WO2007057988A1 - Optical disc device - Google Patents

Optical disc device Download PDF

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Publication number
WO2007057988A1
WO2007057988A1 PCT/JP2006/304380 JP2006304380W WO2007057988A1 WO 2007057988 A1 WO2007057988 A1 WO 2007057988A1 JP 2006304380 W JP2006304380 W JP 2006304380W WO 2007057988 A1 WO2007057988 A1 WO 2007057988A1
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WO
WIPO (PCT)
Prior art keywords
optical
lens
plastic
objective lens
optical pickup
Prior art date
Application number
PCT/JP2006/304380
Other languages
French (fr)
Japanese (ja)
Inventor
Shigeharu Kimura
Takeshi Shimano
Original Assignee
Hitachi, Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi, Ltd. filed Critical Hitachi, Ltd.
Priority to JP2007545159A priority Critical patent/JPWO2007057988A1/en
Publication of WO2007057988A1 publication Critical patent/WO2007057988A1/en

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Classifications

    • 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
    • G11B7/1359—Single prisms
    • 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
    • G11B7/123—Integrated head arrangements, e.g. with source and detectors mounted on the same substrate
    • G11B7/124—Integrated head arrangements, e.g. with source and detectors mounted on the same substrate the integrated head arrangements including waveguides
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/13—Optical detectors therefor
    • G11B7/131—Arrangement of detectors in a multiple array
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1372—Lenses
    • G11B7/1374—Objective lenses
    • 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
    • G11B7/1372—Lenses
    • G11B7/1376—Collimator lenses
    • 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
    • G11B7/1392—Means for controlling the beam wavefront, e.g. for correction of aberration
    • G11B7/13922—Means for controlling the beam wavefront, e.g. for correction of aberration passive
    • 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
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
    • G11B7/0857—Arrangements for mechanically moving the whole head
    • G11B7/08576—Swinging-arm positioners

Definitions

  • the present invention relates to an optical disc device, and more particularly to an optical disc device provided with a novel optical pickup.
  • Optical disc devices have been commercialized as CDs or DVDs! Since these devices mainly use an optical disk with a diameter of 12 cm, an optical disk drive corresponding to the size is used, and the optical disk pickup device (hereinafter referred to as an optical pickup) in the inside of the apparatus should be reduced in size so much. Not required.
  • an optical pickup the optical disk pickup device
  • the recording area is reduced and the storage capacity is reduced. In order to avoid this, it is desirable to increase the storage density, that is, to increase the NA (numerical aperture) of the objective lens that narrows the laser beam onto the optical disk.
  • Patent Document 1 discloses a technique for integrating a semiconductor laser chip and a prism on a substrate on which a photodetector is fabricated. Since CD and DVD have different wavelengths, miniaturization is achieved by stacking two layers of integrated substrates using semiconductor laser chips of each wavelength. In this case, there is a merit of light weight by avoiding double installation of an optical system such as an objective lens.
  • Patent Document 2 discloses an ultra-compact head that integrates a light source, a rising mirror, an objective lens, and a diffraction element that diffracts reflected light, and makes it easy to adjust the incident position on the light receiving element by moving the reflecting plate. It is described.
  • Patent Document 3 describes a method for reducing the size of a prism by mounting a semiconductor laser chip and a prism on the same substrate in order to reduce the thickness of an optical pickup.
  • Patent Document 1 Japanese Patent Laid-Open No. 11-144297
  • Patent Document 2 JP 2004-272951 A
  • Patent Document 3 Japanese Patent Laid-Open No. 5-28517
  • plastic When plastic is used as a lens material in order to reduce the weight of the optical pickup, plastic has a drawback that the temperature change of the refractive index is larger than that of glass.
  • the optical pickup has a heat source such as a semiconductor laser chip actuator, and the temperature of the lens rises as the device is used. For this reason, the wave front of the laser light emitted from the lens is shifted in an optimum state force, and the light condensing state is deteriorated. As a result, the signal due to the reflected light from the mark row or the pit row of the optical information medium has a large jitter due to a decrease in resolution or fluctuations in the reflected light, and the read information has many errors.
  • An object of the present invention is to reduce the optical aberration with respect to temperature change in an optical pickup using a plastic lens by reducing the size and weight and reducing the recording density.
  • the NA of the objective lens is 0.45 and 0.6.
  • NAO.85 larger than these values is adopted in order to keep the recording density high. If NA is increased, the laser spot can be reduced, so that the memory density can be increased. Under this condition, the effective diameter of the lens is reduced.
  • the size of the optical pickup is determined not only by the effective diameter of the lens, but of course the entire optical system. It is necessary to decide.
  • FIG. 2 shows the entire optical system of the optical pickup.
  • Laser light from the semiconductor laser chip 10 is emitted from the light emitting point at point L, reflected by the prism 111, and incident on the coupling lens 101. Further, the light is condensed on the information recording layer 310 of the information recording medium (optical disk) 300 by the objective lens 102.
  • the laser beam reflected from the information recording layer 310 returns to the lenses 102 and 101 and enters the prism 111.
  • Laser light is detected by the light detectors 221, 222, and 223 while repeatedly reflecting inside the prism.
  • the position of the photodetector 222 is set at the same optical distance as P.
  • P represents the intersection of the optical axis and the prism reflecting surface, and the optical distance is taken into account multiple reflections to the detector inside the prism.
  • the semiconductor laser chip 10, the prism 111, and the lenses 101 and 102 are fixed to a substrate 210 on which a photodetector is built, and their positions do not change relatively. Focusing and tracking control is performed by moving the substrate 210.
  • the substrate 210 is fixed to the actuator arm 201, and tracking and focusing control is performed by rotational movement of the tip of the actuator arm and movement of the information recording medium 300 in the direction of the rotational axis.
  • the photodetectors 221 and 223 use split detectors, can generate a focus error signal and a tracking error signal, and serve as a feedback signal for the swing arm activator.
  • the thickness of the prism 111 is shortened by the force depending on the distance LP, the height of the prism 111 can be lowered.
  • the distance PH increases as the distance LP is shortened, and the thickness of the optical pickup must be increased.
  • the point H represents an intersection with the optical axis of the surface of the lens 101 on the prism side. Therefore, in order to reduce the overall thickness, it is necessary to use a lens system that shortens the working distance including the distance LP and the distance PH.
  • FIG. 3 shows the lens system to be analyzed.
  • L is a laser light source
  • 101 is a plastic coupling lens
  • 102 is a plastic lens It is a plastic objective lens.
  • A is the effective diameter (radius) of the coupling lens
  • F is the lens interval
  • G is the thickness of the objective lens 102.
  • B is the direction cosine of ambient light. To define the direction of the direction cosine, consider the plane containing the optical axis and the ray, and consider the direction cosine with respect to a straight line perpendicular to the optical axis in this plane. The direction is positive when going away from the optical axis.
  • a and F, G, and B are used as control factors of Taguchi Methods J, and other factors include temperature change coefficient (represented as C), refractive index (denoted as D), Abbe number (E Assign control factors A through G to the L18 orthogonal table, excluding column number 1. Column number 1 is not used because it has two levels, and the remaining seven columns have three levels. Three control factor values can be set, and Table 1 shows the value of each control factor level.
  • the power with which an effective radius of about 1.5 mm is used for DVDs, etc. The value is about 1/6 for miniaturization. Since the refractive index becomes smaller as the temperature rises, a negative value is set, which is about 1 to 2 times larger in absolute value than the glass material.
  • Lens design is performed for each level combination determined by the orthogonal table for eight factors.
  • odd-order aspheric surfaces are used for all surfaces of the lens. . This makes it possible to design a lens that suppresses aberrations low.
  • the odd-order aspheric surface is given by the following equation.
  • c is the curvature at the vertex of the surface (unit: lZmm)
  • K is the conic coefficient
  • A, ⁇ , and C are the second-order, third-order, and fourth-order aspheric coefficients, respectively.
  • the image side wrinkle was set to 0.85
  • the object side wrinkle was set to 0.1.
  • the distance between the light source and the object-side surface (first surface) of the coupling lens 101 was set to 1.4 mm, and the shape of the coupling lens with a center thickness of 0.42 mm was a square type. Accordingly, the distance (LP + PH) in FIG. 2 can be shortened, so that the prism 111 can be made thin.
  • the 301 represents a polycarbonate cover layer with a thickness of 0.1 mm, and the working distance between the objective lens and the cover layer was 0.05 mm or more. Under these conditions, the object height (distance to the optical axis force L) at a temperature of 20 ° C was set to 0.0 and 0.01 mm, and the lens shape was measured for three wavelengths of 645 nm, 650 nm, and 655 nm. Perform optimization.
  • the level selection of the factor of A force G is performed by an orthogonal table, and 18 sets are set.
  • Table 2 shows the orthogonal table and the calculated S / N ratio for each setting.
  • the first row is not used, and the second row force is assigned the control factors in Table 1.
  • the number represents the level.
  • level 1 is set for all factors in the first column.
  • the SN ratio is calculated using rms wavefront aberration. Based on the lens shape optimized at 20 ° C, the wavefront aberration at 40 ° C and 60 ° C is calculated for 6 combinations of object height and wavelength.
  • r? represents the SN ratio
  • subscript represents the line number of the condition.
  • Figures 4 to 10 show the effects of effective radius, direction cosine, refractive index temperature change rate, refractive index, Abbe number, lens spacing, and objective lens center thickness, respectively.
  • FIG. 4 shows that aberrations due to temperature rise are smaller when the effective radius is smaller than 0.25 mm.
  • Figure 5 shows that aberrations are lower for direction cosines from 0 to negative values.
  • Fig. 6 shows that the smaller the refractive index temperature change coefficient force S, the smaller the aberration, and
  • Fig. 8 shows that the larger the Abbe number, the smaller the aberration.
  • Narrower lens spacing is preferable because the optical pickup can be made thinner.
  • the wavefront aberration for evaluation was calculated at a temperature of 60 ° C and a wavelength of 655 nm, so the larger object height of 0.0 mm or 0.01 mm was selected.
  • Figure 12 shows the analysis results. Since the wavefront aberration is smaller than 0.03 rms at the lens interval of about 0.2 mm, it can be seen that the lens can be used in this vicinity.
  • Table 5 shows the conditions used.
  • FIG. 13 shows the dependency of wavefront aberration on lens thickness. The same definition of wavefront aberration as in the case of lens spacing was used. It can be seen that the wall thickness can be used in the range of 0.32mm force and 0.36mm.
  • FIG. 14 shows the effective radius dependence of the wavefront aberration. If the wavefront aberration is 0.03 rms or less, the usable range is from the effective radius of 0.24 mm to 0.25 mm.
  • Table 7 shows an example of lens surface data designed based on the above analysis.
  • OBJ represents an object plane
  • IMG represents an image plane
  • # 1 represents the surface of the coupling lens 101 in FIG. 3 on the light source side
  • STO indicates that it is a diaphragm surface. If it is not a diaphragm surface, # 2 is displayed.
  • STO represents the surface of the coupling lens 101 on the optical disc side
  • # 3 represents the surface of the objective lens 102 on the light source side
  • # 4 represents the surface of the objective lens 102 on the optical disc side
  • # 5 represents the light source side surface of the optical disc cover layer 301
  • # 6 represents the back surface of the cover layer.
  • the TYPE column indicates the surface type, S means spherical, and A means aspherical.
  • RADIUS indicates the radius of curvature, and the negative sign of the radius of curvature indicates that the center is on the light source side. Infinity indicates that the radius is infinite.
  • RADIUS here is the reciprocal of c (curvature) in Equation 1.
  • DISTANCE is the surface interval.
  • the GLASS column represents the material from the corresponding surface to the next surface, 500000.550 represents a relative refractive index of 1.5 at 20 ° C, an Abbe number of 55.0, POLYCARB represents polycarbonate, and AIR represents air. .
  • the INDEX column indicates the absolute refractive index at 20 ° C
  • the APY-Y column indicates the aperture radius
  • the AP column C indicates a circular aperture.
  • Table 8 shows the aspheric coefficients.
  • # 1 to # 4 represent the same surface as Table 7, and all the surfaces are odd-order aspheric surfaces represented by ODD.
  • K and A, B, and C are coefficients for representing an odd-order aspheric surface, and are the same as those used in Equation (1).
  • the wavefront aberration of 0.06944 rms can be obtained under the conditions of an environmental temperature of 60 ° C, a wavelength of 655 nm, and an object height of 0.01 mm.
  • the wavefront aberration can be reduced even when the temperature of the plastic lens rises by making all four surfaces of the two lenses used in the optical pickup an odd-order aspheric surface. As a result, a good light spot can be formed on the information recording medium, and read errors can be reduced.
  • the use of plastic for the lens of the optical pickup makes it possible to reduce the weight of the lens to be moved and thereby reduce the heat generated.
  • the optical pickup of the present invention uses a swing arm. Since the swing arm controls the movement of the entire optical system of the optical pickup, the weight is heavy, and the current that flows to the actuator for rotating or bending the swing arm increases, and the amount of heat generation increases. As a result, the temperature inside the optical pickup rises, causing a large change in the refractive index of the plastic lens. According to the present invention, since the load applied to the swing arm can be reduced, the power consumption can be reduced and the temperature rise of the optical pickup can be suppressed.
  • FIG. 1 is a schematic sectional view showing an embodiment of an optical pickup according to the present invention.
  • FIG. 2 is a schematic diagram of an optical pickup.
  • FIG. 3 is a diagram showing a lens system.
  • FIG. 5 is a diagram showing the main effect of direction cosine.
  • FIG. 6 is a diagram showing the main effect of the refractive index temperature change coefficient.
  • FIG. 7 is a diagram showing the main effect of refractive index.
  • FIG. 8 Diagram showing the main effect of Abbe number.
  • FIG. 9 is a diagram showing the main effect of lens spacing.
  • FIG. 10 is a diagram showing the main effect of the center thickness of the objective lens.
  • FIG. 11 is a graph showing the dependence of wavefront aberration on the direction cosine of the most peripheral light.
  • FIG. 12 is a graph showing the lens interval dependence of wavefront aberration.
  • FIG. 13 is a graph showing the dependence of wavefront aberration on the center thickness of an objective lens.
  • FIG. 14 is a graph showing the dependence of wavefront aberration on the effective radius of a coupling lens.
  • FIG. 15 is a diagram showing the temperature dependence of the wavefront aberration of the lens system used in the example.
  • FIG. 16 is a diagram showing a photodetector pattern used in the example.
  • FIG. 17 is a diagram showing an outline of an optical disc apparatus equipped with the optical pickup of the present invention.
  • FIG. 17 is a schematic diagram of an optical disc apparatus.
  • Fig. 17 (a) is a plan view and Fig. 17 (b) is a side view.
  • the optical disc 300 is fixed to the rotating shaft of the spindle motor 402 and is driven to rotate.
  • the optical pickup 401 is attached to the actuator arm 201, and the actuator arm 201 can be finely moved by the focus actuator 407 in the optical axis direction of the objective lens of the optical pickup. Further, the actuator arm 201 and the focus actuator 407 are fixed to the swing arm 403 together with the counter balance 405, and the swing arm 403 uses the swing motor 404 to connect the optical pickup 401 to the optical device. Drive in the radial direction of the K300. Signal input / output to the optical pickup is connected to the control circuit 406 by a flexible plastic cable (not shown).
  • FIG. 1 shows an embodiment of an optical pickup according to the present invention, and is a schematic view of a cross section passing through the optical axis of the optical pickup.
  • the optical system shown in Fig. 1 is the same as the schematic optical configuration shown in Fig. 2, but Fig. 1 shows an optical system based on the design result of the plastic lens.
  • the size of the light beam was divided.
  • Reference numeral 10 denotes a semiconductor laser chip having a wavelength of 650 nm, which is reflected by the glass prism 111 having a refractive index of 1. 725829.
  • the coupling lens 103 and the objective lens 104 use an optical plastic called ZEONEX330R (manufactured by Nippon Zeon Co., Ltd.).
  • the plastic lens is made by injection molding, and at the same time as the lens part that refracts light, a flat support part for installation on the upper part of the prism 111 is also molded.
  • the coupling lens 103 is a meniscus type, and is effective in shortening the working distance between the laser light source and the coupling lens 103 when the NA (0.1) on the laser light source side and the effective radius are fixed. It becomes.
  • the direction cosine of the most ambient light between the coupling lens 103 and the object lens 104 is designed to be 0.06.
  • the coupling lens 103 is bonded onto the prism 111, and the objective lens 104 is bonded onto the coupling lens 103.
  • the NA of the objective lens 104 is 0.85, and the laser light is focused on the information recording layer through the 0.1 mm cover layer of the optical disk.
  • the reflected light from the information recording layer returns to the objective lens 104 and the coupling lens 103 and then enters the prism 111 and is reflected therein a plurality of times.
  • An aluminum thin film is deposited on the top of the prism to increase the reflectivity.
  • 221, 222, and 223 are photodetectors, and the height and position of the prism 111 and the entrance position of the reflected light are appropriately set so that the light spot becomes small at the photodetector 222 when the optical disk is at the in-focus position. It is.
  • the photodetectors 221 and 223 are for generating a focus error signal and a tracking error signal, and the signal from the photodetector 222 is an RF signal for reading out recorded information. These photodetectors are formed on the silicon substrate 211, and are bonded to the swing arm 201. The swing arm can be moved and bent in the direction perpendicular to the paper surface and the vertical direction in the paper surface by the actuator, and the appropriate track position and focus on the information recording layer of the optical disc 301 can be determined by feedback signals from the optical detectors 221 and 223. Position kept It is.
  • the way of reading the table is the same as Table 7 and Table 8.
  • the height of the prism in Fig. 1 was 0.65 mm
  • the distance between the laser light source and the prism was 1.1 mm
  • the height of the optical axis was set at a silicon substrate surface force of 0.45 mm.
  • the height of the prism bottom force objective lens to the exit surface is about 1.7 mm.
  • the thickness of the silicon substrate and swing arm is 0.5 mm and 1. Omm, respectively, the total thickness is about 3.2 mm.
  • Laser light source The distance to the right end of the prism 111 is about 3 mm, and the width of the prism 111 in the direction perpendicular to the paper surface can be about 0.8 mm. In this way, the optical system of the optical pickup can be made small, and since plastic is used for the lens support portion, the weight can be reduced.
  • Figure 16 shows the relationship between the shape of the photodetectors 221, 222, and 223 of the example, the focus error signal (FES), the tracking error signal (TES), the RF signal (RFS), and the output of the photodetector. Show.
  • the shape of the photodetector is that of the objective lens when viewed from the optical axis direction of the objective lens, that is, the optical disk side force silicon substrate, and there is a laser light source in the left direction.
  • the focus error signal is generated from the three-divided photodetector 221 (M, N, O) and the six-divided photodetector 223 (P, Q, R, S, T, U).
  • the k is used to compensate for a decrease in the total amount of light incident on the photodetector due to a decrease in the amount of light each time it is reflected in the prism.
  • the light spot falling on the detector 221 becomes smaller when the information recording medium is moved a minute distance from the objective lens, and 223 The shape of the light spot falling on the light detector becomes larger.
  • the light spot falling on the detector 221 increases and the shape of the light spot falling on the detector 223 increases. This shape change is detected as an FES signal, and the swing end actuator is controlled.
  • the tracking error signal is formed from the photodetector 223.
  • An optical pickup is installed so that the direction of the track of the optical information recording medium and the direction of the two-divided line of the photodetector 223 are substantially coincident. If tracking is shifted, the total of the S, T, and U pairs of the detector 223 There is an imbalance between the light intensity and the total light intensity of the PQR pair. This is the tracking error signal.
  • the optical pickup is reduced in size and weight, and the convenience of the optical disc apparatus is improved. can do.
  • the optical disk drive including the optical pickup can be downsized.
  • a large amount of data can be easily captured.
  • a light plastic lens it is possible to move the swing arm in the optical pickup at a high speed, thereby shortening the data access time.
  • the plastic lens is easier to manufacture than the glass mold lens, the optical pickup can be manufactured at low cost.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Head (AREA)

Abstract

In an optical pickup using a plastic lens, sizes, weight and thickness are reduced and optical aberration is suppressed against temperature change without deteriorating recoding density. Wavefront aberration is reduced by permitting four planes of a coupling lens (103) and an objective lens (104) to be odd-order aspheric surfaces and direction cosine of the maximum ambient light between the lenses to be a negative value. The optical pickup is reduced in sizes, weight and thickness by reducing the effective radius of a meniscus coupling lens.

Description

明 細 書  Specification
光ディスク装置  Optical disk device
技術分野  Technical field
[0001] 本発明は、光ディスク装置に関し、より詳細には新規な光ピックアップを備えた光デ イスク装置に関する。  TECHNICAL FIELD [0001] The present invention relates to an optical disc device, and more particularly to an optical disc device provided with a novel optical pickup.
背景技術  Background art
[0002] 光ディスク装置は、 CDあるいは DVDが商品化されて!/、る。これらの装置は主に直 径 12cmの光ディスクを使用するため、その大きさに応じた光ディスクドライブが使用 されおり、その内部にある光ディスクピックアップ装置（以下、光ピックアップという）は それほど小型化することを要求されていない。しかし、光ディスクドライブの携帯用途 でのさらなる利便性の向上を考えたとき、光ディスクの小径化とそれを読み書きする 光ディスクドライブもさらに小型化及び軽量化、薄型化が必要になる。このためには、 内部にある光ピックアップを小型かつ軽量、薄型化する必要がある。また、携帯用に 光ディスクを小型化したとき、記録のための面積が小さくなり記憶容量が小さくなつて しまう。これを避けるため、記憶密度を大きくすること、すなわち、光ディスクにレーザ 光を絞り込む対物レンズの NA (開口数)を大きくとることが望まれる。  [0002] Optical disc devices have been commercialized as CDs or DVDs! Since these devices mainly use an optical disk with a diameter of 12 cm, an optical disk drive corresponding to the size is used, and the optical disk pickup device (hereinafter referred to as an optical pickup) in the inside of the apparatus should be reduced in size so much. Not required. However, considering further improvements in the convenience of portable use of optical disc drives, it is necessary to reduce the diameter of optical discs and to further reduce the size, weight, and thickness of optical disc drives that read and write data. For this purpose, it is necessary to reduce the size, weight and thickness of the optical pickup inside. In addition, when an optical disc is miniaturized for portable use, the recording area is reduced and the storage capacity is reduced. In order to avoid this, it is desirable to increase the storage density, that is, to increase the NA (numerical aperture) of the objective lens that narrows the laser beam onto the optical disk.
[0003] 光ピックアップの小型軽量ィ匕の例として、特許文献 1に半導体レーザチップとプリズ ムとを光検出器が作製された基板上に集積する技術が開示されている。 CDと DVD では波長が異なるのでそれぞれの波長の半導体レーザチップを用いた集積基板を 2 段重ねにして小型化を図っている。この場合、対物レンズ等の光学系が 2重に設置さ れるのを避けることでの軽量ィ匕のメリットがある。特許文献 2には、光源と立ち上げミラ 一、対物レンズ、反射光を回折する回折素子を一体ィ匕し、反射板の移動により受光 素子への入射位置の調整を容易にした超小型ヘッドが記載されて 、る。このヘッドは スイングアーム上に取り付けられ、ヘッド全体が駆動され、フォーカス及びトラッキング 制御がなされる。特許文献 3には、光ピックアップの薄型化に関し、半導体レーザチ ップとプリズムを同一基板上に取り付け、プリズムの大きさを小さくする方法が記載さ れている。 特許文献 1：特開平 11-144297号公報 [0003] As an example of a small and lightweight optical pickup, Patent Document 1 discloses a technique for integrating a semiconductor laser chip and a prism on a substrate on which a photodetector is fabricated. Since CD and DVD have different wavelengths, miniaturization is achieved by stacking two layers of integrated substrates using semiconductor laser chips of each wavelength. In this case, there is a merit of light weight by avoiding double installation of an optical system such as an objective lens. Patent Document 2 discloses an ultra-compact head that integrates a light source, a rising mirror, an objective lens, and a diffraction element that diffracts reflected light, and makes it easy to adjust the incident position on the light receiving element by moving the reflecting plate. It is described. This head is mounted on a swing arm, the entire head is driven, and focus and tracking control is performed. Patent Document 3 describes a method for reducing the size of a prism by mounting a semiconductor laser chip and a prism on the same substrate in order to reduce the thickness of an optical pickup. Patent Document 1: Japanese Patent Laid-Open No. 11-144297
特許文献 2：特開 2004-272951号公報  Patent Document 2: JP 2004-272951 A
特許文献 3：特開平 5-28517号公報  Patent Document 3: Japanese Patent Laid-Open No. 5-28517
発明の開示  Disclosure of the invention
発明が解決しょうとする課題  Problems to be solved by the invention
[0004] 光ピックアップを小型かつ厚さの薄いものにするためには、レーザ光を集光するレ ンズ系を小さくする必要がある。しかも、記憶容量を大きく保つ必要があるため、 NA を大きくしておく必要がある。特許文献 1から 3は、レンズの大きさについては言及して いない。また、光ピックアップでは、情報記録面でレーザ光を適切な位置に集光する ためにレンズの位置を制御する必要がある。このとき、光ピックアップの重量はできる だけ軽い方がよい。重いと、レンズを制御するためのァクチユエータの消費電力が大 きくなるとともに、発熱量も大きくなり、光ピックアップの温度を上昇させる。  [0004] In order to make the optical pickup small and thin, it is necessary to reduce the lens system for condensing the laser beam. Moreover, since the storage capacity needs to be kept large, it is necessary to increase NA. Patent documents 1 to 3 do not mention the size of the lens. In addition, in the optical pickup, it is necessary to control the position of the lens in order to focus the laser beam at an appropriate position on the information recording surface. At this time, the weight of the optical pickup should be as light as possible. If it is heavy, the power consumption of the actuator for controlling the lens increases and the amount of heat generated increases, raising the temperature of the optical pickup.
[0005] 光ピックアップの重量を軽くするためにレンズの材料としてプラスチックを使用する 場合、プラスチックはガラスと比較して屈折率の温度変化が大き 、と 、う欠点がある。 光ピックアップには半導体レーザチップゃァクチユエータなどの発熱源があり、レンズ の温度も装置の使用により上昇する。このため、レンズから出射したレーザ光の波面 が最適な状態力 ずれてしまい、集光状態が悪くなる。その結果、光情報媒体のマ 一ク列ゃピット列からの反射光による信号は、分解能の低下や反射光の変動により、 ジッターの大きいものになり、読み出した情報にエラーが多くなつてしまう。  [0005] When plastic is used as a lens material in order to reduce the weight of the optical pickup, plastic has a drawback that the temperature change of the refractive index is larger than that of glass. The optical pickup has a heat source such as a semiconductor laser chip actuator, and the temperature of the lens rises as the device is used. For this reason, the wave front of the laser light emitted from the lens is shifted in an optimum state force, and the light condensing state is deteriorated. As a result, the signal due to the reflected light from the mark row or the pit row of the optical information medium has a large jitter due to a decrease in resolution or fluctuations in the reflected light, and the read information has many errors.
[0006] 本発明の目的は、プラスチックレンズを使用した光ピックアップにおいて、小型'軽 量'薄型化を図り、かつ記録密度を低下させず、温度変化に対して光学収差を小さく 抑えることである。  An object of the present invention is to reduce the optical aberration with respect to temperature change in an optical pickup using a plastic lens by reducing the size and weight and reducing the recording density.
課題を解決するための手段  Means for solving the problem
[0007] CDや DVDでは対物レンズの NAが 0. 45, 0. 6である。本発明では、記録密度を 大きく保っため、これらの値より大きな NAO. 85を採用する。 NAを大きくすれば、レ 一ザスポットを小さくすることができるので、記憶密度を大きくすることができる。この条 件の下、レンズの有効径を小さくする。光ピックアップの大きさはレンズの有効径だけ でなぐ当然光学系全体で決まるものであるので、採用する全体の光学系の構成を 決めておく必要がある。 [0007] For CDs and DVDs, the NA of the objective lens is 0.45 and 0.6. In the present invention, NAO.85 larger than these values is adopted in order to keep the recording density high. If NA is increased, the laser spot can be reduced, so that the memory density can be increased. Under this condition, the effective diameter of the lens is reduced. The size of the optical pickup is determined not only by the effective diameter of the lens, but of course the entire optical system. It is necessary to decide.
[0008] 図 2に、光ピックアップの全体の光学系を示す。半導体レーザチップ 10からのレー ザ光は点 Lの発光点から出射し、プリズム 111で反射され、カップリングレンズ 101へ 入射する。さらに対物レンズ 102で、情報記録媒体 (光ディスク） 300の情報記録層 3 10へ集光される。情報記録層 310から反射されたレーザ光はレンズ 102及び 101を 戻り、プリズム 111の内部に入射する。プリズム内部では反射を繰り返しながら、光検 出器 221, 222, 223でレーザ光が検出されていく。光検出器 222の位置は、距離し Pと同じ光学的距離に設置されている。 Pは光軸とプリズム反射面との交点を表して おり、光学的距離はプリズム内部での検出器までの複数回の反射を考慮したもので ある。  FIG. 2 shows the entire optical system of the optical pickup. Laser light from the semiconductor laser chip 10 is emitted from the light emitting point at point L, reflected by the prism 111, and incident on the coupling lens 101. Further, the light is condensed on the information recording layer 310 of the information recording medium (optical disk) 300 by the objective lens 102. The laser beam reflected from the information recording layer 310 returns to the lenses 102 and 101 and enters the prism 111. Laser light is detected by the light detectors 221, 222, and 223 while repeatedly reflecting inside the prism. The position of the photodetector 222 is set at the same optical distance as P. P represents the intersection of the optical axis and the prism reflecting surface, and the optical distance is taken into account multiple reflections to the detector inside the prism.
[0009] 半導体レーザチップ 10とプリズム 111、レンズ 101, 102は光検出器が作り付けら れた基板 210に固定されていて、相対的に位置が変化することはないものとする。フ オーカシング及びトラッキング制御は基板 210を移動させることで行う。基板 210はァ クチユエータアーム 201に固定され、ァクチユエータアームの先端の回転移動や情 報記録媒体 300の回転軸方向への移動により、トラッキング及びフォーカシング制御 が行われる。光検出器 221及び 223は分割検出器を用いており、フォーカスエラー 信号及びトラッキングエラー信号を生成することができ、スイングアームのァクチユエ ータ用のフィードバック信号となる。  It is assumed that the semiconductor laser chip 10, the prism 111, and the lenses 101 and 102 are fixed to a substrate 210 on which a photodetector is built, and their positions do not change relatively. Focusing and tracking control is performed by moving the substrate 210. The substrate 210 is fixed to the actuator arm 201, and tracking and focusing control is performed by rotational movement of the tip of the actuator arm and movement of the information recording medium 300 in the direction of the rotational axis. The photodetectors 221 and 223 use split detectors, can generate a focus error signal and a tracking error signal, and serve as a feedback signal for the swing arm activator.
[0010] プリズム 111の厚さは距離 LPに依存する力 短くすればプリズム 111の高さを低く することができる。しかし、距離 LPと距離 PHをカ卩えたレンズの作動距離が一定である ならば、距離 LPを短くすると距離 PHが大きくなり、光ピックアップの厚さは厚くならざ るを得ない。ここに、点 Hはレンズ 101のプリズム側の面の光軸との交点を表す。した がって、全体の厚さを薄くするためには、距離 LPと距離 PHを加えた作動距離の短く なるようなレンズ系を使用する必要がある。  [0010] If the thickness of the prism 111 is shortened by the force depending on the distance LP, the height of the prism 111 can be lowered. However, if the working distance of the lens with the distance LP and the distance PH is constant, the distance PH increases as the distance LP is shortened, and the thickness of the optical pickup must be increased. Here, the point H represents an intersection with the optical axis of the surface of the lens 101 on the prism side. Therefore, in order to reduce the overall thickness, it is necessary to use a lens system that shortens the working distance including the distance LP and the distance PH.
[0011] レンズ系には複数のパラメータがあり、それぞれがレンズの特性に影響を与える。  There are a plurality of parameters in the lens system, and each affects the characteristics of the lens.
すべての組み合わせにつ 、て影響を計算するのは時間がかかるので、品質工学で パラメータ設計に使用される「Taguchi Methods」を利用する。解析するレンズ系を図 3 に示す。 Lはレーザ光の点光源、 101はプラスチックのカップリングレンズ、 102はプ ラスチックの対物レンズである。 Aはカップリングレンズの有効径（半径）、 Fはレンズ 間隔、 Gは対物レンズ 102の肉厚である。 Bは周辺光の方向余弦である。方向余弦 の方向の定義は、光軸と光線を含む面を考え、この面内の光軸に垂直な直線に対し て方向余弦を考える。方向は、光軸から離れていく方向を正とする。レンズ間の光線 が対物レンズに向かって収束していく場合、方向余弦は負の符号をとることになる。 Aと F, G, Bを「Taguchi MethodsJの制御要因とし、その他の要因としてレンズに使用 するプラスチックの屈折率の温度変化係数 (Cと表記）、屈折率 (Dと表記）、アッベ数 (Eと表記）を選ぶ。 Aから Gの制御因子を L18の直交表に列番 1を除いて割り当てる 。列番 1は水準が二つなので不使用とした。残りの 7列は 3水準あり適当に制御要因 の数値を 3個設定することができる。表 1に制御因子のそれぞれの水準の値を示す。 For all combinations, it takes time to calculate the impact, so use “Taguchi Methods”, which is used for quality engineering and parameter design. Figure 3 shows the lens system to be analyzed. L is a laser light source, 101 is a plastic coupling lens, 102 is a plastic lens It is a plastic objective lens. A is the effective diameter (radius) of the coupling lens, F is the lens interval, and G is the thickness of the objective lens 102. B is the direction cosine of ambient light. To define the direction of the direction cosine, consider the plane containing the optical axis and the ray, and consider the direction cosine with respect to a straight line perpendicular to the optical axis in this plane. The direction is positive when going away from the optical axis. If the light rays between the lenses converge toward the objective lens, the direction cosine will have a negative sign. A and F, G, and B are used as control factors of Taguchi Methods J, and other factors include temperature change coefficient (represented as C), refractive index (denoted as D), Abbe number (E Assign control factors A through G to the L18 orthogonal table, excluding column number 1. Column number 1 is not used because it has two levels, and the remaining seven columns have three levels. Three control factor values can be set, and Table 1 shows the value of each control factor level.
[表 1]
Figure imgf000006_0001
[table 1]
Figure imgf000006_0001
Figure imgf000006_0002
Figure imgf000006_0002
[0012] DVDなどでは有効半径 1. 5mm程度のレンズが使用される力 小型化のために 6 分の 1程度の値とした。屈折率は温度上昇に伴い小さくなるので、負の値を設定し、 ガラス材料に比較して絶対値で 1から 2乗程度大きい値とした。  [0012] The power with which an effective radius of about 1.5 mm is used for DVDs, etc. The value is about 1/6 for miniaturization. Since the refractive index becomes smaller as the temperature rises, a negative value is set, which is about 1 to 2 times larger in absolute value than the glass material.
[0013] 8個の因子に対して直交表で決まるそれぞれの水準の組み合わせに対して、レン ズ設計を行う。本発明では、レンズのすべての面に対して、奇数次非球面を使用する 。これにより収差を低く抑えるレンズの設計が可能になる。奇数次非球面は次式で与 えられる。 [0013] Lens design is performed for each level combination determined by the orthogonal table for eight factors. In the present invention, odd-order aspheric surfaces are used for all surfaces of the lens. . This makes it possible to design a lens that suppresses aberrations low. The odd-order aspheric surface is given by the following equation.
[数 1]  [Number 1]
z(h) =—— . Ck ^ + A - h2 + B - hs + C - h4 -(1) z (h) = -. Ck ^ + A - h 2 + B - h s + C - h 4 - (1)
[0014] ここに、 cは面の頂点での曲率（単位： lZmm)、 Kはコーニック係数、 A, Β, Cはそ れぞれ 2次， 3次， 4次の非球面係数である。像側 ΝΑは前述のように 0. 85とし、物体 側の ΝΑは 0. 1とした。光源とカップリングレンズ 101の物体側の面 (第 1面）との距離 を 1. 4mmに設定し、中心肉厚 0. 42mmのカップリングレンズの形状はメ-スカス型 とした。これにより、図 2における距離 (LP+PH)を短くできるので、プリズム 111を薄 くすることが可能になる。また、 301は厚さ 0. 1mmのポリカーボネートのカバー層を 表しており、対物レンズとカバー層までの作動距離は 0. 05mm以上とした。このよう な条件の下、温度 20°Cにおいて物体の高さ（光軸力もの Lまでの距離）を 0. 0及び 0 . 01mmとし、波長 645nm、 650nm、 655nmの 3波長について、レンズ形状の最適 化を行う。 [0014] where c is the curvature at the vertex of the surface (unit: lZmm), K is the conic coefficient, and A, Β, and C are the second-order, third-order, and fourth-order aspheric coefficients, respectively. As described above, the image side wrinkle was set to 0.85, and the object side wrinkle was set to 0.1. The distance between the light source and the object-side surface (first surface) of the coupling lens 101 was set to 1.4 mm, and the shape of the coupling lens with a center thickness of 0.42 mm was a square type. Accordingly, the distance (LP + PH) in FIG. 2 can be shortened, so that the prism 111 can be made thin. 301 represents a polycarbonate cover layer with a thickness of 0.1 mm, and the working distance between the objective lens and the cover layer was 0.05 mm or more. Under these conditions, the object height (distance to the optical axis force L) at a temperature of 20 ° C was set to 0.0 and 0.01 mm, and the lens shape was measured for three wavelengths of 645 nm, 650 nm, and 655 nm. Perform optimization.
[0015] A力 Gの因子の水準選択は直交表により行われ、 18組の設定がなされる。表 2に 直交表とそれぞれの設定に対する SN比の計算結果を示す。  [0015] The level selection of the factor of A force G is performed by an orthogonal table, and 18 sets are set. Table 2 shows the orthogonal table and the calculated S / N ratio for each setting.
[表 2] [Table 2]
e A B C D E F G e A B C D E F G
No 1 2 3 4 5 6 7 8 SN比（dB) No 1 2 3 4 5 6 7 8 SN ratio (dB)
1 1 1 1 1 1 1 1 1 20.31 1 1 1 1 1 1 1 1 20.3
2 1 1 2 2 2 2 2 2 り 2 . 15.62 1 1 2 2 2 2 2 2 2 .15.6
3 1 1 3 3 3 3 3 3 r 12.13 1 1 3 3 3 3 3 3 r 12.1
4 1 2 1 1 2 2 3 3 28.64 1 2 1 1 2 2 3 3 28.6
5 1 2 2 2 3 3 1 1 " 5 23.15 1 2 2 2 3 3 1 1 "5 23.1
6 1 2 3 3 1 1 2 2 6 20.76 1 2 3 3 1 1 2 2 6 20.7
7 1 3 1 2 1 3 2 3 " 1 28.27 1 3 1 2 1 3 2 3 "1 28.2
8 1 3 2 3 2 1 3 1 n a 8.858 1 3 2 3 2 1 3 1 n a 8.85
9 1 3 3 1 3 2 1 2 25.39 1 3 3 1 3 2 1 2 25.3
10 2 1 1 3 3 2 2 1 12.110 2 1 1 3 3 2 2 1 12.1
11 2 1 2 1 1 3 3 2 21.711 2 1 2 1 1 3 3 2 21.7
12 2 1 3 2 2 1 1 3 9.2612 2 1 3 2 2 1 1 3 9.26
13 2 2 1 2 3 1 3 2 13 24.813 2 2 1 2 3 1 3 2 13 24.8
14 2 2 2 3 1 2 1 3 V H 24.914 2 2 2 3 1 2 1 3 V H 24.9
15 2 2 3 1 2 3 2 1 5 30.215 2 2 3 1 2 3 2 1 5 30.2
16 2 3 1 3 2 3 1 2 16 26.716 2 3 1 3 2 3 1 2 16 26.7
17 2 3 2 1 3 1 2 3 30.017 2 3 2 1 3 1 2 3 30.0
18 2 3 3 2 1 2 3 1 21.4 前述のように 1列目は使用せず、 2列目力 表 1の制御因子を割り当ててある。数字 は水準を表し、例えば、 1列目の条件ではすべての因子に水準 1が設定されることに なる。 SN比の計算は rms波面収差を用いて計算する。 20°Cにおいて最適化された レンズ形状にぉ 、て、物体高と波長の組み合わせた 6通りにつレ、て 40°C及び 60°C での波面収差を計算する。 3通りの温度で計算された 18個の波面収差の 2乗の平均 をとり、それを σ 2としたとき、 Si¾^¾S/N= 10 X log (l/ a 2) (dB)と表される。そも そも、 σ 2のなかの 20°Cに関連する値は最適化されたものなので σ 2への影響は小さ ぐ 40°C及び 60°Cでの波面収差に大きく影響されるものである。すなわち、温度上 昇による波面収差が小さい場合、 σ 2の値は大きくなる。 18 2 3 3 2 1 2 3 1 21.4 As described above, the first row is not used, and the second row force is assigned the control factors in Table 1. The number represents the level. For example, level 1 is set for all factors in the first column. The SN ratio is calculated using rms wavefront aberration. Based on the lens shape optimized at 20 ° C, the wavefront aberration at 40 ° C and 60 ° C is calculated for 6 combinations of object height and wavelength. When the average of the squares of 18 wavefront aberrations calculated at three different temperatures is taken as σ 2 , it is expressed as Si¾ ^ ¾S / N = 10 X log (l / a 2 ) (dB) The In the first place, the value related to 20 ° C in σ 2 is optimized, so the effect on σ 2 is small. It is greatly affected by wavefront aberrations at 40 ° C and 60 ° C. That is, when the wavefront aberration due to temperature rise is small, the value of σ 2 becomes large.
[0017] 次に、 SN比に対する各制御因子の主効果の大きさについて計算する。制御因子 の各水準での主効果は関係する SN比の平均で表される。例えば、制御因子 Αの水 準 1の主効果を A1をしたとき、 Al = ( 7? + 7} + 7} + 7} + 7} + 7} ) Ζ6のように Next, the magnitude of the main effect of each control factor on the SN ratio is calculated. The main effect at each level of the control factor is expressed as the mean of the signal-to-noise ratio involved. For example, when the main effect of level 1 of control factor Α is A1, Al = (7? + 7} + 7} + 7} + 7} + 7}) Ζ6
1 2 3 10 11 12  1 2 3 10 11 12
表される。 r?は SN比を表し、添え字は条件の行番号を表す。同様に水準 2の主効果 Α2は、 Α2= ( + 7? + 7? + 7? + 7? + 7? ) Ζ6と表される。図 4から図 10に Αか  expressed. r? represents the SN ratio, and the subscript represents the line number of the condition. Similarly, level 2 main effect Α2 is expressed as Α2 = (+ 7? + 7? + 7? + 7? + 7?) Ζ6. From Fig. 4 to Fig. 10
4 5 6 13 14 15  4 5 6 13 14 15
ら Gの主効果を示す。図 4から図 10は、それぞれ有効半径、方向余弦、屈折率温度 変化率、屈折率、アッベ数、レンズ間隔、対物レンズ中心肉厚の効果を表す。  Show the main effect of G. Figures 4 to 10 show the effects of effective radius, direction cosine, refractive index temperature change rate, refractive index, Abbe number, lens spacing, and objective lens center thickness, respectively.
[0018] 図 4には、有効半径は 0. 25mmより小さい方が温度上昇による収差が小さいことが 示されている。図 5は、方向余弦が 0から負の値の方が収差が低くなることを示してい る。図 6は屈折率温度変化係数力 S小さい方が収差が小さくなり、図 8はアッベ数が大 きい方が収差が小さくなること示している力 これらはレンズ材料の特性を考えれば 当然の帰結である。図 7は、屈折率が 1. 5のように小さくても温度変化に対して収差 の発生を小さくできることを示している。図 9は、レンズ間隔は 0. 2mmより長い方が収 差が小さくなることを示して 、る。  [0018] FIG. 4 shows that aberrations due to temperature rise are smaller when the effective radius is smaller than 0.25 mm. Figure 5 shows that aberrations are lower for direction cosines from 0 to negative values. Fig. 6 shows that the smaller the refractive index temperature change coefficient force S, the smaller the aberration, and Fig. 8 shows that the larger the Abbe number, the smaller the aberration. These are natural consequences when considering the characteristics of the lens material. is there. Figure 7 shows that the occurrence of aberration can be reduced with respect to temperature changes even if the refractive index is as low as 1.5. Figure 9 shows that the convergence is smaller when the lens interval is longer than 0.2 mm.
[0019] 上記の解析結果をもとに、周辺光の方向余弦に対する収差の依存性を計算する。  Based on the above analysis results, the dependence of aberration on the direction cosine of ambient light is calculated.
条件を表 3に示す。  Table 3 shows the conditions.
[表 3] [Table 3]
Figure imgf000010_0001
Figure imgf000010_0001
記号 因子名 使用値 Symbol Factor name Value used
A 有効半径（nun) 0. 25  A Effective radius (nun) 0.25
屈折率温度変化係  Refractive index temperature change
C - 1 00  C-1 00
数 (X1 0— 6 。 C) Number (X1 0- 6. C)
D 屈折率 1 . 5  D Refractive index 1.5
E アッベ数 ( 5〇5E Abbe number ( 505
M C  M C
F レンズ間隔（mm) ο  F Lens spacing (mm) ο
対物レンズ肉厚  Objective lens thickness
G 0. 32  G 0. 32
(mm)  (mm)
[0020] 条件は SN比が大きくなるところを選んだ。一般に温度が上昇すると、半導体レーザ チップ力もの出射光の波長は長くなる。したがって、温度が上昇したとき注目すべき 収差は波長 655nmにおけるものであり、この波長における物体高が 0. Ommと 0. 0 lmmでの収差が最大になる方が実際上重要となる。図 11に、横軸を方向余弦とした 655nmにおける最大波面収差を示す。光ピックアップに許される波面収差を 0. 03 え rmsと仮定すると、周辺光の方向余弦は 0. 08力 0. 03で使用可能であるこ とが分かる。 [0020] The conditions were selected where the S / N ratio increased. In general, when the temperature rises, the wavelength of the emitted light becomes as long as the power of the semiconductor laser chip. Therefore, the notable aberration when the temperature rises is at the wavelength of 655 nm, and it is practically important that the object height at this wavelength is maximum at 0.0 Omm and 0.0 lmm. Figure 11 shows the maximum wavefront aberration at 655 nm with the horizontal axis as the direction cosine. Assuming that the wavefront aberration allowed for the optical pickup is 0.03 rms, we can see that the direction cosine of the ambient light can be used with 0.08 force 0.03.
[0021] 次に、レンズ間隔にっレ、て解析する。使用する条件を表 4に示す。  [0021] Next, the lens interval is analyzed. Table 4 shows the conditions used.
[表 4] [Table 4]
記号 因子名 使用値 Symbol Factor name Value used
A 有効半怪 (mm) 0. 25 A Effective half-heart (mm) 0. 25
B 方向余弦 -0. 06 B direction cosine -0. 06
屈折率温度変化係  Refractive index temperature change
C - 1 00  C-1 00
数 (X1 0— 6 。 C) Number (X1 0- 6. C)
D 屈折率 1 . 5  D Refractive index 1.5
E アッベ数 55 E Abbe number 55
対物レンズ肉厚  Objective lens thickness
G 、mmノ 0. 32  G, mm no 0.32
[0022] レンズ間隔は狭 、方が光ピックアップを薄くできるので好まし V、が、収差を考慮する 必要がある。評価のための波面収差は、温度が 60°C、波長 655nmで計算されたも ので、物体高が 0. Ommと 0. 01 mmのうち大きい方を選んだ。図 12に解析結果を示 す。 0. 2mm付近のレンズ間隔において波面収差が 0. 03 rmsより小さくなるので 、この近傍で使用可能であることが分かる。 [0022] Narrower lens spacing is preferable because the optical pickup can be made thinner. However, it is necessary to consider aberrations. The wavefront aberration for evaluation was calculated at a temperature of 60 ° C and a wavelength of 655 nm, so the larger object height of 0.0 mm or 0.01 mm was selected. Figure 12 shows the analysis results. Since the wavefront aberration is smaller than 0.03 rms at the lens interval of about 0.2 mm, it can be seen that the lens can be used in this vicinity.
[0023] 次に、対物レンズの中心肉厚について解析する。使用する条件を表 5に示す。  Next, the center thickness of the objective lens is analyzed. Table 5 shows the conditions used.
[表 5] [Table 5]
Figure imgf000012_0001
Figure imgf000012_0001
言己 因子名 使用値 Kotomi Factor name Value used
A 有効半径 (mm) 0. 25  A Effective radius (mm) 0.25
B 方向余弦 B direction cosine
屈折率温度変化係  Refractive index temperature change
C  C
数 (X1 0—6 。 C) 一 1 00 Number (X1 0- 6. C) one 1 00
D 屈折率 1 . 〇 5 D Refractive index 1.
E アッベ数 55 〇 E Abbe number 55 〇
F レンズ間隔（mm) 0. 20 F Lens spacing (mm) 0.20
[0024] レンズの中心肉厚は薄い方が光ピックアップを薄くすることができる。しかし、レンズ のコバ厚が薄くなり過ぎな 、ようにする必要がある。図 13は波面収差のレンズ肉厚依 存性を示すものであり、波面収差はレンズ間隔の場合と同様の定義を使用した。肉 厚 0. 32mm力 0. 36mmの範囲で使用可能であることが分かる。 [0024] The thinner the center thickness of the lens, the thinner the optical pickup. However, it is necessary to make sure that the lens edge is not too thin. Figure 13 shows the dependency of wavefront aberration on lens thickness. The same definition of wavefront aberration as in the case of lens spacing was used. It can be seen that the wall thickness can be used in the range of 0.32mm force and 0.36mm.
[0025] 同様な解析をカップリングレンズの有効半径について行う。解析条件を表 6に示す  A similar analysis is performed for the effective radius of the coupling lens. The analysis conditions are shown in Table 6.
[表 6] [Table 6]
p己" 因子名 使用値 p self "Factor name Value used
B 方向余弦 -0. 06  B direction cosine -0. 06
C 屈折率温度変化係 - 1 00 C Refractive index temperature change-1 00
数 (X1 0— 6 。 C) Number (X1 0- 6. C)
D 屈折率 1 . 5  D Refractive index 1.5
E アッベ数 55 E Abbe number 55
F レンズ『曰 Pil(nim) 0. 20 F lens `` 曰 Pil (nim) 0.20
対物レンズ肉厚  Objective lens thickness
G 0. 32  G 0. 32
(mm;  (mm;
[0026] 図 14に波面収差の有効半径依存性を示す。使用可能な範囲は、波面収差が 0. 0 3 rms以下とすれば、有効半径 0. 24mm力ら 0. 25mmの範囲となる。 FIG. 14 shows the effective radius dependence of the wavefront aberration. If the wavefront aberration is 0.03 rms or less, the usable range is from the effective radius of 0.24 mm to 0.25 mm.
[0027] 以上の解析をもとに設計されたレンズの面データの一例を表 7に示す。  [0027] Table 7 shows an example of lens surface data designed based on the above analysis.
[表 7]
Figure imgf000013_0001
[Table 7]
Figure imgf000013_0001
Figure imgf000013_0002
Figure imgf000013_0002
単位： mm [0028] OBJは物体面、 IMGは像面を表す。 # 1は図 3のカップリングレンズ 101の光源側の 面を表し、 STOは絞り面であること示しており、もし絞り面でなければ # 2と表示される ものである。 STOは、図 3ではカップリングレンズ 101の光ディスク側の面を表す。 # 3 は対物レンズ 102の光源側の面を表し、 # 4は対物レンズ 102の光ディスク側の面を 表す。 # 5は光ディスクのカバー層 301の光源側の面、 # 6はカバー層の裏面を表し ている。 TYPEの列は面のタイプを表し、 Sは球面、 Aは非球面を意味する。 RADIUS は曲率半径を表し、曲率半径の負の符号は中心が光源側にあることを表している。ま た、 Infinityは半径が無限大であることを表している。ここでの RADIUSは、数式 1の c ( 曲率）の逆数となっている。 DISTANCEは面間隔である。 GLASSの列は該当する面か ら次の面までの材質を表し、 500000. 550は 20°Cにおける比屈折率 1. 5、アッベ 数 55. 0を表し、 POLYCARBはポリカーボネート、 AIRは空気を表す。 INDEXの列は 2 0°Cでの絶対屈折率、 APY-Yの列はアパーチャ半径を表し、 APの列の Cは円形開口 であることを示している。表 8には非球面係数を表す。 Unit: mm [0028] OBJ represents an object plane, and IMG represents an image plane. # 1 represents the surface of the coupling lens 101 in FIG. 3 on the light source side, and STO indicates that it is a diaphragm surface. If it is not a diaphragm surface, # 2 is displayed. In FIG. 3, STO represents the surface of the coupling lens 101 on the optical disc side. # 3 represents the surface of the objective lens 102 on the light source side, and # 4 represents the surface of the objective lens 102 on the optical disc side. # 5 represents the light source side surface of the optical disc cover layer 301, and # 6 represents the back surface of the cover layer. The TYPE column indicates the surface type, S means spherical, and A means aspherical. RADIUS indicates the radius of curvature, and the negative sign of the radius of curvature indicates that the center is on the light source side. Infinity indicates that the radius is infinite. RADIUS here is the reciprocal of c (curvature) in Equation 1. DISTANCE is the surface interval. The GLASS column represents the material from the corresponding surface to the next surface, 500000.550 represents a relative refractive index of 1.5 at 20 ° C, an Abbe number of 55.0, POLYCARB represents polycarbonate, and AIR represents air. . The INDEX column indicates the absolute refractive index at 20 ° C, the APY-Y column indicates the aperture radius, and the AP column C indicates a circular aperture. Table 8 shows the aspheric coefficients.
[表 8]
Figure imgf000014_0001
[Table 8]
Figure imgf000014_0001
Figure imgf000014_0002
Figure imgf000014_0002
[0029] # 1から #4は表 7と同じ面を表しており、すべての面は ODDで表される奇数次非 球面となっている。 K及び A, B, Cは、奇数次非球面を表すための係数であり、式 (1) で使用された係数と同じである。この面形状を使用すると、環境温度 60°C、波長 655 nm、物体高 0. 01mmの条件で、波面収差は 0. 02694え rmsを得ることができる。  [0029] # 1 to # 4 represent the same surface as Table 7, and all the surfaces are odd-order aspheric surfaces represented by ODD. K and A, B, and C are coefficients for representing an odd-order aspheric surface, and are the same as those used in Equation (1). When this surface shape is used, the wavefront aberration of 0.06944 rms can be obtained under the conditions of an environmental temperature of 60 ° C, a wavelength of 655 nm, and an object height of 0.01 mm.
[0030] 以上の解析は、プラスチックの屈折率温度変ィ匕係数が 100 X 10— 6Z°Cの下に行 つたものであり、この係数をさらにゼロに近い値 (例えば—80 X 10— 6Z°C)に設定する と、使用可能な範囲すなわち波面収差が 0. 03 rmsより小さい範囲は広がる。した がって、上記の解析した範囲に、本発明の範囲が限定されるものではない。 [0030] The above analysis is intended refractive index temperature Heni匕係number of plastic is one line below the 100 X 10- 6 Z ° C, closer to zero the value of this factor (e.g., -80 X 10- 6 Z ° C) Then, the usable range, that is, the range where the wavefront aberration is smaller than 0.03 rms widens. Therefore, the scope of the present invention is not limited to the analyzed range.
発明の効果  The invention's effect
[0031] 光ピックアップのカップリングレンズと対物レンズにプラスチック材料を使用したとき、 レンズの屈折率が温度で大きく変わる問題が生ずる。本発明では、光ピックアップで 使用する 2枚のレンズの 4面すべてを奇数次非球面とすることで、プラスチックレンズ に温度上昇があっても、波面収差を小さくすることができる。これにより情報記録媒体 上に良好な光スポットを形成することができ、読出しエラーを少なくすることができる。  [0031] When a plastic material is used for the coupling lens and the objective lens of the optical pickup, there arises a problem that the refractive index of the lens varies greatly with temperature. In the present invention, the wavefront aberration can be reduced even when the temperature of the plastic lens rises by making all four surfaces of the two lenses used in the optical pickup an odd-order aspheric surface. As a result, a good light spot can be formed on the information recording medium, and read errors can be reduced.
[0032] また、光ピックアップのレンズにプラスチックを使用したことで、移動制御するべきレ ンズの重量を軽くすることができ、これにより発生する熱を小さくすることが可能になる 。本発明の光ピックアップは、スイングアームを使用する。スイングアームは光ピックァ ップの光学系全体を移動制御するので、重量が重 、とスイングアームを回転させたり 、曲げたりするためのァクチユエータに流す電流が大きくなり、発熱量が大きくなる。 その結果、光ピックアップ内部の温度が上昇し、プラスチックレンズの屈折率を大きく 変化させる原因になる。本発明によれば、スイングアームにかかる負荷を小さくできる ので、消費電力を小さくすることができ、光ピックアップの温度上昇を抑えることができ る。  [0032] Further, the use of plastic for the lens of the optical pickup makes it possible to reduce the weight of the lens to be moved and thereby reduce the heat generated. The optical pickup of the present invention uses a swing arm. Since the swing arm controls the movement of the entire optical system of the optical pickup, the weight is heavy, and the current that flows to the actuator for rotating or bending the swing arm increases, and the amount of heat generation increases. As a result, the temperature inside the optical pickup rises, causing a large change in the refractive index of the plastic lens. According to the present invention, since the load applied to the swing arm can be reduced, the power consumption can be reduced and the temperature rise of the optical pickup can be suppressed.
[0033] さらに、有効径の小さいレンズの採用と、メニスカス型のカップリングレンズの使用に より、小型で軽量の携帯用途に適した光ピックアップの実現が可能になる。  [0033] Furthermore, the use of a lens having a small effective diameter and the use of a meniscus coupling lens make it possible to realize an optical pickup that is small and lightweight and suitable for portable use.
図面の簡単な説明  Brief Description of Drawings
[0034] [図 1]本発明による光ピックアップの実施例を示す断面概略図。 FIG. 1 is a schematic sectional view showing an embodiment of an optical pickup according to the present invention.
[図 2]光ピックアップの概略図。  FIG. 2 is a schematic diagram of an optical pickup.
[図 3]レンズ系を示す図。  FIG. 3 is a diagram showing a lens system.
[図 4]有効半径の主効果を示す図。  [Fig. 4] Diagram showing main effect of effective radius.
[図 5]方向余弦の主効果を示す図。  FIG. 5 is a diagram showing the main effect of direction cosine.
[図 6]屈折率温度変化係数の主効果を示す図。  FIG. 6 is a diagram showing the main effect of the refractive index temperature change coefficient.
[図 7]屈折率の主効果を示す図。  FIG. 7 is a diagram showing the main effect of refractive index.
[図 8]アッベ数の主効果を示す図。 [図 9]レンズ間隔の主効果を示す図。 [Fig. 8] Diagram showing the main effect of Abbe number. FIG. 9 is a diagram showing the main effect of lens spacing.
[図 10]対物レンズ中心肉厚の主効果を示す図。  FIG. 10 is a diagram showing the main effect of the center thickness of the objective lens.
[図 11]波面収差の最周辺光の方向余弦に対する依存性を示す図。  FIG. 11 is a graph showing the dependence of wavefront aberration on the direction cosine of the most peripheral light.
[図 12]波面収差のレンズ間隔依存性を示す図。  FIG. 12 is a graph showing the lens interval dependence of wavefront aberration.
[図 13]波面収差の対物レンズの中心肉厚に対する依存性を示す図。  FIG. 13 is a graph showing the dependence of wavefront aberration on the center thickness of an objective lens.
[図 14]波面収差のカップリングレンズの有効半径に対する依存性を示す図。  FIG. 14 is a graph showing the dependence of wavefront aberration on the effective radius of a coupling lens.
[図 15]実施例で使用したレンズ系の波面収差の温度依存性を示す図。  FIG. 15 is a diagram showing the temperature dependence of the wavefront aberration of the lens system used in the example.
[図 16]実施例に使用される光検出器パターンを示す図。  FIG. 16 is a diagram showing a photodetector pattern used in the example.
[図 17]本発明の光ピックアップを搭載した光ディスク装置の概略を示す図。  FIG. 17 is a diagram showing an outline of an optical disc apparatus equipped with the optical pickup of the present invention.
符号の説明  Explanation of symbols
[0035] 10 半導体レーザチップ [0035] 10 Semiconductor laser chip
103 カップリングレンズ  103 coupling lens
104 対物レンズ  104 Objective lens
111 プリズム  111 prism
211 シリコン基板  211 Silicon substrate
221, 222, 223 光検出器  221, 222, 223 photodetector
201 ァクチユエータアーム  201 Actuator Arm
300 情報記録媒体 (光ディスク）  300 Information recording medium (optical disc)
301 カバー層  301 cover layer
発明を実施するための最良の形態  BEST MODE FOR CARRYING OUT THE INVENTION
[0036] 以下、本発明の形態の形態を、図を用いて説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0037] 図 17は、光ディスク装置の概略図である。図 17 (a)は平面図、図 17 (b)は側面図 である。光ディスク 300はスピンドルモータ 402の回転軸に固定され、回転駆動され る。光ピックアップ 401はァクチユエータアーム 201に取りつけられており、ァクチユエ ータアーム 201はフォーカスァクチユエータ 407で光ピックアップの対物レンズの光 軸方向に微動できるようになつている。さらにァクチユエータアーム 201とフォーカス ァクチユエータ 407は、カウンターバランス 405と共にスイングアーム 403に固定され ており、スイングアーム 403はスイングモータ 404により光ピックアップ 401を光デイス ク 300の半径方向に駆動する。光ピックアップへの信号入出力は図示しないフレキシ ブルプラスチックケーブルにより制御回路 406へ結線されている。 FIG. 17 is a schematic diagram of an optical disc apparatus. Fig. 17 (a) is a plan view and Fig. 17 (b) is a side view. The optical disc 300 is fixed to the rotating shaft of the spindle motor 402 and is driven to rotate. The optical pickup 401 is attached to the actuator arm 201, and the actuator arm 201 can be finely moved by the focus actuator 407 in the optical axis direction of the objective lens of the optical pickup. Further, the actuator arm 201 and the focus actuator 407 are fixed to the swing arm 403 together with the counter balance 405, and the swing arm 403 uses the swing motor 404 to connect the optical pickup 401 to the optical device. Drive in the radial direction of the K300. Signal input / output to the optical pickup is connected to the control circuit 406 by a flexible plastic cable (not shown).
[0038] 図 1は、本発明による光ピックアップの実施例を示すものであり、光ピックアップの光 軸を通る断面の概略図である。図 1に示した光学系は、図 2に示した概略の光学構 成と同じであるが、図 1にはプラスチックレンズの設計結果に基づく光学系が示してあ り、同時に光線経路を示し、光ビームの大きさが分力るようにした。 10は波長 650nm の半導体レーザチップであり、屈折率 1. 725829のガラスプリズム 111により反射さ れる。カップリングレンズ 103及び対物レンズ 104は ZEONEX330R (日本ゼオン株式 会社製）という光学用のプラスチックを使用している。プラスチックレンズは射出成型 により作られ、光を屈折するレンズ部分と同時に、プリズム 111の上部に設置するた めの平坦な支持部も成型される。カップリングレンズ 103はメニスカス型であり、レー ザ光源側の NA(0. 1)と有効半径が固定されている場合、レーザ光源とカップリング レンズ 103との間の作動距離を短くするのに有効となる。カップリングレンズ 103と対 物レンズ 104の間の最周辺光の方向余弦は 0. 06になるように設計した。カツプリ ングレンズ 103はプリズム 111の上に接着され、さらに対物レンズ 104がカップリング レンズ 103の上に接着される。対物レンズ 104の NAは 0. 85であり、レーザ光は光 ディスクの 0. 1mmのカバー層を通して情報記録層に集光される。  FIG. 1 shows an embodiment of an optical pickup according to the present invention, and is a schematic view of a cross section passing through the optical axis of the optical pickup. The optical system shown in Fig. 1 is the same as the schematic optical configuration shown in Fig. 2, but Fig. 1 shows an optical system based on the design result of the plastic lens. The size of the light beam was divided. Reference numeral 10 denotes a semiconductor laser chip having a wavelength of 650 nm, which is reflected by the glass prism 111 having a refractive index of 1. 725829. The coupling lens 103 and the objective lens 104 use an optical plastic called ZEONEX330R (manufactured by Nippon Zeon Co., Ltd.). The plastic lens is made by injection molding, and at the same time as the lens part that refracts light, a flat support part for installation on the upper part of the prism 111 is also molded. The coupling lens 103 is a meniscus type, and is effective in shortening the working distance between the laser light source and the coupling lens 103 when the NA (0.1) on the laser light source side and the effective radius are fixed. It becomes. The direction cosine of the most ambient light between the coupling lens 103 and the object lens 104 is designed to be 0.06. The coupling lens 103 is bonded onto the prism 111, and the objective lens 104 is bonded onto the coupling lens 103. The NA of the objective lens 104 is 0.85, and the laser light is focused on the information recording layer through the 0.1 mm cover layer of the optical disk.
[0039] 情報記録層からの反射光は対物レンズ 104及びカップリングレンズ 103を戻った後 、プリズム 111の内部に進入し、複数回内部で反射される。プリズムの上部はアルミ- ゥムの薄膜が蒸着され、反射率を大きくしている。 221と 222, 223は光検出器であり 、光ディスクが合焦点位置にあるとき光検出器 222のところで光スポットが小さくなるよ うに、プリズム 111の高さと位置、反射光の進入位置を適切に設定してある。  The reflected light from the information recording layer returns to the objective lens 104 and the coupling lens 103 and then enters the prism 111 and is reflected therein a plurality of times. An aluminum thin film is deposited on the top of the prism to increase the reflectivity. 221, 222, and 223 are photodetectors, and the height and position of the prism 111 and the entrance position of the reflected light are appropriately set so that the light spot becomes small at the photodetector 222 when the optical disk is at the in-focus position. It is.
[0040] 光検出器 221と 223はフォーカスエラー信号とトラッキングエラー信号を生成するた めのものであり、光検出器 222からの信号は記録情報を読み出すための RF信号とな る。これらの光検出器はシリコン基板 211上に形成されたものであり、スイングアーム 201に接着されて 、る。スイングアームはァクチユエータにより紙面に垂直方向と紙 面内上下方向に移動 ·屈曲することができ、光検出器 221と 223からのフィードバック 信号により、光ディスク 301の情報記録層上で適切なトラック位置、焦点位置が保た れる。 The photodetectors 221 and 223 are for generating a focus error signal and a tracking error signal, and the signal from the photodetector 222 is an RF signal for reading out recorded information. These photodetectors are formed on the silicon substrate 211, and are bonded to the swing arm 201. The swing arm can be moved and bent in the direction perpendicular to the paper surface and the vertical direction in the paper surface by the actuator, and the appropriate track position and focus on the information recording layer of the optical disc 301 can be determined by feedback signals from the optical detectors 221 and 223. Position kept It is.
図 1に示したプラスチックレンズの面データの一例を表 9,表 10に示す,  Examples of surface data for the plastic lens shown in Fig. 1 are shown in Tables 9 and 10.
[表 9]
Figure imgf000018_0001
[Table 9]
Figure imgf000018_0001
Figure imgf000018_0002
Figure imgf000018_0002
単位： mm Unit: mm
10] 表 1 0 10] Table 1 0
Figure imgf000018_0003
表の見方は表 7、表 8と同じである。図 1のプリズムの高さは 0. 65mmであり、レー ザ光源とプリズムまでの距離は 1. 1mm、光軸の高さはシリコン基板表面力 0. 45m mの所に設定した。表 9に示した面間隔を勘案すると、プリズムの底面力 対物レン ズの出射面までの高さは約 1. 7mmとなる。シリコン基板とスイングアームの厚さを、 それぞれ 0. 5mm, 1. Ommとすると、全体の厚さは約 3. 2mmとなる。レーザ光源か らプリズム 111の右端までの距離は約 3mmであり、紙面に垂直方向のプリズム 111 の幅は約 0. 8mm程度とすることができる。このように光ピックアップの光学系を小さく でき、またレンズの支持部分にもプラスチックを使用するので、軽量ィ匕できる。
Figure imgf000018_0003
The way of reading the table is the same as Table 7 and Table 8. The height of the prism in Fig. 1 was 0.65 mm, the distance between the laser light source and the prism was 1.1 mm, and the height of the optical axis was set at a silicon substrate surface force of 0.45 mm. Considering the surface spacing shown in Table 9, the height of the prism bottom force objective lens to the exit surface is about 1.7 mm. If the thickness of the silicon substrate and swing arm is 0.5 mm and 1. Omm, respectively, the total thickness is about 3.2 mm. Laser light source The distance to the right end of the prism 111 is about 3 mm, and the width of the prism 111 in the direction perpendicular to the paper surface can be about 0.8 mm. In this way, the optical system of the optical pickup can be made small, and since plastic is used for the lens support portion, the weight can be reduced.
[0043] レンズの面データを表 9,表 10に示したレンズ系のプラスチックレンズの波面収差 の温度依存性を図 15に示す。 650nmと 655nmの 2波長と、零と 0. Olmmの二つの 物体高の組み合わせについて、 20, 40, 60°Cの波面収差を示した。温度が上昇し ても、波長 655nmで軸外すなわち物体高 0. Olmmにおいても 0. 03 rms以下に 波面収差が抑えられて 、る。 60°Cでの波面収差力 0°Cの場合より小さくなる現象が 見られる力 これは使用したプラスチック材料 ZEONEX330Rの屈折率温度変ィ匕係数 が温度上昇とともに負から正の値に変化する性質を有するためである。  [0043] The temperature dependence of the wavefront aberration of the plastic lens of the lens system whose lens surface data is shown in Tables 9 and 10 is shown in FIG. Wavefront aberrations of 20, 40, and 60 ° C were shown for two object heights of 650nm and 655nm and two object heights of zero and 0. Olmm. Even when the temperature rises, the wavefront aberration is suppressed to 0.03 rms or less even at an off-axis wavelength of 655 nm, that is, at an object height of 0.05 mm. Wavefront aberration force at 60 ° C Force that is smaller than that at 0 ° C This is the property that the refractive index temperature change coefficient of the plastic material used ZEONEX330R changes from negative to positive value as the temperature rises. It is for having.
[0044] 実施例の光検出器 221, 222, 223の形状とフォーカスエラー信号 (FES)、トラッ キングエラー信号 (TES)、RF信号 (RFS)と光検出器力もの出力の関係を図 16に 示す。光検出器の形状は、対物レンズの光軸方向すなわち光ディスク側力 シリコン 基板を見たときのものであり、左方向にレーザ光源がある。フォーカスエラー信号は、 3分割された光検出器 221 (M, N, O)と 6分割した光検出器 223 (P, Q, R, S, T, U)から生成する。 kはプリズム内で反射する毎に光量が減少して、光検出器に入射 する全光量が減少するのを補償するためのものである。情報記録媒体が合焦点位置 にある場合の光検出器上のスポット形状と比較して、情報記録媒体が対物レンズから 微小な距離遠ざかると、 221の検出器に落ちる光スポットが小さくなり、かつ 223の光 検出器に落ちる光スポット形状は大きくなる。逆に、情報記録媒体が対物レンズに近 づくと、 221の検出器に落ちる光スポットが大きくなり、かつ 223の光検出器に落ちる 光スポット形状は大きくなる。この形状変化を FESの信号として検出し、スイング了一 ムのァクチユエータを制御する。トラッキングエラー信号は光検出器 223から形成され る。光情報記録媒体のトラックの方向と光検出器 223の 2分割線の方向がほぼ一致 するように光ピックアップが設置されており、トラッキングがずれると検出器 223の S、 T 、 Uの組の総光量と PQRの組の総光量にアンバランスが生じる。これがトラッキングェ ラー信号となる。  [0044] Figure 16 shows the relationship between the shape of the photodetectors 221, 222, and 223 of the example, the focus error signal (FES), the tracking error signal (TES), the RF signal (RFS), and the output of the photodetector. Show. The shape of the photodetector is that of the objective lens when viewed from the optical axis direction of the objective lens, that is, the optical disk side force silicon substrate, and there is a laser light source in the left direction. The focus error signal is generated from the three-divided photodetector 221 (M, N, O) and the six-divided photodetector 223 (P, Q, R, S, T, U). k is used to compensate for a decrease in the total amount of light incident on the photodetector due to a decrease in the amount of light each time it is reflected in the prism. Compared with the spot shape on the photodetector when the information recording medium is at the in-focus position, the light spot falling on the detector 221 becomes smaller when the information recording medium is moved a minute distance from the objective lens, and 223 The shape of the light spot falling on the light detector becomes larger. Conversely, when the information recording medium approaches the objective lens, the light spot falling on the detector 221 increases and the shape of the light spot falling on the detector 223 increases. This shape change is detected as an FES signal, and the swing end actuator is controlled. The tracking error signal is formed from the photodetector 223. An optical pickup is installed so that the direction of the track of the optical information recording medium and the direction of the two-divided line of the photodetector 223 are substantially coincident. If tracking is shifted, the total of the S, T, and U pairs of the detector 223 There is an imbalance between the light intensity and the total light intensity of the PQR pair. This is the tracking error signal.
[0045] 本発明により、光ピックアップが小型軽量化され、光ディスク装置の利便性を向上 することができる。小径の光ディスクを使用することで、光ピックアップを含む光デイス クドライブを小型化できる。これを、携帯電話等の情報携帯端末に搭載することで、 容易に大量のデータを取り込むことができるようになる。また、軽いプラスチックレンズ を使用することで、光ピックアップ内のスイングアームを高速で移動させることが可能 になるので、データアクセス時間を短縮することが可能になる。さらに、プラスチックレ ンズはガラスモールドレンズより製作が容易であるため、光ピックアップを安価に製造 可能となる。 [0045] According to the present invention, the optical pickup is reduced in size and weight, and the convenience of the optical disc apparatus is improved. can do. By using a small-diameter optical disk, the optical disk drive including the optical pickup can be downsized. By installing this in portable information terminals such as mobile phones, a large amount of data can be easily captured. In addition, by using a light plastic lens, it is possible to move the swing arm in the optical pickup at a high speed, thereby shortening the data access time. Furthermore, since the plastic lens is easier to manufacture than the glass mold lens, the optical pickup can be manufactured at low cost.

Claims

請求の範囲 The scope of the claims
[1] 光ディスクを固定して回転駆動するディスク駆動部と、前記ディスク駆動部に固定さ れた光ディスクに対してレーザ光を照射し反射光を検出する光ピックアップと、前記 光ピックアップを前記ディスク駆動部に固定された光ディスクの半径方向に駆動する 光ピックアップ駆動部とを備える光ディスク装置において、  [1] A disk drive unit that fixes and rotates an optical disk, an optical pickup that irradiates a laser beam to the optical disk fixed to the disk drive unit to detect reflected light, and drives the optical pickup to the disk In an optical disc apparatus comprising an optical pickup driving unit that drives in a radial direction of an optical disc fixed to the unit,
前記光ピックアップは、半導体レーザチップと、前記ディスク駆動部に固定された光 ディスクに前記半導体レーザチップからの出射光を集光する集光光学系と、反射光 を検出する検出光学系とを有し、前記集光光学系はプラスチックカツプリングレンズと プラスチック対物レンズとによって構成され、前記カップリングレンズ及び前記対物レ ンズのそれぞれの面は奇数次非球面であることを特徴とする光ディスク装置。  The optical pickup includes a semiconductor laser chip, a condensing optical system that condenses the light emitted from the semiconductor laser chip on an optical disk fixed to the disk drive unit, and a detection optical system that detects reflected light. The condensing optical system is constituted by a plastic coupling lens and a plastic objective lens, and each surface of the coupling lens and the objective lens is an odd-order aspheric surface.
[2] 請求項 1記載の光ディスク装置において、前記半導体レーザリップからの出射光を 受ける前記プラスチックカップリングレンズから前記プラスチック対物レンズに向力ぅレ 一ザ光のビーム径は光軸を進むにしたがって小さくなることを特徴とする光ディスク装 置。  [2] In the optical disc device according to claim 1, the beam diameter of the laser beam directed from the plastic coupling lens that receives the light emitted from the semiconductor laser lip to the plastic objective lens as it travels along the optical axis. An optical disc device characterized by being smaller.
[3] 請求項 1記載の光ディスク装置において、前記集光光学系の光軸と前記半導体レ 一ザチップからの出射光を含む面内で前記光軸に垂直な直線を考えるとき、当該直 線に対して前記プラスチックカップリングレンズから前記プラスチック対物レンズに向 力うレーザ光の周辺光の方向余弦は 0. 08〜一 0. 03であることを特徴とする光デ イスク装置。  [3] In the optical disc apparatus according to claim 1, when considering a straight line perpendicular to the optical axis in a plane including the optical axis of the condensing optical system and the light emitted from the semiconductor laser chip, the straight line On the other hand, the optical disk device is characterized in that the direction cosine of the ambient light of the laser light directed from the plastic coupling lens to the plastic objective lens is 0.08 to 0.03.
[4] 請求項 1記載の光ディスク装置において、前記プラスチックカップリングレンズはメ ニスカスであることを特徴とする光ディスク装置。  4. The optical disk apparatus according to claim 1, wherein the plastic coupling lens is a meniscus.
[5] 請求項 1記載の光ディスク装置において、前記プラスチック対物レンズの NAは略 05. The optical disc apparatus according to claim 1, wherein NA of the plastic objective lens is substantially 0.
. 85であることを特徴とする光ディスク装置。 An optical disc device characterized by being 85.
[6] 請求項 1記載の光ディスク装置にお!、て、前記半導体レーザチップ、前記プラスチ ックカップリングレンズ及び前記プラスチック対物レンズは相対位置が固定され、前記 光ピックアップ駆動部は、前記半導体レーザチップ、前記プラスチックカップリングレ ンズ及び前記プラスチック対物レンズを一体として駆動することを特徴とする光デイス ク装置。 請求項 1記載の光ディスク装置において、前記集光光学系の有効半径は 0. 25m m以下であることを特徴とする光ディスク装置。 [6] In the optical disc apparatus according to claim 1, the semiconductor laser chip, the plastic coupling lens, and the plastic objective lens are fixed in relative positions, and the optical pickup driving unit includes the semiconductor laser. An optical disk device, wherein a chip, the plastic coupling lens, and the plastic objective lens are integrally driven. 2. The optical disk apparatus according to claim 1, wherein an effective radius of the condensing optical system is 0.25 mm or less.
PCT/JP2006/304380 2005-11-16 2006-03-07 Optical disc device WO2007057988A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009037738A (en) * 2007-07-31 2009-02-19 Hitachi High-Technologies Corp Electron microscope equipped with electronic spectrometer

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Publication number Priority date Publication date Assignee Title
JPH07161064A (en) * 1993-12-09 1995-06-23 Sharp Corp Optical pickup
JPH085909A (en) * 1994-06-20 1996-01-12 Konica Corp Light convergence optical system for recording and reproduction of optical information medium
JPH1055562A (en) * 1996-04-03 1998-02-24 Konica Corp Recording and/or reproducing optical system for optical information recording medium

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07161064A (en) * 1993-12-09 1995-06-23 Sharp Corp Optical pickup
JPH085909A (en) * 1994-06-20 1996-01-12 Konica Corp Light convergence optical system for recording and reproduction of optical information medium
JPH1055562A (en) * 1996-04-03 1998-02-24 Konica Corp Recording and/or reproducing optical system for optical information recording medium

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009037738A (en) * 2007-07-31 2009-02-19 Hitachi High-Technologies Corp Electron microscope equipped with electronic spectrometer

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