WO2005048249A1 - Capteur optique et le lecteur de disques optiques - Google Patents

Capteur optique et le lecteur de disques optiques Download PDF

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Publication number
WO2005048249A1
WO2005048249A1 PCT/JP2004/010662 JP2004010662W WO2005048249A1 WO 2005048249 A1 WO2005048249 A1 WO 2005048249A1 JP 2004010662 W JP2004010662 W JP 2004010662W WO 2005048249 A1 WO2005048249 A1 WO 2005048249A1
Authority
WO
WIPO (PCT)
Prior art keywords
optical
recording
pickup device
optical pickup
semiconductor laser
Prior art date
Application number
PCT/JP2004/010662
Other languages
English (en)
Japanese (ja)
Inventor
Issei Abe
Original Assignee
Ricoh Company, 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 Ricoh Company, Ltd. filed Critical Ricoh Company, Ltd.
Publication of WO2005048249A1 publication Critical patent/WO2005048249A1/fr

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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
    • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
    • G11B7/127—Lasers; Multiple laser arrays
    • 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
    • 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
    • G11B2007/0009—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage
    • G11B2007/0013—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage for carriers having multiple discrete layers

Definitions

  • the present invention relates to an optical pickup device and an optical disk device.
  • Patent Document 1 JP-A-10-20263
  • the recording density of the optical disc has been increased by increasing the linear recording density in the information recording layer of the optical disc and by narrowing the track pitch.
  • Methods for reducing the beam diameter of the light beam include increasing the numerical aperture NA (Numerical Aperture) of the light beam emitted from an objective lens as a condensing optical system of an optical pickup device for recording and reproducing an optical disk, It is possible to shorten the wavelength of the light beam. For example, shortening the wavelength of a light beam is considered to be feasible by changing the light source to a red semiconductor laser, a blue-violet semiconductor laser that has begun to be fully commercialized.
  • the information recording layer is covered with a cover glass in order to protect the information recording layer from dust and scratches. Therefore, the light beam transmitted through the objective lens of the optical pickup device passes through the cover glass, and is condensed and focused on the information recording layer thereunder.
  • spherical aberration SA Spherical Aberration
  • the spherical aberration SA is represented by the following equation (1).
  • the spherical aberration SA is proportional to the fourth power of the cover glass thickness d and the numerical aperture NA of the objective lens.
  • the objective lens is designed to cancel the spherical aberration, so that the spherical aberration of the light beam passing through the objective lens and the cover glass is sufficiently small.
  • the spherical aberration error ASA caused by the cover glass thickness error Ad is proportional to the cover glass thickness error ⁇ (!. That is, the cover glass thickness error Ad can be increased. The greater the error, the greater the spherical aberration error ASA, which makes it impossible to read and write information correctly.
  • a conventional optical disc for example, like a DVD (Digital Versatile Disc)
  • NA of an objective lens in an optical pickup device used is as small as about 0.6. Therefore, the spherical aberration error ASA caused by the cover glass thickness error Ad was small, and the light beam could be focused sufficiently small for each information recording layer.
  • a multi-layer optical disc formed by laminating information recording layers for example, a DVD with two information recording layers has already been commercialized so that the density of recorded information can be increased in the thickness direction of the optical disc.
  • the thickness from the surface of the optical disc (cover glass surface) to each information recording layer differs for each of the laminated information recording layers.
  • the spherical aberration generated when the light beam passes through the cover glass of the optical disc differs for each information recording layer.
  • the difference (error ASA) of the spherical aberration occurring in the information recording layer in contact with the P is in proportion to the interlayer distance t (corresponding to the thickness d) of the information recording layer in contact with the above equation (1).
  • An object of the present invention is to reduce the cost and the size of a device using a wavefront aberration correction element such as a liquid crystal element so that the recording or reproducing operation on an optical recording medium having a plurality of recording surfaces is affected by the wavefront aberration. Is to be able to do without.
  • the present invention relates to an optical pickup device for irradiating an optical recording medium having a plurality of recording surfaces laminated thereon, wherein a laser beam is applied to the optical recording medium.
  • the present invention also provides an optical disk device provided with the above optical pickup device.
  • the present invention it is possible to realize a better recording or reproducing operation at a lower cost and a smaller size than an optical system using a wavefront aberration correcting element such as a liquid crystal element.
  • FIG. 1 is an optical system configuration diagram schematically showing a configuration example of an optical pickup device according to an embodiment of the present invention provided in an optical disk device.
  • FIG. 2 is an explanatory diagram schematically showing an optical system of a semiconductor laser chip separated.
  • FIG. 3 is a perspective view showing a configuration example of a light source unit.
  • FIG. 4 is a diagram showing a configuration example of an optical disc device according to an embodiment of the present invention.
  • FIG. 1 is an optical system configuration diagram schematically showing a configuration example of an optical pickup device provided in an optical disk device according to an embodiment of the present invention.
  • a DVD disc is used as an optical recording medium.
  • the optical pickup device 2 shown in FIG. 1 irradiates the optical recording medium 1 with a wavelength of about 660 nm.
  • An LD package 3 as a light source that emits a laser beam, a diffraction grating 4 for separating the laser beam emitted from the LD package 3 into three beams, for example, a main beam and two sub beams, and incident light.
  • Polarizing beam splitter 5 for separating return light
  • collimator lens 6 for collimating divergent laser light
  • 1Z4 wave plate 7 for converting linearly polarized light to circularly polarized light
  • Objective lens 8 a cylindrical lens 9 for condensing the return light separated by the polarizing beam splitter 5, and receiving the condensed return light to detect RF signal information, servo signals, etc.
  • a light-receiving element 10 having an appropriately divided structure for performing the operation.
  • the laser light emitted from the LD package 3 passes through the polarizing beam splitter 5 and the collimator lens 6 while being separated into three beams by the diffraction grating 4, and becomes a quarter-wavelength parallel light flux.
  • the light enters the plate 7, is converted from linearly polarized light into circularly polarized light, and is condensed and irradiated on the recording surface of the optical recording medium 1 by the objective lens 8.
  • the three spots based on the three beams are separately irradiated at predetermined intervals.
  • the return light reflected from the optical recording medium 1 passes through the objective lens 8 and the quarter-wave plate 7 again, and is converted from circularly polarized light into linearly polarized light having a polarization direction different from that of the incident light by 90 °. Then, the light enters the polarization beam splitter 5. As a result, the return light is separated from the incident light and condensed on the light receiving element 10 by the cylindrical lens 9. RF signal information, servo signals, and the like are detected based on the light receiving signal of the light receiving element 10.
  • the embodiment shown in FIG. 1 is a DVD having a plurality of recording surfaces, for example, a DVD having two recording surfaces, a first recording surface la and a second recording surface lb.
  • Disc 1 is applicable. Therefore, in order to correspond to such a plurality of recording surfaces, the optical pickup device 2 has a semiconductor laser chip 1 la, which serves as two light emitting units dedicated to each of the recording surfaces la and lb with respect to the LD package 3. Consists of 1 lb.
  • the semiconductor laser chip 11a is provided for the recording surface la of the first layer, and the semiconductor laser chip l ib is provided for the recording surface lb of the fourth layer.
  • Each of these semiconductor laser chips 11a and 11b emits laser light having a wavelength of about 660 nm from the light emitting point corresponding to the DVD disk 1.
  • the semiconductor laser chips 11a and 11b are located between the light emitting point positions in the optical axis direction.
  • the positional relationship between the recording surfaces la and lb is adjusted and set so that the distance becomes a predetermined distance according to the distance between the recording surfaces la and lb.
  • the laser light emitted from the semiconductor laser chip 11a is applied to the first-layer recording surface la via an optical system such as the objective lens 8 or the like, the laser light is emitted from the semiconductor laser chip 11a. Is positioned at the position on the optical axis where the optical characteristics (recording / reproducing function) are optimal.
  • the laser beam emitted from the semiconductor laser chip l ib is applied to the second layer recording surface lb via an optical system such as the objective lens 8
  • the laser beam emitted from the semiconductor laser chip l ib is The laser beam is positioned on the optical axis at which the optical characteristics (recording / reproducing function) of the laser beam are optimal (ie, a state in which spherical aberration is extremely small).
  • these semiconductor laser chips 11a and 11b are arranged so as to have a predetermined distance between light emitting point positions in the optical axis direction.
  • FIG. 2 schematically shows the optical system of the semiconductor laser chips 11a and 11b separately.
  • the focal length of the collimator lens 6 is fcl
  • the focal length of the objective lens 8 is fol
  • the distance between the first and second recording surfaces la and lb is d
  • the distance between the first and second recording surfaces la and lb is n
  • the distance L between the light emitting points a and b in the optical axis direction of the two semiconductor laser chips 11a and lib is
  • the positions in the optical axis direction are adjusted and set so as to satisfy the following relationship.
  • the mutual optical axes are adjusted so that the optical characteristics of the laser light radiated to the corresponding recording surfaces la and lb via the common objective lens 8 are optimized.
  • An LD package 3 having two semiconductor laser chips l la and l ib whose position in the direction is adjusted is provided. Therefore, the optical pickup device 2 uses a wavefront aberration correction element such as a liquid crystal element that performs a recording or reproducing operation using the semiconductor laser chips 1 la and 1 lb corresponding to the respective recording surfaces la and lb.
  • a wavefront aberration correction element such as a liquid crystal element that performs a recording or reproducing operation using the semiconductor laser chips 1 la and 1 lb corresponding to the respective recording surfaces la and lb.
  • each of the semiconductor laser chips l la and l ib is adjusted and set so that the optical characteristics with respect to the first and second recording surfaces la and lb of the DVD disk 1 are optimal.
  • the semiconductor laser chip 11a is used and the second layer
  • the use of the semiconductor laser chip l ib during the recording or reproducing operation of the recording surface lb of will not be affected by spherical aberration during the recording or reproducing operation of any of the recording surfaces la and lb.
  • the mutual positional relationship between the semiconductor laser chips l la and l ib is designed and managed so that the mutual positional relationship in the optical axis direction becomes a predetermined value by simultaneous fabrication in the fabrication stage of these chips. It is desirable to keep.
  • a configuration example of the light source unit will be described with reference to FIG.
  • the semiconductor laser chips 11a and 11b are formed adjacently and simultaneously on the same substrate. Then, the positions are set by cutting the semiconductor laser chips 11a and 11b so that the distance in the optical axis direction between the light emitting points a of the laser beams 11a and lib satisfies the above relational expression relating to L.
  • FIG. 3 the semiconductor laser chips 11a and 11b are formed adjacently and simultaneously on the same substrate. Then, the positions are set by cutting the semiconductor laser chips 11a and 11b so that the distance in the optical axis direction between the light emitting points a of the laser beams 11a and lib satisfies the above relational expression relating to L.
  • an optical recording medium having three or more recording surfaces The same can be applied to
  • the optical recording medium is not limited to a DVD disk, but may be a CD disk using a laser beam having a wavelength of about 780 nm, or an optical pickup device capable of recording and reproducing both CDZDVD disks. Les ,.
  • the force applied to an example of an optical system configuration called a Balta type using the light source 3 and the light receiving element 10 separately is a light receiving / emitting element recently used in an optical pickup configuration.
  • a hologram unit that installs a hologram or a polarization hologram in one package and separates and combines light beams by using a hologram unit or an optical system configuration that uses a polarization hologram unit may be used. .
  • FIG. 4 is a diagram illustrating a configuration example of an optical disc device according to an embodiment of the present invention.
  • the optical disk device 20 includes an optical pickup device 2, a spin-driving motor 21, a servo circuit 22, an optical disk controller 23, an access control circuit 24, a signal processing circuit 25, and an Interface 26.
  • the spindle motor 21 drives the optical recording medium 1 to rotate at a predetermined rotation speed under the control of the optical disk controller 23.
  • the servo circuit 22 performs focus servo and tracking servo of the optical pickup device based on a tracking error signal, a focus error signal, and the like under the control of the optical disk controller 23.
  • the access control circuit 24 operates the optical pickup device 2 at high speed in the radial direction of the optical recording medium 1 under the control of the optical disk controller 23, and moves the optical pickup device 2 on the signal recording surface of the optical recording medium 1. At a predetermined recording track.
  • the access control circuit 24 also controls the emission power of the laser light emitted from the optical pickup device 2 under the control of the optical disk controller 23.
  • the signal processing circuit 25 generates a reproduction signal based on the detection signal from the optical pickup device 2.
  • the generated reproduction signal is output to an external computer or the like via the interface 26.
  • an external computer or the like can receive a signal recorded on the optical recording medium 1 as a reproduction signal.
  • the signal processing circuit 25 generates a control signal such as a tracking error signal or a focus error signal based on the detection signal from the optical pickup device 2 and outputs the control signal to the optical disk controller 25.
  • optical disk device 20 shown in FIG. 4 by providing the optical pickup device 2 described above, it is possible to provide an optical disk device that realizes a good recording or reproducing operation at low cost and small size. Can be.
  • an optical pickup device for an optical recording medium having a plurality of recording surfaces or an optical disk device including the above optical pickup device is provided for each recording surface. Since a light source having a plurality of laser light emitting units for emitting laser light to irradiate the corresponding recording surface through a common objective lens is provided, if the recording or reproducing operation is performed using the light emitting unit corresponding to each recording surface, This makes it possible to realize a good recording or reproducing operation at a lower cost and a smaller size than an optical system using a wavefront aberration correcting element such as a liquid crystal element.
  • the light emitting section is configured as a semiconductor laser chip, and the positional relationship between the chips in the optical axis direction is designed, managed and adjusted at the manufacturing stage, so that the device can be manufactured accurately and the positional relationship can be adjusted later Can be eliminated.

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

Abstract

Cette invention se rapporte à un capteur optique pour un support d'enregistrement optique (1) comportant plusieurs faces d'enregistrement (1a, 1b), dans lequel est disposée une source lumineuse, présentant plusieurs sections photoémettrices laser (a, b) qui sont prévues pour des faces d'enregistrement respectives (1a, 1b) et qui sont ajustées et réglées dans leurs positions mutuelles dans le sens de l'axe optique, de façon à ne provoquer aucune aberration sphérique due aux caractéristiques optiques du faisceau laser appliqué à la face d'enregistrement correspondante (1a, 1b) par l'intermédiaire d'une lentille objectif commune (8). Dès lors que l'opération d'enregistrement ou de lecture peut être effectuée au moyen de la section photoémettrice (a, b) correspondant à la face d'enregistrement (1a, 1b), une opération d'enregistrement ou de lecture de bonne qualité peut être réalisée au moyen d'un système optique de petite taille et de faible coût, par rapport à ceux utilisant un élément de correction d'aberration d'ondes, par exemple un élément à cristaux liquides.
PCT/JP2004/010662 2003-11-13 2004-07-27 Capteur optique et le lecteur de disques optiques WO2005048249A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2003384043A JP2005149596A (ja) 2003-11-13 2003-11-13 光ピックアップ装置及び光ディスク装置
JP2003-384043 2003-11-13

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WO2005048249A1 true WO2005048249A1 (fr) 2005-05-26

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04243024A (ja) * 1991-01-17 1992-08-31 Toshiba Corp 情報記録・再生装置
JP2004241088A (ja) * 2003-02-07 2004-08-26 Nippon Hoso Kyokai <Nhk> 光記録再生方法、光記録再生装置、及び光記録媒体

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04243024A (ja) * 1991-01-17 1992-08-31 Toshiba Corp 情報記録・再生装置
JP2004241088A (ja) * 2003-02-07 2004-08-26 Nippon Hoso Kyokai <Nhk> 光記録再生方法、光記録再生装置、及び光記録媒体

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