WO2011021474A1 - Optical pickup device - Google Patents

Optical pickup device Download PDF

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Publication number
WO2011021474A1
WO2011021474A1 PCT/JP2010/062478 JP2010062478W WO2011021474A1 WO 2011021474 A1 WO2011021474 A1 WO 2011021474A1 JP 2010062478 W JP2010062478 W JP 2010062478W WO 2011021474 A1 WO2011021474 A1 WO 2011021474A1
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WO
WIPO (PCT)
Prior art keywords
light
light beam
optical
pickup device
light receiving
Prior art date
Application number
PCT/JP2010/062478
Other languages
French (fr)
Japanese (ja)
Inventor
龍司 黒釜
博之 新藤
耕平 大田
Original Assignee
コニカミノルタオプト株式会社
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Application filed by コニカミノルタオプト株式会社 filed Critical コニカミノルタオプト株式会社
Priority to JP2011527617A priority Critical patent/JPWO2011021474A1/en
Publication of WO2011021474A1 publication Critical patent/WO2011021474A1/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
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1381—Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops
    • 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 an optical pickup device capable of recording and / or reproducing information in a manner compatible with different types of optical disks.
  • 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 the system to and from the recording density of an optical disk for recording / reproducing information is conceivable, but a plurality of optical systems are required, which is disadvantageous for miniaturization and increases 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.
  • 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.
  • each light emitting unit is shifted in the direction perpendicular to the optical axis. It is necessary to shift each light flux.
  • the light beam is shifted using a diffractive structure, but it is assumed that the interval between the light emitting points is accurately adjusted to a predetermined value.
  • Patent Document 3 discloses a light source in which three semiconductor lasers are housed in one package.
  • a so-called blue-violet semiconductor laser that emits a light beam having a wavelength 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 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). ).
  • 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.
  • 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.
  • the present invention has been made in consideration of the above-described problems, and an object of the present invention is to provide an optical pickup device capable of appropriately recording / reproducing information on three different types of optical disks while reducing the size and reducing the cost.
  • the optical pickup device 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
  • a spot is formed by condensing on the information recording surface of one optical disc, and information is recorded and / or reproduced on the first optical disc based on a signal from the photodetector that receives the reflected light.
  • a spot is formed by condensing the light beam from the second light emitting unit on the information recording surface of the second optical disk by the objective optical system, and the reflected light is received as a signal from the photodetector.
  • 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 from the second light emitting unit and the third light emitting unit.
  • the photodetector includes a first light receiving unit that receives the first light beam, a second light receiving unit that receives the second light beam, and a third light receiving unit that receives the third light beam,
  • a diffraction element through which the first light flux, the second light flux, and the third light flux pass in common is movably disposed in an optical path between the light source and the photodetector,
  • the diffractive element has a diffractive structure, and m-th order diffracted light generated when the first light beam enters the diffractive structure is received by the first light receiving unit, and the second light beam is The nth order diffracted light generated when the light enters is received by the second light receiving unit, and the nth order diffracted light generated when the third light beam is incident is received by the third light receiving unit.
  • m and n are arbitrary integers and m ⁇ n.
  • the optical axis shift amount of the diffracted light generated when the diffractive element is moved in the direction of the incident optical axis is sufficiently larger for the light beam having the wavelength ⁇ 3 than for the light beam having the wavelength ⁇ 1 when the light beam having the wavelength ⁇ 2 is considered as a reference. It can be said that it is small.
  • the position adjustment can be adjusted by moving the diffraction element in the optical axis direction. Even if the optical axis of the diffracted light having the wavelength ⁇ 1 is shifted, the light flux having the wavelength ⁇ 2 and the light beam having the wavelength ⁇ 3 are converged on the photodetector as compared with the change in the condensing spot interval between the light flux having the wavelength ⁇ 1 and the light beam having the wavelength ⁇ 2.
  • the change in the spot interval is small, and the light beam having the wavelength ⁇ 2 and the light beam having the wavelength ⁇ 3 can be guided to the second and third light receiving parts for the light beam having the wavelength ⁇ 2 and the light beam having the wavelength ⁇ 3, respectively, without a large positional shift. .
  • the diffractive element has a diffractive structure, and m-th order diffracted light generated when the first light beam enters the diffractive structure (desirably having the maximum light amount among the generated diffracted light).
  • the first light receiving unit receives light, and the nth order diffracted light generated when the second light beam is incident (desirably having the maximum light amount among the generated diffracted light) is the second light receiving.
  • the n-th order diffracted light generated when the third light beam is incident is received by the third light receiving section.
  • m and n are arbitrary integers and m ⁇ n, for example, an interval between the first light emitting unit, the second light emitting unit, and the third light emitting unit. Even when an error occurs in the diffraction element, the diffraction element is moved.
  • the m-th order diffracted light of the first light beam can be condensed on the photodetector, and the n-th order diffracted light of the second light beam and the n-order diffracted light of the third light beam are collected on the photodetector.
  • 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.
  • the optical pickup device is characterized in that, in the invention according to claim 1, the diffraction element is arranged to be movable at least in an optical axis direction of the optical pickup device.
  • the distance between the spot position of the second light flux and the spot position of the third light flux changes slightly, but this gap deviation is (when n ⁇ 0, Since the amount is small, there is little possibility of causing a problem in adjusting the distance between the spot position of the first light beam and the spot position of the second light beam.
  • the photodetector since the photodetector has signal extraction wiring and the like, it can be said that it is easier to adjust the deviation of the luminous flux by moving the diffraction element that does not have such wiring.
  • the term “movable” includes not only the case where the optical pickup device can be moved but also the case where the optical pickup device can be moved when the optical pickup device is assembled and is fixed to the optical pickup device by adhesion after adjustment. .
  • optical pickup device is characterized in that, in the invention according to claim 1 or 2, the following expression is satisfied.
  • the optical pickup device is the invention according to any one of claims 1 to 3, wherein the m-th order diffracted light among the diffracted light of the first light flux by the diffraction element has a maximum diffraction efficiency, Of the diffracted lights of the second light flux and the third light flux, the nth-order diffracted light has the maximum diffraction efficiency. As a result, a sufficient amount of light flux received by the photodetector can be secured.
  • n 0.
  • the intervals between the light emitting elements of the light beam having the wavelength ⁇ 2 and the light beam having the wavelength ⁇ 3 arranged with high accuracy are reproduced as they are with high accuracy in the light receiving unit, and the light beam with the wavelength ⁇ 1 from the first light emitting unit having a large positional variation is accurately wavelength ⁇ 1.
  • An optical pickup device is characterized in that, in the invention according to any one of the first to fifth aspects, the diffraction element is disposed in an optical path from the light source to the objective optical system. To do.
  • the optical pickup device according to any one of the first to fifth aspects, further comprising a light beam separating element for separating the reflected light from the optical disk and the light beam emitted from the light source.
  • the diffraction element is disposed between the light beam separation element and the photodetector.
  • the optical pickup device according to any one of the first to seventh aspects, wherein the objective optical system includes a single objective lens.
  • An optical pickup device is the invention according to any one of the first to seventh aspects, wherein the objective optical system includes a first objective lens that focuses the first light flux on the first optical disc; And a second objective lens for condensing the second light beam on the second optical disk and condensing the third light beam on the third optical disk.
  • the second objective lens is made different from the first objective lens, and the second By using a dedicated design for the light beam and the third light beam, further reduction in the light amount of the second light beam or the third light beam can be suppressed.
  • the objective optical system condenses the first light flux on the first optical disc and the second light flux. It has a 1st objective lens which condenses on the said 2nd optical disk, and a 2nd objective lens which condenses the said 3rd light beam on the said 3rd optical disk, It is characterized by the above-mentioned.
  • the second objective lens is made different from the first objective lens, By doing so, the further light quantity fall of the said 2nd light beam or the said 3rd light beam can be suppressed.
  • the optical pickup device is the optical pickup device according to any one of claims 1 to 10, wherein the first light receiving unit, the second light receiving unit, and the third light receiving unit are the optical pickup device. It is characterized by being arranged at different positions in the direction crossing the optical axis. Thereby, each light beam can be condensed for each light receiving part.
  • An optical pickup device is the optical pickup device according to any one of the first to eleventh aspects, wherein the first light flux is received by the second light receiving portion or the third light receiving portion.
  • One light-receiving portion is also used. Thereby, a photodetector can be made more compact.
  • An optical pickup device is the invention according to any one of the first to eleventh aspects, wherein the first light receiving unit, the second light receiving unit, and the third light receiving unit are a common light receiving unit. It is characterized by.
  • the diffractive structure referred to in this specification is a general term for structures that have a step and have a function of converging or diverging a light beam by diffraction.
  • it is configured by arranging a plurality of unit shapes, a light beam is incident on each unit shape, and the wavefront of the transmitted light is shifted by approximately an integer wavelength or an integer wavelength for each adjacent annular zone.
  • It includes a structure that collects light by forming a simple wavefront.
  • the diffractive structure preferably has a plurality of steps, and the steps may be arranged with a periodic interval in the direction perpendicular to the optical axis, or may be arranged with a non-periodic interval in the direction perpendicular to the optical axis.
  • the diffractive structure preferably has a groove extending linearly along a plane orthogonal to the optical axis. Furthermore, the diffractive structure can take various cross-sectional shapes (cross-sectional shapes in a plane including the optical axis), and the cross-sectional shape including the optical axis is roughly classified into a blazed structure and a staircase structure.
  • the diffractive structure is preferably 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”.
  • 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 schematically the structure of optical pick-up apparatus PU1 of this Embodiment which can record and / or reproduce
  • optical pick-up apparatus PU2 of this Embodiment which can record and / or reproduce
  • optical pick-up apparatus PU3 of this Embodiment which can record and / or reproduce
  • FIG. 8 It is the figure which looked at the light-receiving surface of photodetector PD 'shown in FIG. 8 in the arrow IX direction. It is the schematic which shows the relationship between the position of 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
  • the first light receiving unit, the second light receiving unit, and the third light receiving unit are shared by the common light receiving unit 32R, the light having the diffraction element DE ′ disposed between the light source unit LDP and the objective lens OBJ as another position. It is the schematic of a pick-up apparatus.
  • FIG. 1 is a diagram schematically showing a configuration of an optical pickup apparatus 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. 2 is a view of the light receiving surface of the photodetector PD shown in FIG. 1 as viewed in the direction of arrow II, 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 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 third semiconductor laser LD3 (third light emitting unit) that emits a light beam), a light source unit LDP housed in one package, and a group that divides an incident light beam into three parts.
  • Computing GRT, sensor lens SN, the diffraction element DE having a diffractive structure comprises a photodetector PD, and the like.
  • the second semiconductor laser LD2 and the third semiconductor laser LD3 are formed on the same chip of the Ga-based semiconductor substrate (monolithic configuration), and the first semiconductor laser LD1 is formed on a chip of a different nitride-based semiconductor substrate. Yes (hybrid configuration).
  • An example of such a light source is disclosed in Japanese Patent Application Laid-Open No. 2004-319915.
  • the first semiconductor laser LD1 and the second semiconductor laser LD2 and the third semiconductor laser LD3 are formed are separate, the first semiconductor laser LD1 and the second semiconductor laser
  • the distance between the LD2 and the third semiconductor laser LD3 in the direction perpendicular to the optical axis is not stable, and the distance tends to vary.
  • the diffractive element DE generates the first-order diffracted light as the diffracted light having the highest light amount when the first light beam is incident, and the 0th-order diffracted light as the diffracted light having the highest light amount when the second and third light beams are incident.
  • the generated diffraction structure 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 in the vertical and horizontal directions, and the received light amounts are 1e, 1c, 1f, and 1d, respectively.
  • the light receiving portions 11R and 13R on both sides of the light receiving portion 12R are divided into left and right parts, and the received light amounts are 1h, 1g, and 1b, 1a, respectively.
  • the light receiving unit 22R is divided into four parts, top, bottom, left, and right, and the amounts of light received 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 the received light amounts are 2h, 2g, 2b and 2a, respectively.
  • the light receiving unit 32R is divided into four parts in the vertical and horizontal directions, and the received light amounts are 3e, 3c, 3f, and 3d, respectively.
  • the light receiving portions 31R and 33R on both sides of the light receiving portion 32R are divided into left and right parts, and the received light amounts are 3h, 3g, 3b, and 3a, respectively.
  • the light beam passing through the COL, converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, the diameter of the light beam being regulated by a diaphragm (not shown), and further condensed by the objective lens OBJ has a thickness of 0.1 mm. It becomes a spot formed on the information recording surface of the BD through the protective substrate.
  • 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).
  • the sensor lens SN is a concave lens that is inclined with respect to the optical axis.
  • 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 light beam that has passed through the collimator lens COL, converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, is regulated by a diaphragm (not shown), and is condensed by the objective lens OBJ. It becomes a spot formed on the information recording surface of the DVD through a protective substrate having a thickness of 0.6 mm.
  • 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 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. 3 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, but each light beam is shown by a line for easy understanding.
  • the distance between the first semiconductor laser and the second semiconductor laser is larger than the reference value, and the second-order light beam and the zero-order diffracted light of the third light beam that have passed through the diffraction element DE are respectively
  • the optical system is set so as to be positioned at the center of the light receiving parts 22R and 32R, the first-order diffracted light of the first light beam may be condensed above the light receiving part 12R, 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 second light beam and the third light beam that has passed through the diffraction element DE is In contrast, the first-order diffracted light of the first light flux approaches the center of the light receiving unit 12R. 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 first light beam is condensed below the light receiving unit 12R, the diffractive element DE may be moved away from the photodetector PD.
  • the following adjustment is performed in a state where the optical pickup device is temporarily assembled.
  • the second light beam grating GRT is rotated around the optical axis so that the TE signal is maximized.
  • the grating GRT can be individually adjusted for the first light flux, the second light flux, and the third light flux (not shown).
  • the main beam has a circular diameter at the center of the four divisions of the light receiving unit 12R.
  • the position is adjusted by displacing the diffractive element DE in the optical axis direction so as to be a spot (that is, the output signals 1c, 1d, 1e, and 1f are equal and the sum signal thereof is maximized).
  • FIG. 4 is a schematic view of an optical pickup device in which the diffraction element DE is arranged between the light source unit LDP and the objective lens OBJ as another position.
  • a cube-type polarizing beam splitter is used as the polarizing beam splitter PBS.
  • the arrangement of the grating GRT and the light source unit LDP, the sensor lens SN, the diffraction element DE, and the photodetector PD in the optical pickup device shown in FIG. 1 is switched. Further, some elements are omitted, and each light flux is shown by a line for easy understanding.
  • the 0th-order diffracted light of the second light flux and the third light flux that have passed through the diffraction element DE is Each passes through the polarization beam splitter PBS, is focused on the optical disk (BD / DVD / CD) by the objective lens OBJ, and the reflected light passes through the objective lens OBJ, is reflected by the polarization beam splitter PBS, and is reflected on the photodetector PD. If the optical system is set so as to be positioned at the center of the light receiving parts 22R and 32R, the first-order diffracted light of the first light beam may be condensed above the light receiving part 12R, and an inappropriate signal may be output.
  • the diffractive element DE when the diffraction element DE is moved away from the objective lens OBJ, the optical paths of the 0th-order diffracted light of the second light beam and the third light beam that have passed through the diffraction element DE are changed. In contrast, the first-order diffracted light of the first light flux approaches the center of the light receiving unit 12R. That is, by moving the diffractive element DE relative to the objective lens OBJ, all the light beams can be appropriately condensed on the light receiving part. When the first-order diffracted light of the first light beam is condensed below the light receiving unit 12R, the diffractive element DE may be moved so as to approach the objective lens OBJ.
  • the first-order diffracted light is generated as the diffracted light having the highest light amount when the first light beam is incident, and the diffraction having the highest light amount is performed when the second light beam and the third light beam are incident.
  • a diffractive structure that generates ⁇ 1st order diffracted light as light is formed on the surface will be described.
  • FIG. 5 shows the relationship between the position of the modified example of the diffraction element DE disposed between the photodetector PD and the polarization beam splitter PBS and the light receiving position of each light beam in the photodetector PD, as in FIG. Although it is a schematic view, each light beam is shown by a line for easy understanding.
  • the ⁇ 1st order diffracted light of the second light beam and the third light beam is bent so as to pass through the diffraction element DE and away from the optical axis (S2, S3).
  • the first-order diffracted light of the first light beam is bent so as to pass through the diffraction element DE and away from the optical axis (S1).
  • L12 be the focal spot interval between the first and second luminous fluxes
  • L23 be the focal spot interval between the second and third luminous fluxes.
  • the optical system is set so that the next-order diffracted light is positioned at the center of each of the light receiving portions 22R and 32R, the first-order diffracted light of the first light beam is condensed above the light receiving portion 12R, and an inappropriate signal is output. There is a risk.
  • the first-order diffracted light of the first light flux approaches the center of the light receiving unit 12R (S1 ′), and the condensing spot interval between the first light flux and the second light flux after the movement of the diffraction element DE becomes smaller (S1 ′).
  • the diffractive element DE is separated from the light detector PD and the light detector PD is moved in the direction perpendicular to the optical axis (in this case). To the lower).
  • FIG. 6 is a schematic diagram of an optical pickup device in which a modification of the diffraction element DE is arranged between the light source unit LDP and the objective lens OBJ.
  • a cube-type polarizing beam splitter is used as the polarizing beam splitter PBS.
  • the arrangement of the grating GRT and the light source unit LDP, the sensor lens SN, the diffraction element DE, and the photodetector PD in the optical pickup device shown in FIG. 1 is switched. Further, some elements are omitted, and each light flux is shown by a line for easy understanding.
  • the ⁇ 1st order diffracted light of the second light flux and the third light flux that have passed through the diffraction element DE is ,
  • Each passing through the polarizing beam splitter PBS, condensed on the optical disc (BD / DVD / CD) by the objective lens OBJ, and the reflected light passes through the objective lens OBJ and reflected by the polarizing beam splitter PBS, and is detected by the photodetector PD.
  • the optical system is set so as to be positioned at the center of the light receiving portions 22R and 32R, the first-order diffracted light of the first light beam is condensed above the light receiving portion 12R, and an inappropriate signal may be output. .
  • the diffraction element DE is moved away from the objective lens OBJ, and the photodetector PD is moved in the direction perpendicular to the optical axis (in this case, upward). All the light beams can be appropriately condensed on the light receiving part.
  • the diffractive element DE is separated from the objective lens OBJ and the photodetector PD is moved in the direction orthogonal to the optical axis (in this case). May be moved downward).
  • FIG. 7 is a diagram schematically showing a configuration of the optical pickup device PU2 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 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 present embodiment only differences from the above-described embodiment will be described, and the description of the common components will be omitted by attaching the same reference numerals.
  • 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 first objective lens OBJ1 is inserted into the optical path of the optical pickup device.
  • 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 objective lens OBJ by an objective lens actuator (not shown).
  • the second objective lens OBJ2 is inserted into the optical path of the optical pickup device.
  • the light beam passing through the lens COL converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, the diameter of the light beam being regulated by a diaphragm (not shown), and further condensed by the second objective lens OBJ2 has a thickness of It becomes a spot formed on the information recording surface of the DVD through a 0.6 mm protective substrate.
  • 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.
  • the objective lens OBJ is focused and tracked by an unillustrated objective lens actuator, whereby the 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 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. 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.
  • 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.
  • FIG. 8 is a diagram schematically showing a configuration of the optical pickup device PU3 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 PU3 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 diffraction grating DE 'and the photodetector PD' are different from the embodiment of FIG.
  • Other configurations are the same as those in the above-described embodiment, and thus the same reference numerals are used and description thereof is omitted.
  • the difference is that the diffraction grating DE ′ in the present embodiment generates ⁇ 1st order diffracted light (bent in a direction approaching the third light beam) as diffracted light having the highest light amount when the first light beam is incident.
  • a diffractive structure that generates zero-order diffracted light as the diffracted light having the highest light amount when the second light flux and the third light flux are incident 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 21R to 33R arranged in 2 rows and 3 columns on the light receiving surface side substantially orthogonal to the optical axis, so that it is more compact than the configuration of FIG. ing.
  • the light receiving units 21R to 23R are second light receiving units that receive the reflected light from the DVD, and the light receiving units 31R to 33R are the third light receiving units (also serving as both the reflected light from the BD and the reflected light from the CD). 1st light-receiving part).
  • the light receiving unit 22R is divided into four parts, top, bottom, left, and right, and the amounts of light received are 2e, 2c, 2f, and 2d, respectively.
  • the light receiving portions 21R and 23R on both sides of the light receiving portion 22R are not divided, and the amounts of received light are 2b and 2a, respectively. Further, the light receiving unit 32R is divided into four parts, top, bottom, left, and right, and the amounts of received light are 13e, 13c, 13f, and 13d, respectively.
  • the light receiving portions 31R and 33R on both sides of the light receiving portion 32R are not divided, and the amounts of received light are 13b and 13a, respectively.
  • the light spot near the light receiving part 32R means reflected light from the BD
  • the light spot far from the light receiving part 32R means reflected light from the CD. To do.
  • the light beam passing through the COL, converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, the diameter of the light beam being regulated by a diaphragm (not shown), and further condensed by the objective lens OBJ has a thickness of 0.1 mm. It becomes a spot formed on the information recording surface of the BD through the protective substrate.
  • 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 are converged on the light receiving portions 31R to 33R 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 (13c + 13f) ⁇ (13e + 13d), and the objective lens OBJ is focused by the objective lens actuator so that this becomes close to zero.
  • the tracking servo uses the 3-beam method.
  • the TE signal is obtained by (13a-13b), 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 (13a + 13b + 13c + 13d + 13e + 13f).
  • the light beam that has passed through the collimator lens COL, converted from linearly polarized light to circularly polarized light by the ⁇ / 4 wave plate QWP, is regulated by a diaphragm (not shown), and is condensed by the objective lens OBJ. It becomes a spot formed on the information recording surface of the DVD through a protective substrate having a thickness of 0.6 mm.
  • 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 3-beam method.
  • the TE signal is obtained by (2a-2b), 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).
  • 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 (13c + 13f) ⁇ (13e + 13d), and the objective lens OBJ is focused by the objective lens actuator so that this becomes close to zero.
  • the tracking servo uses the 3-beam method.
  • the TE signal is obtained by (13a-13b), 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 (13a + 13b + 13c + 13d + 13e + 13f).
  • 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 21R to 33R of the photodetector PD ' cannot be shifted. Therefore, if the interval between the semiconductor lasers exceeds the allowable error, each light beam cannot be properly received by the light receiving portions 21R to 33R. Therefore, in the present embodiment, such a problem is solved as follows.
  • FIG. 10 is a schematic diagram showing the relationship between the position of the diffractive element DE 'and the light receiving position of each light beam in the photodetector PD', but each light beam is shown by a line for easy understanding.
  • the distance between the first semiconductor laser and the second semiconductor laser is larger than the reference value, and the 0th-order diffracted lights B2 and B3 of the second light flux and the third light flux that have passed through the diffractive element DE ′ are obtained. If the optical system is set so as to be positioned at the center of each of the light receiving portions 22R and 32R, the ⁇ 1st order diffracted light B1 of the first light beam is condensed below the light receiving portion 32R, and an inappropriate signal is output. There is a fear.
  • the diffractive element DE ′ when the diffraction element DE ′ is moved so as to approach the photodetector PD ′, the 0th-order diffracted light of the second light beam and the third light beam that have passed through the diffraction element DE ′. While the optical paths of B2 and B3 are not changed, the ⁇ 1st order diffracted light B1 of the first light flux comes closer to the center of the light receiving part 32R. 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 parts. When the ⁇ 1st order diffracted light B1 of the first light beam is condensed above the light receiving portion 32R, the diffractive element DE ′ may be moved away from the photodetector PD ′.
  • FIG. 11 is a schematic diagram 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.
  • a cube-type polarizing beam splitter is used as the polarizing beam splitter PBS.
  • the arrangement of the grating GRT and the light source unit LDP, the sensor lens SN, the diffraction element DE, and the photodetector PD in the optical pickup device shown in FIG. 8 is switched. Further, some elements are omitted, and each light flux is shown by a line for easy understanding.
  • the 0th-order diffracted light B2 of the second light flux and the third light flux that have passed through the diffraction element DE ′. , B3 pass through the polarization beam splitter PBS, and are collected on the optical disk (BD / DVD / CD) by the objective lens OBJ, and the reflected light passes through the objective lens OBJ, and is reflected by the polarization beam splitter PBS, and the light.
  • the optical system is set so that it is positioned at the center of the light receiving portions 22R and 32R of the detector PD, the ⁇ 1st order diffracted light B1 of the first light beam is condensed below the light receiving portion 32R, and an inappropriate signal is output. There is a fear.
  • the diffractive element DE ′ when the diffractive element DE ′ is moved away from the objective lens OBJ, the 0th-order diffracted light B2 of the second light flux and the third light flux that have passed through the diffractive element DE ′ is obtained. While the optical path of B3 does not change, the ⁇ 1st order diffracted light B1 of the first light flux comes closer to the center of the light receiving part 32R. That is, by moving the diffractive element DE ′ relative to the objective lens OBJ, all the light beams can be appropriately condensed on the light receiving part. If the ⁇ 1st order diffracted light B1 of the first light beam is condensed above the light receiving portion 32R, the diffractive element DE ′ may be moved so as to approach the objective lens OBJ.
  • the first light beam and the third light beam are commonly received by the third light receiving unit.
  • the first light beam and the second light beam may be commonly received by the second light receiving unit.
  • tracking servo may be performed by the DPP method as in the above-described embodiment. Further, when the second light beam and the third light beam are made incident on the diffractive element DE ', diffracted light other than the 0th order (where n ⁇ m) may be generated.
  • first light receiving unit, the second light receiving unit, and the third light receiving unit may be a common light receiving unit.
  • FIG. 12 shows the position of the diffraction element DE ′ and the light receiving position of each light beam in the photodetector PD ′ when the first light receiving unit, the second light receiving unit, and the third light receiving unit are shared by the common light receiving unit 32R. It is the schematic which shows these relationships.
  • an optical element DE ′′ that diffracts only the second light flux of ⁇ 2 is arranged on the light source side of the diffraction element DE ′.
  • the diffractive element DE ′ when the diffractive element DE ′ is moved closer to the photodetector PD ′, the 0th-order diffracted light of the second light flux and the third light flux that have passed through the diffractive element DE ′. While the optical paths of B2 and B3 are not changed, the ⁇ 1st order diffracted light B1 of the first light flux comes closer to the center of the light receiving part 32R. That is, by moving the diffractive element DE ′ relative to the photodetector PD ′, it is possible to appropriately collect all the light beams on the light receiving unit 32R. When the ⁇ 1st order diffracted light B1 of the first light beam is condensed above the light receiving portion 32R, the diffractive element DE ′ may be moved away from the photodetector PD ′.
  • FIG. 13 is a schematic view of an optical pickup device in which the diffraction element DE ′ is disposed between the light source unit LDP and the objective lens OBJ as another position.
  • an optical element DE ′′ that diffracts only the second light flux of ⁇ 2 is arranged between the photodetector PD ′ and the polarization beam splitter PBS.
  • the polarizing beam splitter PBS is a cube-shaped polarizing beam splitter
  • the optical pickup device shown in Fig. 8 includes a grating GRT and a light source unit LDP, a sensor lens SN, a diffraction element DE, and a photodetector PD. Also, some of the elements are omitted, and each light beam is indicated by a line for easy understanding.
  • Next-order diffracted beams B2 and B3 pass through the polarizing beam splitter PBS, and are focused on the optical disc (BD / DVD / CD) by the objective lens OBJ.
  • the reflected light passes through the objective lens OBJ and is reflected by the polarizing beam splitter PBS.
  • the optical system is set so as to be positioned at the center of the light receiving portion 32R of the photodetector PD, the ⁇ 1st order diffracted light B1 of the first light beam is condensed below the light receiving portion 32R, and an inappropriate signal is generated. There is a risk of output.
  • the diffractive element DE ′ when the diffractive element DE ′ is moved away from the objective lens OBJ, the 0th-order diffracted light B2 of the second light flux and the third light flux that have passed through the diffractive element DE ′ are obtained. While the optical path of B3 does not change, the ⁇ 1st order diffracted light B1 of the first light flux comes closer to the center of the light receiving part 32R. That is, by moving the diffractive element DE 'relative to the objective lens OBJ, all the light beams can be appropriately condensed on the light receiving unit 32R. If the ⁇ 1st order diffracted light B1 of the first light beam is condensed above the light receiving portion 32R, the diffractive element DE ′ may be moved so as to approach the objective lens OBJ.
  • Table 1 shows data of the examples.
  • the diffractive element of the example has a straight four-step stair-like diffraction structure formed on a parallel plate.
  • the step difference of the stepped diffraction structure with respect to the zeroth order diffracted light Is a positive (+) order diffracted light, and an outgoing light beam bent to the opposite side (left side in the table) is negative (- ) Order diffraction light.
  • dor 8.25.
  • the lateral pitch can be arbitrarily changed according to the desired emission angle.
  • the first-order diffracted light has the highest intensity when a light beam with wavelength ⁇ 1 is incident, and the zero-order diffracted light has the highest intensity when light beams with wavelengths ⁇ 2 and ⁇ 3 are incident.

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Abstract

Provided is an optical pickup device by which appropriate recording/reproducing of information to three different types of optical disks is possible, while downsizing the device and suppressing the cost. When a diffractive element (DE) is moved to closer an optical detector (PD), light paths of the 0-order diffracted light of a second light flux and a third light flux which have passed the diffractive element (DE) do not change, while the primary diffracted light of a first light flux approaches the center of a light receiving portion (12R). Namely, by moving the diffractive element (DE) relative to the optical detector (PD), all light fluxes can be appropriately gathered to the light receiving portion, respectively.

Description

光ピックアップ装置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／又は再生を行える光ピックアップ装置に関する。 The present invention relates to an optical pickup device capable of recording and / or reproducing information in a manner compatible with different types of optical disks.
　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研究・開発が急速に進んでいる。一例として、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, research and development of high-density optical disc systems that can record and / or reproduce 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. Development is progressing rapidly. As an example, in an optical disc for recording / reproducing information with specifications of NA 0.85 and light source wavelength 405 nm, so-called Blu-ray Disc (hereinafter referred to as BD), DVD (NA 0.6, light source wavelength 650 nm, storage capacity 4.7 GB) It is possible to record 25 GB of information per layer on an optical disc having a diameter of 12 cm which is the same size as the above.
　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の記録密度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 the system to and from the recording density of an optical disk for recording / reproducing information is conceivable, but a plurality of optical systems are required, which is disadvantageous for miniaturization and increases the cost.
　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.
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
　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、回折構造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 beam is shifted using a diffractive structure, but it is assumed that the interval between the light emitting points is accurately adjusted to a predetermined value.
　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。特許文献３によれば、４０５ｎｍ前後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。 On the other hand, Patent Document 3 discloses a light source in which three semiconductor lasers are housed in one package. According to Patent Document 3, a so-called blue-violet semiconductor laser that emits a light beam having a wavelength 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.
　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を提供することを目的とする。 The present invention has been made in consideration of the above-described problems, and an object of the present invention is to provide an optical pickup device capable of appropriately recording / reproducing information on three different types of optical disks while reducing the size and reducing the cost. And
　請求項１に記載の光ピックアップ装置は、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、光検出器とを有し、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おいて、
　前記光源は、前記第２発光部と前記第３発光部が同一のチップ上に形成され、前記第１発光部が、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、
　前記光検出器は、前記第１光束を受光する第１受光部と、前記第２光束を受光する第２受光部と、前記第３光束を受光する第３受光部とを有し、
　前記光源と前記光検出器との間の光路内に、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が移動可能に配置されており、
　前記回折素子は回折構造を有し、前記回折構造に前記第１光束が入射したときに発生するｍ次回折光が前記第１受光部に受光されるようになっており、また前記第２光束が入射したときに発生するｎ次回折光が前記第２受光部に受光されるようになっており、更に前記第３光束が入射したときに発生するｎ次回折光が前記第３受光部に受光されるようになっている（但し、ｍ、ｎは任意の整数であってｍ≠ｎ）ことを特徴とする。 The optical pickup device 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 A light source including a third light-emitting unit that emits a third light beam of <λ3), an objective optical system, and a photodetector, and the light beam from the first light-emitting unit is generated by the objective optical system. A spot is formed by condensing on the information recording surface of one optical disc, and information is recorded and / or reproduced on the first optical disc based on a signal from the photodetector that receives the reflected light. A spot is formed by condensing the light beam from the second light emitting unit on the information recording surface of the second optical disk by the objective optical system, and the reflected light is received as a signal from the photodetector. Based on the recording of information on the second optical disc and / or Performs reproduction, forms a spot by condensing the light beam from the third light emitting unit on the information recording surface of the third optical disk by the objective optical system, and receives the reflected light from the photodetector. In the optical pickup device for recording and / or reproducing information with respect to the third optical disc based on the signal of
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 different chip from the second light emitting unit and the third light emitting unit. And
The photodetector includes a first light receiving unit that receives the first light beam, a second light receiving unit that receives the second light beam, and a third light receiving unit that receives the third light beam,
A diffraction element through which the first light flux, the second light flux, and the third light flux pass in common is movably disposed in an optical path between the light source and the photodetector,
The diffractive element has a diffractive structure, and m-th order diffracted light generated when the first light beam enters the diffractive structure is received by the first light receiving unit, and the second light beam is The nth order diffracted light generated when the light enters is received by the second light receiving unit, and the nth order diffracted light generated when the third light beam is incident is received by the third light receiving unit. Where m and n are arbitrary integers and m ≠ n.
　本発明の原理を説明する。ピッチｄの回折構造に波長λの光が入射すると入射光軸に対してθ方向（θ＝回折角）への回折光が発生するが、これらの関係はｓｉｎθ＝ｋλ／ｄで与えられる。ここでｋは整数で回折次数を意味する。波長λ２の光束と波長λ３の光束については、光検出器に導かれる回折光が同一次数（ｎ次）であるため回折角の差が小さく出射方向が近くなる。これに対し、ｍ次光の波長λ１の光束は次数が異なるため、波長λ２の光束と波長λ３の光束の回折方向とは大きく異なる。このため、回折素子を入射光軸方向に移動した場合に発生する回折光の光軸シフト量は、波長λ２の光束を基準にして考えれば、波長λ３の光束の方が波長λ１の光束より十分小さいといえる。従って波長λ１、λ２、λ３の光束、それぞれの受光位置が定められた光検出器の受光部に対して、発光位置のバラツキの大きい第１発光部からの波長λ１の光束の受光部上での位置調整を、回折素子を光軸方向に移動することによって調整することができる。この波長λ１の回折光の光軸をシフトしても、光検出器上において波長λ１の光束と波長λ２の光束の集光スポット間隔変化に較べ、波長λ２の光束と波長λ３の光束の集光スポット間隔変化は小さなものですみ、波長λ２の光束と波長λ３の光束それぞれを、波長λ２の光束と波長λ３の光束用の第２，第３受光部に大きな位置ずれを伴わず導くことができる。 The principle of the present invention will be described. When light of wavelength λ enters the diffractive structure of pitch d, diffracted light is generated in the θ direction (θ = diffraction angle) with respect to the incident optical axis, and these relationships are given by sin θ = kλ / d. Here, k is an integer and means a diffraction order. For the light beam with wavelength λ 2 and the light beam with wavelength λ 3, the difference in diffraction angle is small and the emission direction is close because the diffracted light guided to the photodetector has the same order (nth order). On the other hand, since the light beams of the wavelength λ1 of the m-th order light have different orders, the diffraction directions of the light beam of the wavelength λ2 and the light beam of the wavelength λ3 are greatly different. For this reason, the optical axis shift amount of the diffracted light generated when the diffractive element is moved in the direction of the incident optical axis is sufficiently larger for the light beam having the wavelength λ3 than for the light beam having the wavelength λ1 when the light beam having the wavelength λ2 is considered as a reference. It can be said that it is small. Therefore, the light beams of wavelengths λ1, λ2, and λ3, and the light receiving portion of the light beam having the wavelength λ1 from the first light emitting portion having a large variation in the light emitting position with respect to the light receiving portion of the photodetector in which the respective light receiving positions are determined. The position adjustment can be adjusted by moving the diffraction element in the optical axis direction. Even if the optical axis of the diffracted light having the wavelength λ1 is shifted, the light flux having the wavelength λ2 and the light beam having the wavelength λ3 are converged on the photodetector as compared with the change in the condensing spot interval between the light flux having the wavelength λ1 and the light beam having the wavelength λ2. The change in the spot interval is small, and the light beam having the wavelength λ2 and the light beam having the wavelength λ3 can be guided to the second and third light receiving parts for the light beam having the wavelength λ2 and the light beam having the wavelength λ3, respectively, without a large positional shift. .
　本発明によれば、前記回折素子は回折構造を有し、前記回折構造に前記第１光束が入射したときに発生するｍ次回折光（発生する回折光のうち最大の光量を有すると望ましい）が前記第１受光部に受光されるようになっており、また前記第２光束が入射したときに発生するｎ次回折光（発生する回折光のうち最大の光量を有すると望ましい）が前記第２受光部に受光されるようになっており、更に前記第３光束が入射したときに発生するｎ次回折光（発生する回折光のうち最大の光量を有すると望ましい）が前記第３受光部に受光されるようになっている（但し、ｍ、ｎは任意の整数であってｍ≠ｎ）ので、例えば、前記第１発光部と、前記第２発光部及び前記第３発光部との間の間隔に誤差が生じた場合でも、前記回折素子を移動させることによって、前記第１光束のｍ次回折光を前記光検出器に集光させることができると共に、前記第２光束のｎ次回折光及び前記第３光束のｎ次ぎ回折光を前記光検出器に集光させることができる。尚、前記第２発光部及び前記第３発光部とは同一チップに形成され、前記第１発光部はそれとは別なチップに形成されている。 According to the present invention, the diffractive element has a diffractive structure, and m-th order diffracted light generated when the first light beam enters the diffractive structure (desirably having the maximum light amount among the generated diffracted light). The first light receiving unit receives light, and the nth order diffracted light generated when the second light beam is incident (desirably having the maximum light amount among the generated diffracted light) is the second light receiving. The n-th order diffracted light generated when the third light beam is incident (preferably having the maximum light quantity among the generated diffracted lights) is received by the third light receiving section. Since m and n are arbitrary integers and m ≠ n, for example, an interval between the first light emitting unit, the second light emitting unit, and the third light emitting unit. Even when an error occurs in the diffraction element, the diffraction element is moved. Thus, the m-th order diffracted light of the first light beam can be condensed on the photodetector, and the n-th order diffracted light of the second light beam and the n-order diffracted light of the third light beam are collected on the photodetector. Can be lighted. 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.
　請求項２に記載の光ピックアップ装置は、請求項１に記載の発明において、前記回折素子は、少なくとも前記光ピックアップ装置の光軸方向に移動可能に配置されていることを特徴とする。 The optical pickup device according to claim 2 is characterized in that, in the invention according to claim 1, the diffraction element is arranged to be movable at least in an optical axis direction of the optical pickup device.
　例えば、前記回折素子を光ピックアップ装置に固定した場合でも、前記光検出器を光ピックアップ装置の光軸方向に移動させることで、前記光検出器上における前記第１光束のスポット位置と、前記第２光束及び前記第３光束のスポット位置との間隔を調整することは可能である。かかる場合、たとえ前記第２光束と前記第３光束の０次回折光を用いた（ｎ＝０）としても、両光束の受光部への光軸は若干非平行であるため、前記光検出器を光ピックアップ装置の光軸方向に移動させたとき、前記第２光束のスポット位置と前記第３光束のスポット位置との間隔が若干変化するが、この間隔ずれは（ｎ≠０で或る場合に比べ）わずかな量であるから、前記第１光束のスポット位置と前記第２光束のスポット位置との間隔調整に当たって問題となる恐れが少ない。しかし、光検出器は信号取り出し用の配線等を有するので、このような配線を有しない回折素子を移動させた方が光束のズレ調整は容易であるといえる。尚、「移動可能」とは、光ピックアップ装置の組み付け後に移動可能である場合の他、光ピックアップ装置の組み付け時に移動可能であって、調整後に接着等で光ピックアップ装置に固定される場合も含む。 For example, even when the diffractive element is fixed to an optical pickup device, the spot position of the first light beam on the photodetector and the first position can be obtained by moving the photodetector in the optical axis direction of the optical pickup device. It is possible to adjust the distance between the spot positions of the two light beams and the third light beam. In this case, even if the 0th-order diffracted light of the second light flux and the third light flux is used (n = 0), the optical axis to the light receiving part of both light fluxes is slightly non-parallel. When the optical pickup device is moved in the optical axis direction, the distance between the spot position of the second light flux and the spot position of the third light flux changes slightly, but this gap deviation is (when n ≠ 0, Since the amount is small, there is little possibility of causing a problem in adjusting the distance between the spot position of the first light beam and the spot position of the second light beam. However, since the photodetector has signal extraction wiring and the like, it can be said that it is easier to adjust the deviation of the luminous flux by moving the diffraction element that does not have such wiring. The term “movable” includes not only the case where the optical pickup device can be moved but also the case where the optical pickup device can be moved when the optical pickup device is assembled and is fixed to the optical pickup device by adhesion after adjustment. .
　請求項３に記載の光ピックアップ装置は、請求項１又は２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 optical pickup device according to claim 3 is characterized in that, in the invention according to claim 1 or 2, the following expression is satisfied.
　３９５（ｎｍ）≦λ１≦４１５（ｎｍ）　　　（１）
　６３０（ｎｍ）≦λ２≦７００（ｎｍ）　　　（２）
　７５０（ｎｍ）≦λ３≦８５０（ｎｍ）　　　（３）
　請求項４に記載の光ピックアップ装置は、請求項１～３のいずれかに記載の発明において、前記回折素子による前記第１光束の回折光のうちｍ次回折光が最大の回折効率を有し、前記第２光束および前記第３光束の回折光のうちｎ次回折光が最大の回折効率を有することを特徴とする。これにより前記光検出器に受光される光束の光量を十分に確保できる。 395 (nm) ≦ λ1 ≦ 415 (nm) (1)
630 (nm) ≦ λ2 ≦ 700 (nm) (2)
750 (nm) ≦ λ3 ≦ 850 (nm) (3)
The optical pickup device according to claim 4 is the invention according to any one of claims 1 to 3, wherein the m-th order diffracted light among the diffracted light of the first light flux by the diffraction element has a maximum diffraction efficiency, Of the diffracted lights of the second light flux and the third light flux, the nth-order diffracted light has the maximum diffraction efficiency. As a result, a sufficient amount of light flux received by the photodetector can be secured.
　請求項５に記載の光ピックアップ装置は、請求項１～４のいずれかに記載の発明において、ｎ＝０であることを特徴とする。特にｎ＝０の場合は、波長λ２の光束および波長λ３の光束は回折素子によって回折が生じないことを意味する。したがって回折素子を入射光軸方向に移動させても波長λ２の光束および波長λ３の光束の光軸の方向に変化は発生せず、波長λ１の光束だけの光軸角度調整を独立的に行うことができる。この結果、精度よく配置された波長λ２の光束および波長λ３の光束の発光素子間隔はそのまま精度よく受光部で再現され、位置ばらつきの大きい第１発光部からの波長λ１の光束を正確に波長λ１の光束用の第１受光部に導くことができる。 The optical pickup device according to claim 5 is the invention according to any one of claims 1 to 4, wherein n = 0. In particular, when n = 0, it means that the light beam having the wavelength λ2 and the light beam having the wavelength λ3 are not diffracted by the diffraction element. Therefore, even if the diffractive element is moved in the direction of the incident optical axis, there is no change in the optical axis direction of the light flux with wavelength λ2 and the light flux with wavelength λ3, and the optical axis angle adjustment of only the light flux with wavelength λ1 is performed independently. Can do. As a result, the intervals between the light emitting elements of the light beam having the wavelength λ2 and the light beam having the wavelength λ3 arranged with high accuracy are reproduced as they are with high accuracy in the light receiving unit, and the light beam with the wavelength λ1 from the first light emitting unit having a large positional variation is accurately wavelength λ1. Can be guided to the first light receiving portion for the luminous flux.
　請求項６に記載の光ピックアップ装置は、請求項１～５のいずれかに記載の発明において、前記回折素子が、前記光源から前記対物光学系までの光路中に配置されていることを特徴とする。 An optical pickup device according to a sixth aspect is characterized in that, in the invention according to any one of the first to fifth aspects, the diffraction element is disposed in an optical path from the light source to the objective optical system. To do.
　請求項７に記載の光ピックアップ装置は、請求項１～５のいずれかに記載の発明において、前記光ディスクからの反射光と前記光源から出射した光束とを分離するための光束分離素子を有し、前記回折素子が、前記光束分離素子と前記光検出器との間に配置されていることを特徴とする。 According to a seventh aspect of the present invention, there is provided the optical pickup device according to any one of the first to fifth aspects, further comprising a light beam separating element for separating the reflected light from the optical disk and the light beam emitted from the light source. The diffraction element is disposed between the light beam separation element and the photodetector.
　請求項８に記載の光ピックアップ装置は、請求項１～７のいずれかに記載の発明において、前記対物光学系は、単一の対物レンズで構成されていることを特徴とする。 According to an eighth aspect of the present invention, there is provided the optical pickup device according to any one of the first to seventh aspects, wherein the objective optical system includes a single objective lens.
　請求項９に記載の光ピックアップ装置は、請求項１～７のいずれかに記載の発明において、前記対物光学系は、前記第１光束を前記第１光ディスクに集光する第１対物レンズと、前記第２光束を前記第２光ディスクに集光し、前記第３光束を前記第３光ディスクに集光する第２対物レンズとを有することを特徴とする。例えば前記回折構造の特性により、それを通過した前記第２光束又は前記第３光束のｎ次回折光の光量が低下する場合、前記第２対物レンズを前記第１対物レンズと異ならせ、前記第２光束及び前記第３光束の専用設計とすることで、前記第２光束又は前記第３光束の更なる光量低下を抑制できる。 An optical pickup device according to a ninth aspect is the invention according to any one of the first to seventh aspects, wherein the objective optical system includes a first objective lens that focuses the first light flux on the first optical disc; And a second objective lens for condensing the second light beam on the second optical disk and condensing the third light beam on the third optical disk. For example, when the light quantity of the n-th order diffracted light of the second light flux or the third light flux that has passed through the characteristics of the diffractive structure decreases, the second objective lens is made different from the first objective lens, and the second By using a dedicated design for the light beam and the third light beam, further reduction in the light amount of the second light beam or the third light beam can be suppressed.
　請求項１０に記載の光ピックアップ装置は、請求項１～７のいずれかに記載の発明において、前記対物光学系は、前記第１光束を前記第１光ディスクに集光し、前記第２光束を前記第２光ディスクに集光する第１対物レンズと、前記第３光束を前記第３光ディスクに集光する第２対物レンズとを有することを特徴とする。例えば前記回折構造の特性により、それを通過した前記第３光束のｎ次回折光の光量が低下する場合、前記第２対物レンズを前記第１対物レンズと異ならせ、前記第３光束の専用設計とすることで、前記第２光束又は前記第３光束の更なる光量低下を抑制できる。 According to a tenth aspect of the present invention, in the optical pickup device according to any one of the first to seventh aspects, the objective optical system condenses the first light flux on the first optical disc and the second light flux. It has a 1st objective lens which condenses on the said 2nd optical disk, and a 2nd objective lens which condenses the said 3rd light beam on the said 3rd optical disk, It is characterized by the above-mentioned. For example, when the light quantity of the nth-order diffracted light of the third light beam that has passed through the characteristics of the diffractive structure decreases, the second objective lens is made different from the first objective lens, By doing so, the further light quantity fall of the said 2nd light beam or the said 3rd light beam can be suppressed.
　請求項１１に記載の光ピックアップ装置は、請求項１～１０のいずれかに記載の発明において、前記第１受光部と、前記第２受光部と、前記第３受光部は、前記光ピックアップ装置の光軸に対し交差する方向に位置を異ならせて配置されていることを特徴とする。これにより、各光束を各受光部毎に集光させることができる。 The optical pickup device according to claim 11 is the optical pickup device according to any one of claims 1 to 10, wherein the first light receiving unit, the second light receiving unit, and the third light receiving unit are the optical pickup device. It is characterized by being arranged at different positions in the direction crossing the optical axis. Thereby, each light beam can be condensed for each light receiving part.
　請求項１２に記載の光ピックアップ装置は、請求項１～１１のいずれかに記載の発明において、前記第１光束を、前記第２受光部又は前記第３受光部に受光させることにより、前記第１受光部として兼用させることを特徴とする。これにより、光検出器をよりコンパクトなものとすることができる。 An optical pickup device according to a twelfth aspect of the present invention is the optical pickup device according to any one of the first to eleventh aspects, wherein the first light flux is received by the second light receiving portion or the third light receiving portion. One light-receiving portion is also used. Thereby, a photodetector can be made more compact.
　請求項１３に記載の光ピックアップ装置は、請求項１～１１のいずれかに記載の発明において、前記第１受光部、前記第２受光部及び前記第３受光部が共通の受光部であることを特徴とする。 An optical pickup device according to a thirteenth aspect is the invention according to any one of the first to eleventh aspects, wherein the first light receiving unit, the second light receiving unit, and the third light receiving unit are a common light receiving unit. It is characterized by.
　なお、本明細書でいう回折構造とは、段差を有し、回折によって光束を収束あるいは発散させる作用を持たせる構造の総称である。例えば、単位形状が複数並ぶことによって構成されており、それぞれの単位形状に光束が入射し、透過した光の波面が、隣り合う輪帯毎に略整数波長又は整数波長分だけズレを起こし、新たな波面を形成することによって光を集光させるような構造を含むものである。回折構造は、好ましくは段差を複数有し、段差は光軸垂直方向に周期的な間隔をもって配置されていてもよいし、光軸垂直方向に非周期的な間隔をもって配置されていてもよい。 In addition, the diffractive structure referred to in this specification is a general term for structures that have a step and have a function of converging or diverging a light beam by diffraction. For example, it is configured by arranging a plurality of unit shapes, a light beam is incident on each unit shape, and the wavefront of the transmitted light is shifted by approximately an integer wavelength or an integer wavelength for each adjacent annular zone. It includes a structure that collects light by forming a simple wavefront. The diffractive structure preferably has a plurality of steps, and the steps may be arranged with a periodic interval in the direction perpendicular to the optical axis, or may be arranged with a non-periodic interval in the direction perpendicular to the optical axis.
　又、回折構造は、光軸に直交する面に沿って直線的に延在する溝を有すると好ましい。更に、回折構造は、様々な断面形状（光軸を含む面での断面形状）をとり得、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。 The diffractive structure preferably has a groove extending linearly along a plane orthogonal to the optical axis. Furthermore, the diffractive structure can take various cross-sectional shapes (cross-sectional shapes in a plane including the optical axis), and the cross-sectional shape including the optical axis is roughly classified into a blazed structure and a staircase structure.
　尚、回折構造は、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 diffractive structure is preferably 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
　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を提供することが可能になる。 According to the present invention, it is possible to provide 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.
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１に示す光検出器ＰＤの受光面を矢印II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. 1 in the arrow II 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. 回折素子ＤＥの変形例の位置と、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 modification of the diffraction element DE, and the light receiving position of each light beam in photodetector PD. 回折素子ＤＥの変形例を、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 modification of the diffraction element DE between light source unit LDP and 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. 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ＰＵ３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 PU3 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８に示す光検出器ＰＤ’の受光面を矢印IX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. 8 in the arrow IX 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 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 the light source unit LDP and the objective lens OBJ. 第１受光部、第２受光部及び第３受光部を共通の受光部３２Ｒで兼用する場合の、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。The relationship between the position of the diffraction element DE ′ and the light receiving position of each light beam in the photodetector PD ′ when the first light receiving unit, the second light receiving unit, and the third light receiving unit are shared by the common light receiving unit 32R is shown. FIG. 第１受光部、第２受光部及び第３受光部を共通の受光部３２Ｒで兼用する場合の、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。In the case where the first light receiving unit, the second light receiving unit, and the third light receiving unit are shared by the common light receiving unit 32R, the light having the diffraction element DE ′ disposed between the light source unit LDP and the objective lens OBJ as another position. It is the schematic of a pick-up apparatus.
　以下、本発明の実施の形態を、図面を参照して説明する。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. The present invention is not limited to the present embodiment.
　図１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２は、図１に示す光検出器ＰＤの受光面を矢印II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。 FIG. 1 is a diagram schematically showing a configuration of an optical pickup apparatus 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. 2 is a view of the light receiving surface of the photodetector PD shown in FIG. 1 as viewed in the direction of arrow II, 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.
　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）と、１つのパッケージに収容した光源ユニット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、回折構造を有する回折素子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Ｇａ系半導体基板の同一チップに形成され（モノリシック構成）、第１半導体レーザＬＤ１は、それとは異なる窒化物系半導体基板のチップに形成されている（ハイブリッド構成）。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 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 third semiconductor laser LD3 (third light emitting unit) that emits a light beam), a light source unit LDP housed in one package, and a group that divides an incident light beam into three parts. Computing GRT, sensor lens SN, the diffraction element DE having a diffractive structure comprises a photodetector PD, and the like. The second semiconductor laser LD2 and the third semiconductor laser LD3 are formed on the same chip of the Ga-based semiconductor substrate (monolithic configuration), and the first semiconductor laser LD1 is formed on a chip of a different nitride-based semiconductor substrate. Yes (hybrid configuration). An example of such a light source is disclosed in Japanese Patent Application Laid-Open No. 2004-319915.
　このように、第１半導体レーザＬＤ１が形成されたチップと第２半導体レーザＬＤ２及び第３半導体レーザＬＤ３が形成されたチップとが別体の場合には、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との光軸直交方向の間隔が安定せず、その間隔にバラツキが生じ易い。 Thus, when the chip on which the first semiconductor laser LD1 is formed and the chip on which the second semiconductor laser LD2 and the third semiconductor laser LD3 are formed are separate, the first semiconductor laser LD1 and the second semiconductor laser The distance between the LD2 and the third semiconductor laser LD3 in the direction perpendicular to the optical axis is not stable, and the distance tends to vary.
　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１次回折光を発生し、第２光束及び第３光束が入射したときに最も光量が高い回折光として０次回折光を発生する回折構造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 generates the first-order diffracted light as the diffracted light having the highest light amount when the first light beam is incident, and the 0th-order diffracted light as the diffracted light having the highest light amount when the second and third light beams are incident. The generated diffraction structure 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２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、その受光量をそれぞれ３ｈ、３ｇ、及び３ｂ、３ａとする。 As shown in FIG. 2, 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 in the vertical and horizontal directions, and the received light amounts are 1e, 1c, 1f, and 1d, respectively. The light receiving portions 11R and 13R on both sides of the light receiving portion 12R are divided into left and right parts, and the received light amounts are 1h, 1g, and 1b, 1a, respectively. The light receiving unit 22R is divided into four parts, top, bottom, left, and right, and the amounts of light received 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 the received light amounts are 2h, 2g, 2b and 2a, respectively. Further, the light receiving unit 32R is divided into four parts in the vertical and horizontal directions, and the received light amounts are 3e, 3c, 3f, and 3d, respectively. The light receiving portions 31R and 33R on both sides of the light receiving portion 32R are divided into left and right parts, and the received light amounts are 3h, 3g, 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、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 light beam passing through the COL, converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, the diameter of the light beam being regulated by a diaphragm (not shown), and further condensed by the objective lens OBJ has a thickness of 0.1 mm. It becomes a spot formed on the information recording surface of the BD through the protective substrate.
　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。なお、センサレンズＳＮは、凹レンズを光軸に対し傾斜させたものである。 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). The sensor lens SN is a concave lens that is inclined with respect to the optical axis.
　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、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. The light beam that has passed through the collimator lens COL, converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, is regulated by a diaphragm (not shown), and is condensed by the objective lens OBJ. It 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、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 that has passed through the collimator lens COL, converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, is regulated by a diaphragm (not shown), and further condensed by the objective lens OBJ has a thickness of It becomes a spot formed on the information recording surface of the CD through the 1.2 mm protective substrate.
　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３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いる。例えば、図３（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が基準値より大きく、回折素子ＤＥを通過した第２光束と第３光束の０次回折光が、それぞれ受光部２２Ｒ、３２Ｒの中央に位置するように光学系をセットすると、第１光束の１次回折光が受光部１２Ｒの上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. 3 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, but each light beam is shown by a line for easy understanding. For example, in the state shown in FIG. 3A, the distance between the first semiconductor laser and the second semiconductor laser is larger than the reference value, and the second-order light beam and the zero-order diffracted light of the third light beam that have passed through the diffraction element DE are respectively If the optical system is set so as to be positioned at the center of the light receiving parts 22R and 32R, the first-order diffracted light of the first light beam may be condensed above the light receiving part 12R, and an inappropriate signal may be output.
　かかる場合、図３（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２光束と第３光束の０次回折光の光路は変わらないのに対し、第１光束の１次回折光は、受光部１２Ｒ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１光束の１次回折光が受光部１２Ｒの下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. 3B, 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 second light beam and the third light beam that has passed through the diffraction element DE is In contrast, the first-order diffracted light of the first light flux approaches the center of the light receiving unit 12R. 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 first light beam is condensed below the light receiving unit 12R, the diffractive element DE may be moved away from the photodetector PD.
　より具体的に、光ピックアップ装置の調整方法について述べる。尚、以下の調整は、光ピックアップ装置を仮組みした状態で行うものとする。 More specifically, a method for adjusting the optical pickup device will be described. The following adjustment is performed in a state where the optical pickup device is temporarily assembled.
　（１）第２半導体レーザＬＤ２から射出された第２光束によるサーボ調整
ａ）　通常の非点収差法を用いたＤＶＤ用光ピックアップ装置の調整と同様にして、調整用光ディスク（ＤＶＤ）に対する遠近の往復運動を対物レンズＯＢＪに与えながら、光ディスクの情報記録面において第２光束が結像したとき、メインビームが受光部２２Ｒの４分割の中心で円径スポットとなるよう（すなわち２ｃ、２ｄ、２ｅ、２ｆの各出力信号が等しく、またこれらの和信号が最大となるよう）、光検出器ＰＤを光軸垂直面内で、センサレンズＳＮを光軸方向に変位させて位置調整を行う。
ｂ）　回転する光ディスクに対してフォーカスサーボを適用したあと、第２光束用のグレーティングＧＲＴを、ＴＥ信号が最大となるよう光軸を中心に回転調整を行う。ただしグレーティングＧＲＴは第１光束、第２光束、第３光束それぞれ個別調整できるものとする（不図示）。
ｃ）　トラッキングサーボを適用した状態でＲＦ信号が最大となるよう、光検出器ＰＤとセンサレンズＳＮの位置を微調整する（調整方向は上記ａ）と同じ）。 (1) Servo adjustment by the second light beam emitted from the second semiconductor laser LD2 a) In the same manner as the adjustment of the optical pickup device for DVD using the normal astigmatism method, the distance to the adjustment optical disk (DVD) is adjusted. When the second light beam forms an image on the information recording surface of the optical disc while applying the reciprocating motion to the objective lens OBJ, the main beam becomes a circular spot at the center of the four divisions of the light receiving portion 22R (that is, 2c, 2d, 2e). The output signals of 2f are equal and the sum of these signals is maximized), and the position is adjusted by displacing the sensor PD in the optical axis direction and the sensor lens SN in the optical axis direction.
b) After applying the focus servo to the rotating optical disk, the second light beam grating GRT is rotated around the optical axis so that the TE signal is maximized. However, the grating GRT can be individually adjusted for the first light flux, the second light flux, and the third light flux (not shown).
c) Finely adjust the positions of the photodetector PD and the sensor lens SN so that the RF signal becomes maximum in a state where the tracking servo is applied (the adjustment direction is the same as that in the above a)).
　（２）第１半導体レーザＬＤ１から射出された第１光束によるサーボ調整（第２光束の代わりに第１光束を用いる。）
ａ）　調整用光ディスク（ＢＤ）に対する遠近の往復運動を対物レンズＯＢＪに与えながら、光ディスクの情報記録面において第１光束が結像したとき、メインビームが受光部１２Ｒの４分割の中心で円径スポットとなるよう（すなわち１ｃ、１ｄ、１ｅ、１ｆの各出力信号が等しく、またこれらの和信号が最大となるよう）、回折素子ＤＥを光軸方向に変位させて位置調整を行う。
ｂ）　回転する光ディスクに対してフォーカスサーボを適用した後、第１光束用のグレーティングＧＲＴを、ＴＥ信号が最大となるよう光軸を中心に回転調整を行う。
ｃ）　トラッキングサーボを適用した状態でＲＦ信号が最大になるよう、回折素子ＤＥを光軸方向に微調整する。 (2) Servo adjustment using the first light beam emitted from the first semiconductor laser LD1 (using the first light beam instead of the second light beam)
a) When the first light beam forms an image on the information recording surface of the optical disk while giving the objective lens OBJ a reciprocating motion to and from the adjustment optical disk (BD), the main beam has a circular diameter at the center of the four divisions of the light receiving unit 12R. The position is adjusted by displacing the diffractive element DE in the optical axis direction so as to be a spot (that is, the output signals 1c, 1d, 1e, and 1f are equal and the sum signal thereof is maximized).
b) After applying the focus servo to the rotating optical disc, the rotation of the grating GRT for the first light beam is adjusted around the optical axis so that the TE signal is maximized.
c) Finely adjust the diffraction element DE in the optical axis direction so that the RF signal is maximized in a state where the tracking servo is applied.
　（３）第３半導体レーザＬＤ３から射出された第３光束によるサーボ調整（第１光束の代わりに第３光束を用いる。）
ａ）　回転する調整用光ディスク（ＣＤ）にフォーカスサーボを適用した後、第３光束用のグレーティングＧＲＴを、ＴＥ信号が最大となるよう光軸を中心に回転調整を行う。 (3) Servo adjustment using a third light beam emitted from the third semiconductor laser LD3 (a third light beam is used instead of the first light beam)
a) After applying the focus servo to the rotating optical disk for adjustment (CD), the third light beam grating GRT is rotationally adjusted around the optical axis so that the TE signal is maximized.
　調整方法は以上であるが、光源を切り換える際、対物レンズＯＢＪの設計によってはコリメートレンズＣＯＬを所定の位置になるよう光軸方向に移動させる必要がある場合があるが、この技術は公知であるため、ここでは説明を省略した。 Although the adjustment method is as described above, when switching the light source, it may be necessary to move the collimating lens COL in the direction of the optical axis so as to reach a predetermined position depending on the design of the objective lens OBJ, but this technique is publicly known. Therefore, the description is omitted here.
　図４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。本例においては、偏光ビームスプリッタＰＢＳとしてキューブ型の偏光ビームスプリッタを用いている。また、図１に示す光ピックアップ装置の、グレーティングＧＲＴ及び光源ユニットＬＤＰと、センサレンズＳＮ、回折素子ＤＥ及び光検出器ＰＤと、の配置を入れ替えてある。また、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。 FIG. 4 is a schematic view of an optical pickup device in which the diffraction element DE is arranged between the light source unit LDP and the objective lens OBJ as another position. In this example, a cube-type polarizing beam splitter is used as the polarizing beam splitter PBS. In addition, the arrangement of the grating GRT and the light source unit LDP, the sensor lens SN, the diffraction element DE, and the photodetector PD in the optical pickup device shown in FIG. 1 is switched. Further, some elements are omitted, and each light flux is shown by a line for easy understanding.
　図４（ａ）に示す状態では、第１半導体レーザＬＤ１と第２半導体レーザＬＤ２との間隔が基準値より大きいため、回折素子ＤＥを通過した第２光束と第３光束の０次回折光が、それぞれ偏光ビームスプリッタＰＢＳを通過し、対物レンズＯＢＪにより光ディスク（ＢＤ／ＤＶＤ／ＣＤ）に集光され、その反射光が対物レンズＯＢＪを通過し、偏光ビームスプリッタＰＢＳで反射され、光検出器ＰＤの受光部２２Ｒ、３２Ｒの中央に位置するように光学系をセットすると、第１光束の１次回折光が受光部１２Ｒの上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。 In the state shown in FIG. 4A, since the distance between the first semiconductor laser LD1 and the second semiconductor laser LD2 is larger than the reference value, the 0th-order diffracted light of the second light flux and the third light flux that have passed through the diffraction element DE is Each passes through the polarization beam splitter PBS, is focused on the optical disk (BD / DVD / CD) by the objective lens OBJ, and the reflected light passes through the objective lens OBJ, is reflected by the polarization beam splitter PBS, and is reflected on the photodetector PD. If the optical system is set so as to be positioned at the center of the light receiving parts 22R and 32R, the first-order diffracted light of the first light beam may be condensed above the light receiving part 12R, and an inappropriate signal may be output.
　かかる場合、図４（ｂ）に示すように、回折素子ＤＥを対物レンズＯＢＪから離間させるように移動させると、回折素子ＤＥを通過した第２光束と第３光束の０次回折光の光路は変わらないのに対し、第１光束の１次回折光は、受光部１２Ｒの中央に近づくようになる。即ち、回折素子ＤＥを対物レンズＯＢＪ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１光束の１次回折光が受光部１２Ｒの下方に集光してしまう場合には、回折素子ＤＥを対物レンズＯＢＪに接近させるように移動させればよい。 In this case, as shown in FIG. 4B, when the diffraction element DE is moved away from the objective lens OBJ, the optical paths of the 0th-order diffracted light of the second light beam and the third light beam that have passed through the diffraction element DE are changed. In contrast, the first-order diffracted light of the first light flux approaches the center of the light receiving unit 12R. That is, by moving the diffractive element DE relative to the objective lens OBJ, all the light beams can be appropriately condensed on the light receiving part. When the first-order diffracted light of the first light beam is condensed below the light receiving unit 12R, the diffractive element DE may be moved so as to approach the objective lens OBJ.
　次に、回折素子ＤＥの変形例として、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１次回折光を発生し、第２光束及び第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構造を表面に形成している場合について説明する。 Next, as a modification of the diffractive element DE, the first-order diffracted light is generated as the diffracted light having the highest light amount when the first light beam is incident, and the diffraction having the highest light amount is performed when the second light beam and the third light beam are incident. A case where a diffractive structure that generates −1st order diffracted light as light is formed on the surface will be described.
　図５は、図３と同様に光検出器ＰＤと偏光ビームスプリッタＰＢＳとの間に配置された回折素子ＤＥの変形例の位置と、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いる。本変形例では、図５（ｃ）に示すように、第２光束と第３光束の－１次回折光は回折素子ＤＥを通過して光軸から下方に遠ざかるように折れ曲がる（Ｓ２，Ｓ３）が、第１光束の１次回折光は、回折素子ＤＥを通過して光軸から上方に遠ざかるように折れ曲がっている（Ｓ１）。第１光束と第２光束の集光スポット間隔をＬ１２とし、第２光束と第３光束の集光スポット間隔をＬ２３とする。 FIG. 5 shows the relationship between the position of the modified example of the diffraction element DE disposed between the photodetector PD and the polarization beam splitter PBS and the light receiving position of each light beam in the photodetector PD, as in FIG. Although it is a schematic view, each light beam is shown by a line for easy understanding. In the present modification, as shown in FIG. 5C, the −1st order diffracted light of the second light beam and the third light beam is bent so as to pass through the diffraction element DE and away from the optical axis (S2, S3). The first-order diffracted light of the first light beam is bent so as to pass through the diffraction element DE and away from the optical axis (S1). Let L12 be the focal spot interval between the first and second luminous fluxes, and let L23 be the focal spot interval between the second and third luminous fluxes.
　ここで、第１発光部と第２発光部との間隔が基準値より大きいとした場合、図５（ａ）に示すように、回折素子ＤＥを通過した第２光束と第３光束の－１次回折光が、それぞれ受光部２２Ｒ、３２Ｒの中央に位置するように光学系をセットすると、第１光束の１次回折光が受光部１２Ｒの上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。 Here, when the interval between the first light emitting unit and the second light emitting unit is larger than the reference value, as shown in FIG. 5A, −1 of the second light flux and the third light flux that have passed through the diffraction element DE. If the optical system is set so that the next-order diffracted light is positioned at the center of each of the light receiving portions 22R and 32R, the first-order diffracted light of the first light beam is condensed above the light receiving portion 12R, and an inappropriate signal is output. There is a risk.
　かかる場合、図５（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２光束と第３光束の－１次回折光は略平行の状態が維持されるため（Ｓ２’、Ｓ３’）、回折素子ＤＥ移動後における第２光束と第３光束の集光スポット間隔は略一定である（Ｌ２３＝Ｌ２３’）が、第２光束及び第３光束のスポット位置は、光検出器に対して上方へと移動する。一方、第１光束の１次回折光は、受光部１２Ｒの中央に近づくようになる（Ｓ１’）と共に、回折素子ＤＥ移動後における第１光束と第２光束の集光スポット間隔はより小さくなる（Ｌ１２＞Ｌ１２’）。そこで、回折素子ＤＥを光検出器ＰＤに対して相対的に移動すると共に、光検出器ＰＤを光軸直交方向（この場合には上方）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１光束の１次回折光が受光部１２Ｒの下方に集光してしまう場合には、回折素子ＤＥを光検出器ＰＤから離間させると共に、光検出器ＰＤを光軸直交方向（この場合には下方）に移動させればよい。 In this case, as shown in FIG. 5B, when the diffractive element DE is moved closer to the photodetector PD, the -1st order diffracted light of the second light beam and the third light beam that have passed through the diffractive element DE is approximately Since the parallel state is maintained (S2 ′, S3 ′), the distance between the second light flux and the third light flux after the movement of the diffraction element DE is substantially constant (L23 = L23 ′), but the second light flux The spot position of the third light beam moves upward with respect to the photodetector. On the other hand, the first-order diffracted light of the first light flux approaches the center of the light receiving unit 12R (S1 ′), and the condensing spot interval between the first light flux and the second light flux after the movement of the diffraction element DE becomes smaller (S1 ′). L12> L12 ′). Therefore, the diffractive element DE is moved relative to the photodetector PD, and the photodetector PD is moved in the direction perpendicular to the optical axis (in this case, upward), so that all the light beams are respectively transmitted to the light receiving unit. The light can be collected appropriately. When the first-order diffracted light of the first light beam is condensed below the light receiving portion 12R, the diffractive element DE is separated from the light detector PD and the light detector PD is moved in the direction perpendicular to the optical axis (in this case). To the lower).
　図６は、回折素子ＤＥの変形例を、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。本例においては、偏光ビームスプリッタＰＢＳとしてキューブ型の偏光ビームスプリッタを用いている。また、図１に示す光ピックアップ装置の、グレーティングＧＲＴ及び光源ユニットＬＤＰと、センサレンズＳＮ、回折素子ＤＥ及び光検出器ＰＤと、の配置を入れ替えてある。また、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。 FIG. 6 is a schematic diagram of an optical pickup device in which a modification of the diffraction element DE is arranged between the light source unit LDP and the objective lens OBJ. In this example, a cube-type polarizing beam splitter is used as the polarizing beam splitter PBS. In addition, the arrangement of the grating GRT and the light source unit LDP, the sensor lens SN, the diffraction element DE, and the photodetector PD in the optical pickup device shown in FIG. 1 is switched. Further, some elements are omitted, and each light flux is shown by a line for easy understanding.
　図６（ａ）に示す状態では、第１半導体レーザＬＤ１と第２半導体レーザＬＤ２との間隔が基準値より大きいため、回折素子ＤＥを通過した第２光束と第３光束の－１次回折光が、それぞれ偏光ビームスプリッタＰＢＳを通過し、対物レンズＯＢＪにより光ディスク（ＢＤ／ＤＶＤ／ＣＤ）に集光され、その反射光が対物レンズＯＢＪを通過し、偏光ビームスプリッタＰＢＳで反射され、光検出器ＰＤの受光部２２Ｒ、３２Ｒの中央に位置するように光学系をセットすると、第１光束の１次回折光が受光部１２Ｒの上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。 In the state shown in FIG. 6A, since the distance between the first semiconductor laser LD1 and the second semiconductor laser LD2 is larger than the reference value, the −1st order diffracted light of the second light flux and the third light flux that have passed through the diffraction element DE is , Each passing through the polarizing beam splitter PBS, condensed on the optical disc (BD / DVD / CD) by the objective lens OBJ, and the reflected light passes through the objective lens OBJ and reflected by the polarizing beam splitter PBS, and is detected by the photodetector PD. If the optical system is set so as to be positioned at the center of the light receiving portions 22R and 32R, the first-order diffracted light of the first light beam is condensed above the light receiving portion 12R, and an inappropriate signal may be output. .
　かかる場合、図６（ｂ）に示すように、回折素子ＤＥを対物レンズＯＢＪから離間させるように移動させると共に、光検出器ＰＤを光軸直交方向（この場合には上方）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１光束の１次回折光が受光部１２Ｒの下方に集光してしまう場合には、回折素子ＤＥを対物レンズＯＢＪから離間させると共に、光検出器ＰＤを光軸直交方向（この場合には下方）に移動させればよい。 In such a case, as shown in FIG. 6B, the diffraction element DE is moved away from the objective lens OBJ, and the photodetector PD is moved in the direction perpendicular to the optical axis (in this case, upward). All the light beams can be appropriately condensed on the light receiving part. When the first-order diffracted light of the first light beam is condensed below the light receiving unit 12R, the diffractive element DE is separated from the objective lens OBJ and the photodetector PD is moved in the direction orthogonal to the optical axis (in this case). May be moved downward).
　図７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、上述した実施の形態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. 7 is a diagram schematically showing a configuration of the optical pickup device PU2 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 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 differences from the above-described embodiment will be described, and the description of the common components will be omitted by attaching the same reference numerals.
　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、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 light beam that has passed through the COL, converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, is regulated by a diaphragm (not shown), and is condensed by the first objective lens OBJ1, has a thickness of 0. A spot formed on the information recording surface of the BD through a 1 mm protective substrate.
　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 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 objective lens OBJ 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、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 parts, as shown by a one-dot chain line, and then reflected by the polarization beam splitter PBS and collimated. The light beam passing through the lens COL, converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, the diameter of the light beam being regulated by a diaphragm (not shown), and further condensed by the second objective lens OBJ2 has a thickness of It becomes a spot formed on the information recording surface of the DVD through a 0.6 mm protective substrate.
　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 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, 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.
　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、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 light beam that has passed through the COL, converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, whose light beam diameter is regulated by a diaphragm (not shown), and condensed by the second objective lens OBJ2 has a thickness of 1 A spot formed on the information recording surface of the CD through a 2 mm protective substrate.
　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 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. 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.
　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.
　図８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ＰＵ３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ＰＵ３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。 FIG. 8 is a diagram schematically showing a configuration of the optical pickup device PU3 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 PU3 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.
　本実施の形態においては、図１の実施の形態に対して回折格子ＤＥ’と光検出器ＰＤ’とが異なる。それ以外の構成については、上述した実施の形態と共通するので、同じ符号を付すことで説明を省略する。具体的に異なる点を説明すると、本実施の形態における回折格子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－１次回折光（第３光束に近づく方向に曲がる）を発生し、第２光束及び第３光束が入射したときに最も光量が高い回折光として０次回折光を発生する回折構造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。 In the present embodiment, the diffraction grating DE 'and the photodetector PD' are different from the embodiment of FIG. Other configurations are the same as those in the above-described embodiment, and thus the same reference numerals are used and description thereof is omitted. Specifically, the difference is that the diffraction grating DE ′ in the present embodiment generates −1st order diffracted light (bent in a direction approaching the third light beam) as diffracted light having the highest light amount when the first light beam is incident. A diffractive structure that generates zero-order diffracted light as the diffracted light having the highest light amount when the second light flux and the third light flux are incident 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.
　更に光検出器ＰＤ’は、図９に示すように光軸に略直交する受光面側に、２行３列に並んだ受光部２１Ｒ～３３Ｒを有するため、図２の構成に比べコンパクトとなっている。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ＢＤからの反射光とＣＤからの反射光を共通して受光する第３受光部（兼第１受光部）である。受光部２２Ｒは、上下左右に４分割され、その受光量をそれぞれ２ｅ、２ｃ、２ｆ、２ｄとする。又受光部２２Ｒの両側の受光部２１Ｒ、２３Ｒは分割されておらず、その受光量をそれぞれ２ｂ及び２ａとする。更に受光部３２Ｒは、上下左右に４分割され、その受光量をそれぞれ１３ｅ、１３ｃ、１３ｆ、１３ｄとする。又受光部３２Ｒの両側の受光部３１Ｒ、３３Ｒは分割されておらず、その受光量をそれぞれ１３ｂ及び１３ａとする。尚、受光部３１Ｒ、３３Ｒに集光される光束において、受光部３２Ｒに近い集光スポットはＢＤからの反射光を、受光部３２Ｒから離れた集光スポットはＣＤからの反射光を、それぞれ意味する。 Further, as shown in FIG. 9, the photodetector PD ′ has light receiving portions 21R to 33R arranged in 2 rows and 3 columns on the light receiving surface side substantially orthogonal to the optical axis, so that it is more compact than the configuration of FIG. ing. The light receiving units 21R to 23R are second light receiving units that receive the reflected light from the DVD, and the light receiving units 31R to 33R are the third light receiving units (also serving as both the reflected light from the BD and the reflected light from the CD). 1st light-receiving part). The light receiving unit 22R is divided into four parts, top, bottom, left, and right, and the amounts of light received are 2e, 2c, 2f, and 2d, respectively. The light receiving portions 21R and 23R on both sides of the light receiving portion 22R are not divided, and the amounts of received light are 2b and 2a, respectively. Further, the light receiving unit 32R is divided into four parts, top, bottom, left, and right, and the amounts of received light are 13e, 13c, 13f, and 13d, respectively. The light receiving portions 31R and 33R on both sides of the light receiving portion 32R are not divided, and the amounts of received light are 13b and 13a, respectively. In the light beams condensed on the light receiving parts 31R and 33R, the light spot near the light receiving part 32R means reflected light from the BD, and the light spot far from the light receiving part 32R means reflected light from the CD. To do.
　次に光ピックアップ装置ＰＵ３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、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 PU3 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 light beam passing through the COL, converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, the diameter of the light beam being regulated by a diaphragm (not shown), and further condensed by the objective lens OBJ has a thickness of 0.1 mm. It becomes a spot formed on the information recording surface of the BD through the protective substrate.
　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、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. 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, 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（１３ｃ＋１３ｆ）－（１３ｅ＋１３ｄ）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 (13c + 13f) − (13e + 13d), 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３ビーム法を用いることとする。３ビーム法において、ＴＥ信号は、（１３ａ－１３ｂ）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、（１３ａ＋１３ｂ＋１３ｃ＋１３ｄ＋１３ｅ＋１３ｆ）で表される。 On the other hand, the tracking servo uses the 3-beam method. In the three-beam method, the TE signal is obtained by (13a-13b), 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 (13a + 13b + 13c + 13d + 13e + 13f).
　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、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. The light beam that has passed through the collimator lens COL, converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, is regulated by a diaphragm (not shown), and is condensed by the objective lens OBJ. It 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３ビーム法を用いることとする。３ビーム法において、ＴＥ信号は、（２ａ－２ｂ）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）で表される。 On the other hand, the tracking servo uses the 3-beam method. In the three-beam method, the TE signal is obtained by (2a-2b), 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).
　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、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 that has passed through the collimator lens COL, converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, is regulated by a diaphragm (not shown), and further condensed by the objective lens OBJ has a thickness of It becomes a spot formed on the information recording surface of the CD through the 1.2 mm protective substrate.
　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（１３ｃ＋１３ｆ）－（１３ｅ＋１３ｄ）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 (13c + 13f) − (13e + 13d), 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３ビーム法を用いることとする。３ビーム法において、ＴＥ信号は、（１３ａ－１３ｂ）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、（１３ａ＋１３ｂ＋１３ｃ＋１３ｄ＋１３ｅ＋１３ｆ）で表される。 On the other hand, the tracking servo uses the 3-beam method. In the three-beam method, the TE signal is obtained by (13a-13b), 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 (13a + 13b + 13c + 13d + 13e + 13f).
　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２１Ｒ～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２１Ｒ～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 21R to 33R of the photodetector PD 'cannot be shifted. Therefore, if the interval between the semiconductor lasers exceeds the allowable error, each light beam cannot be properly received by the light receiving portions 21R to 33R. Therefore, in the present embodiment, such a problem is solved as follows.
　図１０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いる。 FIG. 10 is a schematic diagram showing the relationship between the position of the diffractive element DE 'and the light receiving position of each light beam in the photodetector PD', but each light beam is shown by a line for easy understanding.
　図１０（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が基準値より大きく、回折素子ＤＥ’を通過した第２光束と第３光束の０次回折光Ｂ２，Ｂ３が、それぞれ受光部２２Ｒ、３２Ｒの中央に位置するように光学系をセットすると、第１光束の－１次回折光Ｂ１が受光部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。 In the state shown in FIG. 10A, the distance between the first semiconductor laser and the second semiconductor laser is larger than the reference value, and the 0th-order diffracted lights B2 and B3 of the second light flux and the third light flux that have passed through the diffractive element DE ′ are obtained. If the optical system is set so as to be positioned at the center of each of the light receiving portions 22R and 32R, the −1st order diffracted light B1 of the first light beam is condensed below the light receiving portion 32R, and an inappropriate signal is output. There is a fear.
　かかる場合、図１０（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２光束と第３光束の０次回折光Ｂ２，Ｂ３の光路は変わらないのに対し、第１光束の－１次回折光Ｂ１は、受光部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１光束の－１次回折光Ｂ１が受光部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. 10B, when the diffraction element DE ′ is moved so as to approach the photodetector PD ′, the 0th-order diffracted light of the second light beam and the third light beam that have passed through the diffraction element DE ′. While the optical paths of B2 and B3 are not changed, the −1st order diffracted light B1 of the first light flux comes closer to the center of the light receiving part 32R. 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 parts. When the −1st order diffracted light B1 of the first light beam is condensed above the light receiving portion 32R, the diffractive element DE ′ may be moved away from the photodetector PD ′.
　図１１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。本例においては、偏光ビームスプリッタＰＢＳとしてキューブ型の偏光ビームスプリッタを用いている。また、図８に示す光ピックアップ装置の、グレーティングＧＲＴ及び光源ユニットＬＤＰと、センサレンズＳＮ、回折素子ＤＥ及び光検出器ＰＤと、の配置を入れ替えてある。また、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。 FIG. 11 is a schematic diagram 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. In this example, a cube-type polarizing beam splitter is used as the polarizing beam splitter PBS. Further, the arrangement of the grating GRT and the light source unit LDP, the sensor lens SN, the diffraction element DE, and the photodetector PD in the optical pickup device shown in FIG. 8 is switched. Further, some elements are omitted, and each light flux is shown by a line for easy understanding.
　図１１（ａ）に示す状態では、第１半導体レーザＬＤ１と第２半導体レーザＬＤ２との間隔が基準値より大きいため、回折素子ＤＥ’を通過した第２光束と第３光束の０次回折光Ｂ２，Ｂ３が、それぞれ偏光ビームスプリッタＰＢＳを通過し、対物レンズＯＢＪにより光ディスク（ＢＤ／ＤＶＤ／ＣＤ）に集光され、その反射光が対物レンズＯＢＪを通過し、偏光ビームスプリッタＰＢＳで反射され、光検出器ＰＤの受光部２２Ｒ、３２Ｒの中央に位置するように光学系をセットすると、第１光束の－１次回折光Ｂ１が受光部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。 In the state shown in FIG. 11A, since the distance between the first semiconductor laser LD1 and the second semiconductor laser LD2 is larger than the reference value, the 0th-order diffracted light B2 of the second light flux and the third light flux that have passed through the diffraction element DE ′. , B3 pass through the polarization beam splitter PBS, and are collected on the optical disk (BD / DVD / CD) by the objective lens OBJ, and the reflected light passes through the objective lens OBJ, and is reflected by the polarization beam splitter PBS, and the light. If the optical system is set so that it is positioned at the center of the light receiving portions 22R and 32R of the detector PD, the −1st order diffracted light B1 of the first light beam is condensed below the light receiving portion 32R, and an inappropriate signal is output. There is a fear.
　かかる場合、図１１（ｂ）に示すように、回折素子ＤＥ’を対物レンズＯＢＪから離間させるように移動させると、回折素子ＤＥ’を通過した第２光束と第３光束の０次回折光Ｂ２，Ｂ３の光路は変わらないのに対し、第１光束の－１次回折光Ｂ１は、受光部３２Ｒの中央に近づくようになる。即ち、回折素子ＤＥ’を対物レンズＯＢＪ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１光束の－１次回折光Ｂ１が受光部３２Ｒの上方に集光してしまう場合には、回折素子ＤＥ’を対物レンズＯＢＪに接近させるように移動させればよい。 In this case, as shown in FIG. 11B, when the diffractive element DE ′ is moved away from the objective lens OBJ, the 0th-order diffracted light B2 of the second light flux and the third light flux that have passed through the diffractive element DE ′ is obtained. While the optical path of B3 does not change, the −1st order diffracted light B1 of the first light flux comes closer to the center of the light receiving part 32R. That is, by moving the diffractive element DE ′ relative to the objective lens OBJ, all the light beams can be appropriately condensed on the light receiving part. If the −1st order diffracted light B1 of the first light beam is condensed above the light receiving portion 32R, the diffractive element DE ′ may be moved so as to approach the objective lens OBJ.
　以上の実施の形態では、第３受光部で第１光束及び第３光束を共通に受光するようにしたが、第２受光部で第１光束及び第２光束を共通に受光するようにしてもよい。又、共通に用いない受光部においては、上述の実施の形態のようにＤＰＰ法でトラッキングサーボを行っても良い。更に、回折素子ＤＥ’に第２光束と第３光束を入射させたとき、０次以外（但しｎ≠ｍ）の回折光を発生させても良い。 In the above embodiment, the first light beam and the third light beam are commonly received by the third light receiving unit. However, the first light beam and the second light beam may be commonly received by the second light receiving unit. Good. In a light receiving unit that is not used in common, tracking servo may be performed by the DPP method as in the above-described embodiment. Further, when the second light beam and the third light beam are made incident on the diffractive element DE ', diffracted light other than the 0th order (where n ≠ m) may be generated.
　さらに、第１受光部、第２受光部及び第３受光部を共通の受光部とすることもできる。 Furthermore, the first light receiving unit, the second light receiving unit, and the third light receiving unit may be a common light receiving unit.
　図１２は、第１受光部、第２受光部及び第３受光部を共通の受光部３２Ｒで兼用する場合の、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。図１２においては、図１０に示す配置に加え、回折素子ＤＥ’の光源側に、λ２の第２光束のみを回折させる光学素子ＤＥ”を配置してある。 FIG. 12 shows the position of the diffraction element DE ′ and the light receiving position of each light beam in the photodetector PD ′ when the first light receiving unit, the second light receiving unit, and the third light receiving unit are shared by the common light receiving unit 32R. It is the schematic which shows these relationships. In FIG. 12, in addition to the arrangement shown in FIG. 10, an optical element DE ″ that diffracts only the second light flux of λ2 is arranged on the light source side of the diffraction element DE ′.
　図１２（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が基準値より大きいため、光学素子ＤＥ”及び回折素子ＤＥ’を通過した第２光束と第３光束の０次回折光Ｂ２，Ｂ３が、それぞれ受光部３２Ｒの中央に位置するように光学系をセットすると、第１光束の－１次回折光Ｂ１が受光部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。 In the state shown in FIG. 12A, since the distance between the first semiconductor laser and the second semiconductor laser is larger than the reference value, 0 of the second light flux and the third light flux that have passed through the optical element DE ″ and the diffraction element DE ′. If the optical system is set so that the second-order diffracted beams B2 and B3 are respectively positioned at the center of the light receiving unit 32R, the −1st-order diffracted light B1 of the first light beam is condensed below the light receiving unit 32R, and an inappropriate signal is obtained. May be output.
　かかる場合、図１２（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２光束と第３光束の０次回折光Ｂ２，Ｂ３の光路は変わらないのに対し、第１光束の－１次回折光Ｂ１は、受光部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、全ての光束を受光部３２Ｒに適切に集光することができるのである。尚、第１光束の－１次回折光Ｂ１が受光部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. 12B, when the diffractive element DE ′ is moved closer to the photodetector PD ′, the 0th-order diffracted light of the second light flux and the third light flux that have passed through the diffractive element DE ′. While the optical paths of B2 and B3 are not changed, the −1st order diffracted light B1 of the first light flux comes closer to the center of the light receiving part 32R. That is, by moving the diffractive element DE ′ relative to the photodetector PD ′, it is possible to appropriately collect all the light beams on the light receiving unit 32R. When the −1st order diffracted light B1 of the first light beam is condensed above the light receiving portion 32R, the diffractive element DE ′ may be moved away from the photodetector PD ′.
　図１３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。図１３においては、図１１に示す配置に加え、光検出器ＰＤ’と偏光ビームスプリッタＰＢＳの間に、λ２の第２光束のみを回折させる光学素子ＤＥ”を配置してある。本例においては、偏光ビームスプリッタＰＢＳをキューブ型の偏光ビームスプリッタを用いている。また、図８に示す光ピックアップ装置とは、グレーティングＧＲＴ及び光源ユニットＬＤＰと、センサレンズＳＮ、回折素子ＤＥ及び光検出器ＰＤと、の配置を入れ替えたものである。また、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。 FIG. 13 is a schematic view of an optical pickup device in which the diffraction element DE ′ is disposed between the light source unit LDP and the objective lens OBJ as another position. 13, in addition to the arrangement shown in FIG. 11, an optical element DE ″ that diffracts only the second light flux of λ2 is arranged between the photodetector PD ′ and the polarization beam splitter PBS. The polarizing beam splitter PBS is a cube-shaped polarizing beam splitter, and the optical pickup device shown in Fig. 8 includes a grating GRT and a light source unit LDP, a sensor lens SN, a diffraction element DE, and a photodetector PD. Also, some of the elements are omitted, and each light beam is indicated by a line for easy understanding.
　図１３（ａ）に示す状態では、第１半導体レーザＬＤ１と第２半導体レーザＬＤ２との間隔が基準値より大きくなっているため、回折素子ＤＥ’を通過した第２光束と第３光束の０次回折光Ｂ２，Ｂ３が、それぞれ偏光ビームスプリッタＰＢＳを通過し、対物レンズＯＢＪにより光ディスク（ＢＤ／ＤＶＤ／ＣＤ）に集光され、その反射光が対物レンズＯＢＪを通過し、偏光ビームスプリッタＰＢＳで反射され、光検出器ＰＤの受光部３２Ｒの中央に位置するように光学系をセットすると、第１光束の－１次回折光Ｂ１が受光部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。 In the state shown in FIG. 13A, since the distance between the first semiconductor laser LD1 and the second semiconductor laser LD2 is larger than the reference value, 0 of the second light flux and the third light flux that have passed through the diffraction element DE ′. Next-order diffracted beams B2 and B3 pass through the polarizing beam splitter PBS, and are focused on the optical disc (BD / DVD / CD) by the objective lens OBJ. The reflected light passes through the objective lens OBJ and is reflected by the polarizing beam splitter PBS. If the optical system is set so as to be positioned at the center of the light receiving portion 32R of the photodetector PD, the −1st order diffracted light B1 of the first light beam is condensed below the light receiving portion 32R, and an inappropriate signal is generated. There is a risk of output.
　かかる場合、図１３（ｂ）に示すように、回折素子ＤＥ’を対物レンズＯＢＪから離間させるように移動させると、回折素子ＤＥ’を通過した第２光束と第３光束の０次回折光Ｂ２，Ｂ３の光路は変わらないのに対し、第１光束の－１次回折光Ｂ１は、受光部３２Ｒの中央に近づくようになる。即ち、回折素子ＤＥ’を対物レンズＯＢＪに対して相対的に移動することで、全ての光束を受光部３２Ｒに適切に集光することができるのである。尚、第１光束の－１次回折光Ｂ１が受光部３２Ｒの上方に集光してしまう場合には、回折素子ＤＥ’を対物レンズＯＢＪに接近させるように移動させればよい。 In this case, as shown in FIG. 13B, when the diffractive element DE ′ is moved away from the objective lens OBJ, the 0th-order diffracted light B2 of the second light flux and the third light flux that have passed through the diffractive element DE ′ are obtained. While the optical path of B3 does not change, the −1st order diffracted light B1 of the first light flux comes closer to the center of the light receiving part 32R. That is, by moving the diffractive element DE 'relative to the objective lens OBJ, all the light beams can be appropriately condensed on the light receiving unit 32R. If the −1st order diffracted light B1 of the first light beam is condensed above the light receiving portion 32R, the diffractive element DE ′ may be moved so as to approach the objective lens OBJ.
　（実施例）
　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。表１に実施例のデータを示す。実施例の回折素子は、表１に示すように、ストレートな４段の階段状回折構造を平行平板に形成したものである。表１の例に示すように、階段状回折構造に入射した入射光に対して同方向に出射する光束を０次回折光としたときに、この０次回折光に対して、階段状回折構造の段差がシフトしてゆく方向（表の例で右側）に曲げられた出射光束を正の（＋）次数回折光とし、逆側（表の例で左側）に曲げられた出射光束を負の（－）次数回折光とする。ここで、１段の光軸方向段差量Ｄは、Ｎ１を素材の屈折率とし、Ｎ２を空気の屈折率としたときに、Ｄ＝ｄｏｒ×λ１（Ｎ１－Ｎ２）で表される。但しｄｏｒ＝８．２５とした。横方向のピッチは所望する出射角に応じて任意に変更できる。かかる実施例によれば、波長λ１の光束が入射した場合、１次回折光が最も強度が高くなり、波長λ２，λ３の光束が入射した場合、０次回折光が最も強度が高くなる。 (Example)
Examples that can be used in the above-described embodiment will be described below. Table 1 shows data of the examples. As shown in Table 1, the diffractive element of the example has a straight four-step stair-like diffraction structure formed on a parallel plate. As shown in the example of Table 1, when the light beam emitted in the same direction with respect to the incident light incident on the stepped diffraction structure is set as the zeroth order diffracted light, the step difference of the stepped diffraction structure with respect to the zeroth order diffracted light. Is a positive (+) order diffracted light, and an outgoing light beam bent to the opposite side (left side in the table) is negative (- ) Order diffraction light. Here, the level difference D in one optical axis direction is expressed by D = dor × λ1 (N1−N2) where N1 is the refractive index of the material and N2 is the refractive index of air. However, dor = 8.25. The lateral pitch can be arbitrarily changed according to the desired emission angle. According to this embodiment, the first-order diffracted light has the highest intensity when a light beam with wavelength λ1 is incident, and the zero-order diffracted light has the highest intensity when light beams with wavelengths λ2 and λ3 are incident.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　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
　ＰＵ３　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 PU3 Optical pickup device QWP λ / 4 wave plate SN Sensor lens

Claims (13)

  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、光検出器とを有し、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おいて、
    　前記光源は、前記第２発光部と前記第３発光部が同一のチップ上に形成され、前記第１発光部が、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、
    　前記光検出器は、前記第１光束を受光する第１受光部と、前記第２光束を受光する第２受光部と、前記第３光束を受光する第３受光部とを有し、
    　前記光源と前記光検出器との間の光路内に、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が移動可能に配置されており、
    　前記回折素子は回折構造を有し、前記回折構造に前記第１光束が入射したときに発生するｍ次回折光が前記第１受光部に受光されるようになっており、また前記第２光束が入射したときに発生するｎ次回折光が前記第２受光部に受光されるようになっており、更に前記第３光束が入射したときに発生するｎ次回折光が前記第３受光部に受光されるようになっている（但し、ｍ、ｎは任意の整数であってｍ≠ｎ）ことを特徴とする光ピックアップ装置。     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 third light beam that emits a third light beam having a wavelength λ3 (λ2 <λ3). A light source including three light emitting units, an objective optical system, and a photodetector, and the light beam from the first light emitting unit is condensed on the information recording surface of the first optical disc by the objective optical system. In this way, a spot is formed, and information is recorded and / or reproduced on the first optical disk based on a signal from the photodetector that receives the reflected light, and a light beam from the second light emitting unit is reflected. A spot is formed by condensing on the information recording surface of the second optical disk by the objective optical system, and information is transmitted to the second optical disk based on a signal from the photodetector that receives the reflected light. Recording and / or reproduction of light 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. 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 different chip from the second light emitting unit and the third light emitting unit. And
    The photodetector includes a first light receiving unit that receives the first light beam, a second light receiving unit that receives the second light beam, and a third light receiving unit that receives the third light beam,
    A diffraction element through which the first light flux, the second light flux, and the third light flux pass in common is movably disposed in an optical path between the light source and the photodetector,
    The diffractive element has a diffractive structure, and m-th order diffracted light generated when the first light beam enters the diffractive structure is received by the first light receiving unit, and the second light beam is The nth order diffracted light generated when the light enters is received by the second light receiving unit, and the nth order diffracted light generated when the third light beam is incident is received by the third light receiving unit. An optical pickup device characterized in that m and n are arbitrary integers and m ≠ n.
  2. 　前記回折素子は、少なくとも前記光ピックアップ装置の光軸方向に移動可能に配置されていることを特徴とする請求項１に記載の光ピックアップ装置。 2. The optical pickup device according to claim 1, wherein the diffraction element is arranged to be movable at least in an optical axis direction of the optical pickup device.
  3. 　以下の式を満たすことを特徴とする請求項１又は２に記載の光ピックアップ装置。
    　３９５（ｎｍ）≦λ１≦４１５（ｎｍ）　　　（１）
    　６３０（ｎｍ）≦λ２≦７００（ｎｍ）　　　（２）
    　７５０（ｎｍ）≦λ３≦８５０（ｎｍ）　　　（３）     The optical pickup device according to claim 1, wherein the following expression is satisfied.
    395 (nm) ≦ λ1 ≦ 415 (nm) (1)
    630 (nm) ≦ λ2 ≦ 700 (nm) (2)
    750 (nm) ≦ λ3 ≦ 850 (nm) (3)
  4. 　前記回折素子による前記第１光束の回折光のうちｍ次回折光が最大の回折効率を有し、前記第２光束および前記第３光束の回折光のうちｎ次回折光が最大の回折効率を有することを特徴とする請求項１～３のいずれかに記載の光ピックアップ装置。 Of the diffracted light of the first light flux by the diffractive element, the mth order diffracted light has the maximum diffraction efficiency, and among the diffracted light of the second light flux and the third light flux, the nth order diffracted light has the maximum diffraction efficiency. The optical pickup device according to any one of claims 1 to 3, wherein:
  5. 　ｎ＝０であることを特徴とする請求項１～４のいずれかに記載の光ピックアップ装置。 5. The optical pickup device according to claim 1, wherein n = 0.
  6. 　前記回折素子が、前記光源から前記対物光学系までの光路中に配置されていることを特徴とする請求項１～５のいずれかに記載の光ピックアップ装置。 6. The optical pickup device according to claim 1, wherein the diffraction element is arranged in an optical path from the light source to the objective optical system.
  7. 　前記光ディスクからの反射光と前記光源から出射した光束とを分離するための光束分離素子を有し、前記回折素子が、前記光束分離素子と前記光検出器との間に配置されていることを特徴とする請求項１～５のいずれかに記載の光ピックアップ装置。 A light beam separating element for separating reflected light from the optical disc and light beam emitted from the light source, and the diffraction element is disposed between the light beam separating element and the photodetector. The optical pickup device according to any one of claims 1 to 5, wherein
  8. 　前記対物光学系は、単一の対物レンズで構成されていることを特徴とする請求項１～７のいずれかに記載の光ピックアップ装置。 The optical pickup device according to any one of claims 1 to 7, wherein the objective optical system includes a single objective lens.
  9. 　前記対物光学系は、前記第１光束を前記第１光ディスクに集光する第１対物レンズと、前記第２光束を前記第２光ディスクに集光し、前記第３光束を前記第３光ディスクに集光する第２対物レンズとを有することを特徴とする請求項１～７のいずれかに記載の光ピックアップ装置。 The objective optical system condenses the first light beam on the first optical disk, condenses the second light beam on the second optical disk, and collects the third light beam on the third optical disk. 8. The optical pickup device according to claim 1, further comprising a second objective lens that emits light.
  10. 　前記対物光学系は、前記第１光束を前記第１光ディスクに集光し、前記第２光束を前記第２光ディスクに集光する第１対物レンズと、前記第３光束を前記第３光ディスクに集光する第２対物レンズとを有することを特徴とする請求項１～７のいずれかに記載の光ピックアップ装置。 The objective optical system condenses the first light beam on the first optical disk, collects the second light beam on the second optical disk, and collects the third light beam on the third optical disk. 8. The optical pickup device according to claim 1, further comprising a second objective lens that emits light.
  11. 　前記第１受光部と、前記第２受光部と、前記第３受光部は、前記光ピックアップ装置の光軸に対し交差する方向に位置を異ならせて配置されていることを特徴とする請求項１～１０のいずれかに記載の光ピックアップ装置。 The first light receiving unit, the second light receiving unit, and the third light receiving unit are arranged at different positions in a direction intersecting an optical axis of the optical pickup device. The optical pickup device according to any one of 1 to 10.
  12. 　前記第１光束を、前記第２受光部又は前記第３受光部に受光させることにより、前記第１受光部として兼用させることを特徴とする請求項１～１１のいずれかに記載の光ピックアップ装置。 The optical pickup device according to any one of claims 1 to 11, wherein the first light beam is also used as the first light receiving unit by causing the second light receiving unit or the third light receiving unit to receive the first light beam. .
  13. 　前記第１受光部、前記第２受光部及び前記第３受光部が共通の受光部であることを特徴とする請求項１～１１のいずれかに記載の光ピックアップ装置。 12. The optical pickup device according to claim 1, wherein the first light receiving unit, the second light receiving unit, and the third light receiving unit are common light receiving units.
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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
JP2006302456A (en) * 2005-04-25 2006-11-02 Matsushita Electric Ind Co Ltd Optical pickup device
JP2008041234A (en) * 2006-07-10 2008-02-21 Ricoh Co Ltd Optical pickup and optical information processing device
JP2008052844A (en) * 2006-08-25 2008-03-06 Matsushita Electric Ind Co Ltd Optical pickup device
JP2008052826A (en) * 2006-08-24 2008-03-06 Funai Electric Co Ltd Optical pickup device

Patent Citations (6)

* 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
JP2006302456A (en) * 2005-04-25 2006-11-02 Matsushita Electric Ind Co Ltd Optical pickup device
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
JP2008052844A (en) * 2006-08-25 2008-03-06 Matsushita Electric Ind Co Ltd Optical pickup device

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