WO2011065277A1 - Diffractive element and light pickup device - Google Patents

Diffractive element and light pickup device Download PDF

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Publication number
WO2011065277A1
WO2011065277A1 PCT/JP2010/070553 JP2010070553W WO2011065277A1 WO 2011065277 A1 WO2011065277 A1 WO 2011065277A1 JP 2010070553 W JP2010070553 W JP 2010070553W WO 2011065277 A1 WO2011065277 A1 WO 2011065277A1
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WIPO (PCT)
Prior art keywords
light
diffraction
optical
pickup device
light beam
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PCT/JP2010/070553
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French (fr)
Japanese (ja)
Inventor
徹 木村
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コニカミノルタオプト株式会社
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Priority to JP2011543221A priority Critical patent/JPWO2011065277A1/en
Publication of WO2011065277A1 publication Critical patent/WO2011065277A1/en

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/13—Optical detectors therefor
    • G11B7/131—Arrangement of detectors in a multiple array
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
    • G11B7/127—Lasers; Multiple laser arrays
    • G11B7/1275—Two or more lasers having different wavelengths
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1353—Diffractive elements, e.g. holograms or gratings
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B2007/0003—Recording, reproducing or erasing systems characterised by the structure or type of the carrier
    • G11B2007/0006—Recording, reproducing or erasing systems characterised by the structure or type of the carrier adapted for scanning different types of carrier, e.g. CD & DVD

Definitions

  • the present invention relates to a diffraction element and an optical pickup device suitable for use in an optical pickup device capable of recording and / or reproducing (recording / reproducing) information interchangeably for different types of optical discs.
  • the value as a product of an optical disc player / recorder cannot be said to be sufficient simply by saying that information can be appropriately recorded / reproduced on such a high-density optical disc.
  • DVDs and CDs compact discs
  • making it possible to appropriately record / reproduce information on DVDs and CDs leads to an increase in commercial value as an optical disc player / recorder for high-density optical discs.
  • an optical pickup device mounted on an optical disc player / recorder for high density optical discs can appropriately receive information while maintaining compatibility with both high density optical discs, DVDs, and even CDs. It is desired to have a performance capable of recording / reproducing.
  • optical systems for high-density optical discs and optical systems for DVDs and CDs are used.
  • a method of selectively switching between systems depending on an optical disk on which information is recorded / reproduced is conceivable, but a plurality of optical systems are required, which is disadvantageous for miniaturization and increases costs.
  • the optical system for high-density optical discs and the optical system for DVDs and CDs must be shared in compatible optical pickup devices. It is preferable to reduce the number of optical components constituting the optical pickup device as much as possible. In addition, it is most advantageous for miniaturization and cost reduction of the configuration of the optical pickup device to make the objective optical element arranged facing the optical disc as common as possible.
  • Patent Documents 1 and 2 disclose a high-density optical disk using a light source and a common photodetector that house a semiconductor laser capable of emitting light beams of three different wavelengths in one package in order to reduce the size and cost. And an optical pickup device for recording and / or reproducing information so as to be compatible with conventional DVDs and CDs.
  • Patent Document 3 discloses a light source in which three semiconductor lasers are housed in one package.
  • Patent Document 4 discloses a semiconductor laser device including a plurality of semiconductor laser elements.
  • Patent Document 5 discloses that 0th order diffracted light is generated when a light beam having a wavelength ⁇ 1 is incident, Mth order diffracted light is generated when a light beam having a wavelength ⁇ 2 is incident, and Nth order diffracted light is incident when a light beam having a wavelength ⁇ 3 is incident.
  • a diffractive element that generates the above is disclosed.
  • each light emitting unit is shifted in the direction perpendicular to the optical axis. It is necessary to shift each light flux.
  • the light flux is shifted using a diffraction groove, but it is assumed that the interval between the light emitting points is accurately adjusted to a predetermined value.
  • Patent Document 3 a so-called blue-violet semiconductor laser that emits a light beam of about 405 nm is formed on a GaN substrate.
  • An infrared semiconductor laser is formed on a GaAs substrate.
  • the emission point interval can be maintained with high accuracy relatively easily.
  • semiconductor lasers it is inevitable that the intervals between the light emitting points vary when assembled in the same package (see paragraphs [0010], [0011], and [0012] of Patent Document 4). ).
  • a diffractive element that generates next-order diffracted light is disclosed, but by using such a diffractive element, there is a collection caused by variation in the distance between the light emitting point of the light beam having the wavelength ⁇ 1 and the light emitting point of the light beam having the wavelengths ⁇ 2 and ⁇ 3.
  • Patent Document 5 does not disclose or suggest the idea of correcting the deviation of the optical position.
  • the present invention takes the above-described problems into consideration, and provides a diffraction element for use in an optical pickup device capable of appropriately recording / reproducing information with respect to three different types of optical disks while reducing the size and reducing the cost.
  • the purpose is to do.
  • the diffractive element according to claim 1 includes a first light emitting unit that emits a first light beam having a wavelength ⁇ 1, a second light emitting unit that emits a second light beam having a wavelength ⁇ 2 ( ⁇ 1 ⁇ 2), and a wavelength ⁇ 3 ( ⁇ 2 ⁇ ⁇ 3) a third light source that emits a third light beam, an objective optical system, a single photodetector, and a light path between the light source and the photodetector so as to be movable
  • a diffraction element that is disposed and through which the first light beam, the second light beam, and the third light beam pass in common, and the light beam from the first light emitting unit is transmitted to the information on the first optical disk by the objective optical system.
  • a spot is formed by condensing on the recording surface, and information is recorded and / or reproduced on the first optical disk based on a signal from the photodetector that has received the reflected light, and the first 2
  • the light flux from the light emitting section is condensed on the information recording surface of the second optical disk by the objective optical system.
  • a spot is formed and information is recorded and / or reproduced on the second optical disc based on a signal from the photodetector that receives the reflected light, and a light beam from the third light emitting unit. Is focused on the information recording surface of the third optical disk by the objective optical system, and a spot is formed.
  • the spot is formed on the third optical disk.
  • a diffraction element used in an optical pickup device for recording and / or reproducing information In the light source, the second light emitting unit and the third light emitting unit are formed on the same chip, and the first light emitting unit is formed on a chip different from the second light emitting unit and the third light emitting unit.
  • the diffractive element has a diffraction groove that transmits the first light flux and diffracts the second light flux and the third light flux.
  • the first light beam, the second light beam, and the third light beam are drawn while being shifted in the vertical direction for easy understanding, but they may overlap in the direction perpendicular to the paper surface.
  • the diffracted light emitted from the diffraction element is zero-order diffracted light and passes (transmits).
  • the diffracted light emitted from the diffraction element is m-order (m ⁇ 0) diffracted light, so that the diffraction angle ⁇ 2 is given, and the light beam has a different direction from the light beam having the wavelength ⁇ 1. It will be emitted.
  • the diffracted light emitted from the diffraction element is an nth order (n ⁇ 0) diffracted light, so that a diffraction angle ⁇ 3 is given, and the light is emitted in a direction different from the light beam having the wavelength ⁇ 1. Will be.
  • the distance between the first light emitting unit and the second light emitting unit and the first light emitting unit and the third light emitting unit deviated from the design value.
  • the photodetector is shifted up and down in FIG. 1 so that the light receiving position P1 of the light beam with wavelength ⁇ 1 is the optimum position, the light receiving position of the light beam with wavelength ⁇ 1 on the light receiving surface of the light detector.
  • P1 is appropriate, the light receiving positions P2 and P3 of the light beam having the wavelength ⁇ 2 and the light beam having the wavelength ⁇ 3 are shifted from appropriate positions with respect to the light receiving surface position.
  • the light beam having the wavelength ⁇ 1 passes through, so that the light receiving position P1 of the photodetector is unchanged, whereas the light beam having the wavelength ⁇ 2 and the wavelength ⁇ 3 With respect to the luminous flux, the light receiving position changes from P2, P3 to P2 ′, P3 ′, respectively, according to the relative distance between the diffraction element and the photodetector.
  • the light receiving position of the light beams having the wavelengths ⁇ 2 and ⁇ 3 can be changed independently of the light beam having the wavelength ⁇ 1, and an appropriate position can be obtained.
  • any light beam is detected. Can be incident on an appropriate position on the light receiving surface of the detector.
  • the position of the diffraction element in the optical axis direction may be adjusted during assembly of the optical pickup device and fixed after assembly, or the diffraction element may be movable in the optical axis direction so that it can be adjusted in a timely manner.
  • ⁇ 2 ⁇ 3.
  • the diffraction element according to claim 2 is characterized in that, in the invention according to claim 1, the diffraction groove has a one-dimensional structure.
  • the diffraction element according to claim 3 is the invention according to claim 1 or 2, wherein the diffraction groove includes three or more step surfaces extending substantially parallel to the optical axis of the optical system of the optical pickup device. And a step unit formed by sequentially shifting the adjacent terrace surfaces in the optical axis direction of the optical pickup device as the optical axis of the optical pickup device.
  • a step periodic structure is formed by arranging a plurality of elements along the intersecting direction.
  • a diffraction element according to a fourth aspect is the invention according to any one of the first to third aspects, wherein the following formulas (1) to (3), 395 (nm) ⁇ ⁇ 1 ⁇ 415 (nm) (1) 630 (nm) ⁇ ⁇ 2 ⁇ 700 (nm) (2) 750 (nm) ⁇ ⁇ 3 ⁇ 850 (nm) (3) It is characterized by satisfying.
  • the diffraction element according to claim 5 is the diffraction element according to any one of claims 1 to 4, wherein the diffraction order of diffracted light generated when the second light flux is incident on the diffraction element;
  • the signs of the diffraction orders of the diffracted light generated when the third light beam is incident are equal to each other.
  • a diffraction element is the invention according to the third aspect, wherein an Abbe number ⁇ d in the d-line of the material of the diffraction element is between 40 and 70, and the second light flux is incident on the diffraction element.
  • the Abbe number ⁇ d at the d-line of the material of the diffractive element is between 20 and 40, and the second light flux is incident on the diffractive element.
  • a diffraction element is the invention according to the sixth or seventh aspect, wherein the following formulas (13) to (15),
  • 0 (13)
  • m (14)
  • n (15)
  • the amount d2 the third step amount d3,..., The jth step amount dj, the phase difference of the i-th wavelength ⁇ i generated by each step amount.
  • ⁇ ij ⁇ ij ⁇ ROUND ( ⁇ i)
  • ⁇ ij dj / ⁇ i ⁇ (ni ⁇ 1)
  • ⁇ ij ⁇ i1 + ⁇ i2 + ... + ⁇ ij-1 + ⁇ ij
  • I-th wavelength ⁇ i ( ⁇ m)
  • Refractive index of diffraction element at i-th wavelength ⁇ i: ni J-th step: dj ( ⁇ m)
  • Integer obtained by rounding the first decimal place of any real number A: ROUND (A) It is characterized by satisfying.
  • a diffraction element is the invention according to any one of the first to seventh aspects, wherein the diffraction grooves are three or more extending substantially parallel to an optical axis of an optical system of the optical pickup device.
  • the first step surface and three or more first terrace surfaces intersecting the first step surface, and the adjacent first terrace surfaces are sequentially shifted in the optical axis direction of the optical pickup device.
  • a first step periodic structure formed by arranging a plurality of first step units along a direction intersecting the optical axis of the optical pickup device, and extends substantially parallel to the optical axis of the optical pickup device.
  • a second step unit having two second step surfaces and two second terrace surfaces intersecting the second step surface, wherein the two second step surfaces overlap in a direction perpendicular to the optical axis; Intersects the optical axis of the device Along the direction of the second step periodic structure formed by arranging a plurality, characterized by comprising superimposed together period each other.
  • the diffraction element according to any one of the first to seventh aspects, wherein the diffraction grooves are five or more extending substantially parallel to the optical axis of the optical system of the optical pickup device.
  • the first step surface and five or more first terrace surfaces intersecting the first step surface, and the adjacent first terrace surfaces are sequentially shifted in the optical axis direction of the optical pickup device.
  • a first step periodic structure formed by arranging a plurality of first step units along a direction intersecting the optical axis of the optical pickup device, and extends substantially parallel to the optical axis of the optical pickup device.
  • a second step unit having two second step surfaces and two second terrace surfaces intersecting the second step surface, wherein the two second step surfaces overlap in a direction perpendicular to the optical axis; Crosses the optical axis of the device
  • a second step periodic structure formed by arranging a plurality of the stepped portions along a direction, two third step surfaces extending substantially parallel to the optical axis of the optical pickup device, and the third step surface.
  • a plurality of third step units having two third terrace surfaces and overlapping the two third step surfaces in the direction perpendicular to the optical axis are arranged along a direction intersecting the optical axis of the optical pickup device.
  • the third step periodic structure formed by the above is overlapped with the same period.
  • the diffraction element according to claim 11 is characterized in that, in the invention according to any one of claims 1 to 10, the following expression is satisfied.
  • a diffractive element according to a twelfth aspect is characterized in that, in the invention according to any one of the first to eleventh aspects, the diffraction groove is formed on a parallel plate.
  • An optical pickup device includes the diffraction element according to any one of the first to twelfth aspects.
  • An optical pickup device is the optical pickup device according to the thirteenth aspect, wherein the diffraction order of the diffracted light generated when the second light flux is incident on the diffraction element is m, and the diffraction order is the first.
  • N is the diffraction order of the diffracted light generated when three light beams are incident
  • A is the distance in the direction perpendicular to the optical axis between the first light emitting part and the second light emitting part, and the first light emitting part and the third light emitting part.
  • the diffraction angle of the diffracted light generated in the diffraction groove is determined by the product of the wavelength and the diffraction order.
  • A the distance between the first light emitting part LD1 and the second light emitting part LD2 in the direction perpendicular to the optical axis
  • B the distance between the first light emitting part LD1 and the third light emitting part LD3 in the direction perpendicular to the optical axis
  • the diffraction order of the diffracted light generated when the second light beam ⁇ 2 is incident on the element DE is m
  • the diffraction order of the diffracted light generated when the third light beam ⁇ 3 is incident on the diffractive element DE is n
  • optical axis of the optical system of the optical pickup device may be abbreviated as “optical axis”.
  • the light source of the optical pickup device has at least three light emitting units, a first light emitting unit, a second light emitting unit, and a third light emitting unit. Furthermore, the optical pickup device of the present invention condenses the first light flux on the information recording surface of the first optical disc, condenses the second light flux on the information recording surface of the second optical disc, and causes the third light flux to be third. It has a condensing optical system for condensing on the information recording surface of the optical disc.
  • the optical pickup device of the present invention includes a light receiving element that receives a reflected light beam from the information recording surface of the first optical disc, the second optical disc, or the third optical disc.
  • the first optical disc has a protective substrate having a thickness t1 and an information recording surface.
  • the second optical disc has a protective substrate having a thickness t2 (t1 ⁇ t2) and an information recording surface.
  • the third optical disc has a protective substrate having a thickness t3 (t2 ⁇ t3) and an information recording surface.
  • the first optical disc is preferably a BD
  • the second optical disc is a DVD
  • the third optical disc is preferably a CD, but is not limited thereto.
  • the first optical disc, the second optical disc, or the third optical disc may be a multi-layer optical disc having a plurality of information recording surfaces.
  • BD means that information is recorded / reproduced by a light beam having a wavelength of about 390 to 415 nm and an objective lens having an NA of about 0.8 to 0.9, and the thickness of the protective substrate is 0.05 to 0.00 mm.
  • It is a generic term for a BD series optical disc of about 125 mm, and includes a BD having only a single information recording layer, a BD having two or more information recording layers, and the like.
  • DVD is a general term for DVD series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.60 to 0.67 and the thickness of the protective substrate is about 0.6 mm.
  • CD is a general term for CD series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.45 to 0.51 and the thickness of the protective substrate is about 1.2 mm.
  • CD-ROM, CD-Audio, CD-Video, CD-R, CD-RW and the like As for the recording density, the recording density of BD is the highest, followed by the order of DVD and CD.
  • the thickness of the protective substrate is the thickness of the protective substrate provided on the surface of the optical disk. That is, the thickness of the protective substrate from the optical disc surface to the information recording surface closest to the surface.
  • the first light emitting unit, the second light emitting unit, and the third light emitting unit are preferably laser light sources.
  • the laser light source a semiconductor laser, a silicon laser, or the like can be preferably used.
  • the first wavelength ⁇ 1 of the first light beam emitted from the first light emitting unit, the second wavelength ⁇ 2 of the second light beam emitted from the second light emitting unit ( ⁇ 2> ⁇ 1), and the third light beam emitted from the third light emitting unit The third wavelength ⁇ 3 ( ⁇ 3> ⁇ 2) of the following conditional expressions (21), (22), 1.5 ⁇ ⁇ 1 ⁇ 2 ⁇ 1.7 ⁇ ⁇ 1 (21) 1.8 ⁇ ⁇ 1 ⁇ 3 ⁇ 2.0 ⁇ ⁇ 1 (22) It is preferable to satisfy.
  • the first wavelength ⁇ 1 of the first light emitting unit is preferably 350 nm or more and 440 nm or less, more preferably
  • the second wavelength ⁇ 2 of the second light emitting part is preferably 570 nm or more and 730 nm or less, more preferably 630 nm or more and 700 nm or less
  • the third wavelength ⁇ 3 of the third light emitting part is 395 nm or more and 415 nm or less.
  • they are 730 nm or more and 880 nm or less, More preferably, they are 750 nm or more and 850 nm or less.
  • the first light emitting unit, the second light emitting unit, and the third light emitting unit are preferably a single light source that is unitized.
  • the unitization means that the first light emitting unit, the second light emitting unit, and the third light emitting unit are fixedly housed in one package, for example.
  • the first light emitting unit, the second light emitting unit, and the third light emitting unit are arranged at different positions along the direction intersecting the optical axis of the optical pickup device.
  • the light source it is preferable that the second light emitting unit and the third light emitting unit are formed on the same chip, and the first light emitting unit is formed on a different chip.
  • An example of such a light source is disclosed in Japanese Patent Application Laid-Open No. 2004-319915.
  • a photodetector such as a photodiode is preferably used.
  • Light reflected on the information recording surface of the optical disc enters the light receiving element, and a read signal of information recorded on each optical disc is obtained using the output signal. Furthermore, it detects the change in the light amount due to the spot shape change and position change on the light receiving element, performs focus detection and track detection, and based on this detection, the objective lens can be moved for focusing and tracking I can do it.
  • the light receiving element may comprise a plurality of photodetectors.
  • the light receiving element may have a main photodetector and a sub photodetector.
  • two sub photodetectors are provided on both sides of a photodetector that receives main light used for recording and reproducing information, and the sub light for tracking adjustment is received by the two sub photodetectors. It is good also as a simple light receiving element.
  • the light receiving element a plurality (at least three or more) of light receiving portions corresponding to the first, second, and third light emitting portions are arranged differently in the direction perpendicular to the optical axis of the optical pickup device.
  • the condensing optical system has an objective lens.
  • the condensing optical system preferably includes a coupling lens such as a collimator (sometimes referred to as a collimating lens) in addition to the objective lens.
  • the coupling lens is a single lens or a lens group that is disposed between the objective lens and the light source and changes the divergence angle of the light beam.
  • the collimator is a type of coupling lens, and is a lens that emits light incident on the collimator as parallel light.
  • the objective lens refers to an optical system that is disposed at a position facing the optical disk in the optical pickup device and has a function of condensing the light beam emitted from the light source onto the information recording surface of the optical disk.
  • the objective lens may be composed of two or more lenses and / or optical elements, or may be composed of a single lens, but is preferably an objective lens composed of a single convex lens.
  • the objective lens may be a glass lens or a plastic lens, or an optical path difference providing structure is provided on the glass lens with a photocurable resin, an ultraviolet curable resin, or a thermosetting resin.
  • a hybrid lens may also be used.
  • the objective lens has a plurality of lenses, a glass lens and a plastic lens may be mixed and used.
  • the objective lens includes a plurality of lenses, it may be a combination of a flat optical element having an optical path difference providing structure and an aspherical lens (which may or may not have an optical path difference providing structure).
  • the objective lens preferably has a refractive surface that is aspheric.
  • the base surface on which the optical path difference providing structure is provided is preferably an aspherical surface.
  • the objective lens a single objective lens shared by three wavelengths may be used, or an objective lens shared by two wavelengths and an objective lens dedicated to the remaining wavelengths may be used. Such an objective lens is well known and will not be described.
  • the diffractive element of the present invention can be arranged at any position as long as it is in the optical path between the light source and the light receiving element.
  • the diffraction efficiency of the 0th-order diffracted light when the first light beam is incident, the diffraction efficiency of the 0th-order diffracted light is higher than the diffraction efficiency of any other diffraction order diffracted light, and the second light beam is incident.
  • the diffraction efficiency of the mth order (m ⁇ 0) diffracted light is higher than the diffraction efficiency of any other diffracted order diffracted light, and when the third light beam is incident, the nth order (n ⁇ 0).
  • the diffraction element can be made of glass or plastic and is preferably formed on a parallel plate as shown in FIG. It is preferable that the diffraction orders of the diffracted light generated when the second light beam is incident on the diffractive element are equal to the signs of the diffraction orders of the diffracted light generated when the third light beam is incident. Referring to FIG.
  • the diffracted light of the emitted second light beam and the diffracted light of the third light beam travel in different directions (one is + direction when the 0th-order diffracted light is 0 degree, and the other is-direction). This is because it is difficult to adjust the spot position.
  • the diffractive element may have a hybrid structure in which a plastic layer having diffraction grooves formed on the surface thereof is bonded onto a glass substrate, or materials having different dispersions are bonded to form a diffraction groove on the bonding surface. It is good also as a joined type structure.
  • the diffractive element has a hybrid structure, it is preferable to use a photocurable resin, an ultraviolet curable resin, or a thermosetting resin as the plastic layer.
  • a junction structure it is possible to suppress diffraction of light in different wavelength bands and selectively configure only the second light flux and the third light flux with desired diffraction efficiency.
  • the diffraction groove is made of different materials, and each material has a required refractive index difference between the refractive index of the light beam having the first wavelength ⁇ 1 and the refractive index of the light beam of the second wavelength ⁇ 2 and the third wavelength ⁇ 3.
  • each material has a required refractive index difference between the refractive index of the light beam having the first wavelength ⁇ 1 and the refractive index of the light beam of the second wavelength ⁇ 2 and the third wavelength ⁇ 3.
  • the diffraction groove as used in this specification is a general term for a structure having a step surface extending substantially parallel to the optical axis and having an action of changing the traveling direction of a light beam having a specific wavelength by diffraction.
  • the diffraction grooves are preferably not a concentric circle but a linear one-dimensional grating.
  • the diffraction groove is formed in a straight shape on the substrate in a direction orthogonal to the optical axis, and a light beam having a specific wavelength is incident on each unit shape.
  • the structure includes a structure in which the wavefront of the transmitted light shifts between adjacent annular zones, and as a result, a traveling direction of the light flux is changed by forming a new wavefront.
  • the diffraction groove preferably has a plurality of step surfaces, and the step surfaces may be arranged at periodic intervals in the optical axis orthogonal direction or may be arranged at non-periodic intervals in the optical axis orthogonal direction. Good.
  • the diffraction grooves have various cross-sectional shapes (cross-sectional shapes on the plane including the optical axis), and the cross-sectional shapes including the optical axis are roughly classified into a blazed structure and a staircase structure.
  • the blazed structure is a sawtooth shape in cross section including the optical axis of a diffraction element having a diffraction groove. It has a plurality of step surfaces ST extending along a substantially optical axis direction (vertical direction in the drawing) of the optical pickup device, and a slope CP connecting the adjacent step surfaces.
  • the upper side is the light source side
  • the lower side is the photodetector side
  • a diffraction groove is formed on a parallel plate.
  • the length in the direction perpendicular to the optical axis of one blaze unit is referred to as a pitch P (see FIGS. 4A and 4B).
  • the length in the optical axis direction of the step surface parallel to the optical axis of the blaze is referred to as a step amount B (or sometimes referred to as a blaze height h) (see FIG. 4A).
  • Such a blazed structure tends to have a smaller step than the step structure described later, so that the wavelength dependence and temperature dependence of diffraction efficiency can be reduced. Even a light source deviating from the value can be used, and an optical pickup device having a wide usable environmental temperature range can be provided.
  • the staircase structure is a step-like structure in which the cross-sectional shape including the optical axis of an optical element having a diffraction groove is a step shape (referred to as a step unit). More specifically, it has a plurality of step surfaces ST extending substantially along the optical axis direction of the optical pickup device, and a plurality of terrace surfaces TR intersecting with the step surfaces.
  • the stepped structure shown in FIG. 4C has three or more (five in the drawing) step surfaces ST and three or more (five in the drawing) terrace surfaces TR, and adjacent terrace surfaces TR.
  • the step periodic structure is formed by arranging a plurality of step units, which are sequentially shifted in the optical axis direction of the optical pickup device, along the direction intersecting the optical axis of the optical pickup device (left-right direction in the figure). It will be. That is, in particular, the staircase structure with three or more terrace surfaces TR has a small step surface ST and a large step surface LST. In this specification, when there are three terrace surfaces, it is called a three-step structure, and when there are four terrace surfaces, it is called a four-step structure.
  • the staircase structure refers to diffracted light used for information recording / reproduction and unnecessary-order light (diffracted light having a different order from the order of diffracted light used for information recording / reproduction, compared to the blazed structure described above.
  • the difference between the diffraction angle and the collection spot of diffracted light used for recording / reproducing information and the collection spot of unnecessary order light on the light receiving surface of the photodetector is large. It is possible to obtain good information recording / reproducing characteristics without becoming too small.
  • the diffraction grooves shown in FIG. 4D are configured to connect the terrace surfaces TR sandwiched between the end portions of the adjacent step surfaces ST and ST extending substantially in the optical axis direction.
  • the terrace surfaces TR and TR are parallel to each other and shifted in the optical axis direction.
  • it is called a two-step structure.
  • a structure in which one or more terraces TR are shifted in the direction of lowering by an equal amount from the highest side is also a staircase structure.
  • the length of one staircase unit in the direction perpendicular to the optical axis is referred to as a pitch P (see FIGS. 4C and 4D).
  • the lengths of the steps LST and ST along the optical axis direction are referred to as step amounts B1 and B2.
  • B1 B2.
  • the diffraction groove preferably has a structure in which a certain unit shape is periodically repeated.
  • unit shape is periodically repeated naturally includes shapes in which the same shape is repeated in the same cycle.
  • the unit shape that is one unit of the cycle has regularity, and the shape in which the cycle gradually increases or decreases gradually is also included in the “unit shape is periodically repeated”.
  • the width of the terrace surface formed in one staircase unit may be uniform or non-uniform in one staircase unit. If the width of the terrace surface is not uniform within one step unit, the intensity of the diffracted light of a specific order can be increased or decreased, so that it does not affect the information recording / reproduction characteristics. In addition, it is possible to adjust the intensity of unnecessary-order light (which indicates a diffracted light having a different order from that of the diffracted light used for recording / reproducing information) on the light receiving surface of the photodetector.
  • the width of the terrace surface formed in one staircase unit non-uniform it is preferable to make the width of the terrace surface that becomes a recess in the mold wider than the other terrace surfaces.
  • the concave portion in the mold here refers to a terrace surface in which adjacent step surfaces are negative on both sides.
  • the sawtooth shape as a unit shape is repeated. As shown in FIG. 4 (a), the same sawtooth shape may be repeated.
  • the diffraction groove has a stepped structure
  • the terrace surface TR is inclined with respect to the optical axis.
  • the step amount B has an intersection angle of 180 degrees on the side in contact with air.
  • the distance in the optical axis direction between the intersections of the step surface ST and the terrace surface TR is as described above.
  • a minute step is formed in the back of the terrace surface TR.
  • the step amount B is the intersection angle on the side in contact with the air. Is the distance in the optical axis direction between the intersections of the step surface ST and the terrace surface TR that is 180 degrees or more. Note that the length of the step surface ST in the optical axis direction may be changed slightly. Further, the diffraction groove may be provided on the light source side of the parallel plate, or may be provided on the photodetector side.
  • a light beam is incident from below on a diffractive element arranged such that a slope CP connecting adjacent step surfaces increases from left to right.
  • diffracted light that is diffracted in the right direction is a positive diffraction order
  • diffracted light that is diffracted in the left direction is a negative diffraction order.
  • the staircase structure is a structure in which one or two or more terraces TR are shifted from the highest side in the direction of decreasing by an equal amount as shown in FIG. 4E, the terraces TR are shifted.
  • the diffractive element arranged so that the terrace surface TR sequentially increases from left to right within one step unit of the previous basic structure (pointing to the structure indicated by the dotted line in FIG. 4E) from below.
  • a diffracted light that is diffracted in the right direction when the light beam is incident is a positive diffraction order
  • a diffracted light that is diffracted in the left direction is a negative diffraction order.
  • the optical information recording / reproducing apparatus has an optical disc drive apparatus having an optical pickup device provided with the above-described diffraction element.
  • the optical disk drive apparatus can hold an optical disk mounted from the optical information recording / reproducing apparatus main body containing the optical pickup apparatus or the like. There are a system in which only the tray is taken out, and a system in which the optical disc drive apparatus main body in which the optical pickup device is stored is taken out to the outside.
  • the optical information recording / reproducing apparatus using each method described above is generally equipped with the following components, but is not limited thereto.
  • An optical pickup device housed in a housing or the like, a drive source of an optical pickup device such as a seek motor that moves the optical pickup device together with the housing toward the inner periphery or outer periphery of the optical disc, and the optical pickup device housing the inner periphery or outer periphery of the optical disc include a transfer means of an optical pickup device having a guide rail or the like that guides toward the head, a spindle motor that rotates the optical disk, and the like.
  • the former method is provided with a tray that can be held in a state in which an optical disk is mounted and a loading mechanism for sliding the tray, and the latter method has no tray and loading mechanism. It is preferable that each component is provided in a drawer corresponding to a chassis that can be pulled out to the outside.
  • a diffractive element used for an optical pickup device capable of appropriately recording / reproducing information on three different types of optical discs while reducing the size and reducing the cost.
  • FIG. 1 It is a figure which shows the principle of this invention. It is a figure for demonstrating the relationship between the space
  • FIG. 6 It is the figure which looked at the light-receiving surface of photodetector PD shown in FIG. 6 in the arrow VII direction. It is the schematic which shows the relationship between the position of the diffraction element DE, and the light-receiving position of each light beam in photodetector PD. It is the schematic of the optical pick-up apparatus which has arrange
  • 3 is a cross-sectional view of the diffraction element of Example 1.
  • FIG. 6 is a diagram showing the wavelength characteristics of the diffraction element of Example 3.
  • FIG. 6 is a diagram showing the wavelength characteristics of the diffraction element of Example 4.
  • 6 is a sectional view of a diffraction element according to Example 6.
  • FIG. It is sectional drawing of the diffraction element of Example 16, and shows the shifted staircase type diffraction structure which can be formed by superimposition.
  • FIG. 10 is a graph showing the wavelength characteristics of the diffraction element of Example 16. It is sectional drawing of the diffraction element of Example 17, and shows the shifted staircase type diffraction structure which can be formed by superimposition.
  • FIG. 14 is a graph showing the wavelength characteristics of the diffraction element of Example 17.
  • FIG. 6 is a diagram schematically showing the configuration of the optical pickup device PU1 of the present embodiment that can appropriately record and / or reproduce information on BD, DVD, and CD, which are different optical disks.
  • Such an optical pickup device PU1 can be mounted on an optical information recording / reproducing device.
  • FIG. 7 is a view of the light receiving surface of the photodetector PD shown in FIG. 6 as viewed in the direction of the arrow VII, and the condensing spot is indicated by hatching.
  • the first optical disc is a BD
  • the second optical disc is a DVD
  • the third optical disc is a CD.
  • the present invention is not limited to the present embodiment.
  • the optical pickup device PU1 records / reproduces information to / from a single objective lens OBJ as an objective optical system, a ⁇ / 4 wavelength plate QWP, a collimating lens COL, and a polarization beam splitter PBS and BD as light beam separation elements.
  • a light source unit LDP in which a third semiconductor laser LD3 (third light emitting portion) emitting a light beam) is integrated in a single package; That grating GRT, sensor lens SN, the diffraction element DE having diffraction grooves have a photodetector PD, and the like.
  • the second semiconductor laser LD2 and the third semiconductor laser LD3 are formed on the same chip, and the first semiconductor laser LD1 is formed on a different chip.
  • the diffractive element DE shaped as shown in FIG. 3 generates 0th-order diffracted light as the diffracted light with the highest light amount when the first light beam enters, and as the diffracted light with the highest light amount when the second light beam enters.
  • a diffraction groove that generates first-order diffracted light and generates first-order diffracted light as the diffracted light having the highest light amount when the third light beam enters is formed on the surface.
  • the diffraction element DE is held by a guide (not shown) so as to be movable in the optical axis direction.
  • the photodetector PD has light receiving portions 11R to 33R arranged in 3 rows and 3 columns on the light receiving surface side substantially orthogonal to the optical axis.
  • the light receiving portions 11R to 13R are first light receiving portions that receive the reflected light from the BD
  • the light receiving portions 21R to 23R are second light receiving portions that receive the reflected light from the DVD
  • the light receiving portions 31R to 33R are from the CD. It is the 3rd light-receiving part which receives the reflected light.
  • the light receiving unit 12R is divided into four parts vertically and horizontally, and signals based on the amount of received light are 1e, 1c, 1f, and 1d, respectively.
  • the light receiving parts 11R and 13R on both sides of the light receiving part 12R are divided into left and right parts, and signals based on the amount of light received are 1h, 1g, and 1b and 1a, respectively.
  • the light receiving unit 22R is divided into four parts in the vertical and horizontal directions, and signals based on the amount of received light are 2e, 2c, 2f, and 2d, respectively.
  • the light receiving parts 21R and 23R on both sides of the light receiving part 22R are divided into left and right parts, and signals based on the amount of light received are 2h, 2g, 2b and 2a, respectively.
  • the light receiving unit 32R is divided into four parts, top, bottom, left, and right, and signals based on the amount of light received are 3e, 3c, 3f, and 3d, respectively.
  • the light receiving parts 31R and 33R on both sides of the light receiving part 32R are divided into left and right parts, and the signals based on the amount of received light are 3h, 3g, and 3b and 3a, respectively.
  • the collimated light passes through the COL, is converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, the diameter of the light flux is regulated by a diaphragm (not shown), and the light flux condensed by the objective lens OBJ is thick.
  • the spot is formed on the information recording surface of the BD through a protective substrate having a thickness of 0.1 mm.
  • the reflected light beam modulated by the information pits on the information recording surface of the BD again passes through the objective lens OBJ and a diaphragm (not shown), and then converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wavelength plate QWP, and collimated lens COL.
  • the light beam is converged and passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams converge on the light receiving portions 11R to 13R of the photodetector PD, respectively.
  • the information recorded on the BD can be read by using the output signal of the photodetector PD to focus or track the objective lens OBJ by an objective lens actuator (not shown).
  • a focus error (FE) signal, a tracking error (TE) signal, and a recording mark reproduction signal (RF) in a state where the focus servo is applied to the BD are observed.
  • the astigmatism method is used for the focus servo, and the FE signal is obtained by (1c + 1f) ⁇ (1e + 1d), and the objective lens OBJ is focused by the objective lens actuator so that the FE signal approaches zero.
  • the tracking servo uses the DPP method.
  • the TE signal is obtained by (1a + 1g + 1e + 1f) ⁇ (1b + 1h + 1c + 1d), and the objective lens OBJ is tracked by the objective lens actuator so that this approaches zero.
  • the RF signal is the sum of the amounts of received light, and is represented by (1a + 1b + 1c + 1d + 1e + 1f + 1g + 1h).
  • the reflected light beam modulated by the information pits on the information recording surface of the DVD is again transmitted through the objective lens OBJ and a diaphragm (not shown), and then converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wavelength plate QWP, and collimated lens COL.
  • the light beam is converged and passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams are converged on the light receiving portions 21R to 23R of the photodetector PD, respectively.
  • the objective lens OBJ is focused and tracked by an unillustrated objective lens actuator, whereby the information recorded on the DVD can be read.
  • a focus error (FE) signal, a tracking error (TE) signal, and a recording mark reproduction signal (RF) in a state where the focus servo is applied to the DVD are observed.
  • the astigmatism method is used for the focus servo, and the FE signal is obtained by (2c + 2f) ⁇ (2e + 2d), and the objective lens OBJ is focused by the objective lens actuator so that this becomes close to zero.
  • the tracking servo uses the DPP method.
  • the TE signal is obtained by (2a + 2g + 2e + 2f) ⁇ (2b + 2h + 2c + 2d), and the objective lens OBJ is tracked by the objective lens actuator so that the TE signal approaches zero.
  • the RF signal is the sum of the amounts of received light, and is represented by (2a + 2b + 2c + 2d + 2e + 2f + 2g + 2h).
  • the light beam passes through the collimating lens COL, becomes parallel light, is converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, the diameter of the light beam is regulated by a diaphragm (not shown), and the light beam collected by the objective lens OBJ.
  • the reflected light beam modulated by the information pits on the information recording surface of the CD is again transmitted through the objective lens OBJ and a diaphragm (not shown), and then converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wavelength plate QWP, and collimated lens COL.
  • the light beam is converged and passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams are converged on the light receiving portions 31R to 33R of the photodetector PD, respectively.
  • the objective lens OBJ is focused or tracked by an unillustrated objective lens actuator, whereby the information recorded on the CD can be read.
  • a focus error (FE) signal, a tracking error (TE) signal, and a recording mark reproduction signal (RF) in a state where the focus servo is applied to the CD are observed.
  • the astigmatism method is used for the focus servo, and the FE signal is obtained by (3c + 3f) ⁇ (3e + 3d), and the objective lens OBJ is focused by the objective lens actuator so that this becomes close to zero.
  • the tracking servo uses the DPP method.
  • the TE signal is obtained by (3a + 3g + 3e + 3f) ⁇ (3b + 3h + 3c + 3d), and the objective lens OBJ is tracked by the objective lens actuator so that the TE signal approaches zero.
  • the RF signal is the sum of the amounts of received light, and is represented by (3a + 3b + 3c + 3d + 3e + 3f + 3g + 3h).
  • the second semiconductor laser LD2 and the third semiconductor laser LD3 are formed on the same chip, and the first semiconductor laser LD1 is formed on a different chip. Therefore, when assembled to the light source unit LDP, There is a variation in the distance between the first semiconductor laser LD1, the second semiconductor laser LD2, and the third semiconductor laser LD3.
  • the relative positions of the light receiving portions 11R to 33R of the photodetector PD cannot be shifted. Therefore, when the interval between the semiconductor lasers exceeds the allowable error, it becomes impossible to appropriately receive the light beams by the light receiving portions 11R to 33R. Therefore, in the present embodiment, such a problem is solved as follows.
  • FIG. 8 is a schematic diagram showing the relationship between the position of the diffraction element DE and the light receiving position of each light beam in the photodetector PD.
  • each light beam is shown by a line.
  • the light receiving part is shown only at the center (12R to 32R).
  • the distance between the first semiconductor laser and the second semiconductor laser and the distance between the first semiconductor laser and the third semiconductor laser are larger than the reference value and pass through the diffraction element DE.
  • the optical system When the optical system is set so that one-beam zero-order diffracted light (spot ⁇ 1 indicated by a hatched circle) is positioned at the center of the light receiving portion 12R, the first-order diffracted light (spots indicated by the hatched circle) of the second and third light beams. ( ⁇ 2, ⁇ 3) may be condensed below the light receiving portions 22R and 32R, and an inappropriate signal may be output.
  • the diffractive element DE when the diffraction element DE is moved so as to approach the photodetector PD, the optical path of the 0th-order diffracted light of the first light beam that has passed through the diffraction element DE does not change.
  • the first-order diffracted lights of the second light beam and the third light beam come closer to the centers of the light receiving portions 22R and 32R, respectively. That is, by moving the diffractive element DE relative to the photodetector PD, all the light beams can be appropriately condensed on the light receiving part.
  • the diffractive element DE may be moved away from the photodetector PD.
  • FIG. 9 is a schematic view of an optical pickup device in which the diffractive element DE is disposed between the light source unit LDP and the objective lens OBJ as another position, but some elements are omitted so that it can be easily understood. Each light beam is indicated by a line. Even in this modification, when the diffraction element DE is moved in the optical axis direction, the condensing position of the 0th-order diffracted light of the first light beam that has passed through the diffraction element DE on the light receiving surface of the photodetector PD is not changed.
  • the condensing position of the first-order diffracted light of the second light flux and the third light flux changes, it is possible to collect all the diffracted light at an appropriate position by adjusting the position of the diffractive element DE in the optical axis direction. it can.
  • FIG. 10 is a diagram schematically showing a configuration of the optical pickup device PU2 of the present embodiment capable of appropriately recording and / or reproducing information on BD, DVD, and CD which are different optical disks.
  • Such an optical pickup device PU2 can be mounted on an optical information recording / reproducing device.
  • the first optical disc is a BD
  • the second optical disc is a DVD
  • the third optical disc is a CD.
  • the common components will be denoted by the same reference numerals and description thereof will be omitted.
  • the optical pickup device PU2 of the present embodiment includes a first objective lens OBJ1 and a second objective lens OBJ2 as objective optical systems.
  • the first objective lens OBJ1 and the second objective lens OBJ2 are held by a holder HD, and either one can be inserted into the optical path of the optical pickup device by an actuator (not shown).
  • the first objective lens OBJ1 is designed exclusively for the first light beam
  • the second objective lens OBJ2 is designed to share the second light beam and the third light beam.
  • the operation of the optical pickup device PU2 will be described.
  • the first objective lens OBJ1 is inserted into the optical path of the optical pickup device.
  • the collimated light passes through the COL, is converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, the diameter of the light flux is regulated by a stop (not shown), and the light flux collected by the first objective lens OBJ1 is The spots are formed on the information recording surface of the BD through a protective substrate having a thickness of 0.1 mm.
  • the reflected light beam modulated by the information pits on the information recording surface of the BD again passes through the first objective lens OBJ1 and a diaphragm (not shown), and then converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wavelength plate QWP, and collimated.
  • a converged light beam is formed by the lens COL, passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams converge on the light receiving portions 11R to 13R of the photodetector PD, respectively.
  • the information recorded on the BD can be read by using the output signal of the photodetector PD to focus or track the first objective lens OBJ1 by an objective lens actuator (not shown).
  • the second objective lens OBJ2 is inserted into the optical path of the optical pickup device.
  • a light beam that passes through the lens COL and becomes parallel light, is converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, the diameter of the light beam is regulated by a diaphragm (not shown), and is collected by the second objective lens OBJ2.
  • the reflected light beam modulated by the information pits on the information recording surface of the DVD is again transmitted through the second objective lens OBJ2 and the stop (not shown), and then converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wavelength plate QWP, and collimated.
  • the light beam converged by the lens COL passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams converge on the light receiving portions 21R to 23R of the photodetector PD, respectively. Then, by using the output signal of the photodetector PD to focus or track the second objective lens OBJ2 by an objective lens actuator (not shown), information recorded on the DVD can be read.
  • the second objective lens OBJ2 is inserted into the optical path of the optical pickup device.
  • the collimated light passes through the COL, is converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, the diameter of the light flux is regulated by a diaphragm (not shown), and the light flux collected by the second objective lens OBJ2 is The spots are formed on the information recording surface of the CD through a protective substrate having a thickness of 1.2 mm.
  • the reflected light beam modulated by the information pits on the information recording surface of the CD is again transmitted through the second objective lens OBJ2 and the stop (not shown), and then converted from circularly polarized light to linearly polarized light by the ⁇ / 4 wavelength plate QWP.
  • a converged light beam is formed by the lens COL, passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams converge on the light receiving portions 31R to 33R of the photodetector PD, respectively.
  • the information recorded on the CD can be read by using the output signal of the photodetector PD to focus or track the second objective lens OBJ2 by an objective lens actuator (not shown).
  • the first objective lens OBJ1 when the first objective lens OBJ1 is designed exclusively for the first light flux and the second objective lens OBJ2 is designed to share the second light flux and the third light flux, the diffraction efficiency in the diffraction element DE decreases for the third light flux. Even in such a case, the minimum amount of light received by the photodetector PD can be ensured.
  • the first objective lens OBJ1 may be designed to share the first light flux and the second light flux
  • the second objective lens OBJ2 may be designed exclusively for the third light flux.
  • the diffraction element DE is arranged in the optical path between the polarization beam splitter PBS and the photodetector PD.
  • the light source unit LDP and the polarization beam are arranged. You may arrange
  • the diffraction element DE may be integrated with another optical element. For example, the number of parts can be reduced by forming a diffraction groove on any optical surface of the sensor lens SN or forming a diffraction groove on any optical surface of the grating GRT.
  • the sign of the diffraction order is defined as + when the light beam incident along the horizontal optical axis is directed downward and ⁇ when it is directed upward in the sectional view of the embodiment.
  • the sign of the step amount di is defined as + in the direction toward the right side from the terrace surface adjacent to the upper side and ⁇ as defined in the direction toward the left side from the terrace surface adjacent to the upper side.
  • the sign of the blaze height h is defined as + for the direction toward the right side from the slope adjacent to the upper side, and ⁇ for the direction toward the left side from the slope adjacent to the upper side.
  • the reference numerals described after the numerical values of the step amount di and the blaze height h represent the step amount di and the sign of the blaze height h as described above.
  • Example 1 is a diffractive element provided with a diffractive groove formed by periodically repeating a three-step staircase structure with three terrace surfaces as one step unit, and its shape data is shown in Table 1.
  • FIG. 11 is a cross-sectional view in the optical axis direction of the diffraction element according to the first embodiment.
  • the Abbe number of the material is 56
  • the step amount of the first and second step surfaces is 0.831 ⁇ m
  • the step amount of the third step surface is ⁇ 1.663 ⁇ m. It is.
  • the wavefront of the light beam that has passed through the stepped structure of Example 1 will be described.
  • the wavefronts that have passed through the adjacent terrace surfaces shifted along the optical axis with a step amount of 0.831 ⁇ m are shifted by + 0.150 ⁇ ⁇ 1 wavelength, respectively, and the jth step in an arbitrary step unit
  • ⁇ 1j 0
  • the light passes through as it is (this light beam is called zero-order diffracted light).
  • the wavefronts that have passed through the adjacent terrace surfaces shifted along the optical axis with a step amount of 0.831 ⁇ m are shifted by ⁇ 0.314 ⁇ ⁇ 2 wavelengths, respectively, and the j-th in any step unit.
  • the second light flux that has passed through the stepped structure The diffraction order is ⁇ 1.
  • Example 1 the diffraction efficiency of the first-order diffracted light of the first light flux is 52.6%, the diffraction efficiency of the -1st-order diffracted light of the second light flux is 67.7%, and the diffraction efficiency of the -1st-order diffracted light of the third light flux is 52.8%.
  • Example 2 is a diffractive element provided with a diffractive groove formed by periodically repeating a three-step staircase structure having three terrace surfaces as one step unit. Table 2 shows the shape data thereof.
  • the Abbe number of the material is 56
  • the step amount of the first and second step surfaces 6.435 ⁇ m
  • the step amount of the third step surface ⁇ 12.870 ⁇ m. It is.
  • the intensity of the + 1st order diffracted light is the highest in the incident light, and its diffraction efficiency is 67.6%. Further, when the third light beam is incident, the intensity of the + 1st order diffracted light is the highest in the emitted light, and the diffraction efficiency is 59. 8%.
  • Example 3 is a diffractive element provided with a diffractive groove formed by periodically repeating a five-step staircase structure with five terrace surfaces as one step unit. Table 3 shows the shape data thereof.
  • the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 81.7%, and when the second light beam is incident, it is emitted.
  • the intensity of the + 1st order diffracted light is the highest, the diffraction efficiency is 70.6%, and when the third light beam is incident, the intensity of the + 2nd order diffracted light is the highest in the emitted light, and the diffraction efficiency is 50 0.7%.
  • the wavelength dependence of the first light flux in the diffraction grating of Example 3 is shown in FIG.
  • Example 4 is a diffractive element provided with a diffractive groove formed by periodically repeating a seven-step staircase structure having seven terrace surfaces as one step unit. Table 4 shows the shape data thereof.
  • the Abbe number of the material is 56
  • the step amount of the first to sixth step surfaces 5.025 ⁇ m
  • the step amount of the seventh step surface ⁇ 30.151 ⁇ m. It is.
  • the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 66.2%
  • the second light beam is incident, the light is emitted.
  • FIG. 13 shows the wavelength dependence of the first light flux in the diffraction grating of Example 4.
  • Example 5 is a diffractive element provided with a diffractive groove formed by periodically repeating a three-step staircase structure having three terrace surfaces as one step unit. Table 5 shows the shape data thereof.
  • the Abbe number of the material is 30, the step amount of the first and second step surfaces is 6.476 ⁇ m, and the step amount of the third step surface is ⁇ 12.951 ⁇ m. It is.
  • the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 93.6%, and when the second light beam is incident, it is emitted.
  • the intensity of the ⁇ 1st order diffracted light is the highest, and its diffraction efficiency is 60.7%. Further, when the third light beam is incident, the intensity of the ⁇ 1st order diffracted light is the highest in the emitted light, and its diffraction efficiency Is 61.7%.
  • Example 6 is a diffractive element provided with a diffractive groove formed by periodically repeating a four-step staircase structure having four terrace surfaces in units of one step. Table 6 shows the shape data thereof.
  • FIG. 14 is a sectional view in the optical axis direction of the diffraction element of Example 6.
  • the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 88.2%, and when the second light beam is incident, it is emitted.
  • the intensity of the + 1st order diffracted light is the highest in the incident light, and its diffraction efficiency is 76.3%.
  • the intensity of the + 1st order diffracted light is the highest in the emitted light, and the diffraction efficiency is 71 .1%.
  • Example 7 is a diffractive element provided with a diffractive groove formed by periodically repeating a four-step staircase structure having four terrace surfaces as one step unit, and the shape data is shown in Table 7.
  • the intensity of the 0th-order diffracted light is the highest in the outgoing light, its diffraction efficiency is 100.0%, and when the second light beam is incident, it is emitted.
  • the intensity of the ⁇ 1st order diffracted light is the highest, and its diffraction efficiency is 80.4%. Further, when the third light beam is incident, the intensity of the ⁇ 1st order diffracted light is the highest in the emitted light, and the diffraction efficiency is increased. Is 81.0%.
  • Example 8 is a diffractive element provided with a diffractive groove formed by periodically repeating a five-step staircase structure with five terrace surfaces as one step unit, and the shape data is shown in Table 8.
  • the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 81.7%, and when the second light beam is incident, it is emitted.
  • the intensity of the ⁇ 2nd order diffracted light is the highest, and its diffraction efficiency is 55.7%. Further, when the third light beam is incident, the intensity of the ⁇ 1st order diffracted light is the highest in the emitted light, and the diffraction efficiency is increased. Is 84.3%.
  • Example 9 is a diffractive element provided with a diffractive groove formed by periodically repeating a five-step staircase structure with five terrace surfaces as one step unit, and the shape data is shown in Table 9.
  • the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 81.7%, and when the second light beam is incident, it is emitted.
  • the intensity of the + 1st order diffracted light is the highest in the incident light, and its diffraction efficiency is 75.6%. Further, when the third light beam is incident, the intensity of the + 1st order diffracted light is the highest in the emitted light, and the diffraction efficiency is 69. .3%.
  • Example 10 is a diffractive element provided with a diffractive groove formed by periodically repeating a five-step staircase structure with five terrace surfaces as one step unit.
  • Table 10 shows the shape data thereof.
  • the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 100.0%, and when the second light beam is incident, it is emitted.
  • the intensity of the ⁇ 1st order diffracted light is the highest, and its diffraction efficiency is 78.2%. Further, when the third light beam is incident, the intensity of the ⁇ 1st order diffracted light is the highest in the emitted light, and its diffraction efficiency Is 73.1%.
  • Example 11 is a diffractive element provided with a diffractive groove formed by periodically repeating a seven-step staircase structure having seven terrace surfaces in units of one step. Table 11 shows the shape data thereof.
  • the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 100.0%, and when the second light beam is incident, it is emitted.
  • the intensity of the + 1st order diffracted light is the highest, and its diffraction efficiency is 68.8%. Further, when the third light beam is incident, the intensity of the + 2nd order diffracted light is the highest in the emitted light, and the diffraction efficiency is 75. 0.0%.
  • Example 12 is a diffractive element provided with a diffractive groove formed by periodically repeating a seven-step staircase structure having seven terrace surfaces as one step unit, and its shape data is shown in Table 12.
  • the intensity of the 0th-order diffracted light is the highest in the outgoing light, its diffraction efficiency is 66.2%, and when the second light beam is incident, it is emitted.
  • the intensity of the ⁇ 2nd order diffracted light is the highest, the diffraction efficiency is 71.5%, and when the third light beam is incident, the intensity of the ⁇ 2nd order diffracted light is the highest in the emitted light, and the diffraction efficiency is increased. Is 73.3%.
  • Example 13 is a diffractive element provided with a diffraction groove that is formed by periodically repeating an eight-step staircase structure having eight terrace surfaces as one step unit, and its shape data is shown in Table 13.
  • the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 57.8%, and when the second light beam is incident, In the incident light, the intensity of the + 1st order diffracted light is the highest, the diffraction efficiency is 76.0%, and when the third light beam is incident, the intensity of the + 2nd order diffracted light is the highest in the emitted light, and the diffraction efficiency is 80 8%.
  • Example 14 is a diffractive element provided with a diffraction groove which is formed by periodically repeating an eight-step staircase structure having eight terrace surfaces in units of one step. Table 14 shows the shape data thereof.
  • the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 100.0%, and when the second light beam is incident, it is emitted.
  • the intensity of the ⁇ 2nd order diffracted light is the highest, and its diffraction efficiency is 78.5%. Further, when the third light beam is incident, the intensity of the ⁇ 2nd order diffracted light is the highest in the emitted light, and its diffraction efficiency Is 80.9%.
  • Example 15 is a diffractive element provided with a diffractive groove formed by periodically repeating a nine-step staircase structure with nine terrace surfaces as one step unit. Table 15 shows the shape data thereof.
  • the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 100.0%, and when the second light beam is incident, it is emitted.
  • the intensity of the ⁇ 2nd order diffracted light is the highest, and its diffraction efficiency is 79.6%. Further, when the third light beam is incident, the intensity of the ⁇ 2nd order diffracted light is the highest in the emitted light, and the diffraction efficiency is increased. Is 71.6%.
  • the Abbe number of the material is 56
  • the step amount of the first step surface is 5.025 ⁇ m
  • the step amount of the second step surface is 5.025 ⁇ m
  • the step amount of the fourth step surface 5.025 ⁇ m
  • the step amount of the fifth step surface ⁇ 5.640 ⁇ m.
  • the staircase structure of Example 16 has five first step surfaces in which the diffractive structure extends substantially parallel to the optical axis of the optical pickup device (left-right direction in FIG. 15) as shown in FIG.
  • a first step unit having ST1 and five first terrace surfaces TR1 intersecting with the first step surface ST1 and sequentially shifting adjacent first terrace surfaces TR1 in the optical axis direction of the optical pickup device
  • a first step periodic structure CS1 (5-step structure) formed by arranging a plurality of elements along the direction intersecting the optical axis of the optical pickup device, and the optical axis of the optical pickup device as shown in FIG.
  • two second step surfaces ST2 that intersect the second step surface ST2, and the two second step surfaces ST2 overlap in the direction perpendicular to the optical axis.
  • a second step periodic structure CS2 (two-step structure) formed by arranging a plurality of step units along a direction intersecting the optical axis of the optical pickup device is overlapped with the same period. 15 (c)) and the following expressions (13) to (15) are satisfied.
  • the stepped structure of the sixteenth embodiment is positive in the direction perpendicular to the optical axis in which the step surface ST is directed to the right side from the terrace surface TR adjacent to the upper side in FIG. 15C and upward in FIG.
  • the step surface ST is arranged in the order of positive, positive, negative, positive, negative from the top in one step unit when the direction toward the left side from the terrace surface TR adjacent to the negative is negative.
  • the absolute value of the length in the optical axis direction of the step surface ST and the negative step surface ST is different.
  • it is arbitrary to provide a slope or a minute step as shown in FIG. 5 in this structure.
  • the first step periodic structure has three or more first step surfaces.
  • FIG. 16 is a diagram showing the wavelength dependence of diffraction efficiency in the diffraction element of Example 16. As shown in FIG. 16, even when a wavelength change of ⁇ 5 nm occurs in the semiconductor laser centering on 405 nm, the reduction in diffraction efficiency is about 20%. As can be seen from the comparison with FIG. Improvements are being made. However, in Example 16, the diffraction efficiency of the 0th-order diffracted light of the first light flux is 81.7% and the diffraction efficiency of the + 1st-order diffracted light of the second light flux is 79.5%, whereas the +1 next time of the third light flux. The diffraction efficiency of folding light is as low as 36.9%, and its increase is a problem.
  • the first to sixth steps of the fourth embodiment 5.025 ⁇ m
  • the seventh step is ⁇ 30.151 ⁇ m.
  • FIG. 17D shows a sectional view of the diffractive structure of Example 17.
  • the Abbe number of the material is 56
  • the step amount of the first step surface 5.025 ⁇ m
  • the step amount of the second step surface ⁇ 2.205 ⁇ m
  • 3 Step amount of the fifth step surface 5.025 ⁇ m
  • Step amount of the fourth step surface ⁇ 9.436 ⁇ m
  • Step amount of the fifth step surface 5.025 ⁇ m
  • Sixth step surface Step amount 5.025 ⁇ m
  • step amount of the seventh step surface ⁇ 8.460 ⁇ m.
  • the staircase structure of the seventeenth embodiment has seven first step surfaces in which the diffractive structure extends substantially parallel to the optical axis of the optical pickup device (left-right direction in FIG. 17), as shown in FIG.
  • a first step unit having ST1 and seven first terrace surfaces TR1 intersecting with the first step surface ST1 and sequentially shifting the adjacent first terrace surfaces TR1 in the optical axis direction of the optical pickup device
  • a first step periodic structure CS1 (7 step structure) formed by arranging a plurality of elements along the direction intersecting the optical axis of the optical pickup device, and the optical axis of the optical pickup device as shown in FIG.
  • Second A second step periodic structure CS2 (two step structure) formed by arranging a plurality of step units along a direction intersecting the optical axis of the optical pickup device, and an optical pickup as shown in FIG.
  • a third step periodic structure CS3 (two-step structure) formed by arranging a plurality of third step units overlapping in the orthogonal direction along a direction intersecting the optical axis of the optical pickup device is aligned with each other. (See FIG. 17D) and satisfy the following formulas (13) to (15).
  • the stepped structure of the seventeenth embodiment is positive in the direction perpendicular to the optical axis in the direction perpendicular to the optical axis from the terrace surface TR adjacent to the upper side in FIG. 17 and from the terrace surface TR adjacent to the upper side in FIG.
  • the step surfaces are arranged in order of positive, negative, positive, negative, positive, positive, negative from the top, and the positive step surface and the negative step that face each other.
  • the absolute value of the length of the surface in the optical axis direction is different.
  • the first step periodic structure has five or more first step surfaces.
  • FIG. 18 is a graph showing the wavelength dependence of the diffraction efficiency in the diffraction element of Example 17. As shown in FIG. 18, even when a wavelength change of ⁇ 5 nm occurs in the semiconductor laser centering on 405 nm, the reduction in diffraction efficiency is about 20%. As can be seen from the comparison with FIG. Improvements are being made.
  • Example 17 the diffraction efficiency of the 0th-order diffracted light of the first light flux is 68.9%, the diffraction efficiency of the + 1st-order diffracted light of the second light flux is 87.5%, and the diffraction efficiency of the + 2nd-order diffracted light of the third light flux is 43.8%, which balances the diffraction efficiency of each light beam.
  • the diffraction groove is formed on the optical surface on the side from which the light beam is emitted.
  • the diffraction groove may be formed on the optical surface on the side on which the light beam is incident.

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Abstract

Disclosed is a light pickup device using a light source wherein three semiconductor lasers are contained within one package. A light pickup device uses a diffractive element wherein even if an offset occurs between a light emitting point of a beam of a wavelength λ1 and light emitting points of beams of wavelengths λ2 and λ3, in order to allow each beam to impinge upon a suitable location of a light receiving surface of a light detector, the beam of the wavelength λ1 in an optical path is allowed to pass unmodified, while for the beam of the wavelength λ2 and the beam of the wavelength λ3, a diffraction groove is formed wherein the laser receiving locations shift from P2 and P3 to P2' and P3' according to a relative distance from the light detector.

Description

回折素子及び光ピックアップ装置Diffraction element and optical pickup device
　本発明は、異なる種類の光ディスクに対して互換可能に情報の記録及び／又は再生（記録／再生）を行える光ピックアップ装置に用いると好適な回折素子及び光ピックアップ装置に関する。 The present invention relates to a diffraction element and an optical pickup device suitable for use in an optical pickup device capable of recording and / or reproducing (recording / reproducing) information interchangeably for different types of optical discs.
　近年、波長４００ｎｍ程度の青紫色半導体レーザを用いて、情報の記録及び／又は再生（以下、「記録及び／又は再生」を「記録／再生」と記載する）を行える高密度光ディスクシステムの一例であるＮＡ０．８５、光源波長４０５ｎｍの仕様で情報記録／再生を行う光ディスク、いわゆるＢｌｕ－ｒａｙ　Ｄｉｓｃ（以下、ＢＤという）では、ＤＶＤ（ＮＡ０．６、光源波長６５０ｎｍ、記憶容量４．７ＧＢ）と同じ大きさである直径１２ｃｍの光ディスクに対して、１層あたり２５ＧＢの情報の記録が可能である。 In recent years, an example of a high-density optical disk system capable of recording and / or reproducing information (hereinafter, “recording and / or reproduction” is referred to as “recording / reproduction”) using a blue-violet semiconductor laser having a wavelength of about 400 nm. Same as DVD (NA 0.6, light source wavelength 650 nm, storage capacity 4.7 GB) in an optical disc that records and reproduces information with specifications of NA 0.85 and light source wavelength 405 nm, so-called Blu-ray Disc (hereinafter referred to as BD). Information of 25 GB per layer can be recorded on an optical disc having a diameter of 12 cm.
　ところで、かかるタイプの高密度光ディスクに対して適切に情報の記録／再生ができると言うだけでは、光ディスクプレーヤ／レコーダ（光情報記録再生装置）の製品としての価値は十分なものとはいえない。現在において、多種多様な情報を記録したＤＶＤやＣＤ（コンパクトディスク）が販売されている現実をふまえると、高密度光ディスクに対して情報の記録／再生ができるだけでは足らず、例えばユーザが所有しているＤＶＤやＣＤに対しても同様に適切に情報の記録／再生ができるようにすることが、高密度光ディスク用の光ディスクプレーヤ／レコーダとしての商品価値を高めることに通じるのである。このような背景から、高密度光ディスク用の光ディスクプレーヤ／レコーダに搭載される光ピックアップ装置は、高密度光ディスクとＤＶＤ、更にはＣＤとの何れに対しても互換性を維持しながら適切に情報を記録／再生できる性能を有することが望まれる。 By the way, the value as a product of an optical disc player / recorder (optical information recording / reproducing device) cannot be said to be sufficient simply by saying that information can be appropriately recorded / reproduced on such a high-density optical disc. In light of the reality that DVDs and CDs (compact discs) on which a wide variety of information is recorded are currently being sold, it is not possible to record / reproduce information on high-density optical discs. Similarly, making it possible to appropriately record / reproduce information on DVDs and CDs leads to an increase in commercial value as an optical disc player / recorder for high-density optical discs. From such a background, an optical pickup device mounted on an optical disc player / recorder for high density optical discs can appropriately receive information while maintaining compatibility with both high density optical discs, DVDs, and even CDs. It is desired to have a performance capable of recording / reproducing.
　高密度光ディスクとＤＶＤ、更にはＣＤとの何れに対しても互換性を維持しながら適切に情報を記録／再生できるようにする方法として、高密度光ディスク用の光学系とＤＶＤやＣＤ用の光学系とを情報を記録／再生する光ディスクに応じて選択的に切り替える方法が考えられるが、複数の光学系が必要となるので、小型化に不利であり、またコストが増大する。 As a method for recording / reproducing information appropriately while maintaining compatibility with both high-density optical discs and DVDs, and even CDs, optical systems for high-density optical discs and optical systems for DVDs and CDs are used. A method of selectively switching between systems depending on an optical disk on which information is recorded / reproduced is conceivable, but a plurality of optical systems are required, which is disadvantageous for miniaturization and increases costs.
　従って、光ピックアップ装置の構成を簡素化し、低コスト化を図るためには、互換性を有する光ピックアップ装置においても、高密度光ディスク用の光学系とＤＶＤやＣＤ用の光学系とを共通化して、光ピックアップ装置を構成する光学部品点数を極力減らすのが好ましい。そして、光ディスクに対向して配置される対物光学素子をなるべく共通化することが光ピックアップ装置の構成の小型化・低コスト化に最も有利となる。 Therefore, in order to simplify the configuration of the optical pickup device and reduce the cost, the optical system for high-density optical discs and the optical system for DVDs and CDs must be shared in compatible optical pickup devices. It is preferable to reduce the number of optical components constituting the optical pickup device as much as possible. In addition, it is most advantageous for miniaturization and cost reduction of the configuration of the optical pickup device to make the objective optical element arranged facing the optical disc as common as possible.
　特許文献１、２には、小型化・低コスト化を図るため、互いに異なる３つの波長の光束を出射できる半導体レーザを１パッケージに収容した光源及び共通の光検出器を用いて、高密度光ディスクと従来のＤＶＤ及びＣＤに対して互換可能に情報の記録及び／又は再生を行う光ピックアップ装置が記載されている。 Patent Documents 1 and 2 disclose a high-density optical disk using a light source and a common photodetector that house a semiconductor laser capable of emitting light beams of three different wavelengths in one package in order to reduce the size and cost. And an optical pickup device for recording and / or reproducing information so as to be compatible with conventional DVDs and CDs.
　一方、特許文献３には、３つの半導体レーザを１パッケージに収めた光源が開示されている。また、特許文献４には複数の半導体レーザ素子を備えた半導体レーザ装置が開示されている。 On the other hand, Patent Document 3 discloses a light source in which three semiconductor lasers are housed in one package. Patent Document 4 discloses a semiconductor laser device including a plurality of semiconductor laser elements.
　特許文献５には、波長λ１の光束が入射したときは０次回折光を発生させ、波長λ２の光束が入射したときはＭ次回折光を発生させ、波長λ３の光束が入射したときはＮ次回折光を発生させる回折素子が開示されている。 Patent Document 5 discloses that 0th order diffracted light is generated when a light beam having a wavelength λ1 is incident, Mth order diffracted light is generated when a light beam having a wavelength λ2 is incident, and Nth order diffracted light is incident when a light beam having a wavelength λ3 is incident. A diffractive element that generates the above is disclosed.
特開２００５－３２７４０３号公報JP 2005-327403 A 特開２００６－９９９４１号公報JP 2006-99941 A 特開２００６－２６９９８７号公報JP 2006-269987 A 特開２００４－３１９９１５号公報JP 2004-319915 A 特開２００７－２９４０２９号公報JP 2007-294029 A
　ところで、３つの半導体レーザを１パッケージに収めた光源の場合、各発光部が光軸直交方向にずれるため、単一の光検出器を用いてスポット検出を行う場合、発光部のズレ量に応じて各光束をシフトさせる必要がある。特許文献１、２においては、回折溝を用いて光束をシフトさせているが、発光点の間隔を既定値に精度良く合わせることが前提となっている。 By the way, in the case of a light source in which three semiconductor lasers are housed in one package, each light emitting unit is shifted in the direction perpendicular to the optical axis. It is necessary to shift each light flux. In Patent Documents 1 and 2, the light flux is shifted using a diffraction groove, but it is assumed that the interval between the light emitting points is accurately adjusted to a predetermined value.
　特許文献３によれば、４０５ｎｍ程度の光束を出射するいわゆる青紫色半導体レーザは、ＧａＮ基板に形成されるが、６５５ｎｍ前後の光束を出射するいわゆる赤色半導体レーザと、７８５ｎｍ前後の光束を出射するいわゆる赤外半導体レーザとは、ＧａＡｓ基板に形成されている。ここで、同一基板上に異なる半導体レーザを形成する場合（モノリシック構造という）、比較的容易に発光点間隔を精度良く維持することができる。ところが、別基板にそれぞれ半導体レーザを形成すると、同一パッケージに組み付ける際に、互いの発光点の間隔がばらつくことは避けられない（特許文献４の段落［００１０］、［００１１］、［００１２］参照）。しかるに、発光点の間隔が許容誤差を超えると、光検出器の受光面に光束が適切に集光されない恐れがある。これに対し、許容誤差範囲内に発光点の間隔を抑えると、歩留まりが悪化し、コストが増大するという問題がある。尚、特許文献５には、波長λ１の光束が入射したときは０次回折光を発生させ、波長λ２の光束が入射したときはＭ次回折光を発生させ、波長λ３の光束が入射したときはＮ次回折光を発生させる回折素子が開示されているが、かかる回折素子を用いて、波長λ１の光束の発光点と、波長λ２、λ３の光束の発光点との間の距離のバラツキにより発生する集光位置のズレを補正するという思想について、特許文献５には開示も示唆もされていない。 According to Patent Document 3, a so-called blue-violet semiconductor laser that emits a light beam of about 405 nm is formed on a GaN substrate. An infrared semiconductor laser is formed on a GaAs substrate. Here, when different semiconductor lasers are formed on the same substrate (referred to as a monolithic structure), the emission point interval can be maintained with high accuracy relatively easily. However, when semiconductor lasers are formed on different substrates, it is inevitable that the intervals between the light emitting points vary when assembled in the same package (see paragraphs [0010], [0011], and [0012] of Patent Document 4). ). However, if the interval between the light emitting points exceeds the allowable error, the light flux may not be properly condensed on the light receiving surface of the photodetector. On the other hand, if the interval between the light emitting points is suppressed within the allowable error range, there is a problem that the yield is deteriorated and the cost is increased. In Patent Document 5, zero-order diffracted light is generated when a light beam with wavelength λ1 is incident, M-order diffracted light is generated when a light beam with wavelength λ2 is incident, and N when a light beam with wavelength λ3 is incident. A diffractive element that generates next-order diffracted light is disclosed, but by using such a diffractive element, there is a collection caused by variation in the distance between the light emitting point of the light beam having the wavelength λ1 and the light emitting point of the light beam having the wavelengths λ2 and λ3. Patent Document 5 does not disclose or suggest the idea of correcting the deviation of the optical position.
　本発明は、上述の問題を考慮したものであり、小型化を図りコストを抑えつつも、異なる３種類の光ディスクに対して適切に情報の記録／再生を行える光ピックアップ装置に用いる回折素子を提供することを目的とする。 The present invention takes the above-described problems into consideration, and provides a diffraction element for use in an optical pickup device capable of appropriately recording / reproducing information with respect to three different types of optical disks while reducing the size and reducing the cost. The purpose is to do.
　請求項１に記載の回折素子は、波長λ１の第１光束を出射する第１発光部と、波長λ２（λ１＜λ２）の第２光束を出射する第２発光部と、波長λ３（λ２＜λ３）の第３光束を出射する第３発光部とを備えた光源と、対物光学系と、単一の光検出器と、前記光源と前記光検出器との間の光路内に移動可能に配置され、前記第１光束と前記第２光束と前記第３光束が共通して通過する回折素子とを有し、前記第１発光部からの光束を、前記対物光学系により第１光ディスクの情報記録面上に集光させることでスポットを形成し、その反射光を受光した前記光検出器からの信号に基づいて、前記第１光ディスクに対して情報の記録及び／又は再生を行い、前記第２発光部からの光束を、前記対物光学系により第２光ディスクの情報記録面上に集光させることでスポットを形成し、その反射光を受光した前記光検出器からの信号に基づいて、前記第２光ディスクに対して情報の記録及び／又は再生を行い、前記第３発光部からの光束を、前記対物光学系により第３光ディスクの情報記録面上に集光させることでスポットを形成し、その反射光を受光した前記光検出器からの信号に基づいて、前記第３光ディスクに対して情報の記録及び／又は再生を行う光ピックアップ装置に用いる回折素子であって、
　前記光源は、前記第２発光部と前記第３発光部は同一のチップ上に形成され、前記第１発光部は、前記第２発光部及び前記第３発光部とは異なるチップ上に形成されており、
　前記回折素子は、前記第１の光束は透過し、かつ、前記第２の光束、及び、前記第３の光束は回折する回折溝を有することを特徴とする。 The diffractive element according to claim 1 includes a first light emitting unit that emits a first light beam having a wavelength λ1, a second light emitting unit that emits a second light beam having a wavelength λ2 (λ1 <λ2), and a wavelength λ3 (λ2 < λ3) a third light source that emits a third light beam, an objective optical system, a single photodetector, and a light path between the light source and the photodetector so as to be movable A diffraction element that is disposed and through which the first light beam, the second light beam, and the third light beam pass in common, and the light beam from the first light emitting unit is transmitted to the information on the first optical disk by the objective optical system. A spot is formed by condensing on the recording surface, and information is recorded and / or reproduced on the first optical disk based on a signal from the photodetector that has received the reflected light, and the first 2 The light flux from the light emitting section is condensed on the information recording surface of the second optical disk by the objective optical system. In this way, a spot is formed and information is recorded and / or reproduced on the second optical disc based on a signal from the photodetector that receives the reflected light, and a light beam from the third light emitting unit. Is focused on the information recording surface of the third optical disk by the objective optical system, and a spot is formed. Based on the signal from the photodetector that receives the reflected light, the spot is formed on the third optical disk. A diffraction element used in an optical pickup device for recording and / or reproducing information,
In the light source, the second light emitting unit and the third light emitting unit are formed on the same chip, and the first light emitting unit is formed on a chip different from the second light emitting unit and the third light emitting unit. And
The diffractive element has a diffraction groove that transmits the first light flux and diffracts the second light flux and the third light flux.
　本発明の原理を、図１を参照して説明する。尚、図１では理解しやすいように、第１の光束と第２の光束と第３の光束とを上下方向にシフトして描いているが、紙面垂直方向に重なっていてもよい。本発明の回折素子に、波長λ１の光束を入射させた場合、回折素子から出射する回折光は０次回折光であるため素通り（透過）する。これに対し、波長λ２の光束を入射させた場合、回折素子から出射する回折光はｍ次（ｍ≠０）回折光となるため回折角θ２が与えられ、波長λ１の光束とは異なる方向に出射されることとなる。同様に、波長λ３の光束を入射させた場合、回折素子から出射する回折光はｎ次（ｎ≠０）回折光となるため回折角θ３が与えられ、波長λ１の光束とは異なる方向に出射されることとなる。ここで、光源の製造誤差により、第１発光部と第２発光部、及び、第１発光部と第３発光部との間隔が設計値からずれたために、光検出器の受光面上において、波長λ１の光束の受光位置Ｐ１が最適位置となるように、光検出器を図１の上下方向にシフト調整した場合を仮定すると、光検出器の受光面上において、波長λ１の光束の受光位置Ｐ１は適切であるが、波長λ２の光束及び波長λ３の光束の受光位置Ｐ２，Ｐ３は、受光面位置に対して適切な位置からずれることになる。かかる場合、回折格子を光ピックアップ装置の光軸方向に位置を変えると、波長λ１の光束は素通りするので、光検出器の受光位置Ｐ１は不変であるのに対し、波長λ２の光束及び波長λ３の光束光束については、回折素子と光検出器との相対距離に応じて、受光位置がＰ２，Ｐ３からＰ２’、Ｐ３’へとそれぞれ変化する。これにより、波長λ２，λ３の光束の受光位置を、波長λ１の光束とは独立して変化させることができ適切な位置とすることができる。 The principle of the present invention will be described with reference to FIG. In FIG. 1, the first light beam, the second light beam, and the third light beam are drawn while being shifted in the vertical direction for easy understanding, but they may overlap in the direction perpendicular to the paper surface. When a light beam having a wavelength λ1 is incident on the diffraction element of the present invention, the diffracted light emitted from the diffraction element is zero-order diffracted light and passes (transmits). On the other hand, when the light beam having the wavelength λ2 is incident, the diffracted light emitted from the diffraction element is m-order (m ≠ 0) diffracted light, so that the diffraction angle θ2 is given, and the light beam has a different direction from the light beam having the wavelength λ1. It will be emitted. Similarly, when a light beam having a wavelength λ3 is incident, the diffracted light emitted from the diffraction element is an nth order (n ≠ 0) diffracted light, so that a diffraction angle θ3 is given, and the light is emitted in a direction different from the light beam having the wavelength λ1. Will be. Here, due to the manufacturing error of the light source, the distance between the first light emitting unit and the second light emitting unit and the first light emitting unit and the third light emitting unit deviated from the design value. Assuming that the photodetector is shifted up and down in FIG. 1 so that the light receiving position P1 of the light beam with wavelength λ1 is the optimum position, the light receiving position of the light beam with wavelength λ1 on the light receiving surface of the light detector. Although P1 is appropriate, the light receiving positions P2 and P3 of the light beam having the wavelength λ2 and the light beam having the wavelength λ3 are shifted from appropriate positions with respect to the light receiving surface position. In such a case, if the position of the diffraction grating is changed in the optical axis direction of the optical pickup device, the light beam having the wavelength λ1 passes through, so that the light receiving position P1 of the photodetector is unchanged, whereas the light beam having the wavelength λ2 and the wavelength λ3 With respect to the luminous flux, the light receiving position changes from P2, P3 to P2 ′, P3 ′, respectively, according to the relative distance between the diffraction element and the photodetector. As a result, the light receiving position of the light beams having the wavelengths λ2 and λ3 can be changed independently of the light beam having the wavelength λ1, and an appropriate position can be obtained.
　従って３つの半導体レーザを１パッケージに収めた光源において、波長λ１の光束の発光点と、波長λ２、λ３の光束の発光点との間隔に誤差が生じていた場合でも、いずれの光束も光検出器の受光面の適切な位置に入射させることができる。尚、光ピックアップ装置の組み立て時に回折素子の光軸方向位置を調整し、組み立て後に固定してもよいし、回折素子を光軸方向に移動可能とし適時調整可能としてもよい。又、θ２＝θ３であると好ましい。 Therefore, in a light source in which three semiconductor lasers are housed in one package, even if there is an error in the distance between the light emitting point of the light beam with wavelength λ1 and the light emitting point of the light beam with wavelengths λ2 and λ3, any light beam is detected. Can be incident on an appropriate position on the light receiving surface of the detector. Note that the position of the diffraction element in the optical axis direction may be adjusted during assembly of the optical pickup device and fixed after assembly, or the diffraction element may be movable in the optical axis direction so that it can be adjusted in a timely manner. Moreover, it is preferable that θ2 = θ3.
　請求項２に記載の回折素子は、請求項１に記載の発明において、前記回折溝は一次元構造であることを特徴とする。 The diffraction element according to claim 2 is characterized in that, in the invention according to claim 1, the diffraction groove has a one-dimensional structure.
　請求項３に記載の回折素子は、請求項１又は２に記載の発明において、前記回折溝は、前記光ピックアップ装置の光学系の光軸に略平行に延在する３つ以上の段差面と、前記段差面と交差する３つ以上のテラス面とを有すると共に、隣接する前記テラス面が前記光ピックアップ装置の光軸方向に順次シフトしてなるステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって、ステップ周期構造を形成していることを特徴とする。 The diffraction element according to claim 3 is the invention according to claim 1 or 2, wherein the diffraction groove includes three or more step surfaces extending substantially parallel to the optical axis of the optical system of the optical pickup device. And a step unit formed by sequentially shifting the adjacent terrace surfaces in the optical axis direction of the optical pickup device as the optical axis of the optical pickup device. A step periodic structure is formed by arranging a plurality of elements along the intersecting direction.
　請求項４に記載の回折素子は、請求項１乃至３のいずれかに記載の発明において、以下の式（１）～（３）、
　３９５（ｎｍ）≦λ１≦４１５（ｎｍ）　　　　　　　　　（１）
　６３０（ｎｍ）≦λ２≦７００（ｎｍ）　　　　　　　　　（２）
　７５０（ｎｍ）≦λ３≦８５０（ｎｍ）　　　　　　　　　（３）
を満たすことを特徴とする。 A diffraction element according to a fourth aspect is the invention according to any one of the first to third aspects, wherein the following formulas (1) to (3),
395 (nm) ≦ λ1 ≦ 415 (nm) (1)
630 (nm) ≦ λ2 ≦ 700 (nm) (2)
750 (nm) ≦ λ3 ≦ 850 (nm) (3)
It is characterized by satisfying.
　請求項５に記載の回折素子は、請求項１から４までのいずれかに記載の発明において、前記回折素子に、前記第２の光束が入射した場合に発生する回折光の回折次数と、前記第３の光束が入射した場合に発生する回折光の回折次数の符号が互いに等しいことを特徴とする。 The diffraction element according to claim 5 is the diffraction element according to any one of claims 1 to 4, wherein the diffraction order of diffracted light generated when the second light flux is incident on the diffraction element; The signs of the diffraction orders of the diffracted light generated when the third light beam is incident are equal to each other.
　請求項６に記載の回折素子は、請求項３に記載の発明において、前記回折素子の素材のｄ線におけるアッベ数νｄが４０から７０の間であり、前記回折素子に前記第２の光束が入射した場合に発生する回折光の回折次数をｍ、前記回折素子に前記第３の光束が入射した場合に発生する回折光の回折次数をｎ、としたとき以下の式（４）～（７）、
　（ｍ，ｎ）＝（１，１）　　　　　　　　　　　　　　　　（４）
　（ｍ，ｎ）＝（－１，－１）　　　　　　　　　　　　　　（５）
　（ｍ，ｎ）＝（１，２）　　　　　　　　　　　　　　　　（６）
　（ｍ，ｎ）＝（１，３）　　　　　　　　　　　　　　　　（７）
のいずれかを満たすことを特徴とする。 A diffraction element according to a sixth aspect is the invention according to the third aspect, wherein an Abbe number νd in the d-line of the material of the diffraction element is between 40 and 70, and the second light flux is incident on the diffraction element. When the diffraction order of diffracted light generated when incident is m and the diffraction order of diffracted light generated when the third light beam is incident on the diffractive element is n, the following equations (4) to (7) ),
(M, n) = (1,1) (4)
(M, n) = (-1, -1) (5)
(M, n) = (1,2) (6)
(M, n) = (1,3) (7)
Any one of the above is satisfied.
　請求項７に記載の回折素子は、請求項３に記載の発明において、前記回折素子の素材のｄ線におけるアッベ数νｄが２０から４０の間であり、前記回折素子に前記第２の光束が入射した場合に発生する回折光の回折次数をｍ、前記回折素子に前記第３の光束が入射した場合に発生する回折光の回折次数をｎ、としたとき以下の式（８）～（１２）、
　（ｍ，ｎ）＝（１，１）　　　　　　　　　　　　　　　　（８）
　（ｍ，ｎ）＝（－１，－１）　　　　　　　　　　　　　　（９）
　（ｍ，ｎ）＝（－２，－１）　　　　　　　　　　　　　　（１０）
　（ｍ，ｎ）＝（１，２）　　　　　　　　　　　　　　　　（１１）
　（ｍ，ｎ）＝（－２，－２）　　　　　　　　　　　　　　（１２）
のいずれかを満たすことを特徴とする。 According to a seventh aspect of the present invention, in the invention of the third aspect, the Abbe number νd at the d-line of the material of the diffractive element is between 20 and 40, and the second light flux is incident on the diffractive element. When the diffraction order of diffracted light generated when incident is m and the diffraction order of diffracted light generated when the third light beam is incident on the diffractive element is n, the following equations (8) to (12) ),
(M, n) = (1,1) (8)
(M, n) = (-1, -1) (9)
(M, n) = (− 2, −1) (10)
(M, n) = (1,2) (11)
(M, n) = (− 2, −2) (12)
Any one of the above is satisfied.
　請求項８に記載の回折素子は、請求項６又は７に記載の発明において、以下の式（１３）～（１５）、
　｜ΣΦ１ｊ｜＝０　　　　　　　　　　　　　　　　　　　（１３）
　｜ΣΦ２ｊ｜＝ｍ　　　　　　　　　　　　　　　　　　　（１４）
　｜ΣΦ３ｊ｜＝ｎ　　　　　　　　　　　　　　　　　　　（１５）
但し、Φｉｊ（ｉ＝１、２、３）は、一ステップ単位内に存在する段差量（隣接する前記テラス面間の前記光軸方向シフト量とする）を第１段差量ｄ１、第２段差量ｄ２、第３段差量ｄ３、・・・・、第ｊ段差量ｄｊ、としたとき、各段差量により発生する第ｉ波長λｉの位相差である。
ここで、
Φｉｊ＝φｉｊ－ＲＯＵＮＤ（φｉ）
φｉｊ＝ｄｊ／λｉ×（ｎｉ－１）
ΣΦｉｊ＝Φｉ１＋Φｉ２＋・・・＋Φｉｊ－１＋Φｉｊ
第ｉ波長：λｉ（μｍ）
第ｉ波長λｉにおける回折素子の屈折率：ｎｉ
第ｊ段差：ｄｊ（μｍ）
任意の実数Ａの小数点以下第一位を四捨五入して得られる整数：ＲＯＵＮＤ（Ａ）
を満たすことを特徴とする。 A diffraction element according to an eighth aspect is the invention according to the sixth or seventh aspect, wherein the following formulas (13) to (15),
| ΣΦ1j | = 0 (13)
| ΣΦ2j | = m (14)
| ΣΦ3j | = n (15)
However, Φij (i = 1, 2, 3) is the first step amount d1 and the second step amount, which is the step amount existing in one step unit (the shift amount in the optical axis direction between the adjacent terrace surfaces). When the amount d2, the third step amount d3,..., The jth step amount dj, the phase difference of the i-th wavelength λi generated by each step amount.
here,
Φij = φij−ROUND (φi)
φij = dj / λi × (ni−1)
ΣΦij = Φi1 + Φi2 + ... + Φij-1 + Φij
I-th wavelength: λi (μm)
Refractive index of diffraction element at i-th wavelength λi: ni
J-th step: dj (μm)
Integer obtained by rounding the first decimal place of any real number A: ROUND (A)
It is characterized by satisfying.
　式（１３）～（１５）を満たすようにすれば、一ステップ単位内の全ての段差量に応じて発生する各光束の位相差を足したとき、その絶対値がそれぞれ、第１光束で略０、第２光束で略ｍ、第３光束で略ｎになるように各段差量を設定することによって、前記回折素子に第１光束が入射したときに０次回折光を発生させ、第２光束が入射したときにｍ次回折光を発生させ、第３光束が入射したときにｎ次回折光を発生させることができる。 If Expressions (13) to (15) are satisfied, when the phase differences of the light beams generated in accordance with all the step amounts in one step unit are added, the absolute values of the first light beams are approximately equal. By setting each step amount so that 0, the second light beam is approximately m, and the third light beam is approximately n, the 0th-order diffracted light is generated when the first light beam is incident on the diffraction element, and the second light beam is generated. M-order diffracted light can be generated when the light enters, and n-order diffracted light can be generated when the third light beam enters.
　請求項９に記載の回折素子は、請求項１から７までのいずれかに記載の発明において、前記回折溝は、前記光ピックアップ装置の光学系の光軸に略平行に延在する３つ以上の第１段差面と、前記第１段差面と交差する３つ以上の第１テラス面とを有すると共に、隣接する前記第１テラス面が前記光ピックアップ装置の光軸方向に順次シフトしてなる第１ステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第１ステップ周期構造と、前記光ピックアップ装置の光軸に略平行に延在する２つの第２段差面と、前記第２段差面と交差する２つの第２テラス面とを有し、前記２つの第２段差面が光軸直交方向に重なり合う第２ステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第２ステップ周期構造とを、互いに周期を合わせて重畳してなることを特徴とする。 A diffraction element according to a ninth aspect is the invention according to any one of the first to seventh aspects, wherein the diffraction grooves are three or more extending substantially parallel to an optical axis of an optical system of the optical pickup device. The first step surface and three or more first terrace surfaces intersecting the first step surface, and the adjacent first terrace surfaces are sequentially shifted in the optical axis direction of the optical pickup device. A first step periodic structure formed by arranging a plurality of first step units along a direction intersecting the optical axis of the optical pickup device, and extends substantially parallel to the optical axis of the optical pickup device. A second step unit having two second step surfaces and two second terrace surfaces intersecting the second step surface, wherein the two second step surfaces overlap in a direction perpendicular to the optical axis; Intersects the optical axis of the device Along the direction of the second step periodic structure formed by arranging a plurality, characterized by comprising superimposed together period each other.
　請求項１０に記載の回折素子は、請求項１から７までのいずれかに記載の発明において、前記回折溝は、前記光ピックアップ装置の光学系の光軸に略平行に延在する５つ以上の第１段差面と、前記第１段差面と交差する５つ以上の第１テラス面とを有すると共に、隣接する前記第１テラス面が前記光ピックアップ装置の光軸方向に順次シフトしてなる第１ステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第１ステップ周期構造と、前記光ピックアップ装置の光軸に略平行に延在する２つの第２段差面と、前記第２段差面と交差する２つの第２テラス面とを有し、前記２つの第２段差面が光軸直交方向に重なり合う第２ステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第２ステップ周期構造と、前記光ピックアップ装置の光軸に略平行に延在する２つの第３段差面と、前記第３段差面と交差する２つの第３テラス面とを有し、前記２つの第３段差面が光軸直交方向に重なり合う第３ステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第３ステップ周期構造とを、互いに周期を合わせて重畳してなることを特徴とする。 According to a tenth aspect of the present invention, there is provided the diffraction element according to any one of the first to seventh aspects, wherein the diffraction grooves are five or more extending substantially parallel to the optical axis of the optical system of the optical pickup device. The first step surface and five or more first terrace surfaces intersecting the first step surface, and the adjacent first terrace surfaces are sequentially shifted in the optical axis direction of the optical pickup device. A first step periodic structure formed by arranging a plurality of first step units along a direction intersecting the optical axis of the optical pickup device, and extends substantially parallel to the optical axis of the optical pickup device. A second step unit having two second step surfaces and two second terrace surfaces intersecting the second step surface, wherein the two second step surfaces overlap in a direction perpendicular to the optical axis; Crosses the optical axis of the device A second step periodic structure formed by arranging a plurality of the stepped portions along a direction, two third step surfaces extending substantially parallel to the optical axis of the optical pickup device, and the third step surface. A plurality of third step units having two third terrace surfaces and overlapping the two third step surfaces in the direction perpendicular to the optical axis are arranged along a direction intersecting the optical axis of the optical pickup device. The third step periodic structure formed by the above is overlapped with the same period.
　請求項１１に記載の回折素子は、請求項１から１０までのいずれかに記載の発明において、以下の式を満たすことを特徴とする。 The diffraction element according to claim 11 is characterized in that, in the invention according to any one of claims 1 to 10, the following expression is satisfied.
　｜ｍ｜＝｜ｎ｜　　　　　　　　　　　　　　　　　　（１６）
　請求項１２に記載の回折素子は、請求項１から１１までのいずれかに記載の発明において、前記回折溝は、平行平板上に形成されていることを特徴とする。 | M | = | n | (16)
A diffractive element according to a twelfth aspect is characterized in that, in the invention according to any one of the first to eleventh aspects, the diffraction groove is formed on a parallel plate.
　請求項１３に記載の光ピックアップ装置は、請求項１から１２までのいずれかに記載の回折素子を搭載したことを特徴とする。 An optical pickup device according to a thirteenth aspect includes the diffraction element according to any one of the first to twelfth aspects.
　請求項１４に記載の光ピックアップ装置は、請求項１３に記載の発明において、前記回折素子に前記第２の光束が入射した場合に発生する回折光の回折次数をｍ、前記回折素子に前記第３の光束が入射した場合に発生する回折光の回折次数をｎ、前記第１発光部と前記第２発光部の光軸直交方向の間隔をＡ、前記第１発光部と前記第３発光部の光軸直交方向の間隔をＢとしたとき、以下の式（１７）、を満たすことを特徴とする。
０．９×（λ２×｜ｍ｜）／（λ３×｜ｎ｜）≦Ａ／Ｂ≦１．１×
　　　　　　　　　　（λ２×｜ｍ｜）／（λ３×｜ｎ｜）　　　（１７）
を満たすことを特徴とする。 An optical pickup device according to a fourteenth aspect is the optical pickup device according to the thirteenth aspect, wherein the diffraction order of the diffracted light generated when the second light flux is incident on the diffraction element is m, and the diffraction order is the first. N is the diffraction order of the diffracted light generated when three light beams are incident, A is the distance in the direction perpendicular to the optical axis between the first light emitting part and the second light emitting part, and the first light emitting part and the third light emitting part. When the interval in the direction perpendicular to the optical axis is B, the following expression (17) is satisfied.
0.9 × (λ2 × | m |) / (λ3 × | n |) ≦ A / B ≦ 1.1 ×
(Λ2 × | m |) / (λ3 × | n |) (17)
It is characterized by satisfying.
　回折溝で発生する回折光の回折角は、波長と回折次数の積で決まる。図２において、第１発光部ＬＤ１と第２発光部ＬＤ２の光軸直交方向の間隔をＡ、第１発光部ＬＤ１と第３発光部ＬＤ３の光軸直交方向の間隔をＢとしたとき、回折素子ＤＥに第２の光束λ２が入射した場合に発生する回折光の回折次数をｍ、回折素子ＤＥに第３の光束λ３が入射した場合に発生する回折光の回折次数をｎとすると、（１７）式を満たすように、所定の間隔で発光部ＬＤ１～ＬＤ３を配置することで、光検出器の所定領域に３つの光束λ１～λ３を適切に入射させることができる。 The diffraction angle of the diffracted light generated in the diffraction groove is determined by the product of the wavelength and the diffraction order. In FIG. 2, when the distance between the first light emitting part LD1 and the second light emitting part LD2 in the direction perpendicular to the optical axis is A, and the distance between the first light emitting part LD1 and the third light emitting part LD3 in the direction perpendicular to the optical axis is B, diffraction is performed. If the diffraction order of the diffracted light generated when the second light beam λ2 is incident on the element DE is m, and the diffraction order of the diffracted light generated when the third light beam λ3 is incident on the diffractive element DE is n, ( By arranging the light emitting portions LD1 to LD3 at a predetermined interval so as to satisfy the equation (17), the three light beams λ1 to λ3 can be appropriately incident on the predetermined region of the photodetector.
　本明細書中において、回折溝により回折作用を受けずに透過する光束を０次回折光と呼ぶ。又、本明細書においては、光ピックアップ装置の光学系の光軸を、「光軸」と略する場合もある。 In this specification, a light beam transmitted without being diffracted by the diffraction groove is referred to as zero-order diffracted light. Further, in this specification, the optical axis of the optical system of the optical pickup device may be abbreviated as “optical axis”.
　本発明に係る光ピックアップ装置の光源は、第１発光部、第２発光部、第３発光部の少なくとも３つの発光部を有する。さらに、本発明の光ピックアップ装置は、第１光束を第１光ディスクの情報記録面上に集光させ、第２光束を第２光ディスクの情報記録面上に集光させ、第３光束を第３光ディスクの情報記録面上に集光させるための集光光学系を有する。また、本発明の光ピックアップ装置は、第１光ディスク、第２光ディスク又は第３光ディスクの情報記録面からの反射光束を受光する受光素子を有する。 The light source of the optical pickup device according to the present invention has at least three light emitting units, a first light emitting unit, a second light emitting unit, and a third light emitting unit. Furthermore, the optical pickup device of the present invention condenses the first light flux on the information recording surface of the first optical disc, condenses the second light flux on the information recording surface of the second optical disc, and causes the third light flux to be third. It has a condensing optical system for condensing on the information recording surface of the optical disc. The optical pickup device of the present invention includes a light receiving element that receives a reflected light beam from the information recording surface of the first optical disc, the second optical disc, or the third optical disc.
　第１光ディスクは、厚さがｔ１の保護基板と情報記録面とを有する。第２光ディスクは厚さがｔ２（ｔ１＜ｔ２）の保護基板と情報記録面とを有する。第３光ディスクは、厚さがｔ３（ｔ２＜ｔ３）の保護基板と情報記録面とを有する。第１光ディスクがＢＤであり、第２光ディスクがＤＶＤであり、第３光ディスクがＣＤであることが好ましいが、これに限られるものではない。なお、第１光ディスク、第２光ディスク又は第３光ディスクは、複数の情報記録面を有する複数層の光ディスクでもよい。 The first optical disc has a protective substrate having a thickness t1 and an information recording surface. The second optical disc has a protective substrate having a thickness t2 (t1 <t2) and an information recording surface. The third optical disc has a protective substrate having a thickness t3 (t2 <t3) and an information recording surface. The first optical disc is preferably a BD, the second optical disc is a DVD, and the third optical disc is preferably a CD, but is not limited thereto. The first optical disc, the second optical disc, or the third optical disc may be a multi-layer optical disc having a plurality of information recording surfaces.
　本明細書において、ＢＤとは、波長３９０～４１５ｎｍ程度の光束、ＮＡ０．８～０．９程度の対物レンズにより情報の記録／再生が行われ、保護基板の厚さが０．０５～０．１２５ｍｍ程度であるＢＤ系列光ディスクの総称であり、単一の情報記録層のみ有するＢＤや、２層以上の情報記録層を有するＢＤ等を含むものである。更に、本明細書においては、ＤＶＤとは、ＮＡ０．６０～０．６７程度の対物レンズにより情報の記録／再生が行われ、保護基板の厚さが０．６ｍｍ程度であるＤＶＤ系列光ディスクの総称であり、ＤＶＤ－ＲＯＭ、ＤＶＤ－Ｖｉｄｅｏ、ＤＶＤ－Ａｕｄｉｏ、ＤＶＤ－ＲＡＭ、ＤＶＤ－Ｒ、ＤＶＤ－ＲＷ、ＤＶＤ＋Ｒ、ＤＶＤ＋ＲＷ等を含む。また、本明細書においては、ＣＤとは、ＮＡ０．４５～０．５１程度の対物レンズにより情報の記録／再生が行われ、保護基板の厚さが１．２ｍｍ程度であるＣＤ系列光ディスクの総称であり、ＣＤ－ＲＯＭ、ＣＤ－Ａｕｄｉｏ、ＣＤ－Ｖｉｄｅｏ、ＣＤ－Ｒ、ＣＤ－ＲＷ等を含む。尚、記録密度については、ＢＤの記録密度が最も高く、次いでＤＶＤ、ＣＤの順に低くなる。 In this specification, BD means that information is recorded / reproduced by a light beam having a wavelength of about 390 to 415 nm and an objective lens having an NA of about 0.8 to 0.9, and the thickness of the protective substrate is 0.05 to 0.00 mm. It is a generic term for a BD series optical disc of about 125 mm, and includes a BD having only a single information recording layer, a BD having two or more information recording layers, and the like. Further, in this specification, DVD is a general term for DVD series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.60 to 0.67 and the thickness of the protective substrate is about 0.6 mm. Including DVD-ROM, DVD-Video, DVD-Audio, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW, and the like. In this specification, CD is a general term for CD series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.45 to 0.51 and the thickness of the protective substrate is about 1.2 mm. Including CD-ROM, CD-Audio, CD-Video, CD-R, CD-RW and the like. As for the recording density, the recording density of BD is the highest, followed by the order of DVD and CD.
　なお、保護基板の厚さｔ１、ｔ２、ｔ３に関しては、以下の条件式（１８）、（１９）、（２０）、
　０．０５０ｍｍ≦ｔ１≦０．１２５ｍｍ　　　　　（１８）
　　　０．５ｍｍ≦ｔ２≦０．７ｍｍ　　　　　　　（１９）
　　　１．０ｍｍ≦ｔ３≦１．３ｍｍ　　　　　　　（２０）
を満たすことが好ましいが、これに限られない。尚、ここで言う、保護基板の厚さとは、光ディスク表面に設けられた保護基板の厚さのことである。即ち、光ディスク表面から、表面に最も近い情報記録面までの保護基板の厚さのことをいう。 In addition, regarding the thicknesses t1, t2, and t3 of the protective substrate, the following conditional expressions (18), (19), (20),
0.050 mm ≦ t1 ≦ 0.125 mm (18)
0.5mm ≦ t2 ≦ 0.7mm (19)
1.0 mm ≦ t3 ≦ 1.3 mm (20)
However, the present invention is not limited to this. The thickness of the protective substrate referred to here is the thickness of the protective substrate provided on the surface of the optical disk. That is, the thickness of the protective substrate from the optical disc surface to the information recording surface closest to the surface.
　本明細書において、第１発光部、第２発光部、第３発光部は、好ましくはレーザ光源である。レーザ光源としては、好ましくは半導体レーザ、シリコンレーザ等を用いることが出来る。第１発光部から出射される第１光束の第１波長λ１、第２発光部から出射される第２光束の第２波長λ２（λ２＞λ１）、第３発光部から出射される第３光束の第３波長λ３（λ３＞λ２）は以下の条件式（２１）、（２２）、
　１．５・λ１＜λ２＜１．７・λ１　　　　　　　（２１）
　１．８・λ１＜λ３＜２．０・λ１　　　　　　　（２２）
を満たすことが好ましい。 In the present specification, the first light emitting unit, the second light emitting unit, and the third light emitting unit are preferably laser light sources. As the laser light source, a semiconductor laser, a silicon laser, or the like can be preferably used. The first wavelength λ1 of the first light beam emitted from the first light emitting unit, the second wavelength λ2 of the second light beam emitted from the second light emitting unit (λ2> λ1), and the third light beam emitted from the third light emitting unit The third wavelength λ3 (λ3> λ2) of the following conditional expressions (21), (22),
1.5 · λ1 <λ2 <1.7 · λ1 (21)
1.8 · λ1 <λ3 <2.0 · λ1 (22)
It is preferable to satisfy.
　また、第１光ディスク、第２光ディスク、第３光ディスクとして、それぞれ、ＢＤ、ＤＶＤ及びＣＤが用いられる場合、第１発光部の第１波長λ１は好ましくは、３５０ｎｍ以上、４４０ｎｍ以下、より好ましくは、３９５ｎｍ以上、４１５ｎｍ以下であって、第２発光部の第２波長λ２は好ましくは５７０ｎｍ以上、７３０ｎｍ以下、より好ましくは、６３０ｎｍ以上、７００ｎｍ以下であって、第３発光部の第３波長λ３は好ましくは、７３０ｎｍ以上、８８０ｎｍ以下、より好ましくは、７５０ｎｍ以上、８５０ｎｍ以下である。 In addition, when BD, DVD, and CD are used as the first optical disc, the second optical disc, and the third optical disc, respectively, the first wavelength λ1 of the first light emitting unit is preferably 350 nm or more and 440 nm or less, more preferably The second wavelength λ2 of the second light emitting part is preferably 570 nm or more and 730 nm or less, more preferably 630 nm or more and 700 nm or less, and the third wavelength λ3 of the third light emitting part is 395 nm or more and 415 nm or less. Preferably, they are 730 nm or more and 880 nm or less, More preferably, they are 750 nm or more and 850 nm or less.
　第１発光部、第２発光部、第３発光部はユニット化された単一の光源となっていると好ましい。ユニット化とは、例えば第１発光部、第２発光部、第３発光部とが１パッケージに固定収納されているようなものをいう。この場合、第１発光部、第２発光部、第３発光部は光ピックアップ装置の光軸に交差する方向に沿って異なる位置に配置されている。尚、光源において、第２発光部及び第３発光部とは同一チップに形成され、第１発光部はそれとは別なチップに形成されていることが望ましい。このような光源の例が、特開２００４－３１９９１５号公報に開示されている。 The first light emitting unit, the second light emitting unit, and the third light emitting unit are preferably a single light source that is unitized. The unitization means that the first light emitting unit, the second light emitting unit, and the third light emitting unit are fixedly housed in one package, for example. In this case, the first light emitting unit, the second light emitting unit, and the third light emitting unit are arranged at different positions along the direction intersecting the optical axis of the optical pickup device. In the light source, it is preferable that the second light emitting unit and the third light emitting unit are formed on the same chip, and the first light emitting unit is formed on a different chip. An example of such a light source is disclosed in Japanese Patent Application Laid-Open No. 2004-319915.
　受光素子としては、フォトダイオードなどの光検出器が好ましく用いられる。光ディスクの情報記録面上で反射した光が受光素子へ入射し、その出力信号を用いて、各光ディスクに記録された情報の読み取り信号が得られる。さらに、受光素子上のスポットの形状変化、位置変化による光量変化を検出して、合焦検出やトラック検出を行い、この検出に基づいて、合焦、トラッキングのために対物レンズを移動させることが出来る。受光素子は、複数の光検出器からなっていてもよい。受光素子は、メインの光検出器とサブの光検出器を有していてもよい。例えば、情報の記録再生に用いられるメイン光を受光する光検出器の両脇に２つのサブの光検出器を設け、当該２つのサブの光検出器によってトラッキング調整用のサブ光を受光するような受光素子としてもよい。また、受光素子は第１、第２、第３発光部のそれぞれに対応した複数（少なくとも３つ以上）の受光部を、光ピックアップ装置の光軸直交方向に異ならせて配置している。 As the light receiving element, a photodetector such as a photodiode is preferably used. Light reflected on the information recording surface of the optical disc enters the light receiving element, and a read signal of information recorded on each optical disc is obtained using the output signal. Furthermore, it detects the change in the light amount due to the spot shape change and position change on the light receiving element, performs focus detection and track detection, and based on this detection, the objective lens can be moved for focusing and tracking I can do it. The light receiving element may comprise a plurality of photodetectors. The light receiving element may have a main photodetector and a sub photodetector. For example, two sub photodetectors are provided on both sides of a photodetector that receives main light used for recording and reproducing information, and the sub light for tracking adjustment is received by the two sub photodetectors. It is good also as a simple light receiving element. In the light receiving element, a plurality (at least three or more) of light receiving portions corresponding to the first, second, and third light emitting portions are arranged differently in the direction perpendicular to the optical axis of the optical pickup device.
　集光光学系は、対物レンズを有する。集光光学系は、対物レンズの他にコリメータ（コリメートレンズと称することもある）等のカップリングレンズを有していることが好ましい。カップリングレンズとは、対物レンズと光源の間に配置され、光束の発散角を変える単レンズ又はレンズ群のことをいう。コリメータは、カップリングレンズの一種で、コリメータに入射した光を平行光にして出射するレンズである。本明細書において、対物レンズとは、光ピックアップ装置において光ディスクに対向する位置に配置され、光源から射出された光束を光ディスクの情報記録面上に集光する機能を有する光学系を指す。対物レンズは、二つ以上の複数のレンズ及び／又は光学素子から構成されていてもよいし、単玉のレンズのみからなっていてもよいが、好ましくは単玉の凸レンズからなる対物レンズである。また、対物レンズは、ガラスレンズであってもプラスチックレンズであっても、又は、ガラスレンズの上に光硬化性樹脂、紫外線硬化性樹脂、又は熱硬化性樹脂などで光路差付与構造を設けたハイブリッドレンズであってもよい。対物レンズが複数のレンズを有する場合は、ガラスレンズとプラスチックレンズを混合して用いてもよい。対物レンズが複数のレンズを有する場合、光路差付与構造を有する平板光学素子と非球面レンズ（光路差付与構造を有していてもいなくてもよい）の組み合わせであってもよい。また、対物レンズは、屈折面が非球面であることが好ましい。また、対物レンズは、光路差付与構造が設けられるベース面が非球面であることが好ましい。 The condensing optical system has an objective lens. The condensing optical system preferably includes a coupling lens such as a collimator (sometimes referred to as a collimating lens) in addition to the objective lens. The coupling lens is a single lens or a lens group that is disposed between the objective lens and the light source and changes the divergence angle of the light beam. The collimator is a type of coupling lens, and is a lens that emits light incident on the collimator as parallel light. In this specification, the objective lens refers to an optical system that is disposed at a position facing the optical disk in the optical pickup device and has a function of condensing the light beam emitted from the light source onto the information recording surface of the optical disk. The objective lens may be composed of two or more lenses and / or optical elements, or may be composed of a single lens, but is preferably an objective lens composed of a single convex lens. . The objective lens may be a glass lens or a plastic lens, or an optical path difference providing structure is provided on the glass lens with a photocurable resin, an ultraviolet curable resin, or a thermosetting resin. A hybrid lens may also be used. When the objective lens has a plurality of lenses, a glass lens and a plastic lens may be mixed and used. When the objective lens includes a plurality of lenses, it may be a combination of a flat optical element having an optical path difference providing structure and an aspherical lens (which may or may not have an optical path difference providing structure). The objective lens preferably has a refractive surface that is aspheric. In the objective lens, the base surface on which the optical path difference providing structure is provided is preferably an aspherical surface.
　対物レンズとしては、３波長で共用する単一の対物レンズを用いても良いし、２波長で共用する対物レンズと、残りの波長専用の対物レンズとを用いても良い。このような対物レンズは良く知られているので、説明を省略する。 As the objective lens, a single objective lens shared by three wavelengths may be used, or an objective lens shared by two wavelengths and an objective lens dedicated to the remaining wavelengths may be used. Such an objective lens is well known and will not be described.
　本発明の回折素子は、光源と受光素子の間の光路内であれば任意の位置に配置可能である。本発明の回折素子は、第１の光束が入射した場合には、０次回折光の回折効率が他の何れの回折次数の回折光の回折効率よりも高くなり、第２の光束が入射した場合には、ｍ次（ｍ≠０）回折光の回折効率が他の何れの回折次数の回折光の回折効率よりも高くなり、第３の光束が入射した場合には、ｎ次（ｎ≠０）回折光の回折効率が他の何れの回折次数の回折光の回折効率よりも高くなる回折溝を有する。このとき、回折素子の素材のｄ線におけるアッベ数νｄが４０から７０の間であるときは、光学材料が豊富であり、材料選択の自由度が大きいが、以下の式（４）～（７）、
　（ｍ，ｎ）＝（１，１）　　　　　　　　　　　　　　　　（４）
　（ｍ，ｎ）＝（－１，－１）　　　　　　　　　　　　　　（５）
　（ｍ，ｎ）＝（１，２）　　　　　　　　　　　　　　　　（６）
　（ｍ，ｎ）＝（１，３）　　　　　　　　　　　　　　　　（７）
のいずれかを満たすことが望ましい。 The diffractive element of the present invention can be arranged at any position as long as it is in the optical path between the light source and the light receiving element. In the diffraction element of the present invention, when the first light beam is incident, the diffraction efficiency of the 0th-order diffracted light is higher than the diffraction efficiency of any other diffraction order diffracted light, and the second light beam is incident. The diffraction efficiency of the mth order (m ≠ 0) diffracted light is higher than the diffraction efficiency of any other diffracted order diffracted light, and when the third light beam is incident, the nth order (n ≠ 0). ) It has a diffraction groove in which the diffraction efficiency of diffracted light is higher than the diffraction efficiency of diffracted light of any other diffraction order. At this time, when the Abbe number νd in the d-line of the material of the diffraction element is between 40 and 70, the optical material is abundant and the degree of freedom in material selection is large, but the following equations (4) to (7) ),
(M, n) = (1,1) (4)
(M, n) = (-1, -1) (5)
(M, n) = (1,2) (6)
(M, n) = (1,3) (7)
It is desirable to satisfy either of these.
　一方、回折素子の素材のｄ線におけるアッベ数νｄが２０から４０の間であるときは、第３光束の回折効率を向上することができるが、以下の式（８）～（１３）、
　（ｍ，ｎ）＝（１，１）　　　　　　　　　　　　　　　　（８）
　（ｍ，ｎ）＝（－１，－１）　　　　　　　　　　　　　　（９）
　（ｍ，ｎ）＝（－２，－１）　　　　　　　　　　　　　　（１０）
　（ｍ，ｎ）＝（１，２）　　　　　　　　　　　　　　　　（１１）
　（ｍ，ｎ）＝（－２，－２）　　　　　　　　　　　　　　（１２）
のいずれかを満たすことが望ましい。 On the other hand, when the Abbe number νd at the d-line of the material of the diffractive element is between 20 and 40, the diffraction efficiency of the third light beam can be improved, but the following equations (8) to (13),
(M, n) = (1,1) (8)
(M, n) = (-1, -1) (9)
(M, n) = (− 2, −1) (10)
(M, n) = (1,2) (11)
(M, n) = (− 2, −2) (12)
It is desirable to satisfy either of these.
　好ましくは、以下の式（１６）、
　｜ｍ｜＝｜ｎ｜　　　　　　　　　　　　　　　　　　　　（１６）
を満たすことである。 Preferably, the following formula (16),
| M | = | n | (16)
Is to satisfy.
　また、回折素子は、ガラス製又はプラスチック製とでき、図３に示すように平行平板上に形成されていると好ましい。尚、回折素子に、第２の光束が入射した場合に発生する回折光の回折次数と、第３の光束が入射した場合に発生する回折光の回折次数の符号が互いに等しいと好ましい。図１を参照して、第２の光束が入射した場合に発生する回折光の回折次数と、第３の光束が入射した場合に発生する回折光の回折次数の符号が異なると、回折格子から出射する第２の光束の回折光と第３の光束の回折光とが異なる方向（０次の回折光を０度とすると一方が＋方向、他方が－方向）に進行し、回折機能を用いたスポット位置調整が困難となるからである。 Further, the diffraction element can be made of glass or plastic and is preferably formed on a parallel plate as shown in FIG. It is preferable that the diffraction orders of the diffracted light generated when the second light beam is incident on the diffractive element are equal to the signs of the diffraction orders of the diffracted light generated when the third light beam is incident. Referring to FIG. 1, if the diffraction order of the diffracted light generated when the second light beam is incident and the sign of the diffraction order of the diffracted light generated when the third light beam are incident are different from the diffraction grating, The diffracted light of the emitted second light beam and the diffracted light of the third light beam travel in different directions (one is + direction when the 0th-order diffracted light is 0 degree, and the other is-direction). This is because it is difficult to adjust the spot position.
　さらに、回折素子は、回折溝をその表面に形成したプラスチック層をガラス基板上に接合したハイブリッド型構造としても良いし、あるいは、分散が互いに異なる材料を接合し、その接合面に回折溝を形成した接合型構造としても良い。回折素子をハイブリッド型構造とする場合は、プラスチック層として光硬化性樹脂、紫外線硬化性樹脂、又は熱硬化性樹脂を使用することが好ましい。また、回折溝を、接合型構造により構成することによって、異なる波長帯域の光の回折を抑えて、第２光束及び第３光束のみを選択的に所望の回折効率をもって構成することができる。例えば、回折溝を異なる材料により構成し、各材料として、第１波長λ１の光束における屈折率と、第２波長λ２及び第３波長λ３の光束における屈折率とで所要の屈折率差を有するものを選定することによって、回折効率において良好な波長選択性を有する回折溝を構成することができる。 Furthermore, the diffractive element may have a hybrid structure in which a plastic layer having diffraction grooves formed on the surface thereof is bonded onto a glass substrate, or materials having different dispersions are bonded to form a diffraction groove on the bonding surface. It is good also as a joined type structure. When the diffractive element has a hybrid structure, it is preferable to use a photocurable resin, an ultraviolet curable resin, or a thermosetting resin as the plastic layer. In addition, by configuring the diffraction grooves with a junction structure, it is possible to suppress diffraction of light in different wavelength bands and selectively configure only the second light flux and the third light flux with desired diffraction efficiency. For example, the diffraction groove is made of different materials, and each material has a required refractive index difference between the refractive index of the light beam having the first wavelength λ1 and the refractive index of the light beam of the second wavelength λ2 and the third wavelength λ3. By selecting this, it is possible to configure a diffraction groove having a favorable wavelength selectivity in diffraction efficiency.
　また、本明細書でいう回折溝とは、光軸に略平行に延在する段差面を有し、回折によって、特定の波長を有する光束の進行方向を変える作用を持たせる構造の総称である。尚、回折溝は、同心円状ではなく、直線状のような一次元格子であることが好ましい。一例を挙げると、回折溝は、図３の斜視図に示すように、基板上に光軸直交方向にストレートな形状で構成されており、それぞれの単位形状に特定の波長を有する光束が入射し、透過した光の波面が、隣り合う輪帯毎にズレを起こし、その結果、新たな波面を形成することによって光束の進行方向を変えるような構造を含むものである。回折溝は、好ましくは段差面を複数有し、段差面は光軸直交方向に周期的な間隔をもって配置されていてもよいし、光軸直交方向に非周期的な間隔をもって配置されていてもよい。回折溝は、一般に、様々な断面形状（光軸を含む面での断面形状）があり、光軸を含む断面形状がブレーズ型構造と階段型構造とに大別される。 In addition, the diffraction groove as used in this specification is a general term for a structure having a step surface extending substantially parallel to the optical axis and having an action of changing the traveling direction of a light beam having a specific wavelength by diffraction. . Note that the diffraction grooves are preferably not a concentric circle but a linear one-dimensional grating. For example, as shown in the perspective view of FIG. 3, the diffraction groove is formed in a straight shape on the substrate in a direction orthogonal to the optical axis, and a light beam having a specific wavelength is incident on each unit shape. The structure includes a structure in which the wavefront of the transmitted light shifts between adjacent annular zones, and as a result, a traveling direction of the light flux is changed by forming a new wavefront. The diffraction groove preferably has a plurality of step surfaces, and the step surfaces may be arranged at periodic intervals in the optical axis orthogonal direction or may be arranged at non-periodic intervals in the optical axis orthogonal direction. Good. In general, the diffraction grooves have various cross-sectional shapes (cross-sectional shapes on the plane including the optical axis), and the cross-sectional shapes including the optical axis are roughly classified into a blazed structure and a staircase structure.
　ブレーズ型構造とは、図４（ａ）、（ｂ）に示されるように、回折溝を有する回折素子の光軸を含む断面形状が、鋸歯状の形状ということであり、具体的には、光ピックアップ装置の略光軸方向（図で上下方向）に沿って延在する複数の段差面ＳＴと、隣接する段差面同士を連結する斜面ＣＰとを有する。尚、図４の例においては、上方が光源側、下方が光検出器側であって、平行平板上に回折溝が形成されているものとする。ブレーズ型構造において、１つのブレーズ単位の光軸垂直方向の長さをピッチＰという（図４（ａ）、（ｂ）参照）。また、ブレーズの光軸に平行方向の段差面の光軸方向長さを段差量Ｂ（又はブレーズ高さｈと称することもある）という（図４（ａ）参照）。 As shown in FIGS. 4 (a) and 4 (b), the blazed structure is a sawtooth shape in cross section including the optical axis of a diffraction element having a diffraction groove. It has a plurality of step surfaces ST extending along a substantially optical axis direction (vertical direction in the drawing) of the optical pickup device, and a slope CP connecting the adjacent step surfaces. In the example of FIG. 4, it is assumed that the upper side is the light source side, the lower side is the photodetector side, and a diffraction groove is formed on a parallel plate. In the blazed structure, the length in the direction perpendicular to the optical axis of one blaze unit is referred to as a pitch P (see FIGS. 4A and 4B). The length in the optical axis direction of the step surface parallel to the optical axis of the blaze is referred to as a step amount B (or sometimes referred to as a blaze height h) (see FIG. 4A).
　かかるブレーズ型構造は、後述する階段型構造と比べて、段差量が小さくなる傾向があるので、回折効率の波長依存性や温度依存性を小さくすることができるので、製造ばらつきにより発振波長が設計値からずれた光源であっても使用することが可能であり、使用可能な環境温度幅の広い光ピックアップ装置を提供することが可能となる。 Such a blazed structure tends to have a smaller step than the step structure described later, so that the wavelength dependence and temperature dependence of diffraction efficiency can be reduced. Even a light source deviating from the value can be used, and an optical pickup device having a wide usable environmental temperature range can be provided.
　また、階段型構造とは、図４（ｃ）、（ｄ）に示されるように、回折溝を有する光学素子の光軸を含む断面形状が、小階段状のもの（ステップ単位と称する）を複数有するということであり、具体的には、光ピックアップ装置の略光軸方向に沿って延在する複数の段差面ＳＴと、前記段差面と交差する複数のテラス面ＴＲとを有する。 In addition, as shown in FIGS. 4C and 4D, the staircase structure is a step-like structure in which the cross-sectional shape including the optical axis of an optical element having a diffraction groove is a step shape (referred to as a step unit). More specifically, it has a plurality of step surfaces ST extending substantially along the optical axis direction of the optical pickup device, and a plurality of terrace surfaces TR intersecting with the step surfaces.
　図４（ｃ）に示す階段型構造は、３つ以上（図示では５つ）の段差面ＳＴと、３つ以上（図示では５つ）のテラス面ＴＲとを有し、隣接するテラス面ＴＲが光ピックアップ装置の光軸方向に順次シフトしてなるステップ単位を、光ピックアップ装置の光軸に交差する方向（図で左右方向）に沿って複数個配置することによって、ステップ周期構造を形成してなるものである。即ち、特にテラス面ＴＲが３つ以上の階段型構造は、小さい段差面ＳＴと大きい段差面ＬＳＴとを有することになる。本明細書では、テラス面が３つの場合、３ステップ構造といい、図３に示すような４つの場合、４ステップ構造という。 The stepped structure shown in FIG. 4C has three or more (five in the drawing) step surfaces ST and three or more (five in the drawing) terrace surfaces TR, and adjacent terrace surfaces TR. The step periodic structure is formed by arranging a plurality of step units, which are sequentially shifted in the optical axis direction of the optical pickup device, along the direction intersecting the optical axis of the optical pickup device (left-right direction in the figure). It will be. That is, in particular, the staircase structure with three or more terrace surfaces TR has a small step surface ST and a large step surface LST. In this specification, when there are three terrace surfaces, it is called a three-step structure, and when there are four terrace surfaces, it is called a four-step structure.
　階段構造は、上述したブレーズ型構造と比べて、情報の記録／再生に使用する回折光と、不要次数光（情報の記録／再生に使用する回折光の次数とは異なる次数の回折光を指す）との回折角の差を大きくとることができるので、光検出器の受光面上で、情報の記録／再生に使用する回折光の集光スポットと、不要次数光の集光スポットの距離が小さくなりすぎず、良好な情報の記録／再生特性を得ることが可能となる。 The staircase structure refers to diffracted light used for information recording / reproduction and unnecessary-order light (diffracted light having a different order from the order of diffracted light used for information recording / reproduction, compared to the blazed structure described above. The difference between the diffraction angle and the collection spot of diffracted light used for recording / reproducing information and the collection spot of unnecessary order light on the light receiving surface of the photodetector is large. It is possible to obtain good information recording / reproducing characteristics without becoming too small.
　図４（ｄ）に示す回折溝は、略光軸方向に延在する隣接する段差面ＳＴ、ＳＴの端部同士により、間に挟まれたテラス面ＴＲを連結する構成であって、隣接するテラス面ＴＲ、ＴＲ同士は平行で光軸方向にシフトしている。本明細書では、テラス面が２つの場合、２ステップ構造という。尚、図４（ｅ）に示すように、最も高い側から１又は２以上のテラスＴＲを等量だけ低める方向にシフトしてなる構造も、階段型構造とする。 The diffraction grooves shown in FIG. 4D are configured to connect the terrace surfaces TR sandwiched between the end portions of the adjacent step surfaces ST and ST extending substantially in the optical axis direction. The terrace surfaces TR and TR are parallel to each other and shifted in the optical axis direction. In this specification, when there are two terrace surfaces, it is called a two-step structure. As shown in FIG. 4 (e), a structure in which one or more terraces TR are shifted in the direction of lowering by an equal amount from the highest side is also a staircase structure.
　また、階段型構造において、１つの階段単位の光軸垂直方向の長さをピッチＰという（図４（ｃ）、（ｄ）参照）。また、光軸方向に沿った段差ＬＳＴ、ＳＴの長さを段差量Ｂ１，Ｂ２という。３ステップ以上の階段型構造の場合、大段差量Ｂ１（第ｋ段差量）と小段差量Ｂ２とが存在することになる（図４（ｃ）参照）。一方、２ステップ構造の場合、基本的にＢ１＝Ｂ２である。 Also, in the staircase structure, the length of one staircase unit in the direction perpendicular to the optical axis is referred to as a pitch P (see FIGS. 4C and 4D). The lengths of the steps LST and ST along the optical axis direction are referred to as step amounts B1 and B2. In the case of a stepped structure having three or more steps, there is a large step amount B1 (kth step amount) and a small step amount B2 (see FIG. 4C). On the other hand, in the case of the two-step structure, basically B1 = B2.
　尚、回折溝は、ある単位形状が周期的に繰り返されている構造であることが好ましい。ここでいう「単位形状が周期的に繰り返されている」とは、同一の形状が同一の周期で繰り返されている形状は当然含む。さらに、周期の１単位となる単位形状が、規則性を持って、周期が徐々に長くなったり、徐々に短くなったりする形状も、「単位形状が周期的に繰り返されている」ものに含まれているとする。 The diffraction groove preferably has a structure in which a certain unit shape is periodically repeated. As used herein, “unit shape is periodically repeated” naturally includes shapes in which the same shape is repeated in the same cycle. In addition, the unit shape that is one unit of the cycle has regularity, and the shape in which the cycle gradually increases or decreases gradually is also included in the “unit shape is periodically repeated”. Suppose that
　又、１つの階段単位内に形成されるテラス面の幅は、１つの階段単位内で均等であっても良いし、非均等であっても良い。テラス面の幅を１つの階段単位内で非均等とすると、特定の次数の回折光の強度を強めたり、逆に弱めたりすることが出来るので、情報の記録／再生特性に影響を及ぼさないように、光検出器の受光面上での不要次数光（情報の記録／再生に使用する回折光の次数とは異なる次数の回折光を指す）の強度を調整することが可能となる。 In addition, the width of the terrace surface formed in one staircase unit may be uniform or non-uniform in one staircase unit. If the width of the terrace surface is not uniform within one step unit, the intensity of the diffracted light of a specific order can be increased or decreased, so that it does not affect the information recording / reproduction characteristics. In addition, it is possible to adjust the intensity of unnecessary-order light (which indicates a diffracted light having a different order from that of the diffracted light used for recording / reproducing information) on the light receiving surface of the photodetector.
　更に、１つの階段単位内に形成されるテラス面の幅を非均等とする場合は、金型で凹部となるテラス面の幅を他のテラス面よりも広くすることが好ましい。ここでいう金型で凹部とは、隣接する段差面が両側とも負であるテラス面を指す。このようにテラス面の幅を設定することで、先端幅の広い工具を用いて金型加工を行うことができ、１つの工具で複数の金型を加工することが可能となる。その結果、金型加工コストの低減につながる。 Furthermore, when making the width of the terrace surface formed in one staircase unit non-uniform, it is preferable to make the width of the terrace surface that becomes a recess in the mold wider than the other terrace surfaces. The concave portion in the mold here refers to a terrace surface in which adjacent step surfaces are negative on both sides. By setting the width of the terrace surface in this way, it is possible to perform mold processing using a tool having a wide tip width, and it is possible to process a plurality of molds with one tool. As a result, the die processing cost is reduced.
　回折溝が、ブレーズ型構造を有する場合、単位形状である鋸歯状の形状が繰り返された形状となる。図４（ａ）に示されるように、同一の鋸歯状形状が繰り返されてもよい。 When the diffractive groove has a blazed structure, the sawtooth shape as a unit shape is repeated. As shown in FIG. 4 (a), the same sawtooth shape may be repeated.
　回折溝が、階段型構造を有する場合、図４（ｃ）で示されるようなステップ単位が、繰り返されるような形状等があり得る。 When the diffraction groove has a stepped structure, there may be a shape such that the step unit as shown in FIG. 4C is repeated.
　尚、図５（ａ）に示す階段型構造の変形例の場合、テラス面ＴＲが光軸に対して傾いているが、この場合、段差量Ｂは、空気に接する側の交差角が１８０度以上である段差面ＳＴとテラス面ＴＲの交点間の光軸方向距離をいうものとする。又、図５（ｂ）に示す階段型構造の変形例の場合、テラス面ＴＲの奥に微小な段差が形成されているが、この場合も、段差量Ｂは、空気に接する側の交差角が１８０度以上である段差面ＳＴとテラス面ＴＲの交点間の光軸方向距離をいうものとする。尚、段差面ＳＴの光軸方向長さを微小に変えても良い。また、回折溝は、平行平板の光源側に設けても良いし、光検出器側に設けても良い。 In the modification of the staircase structure shown in FIG. 5A, the terrace surface TR is inclined with respect to the optical axis. In this case, the step amount B has an intersection angle of 180 degrees on the side in contact with air. The distance in the optical axis direction between the intersections of the step surface ST and the terrace surface TR is as described above. In the case of the modification of the staircase structure shown in FIG. 5B, a minute step is formed in the back of the terrace surface TR. In this case, the step amount B is the intersection angle on the side in contact with the air. Is the distance in the optical axis direction between the intersections of the step surface ST and the terrace surface TR that is 180 degrees or more. Note that the length of the step surface ST in the optical axis direction may be changed slightly. Further, the diffraction groove may be provided on the light source side of the parallel plate, or may be provided on the photodetector side.
　ここで、本発明の回折素子の回折次数の符号について説明する。 Here, the sign of the diffraction order of the diffraction element of the present invention will be described.
　（回折溝がブレーズ型構造の場合）
　図４（ａ）、（ｂ）に示すように、隣接する段差面同士を連結する斜面ＣＰが、左から右に向かって高くなるように配置した回折素子に対して、下方から光束が入射した場合に右方向に回折する回折光を正の回折次数、左方向に回折する回折光を負の回折次数とする。 (Diffraction groove has blazed structure)
As shown in FIGS. 4 (a) and 4 (b), a light beam is incident from below on a diffractive element arranged such that a slope CP connecting adjacent step surfaces increases from left to right. In this case, diffracted light that is diffracted in the right direction is a positive diffraction order, and diffracted light that is diffracted in the left direction is a negative diffraction order.
　（回折溝が階段型構造の場合）
　図４（ｃ）に示すように、一ステップ単位内でテラス面ＴＲが左から右に向かって順次高くなるように配置した回折素子に対して、下方から光束が入射した場合に右方向に回折する回折光を正の回折次数、左方向に回折する回折光を負の回折次数とする。 (When the diffraction groove has a stepped structure)
As shown in FIG. 4 (c), when a light beam is incident from below on a diffractive element arranged so that the terrace surface TR is gradually increased from left to right within one step unit, it is diffracted rightward. The diffracted light that is diffracted to the positive diffraction order and the diffracted light that is diffracted in the left direction is the negative diffraction order.
　尚、階段型構造が、図４（ｅ）に示すように、最も高い側から１又は２以上のテラスＴＲを等量だけ低める方向にシフトしてなる構造である場合は、テラスＴＲをシフトする前の基礎構造（図４（ｅ）において点線で示す構造を指す）の一ステップ単位内でテラス面ＴＲが左から右に向かって順次高くなるように配置された回折素子に対して、下方から光束が入射した場合に右方向に回折する回折光を正の回折次数、左方向に回折する回折光を負の回折次数とする。 If the staircase structure is a structure in which one or two or more terraces TR are shifted from the highest side in the direction of decreasing by an equal amount as shown in FIG. 4E, the terraces TR are shifted. With respect to the diffractive element arranged so that the terrace surface TR sequentially increases from left to right within one step unit of the previous basic structure (pointing to the structure indicated by the dotted line in FIG. 4E) from below. A diffracted light that is diffracted in the right direction when the light beam is incident is a positive diffraction order, and a diffracted light that is diffracted in the left direction is a negative diffraction order.
　光情報記録再生装置は、上述の回折素子を備えた光ピックアップ装置を有する光ディスクドライブ装置を有する。 The optical information recording / reproducing apparatus has an optical disc drive apparatus having an optical pickup device provided with the above-described diffraction element.
　ここで、光情報記録再生装置に装備される光ディスクドライブ装置に関して説明すると、光ディスクドライブ装置には、光ピックアップ装置等を収納している光情報記録再生装置本体から光ディスクを搭載した状態で保持可能なトレイのみが外部に取り出される方式と、光ピックアップ装置等が収納されている光ディスクドライブ装置本体ごと、外部に取り出される方式とがある。 Here, the optical disk drive apparatus provided in the optical information recording / reproducing apparatus will be described. The optical disk drive apparatus can hold an optical disk mounted from the optical information recording / reproducing apparatus main body containing the optical pickup apparatus or the like. There are a system in which only the tray is taken out, and a system in which the optical disc drive apparatus main body in which the optical pickup device is stored is taken out to the outside.
　上述した各方式を用いる光情報記録再生装置には、概ね、次の構成部材が装備されているがこれに限られるものではない。ハウジング等に収納された光ピックアップ装置、光ピックアップ装置をハウジングごと光ディスクの内周あるいは外周に向けて移動させるシークモータ等の光ピックアップ装置の駆動源、光ピックアップ装置のハウジングを光ディスクの内周あるいは外周に向けてガイドするガイドレールなどを有した光ピックアップ装置の移送手段及び、光ディスクの回転駆動を行うスピンドルモータ等である。 The optical information recording / reproducing apparatus using each method described above is generally equipped with the following components, but is not limited thereto. An optical pickup device housed in a housing or the like, a drive source of an optical pickup device such as a seek motor that moves the optical pickup device together with the housing toward the inner periphery or outer periphery of the optical disc, and the optical pickup device housing the inner periphery or outer periphery of the optical disc These include a transfer means of an optical pickup device having a guide rail or the like that guides toward the head, a spindle motor that rotates the optical disk, and the like.
　前者の方式には、これら各構成部材の他に、光ディスクを搭載した状態で保持可能なトレイおよびトレイを摺動させるためのローディング機構等が設けられ、後者の方式にはトレイおよびローディング機構がなく、各構成部材が外部に引き出し可能なシャーシに相当するドロワーに設けられていることが好ましい。 In addition to these components, the former method is provided with a tray that can be held in a state in which an optical disk is mounted and a loading mechanism for sliding the tray, and the latter method has no tray and loading mechanism. It is preferable that each component is provided in a drawer corresponding to a chassis that can be pulled out to the outside.
　本発明によれば、小型化を図りコストを抑えつつも、異なる３種類の光ディスクに対して適切に情報の記録／再生を行える光ピックアップ装置に用いる回折素子を提供することも可能となる。 According to the present invention, it is also possible to provide a diffractive element used for an optical pickup device capable of appropriately recording / reproducing information on three different types of optical discs while reducing the size and reducing the cost.
本発明の原理を示す図である。It is a figure which shows the principle of this invention. 発光部の間隔と、波長及び次数との関係を説明するための図である。It is a figure for demonstrating the relationship between the space | interval of a light emission part, a wavelength, and an order. １次元の回折構造を有する回折素子の斜視図である。It is a perspective view of the diffraction element which has a one-dimensional diffraction structure. 回折溝の例を示す軸線方向断面図である。It is an axial direction sectional view showing an example of a diffraction groove. 回折溝の変形例を示す軸線方向断面図である。It is an axial direction sectional view showing a modification of a diffraction groove. 異なる光ディスクであるＢＤとＤＶＤとＣＤに対して適切に情報の記録及び／又は再生を行うことができる本実施の形態の光ピックアップ装置ＰＵ１の構成を概略的に示す図である。It is a figure which shows schematically the structure of optical pick-up apparatus PU1 of this Embodiment which can record and / or reproduce | regenerate information appropriately with respect to BD, DVD, and CD which are different optical disks. 図６に示す光検出器ＰＤの受光面を矢印VII方向に見た図である。It is the figure which looked at the light-receiving surface of photodetector PD shown in FIG. 6 in the arrow VII direction. 回折素子ＤＥの位置と、光検出器ＰＤにおける各光束の受光位置との関係を示す概略図である。It is the schematic which shows the relationship between the position of the diffraction element DE, and the light-receiving position of each light beam in photodetector PD. 回折素子ＤＥを、光源ユニットＬＤＰと対物レンズＯＢＪとの間に配置した光ピックアップ装置の概略図である。It is the schematic of the optical pick-up apparatus which has arrange | positioned the diffraction element DE between light source unit LDP and the objective lens OBJ. 異なる光ディスクであるＢＤとＤＶＤとＣＤに対して適切に情報の記録及び／又は再生を行うことができる本実施の形態の光ピックアップ装置ＰＵ２の構成を概略的に示す図である。It is a figure which shows roughly the structure of optical pick-up apparatus PU2 of this Embodiment which can record and / or reproduce | regenerate information appropriately with respect to BD, DVD, and CD which are different optical disks. 実施例１の回折素子の断面図である。3 is a cross-sectional view of the diffraction element of Example 1. FIG. 実施例３の回折素子の波長特性を示す図である。FIG. 6 is a diagram showing the wavelength characteristics of the diffraction element of Example 3. 実施例４の回折素子の波長特性を示す図である。FIG. 6 is a diagram showing the wavelength characteristics of the diffraction element of Example 4. 実施例６の回折素子の断面図である。6 is a sectional view of a diffraction element according to Example 6. FIG. 実施例１６の回折素子の断面図であり、重畳により形成できるシフトした階段型の回折構造を示す。It is sectional drawing of the diffraction element of Example 16, and shows the shifted staircase type diffraction structure which can be formed by superimposition. 実施例１６の回折素子の波長特性を示す図である。FIG. 10 is a graph showing the wavelength characteristics of the diffraction element of Example 16. 実施例１７の回折素子の断面図であり、重畳により形成できるシフトした階段型の回折構造を示す。It is sectional drawing of the diffraction element of Example 17, and shows the shifted staircase type diffraction structure which can be formed by superimposition. 実施例１７の回折素子の波長特性を示す図である。FIG. 14 is a graph showing the wavelength characteristics of the diffraction element of Example 17.
　以下、本発明の実施の形態を、図面を参照して説明する。図６は、異なる光ディスクであるＢＤとＤＶＤとＣＤに対して適切に情報の記録及び／又は再生を行うことができる本実施の形態の光ピックアップ装置ＰＵ１の構成を概略的に示す図である。かかる光ピックアップ装置ＰＵ１は、光情報記録再生装置に搭載できる。図７は、図６に示す光検出器ＰＤの受光面を矢印VII方向に見た図であり、集光スポットをハッチングで示している。ここでは、第１光ディスクをＢＤとし、第２光ディスクをＤＶＤとし、第３光ディスクをＣＤとする。なお、本発明は、本実施の形態に限られるものではない。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 6 is a diagram schematically showing the configuration of the optical pickup device PU1 of the present embodiment that can appropriately record and / or reproduce information on BD, DVD, and CD, which are different optical disks. Such an optical pickup device PU1 can be mounted on an optical information recording / reproducing device. FIG. 7 is a view of the light receiving surface of the photodetector PD shown in FIG. 6 as viewed in the direction of the arrow VII, and the condensing spot is indicated by hatching. Here, the first optical disc is a BD, the second optical disc is a DVD, and the third optical disc is a CD. The present invention is not limited to the present embodiment.
　光ピックアップ装置ＰＵ１は、対物光学系としての単一の対物レンズＯＢＪ、λ／４波長板ＱＷＰ、コリメートレンズＣＯＬ、光束分離素子としての偏光ビームスプリッタＰＢＳ、ＢＤに対して情報の記録／再生を行う場合に発光され波長λ１＝４０５ｎｍのレーザ光束（第１光束）を射出する第１半導体レーザＬＤ１（第１発光部）と、ＤＶＤに対して情報の記録／再生を行う場合に発光され波長λ２＝６５５ｎｍのレーザ光束（第２光束）を射出する第２半導体レーザＬＤ２（第２発光部）と、ＣＤに対して情報の記録／再生を行う場合に発光され波長λ３＝７８５ｎｍのレーザ光束（第３光束）を射出する第３半導体レーザＬＤ３（第３発光部）を、１パッケージに収容して一体化した光源ユニットＬＤＰ、入射光束を３分割して出射するグレーティングＧＲＴ、センサレンズＳＮ、回折溝を有する回折素子ＤＥ、光検出器ＰＤ等を有する。尚、第２半導体レーザＬＤ２及び第３半導体レーザＬＤ３は同じチップに形成され、第１半導体レーザＬＤ１は、それとは異なるチップに形成されている。 The optical pickup device PU1 records / reproduces information to / from a single objective lens OBJ as an objective optical system, a λ / 4 wavelength plate QWP, a collimating lens COL, and a polarization beam splitter PBS and BD as light beam separation elements. The first semiconductor laser LD1 (first light emitting unit) that emits a laser beam having a wavelength λ1 = 405 nm (first light beam) and the light emitted when information is recorded / reproduced with respect to a DVD. A second semiconductor laser LD2 (second light emitting unit) that emits a laser beam (second beam) of 655 nm, and a laser beam (third beam) emitted when recording / reproducing information with respect to a CD, wavelength λ3 = 785 nm. A light source unit LDP in which a third semiconductor laser LD3 (third light emitting portion) emitting a light beam) is integrated in a single package; That grating GRT, sensor lens SN, the diffraction element DE having diffraction grooves have a photodetector PD, and the like. The second semiconductor laser LD2 and the third semiconductor laser LD3 are formed on the same chip, and the first semiconductor laser LD1 is formed on a different chip.
　図３に示すような形状の回折素子ＤＥは、第１光束が入射したときに最も光量が高い回折光として０次回折光を発生し、第２光束が入射したときに最も光量が高い回折光として１次回折光を発生し、第３光束が入射したときに最も光量が高い回折光として１次回折光を発生する回折溝を表面に形成している。又、回折素子ＤＥは、不図示のガイドにより光軸方向に移動可能に保持されている。 The diffractive element DE shaped as shown in FIG. 3 generates 0th-order diffracted light as the diffracted light with the highest light amount when the first light beam enters, and as the diffracted light with the highest light amount when the second light beam enters. A diffraction groove that generates first-order diffracted light and generates first-order diffracted light as the diffracted light having the highest light amount when the third light beam enters is formed on the surface. The diffraction element DE is held by a guide (not shown) so as to be movable in the optical axis direction.
　図７に示されるように、光検出器ＰＤは、光軸に略直交する受光面側に、３行３列に並んだ受光部１１Ｒ～３３Ｒを有する。受光部１１Ｒ～１３ＲはＢＤからの反射光を受光する第１受光部であり、受光部２１Ｒ～２３ＲはＤＶＤからの反射光を受光する第２受光部であり、受光部３１Ｒ～３３ＲはＣＤからの反射光を受光する第３受光部である。受光部１２Ｒは、上下左右に４分割され、その受光量に基づく信号をそれぞれ１ｅ、１ｃ、１ｆ、１ｄとする。又受光部１２Ｒの両側の受光部１１Ｒ、１３Ｒは、左右に２分割され、その受光量に基づく信号をそれぞれ１ｈ、１ｇ、及び１ｂ、１ａとする。受光部２２Ｒは、上下左右に４分割され、その受光量に基づく信号をそれぞれ２ｅ、２ｃ、２ｆ、２ｄとする。又受光部２２Ｒの両側の受光部２１Ｒ、２３Ｒは、左右に２分割され、その受光量に基づく信号をそれぞれ２ｈ、２ｇ、及び２ｂ、２ａとする。更に受光部３２Ｒは、上下左右に４分割され、その受光量に基づく信号をそれぞれ３ｅ、３ｃ、３ｆ、３ｄとする。又受光部３２Ｒの両側の受光部３１Ｒ、３３Ｒは、左右に２分割され、その受光量に基づく信号をそれぞれ３ｈ、３ｇ、及び３ｂ、３ａとする。 As shown in FIG. 7, the photodetector PD has light receiving portions 11R to 33R arranged in 3 rows and 3 columns on the light receiving surface side substantially orthogonal to the optical axis. The light receiving portions 11R to 13R are first light receiving portions that receive the reflected light from the BD, the light receiving portions 21R to 23R are second light receiving portions that receive the reflected light from the DVD, and the light receiving portions 31R to 33R are from the CD. It is the 3rd light-receiving part which receives the reflected light. The light receiving unit 12R is divided into four parts vertically and horizontally, and signals based on the amount of received light are 1e, 1c, 1f, and 1d, respectively. The light receiving parts 11R and 13R on both sides of the light receiving part 12R are divided into left and right parts, and signals based on the amount of light received are 1h, 1g, and 1b and 1a, respectively. The light receiving unit 22R is divided into four parts in the vertical and horizontal directions, and signals based on the amount of received light are 2e, 2c, 2f, and 2d, respectively. The light receiving parts 21R and 23R on both sides of the light receiving part 22R are divided into left and right parts, and signals based on the amount of light received are 2h, 2g, 2b and 2a, respectively. Furthermore, the light receiving unit 32R is divided into four parts, top, bottom, left, and right, and signals based on the amount of light received are 3e, 3c, 3f, and 3d, respectively. The light receiving parts 31R and 33R on both sides of the light receiving part 32R are divided into left and right parts, and the signals based on the amount of received light are 3h, 3g, and 3b and 3a, respectively.
　次に光ピックアップ装置ＰＵ１の動作について説明する。第１半導体レーザＬＤ１から射出された第１光束（λ１＝４０５ｎｍ）の発散光束は、実線で示すように、グレーティングＧＲＴを通過して３分割された後、偏光ビームスプリッタＰＢＳで反射され、コリメートレンズＣＯＬを通過して平行光となり、λ／４波長板ＱＷＰにより直線偏光から円偏光に変換され、不図示の絞りによりその光束径が規制され、更に対物レンズＯＢＪにより集光された光束は、厚さ０．１ｍｍの保護基板を介して、ＢＤの情報記録面上に形成されるスポットとなる。 Next, the operation of the optical pickup device PU1 will be described. The divergent light beam of the first light beam (λ1 = 405 nm) emitted from the first semiconductor laser LD1 passes through the grating GRT and is divided into three parts, as shown by the solid line, and then reflected by the polarization beam splitter PBS to be collimated lenses. The collimated light passes through the COL, is converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, the diameter of the light flux is regulated by a diaphragm (not shown), and the light flux condensed by the objective lens OBJ is thick. The spot is formed on the information recording surface of the BD through a protective substrate having a thickness of 0.1 mm.
　ＢＤの情報記録面上で情報ピットにより変調された反射光束は、再び対物レンズＯＢＪ、不図示の絞りを透過した後、λ／４波長板ＱＷＰにより円偏光から直線偏光に変換され、コリメートレンズＣＯＬにより収斂光束とされ、偏光ビームスプリッタＰＢＳ、センサレンズＳＮ及び回折素子ＤＥを通過して、３分割された光束がそれぞれ光検出器ＰＤの受光部１１Ｒ～１３Ｒ上に収束する。そして、光検出器ＰＤの出力信号を用いて、不図示の対物レンズ用アクチュエータにより対物レンズＯＢＪをフォーカシングやトラッキングさせることで、ＢＤに記録された情報を読み取ることができる。 The reflected light beam modulated by the information pits on the information recording surface of the BD again passes through the objective lens OBJ and a diaphragm (not shown), and then converted from circularly polarized light to linearly polarized light by the λ / 4 wavelength plate QWP, and collimated lens COL. As a result, the light beam is converged and passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams converge on the light receiving portions 11R to 13R of the photodetector PD, respectively. Then, the information recorded on the BD can be read by using the output signal of the photodetector PD to focus or track the objective lens OBJ by an objective lens actuator (not shown).
　より具体的には、ＢＤに対してフォーカスサーボが入った状態のフォーカスエラー（ＦＥ）信号、トラッキングエラー（ＴＥ）信号及び記録マーク再生信号（ＲＦ）を観察する。例として、フォーカスサーボは非点収差法が用いられ、ＦＥ信号は（１ｃ＋１ｆ）－（１ｅ＋１ｄ）によって得られるものであり、これがゼロに近づくように対物レンズ用アクチュエータにより対物レンズＯＢＪをフォーカシングさせる。 More specifically, a focus error (FE) signal, a tracking error (TE) signal, and a recording mark reproduction signal (RF) in a state where the focus servo is applied to the BD are observed. As an example, the astigmatism method is used for the focus servo, and the FE signal is obtained by (1c + 1f) − (1e + 1d), and the objective lens OBJ is focused by the objective lens actuator so that the FE signal approaches zero.
　一方、トラッキングサーボはＤＰＰ法を用いることとする。ＤＰＰ法において、ＴＥ信号は、（１ａ＋１ｇ＋１ｅ＋１ｆ）－（１ｂ＋１ｈ＋１ｃ＋１ｄ）によって得られるものであり、これがゼロに近づくように対物レンズ用アクチュエータにより対物レンズＯＢＪをトラッキングさせる。尚、ＲＦ信号は、各受光光量の総和であり、（１ａ＋１ｂ＋１ｃ＋１ｄ＋１ｅ＋１ｆ＋１ｇ＋１ｈ）で表される。 On the other hand, the tracking servo uses the DPP method. In the DPP method, the TE signal is obtained by (1a + 1g + 1e + 1f) − (1b + 1h + 1c + 1d), and the objective lens OBJ is tracked by the objective lens actuator so that this approaches zero. The RF signal is the sum of the amounts of received light, and is represented by (1a + 1b + 1c + 1d + 1e + 1f + 1g + 1h).
　次に、第２半導体レーザＬＤ２から射出された第２光束（λ２＝６５５ｎｍ）の発散光束は、一点鎖線で示すように、グレーティングＧＲＴを通過して３分割された後、偏光ビームスプリッタＰＢＳで反射され、コリメートレンズＣＯＬを通過して平行光となり、λ／４波長板ＱＷＰにより直線偏光から円偏光に変換され、不図示の絞りによりその光束径が規制され、更に対物レンズＯＢＪにより集光された光束は、厚さ０．６ｍｍの保護基板を介して、ＤＶＤの情報記録面上に形成されるスポットとなる。 Next, the divergent light beam of the second light beam (λ2 = 655 nm) emitted from the second semiconductor laser LD2 passes through the grating GRT and is divided into three parts as shown by the one-dot chain line, and then reflected by the polarization beam splitter PBS. Then, the light passes through the collimating lens COL, becomes parallel light, is converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, the diameter of the light beam is regulated by a diaphragm (not shown), and further condensed by the objective lens OBJ. The light beam becomes a spot formed on the information recording surface of the DVD through a protective substrate having a thickness of 0.6 mm.
　ＤＶＤの情報記録面上で情報ピットにより変調された反射光束は、再び対物レンズＯＢＪ、不図示の絞りを透過した後、λ／４波長板ＱＷＰにより円偏光から直線偏光に変換され、コリメートレンズＣＯＬにより収斂光束とされ、偏光ビームスプリッタＰＢＳ、センサレンズＳＮ及び回折素子ＤＥを通過して、３分割された光束がそれぞれ光検出器ＰＤの受光部２１Ｒ～２３Ｒ上に収束する。そして、光検出器ＰＤの出力信号を用いて、不図示の対物レンズ用アクチュエータにより対物レンズＯＢＪをフォーカシングやトラッキングさせることで、ＤＶＤに記録された情報を読み取ることができる。 The reflected light beam modulated by the information pits on the information recording surface of the DVD is again transmitted through the objective lens OBJ and a diaphragm (not shown), and then converted from circularly polarized light to linearly polarized light by the λ / 4 wavelength plate QWP, and collimated lens COL. Thus, the light beam is converged and passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams are converged on the light receiving portions 21R to 23R of the photodetector PD, respectively. Then, using the output signal of the photodetector PD, the objective lens OBJ is focused and tracked by an unillustrated objective lens actuator, whereby the information recorded on the DVD can be read.
　より具体的には、ＤＶＤに対してフォーカスサーボが入った状態のフォーカスエラー（ＦＥ）信号、トラッキングエラー（ＴＥ）信号及び記録マーク再生信号（ＲＦ）を観察する。例として、フォーカスサーボは非点収差法が用いられ、ＦＥ信号は（２ｃ＋２ｆ）－（２ｅ＋２ｄ）によって得られるものであり、これがゼロに近づくように対物レンズ用アクチュエータにより対物レンズＯＢＪをフォーカシングさせる。 More specifically, a focus error (FE) signal, a tracking error (TE) signal, and a recording mark reproduction signal (RF) in a state where the focus servo is applied to the DVD are observed. As an example, the astigmatism method is used for the focus servo, and the FE signal is obtained by (2c + 2f) − (2e + 2d), and the objective lens OBJ is focused by the objective lens actuator so that this becomes close to zero.
　一方、トラッキングサーボはＤＰＰ法を用いることとする。ＤＰＰ法において、ＴＥ信号は、（２ａ＋２ｇ＋２ｅ＋２ｆ）－（２ｂ＋２ｈ＋２ｃ＋２ｄ）によって得られるものであり、これがゼロに近づくように対物レンズ用アクチュエータにより対物レンズＯＢＪをトラッキングさせる。尚、ＲＦ信号は、各受光光量の総和であり、（２ａ＋２ｂ＋２ｃ＋２ｄ＋２ｅ＋２ｆ＋２ｇ＋２ｈ）で表される。 On the other hand, the tracking servo uses the DPP method. In the DPP method, the TE signal is obtained by (2a + 2g + 2e + 2f) − (2b + 2h + 2c + 2d), and the objective lens OBJ is tracked by the objective lens actuator so that the TE signal approaches zero. The RF signal is the sum of the amounts of received light, and is represented by (2a + 2b + 2c + 2d + 2e + 2f + 2g + 2h).
　次に、第３半導体レーザＬＤ３から射出された第３光束（λ３＝７８５ｎｍ）の発散光束は、点線で示すように、グレーティングＧＲＴを通過して３分割された後、偏光ビームスプリッタＰＢＳで反射され、コリメートレンズＣＯＬを通過して平行光となり、λ／４波長板ＱＷＰにより直線偏光から円偏光に変換され、不図示の絞りによりその光束径が規制され、更に対物レンズＯＢＪにより集光された光束は、厚さ１．２ｍｍの保護基板を介して、ＣＤの情報記録面上に形成されるスポットとなる。 Next, the divergent light beam of the third light beam (λ3 = 785 nm) emitted from the third semiconductor laser LD3 passes through the grating GRT and is divided into three as shown by the dotted line, and then reflected by the polarization beam splitter PBS. The light beam passes through the collimating lens COL, becomes parallel light, is converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, the diameter of the light beam is regulated by a diaphragm (not shown), and the light beam collected by the objective lens OBJ. Are spots formed on the information recording surface of the CD via a protective substrate having a thickness of 1.2 mm.
　ＣＤの情報記録面上で情報ピットにより変調された反射光束は、再び対物レンズＯＢＪ、不図示の絞りを透過した後、λ／４波長板ＱＷＰにより円偏光から直線偏光に変換され、コリメートレンズＣＯＬにより収斂光束とされ、偏光ビームスプリッタＰＢＳ、センサレンズＳＮ及び回折素子ＤＥを通過して、３分割された光束がそれぞれ光検出器ＰＤの受光部３１Ｒ～３３Ｒ上に収束する。そして、光検出器ＰＤの出力信号を用いて、不図示の対物レンズ用アクチュエータにより対物レンズＯＢＪをフォーカシングやトラッキングさせることで、ＣＤに記録された情報を読み取ることができる。 The reflected light beam modulated by the information pits on the information recording surface of the CD is again transmitted through the objective lens OBJ and a diaphragm (not shown), and then converted from circularly polarized light to linearly polarized light by the λ / 4 wavelength plate QWP, and collimated lens COL. Thus, the light beam is converged and passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams are converged on the light receiving portions 31R to 33R of the photodetector PD, respectively. Then, using the output signal of the photodetector PD, the objective lens OBJ is focused or tracked by an unillustrated objective lens actuator, whereby the information recorded on the CD can be read.
　より具体的には、ＣＤに対してフォーカスサーボが入った状態のフォーカスエラー（ＦＥ）信号、トラッキングエラー（ＴＥ）信号及び記録マーク再生信号（ＲＦ）を観察する。例として、フォーカスサーボは非点収差法が用いられ、ＦＥ信号は（３ｃ＋３ｆ）－（３ｅ＋３ｄ）によって得られるものであり、これがゼロに近づくように対物レンズ用アクチュエータにより対物レンズＯＢＪをフォーカシングさせる。 More specifically, a focus error (FE) signal, a tracking error (TE) signal, and a recording mark reproduction signal (RF) in a state where the focus servo is applied to the CD are observed. As an example, the astigmatism method is used for the focus servo, and the FE signal is obtained by (3c + 3f) − (3e + 3d), and the objective lens OBJ is focused by the objective lens actuator so that this becomes close to zero.
　一方、トラッキングサーボはＤＰＰ法を用いることとする。ＤＰＰ法において、ＴＥ信号は、（３ａ＋３ｇ＋３ｅ＋３ｆ）－（３ｂ＋３ｈ＋３ｃ＋３ｄ）によって得られるものであり、これがゼロに近づくように対物レンズ用アクチュエータにより対物レンズＯＢＪをトラッキングさせる。尚、ＲＦ信号は、各受光光量の総和であり、（３ａ＋３ｂ＋３ｃ＋３ｄ＋３ｅ＋３ｆ＋３ｇ＋３ｈ）で表される。 On the other hand, the tracking servo uses the DPP method. In the DPP method, the TE signal is obtained by (3a + 3g + 3e + 3f) − (3b + 3h + 3c + 3d), and the objective lens OBJ is tracked by the objective lens actuator so that the TE signal approaches zero. The RF signal is the sum of the amounts of received light, and is represented by (3a + 3b + 3c + 3d + 3e + 3f + 3g + 3h).
　ところで、上述したように第２半導体レーザＬＤ２及び第３半導体レーザＬＤ３は同じチップに形成され、第１半導体レーザＬＤ１は、それとは異なるチップに形成されているので、光源ユニットＬＤＰに組み付ける際に、第１半導体レーザＬＤ１と、第２半導体レーザＬＤ２及び第３半導体レーザＬＤ３との間隔にバラツキが生じる。一方、光検出器ＰＤの受光部１１Ｒ～３３Ｒは、相対位置をずらすことができない。従って、半導体レーザの間隔が許容誤差を超えると、各光束を受光部１１Ｒ～３３Ｒに適切に受光させることができなくなる。そこで、本実施の形態では、以下のようにして、かかる問題を解決している。 By the way, as described above, the second semiconductor laser LD2 and the third semiconductor laser LD3 are formed on the same chip, and the first semiconductor laser LD1 is formed on a different chip. Therefore, when assembled to the light source unit LDP, There is a variation in the distance between the first semiconductor laser LD1, the second semiconductor laser LD2, and the third semiconductor laser LD3. On the other hand, the relative positions of the light receiving portions 11R to 33R of the photodetector PD cannot be shifted. Therefore, when the interval between the semiconductor lasers exceeds the allowable error, it becomes impossible to appropriately receive the light beams by the light receiving portions 11R to 33R. Therefore, in the present embodiment, such a problem is solved as follows.
　図８は、回折素子ＤＥの位置と、光検出器ＰＤにおける各光束の受光位置との関係を示す概略図であるが、理解しやすいように各光束は線で示しており、光検出器の受光部は中央のみ（１２Ｒ～３２Ｒ）示している。例えば、図８（ａ）に示す状態では、第１半導体レーザと第２半導体レーザとの間隔及び第１半導体レーザと第３半導体レーザとの間隔が基準値より大きく、回折素子ＤＥを通過した第１光束の０次回折光（ハッチング円で示すスポットλ１）が、それぞれ受光部１２Ｒの中央に位置するように光学系をセットすると、第２光束と第３光束の１次回折光（ハッチング円で示すスポットλ２、λ３）が受光部２２Ｒ、３２Ｒの下方に集光してしまい、不適切な信号が出力される恐れがある。 FIG. 8 is a schematic diagram showing the relationship between the position of the diffraction element DE and the light receiving position of each light beam in the photodetector PD. For ease of understanding, each light beam is shown by a line. The light receiving part is shown only at the center (12R to 32R). For example, in the state shown in FIG. 8A, the distance between the first semiconductor laser and the second semiconductor laser and the distance between the first semiconductor laser and the third semiconductor laser are larger than the reference value and pass through the diffraction element DE. When the optical system is set so that one-beam zero-order diffracted light (spot λ1 indicated by a hatched circle) is positioned at the center of the light receiving portion 12R, the first-order diffracted light (spots indicated by the hatched circle) of the second and third light beams. (λ2, λ3) may be condensed below the light receiving portions 22R and 32R, and an inappropriate signal may be output.
　かかる場合、図８（ｂ）に示すように、回折素子ＤＥを光検出器ＰＤに接近させるように移動させると、回折素子ＤＥを通過した第１光束の０次回折光の光路は変わらないのに対し、第２光束と第３光束の１次回折光は、それぞれ受光部２２Ｒ、３２Ｒの中央に近づくようになる。即ち、回折素子ＤＥを光検出器ＰＤに対して相対的に移動することで、全ての光束をそれぞれ受光部に適切に集光することができるのである。尚、第２光束と第３光束の１次回折光が受光部２２Ｒ、３２Ｒの上方に集光してしまう場合には、回折素子ＤＥを光検出器ＰＤから離間させるように移動させればよい。 In this case, as shown in FIG. 8B, when the diffraction element DE is moved so as to approach the photodetector PD, the optical path of the 0th-order diffracted light of the first light beam that has passed through the diffraction element DE does not change. On the other hand, the first-order diffracted lights of the second light beam and the third light beam come closer to the centers of the light receiving portions 22R and 32R, respectively. That is, by moving the diffractive element DE relative to the photodetector PD, all the light beams can be appropriately condensed on the light receiving part. When the first-order diffracted light of the second light beam and the third light beam is condensed above the light receiving portions 22R and 32R, the diffractive element DE may be moved away from the photodetector PD.
　図９は、回折素子ＤＥを、別な位置として光源ユニットＬＤＰと対物レンズＯＢＪとの間に配置した光ピックアップ装置の概略図であるが、一部の素子を省略しており、理解しやすいように各光束は線で示している。本変形例でも、回折素子ＤＥを光軸方向に移動させたとき、光検出器ＰＤの受光面上における、回折素子ＤＥを通過した第１光束の０次回折光の集光位置は変わらないのに対し、第２光束と第３光束の１次回折光の集光位置は変化するため、回折素子ＤＥの光軸方向位置を調整することで、全ての回折光を適切な位置に集光することができる。 FIG. 9 is a schematic view of an optical pickup device in which the diffractive element DE is disposed between the light source unit LDP and the objective lens OBJ as another position, but some elements are omitted so that it can be easily understood. Each light beam is indicated by a line. Even in this modification, when the diffraction element DE is moved in the optical axis direction, the condensing position of the 0th-order diffracted light of the first light beam that has passed through the diffraction element DE on the light receiving surface of the photodetector PD is not changed. On the other hand, since the condensing position of the first-order diffracted light of the second light flux and the third light flux changes, it is possible to collect all the diffracted light at an appropriate position by adjusting the position of the diffractive element DE in the optical axis direction. it can.
　図１０は、異なる光ディスクであるＢＤとＤＶＤとＣＤに対して適切に情報の記録及び／又は再生を行うことができる本実施の形態の光ピックアップ装置ＰＵ２の構成を概略的に示す図である。かかる光ピックアップ装置ＰＵ２は、光情報記録再生装置に搭載できる。ここでは、第１光ディスクをＢＤとし、第２光ディスクをＤＶＤとし、第３光ディスクをＣＤとする。なお、本実施の形態は、上述した実施の液体に対し異なる点のみを説明し、共通する構成については同じ符号を付すことで説明を省略する。 FIG. 10 is a diagram schematically showing a configuration of the optical pickup device PU2 of the present embodiment capable of appropriately recording and / or reproducing information on BD, DVD, and CD which are different optical disks. Such an optical pickup device PU2 can be mounted on an optical information recording / reproducing device. Here, the first optical disc is a BD, the second optical disc is a DVD, and the third optical disc is a CD. In the present embodiment, only different points from the above-described liquid will be described, and the common components will be denoted by the same reference numerals and description thereof will be omitted.
　本実施の形態の光ピックアップ装置ＰＵ２は、対物光学系として、第１対物レンズＯＢＪ１と第２対物レンズＯＢＪ２とを有する。第１対物レンズＯＢＪ１と第２対物レンズＯＢＪ２とは、ホルダＨＤにより保持されており、不図示のアクチュエータにより、いずれか一方を光ピックアップ装置の光路内に挿入できるようになっている。第１対物レンズＯＢＪ１は、第１光束専用設計とされ、第２対物レンズＯＢＪ２は、第２光束及び第３光束共用設計とされている。 The optical pickup device PU2 of the present embodiment includes a first objective lens OBJ1 and a second objective lens OBJ2 as objective optical systems. The first objective lens OBJ1 and the second objective lens OBJ2 are held by a holder HD, and either one can be inserted into the optical path of the optical pickup device by an actuator (not shown). The first objective lens OBJ1 is designed exclusively for the first light beam, and the second objective lens OBJ2 is designed to share the second light beam and the third light beam.
　次に光ピックアップ装置ＰＵ２の動作について説明する。ＢＤ使用時には、第１対物レンズＯＢＪ１が光ピックアップ装置の光路内に挿入される。第１半導体レーザＬＤ１から射出された第１光束（λ１＝４０５ｎｍ）の発散光束は、実線で示すように、グレーティングＧＲＴを通過して３分割された後、偏光ビームスプリッタＰＢＳで反射され、コリメートレンズＣＯＬを通過して平行光となり、λ／４波長板ＱＷＰにより直線偏光から円偏光に変換され、不図示の絞りによりその光束径が規制され、更に第１対物レンズＯＢＪ１により集光された光束は、厚さ０．１ｍｍの保護基板を介して、ＢＤの情報記録面上に形成されるスポットとなる。 Next, the operation of the optical pickup device PU2 will be described. When the BD is used, the first objective lens OBJ1 is inserted into the optical path of the optical pickup device. The divergent light beam of the first light beam (λ1 = 405 nm) emitted from the first semiconductor laser LD1 passes through the grating GRT and is divided into three parts, as shown by the solid line, and then reflected by the polarization beam splitter PBS to be collimated lenses. The collimated light passes through the COL, is converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, the diameter of the light flux is regulated by a stop (not shown), and the light flux collected by the first objective lens OBJ1 is The spots are formed on the information recording surface of the BD through a protective substrate having a thickness of 0.1 mm.
　ＢＤの情報記録面上で情報ピットにより変調された反射光束は、再び第１対物レンズＯＢＪ１、不図示の絞りを透過した後、λ／４波長板ＱＷＰにより円偏光から直線偏光に変換され、コリメートレンズＣＯＬにより収斂光束とされ、偏光ビームスプリッタＰＢＳ、センサレンズＳＮ及び回折素子ＤＥを通過して、３分割された光束がそれぞれ光検出器ＰＤの受光部１１Ｒ～１３Ｒ上に収束する。そして、光検出器ＰＤの出力信号を用いて、不図示の対物レンズ用アクチュエータにより第１対物レンズＯＢＪ１をフォーカシングやトラッキングさせることで、ＢＤに記録された情報を読み取ることができる。 The reflected light beam modulated by the information pits on the information recording surface of the BD again passes through the first objective lens OBJ1 and a diaphragm (not shown), and then converted from circularly polarized light to linearly polarized light by the λ / 4 wavelength plate QWP, and collimated. A converged light beam is formed by the lens COL, passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams converge on the light receiving portions 11R to 13R of the photodetector PD, respectively. Then, the information recorded on the BD can be read by using the output signal of the photodetector PD to focus or track the first objective lens OBJ1 by an objective lens actuator (not shown).
　次に、ＤＶＤ使用時には、第２対物レンズＯＢＪ２が光ピックアップ装置の光路内に挿入される。第２半導体レーザＬＤ２から射出された第２光束（λ２＝６５５ｎｍ）の発散光束は、一点鎖線で示すように、グレーティングＧＲＴを通過して３分割された後、偏光ビームスプリッタＰＢＳで反射され、コリメートレンズＣＯＬを通過して平行光となり、λ／４波長板ＱＷＰにより直線偏光から円偏光に変換され、不図示の絞りによりその光束径が規制され、更に第２対物レンズＯＢＪ２により集光された光束は、厚さ０．６ｍｍの保護基板を介して、ＤＶＤの情報記録面上に形成されるスポットとなる。 Next, when the DVD is used, the second objective lens OBJ2 is inserted into the optical path of the optical pickup device. The divergent light beam of the second light beam (λ2 = 655 nm) emitted from the second semiconductor laser LD2 passes through the grating GRT and is divided into three, as shown by the alternate long and short dash line, and then reflected by the polarization beam splitter PBS and collimated. A light beam that passes through the lens COL and becomes parallel light, is converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, the diameter of the light beam is regulated by a diaphragm (not shown), and is collected by the second objective lens OBJ2. Are spots formed on the information recording surface of the DVD through a protective substrate having a thickness of 0.6 mm.
　ＤＶＤの情報記録面上で情報ピットにより変調された反射光束は、再び第２対物レンズＯＢＪ２、不図示の絞りを透過した後、λ／４波長板ＱＷＰにより円偏光から直線偏光に変換され、コリメートレンズＣＯＬにより収斂光束とされ、偏光ビームスプリッタＰＢＳ、センサレンズＳＮ及び回折素子ＤＥを通過して、３分割された光束がそれぞれ光検出器ＰＤの受光部２１Ｒ～２３Ｒ上に収束する。そして、光検出器ＰＤの出力信号を用いて、不図示の対物レンズ用アクチュエータにより第２対物レンズＯＢＪ２をフォーカシングやトラッキングさせることで、ＤＶＤに記録された情報を読み取ることができる。 The reflected light beam modulated by the information pits on the information recording surface of the DVD is again transmitted through the second objective lens OBJ2 and the stop (not shown), and then converted from circularly polarized light to linearly polarized light by the λ / 4 wavelength plate QWP, and collimated. The light beam converged by the lens COL, passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams converge on the light receiving portions 21R to 23R of the photodetector PD, respectively. Then, by using the output signal of the photodetector PD to focus or track the second objective lens OBJ2 by an objective lens actuator (not shown), information recorded on the DVD can be read.
　次に、ＣＤ使用時には、第２対物レンズＯＢＪ２が光ピックアップ装置の光路内に挿入される。第３半導体レーザＬＤ３から射出された第３光束（λ３＝７８５ｎｍ）の発散光束は、点線で示すように、グレーティングＧＲＴを通過して３分割された後、偏光ビームスプリッタＰＢＳで反射され、コリメートレンズＣＯＬを通過して平行光となり、λ／４波長板ＱＷＰにより直線偏光から円偏光に変換され、不図示の絞りによりその光束径が規制され、更に第２対物レンズＯＢＪ２により集光された光束は、厚さ１．２ｍｍの保護基板を介して、ＣＤの情報記録面上に形成されるスポットとなる。 Next, when the CD is used, the second objective lens OBJ2 is inserted into the optical path of the optical pickup device. A divergent light beam of the third light beam (λ3 = 785 nm) emitted from the third semiconductor laser LD3 passes through the grating GRT and is divided into three parts as shown by a dotted line, and then is reflected by the polarization beam splitter PBS to be collimated lens. The collimated light passes through the COL, is converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, the diameter of the light flux is regulated by a diaphragm (not shown), and the light flux collected by the second objective lens OBJ2 is The spots are formed on the information recording surface of the CD through a protective substrate having a thickness of 1.2 mm.
　ＣＤの情報記録面上で情報ピットにより変調された反射光束は、再び第２対物レンズＯＢＪ２、不図示の絞りを透過した後、λ／４波長板ＱＷＰにより円偏光から直線偏光に変換され、コリメートレンズＣＯＬにより収斂光束とされ、偏光ビームスプリッタＰＢＳ、センサレンズＳＮ及び回折素子ＤＥを通過して、３分割された光束がそれぞれ光検出器ＰＤの受光部３１Ｒ～３３Ｒ上に収束する。そして、光検出器ＰＤの出力信号を用いて、不図示の対物レンズ用アクチュエータにより第２対物レンズＯＢＪ２をフォーカシングやトラッキングさせることで、ＣＤに記録された情報を読み取ることができる。 The reflected light beam modulated by the information pits on the information recording surface of the CD is again transmitted through the second objective lens OBJ2 and the stop (not shown), and then converted from circularly polarized light to linearly polarized light by the λ / 4 wavelength plate QWP. A converged light beam is formed by the lens COL, passes through the polarization beam splitter PBS, the sensor lens SN, and the diffraction element DE, and the three divided light beams converge on the light receiving portions 31R to 33R of the photodetector PD, respectively. The information recorded on the CD can be read by using the output signal of the photodetector PD to focus or track the second objective lens OBJ2 by an objective lens actuator (not shown).
　このように、第１対物レンズＯＢＪ１を、第１光束専用設計とし、第２対物レンズＯＢＪ２を、第２光束及び第３光束共用設計とすれば、回折素子ＤＥにおける回折効率が第３光束について低下するような場合でも、光検出器ＰＤの最低限の受光量を確保することができる。尚、第１対物レンズＯＢＪ１を、第１光束及び第２光束共用設計とし、第２対物レンズＯＢＪ２を、第３光束専用設計としても良い。 As described above, when the first objective lens OBJ1 is designed exclusively for the first light flux and the second objective lens OBJ2 is designed to share the second light flux and the third light flux, the diffraction efficiency in the diffraction element DE decreases for the third light flux. Even in such a case, the minimum amount of light received by the photodetector PD can be ensured. The first objective lens OBJ1 may be designed to share the first light flux and the second light flux, and the second objective lens OBJ2 may be designed exclusively for the third light flux.
　上述した第１の実施の形態及び第２の実施の形態では、回折素子ＤＥを、偏光ビームスプリッタＰＢＳと光検出器ＰＤの間の光路中に配置する構成としたが、光源ユニットＬＤＰと偏光ビームスプリッタＰＢＳの間の光路中に配置しても良い。また、回折素子ＤＥを他の光学素子と一体化してもよい。例えば、センサレンズＳＮの何れかの光学面上に回折溝を形成したり、グレーティングＧＲＴの何れかの光学面上に回折溝を形成したりすることで部品点数を削減することが可能となる。 In the first embodiment and the second embodiment described above, the diffraction element DE is arranged in the optical path between the polarization beam splitter PBS and the photodetector PD. However, the light source unit LDP and the polarization beam are arranged. You may arrange | position in the optical path between splitter PBS. Further, the diffraction element DE may be integrated with another optical element. For example, the number of parts can be reduced by forming a diffraction groove on any optical surface of the sensor lens SN or forming a diffraction groove on any optical surface of the grating GRT.
　以下、上述した実施の形態に用いることができる実施例について説明する。尚、以下の表の数値において、回折次数の符号は、実施例の断面図において、水平な光軸に沿って入射した光束が、下方に向かう場合を＋とし、上方に向かう場合を－とする。また、段差量ｄｉの符号は、実施例の断面図において、上方に隣接するテラス面より右側に向かう方向を＋とし、上方に隣接するテラス面より左側に向かう方向を－とする。また、ブレーズ高さｈの符号は、実施例の断面図において、上方に隣接する斜面より右側に向かう方向を＋とし、上方に隣接する斜面より左側に向かう方向を－とする。実施例の断面図において、段差量ｄｉ、及び、ブレーズ高さｈの数値の後ろに記載されている符号は、上述したように段差量ｄｉ、及び、ブレーズ高さｈの符号を表す。 Hereinafter, examples that can be used in the above-described embodiment will be described. In the numerical values in the table below, the sign of the diffraction order is defined as + when the light beam incident along the horizontal optical axis is directed downward and − when it is directed upward in the sectional view of the embodiment. . In addition, in the cross-sectional view of the embodiment, the sign of the step amount di is defined as + in the direction toward the right side from the terrace surface adjacent to the upper side and − as defined in the direction toward the left side from the terrace surface adjacent to the upper side. In addition, in the cross-sectional view of the embodiment, the sign of the blaze height h is defined as + for the direction toward the right side from the slope adjacent to the upper side, and − for the direction toward the left side from the slope adjacent to the upper side. In the cross-sectional view of the embodiment, the reference numerals described after the numerical values of the step amount di and the blaze height h represent the step amount di and the sign of the blaze height h as described above.
　（実施例１）
　実施例１は、テラス面が３つある３ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表１に示す。図１１は、実施例１の回折素子の光軸方向断面図である。実施例１の階段型構造は、素材のアッベ数が５６であり、第１、２番目の段差面の段差量＝０．８３１μｍであり、第３番目の段差面の段差量＝－１．６６３μｍである。 Example 1
Example 1 is a diffractive element provided with a diffractive groove formed by periodically repeating a three-step staircase structure with three terrace surfaces as one step unit, and its shape data is shown in Table 1. FIG. 11 is a cross-sectional view in the optical axis direction of the diffraction element according to the first embodiment. In the staircase structure of Example 1, the Abbe number of the material is 56, the step amount of the first and second step surfaces is 0.831 μm, and the step amount of the third step surface is −1.663 μm. It is.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　ここで、実施例１の階段型構造を通過した光束の波面について説明する。階段型構造を通過した波長λ１＝４０５ｎｍの第１光束の平均波面の進行方向は、入射光の進行方向と同じ方向となる。このとき、段差量＝０．８３１μｍで光軸に沿ってシフトした隣接するテラス面を通過した波面は、それぞれ＋０．１５０×λ１波長ずつずれてゆき、任意のステップ単位内の第ｊ番目の段差と、それに隣接するステップ単位内の第ｊ番目の段差を通過した光束の波面同士の位相のズレは、殆ど無いため（ΣΦ１ｊ＝０）、階段型構造を通過した第１光束は回折作用を受けずにそのまま通過する（このような光束を０次回折光とよぶ）。 Here, the wavefront of the light beam that has passed through the stepped structure of Example 1 will be described. The traveling direction of the average wavefront of the first light flux having the wavelength λ1 = 405 nm that has passed through the stepped structure is the same as the traveling direction of the incident light. At this time, the wavefronts that have passed through the adjacent terrace surfaces shifted along the optical axis with a step amount of 0.831 μm are shifted by + 0.150 × λ1 wavelength, respectively, and the jth step in an arbitrary step unit And there is almost no phase shift between the wavefronts of the light beams that have passed through the j-th step in the adjacent step unit (ΣΦ1j = 0). The light passes through as it is (this light beam is called zero-order diffracted light).
　一方、実施例１の階段型構造を通過した波長λ２＝６５５ｎｍの第２光束の平均波面の進行方向は、入射光の進行方向に対して変化することとなる。このとき、段差量＝０．８３１μｍで光軸に沿ってシフトした隣接するテラス面を通過した波面は、それぞれ－０．３１４×λ２波長ずつずれてゆき、任意のステップ単位内の第ｊ番目の段差と、それに隣接するステップ単位内の第ｊ番目の段差を通過した光束の波面同士では、－１×λ２波長ずれることとなるため（ΣΦ２ｊ＝－１）、階段型構造を通過した第２光束の回折次数は－１次となる。 On the other hand, the traveling direction of the average wavefront of the second light flux having the wavelength λ2 = 655 nm that has passed through the stepped structure of Example 1 changes with respect to the traveling direction of the incident light. At this time, the wavefronts that have passed through the adjacent terrace surfaces shifted along the optical axis with a step amount of 0.831 μm are shifted by −0.314 × λ2 wavelengths, respectively, and the j-th in any step unit. Since the wavefronts of the light fluxes that have passed through the step and the jth step in the step unit adjacent to the step are shifted by −1 × λ2 wavelength (ΣΦ2j = −1), the second light flux that has passed through the stepped structure The diffraction order is −1.
　同様に、実施例１の階段型構造を通過した波長λ３＝７８５ｎｍの第３光束の平均波面の進行方向は、入射光の進行方向に対して変化することとなる。このとき、段差量＝０．８３１μｍで光軸に沿ってシフトした隣接するテラス面を通過した波面は、それぞれ－０．４３１×λ３波長ずつずれてゆき、任意のステップ単位内の第ｊ番目の段差と、それに隣接するステップ単位内の第ｊ番目の段差を通過した光束の波面同士では、－１×λ３波長ずれることとなるため（ΣΦ３ｊ＝－１）、階段型構造を通過した第３光束の回折次数は－１次となる。実施例１では、第１光束の０次回折光の回折効率は５２．６％、第２光束の－１次回折光の回折効率は６７．７％、第３光束の－１次回折光の回折効率は５２．８％である。 Similarly, the traveling direction of the average wavefront of the third light flux having the wavelength λ3 = 785 nm that has passed through the stepped structure of the first embodiment changes with respect to the traveling direction of the incident light. At this time, the wavefronts that have passed through the adjacent terrace surfaces shifted along the optical axis with a step amount of 0.831 μm are shifted by −0.431 × λ3 wavelengths, respectively, and the j-th in any step unit. Since the wavefronts of the light fluxes that have passed through the step and the jth step in the step unit adjacent to the step are shifted by −1 × λ3 wavelength (ΣΦ3j = −1), the third light flux that has passed through the stepped structure The diffraction order is −1. In Example 1, the diffraction efficiency of the first-order diffracted light of the first light flux is 52.6%, the diffraction efficiency of the -1st-order diffracted light of the second light flux is 67.7%, and the diffraction efficiency of the -1st-order diffracted light of the third light flux is 52.8%.
　（実施例２）
　実施例２は、テラス面が３つある３ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表２に示す。実施例２の階段型構造は、素材のアッベ数が５６であり、第１、２番目の段差面の段差量＝６．４３５μｍであり、第３番目の段差面の段差量＝－１２．８７０μｍである。実施例２の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は７６．２％であり、また第２光束が入射したときは出射光において＋１次回折光の強度が最も高くなり、その回折効率は６７．６％であり、更に第３光束が入射したときは出射光において＋１次回折光の強度が最も高くなり、その回折効率は５９．８％である。 (Example 2)
Example 2 is a diffractive element provided with a diffractive groove formed by periodically repeating a three-step staircase structure having three terrace surfaces as one step unit. Table 2 shows the shape data thereof. In the staircase structure of Example 2, the Abbe number of the material is 56, the step amount of the first and second step surfaces = 6.435 μm, and the step amount of the third step surface = −12.870 μm. It is. When the first light beam is incident on the diffractive element of Example 2, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 76.2%, and when the second light beam is incident, it is emitted. The intensity of the + 1st order diffracted light is the highest in the incident light, and its diffraction efficiency is 67.6%. Further, when the third light beam is incident, the intensity of the + 1st order diffracted light is the highest in the emitted light, and the diffraction efficiency is 59. 8%.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　（実施例３）
　実施例３は、テラス面が５つある５ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表３に示す。実施例３の階段型構造は、素材のアッベ数が５６であり、第１～４番目の段差面の段差量＝５．０２５μｍであり、第５番目の段差面の段差量＝－２０．２０１μｍである。実施例３の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は８１．７％であり、また第２光束が入射したときは出射光において＋１次回折光の強度が最も高くなり、その回折効率は７０．６％であり、更に第３光束が入射したときは出射光において＋２次回折光の強度が最も高くなり、その回折効率は５０．７％である。実施例３の回折格子における第１光束の波長依存性を図１２に示す。 (Example 3)
Example 3 is a diffractive element provided with a diffractive groove formed by periodically repeating a five-step staircase structure with five terrace surfaces as one step unit. Table 3 shows the shape data thereof. In the staircase structure of Example 3, the material has an Abbe number of 56, the step amount of the first to fourth step surfaces = 5.025 μm, and the step amount of the fifth step surface = −20.201 μm. It is. When the first light beam is incident on the diffractive element of Example 3, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 81.7%, and when the second light beam is incident, it is emitted. In the incident light, the intensity of the + 1st order diffracted light is the highest, the diffraction efficiency is 70.6%, and when the third light beam is incident, the intensity of the + 2nd order diffracted light is the highest in the emitted light, and the diffraction efficiency is 50 0.7%. The wavelength dependence of the first light flux in the diffraction grating of Example 3 is shown in FIG.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　（実施例４）
　実施例４は、テラス面が７つある７ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表４に示す。実施例４の階段型構造は、素材のアッベ数が５６であり、第１～６番目の段差面の段差量＝５．０２５μｍであり、第７番目の段差面の段差量＝－３０．１５１μｍである。実施例４の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は６６．２％であり、また第２光束が入射したときは出射光において＋１次回折光の強度が最も高くなり、その回折効率は９３．０％であり、更に第３光束が入射したときは出射光において＋３次回折光の強度が最も高くなり、その回折効率は５１．５％である。実施例４の回折格子における第１光束の波長依存性を図１３に示す。 Example 4
Example 4 is a diffractive element provided with a diffractive groove formed by periodically repeating a seven-step staircase structure having seven terrace surfaces as one step unit. Table 4 shows the shape data thereof. In the staircase structure of Example 4, the Abbe number of the material is 56, the step amount of the first to sixth step surfaces = 5.025 μm, and the step amount of the seventh step surface = −30.151 μm. It is. When the first light beam is incident on the diffractive element of Example 4, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 66.2%, and when the second light beam is incident, the light is emitted. In the incident light, the intensity of the + 1st order diffracted light is the highest, the diffraction efficiency is 93.0%, and when the third light beam is incident, the intensity of the + 3rd order diffracted light is the highest in the emitted light, and the diffraction efficiency is 51 .5%. FIG. 13 shows the wavelength dependence of the first light flux in the diffraction grating of Example 4.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　（実施例５）
　実施例５は、テラス面が３つある３ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表５に示す。実施例５の階段型構造は、素材のアッベ数が３０であり、第１、２番目の段差面の段差量＝６．４７６μｍであり、第３番目の段差面の段差量＝－１２．９５１μｍである。実施例５の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は９３．６％であり、また第２光束が入射したときは出射光において－１次回折光の強度が最も高くなり、その回折効率は６０．７％であり、更に第３光束が入射したときは出射光において－１次回折光の強度が最も高くなり、その回折効率は６１．７％である。 (Example 5)
Example 5 is a diffractive element provided with a diffractive groove formed by periodically repeating a three-step staircase structure having three terrace surfaces as one step unit. Table 5 shows the shape data thereof. In the staircase structure of Example 5, the Abbe number of the material is 30, the step amount of the first and second step surfaces is 6.476 μm, and the step amount of the third step surface is −12.951 μm. It is. When the first light beam is incident on the diffractive element of Example 5, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 93.6%, and when the second light beam is incident, it is emitted. In the incident light, the intensity of the −1st order diffracted light is the highest, and its diffraction efficiency is 60.7%. Further, when the third light beam is incident, the intensity of the −1st order diffracted light is the highest in the emitted light, and its diffraction efficiency Is 61.7%.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
　（実施例６）
　実施例６は、テラス面が４つある４ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表６に示す。図１４は、実施例６の回折素子の光軸方向断面図である。実施例６の階段型構造は、素材のアッベ数が３０であり、第１～３番目の段差面の段差量＝５．８９０μｍであり、第４番目の段差面の段差量＝－１７．６６９μｍである。実施例６の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は８８．２％であり、また第２光束が入射したときは出射光において＋１次回折光の強度が最も高くなり、その回折効率は７６．３％であり、更に第３光束が入射したときは出射光において＋１次回折光の強度が最も高くなり、その回折効率は７１．１％である。 (Example 6)
Example 6 is a diffractive element provided with a diffractive groove formed by periodically repeating a four-step staircase structure having four terrace surfaces in units of one step. Table 6 shows the shape data thereof. FIG. 14 is a sectional view in the optical axis direction of the diffraction element of Example 6. In the staircase structure of Example 6, the Abbe number of the material is 30, the step amount of the first to third step surfaces = 5.890 μm, and the step amount of the fourth step surface = −17.669 μm. It is. When the first light beam is incident on the diffractive element of Example 6, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 88.2%, and when the second light beam is incident, it is emitted. The intensity of the + 1st order diffracted light is the highest in the incident light, and its diffraction efficiency is 76.3%. Further, when the third light beam is incident, the intensity of the + 1st order diffracted light is the highest in the emitted light, and the diffraction efficiency is 71 .1%.
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
　（実施例７）
　実施例７は、テラス面が４つある４ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表７に示す。実施例７の階段型構造は、素材のアッベ数が３０であり、第１～３番目の段差面の段差量＝６．５０８μｍであり、第４番目の段差面の段差量＝－１９．５２４μｍである。実施例７の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は１００．０％であり、また第２光束が入射したときは出射光において－１次回折光の強度が最も高くなり、その回折効率は８０．４％であり、更に第３光束が入射したときは出射光において－１次回折光の強度が最も高くなり、その回折効率は８１．０％である。 (Example 7)
Example 7 is a diffractive element provided with a diffractive groove formed by periodically repeating a four-step staircase structure having four terrace surfaces as one step unit, and the shape data is shown in Table 7. In the stepped structure of Example 7, the Abbe number of the material is 30, the step amount of the first to third step surfaces = 6.508 μm, and the step amount of the fourth step surface = −19.524 μm. It is. When the first light beam is incident on the diffractive element of Example 7, the intensity of the 0th-order diffracted light is the highest in the outgoing light, its diffraction efficiency is 100.0%, and when the second light beam is incident, it is emitted. In the incident light, the intensity of the −1st order diffracted light is the highest, and its diffraction efficiency is 80.4%. Further, when the third light beam is incident, the intensity of the −1st order diffracted light is the highest in the emitted light, and the diffraction efficiency is increased. Is 81.0%.
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000007
　（実施例８）
　実施例８は、テラス面が５つある５ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表８に示す。実施例８の階段型構造は、素材のアッベ数が３０であり、第１～４番目の段差面の段差量＝５．１７４μｍであり、第５番目の段差面の段差量＝－２０．６９６μｍである。実施例８の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は８１．７％であり、また第２光束が入射したときは出射光において－２次回折光の強度が最も高くなり、その回折効率は５５．７％であり、更に第３光束が入射したときは出射光において－１次回折光の強度が最も高くなり、その回折効率は８４．３％である。 (Example 8)
Example 8 is a diffractive element provided with a diffractive groove formed by periodically repeating a five-step staircase structure with five terrace surfaces as one step unit, and the shape data is shown in Table 8. In the step type structure of Example 8, the Abbe number of the material is 30, the step amount of the first to fourth step surfaces = 5.174 μm, and the step amount of the fifth step surface = -20.696 μm. It is. When the first light beam is incident on the diffractive element of Example 8, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 81.7%, and when the second light beam is incident, it is emitted. In the incident light, the intensity of the −2nd order diffracted light is the highest, and its diffraction efficiency is 55.7%. Further, when the third light beam is incident, the intensity of the −1st order diffracted light is the highest in the emitted light, and the diffraction efficiency is increased. Is 84.3%.
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
　（実施例９）
　実施例９は、テラス面が５つある５ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表９に示す。実施例９の階段型構造は、素材のアッベ数が３０であり、第１～４番目の段差面の段差量＝５．８２５μｍであり、第５番目の段差面の段差量＝－２３．２９９μｍである。実施例９の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は８１．７％であり、また第２光束が入射したときは出射光において＋１次回折光の強度が最も高くなり、その回折効率は７５．６％であり、更に第３光束が入射したときは出射光において＋１次回折光の強度が最も高くなり、その回折効率は６９．３％である。 Example 9
Example 9 is a diffractive element provided with a diffractive groove formed by periodically repeating a five-step staircase structure with five terrace surfaces as one step unit, and the shape data is shown in Table 9. In the staircase structure of Example 9, the Abbe number of the material is 30, the step amount of the first to fourth step surfaces = 5.825 μm, and the step amount of the fifth step surface = −23.299 μm. It is. When the first light beam is incident on the diffractive element of Example 9, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 81.7%, and when the second light beam is incident, it is emitted. The intensity of the + 1st order diffracted light is the highest in the incident light, and its diffraction efficiency is 75.6%. Further, when the third light beam is incident, the intensity of the + 1st order diffracted light is the highest in the emitted light, and the diffraction efficiency is 69. .3%.
Figure JPOXMLDOC01-appb-T000009
Figure JPOXMLDOC01-appb-T000009
　（実施例１０）
　実施例１０は、テラス面が５つある５ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表１０に示す。実施例１０の階段型構造は、素材のアッベ数が３０であり、第１～４番目の段差面の段差量＝６．５０８μｍであり、第５番目の段差面の段差量＝－２６．０３２μｍである。実施例１０の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は１００．０％であり、また第２光束が入射したときは出射光において－１次回折光の強度が最も高くなり、その回折効率は７８．２％であり、更に第３光束が入射したときは出射光において－１次回折光の強度が最も高くなり、その回折効率は７３．１％である。 (Example 10)
Example 10 is a diffractive element provided with a diffractive groove formed by periodically repeating a five-step staircase structure with five terrace surfaces as one step unit. Table 10 shows the shape data thereof. In the stepped structure of Example 10, the Abbe number of the material is 30, the step amount of the first to fourth step surfaces = 6.508 μm, and the step amount of the fifth step surface = −26.032 μm. It is. When the first light beam is incident on the diffractive element of Example 10, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 100.0%, and when the second light beam is incident, it is emitted. In the incident light, the intensity of the −1st order diffracted light is the highest, and its diffraction efficiency is 78.2%. Further, when the third light beam is incident, the intensity of the −1st order diffracted light is the highest in the emitted light, and its diffraction efficiency Is 73.1%.
Figure JPOXMLDOC01-appb-T000010
Figure JPOXMLDOC01-appb-T000010
　（実施例１１）
　実施例１１は、テラス面が７つある７ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表１１に示す。実施例１１の階段型構造は、素材のアッベ数が３０であり、第１～６番目の段差面の段差量＝５．８５７μｍであり、第７番目の段差面の段差量＝－３５．１４４μｍである。実施例１１の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は１００．０％であり、また第２光束が入射したときは出射光において＋１次回折光の強度が最も高くなり、その回折効率は６８．８％であり、更に第３光束が入射したときは出射光において＋２次回折光の強度が最も高くなり、その回折効率は７５．０％である。 (Example 11)
Example 11 is a diffractive element provided with a diffractive groove formed by periodically repeating a seven-step staircase structure having seven terrace surfaces in units of one step. Table 11 shows the shape data thereof. In the staircase structure of Example 11, the Abbe number of the material is 30, the step amount of the first to sixth step surfaces = 5.857 μm, and the step amount of the seventh step surface = −35.144 μm. It is. When the first light beam is incident on the diffractive element of Example 11, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 100.0%, and when the second light beam is incident, it is emitted. In the incident light, the intensity of the + 1st order diffracted light is the highest, and its diffraction efficiency is 68.8%. Further, when the third light beam is incident, the intensity of the + 2nd order diffracted light is the highest in the emitted light, and the diffraction efficiency is 75. 0.0%.
Figure JPOXMLDOC01-appb-T000011
Figure JPOXMLDOC01-appb-T000011
　（実施例１２）
　実施例１２は、テラス面が７つある７ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表１２に示す。実施例１２の階段型構造は、素材のアッベ数が３０であり、第１～６番目の段差面の段差量＝６．４７６μｍであり、第７番目の段差面の段差量＝－３８．８５３μｍである。実施例１２の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は６６．２％であり、また第２光束が入射したときは出射光において－２次回折光の強度が最も高くなり、その回折効率は７１．５％であり、更に第３光束が入射したときは出射光において－２次回折光の強度が最も高くなり、その回折効率は７３．３％である。 (Example 12)
Example 12 is a diffractive element provided with a diffractive groove formed by periodically repeating a seven-step staircase structure having seven terrace surfaces as one step unit, and its shape data is shown in Table 12. In the staircase structure of Example 12, the Abbe number of the material is 30, the step amount of the first to sixth step surfaces = 6.476 μm, and the step amount of the seventh step surface = −38.853 μm It is. When the first light beam is incident on the diffractive element of Example 12, the intensity of the 0th-order diffracted light is the highest in the outgoing light, its diffraction efficiency is 66.2%, and when the second light beam is incident, it is emitted. In the incident light, the intensity of the −2nd order diffracted light is the highest, the diffraction efficiency is 71.5%, and when the third light beam is incident, the intensity of the −2nd order diffracted light is the highest in the emitted light, and the diffraction efficiency is increased. Is 73.3%.
Figure JPOXMLDOC01-appb-T000012
Figure JPOXMLDOC01-appb-T000012
　（実施例１３）
　実施例１３は、テラス面が８つある８ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表１３に示す。実施例１３の階段型構造は、素材のアッベ数が３０であり、第１～７番目の段差面の段差量＝５．８２５μｍであり、第８番目の段差面の段差量＝－４０．７７３μｍである。実施例１３の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は５７．８％であり、また第２光束が入射したときは出射光において＋１次回折光の強度が最も高くなり、その回折効率は７６．０％であり、更に第３光束が入射したときは出射光において＋２次回折光の強度が最も高くなり、その回折効率は８０．８％である。 (Example 13)
Example 13 is a diffractive element provided with a diffraction groove that is formed by periodically repeating an eight-step staircase structure having eight terrace surfaces as one step unit, and its shape data is shown in Table 13. In the step type structure of Example 13, the Abbe number of the material is 30, the step amount of the first to seventh step surfaces = 5.825 μm, and the step amount of the eighth step surface = −40.773 μm. It is. When the first light beam is incident on the diffraction element of Example 13, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 57.8%, and when the second light beam is incident, In the incident light, the intensity of the + 1st order diffracted light is the highest, the diffraction efficiency is 76.0%, and when the third light beam is incident, the intensity of the + 2nd order diffracted light is the highest in the emitted light, and the diffraction efficiency is 80 8%.
Figure JPOXMLDOC01-appb-T000013
Figure JPOXMLDOC01-appb-T000013
　（実施例１４）
　実施例１４は、テラス面が８つある８ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表１４に示す。実施例１４の階段型構造は、素材のアッベ数が３０であり、第１～７番目の段差面の段差量＝６．５０８μｍであり、第８番目の段差面の段差量＝－４５．５５７μｍである。実施例１４の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は１００．０％であり、また第２光束が入射したときは出射光において－２次回折光の強度が最も高くなり、その回折効率は７８．５％であり、更に第３光束が入射したときは出射光において－２次回折光の強度が最も高くなり、その回折効率は８０．９％である。 (Example 14)
Example 14 is a diffractive element provided with a diffraction groove which is formed by periodically repeating an eight-step staircase structure having eight terrace surfaces in units of one step. Table 14 shows the shape data thereof. In the staircase structure of Example 14, the Abbe number of the material is 30, the step amount of the first to seventh step surfaces = 6.508 μm, and the step amount of the eighth step surface = −45.557 μm. It is. When the first light beam is incident on the diffractive element of Example 14, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 100.0%, and when the second light beam is incident, it is emitted. In the incident light, the intensity of the −2nd order diffracted light is the highest, and its diffraction efficiency is 78.5%. Further, when the third light beam is incident, the intensity of the −2nd order diffracted light is the highest in the emitted light, and its diffraction efficiency Is 80.9%.
Figure JPOXMLDOC01-appb-T000014
Figure JPOXMLDOC01-appb-T000014
　（実施例１５）
　実施例１５は、テラス面が９つある９ステップの階段型構造を１ステップ単位として周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表１５に示す。実施例１５の階段型構造は、素材のアッベ数が３０であり、第１～８番目の段差面の段差量＝６．５０８μｍであり、第９番目の段差面の段差量＝－５２．０６５μｍである。実施例１５の回折素子に、第１光束が入射したときは出射光において０次回折光の強度が最も高くなり、その回折効率は１００．０％であり、また第２光束が入射したときは出射光において－２次回折光の強度が最も高くなり、その回折効率は７９．６％であり、更に第３光束が入射したときは出射光において－２次回折光の強度が最も高くなり、その回折効率は７１．６％である。 (Example 15)
Example 15 is a diffractive element provided with a diffractive groove formed by periodically repeating a nine-step staircase structure with nine terrace surfaces as one step unit. Table 15 shows the shape data thereof. In the staircase structure of Example 15, the Abbe number of the material is 30, the step amount of the first to eighth step surfaces = 6.508 μm, and the step amount of the ninth step surface = −52.005 μm It is. When the first light beam is incident on the diffractive element of Example 15, the intensity of the 0th-order diffracted light is the highest in the emitted light, its diffraction efficiency is 100.0%, and when the second light beam is incident, it is emitted. In the incident light, the intensity of the −2nd order diffracted light is the highest, and its diffraction efficiency is 79.6%. Further, when the third light beam is incident, the intensity of the −2nd order diffracted light is the highest in the emitted light, and the diffraction efficiency is increased. Is 71.6%.
Figure JPOXMLDOC01-appb-T000015
Figure JPOXMLDOC01-appb-T000015
　（実施例１６）
　実施例１６は、実施例３の５ステップの階段型構造のうち高い方の２ステップを光軸方向の低い側に、光路差にして、－２０×λ１だけシフト（物理的なシフト量は、－２０×λ１／（ｎ１－１）＝－１４．４６１μｍである）したものを１ステップ単位とし、これを周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表１６に示す。図１５（ｃ）に、実施例１６の回折構造の断面図を示す。実施例１６の階段型構造は、素材のアッベ数が５６であり、１番目の段差面の段差量＝５．０２５μｍであり、２番目の段差面の段差量＝５．０２５μｍであり、３番目の段差面の段差量＝－９．４３６μｍであり、４番目の段差面の段差量＝５．０２５μｍであり、５番目の段差面の段差量＝－５．６４０μｍである。 (Example 16)
In Example 16, the higher two steps of the five-step staircase structure of Example 3 are shifted to the lower side in the optical axis direction by an optical path difference and shifted by −20 × λ1 (the physical shift amount is -20 × λ1 / (n1-1) = − 14.461 μm) is a diffractive element having a diffractive groove formed by repeating this periodically, and the shape data is shown in Table 16 Shown in FIG. 15C is a cross-sectional view of the diffractive structure of Example 16. In the staircase structure of Example 16, the Abbe number of the material is 56, the step amount of the first step surface is 5.025 μm, the step amount of the second step surface is 5.025 μm, and the third step The step amount of the step surface = −9.436 μm, the step amount of the fourth step surface = 5.025 μm, and the step amount of the fifth step surface = −5.640 μm.
　実施例１６の階段型構造を言い換えると、図１５（ａ）に示すごとき、回折構造が、光ピックアップ装置の光軸（図１５で左右方向）に略平行に延在する５つの第１段差面ＳＴ１と、第１段差面ＳＴ１と交差する５つの第１テラス面ＴＲ１とを有すると共に、隣接する第１テラス面ＴＲ１が光ピックアップ装置の光軸方向に順次シフトしてなる第１ステップ単位を、光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第１ステップ周期構造ＣＳ１（５ステップ構造）と、図１５（ｂ）に示すごとき、光ピックアップ装置の光軸に略平行に延在する２つの第２段差面ＳＴ２と、第２段差面ＳＴ２と交差する２つの第２テラス面ＴＲ２とを有し、２つの第２段差面ＳＴ２が光軸直交方向に重なり合う第２ステップ単位を、光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第２ステップ周期構造ＣＳ２（２ステップ構造）とを、互いに周期を合わせて重畳してなり（図１５（ｃ）参照）、且つ以下の式（１３）～（１５）を満たすものである。 In other words, the staircase structure of Example 16 has five first step surfaces in which the diffractive structure extends substantially parallel to the optical axis of the optical pickup device (left-right direction in FIG. 15) as shown in FIG. A first step unit having ST1 and five first terrace surfaces TR1 intersecting with the first step surface ST1 and sequentially shifting adjacent first terrace surfaces TR1 in the optical axis direction of the optical pickup device, A first step periodic structure CS1 (5-step structure) formed by arranging a plurality of elements along the direction intersecting the optical axis of the optical pickup device, and the optical axis of the optical pickup device as shown in FIG. And two second step surfaces ST2 that intersect the second step surface ST2, and the two second step surfaces ST2 overlap in the direction perpendicular to the optical axis. Second A second step periodic structure CS2 (two-step structure) formed by arranging a plurality of step units along a direction intersecting the optical axis of the optical pickup device is overlapped with the same period. 15 (c)) and the following expressions (13) to (15) are satisfied.
　｜ΣΦ１ｊ｜＝０　　　　　　　　　　　　　　　（１３）
　｜ΣΦ２ｊ｜＝１　　　　　　　　　　　　　　　（１４）
　｜ΣΦ３ｊ｜＝１　　　　　　　　　　　　　　　（１５）
但し、Φｉｊ（ｉ＝１、２、３）は、一ステップ単位内に存在する段差量（隣接する前記テラス面間の前記光軸方向シフト量とする）を第１段差量ｄ１、第２段差量ｄ２、第３段差量ｄ３、・・・・、第ｊ段差量ｄｊ、としたとき、各段差量により発生する第ｉ波長λｉの位相差である。
ここで、
Φｉｊ＝φｉｊ－ＲＯＵＮＤ（φｉ）
φｉｊ＝ｄｊ／λｉ×（ｎｉ－１）
ΣΦｉｊ＝Φｉ１＋Φｉ２＋・・・＋Φｉｊ－１＋Φｉｊ
第ｉ波長：λｉ（μｍ）
第ｉ波長λｉにおける回折素子の屈折率：ｎｉ
第ｊ段差：ｄｊ（μｍ）
任意の実数Ａの小数点以下第一位を四捨五入して得られる整数：ＲＯＵＮＤ（Ａ）
である。 | ΣΦ1j | = 0 (13)
| ΣΦ2j | = 1 (14)
| ΣΦ3j | = 1 (15)
However, Φij (i = 1, 2, 3) is the first step amount d1 and the second step amount, which is the step amount existing in one step unit (the shift amount in the optical axis direction between the adjacent terrace surfaces). When the amount d2, the third step amount d3,..., The jth step amount dj, the phase difference of the i-th wavelength λi generated by each step amount.
here,
Φij = φij−ROUND (φi)
φij = dj / λi × (ni−1)
ΣΦij = Φi1 + Φi2 + ... + Φij-1 + Φij
I-th wavelength: λi (μm)
Refractive index of diffraction element at i-th wavelength λi: ni
J-th step: dj (μm)
Integer obtained by rounding the first decimal place of any real number A: ROUND (A)
It is.
　実施例１６の階段型構造を更に言い換えると、光軸直交方向において、段差面ＳＴが図１５（ｃ）で上方に隣接するテラス面ＴＲより右側に向かう方向を正、図１５（ｃ）で上方に隣接するテラス面ＴＲより左側に向かう方向を負としたときに、段差面ＳＴは、一ステップ単位内で上方から順に正、正、負、正、負の順に配列されており、対向する正の段差面ＳＴと負の段差面ＳＴの光軸方向長さの絶対値は異なっている。尚、この構造に、図５に示すような斜面や微小段差を設けることは任意である。又、第１ステップ周期構造の第１段差面は３つ以上であれば足りる。 In other words, the stepped structure of the sixteenth embodiment is positive in the direction perpendicular to the optical axis in which the step surface ST is directed to the right side from the terrace surface TR adjacent to the upper side in FIG. 15C and upward in FIG. The step surface ST is arranged in the order of positive, positive, negative, positive, negative from the top in one step unit when the direction toward the left side from the terrace surface TR adjacent to the negative is negative. The absolute value of the length in the optical axis direction of the step surface ST and the negative step surface ST is different. In addition, it is arbitrary to provide a slope or a minute step as shown in FIG. 5 in this structure. Further, it is sufficient that the first step periodic structure has three or more first step surfaces.
Figure JPOXMLDOC01-appb-T000016
Figure JPOXMLDOC01-appb-T000016
　図１６は、実施例１６の回折素子における回折効率の波長依存性を示す図である。図１６に示すように、４０５ｎｍを中心として、半導体レーザに±５ｎｍの波長変化が生じた場合でも、回折効率の低下は約２０％程度であり、図１２と比較してわかるように波長特性の改善が図られている。しかしながら、実施例１６では、第１光束の０次回折光の回折効率が８１．７％、第２光束の＋１次回折光の回折効率が７９．５％であるのに対し、第３光束の＋１次回折光の回折効率は３６．９％と低く、その増大が課題となっている。 FIG. 16 is a diagram showing the wavelength dependence of diffraction efficiency in the diffraction element of Example 16. As shown in FIG. 16, even when a wavelength change of ± 5 nm occurs in the semiconductor laser centering on 405 nm, the reduction in diffraction efficiency is about 20%. As can be seen from the comparison with FIG. Improvements are being made. However, in Example 16, the diffraction efficiency of the 0th-order diffracted light of the first light flux is 81.7% and the diffraction efficiency of the + 1st-order diffracted light of the second light flux is 79.5%, whereas the +1 next time of the third light flux. The diffraction efficiency of folding light is as low as 36.9%, and its increase is a problem.
　（実施例１７）
　実施例１７は、実施例４の１番目～６番目の段差量＝５．０２５μｍ、７番目の段差量が、－３０．１５１μｍである７ステップの階段型構造のうち高い方から４番目及び５番目の２ステップを光軸方向の低い側に、光路差にして、－１０×λ１だけシフト（物理的なシフト量は、－１０×λ１／（ｎ１－１）＝－７．２３０μｍである）し、さらに高い方の３ステップを光軸方向の低い側に、光路差にして、－２０×λ１だけシフト（物理的なシフト量は、－２０×λ１／（ｎ１－１）＝－１４．４６１μｍである）したものを１ステップ単位とし、これを周期的に繰り返してなる回折溝を備えた回折素子であり、その形状データを表１７に示す。図１７（ｄ）に、実施例１７の回折構造の断面図を示す。実施例１７の階段型構造は、素材のアッベ数が５６であり、１番目の段差面の段差量＝５．０２５μｍであり、２番目の段差面の段差量＝－２．２０５μｍであり、３番目の段差面の段差量＝５．０２５μｍであり、４番目の段差面の段差量＝－９．４３６μｍであり、５番目の段差面の段差量＝５．０２５μｍであり、６番目の段差面の段差量＝５．０２５μｍであり、７番目の段差面の段差量＝－８．４６０μｍである。 (Example 17)
In the seventeenth embodiment, the first to sixth steps of the fourth embodiment = 5.025 μm, and the seventh step is −30.151 μm. The second step is shifted to the lower side in the optical axis direction by an optical path difference and shifted by −10 × λ1 (the physical shift amount is −10 × λ1 / (n1-1) = − 7.230 μm) Then, the higher three steps are shifted to the lower side in the optical axis direction by an optical path difference and shifted by −20 × λ1 (the physical shift amount is −20 × λ1 / (n1-1) = − 14. A diffraction element having a diffraction groove formed by periodically repeating this step is 461 μm), and its shape data is shown in Table 17. FIG. 17D shows a sectional view of the diffractive structure of Example 17. In FIG. In the step type structure of Example 17, the Abbe number of the material is 56, the step amount of the first step surface = 5.025 μm, the step amount of the second step surface = −2.205 μm, 3 Step amount of the fifth step surface = 5.025 μm, Step amount of the fourth step surface = −9.436 μm, Step amount of the fifth step surface = 5.025 μm, Sixth step surface Step amount = 5.025 μm, and step amount of the seventh step surface = −8.460 μm.
　実施例１７の階段型構造を言い換えると、図１７（ａ）に示すごとき、回折構造が、光ピックアップ装置の光軸（図１７で左右方向）に略平行に延在する７つの第１段差面ＳＴ１と、第１段差面ＳＴ１と交差する７つの第１テラス面ＴＲ１とを有すると共に、隣接する第１テラス面ＴＲ１が光ピックアップ装置の光軸方向に順次シフトしてなる第１ステップ単位を、光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第１ステップ周期構造ＣＳ１（７ステップ構造）と、図１７（ｂ）に示すごとき、光ピックアップ装置の光軸に略平行に延在する２つの第２段差面ＳＴ２と、第２段差面ＳＴ２と交差する２つの第２テラス面ＴＲ２とを有し、２つの第２段差面ＳＴ２が光軸直交方向に重なり合う第２ステップ単位を、光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第２ステップ周期構造ＣＳ２（２ステップ構造）と、図１７（ｃ）に示すごとき、光ピックアップ装置の光軸に略平行に延在する２つの第３段差面ＳＴ３と、第３段差面ＳＴ３と交差する２つの第３テラス面ＴＲ３とを有し、２つの第３段差面ＳＴ３が光軸直交方向に重なり合う第３ステップ単位を、光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第３ステップ周期構造ＣＳ３（２ステップ構造）とを、互いに周期を合わせて重畳してなり（図１７（ｄ）参照）、且つ以下の式（１３）～（１５）を満たすものである。 In other words, the staircase structure of the seventeenth embodiment has seven first step surfaces in which the diffractive structure extends substantially parallel to the optical axis of the optical pickup device (left-right direction in FIG. 17), as shown in FIG. A first step unit having ST1 and seven first terrace surfaces TR1 intersecting with the first step surface ST1 and sequentially shifting the adjacent first terrace surfaces TR1 in the optical axis direction of the optical pickup device, A first step periodic structure CS1 (7 step structure) formed by arranging a plurality of elements along the direction intersecting the optical axis of the optical pickup device, and the optical axis of the optical pickup device as shown in FIG. And two second step surfaces ST2 that intersect the second step surface ST2, and the two second step surfaces ST2 overlap in the direction perpendicular to the optical axis. Second A second step periodic structure CS2 (two step structure) formed by arranging a plurality of step units along a direction intersecting the optical axis of the optical pickup device, and an optical pickup as shown in FIG. There are two third step surfaces ST3 extending substantially parallel to the optical axis of the apparatus, and two third terrace surfaces TR3 intersecting the third step surface ST3, and the two third step surfaces ST3 are optical axes. A third step periodic structure CS3 (two-step structure) formed by arranging a plurality of third step units overlapping in the orthogonal direction along a direction intersecting the optical axis of the optical pickup device is aligned with each other. (See FIG. 17D) and satisfy the following formulas (13) to (15).
　｜ΣΦ１ｊ｜＝０　　　　　　　　　　　　　　　（１３）
　｜ΣΦ２ｊ｜＝１　　　　　　　　　　　　　　　（１４）
　｜ΣΦ３ｊ｜＝２　　　　　　　　　　　　　　　（１５）
但し、Φｉｊ（ｉ＝１、２、３）は、一ステップ単位内に存在する段差量（隣接する前記テラス面間の前記光軸方向シフト量とする）を第１段差量ｄ１、第２段差量ｄ２、第３段差量ｄ３、・・・・、第ｊ段差量ｄｊ、としたとき、各段差量により発生する第ｉ波長λｉの位相差である。
ここで、
Φｉｊ＝φｉｊ－ＲＯＵＮＤ（φｉ）
φｉｊ＝ｄｊ／λｉ×（ｎｉ－１）
ΣΦｉｊ＝Φｉ１＋Φｉ２＋・・・＋Φｉｊ－１＋Φｉｊ
第ｉ波長：λｉ（μｍ）
第ｉ波長λｉにおける回折素子の屈折率：ｎｉ
第ｊ段差：ｄｊ（μｍ）
任意の実数Ａの小数点以下第一位を四捨五入して得られる整数：ＲＯＵＮＤ（Ａ）
である。 | ΣΦ1j | = 0 (13)
| ΣΦ2j | = 1 (14)
| ΣΦ3j | = 2 (15)
However, Φij (i = 1, 2, 3) is the first step amount d1 and the second step amount, which is the step amount existing in one step unit (the shift amount in the optical axis direction between the adjacent terrace surfaces). When the amount d2, the third step amount d3,..., The jth step amount dj, the phase difference of the i-th wavelength λi generated by each step amount.
here,
Φij = φij−ROUND (φi)
φij = dj / λi × (ni−1)
ΣΦij = Φi1 + Φi2 + ... + Φij-1 + Φij
I-th wavelength: λi (μm)
Refractive index of diffraction element at i-th wavelength λi: ni
J-th step: dj (μm)
Integer obtained by rounding the first decimal place of any real number A: ROUND (A)
It is.
　実施例１７の階段型構造を更に言い換えると、光軸直交方向において、段差面が図１７で上方に隣接するテラス面ＴＲより右側に向かう方向を正、図１７で上方に隣接するテラス面ＴＲより左側に向かう方向を負としたときに、段差面は、上方から順に正、負、正、負、正、正、負の順に配列されており、対向する正の前記段差面と負の前記段差面の光軸方向長さの絶対値は異なっている。尚、この構造に、図５に示すような斜面や微小段差を設けることは任意である。又、第１ステップ周期構造の第１段差面は５つ以上であれば足りる。 In other words, the stepped structure of the seventeenth embodiment is positive in the direction perpendicular to the optical axis in the direction perpendicular to the optical axis from the terrace surface TR adjacent to the upper side in FIG. 17 and from the terrace surface TR adjacent to the upper side in FIG. When the direction toward the left is negative, the step surfaces are arranged in order of positive, negative, positive, negative, positive, positive, negative from the top, and the positive step surface and the negative step that face each other. The absolute value of the length of the surface in the optical axis direction is different. In addition, it is arbitrary to provide a slope or a minute step as shown in FIG. 5 in this structure. Further, it is sufficient that the first step periodic structure has five or more first step surfaces.
Figure JPOXMLDOC01-appb-T000017
Figure JPOXMLDOC01-appb-T000017
　図１８は、実施例１７の回折素子における回折効率の波長依存性を示す図である。図１８に示すように、４０５ｎｍを中心として、半導体レーザに±５ｎｍの波長変化が生じた場合でも、回折効率の低下は約２０％程度であり、図１３と比較してわかるように波長特性の改善が図られている。しかも、実施例１７では、第１光束の０次回折光の回折効率が６８．９％、第２光束の＋１次回折光の回折効率が８７．５％、第３光束の＋２次回折光の回折効率が４３．８％となり、各光束の回折効率のバランスが図られている。 FIG. 18 is a graph showing the wavelength dependence of the diffraction efficiency in the diffraction element of Example 17. As shown in FIG. 18, even when a wavelength change of ± 5 nm occurs in the semiconductor laser centering on 405 nm, the reduction in diffraction efficiency is about 20%. As can be seen from the comparison with FIG. Improvements are being made. Moreover, in Example 17, the diffraction efficiency of the 0th-order diffracted light of the first light flux is 68.9%, the diffraction efficiency of the + 1st-order diffracted light of the second light flux is 87.5%, and the diffraction efficiency of the + 2nd-order diffracted light of the third light flux is 43.8%, which balances the diffraction efficiency of each light beam.
　以上の実施例では、光束が出射する側の光学面上に回折溝を形成したが、光束が入射する側の光学面上に回折溝を形成してもよい。 In the above embodiment, the diffraction groove is formed on the optical surface on the side from which the light beam is emitted. However, the diffraction groove may be formed on the optical surface on the side on which the light beam is incident.
　本発明は、明細書に記載の実施例に限定されるものではなく、他の実施例・変形例を含むことは、本明細書に記載された実施例や思想から本分野の当業者にとって明らかである。明細書の記載及び実施例は、あくまでも例証を目的としており、本発明の範囲は後述するクレームによって示されている。 The present invention is not limited to the embodiments described in the specification, and other embodiments and modifications are apparent to those skilled in the art from the embodiments and ideas described in the present specification. It is. The description and examples are for illustrative purposes only, and the scope of the invention is indicated by the following claims.
　ＣＯＬ　コリメートレンズ
　ＤＥ　回折素子
　ＧＲＴ　グレーティング
　ＨＤ　ホルダ
　ＬＤ１　第１半導体レーザ
　ＬＤ２　第２半導体レーザ
　ＬＤ３　第３半導体レーザ
　ＬＤＰ　光源ユニット
　ＯＢＪ　対物レンズ
　ＯＢＪ１　第１対物レンズ
　ＯＢＪ２　第２対物レンズ
　ＰＢＳ　偏光ビームスプリッタ
　ＰＤ　光検出器
　ＰＵ１　光ピックアップ装置
　ＰＵ２　光ピックアップ装置
　ＱＷＰ　λ／４波長板
　ＳＮ　センサレンズ COL collimating lens DE diffractive element GRT grating HD holder LD1 first semiconductor laser LD2 second semiconductor laser LD3 third semiconductor laser LDP light source unit OBJ objective lens OBJ1 first objective lens OBJ2 second objective lens PBS polarizing beam splitter PD photodetector PU1 Optical pickup device PU2 Optical pickup device QWP λ / 4 wave plate SN Sensor lens

Claims (14)

  1. 　波長λ１の第１光束を出射する第１発光部と、波長λ２（λ１＜λ２）の第２光束を出射する第２発光部と、波長λ３（λ２＜λ３）の第３光束を出射する第３発光部とを備えた光源と、対物光学系と、単一の光検出器と、前記光源と前記光検出器との間の光路内に移動可能に配置され、前記第１光束と前記第２光束と前記第３光束が共通して通過する回折素子とを有し、前記第１発光部からの光束を、前記対物光学系により第１光ディスクの情報記録面上に集光させることでスポットを形成し、その反射光を受光した前記光検出器からの信号に基づいて、前記第１光ディスクに対して情報の記録及び／又は再生を行い、前記第２発光部からの光束を、前記対物光学系により第２光ディスクの情報記録面上に集光させることでスポットを形成し、その反射光を受光した前記光検出器からの信号に基づいて、前記第２光ディスクに対して情報の記録及び／又は再生を行い、前記第３発光部からの光束を、前記対物光学系により第３光ディスクの情報記録面上に集光させることでスポットを形成し、その反射光を受光した前記光検出器からの信号に基づいて、前記第３光ディスクに対して情報の記録及び／又は再生を行う光ピックアップ装置に用いる回折素子であって、
    　前記光源は、前記第２発光部と前記第３発光部は同一のチップ上に形成され、前記第１発光部は、前記第２発光部及び前記第３発光部とは異なるチップ上に形成されており、
    　前記回折素子は、前記第１の光束は透過し、かつ、前記第２の光束、及び、前記第３の光束は回折する回折溝を有することを特徴とする回折素子。     A first light-emitting unit that emits a first light beam with wavelength λ1, a second light-emitting unit that emits a second light beam with wavelength λ2 (λ1 <λ2), and a third light beam with a wavelength λ3 (λ2 <λ3). A light source including three light emitting units, an objective optical system, a single photodetector, and movably disposed in an optical path between the light source and the photodetector. A diffractive element through which the two light beams and the third light beam pass in common, and the light beam from the first light emitting unit is condensed on the information recording surface of the first optical disk by the objective optical system. And recording and / or reproducing information with respect to the first optical disk based on a signal from the photodetector that has received the reflected light, and a light beam from the second light emitting unit is used as the objective light. A spot is formed by condensing on the information recording surface of the second optical disk by the optical system, Information is recorded and / or reproduced on the second optical disk based on a signal from the photodetector that has received the reflected light, and a light beam from the third light emitting unit is reflected by the objective optical system. A spot is formed by condensing on the information recording surface of the three optical discs, and information is recorded and / or reproduced on the third optical disc based on a signal from the photodetector that receives the reflected light. A diffraction element used in an optical pickup device to perform,
    In the light source, the second light emitting unit and the third light emitting unit are formed on the same chip, and the first light emitting unit is formed on a chip different from the second light emitting unit and the third light emitting unit. And
    The diffractive element has a diffraction groove that transmits the first light beam and diffracts the second light beam and the third light beam.
  2. 　前記回折溝は一次元構造であることを特徴とする請求項１に記載の回折素子。 The diffraction element according to claim 1, wherein the diffraction groove has a one-dimensional structure.
  3. 　前記回折溝は、前記光ピックアップ装置の光学系の光軸に略平行に延在する３つ以上の段差面と、前記段差面と交差する３つ以上のテラス面とを有すると共に、隣接する前記テラス面が前記光ピックアップ装置の光軸方向に順次シフトしてなるステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって、ステップ周期構造を形成していることを特徴とする請求項１又は２に記載の回折素子。 The diffraction groove has three or more step surfaces extending substantially parallel to the optical axis of the optical system of the optical pickup device, and three or more terrace surfaces intersecting the step surface, and is adjacent to the step surface. A step periodic structure is formed by arranging a plurality of step units in which the terrace surface is sequentially shifted in the optical axis direction of the optical pickup device along a direction intersecting the optical axis of the optical pickup device. The diffraction element according to claim 1 or 2, wherein
  4. 　以下の式（１）～（３）を満たすことを特徴とする請求項１から３までのいずれか一項に記載の回折素子。
    　３９５（ｎｍ）≦λ１≦４１５（ｎｍ）　　　　　（１）
    　６３０（ｎｍ）≦λ２≦７００（ｎｍ）　　　　　（２）
    　７５０（ｎｍ）≦λ３≦８５０（ｎｍ）　　　　　（３）     The diffraction element according to any one of claims 1 to 3, wherein the following expressions (1) to (3) are satisfied.
    395 (nm) ≦ λ1 ≦ 415 (nm) (1)
    630 (nm) ≦ λ2 ≦ 700 (nm) (2)
    750 (nm) ≦ λ3 ≦ 850 (nm) (3)
  5. 　前記回折素子に、前記第２の光束が入射した場合に発生する回折光の回折次数と、前記第３の光束が入射した場合に発生する回折光の回折次数の符号が互いに等しいことを特徴とする請求項１から４までのいずれかに記載の回折素子。 The diffraction order of the diffracted light generated when the second light beam is incident on the diffractive element and the sign of the diffraction order of the diffracted light generated when the third light beam is incident are equal to each other. The diffraction element according to any one of claims 1 to 4.
  6. 　前記回折素子の素材のｄ線におけるアッベ数νｄが４０から７０の間であり、前記回折素子に前記第２の光束が入射した場合に発生する回折光の回折次数をｍ、前記回折素子に前記第３の光束が入射した場合に発生する回折光の回折次数をｎ、としたとき以下の式（４）～（７）のいずれかを満たすことを特徴とする請求項３に記載の回折素子。
    　（ｍ，ｎ）＝（１，１）　　　　　　　　　　　　　（４）
    　（ｍ，ｎ）＝（－１，－１）　　　　　　　　　　　（５）
    　（ｍ，ｎ）＝（１，２）　　　　　　　　　　　　　（６）
    　（ｍ，ｎ）＝（１，３）　　　　　　　　　　　　　（７）     The Abbe number νd at the d-line of the material of the diffractive element is between 40 and 70, and the diffraction order of diffracted light generated when the second light flux is incident on the diffractive element is m, 4. The diffractive element according to claim 3, wherein when the diffraction order of the diffracted light generated when the third light beam is incident is n, one of the following formulas (4) to (7) is satisfied: .
    (M, n) = (1,1) (4)
    (M, n) = (-1, -1) (5)
    (M, n) = (1,2) (6)
    (M, n) = (1,3) (7)
  7. 　前記回折素子の素材のｄ線におけるアッベ数νｄが２０から４０の間であり、前記回折素子に前記第２の光束が入射した場合に発生する回折光の回折次数をｍ、前記回折素子に前記第３の光束が入射した場合に発生する回折光の回折次数をｎ、としたとき以下の式（８）～（１３）のいずれかを満たすことを特徴とする請求項３に記載の回折素子。
    　（ｍ，ｎ）＝（１，１）　　　　　　　　　　　　（８）
    　（ｍ，ｎ）＝（－１，－１）　　　　　　　　　　（９）
    　（ｍ，ｎ）＝（－２，－１）　　　　　　　　　　（１０）
    　（ｍ，ｎ）＝（１，２）　　　　　　　　　　　　（１１）
    　（ｍ，ｎ）＝（－２，－２）　　　　　　　　　　（１２）     The Abbe number νd at the d-line of the material of the diffractive element is between 20 and 40, and the diffraction order of diffracted light generated when the second light flux is incident on the diffractive element is m, 4. The diffractive element according to claim 3, wherein when the diffraction order of the diffracted light generated when the third light beam is incident is n, one of the following formulas (8) to (13) is satisfied: .
    (M, n) = (1,1) (8)
    (M, n) = (-1, -1) (9)
    (M, n) = (− 2, −1) (10)
    (M, n) = (1,2) (11)
    (M, n) = (− 2, −2) (12)
  8. 　以下の式（１３）～（１５）を満たすことを特徴とする請求項６または７に記載の回折素子。
    　｜ΣΦ１ｊ｜＝０　　　　　　　　　　　　　　　（１３）
    　｜ΣΦ２ｊ｜＝ｍ　　　　　　　　　　　　　　　（１４）
    　｜ΣΦ３ｊ｜＝ｎ　　　　　　　　　　　　　　　（１５）
    但し、Φｉｊ（ｉ＝１、２、３）は、一ステップ単位内に存在する段差量（隣接する前記テラス面間の前記光軸方向シフト量とする）を第１段差量ｄ１、第２段差量ｄ２、第３段差量ｄ３、・・・・、第ｊ段差量ｄｊ、としたとき、各段差量により発生する第ｉ波長λｉの位相差である。
    ここで、
    Φｉｊ＝φｉｊ－ＲＯＵＮＤ（φｉ）
    φｉｊ＝ｄｊ／λｉ×（ｎｉ－１）
    ΣΦｉｊ＝Φｉ１＋Φｉ２＋・・・＋Φｉｊ－１＋Φｉｊ
    第ｉ波長：λｉ（μｍ）
    第ｉ波長λｉにおける回折素子の屈折率：ｎｉ
    第ｊ段差：ｄｊ（μｍ）
    任意の実数Ａの小数点以下第一位を四捨五入して得られる整数：ＲＯＵＮＤ（Ａ）     The diffraction element according to claim 6 or 7, wherein the following expressions (13) to (15) are satisfied.
    | ΣΦ1j | = 0 (13)
    | ΣΦ2j | = m (14)
    | ΣΦ3j | = n (15)
    However, Φij (i = 1, 2, 3) is the first step amount d1 and the second step amount, which is the step amount existing in one step unit (the shift amount in the optical axis direction between the adjacent terrace surfaces). When the amount d2, the third step amount d3,..., The jth step amount dj, the phase difference of the i-th wavelength λi generated by each step amount.
    here,
    Φij = φij−ROUND (φi)
    φij = dj / λi × (ni−1)
    ΣΦij = Φi1 + Φi2 + ... + Φij-1 + Φij
    I-th wavelength: λi (μm)
    Refractive index of diffraction element at i-th wavelength λi: ni
    J-th step: dj (μm)
    Integer obtained by rounding the first decimal place of any real number A: ROUND (A)
  9. 　前記回折溝は、前記光ピックアップ装置の光学系の光軸に略平行に延在する３つ以上の第１段差面と、前記第１段差面と交差する３つ以上の第１テラス面とを有すると共に、隣接する前記第１テラス面が前記光ピックアップ装置の光軸方向に順次シフトしてなる第１ステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第１ステップ周期構造と、前記光ピックアップ装置の光軸に略平行に延在する２つの第２段差面と、前記第２段差面と交差する２つの第２テラス面とを有し、前記２つの第２段差面が光軸直交方向に重なり合う第２ステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第２ステップ周期構造とを、互いに周期を合わせて重畳してなることを特徴とする請求項１から７までのいずれか一項に記載の回折素子。 The diffraction groove includes three or more first step surfaces extending substantially parallel to the optical axis of the optical system of the optical pickup device, and three or more first terrace surfaces intersecting the first step surface. And arranging a plurality of first step units formed by sequentially shifting the adjacent first terrace surfaces in the optical axis direction of the optical pickup device along a direction intersecting the optical axis of the optical pickup device. A first step periodic structure, two second step surfaces extending substantially parallel to the optical axis of the optical pickup device, and two second terrace surfaces intersecting the second step surface. And a second step periodic structure formed by arranging a plurality of second step units in which the two second step surfaces overlap in an optical axis orthogonal direction along a direction intersecting the optical axis of the optical pickup device. And each other Diffraction device according to any one of claims 1 to 7, characterized by comprising superimposed together period.
  10. 　前記回折溝は、前記光ピックアップ装置の光学系の光軸に略平行に延在する５つ以上の第１段差面と、前記第１段差面と交差する５つ以上の第１テラス面とを有すると共に、隣接する前記第１テラス面が前記光ピックアップ装置の光軸方向に順次シフトしてなる第１ステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第１ステップ周期構造と、前記光ピックアップ装置の光軸に略平行に延在する２つの第２段差面と、前記第２段差面と交差する２つの第２テラス面とを有し、前記２つの第２段差面が光軸直交方向に重なり合う第２ステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第２ステップ周期構造と、前記光ピックアップ装置の光軸に略平行に延在する２つの第３段差面と、前記第３段差面と交差する２つの第３テラス面とを有し、前記２つの第３段差面が光軸直交方向に重なり合う第３ステップ単位を、前記光ピックアップ装置の光軸に交差する方向に沿って複数個配置することによって形成された第３ステップ周期構造とを、互いに周期を合わせて重畳してなることを特徴とする請求項１から７までのいずれか一項に記載の回折素子。 The diffraction groove includes five or more first step surfaces that extend substantially parallel to the optical axis of the optical system of the optical pickup device, and five or more first terrace surfaces that intersect the first step surface. And arranging a plurality of first step units formed by sequentially shifting the adjacent first terrace surfaces in the optical axis direction of the optical pickup device along a direction intersecting the optical axis of the optical pickup device. A first step periodic structure, two second step surfaces extending substantially parallel to the optical axis of the optical pickup device, and two second terrace surfaces intersecting the second step surface. And a second step periodic structure formed by arranging a plurality of second step units in which the two second step surfaces overlap in an optical axis orthogonal direction along a direction intersecting the optical axis of the optical pickup device. And the light The apparatus has two third step surfaces that extend substantially parallel to the optical axis of the backup device and two third terrace surfaces that intersect the third step surface, and the two third step surfaces are orthogonal to the optical axis. A third step periodic structure formed by arranging a plurality of third step units overlapping in the direction along a direction intersecting the optical axis of the optical pickup device is overlapped with each other in the same period. The diffractive element according to any one of claims 1 to 7, wherein:
  11. 　以下の式を満たすことを特徴とする請求項１から１０までのいずれか一項に記載の回折素子。
    　｜ｍ｜＝｜ｎ｜　　　　　　　　　　　　　　　　（１６）     The diffraction element according to any one of claims 1 to 10, wherein the following expression is satisfied.
    | M | = | n | (16)
  12. 　前記回折溝は、平行平板上に形成されていることを特徴とする請求項１から１１までのいずれか一項に記載の回折素子。 The diffraction element according to any one of claims 1 to 11, wherein the diffraction groove is formed on a parallel plate.
  13. 　請求項１から１２までのいずれか一項に記載の回折素子を搭載したことを特徴とする光ピックアップ装置。 An optical pickup device comprising the diffraction element according to any one of claims 1 to 12.
  14. 　前記回折素子に前記第２の光束が入射した場合に発生する回折光の回折次数をｍ、前記回折素子に前記第３の光束が入射した場合に発生する回折光の回折次数をｎ、前記第１発光部と前記第２発光部の光軸直交方向の間隔をＡ、前記第１発光部と前記第３発光部の光軸直交方向の間隔をＢとしたとき、以下の式（１７）を満たすことを特徴とする請求項１３に記載の光ピックアップ装置。
    ０．９×（λ２×｜ｍ｜）／（λ３×｜ｎ｜）≦Ａ／Ｂ≦１．１×
    　　　　　　　（λ２×｜ｍ｜）／（λ３×｜ｎ｜）　　　（１７）     The diffraction order of diffracted light generated when the second light beam enters the diffractive element is m, the diffraction order of diffracted light generated when the third light beam is incident on the diffractive element is n, and the first When the interval between the light emitting unit and the second light emitting unit in the optical axis orthogonal direction is A, and the interval between the first light emitting unit and the third light emitting unit in the optical axis orthogonal direction is B, the following equation (17) is obtained. The optical pickup device according to claim 13, wherein the optical pickup device is satisfied.
    0.9 × (λ2 × | m |) / (λ3 × | n |) ≦ A / B ≦ 1.1 ×
    (Λ2 × | m |) / (λ3 × | n |) (17)
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11134702A (en) * 1997-10-30 1999-05-21 Sanyo Electric Co Ltd Optical pickup device
JP2005327387A (en) * 2004-05-14 2005-11-24 Sanyo Electric Co Ltd Optical pickup apparatus
JP2008041234A (en) * 2006-07-10 2008-02-21 Ricoh Co Ltd Optical pickup and optical information processing device
JP2008052826A (en) * 2006-08-24 2008-03-06 Funai Electric Co Ltd Optical pickup device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11134702A (en) * 1997-10-30 1999-05-21 Sanyo Electric Co Ltd Optical pickup device
JP2005327387A (en) * 2004-05-14 2005-11-24 Sanyo Electric Co Ltd Optical pickup apparatus
JP2008041234A (en) * 2006-07-10 2008-02-21 Ricoh Co Ltd Optical pickup and optical information processing device
JP2008052826A (en) * 2006-08-24 2008-03-06 Funai Electric Co Ltd Optical pickup device

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