WO2005066947A1 - Dispositif a tete optique - Google Patents

Dispositif a tete optique Download PDF

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Publication number
WO2005066947A1
WO2005066947A1 PCT/JP2004/013047 JP2004013047W WO2005066947A1 WO 2005066947 A1 WO2005066947 A1 WO 2005066947A1 JP 2004013047 W JP2004013047 W JP 2004013047W WO 2005066947 A1 WO2005066947 A1 WO 2005066947A1
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WO
WIPO (PCT)
Prior art keywords
light beam
optical
objective lens
head device
parallel
Prior art date
Application number
PCT/JP2004/013047
Other languages
English (en)
Japanese (ja)
Inventor
Kenya Nakai
Fumihiro Shiroki
Keiji Nakamura
Masahisa Shinoda
Original Assignee
Mitsubishi Denki Kabushiki Kaisha
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 Mitsubishi Denki Kabushiki Kaisha filed Critical Mitsubishi Denki Kabushiki Kaisha
Priority to JP2005516793A priority Critical patent/JP4308204B2/ja
Priority to TW093132897A priority patent/TWI279792B/zh
Publication of WO2005066947A1 publication Critical patent/WO2005066947A1/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
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1353—Diffractive elements, e.g. holograms or gratings
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
    • G11B7/127—Lasers; Multiple laser arrays
    • G11B7/1275—Two or more lasers having different wavelengths
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/13—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
    • G11B7/1356—Double or multiple prisms, i.e. having two or more prisms in cooperation
    • 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
    • G11B7/1378—Separate aberration correction lenses; Cylindrical lenses to generate astigmatism; Beam expanders
    • 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
    • G11B7/12—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
    • G11B7/1395—Beam splitters or combiners
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B2007/0003—Recording, reproducing or erasing systems characterised by the structure or type of the carrier
    • G11B2007/0006—Recording, reproducing or erasing systems characterised by the structure or type of the carrier adapted for scanning different types of carrier, e.g. CD & DVD
    • 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
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0901—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following only
    • G11B7/0903—Multi-beam tracking systems
    • 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
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0908—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only
    • G11B7/0909—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only by astigmatic methods

Definitions

  • the present invention relates to an optical head device mounted on an optical disk recording / reproducing device, and more particularly, to an optical head device capable of suppressing the influence of wavefront aberration on recording / reproducing characteristics.
  • An optical head device is mounted as a device for reading and writing information in various optical disk recording / reproducing devices such as a CD player, a DVD player, and an MD player. With the miniaturization and price reduction of the optical disk recording / reproducing device itself, the optical head device is also required to have higher density, higher performance, smaller size, thinner, and lower cost.
  • FIGS. The configuration of a conventional optical head device is shown, for example, in FIGS.
  • the collimator lens converts a light beam, which also emits the power of a semiconductor laser as a light source, into a parallel light beam. Then, the parallel light beam enters the objective lens.
  • An optical system using such a parallel light beam is called an infinite optical system.
  • an optical head device of the infinite optical system as described above exists, there is also an optical head device having a simple configuration without the collimator lens in the conventional optical head mounting force.
  • Such an optical head device without a collimator lens adopts a configuration in which a diffused light beam, not a parallel light beam, is incident on an objective lens.
  • Such a configuration in which the diffused light beam enters the objective lens is called a finite optical system.
  • An optical head device of a finite optical system is shown in FIG. 1 of Patent Document 1 below, for example.
  • Patent Document 1 In addition to Patent Document 1 and Non-Patent Document 1, the following documents are cited as prior art documents relating to the present invention.
  • the optical head device of the finite optical system is advantageous in miniaturization, thinning, and cost reduction with a small number of components because a collimator lens is unnecessary.
  • an optical head device of a finite optical system adopts a configuration in which a diffused light beam is incident on an objective lens. For this reason, when the angle of incidence of the light beam on the objective lens changes due to the light source being shifted by the lens optical axis force of the objective lens, wavefront aberration occurs. Then, the quality of the focused light beam deteriorates. Objective This is because the entrance surface of the lens has a spherical or aspherical shape, so that if incident light deviated from the optical axis of the lens passes through the objective lens, it will not be focused.
  • recording marks which are data, are arranged in a circular or spiral shape on a recording surface of an optical disc information recording medium recorded / reproduced by an optical disc recording / reproducing apparatus.
  • the optical disk recording / reproducing device scans the light beam condensed by the objective lens along the track and reads the reflected light power data.
  • the optical disk information recording medium is rotated by a motor or the like about the center of the track as a central axis.
  • the optical disk recording / reproducing apparatus needs to control the focal position of the optical beam so as to follow the track displacement.
  • the optical head device itself can be displaced by a servo mechanism.
  • the position control of the light beam with respect to the track displacement by the servo mechanism for displacing the entire optical head device is not desirable in terms of the precision and the power consumption.
  • the objective lens can be independently displaced minutely in the radial direction of the optical disc information recording medium in the optical head device. ing. Specifically, an objective lens displacement mechanism using an electromagnetic force generated by a coil or the like is provided in the optical head device so that the objective lens can be displaced.
  • the objective lens displacement mechanism controls the position of the objective lens based on positional deviation information between a track and a light beam obtained from reflected light from an optical disk information recording medium. Therefore, the objective lens displacement mechanism causes the objective lens to follow the track movement of the optical disk information recording medium.
  • the objective lens If the objective lens is caused to follow the track movement while applying force, the light source is displaced on the lens optical axis of the objective lens. As a result, wavefront aberration occurs, and the recording / reproducing characteristics deteriorate.
  • the position of the light source can be regarded as being substantially infinite when viewed from the objective lens. Therefore, even if the objective lens is displaced, the optical axis of the light beam does not deviate in the optical axis force of the objective lens (that is, the angle of incidence of the light beam on the objective lens does not change). The generation of wavefront aberration is not a problem.
  • Patent Document 1 Japanese Patent Application Laid-Open No. 2003-208731
  • Non-patent Document 1 Heitaro Nakajima and Hiroshi Ogawa, "Illustration Compact Disk Reader (Revised 3rd Edition;)", Ohmsha Publishing, May 20, 1996, p.208
  • Non-Patent Document 2 Akira Arimoto et al., "Study of Allowable Aberration of Optical System in Optical Video Disc” Optics, Optical Society of Japan (JSPS) Vol. 12, No. 6, p. 494 (1983)
  • Non-Patent Reference 3 Warren J. 3 ⁇ 4mith, “Modern uptical Engineering the design of optical systems” McGraw-Hill, 1966, pp.83—84
  • the present invention has been made in view of the above circumstances, and is intended to reduce the size, thickness, and cost by adopting a configuration in which a diffused light beam that is not a parallel light beam is incident on an objective lens. It is an object of the present invention to provide an optical head device capable of suppressing the influence of the wavefront aberration on the recording and reproduction characteristics.
  • a first aspect of the optical head device has a light source that emits a light beam, and a diffraction surface on which a grooved diffraction grating is formed.
  • a diffractive optical element for generating diffracted light; and an objective lens for condensing the plurality of diffracted lights on an optical disc information recording medium, wherein the diffractive optical element is configured such that the light source is a lens optical axis of the objective lens.
  • the information recording medium is characterized by having astigmatism in a direction to cancel astigmatism generated by moving away in the radial direction of the information recording medium.
  • the light source that not only generates a plurality of diffracted lights is a lens optical axis force of an objective lens. It also has astigmatism in the direction to cancel astigmatism generated by moving away from the body in the radial direction. Therefore, even when the light beam is incident on the objective lens as a diffused light that is not a parallel light beam, the effect of the wavefront aberration on the recording / reproduction characteristics can be suppressed by the diffractive optical element without using a collimator lens. It is.
  • a first light source that emits a light beam
  • a second light source that emits another light beam
  • a first surface that receives the light beam
  • a second surface for receiving the other light beam
  • a transmission / reflection surface for transmitting the light beam received on the first surface and reflecting the other light beam received on the second surface
  • a dichroic prism having a third surface for emitting, in the same direction, the light beam transmitted through the transmission-reflection surface and the other light beam reflected by the transmission-reflection surface, and the dichroic prism on an optical disk information recording medium.
  • the third surface also passes through the transmission / reflection surface.
  • the first surface and the third surface of the dichroic prism are parallel, and the second surface and the third surface also pass through the transmissive / reflective surface.
  • the third surface is equivalently parallel, and the third surface is arranged at a predetermined angle to the direction of the lens optical axis of the radial direction objective lens. Therefore, both the light beam emitted from the first light source and the other light beams emitted from the second light source have an operation equivalent to passing through a parallel plate optical element inclined at a predetermined angle from the radial direction. Will receive it.
  • the dichroic prism has astigmatism in the direction of canceling astigmatism generated by the light source moving away from the objective lens in the radial direction of the optical disc information recording medium. Therefore, even when the light beam and other light beams are incident on the objective lens as diffused light that is not a parallel light flux, the recording / reproducing characteristics due to wavefront aberration can be reduced by the dichroic prism without using a collimator lens. It is possible to suppress the effects.
  • a third aspect according to the present invention provides a first light source that emits a light beam and another light beam that emits another light beam.
  • a second light source a first surface receiving the light beam, a second surface receiving the other light beam, and the light beam received on the second surface while transmitting the light beam received on the first surface.
  • the other light beam reflects a transmission'reflection surface, and a third surface that emits, in the same direction, the light beam transmitted through the transmission'reflection surface and the other light beam reflected by the transmission'reflection surface.
  • a dichroic prism having: a first dichroic prism; and an objective lens for condensing the light beam and the other light beam emitted from the third surface of the dichroic prism onto an optical disk information recording medium,
  • the surface and the third surface are parallel to each other, and the second surface and the third surface pass through the transmission / reflection surface, so that the other light beam reflected by the transmission / reflection surface is reflected.
  • the second surface and the third surface are not
  • the wedge-shaped flat plate optical element functions as a parallel entrance surface and exit surface, and the third surface is arranged at a predetermined angle in the direction of the radial optical force of the objective lens. It is characterized by that.
  • the first surface and the third surface of the dichroic prism are parallel and the dichroic prism is formed.
  • the second and third surfaces of the system pass through the transmission and reflection surfaces, making the second and third surfaces equivalently non-parallel to other light beams reflected by the transmission and reflection surfaces.
  • a wedge-shaped flat plate optical element that functions as a surface and an exit surface is configured, and the third surface is disposed at a predetermined angle from the radial direction to the direction of the lens optical axis of the objective lens.
  • the astigmatism in the direction to cancel the astigmatism generated by the light source moving away from the lens optical axis of the objective lens in the radial direction of the optical disc information recording medium is defined as:
  • the dichroic prism has.
  • the amount of astigmatism generated in the light beam reflected by the transmission / reflection surface can be changed by the angle difference between the second surface and the third surface, and the amount of astigmatism generated in the light beam can be reduced. Gives design freedom.
  • FIG. 1 is a diagram showing a basic configuration of an optical head device according to Embodiment 1 of the present invention.
  • FIG. 2 is a diagram showing a wavefront aberration generated by a relative optical axis shift from a lens optical axis of an objective lens to a light source in the optical head device according to the first embodiment of the present invention.
  • FIG. 3 is a schematic diagram showing a light-collecting position in a radial section and a tangential section when the objective lens is moved in the radial direction in the optical head device according to Embodiment 1 of the present invention.
  • FIG. 4 is a perspective view showing a positional relationship between an optical disc information recording medium and a radial direction, a tangential direction, and the like.
  • FIG. 5 is a perspective view showing a shape of a diffractive optical element used in the optical head device according to Embodiment 1 of the present invention.
  • FIG. 6 is another perspective view showing the shape of the diffractive optical element employed in the optical head device according to Embodiment 1 of the present invention.
  • FIG. 7 is a perspective view showing another shape of the diffractive optical element used in the optical head device according to Embodiment 1 of the present invention.
  • FIG. 8 is another perspective view showing another shape of the diffractive optical element employed in the optical head device according to Embodiment 1 of the present invention.
  • FIG. 9 is a diagram showing a recording surface of a read-only optical disc information recording medium.
  • FIG. 10 is a diagram showing a recording surface of a writable optical disk information recording medium.
  • FIG. 11 is a diagram showing a change in a combined value of off-axis astigmatism generated by radial movement of an objective lens according to astigmatism generated by a diffractive optical element.
  • FIG. 12 is a schematic diagram showing light condensing positions in a radial section and a tangential section in a state where the objective lens is moved in the radial direction in the optical head device according to Embodiment 1 of the present invention.
  • FIG. 13 is a perspective view showing another shape of the diffractive optical element used in the optical head device according to Embodiment 1 of the present invention.
  • FIG. 14 shows another example of the diffractive optical element employed in the optical head device according to Embodiment 1 of the present invention. It is a perspective view which shows a shape.
  • FIG. 15 is a perspective view showing another shape of the diffractive optical element used in the optical head device according to Embodiment 1 of the present invention.
  • FIG. 16 is a perspective view showing another shape of the diffractive optical element used in the optical head device according to Embodiment 1 of the present invention.
  • FIG. 17 is a view showing the direction in which the grooves of the diffraction grating of the diffractive optical element employed in the optical head device according to Embodiment 1 of the present invention extend.
  • FIG. 18 is a diagram showing a basic configuration of an optical head device according to Embodiment 2 of the present invention.
  • FIG. 19 is a diagram showing the shape and arrangement of a parallel plate type diffractive optical element in an optical head device according to Embodiment 2 of the present invention.
  • FIG. 20 is a diagram showing the shape and arrangement of a parallel plate type diffractive optical element in an optical head device according to Embodiment 2 of the present invention.
  • FIG. 21 is a diagram showing another configuration example of the optical head device according to Embodiment 2 of the present invention.
  • FIG. 22 is a diagram showing a basic configuration of an optical head device according to Embodiment 3 of the present invention.
  • FIG. 23 is a diagram showing a specific shape of a dichroic prism in an optical head device according to Embodiment 3 of the present invention.
  • FIG. 24 is a diagram showing a basic configuration of an optical head device according to Embodiment 4 of the present invention.
  • FIG. 25 illustrates movement of the diffraction grating element according to Embodiment 4 of the present invention.
  • FIG. 26 is a diagram showing a position of a light beam on a photodetector according to Embodiment 4 of the present invention.
  • FIG. 27 is a diagram showing a basic configuration of an optical head device according to Embodiment 5 of the present invention.
  • FIG. 28 is a diagram showing a hologram element according to Embodiment 5 of the present invention.
  • FIG. 29 is a diagram showing a focused state of a semi-luminous beam according to Embodiment 5 of the present invention.
  • FIG. 30 is a diagram showing a light receiving area of the photodetector according to Embodiment 5 of the present invention.
  • the diffractive optical element is provided with a function of generating astigmatism as well as a diffractive function, so that the light source moves away from the lens optical axis of the objective lens in the radial direction of the optical disc information recording medium.
  • Optical head device that cancels astigmatism generated by It is a place.
  • FIG. 1 is a diagram showing a basic configuration of an optical head device according to the present embodiment.
  • This optical head device employs a finite optical system having no collimator lens.
  • reference numeral 1 denotes a semiconductor laser as a light source
  • reference numeral 2a denotes a light beam emitted from the semiconductor laser
  • reference numeral 3 denotes a flat glass serving as an exit window of the light beam 2a
  • reference numeral 4 denotes a semiconductor laser 1.
  • a heat dissipating metal package having a function of integrating the semiconductor laser 1 and the flat glass 3 and dissipating heat generated when the semiconductor laser 1 emits light.
  • the integrated structure of the semiconductor laser 1, the flat glass 3, and the heat dissipating metal package 4 is referred to as a light emitting component 5.
  • Reference numeral 6 denotes a diffractive optical element for diffracting the light beam 2a and dispersing it into a plurality of diffracted light beams 2b.
  • Reference numeral 7 deflects the light beam 2b into a light beam 2c by a reflection surface provided inside.
  • Reference numeral 8 denotes an optical disk information recording medium such as a CD, DVD, or MD, and reference numeral 9 denotes an objective lens that focuses the light beam 2c from the deflection prism 7 on the optical disk information recording medium 8 as a light beam 2d. Since no collimator lens is provided in the path of the light beams 2a-2c, the light beams 2a-2c do not become parallel light beams but become diffused light. Therefore, this optical head device is a finite optical system.
  • the light beam 2d reflected by the optical disk information recording medium 8 again enters the objective lens 9, is converted into convergent light having the optical axes Alb and Ale as central axes, and passes through the deflecting prism 7.
  • the light beam 2e transmitted through the deflecting prism 7 passes through the detection optical element 11 to become a light beam 2f and enters the light detector 10.
  • the photodetector 10 is a photodiode provided with a plurality of divided light receiving surfaces according to the optical system.
  • the light detector 10 converts the amount of the light beam 2f incident on each light receiving surface from the objective lens 9 into an electric signal and outputs the electric signal.
  • the detection optical element 11 is an optical element for appropriately causing the light beam 2e reflected by the optical disk information recording medium 8 to enter the divided light receiving surface of the photodetector 10.
  • the detection optical element 11 is formed of, for example, a concave lens and has a lens function and a beam dividing function.
  • optical disc information recording medium 8 On the optical disc information recording medium 8, tracks in which recording marks (pits) as data are arranged in a circle or a spiral are formed, and the arrangement forms the tracks.
  • An optical disk recording / reproducing apparatus on which the optical head device according to the present embodiment is mounted is an objective laser.
  • the light beam 2d converged by the lens 9 is scanned along the track, and data is read from the reflected light.
  • the optical disk information recording medium 8 is rotated by a motor (not shown) around the center of the track as a central axis.
  • the optical disk recording / reproducing apparatus needs to control the radial position of the optical beam 2d so as to follow the track displacement.
  • the optical head device itself can be displaced by a servo mechanism (not shown).
  • a servo mechanism not shown.
  • radial position control of the light beam by a servo mechanism for displacing the entire optical head device is not desirable from the viewpoint of accuracy and power consumption.
  • the objective lens 9 is independently provided in the optical head device in the radial direction of the optical disk information recording medium 8. Can be moved in parallel. Specifically, an objective lens displacement mechanism (not shown) using an electromagnetic force generated by a coil or the like is provided in the optical head device so that the objective lens 9 can be displaced. This objective lens displacement mechanism calculates the amount of displacement between one track and one light beam based on the signal output from the optical detector 10 after receiving the reflected light from the optical disk information recording medium 8 and controlling the position of the objective lens 9. Perform
  • the semiconductor laser 1 as a light source substantially exists on the lens optical axis of the objective lens 9.
  • the position 9 is often set as the initial design position of the objective lens 9 in the objective lens displacement mechanism.
  • the optical axes Ala and Alb determined by the principal point of the objective lens 9 and the position of the light source at the initial design position are referred to as design optical axes.
  • the light beams 2a-2c from the semiconductor laser 1 enter the objective lens 9 as diffused light.
  • the position of the semiconductor laser 1 as a light source is set with respect to the lens optical axis of the objective lens 9. It will be located off-axis. Therefore, the light beam 2c is The transmission through the lens 9 causes a wavefront aberration.
  • FIG. 2 is a diagram showing a typical characteristic example of a wavefront aberration generated by a relative optical axis shift of the light source with respect to the lens optical axis of the objective lens 9.
  • Typical aberration components of wavefront aberration include astigmatism, coma, spherical aberration, and higher-order aberrations. Further, the total aberration represents a composite value of all these aberrations. Astigmatism occupies the largest proportion of these generated aberrations, and is called off-axis astigmatism.
  • FIG. 3 is a diagram schematically showing a cross section of the light beam 2 in the radial direction D1 and the tangential direction D2 orthogonal thereto.
  • FIG. 4 is a perspective view showing a positional relationship between the optical disc information recording medium 8 and the radial direction Dl, the tangential direction D2, and the like.
  • FIG. 3 for the sake of simplicity, it is assumed that the light beam 2 from the semiconductor laser 1 is directly incident on the objective lens 9 without considering the deflection by the deflection prism 7.
  • the y axis is the same direction as the radial direction D1
  • the X axis is the same direction as the tangential direction D2
  • the z axis is the direction orthogonal to both the x and y axes.
  • the front focal line F2 near the optical disc information recording medium 8 has a direction parallel to the radial direction
  • the rear focal line F1 near the objective lens 9 has a direction parallel to the tangential direction.
  • the objective lens 9 When the objective lens 9 is controlled to be displaced in the radial direction and a relative optical axis shift occurs between the semiconductor laser 1 as the light source and the objective lens 9, the condensing position of the light beam 2 d is changed to the optical disk information. Since the light beam 2d moves from the recording medium 8 toward the objective lens 9 in the direction, the spot shape of the light beam 2d on the optical disk information recording medium 8 changes in the radial direction into an elongated and elliptical shape.
  • the spot of the light beam 2d spreads to the track adjacent to the track being read or written, and the crosstalk of the adjacent track force increases.
  • the resolution in the radial direction is deteriorated, and the ability of the light beam 2d to detect the crossing of the track is also reduced.
  • the position of the objective lens 9 is set so that the recording surface of the optical disc information recording medium 8 is located at a substantially intermediate position between the position of the front focal line F2 and the position of the rear focal line F1. Control in the direction Then, the spot shape of the light beam 2d on the recording surface of the optical disc information recording medium 8 can be made substantially circular. It is thought that this can prevent deterioration of the resolution in the radial direction.
  • the spot of the light beam 2d at that time is larger than that in the case where there is no relative optical axis shift due to the existence of the wavefront aberration. Therefore, the resolution in the tangential direction decreases, and the recording / reproducing characteristics deteriorate.
  • the diffractive optical element 6 has the shape shown in FIGS. 5 and 6, or the shape shown in FIGS. 7 and 8.
  • the diffractive optical element 6a shown in FIGS. 5 and 6 has a diffraction surface 102a on which a diffraction grating DF is formed, and a back surface 101a.
  • the diffraction surface 102a is a plane.
  • the curvature in the ⁇ -axis direction which is the short axis direction of the diffractive optical element 6a
  • the curvature in the ⁇ -axis direction which is the long axis direction of the diffractive optical element 6a
  • the back surface 101a is a convex toric surface having a different curvature and a different curvature C
  • the direction of the grooves of the diffraction grating DF formed on the diffraction surface 102a is substantially parallel to the
  • the traveling direction of the light beam 2a is defined as the ⁇ axis.
  • the axes ⁇ , ⁇ are orthogonal to each other.
  • the light beam 2a emitted from the light emitting component 5 is incident on the back surface 101a of the diffractive optical element 6a, and then the diffraction surface 102a
  • the upper diffraction grating DF splits the light into at least two light beams 2bl-2b3.
  • the number of light beams to be dispersed varies depending on the application.For example, here is the case where light beams are dispersed into three light beams (0th-order diffracted light beam 2bl, + 1st-order diffracted light beam 2b2, and 1st-order diffracted light beam 2b3). Is shown.
  • the 0th-order diffracted light beam 2bl is a transmitted light that is not subjected to a diffraction effect, and is used for recording and reproducing on the optical disc information recording medium 8. Further, the + 1st-order diffracted light beam 2b2 and the 1st-order diffracted light beam 2b3 are both diffracted lights that have undergone a diffractive action and have an optical path bent. Both the 0th-order diffracted light beam 2bl, + the 1st-order diffracted light beam 2b2 and the 1st-order diffracted light beam 2b3 are condensed on the optical disk information recording medium 8 by the objective lens 9 and then reflected, and are respectively received by the photodetector 10. Is done.
  • the diffractive optical element 6b shown in FIGS. 7 and 8 has a diffraction surface 102b on which a diffraction grating DF is formed, and a back surface 101b.
  • the diffraction surface 102b is a plane.
  • the curvature of the diffractive optical element 6b in the ⁇ -axis direction, which is the minor axis direction, is, and the curvature of the diffractive optical element 6b in the ⁇ -axis direction, which is the major axis direction, is C ⁇ .
  • the back surface 101b is a concave toric surface having a different curvature and a different curvature C
  • the direction of the grooves of the diffraction grating DF formed on the diffraction surface 102b is substantially parallel to the
  • the light beam 2a emitted from the light emitting component 5 is incident on the back surface 101b of the diffractive optical element 6b and then diffracted on the diffractive surface 102b.
  • the grating DF splits the beam into at least two or more light beams 2b1 and 2b3.
  • the diffraction gratings DF are not provided on the back surfaces 101a and 101b of the diffraction surfaces, but the diffraction gratings DF are formed not only on the diffraction surfaces 102a and 102b but also on the back surfaces 101a and 101b.
  • a grid DF may be provided.
  • a diffraction grating DF may be provided only on the back surfaces 101a and 101b, and this may be used as a diffraction surface.
  • the 0th-order diffracted light beam 2bl, the + 1st-order diffracted light beam 2b2, and the ⁇ 1st-order diffracted light beam 2b3 separated by the diffraction grating DF of the diffractive surface 102a or 102b are placed on the optical disc information recording medium 8 by the objective lens 9 respectively.
  • the light is converged as a second-order diffracted light beam 2dl, a + first-order diffracted light beam 2d2, and a first-order diffracted light beam 2d3.
  • FIG. 9 is a diagram showing a recording surface of a read-only optical disc information recording medium 8 on which information marks are recorded side by side in the tangential direction D2.
  • FIG. 10 is a diagram showing a recording surface of a writable optical disk information recording medium 8 having a guide groove GR along which a recording mark is recorded.
  • the direction of the arrangement of the three diffracted light beams 2dl-2d3 can be adjusted by rotating the diffracted optical element 6a or 6b around the designed optical axis.
  • a three-beam method is often used for an optical disc information recording medium having a structure without a guide groove GR.
  • the angle ⁇ a of the displacement in the arrangement direction of the three diffracted light beams 2dl—2d3 from the tangential direction D2 is determined by the fact that the radial arrangement distance of the diffracted light beams 2d2 and 2d3 is approximately It is adjusted to an angle that is (N + 1Z2) times the period (N is any integer).
  • the angle of deviation in the arrangement direction of the three diffracted light beams 2dl-2d3 varies depending on the difference in the structure of the optical disc information recording medium and the difference in the deviation detection method, and is relatively large. In some cases, it may be set, while in others it may be set relatively small.
  • the ⁇ -axis is rotated in the tangential direction force, for example, the above-mentioned ⁇ a (in the case of Fig. 9; If the j8 axis is adjusted to the direction in which the radial force is also rotated by, for example, the above ⁇ a (in the case of FIG. 9; ⁇ b in the case of FIG. 10), the three diffracted light beams 2dl— Adjustment in the 2d3 array direction is possible.
  • the 0th-order diffracted light beam 2dl, the + 1st-order diffracted light beam 2d2, and the 1st-order diffracted light beam 2d3 are reflected by the optical disc information recording medium 8, respectively. Then, each reflected diffracted light beam is received by the photodetector 10, and each light amount is output as an electric signal.
  • the electric signals corresponding to the + 1st-order diffracted light beam 2d2 and the ⁇ 1st-order diffracted light beam 2d3 are subjected to calculations according to the deviation detection method, and the 0th-order diffracted light beam 2dl and the information mark sequence are , A tracking error signal representing the relative positional deviation in the radial direction is generated. For example
  • the diffractive optical element 6a or 6b when the light beam 2a passes through the toric surface of the back surface 101a or 101b of the diffractive surface, due to the difference between the curvatures C y and C j8 in the ⁇ -axis direction and the j8-axis direction, Astigmatism occurs. Therefore, by providing the diffractive optical element 6a or 6b with a function of generating astigmatism that is not limited to the diffraction function, the semiconductor laser 1 as a light source is used as a light source for the lens 9 of the objective lens 9. What is necessary is just to cancel the astigmatism generated by moving away in the direction.
  • 8 are set so that the diffractive optical element 6a or 6b has astigmatism in a direction to cancel off-axis astigmatism generated by moving the objective lens 9 in the radial direction. decide.
  • FIG. 11 is a diagram showing a change in a combined value Was of off-axis astigmatism generated by radial movement of the objective lens 9 according to astigmatism generated by the diffractive optical element 6a or 6b.
  • the curve (a) corresponds to the graph of astigmatism in FIG.
  • three states are shown as curves (b), (c), and (d) according to the difference in the amount of astigmatism generated in the diffractive optical element 6a or 6b.
  • the amount of astigmatism generated in the diffractive optical element 6a or 6b is defined as AS g (corresponding to the value of the intercept on each curve in FIG. 11).
  • the relationship between the front focal line F2 and the rear focal line F1 is the relationship shown in FIG. In this case, as shown in FIG. 12, the position of the front focal line F2 and the position of the rear focal line F1 of the light beam are in the relationship of being switched in the case of FIG.
  • the astigmatism amount ASg generated by the diffractive optical element 6a or 6b is set so that the characteristic value of the combined value of the off-axis astigmatism, the characteristic force Was, falls between the curve (b) and the curve (d). Do it.
  • the value of the astigmatism amount ASg is set by the values of the curvatures C y and C of the diffractive optical elements 6a and 6b.
  • the diffractive optical element 6 may have a cylindrical surface shape as shown in FIGS. 13 to 16 as in FIGS. 5 to 8. The effect of generating a large astigmatism is obtained.
  • the diffractive optical element 6c shown in FIG. 13 has a convex cylindrical surface having a curvature only in the ⁇ -axis direction on the back surface 101c of the diffraction surface 102c, and a groove substantially parallel to the
  • a diffraction grating DF having the following formula is formed.
  • the diffractive optical element 6d shown in FIG. 14 has a diffractive grating having a convex cylindrical surface having a curvature only in the ⁇ -axis direction on the diffraction surface 102d and a groove substantially parallel to the
  • DF is formed.
  • the back surface lOld of the diffraction surface 102d is a flat surface.
  • the diffractive optical element 6e shown in FIG. 15 has a concave cylindrical surface having a curvature only in the ⁇ -axis direction on the back surface 101e of the diffraction surface 102e, and has a substantially parallel groove in the
  • the diffraction grating DF is formed.
  • the diffractive optical element 6f shown in FIG. 16 has a concave cylindrical surface having a curvature only in the 8-axis direction on the diffraction surface 102f, and a diffractive surface having grooves substantially parallel to the
  • a grid DF is formed.
  • the back surface 101f of the diffraction surface 102f is a flat surface.
  • the diffraction grating DF is not provided on the back surface 101c to 101f of the diffraction surface, but not only the diffraction surfaces 102c to 102f.
  • a diffraction grating DF may be provided on the back surface 101c-101f.
  • a diffraction grating DF may be provided only on the back surface 101c-1 Olf, and this may be used as a diffraction surface.
  • the spherical aberration and the best image surface force of the light beam focused on the optical disk information recording medium 8 are measured.
  • An aberration (referred to as defocus aberration) caused by defocusing caused by the displacement of the lens 9 in the lens optical axis direction occurs.
  • the toric surface shape shown in FIG. 5 to FIG. 8 when the toric surface shape shown in FIG. 5 to FIG. 8 is adopted, by optimizing the curved surfaces in the ⁇ direction and the j8 direction of the toric surface as aspheric surfaces, a spherical surface besides astigmatism can be obtained. Aberration and defocus aberration can be reduced. In addition, the spherical aberration caused by the distance between the objective lens 9 and the light source deviating from the design value of the objective lens 9 and the thickness of the protective transparent substrate formed on the optical disk information recording medium 8 By optimizing the above-mentioned aspherical shape in consideration of the spherical aberration generated by force such as an error, the quality of the light beam can be further improved, and the recording / reproducing characteristics can be improved. On the other hand, when the cylindrical surface shape shown in FIGS. 13 to 16 is adopted, the amount of astigmatism can only be adjusted.
  • the diffractive surface of the diffractive optical element 6 or the back surface of the diffractive surface is a toric surface or a cylindrical surface
  • the curvature (for example) of a certain meridional surface in the toric surface and the other meridian surface perpendicular to it are obtained.
  • the amount of astigmatism of the diffractive optical element 6 can be adjusted by adjusting the curvature (for example, C
  • a certain meridional surface in the toric surface and another meridional surface perpendicular to the toric surface are formed into an aspherical shape, so that a light beam emitted from a light source that is only affected by astigmatism is reduced to an optical disk. It is also possible to adjust the spherical aberration and the amount of defocus aberration generated in the optical system until the light is focused on the information recording medium 8. Therefore, the quality of the light beam used for recording and reproduction can be further improved.
  • the track direction that is, the tangential direction D2, and the arrangement direction of the 0th-order diffracted light beam 2dl, + 1st-order diffracted light beam 2d2, and 1st-order diffracted light beam 2d3
  • the angle ⁇ a or ⁇ b is provided between the above, the diffractive optical element 6 is rotated in the above.
  • the astigmatism of the diffractive optical element 6 also rotates, and the off-axis astigmatism generated in the objective lens 9 may not be able to be canceled efficiently.
  • the toric surface or the toric surface of the diffractive optical element 6 is set so that the amount of astigmatism generated in the diffractive optical element 6 can cancel out the off-axis astigmatism generated in the objective lens 9 most efficiently. While the direction of curvature of the cylindrical surface is parallel to at least one of the tangential direction D2 and the radial direction D1, the direction in which the groove of the diffraction grating DF extends is only ⁇ a or ⁇ b from the 13th axis as shown in Fig. 17. It is desirable to shift.
  • the direction of the groove of the diffraction grating DF is inclined at an angle ⁇ a or ⁇ b from the radial direction (corresponding to the direction of the ⁇ axis) to the direction of the tangential direction of the optical disc information recording medium 8.
  • a plurality of diffracted lights can be arranged on the optical disc information recording medium 8 at an angle of ⁇ a or ⁇ b with respect to the track direction of the optical disc information recording medium 8, and the diffractive optical element can be arranged.
  • the diffractive optical element 6 can be arranged so that the astigmatism of the objective lens 9 can be canceled most efficiently by the radial movement of the objective lens 9.
  • the diffractive optical element 6 uses the semiconductor laser 1 as a light source that merely generates a plurality of diffracted light beams as a light source.
  • the recording medium 8 also has astigmatism in a direction to cancel astigmatism generated by moving away from the recording medium 8 in the radial direction. Therefore, even when the light beam is incident on the objective lens 9 as a diffused light that is not a parallel light beam, the influence of the wavefront aberration on the recording / reproduction characteristics can be suppressed by the diffractive optical element 6 without using a collimator lens. Is possible. As a result, the size and thickness of the optical head device can be reduced and the cost can be reduced.
  • the diffractive optical element 6 by providing the diffractive optical element 6 with a function of generating astigmatism capable of canceling off-axis astigmatism generated when the objective lens 9 shifts the lens and a spectral function of the diffraction grating DF, it is desirable that It becomes possible to give astigmatism ASg in the direction.
  • the required maximum amount of lens shift is about 600 m
  • the off-axis astigmatism generated by the objective lens 9 at that time is 300 m ⁇ ⁇ It is about. Therefore, the astigmatism ASg of the diffractive optical element 6 is desirably about 300 m ⁇ or less in the direction of canceling off-axis astigmatism.
  • the amount of astigmatism takes into account off-axis astigmatism of the objective lens. In the case of an optical configuration in which astigmatism is further added by a light source or other optical components, the above-described astigmatism is used. In some cases, it should be set larger than the astigmatism amount.
  • the optical configuration described above is an example of a typical finite optical system, but the present embodiment is also applicable to a pseudo finite optical system.
  • the quasi-finite optical system means that even if the light beam emitted from the light source becomes a parallel light beam in the optical path, a separate lens or the like is provided in the optical path between the light source and the objective lens.
  • a separate lens or the like is provided in the optical path between the light source and the objective lens.
  • a separate lens or the like is provided in the optical path between the light source and the objective lens.
  • the light beam incident on the objective lens is the same as in the case of the finite optical system, so that the present embodiment can be applied.
  • This embodiment is a modification of the optical head device according to Embodiment 1, and employs a parallel plate type diffractive optical element instead of the diffractive optical element 6 having a toric surface or a cylindrical surface, The surface is also tilted in the direction of the lens optical axis of the objective lens 9 with respect to the radial force so as to generate astigmatism.
  • FIG. 18 is a diagram showing an optical head device according to the present embodiment.
  • the device configuration is the same as that of FIG. 1 except that the diffractive optical element 6 is changed to a parallel plate type diffractive optical element 61. Therefore, the points other than the parallel plate type diffractive optical element 61 are the same as those of the optical head device according to the first embodiment, and the description is omitted.
  • FIG. 19 and FIG. 20 show the shape and arrangement of the parallel-plate diffractive optical element 61 in FIG.
  • FIG. 19 is a view of the parallel-plate diffractive optical element 61 viewed from the tangential direction
  • FIG. 20 is a view of the parallel-plate diffractive optical element 61 viewed from the radial direction.
  • the parallel plate type diffractive optical element 61 is made of a parallel plate type resin or glass crystal material, and has a diffraction grating DF formed on at least one of a surface on which the light beam 2a enters and a surface on which the light beam 2a exits. ( Figures 19 and 20 show the case where the diffraction grating DF is provided only on the exit surface.)
  • the light beam 2a is split into at least two light beams 2bl-2b3 by the diffraction grating DF of the parallel plate type diffractive optical element 61.
  • the parallel-plate diffractive optical element 61 When the parallel-plate diffractive optical element 61 is given an inclination ⁇ ⁇ with respect to the design optical axis in a direction corresponding to the radial direction D1, the radiated light beam 2a causes the parallel-plate diffractive optical element 61 to Passing it causes astigmatism. Therefore, as in the case of the first embodiment, the axis described in the first embodiment that occurs when the objective lens 9 moves in the radial direction D1 due to astigmatism generated in the parallel-plate diffractive optical element 61. Outer astigmatism can be canceled.
  • the parallel plate diffractive optical element 61 has a parallel plate, in which the j8 axis, which is the direction in which the groove of the diffraction grating DF extends, is aligned with the z-axis, and the ⁇ axis, which is the direction in which the groove of the diffraction grating DF is aligned, is aligned with the X axis.
  • the diffractive surface of the diffractive optical element 61 is arranged at a predetermined angle ⁇ from the radial direction D1 to the direction of the lens optical axis Ala of the objective lens 9.
  • the astigmatism amount W22pv generated by the parallel-plate diffractive optical element 61 is obtained by calculating the numerical aperture of the light beam 2a passing through the parallel-plate diffractive optical element 61 by NA and the wavelength of the light beam 2a by:
  • ⁇ ⁇ be the distance (astigmatic difference) between the front focal line F2 and the rear focal line F1 of astigmatism
  • Equation 1 is based on Non-Patent Document 2 described above.
  • the astigmatic difference ⁇ is calculated using the thickness d and the refractive index ⁇ of the parallel-plate diffractive optical element 61 and the angle ⁇ from the radial direction D1 according to Non-Patent Document 3.
  • the amount of astigmatism ASg generated by the parallel-plate diffractive optical element 61 is expressed by the following equation. Can be determined more.
  • the arrangement direction of each of the light beams 2bl-2b3 after spectroscopy also changes the track directional force of the optical disc information recording medium 8 shown in Figs.
  • the arrangement of the parallel-plate diffractive optical element 61 is adjusted so that ⁇ b is formed with the design optical axis as the rotation axis.
  • the parallel-plate diffractive optical element 61 when the parallel-plate diffractive optical element 61 is rotated, the astigmatism of the parallel-plate diffractive optical element 61 is also rotated, and the off-axis astigmatism generated by the objective lens 9 is efficiently removed. Sometimes it can't be countered.
  • the parallel-plate diffractive optical element 61 is designed so that the amount of astigmatism generated by the parallel-plate diffractive optical element 61 can most effectively cancel the off-axis astigmatism generated by the objective lens 9.
  • the direction of the groove of the diffraction grating DF of the element 61 is desirably shifted from the radial direction D1 in the tangential direction D2 by an angle ⁇ a or ⁇ b, as in FIG.
  • the direction of the groove of the diffraction grating DF is inclined at an angle ⁇ a or ⁇ b from the radial direction (corresponding to the direction of the ⁇ axis) to the direction of the tangential direction of the optical disc information recording medium 8.
  • a plurality of diffracted lights can be arranged on the optical disc information recording medium 8 at an angle ⁇ a or ⁇ b with respect to the track direction of the optical disc information recording medium 8, and a parallel plate type
  • the parallel plate type diffractive optical element 61 can be arranged so that the astigmatism of the diffractive optical element 61 can cancel out the astigmatism generated by the radial movement of the objective lens 9 most efficiently.
  • the diffractive surface of parallel-plate diffractive optical element 61 is arranged at a predetermined angle ⁇ ⁇ from radial direction D1. Therefore, by adjusting the thickness d, the refractive index n, and the degree of inclination 0 of the parallel plate type diffractive optical element 61, the amount of astigmatism of the diffractive optical element can be easily adjusted.
  • the flat glass 3 serving as the exit window of the light beam 2a is positioned in the radial direction.
  • the parallel-plate exit window 3a has a function of generating astigmatism similarly to the parallel-plate diffractive optical element 61. However, since it is inclined obliquely from the radial direction, coma aberration is likely to occur.
  • the parallel-plate diffractive optical element 61 is applied to the light-emitting component 5a in FIG. 21, and the diffractive surface of the parallel-plate diffractive optical element 61 is oriented in the opposite direction to the exit surface of the parallel-plate exit window 3a. If it is tilted, a part or all of the coma generated by the parallel-plate exit window 3 a can be canceled by the coma generated by the parallel-plate diffractive optical element 61. Therefore, the quality of the light beam used for recording and reproduction can be further improved.
  • the required maximum amount of lens shift is about 600 m
  • the off-axis astigmatism generated by the objective lens 9 at that time is 300 m ⁇ ⁇ It is about. Therefore, the amount of astigmatism ASg of the parallel-plate diffractive optical element 61 is desirably about 300 m ⁇ or less in the direction of canceling off-axis astigmatism.
  • the amount of astigmatism takes into consideration off-axis astigmatism of the objective lens.
  • the above-described amount of astigmatism is used. In some cases, it should be set larger than the astigmatism amount.
  • This embodiment is also applicable to a pseudo finite optical system.
  • This embodiment is also a modification of the optical head device according to the first embodiment, and has a dual light source configuration, and uses a dual light source that does not allow the diffractive optical element to perform the function of generating astigmatism.
  • a dichroic prism that emits a light beam in the same direction has an astigmatism generation function.
  • FIG. 22 is a diagram showing an optical head device according to the present embodiment.
  • the semiconductor laser 1 as the first light source, the flat glass 3, the heat dissipating metal package 4, the diffractive optical element 62, the deflecting prism 7, the optical disc information recording medium 8, the objective lens 9, the photodetector 10, the detection Regarding the known optical element 11, a parallel plate type diffractive optical element 62 having a diffractive surface not inclined from the radial direction is used instead of the diffractive optical element 6, and It is the same as FIG. 1 except that a dichroic prism 12 is inserted inside. Therefore, the description of the same components as those in FIG. 1 is omitted.
  • Reference numeral 13 in FIG. 22 denotes a semiconductor laser as a second light source, which emits a light beam 14 (for example, blue light) having a wavelength different from the wavelength of the light beam 2a (for example, red light). I do.
  • Reference numeral 15 denotes a hologram element, and reference numeral 16 denotes a light receiving element formed on the same semiconductor substrate as the semiconductor laser 13.
  • the semiconductor substrate on which the semiconductor laser 13 and the light receiving element 16 are formed is mounted on a package 17 having a heat radiation function. Further, a power supply terminal 18 for supplying power to the semiconductor laser 13 and the light receiving element 16 and an output terminal 19 for outputting an electric signal from the light receiving element 16 are mounted on the package 17.
  • the hologram element 15 is integrated with the package 17 by being bonded thereto.
  • the light beam 14 emitted from the semiconductor laser 13 passes through the hologram element 15.
  • Reference numeral 12 denotes a dichroic prism, which has a characteristic of deflecting the light beam 14 in the z direction by an internal reflection surface and transmitting the light beam 2c from the deflecting prism 7 as it is.
  • the objective lens 9 a wavelength compatible type lens capable of condensing the light beams 2 c and 14 having different wavelengths on the optical disc information recording medium 8 is employed.
  • the light beam 2d output from the semiconductor laser 1 and reflected by the optical disk information recording medium 8 is converted into a light beam that is incident on the objective lens 9 again and converges, and is converted into a dichroic prism 12 and a deflecting prism 7. Through. Then, the light reaches the photodetector 10 via the detection optical element 11.
  • the light beam 14 output from the semiconductor laser 13 is reflected by the optical disk information recording medium 8 and reenters the objective lens 9, is deflected by the dichroic prism 12, and is split into the light receiving element 16 by the hologram element 15. And be deflected.
  • two light beams 2a and 14 emitted from two light sources are made incident on one objective lens 9, and the optical disk information recording medium is 8 is characterized by having a dichroic prism 12 capable of giving astigmatism in the radial direction.
  • FIG. 23 shows a specific shape of the dichroic prism 12.
  • the dichroic prism 12 has a structure in which a prism 12a and a prism 12b are attached by a transmission / reflection surface 105.
  • the transmission / reflection surface 105 functions as a reflection surface for the light beam 14 and simply functions as a transmission surface for the light beam 2c. That is, the dichroic prism 12 transmits the first surface 103 receiving the light beam 2c, the second surface 106 receiving the light beam 14, and the light beam 2c received by the first surface 103, while transmitting the light beam 2c on the second surface 106.
  • the received light beam 14 is transmitted through the transmission / reflection surface 105 and the light beam 2c transmitted through the transmission / reflection surface 105 and the light beam 14 reflected by the transmission / reflection surface 105 in the same direction in which the optical axis Aid extends. And a third surface 104 from which light is emitted.
  • the refractive index of the prism 12a and the refractive index of the prism 12b are the same (n2). Note that there is no change in the cross-sectional shape of the dichroic prism 12 in the yz plane in the x-axis direction in FIG.
  • the Z-axis parallel to the z-axis in FIG. 22 and the Y-axis parallel to the y-axis in FIG. 22 correspond to the intersection P7 between the optical axis A2 of the light beam 14 and the second surface 106. It is newly set with the origin as the origin.
  • the light source is caused by the lens optical axis force of the objective lens 9 moving away from the optical disc information recording medium 8 in the radial direction.
  • the dichroic prism 12 generates astigmatism ASg in a direction to cancel the astigmatism.
  • the perpendiculars L4, L5, L6 of the first surface 103, the third surface 104, and the second surface 106 of the dichroic prism 12 are set to the respective optical axes Alb, Aid, A2 of the incident or emitted light beam. Incline by ⁇ 7, ⁇ 7, ⁇ 1 in each direction.
  • angles ⁇ 2 and ⁇ 6 are respectively the optical axes ⁇ 4 and ⁇ 5 of each light beam inside the dichroic prism 12, the perpendicular L6 of the second surface 106, and the perpendicular L4 or L5 of the first surface 103 or the third surface 104. It is the angle between
  • the straight line L1 passing through the first surface 103 and the third surface 104 and the reflection point P6 is parallel (indicated as “parallel” by the symbol ⁇ ), and the second surface 106 and the reflection point
  • the straight line L2 passing through P6 is parallel (the symbol ⁇ / indicates“ parallel ”).
  • the angle formed between the optical axis A2 before the light beam 14 is incident and the optical axis Aid after the light beam 14 is 90 °.
  • the second surface 106 and the second are designed such that their angles are equivalently parallel through the transmission / reflection surface 105, similarly to the case where the first surface 103 and the third surface 104 are parallel. That is, when the light beam 14 passes through the dichroic prism 12, an effect equivalent to passing through the parallel-plate optical element having an inclination of ⁇ 7 is obtained.
  • the angle difference generated in the light beam 14 is also caused by this angle difference. It is possible to change the amount of astigmatism.
  • the degree of astigmatism generated in the light beam 14 and the shape of the dichroic prism 12 can be freely designed. That is, when the light beam 14 passes through the dichroic prism 12, the light receiving surface and the light emitting surface are subjected to an action equivalent to passing through a non-parallel wedge-shaped flat plate optical element.
  • astigmatism can be given in the radial direction of the optical disc information recording medium 8, and astigmatism generated when the objective lens 9 moves in the radial direction can be canceled.
  • the angle ⁇ 1 and the angle ⁇ 7 are made equal, the amount of astigmatism given to the light beam 14 can be obtained by Equation 3 as in the case of the light beam 2c.
  • the sum may be the sum of the distance drl between the second surface 106 and the straight line L2 in FIG. 23 and the distance dr2 between the third surface 104 and the straight line L1 in FIG.
  • the distance dr2 Since the distance dr2 has already been determined in the transmission optical path, optimizing the distance drl allows the desired astigmatism to be generated in the light beam 14 independently of the amount of astigmatism generated in the light beam 2c.
  • the amount of aberration ASg can be obtained.
  • the light beam 14 is refracted on the second surface 106, and is further refracted on the third surface 104 when exiting the dichroic prism 12.
  • the angle ⁇ 1 is equal to the angle ⁇ 7
  • the transmission / reflection surface 105 must be inclined by an angle ⁇ 3 which has a 45 ° angular force from the Y axis.
  • the light beam 14 is reflected at the point P6, the light beam 14 is The angle ⁇ is equal to the angle between the transmission / reflection surface 105 and the reflected optical axis ⁇ 5.
  • the angle 0 between the transmission / reflection surface 105 and the optical axis ⁇ 5 after reflection is less than the angle ⁇ 3.
  • nl is the refractive index of air outside the dichroic prism 12. So the number
  • first surface 103 and third surface 104 of dichroic prism 12 are parallel, and second surface 106 and third surface 104 are also transmissive / reflective surfaces.
  • the third surface 104 is disposed so as to be equivalently parallel to the third surface 104 through the intermediary of the objective lens 9 at a predetermined angle ⁇ 7 in the direction of the lens optical axis of the objective lens 9.
  • the operation is equivalent to passing through a parallel plate optical element inclined by an angle ⁇ 7 from the radial direction.
  • the second surface 106 and the third surface 104 of the dichroic prism 12 pass through the transmission / reflection surface, so that the transmission / reflection surface
  • the light beam 14 reflected by 105 is subjected to an action equivalent to passing the second surface 106 and the third surface 104 through a wedge-shaped flat optical element functioning as a non-parallel entrance plane and exit plane.
  • the amount of astigmatism generated in the light beam 14 reflected on the transmission / reflection surface 105 can also be changed by the angle difference between the second surface 106 and the third surface 104, and the amount of astigmatism generated in the light beam can be changed.
  • the dichroic prism 12 It is possible to give a degree of freedom to the amount of astigmatism and the design of the shape of the dichroic prism. Therefore, the astigmatism in the direction to cancel the astigmatism generated when the light source moves away from the objective lens 9 in the radial direction of the optical disc information recording medium 8 is reduced by the dichroic prism 12. Has. Therefore, even when the light beam 2c and the light beam 14 are made to enter the objective lens 9 as diffused light that is not a parallel light flux, the recording / reproducing characteristics due to wavefront aberration can be obtained by the dichroic prism 12 without using a collimator lens. It is possible to suppress the effects of As a result, the size and thickness of the optical head device can be reduced and the cost can be reduced.
  • the required maximum amount of lens shift is about 600 m
  • the off-axis astigmatism generated by the objective lens 9 at that time is 300 m ⁇ ⁇ It is about. Therefore, the amount of astigmatism ASg of the dichroic prism 12 is desirably about 300 m ⁇ or less in the direction of canceling off-axis astigmatism.
  • the amount of astigmatism takes into consideration the off-axis astigmatism of the objective lens.
  • the above-described amount of astigmatism is used. In some cases, it should be set larger than the astigmatism amount.
  • This embodiment is also applicable to a pseudo finite optical system.
  • This embodiment is a modification of the optical head device shown in FIG. 1 in the first embodiment.
  • the curvature direction of the cylindrical surface of the diffraction grating element 6 is By setting the light beam almost in the tangential direction, the optical beam device on the light receiving surface of the photodetector 10 is displaced due to positional fluctuation in a plane perpendicular to the design optical axis Ala of the diffraction grating element 6. It is intended to minimize the deterioration of the recording / reproducing characteristics.
  • FIG. 24 is a perspective view showing an optical head device according to Embodiment 4, and the basic optical configuration is the same as that of FIG.
  • the configuration and operation of the optical head device will be described with reference to FIG. 24, but there are no special points or changes in the contents described in Embodiment 1 with reference to FIG. A description of the configuration and operation will be omitted.
  • the diffraction grating element 6 has the shape shown in FIG.
  • the light beam 2a emitted from the laser 1 (not shown) is split into a diffracted light beam 2bl-2b3.
  • FIG. 24 only the path of the zero-order diffracted light beam 2bl among the diffracted light beams is indicated by lines, and the ⁇ first-order diffracted light beams 2b2 and 2b3 are not illustrated. Therefore, in FIG. 24, the path of each light beam is indicated by a line substantially the same as the design optical axis.
  • a flat half mirror 120 arranged at an angle to the design optical axis Alb is used to convert the light beam 2bl—2b3 into the + z direction. And is incident on the objective lens 9.
  • the light beam 2d reflected by the optical disc information recording medium 8 re-enters the objective lens 9, is converted into convergent light having the optical axes Alb and Ale as central axes, and passes through the flat half mirror 120. I do.
  • the light beam 2e transmitted through the flat half mirror 120 passes through the detection optical element 121, becomes a light beam 2f, and enters the light detector 122.
  • the photodetector 122 has a light receiving surface pattern having at least a four-divided light receiving area pair having a light receiving area A-D force and light receiving areas E and F arranged on both sides thereof.
  • the light receiving areas A to D are divided into four by a dividing line substantially parallel to the X axis and a dividing line substantially parallel to the y axis.
  • each light receiving area receives the light beam 2f converted by the detecting optical element 121, it has a function of outputting an electric signal of a magnitude corresponding to the light amount.
  • Focus control is performed on the optical disc information recording medium 8 based on the focus error signal FES. This is performed by displacing the objective lens 9 in the z-axis direction so that the light beam 2d can be condensed at the same time. Specifically, the objective lens 9 is displaced in the z direction by an objective lens displacement mechanism (not shown) using an electromagnetic force generated by a coil or the like.
  • the condensing position of the light beam 2f can be set to an arbitrary distance.
  • the detection optical element 121 has an astigmatism generation function by making the entrance surface or the exit surface a curved surface or forming a hologram, and uses the astigmatism focusing method together with the flat type half mirror 120. It may be used to generate astigmatism of a size necessary for error detection. Further, the detection optical element 121 is generated by the flat-type half mirror 120 if the center axes of the entrance surface and the exit surface are relatively shifted or are arranged at an angle with respect to the design optical axis Ale.
  • Coma can be corrected, and can be used to prevent the light intensity distribution on the photodetector 122 from becoming asymmetric.
  • the detection optical element 121 is not an essential component of the optical head device. For example, when such a lens function, an astigmatism generation function, and a coma aberration correction are not performed, in order to reduce the number of components, the optical head device does not have the optical element 121 for detection. It doesn't matter.
  • the light receiving regions E and F are arranged substantially parallel to the tangential direction D 2, and respectively receive the + 1st-order diffracted light beam 2d2 and the 1st-order diffracted light beam 2d3 reflected by the optical disc information recording medium 8. Receive light.
  • the optical head device shown in FIG. 24 has an optical configuration that performs three-beam tracking error detection by using this. By subtracting output signals from the light receiving areas E and F, the three-beam tracking error is detected. A signal is generated, and based on the signal, the position of the light beam 2d in the radial direction is controlled so as to follow the displacement of the track.
  • the optical head device may use another method as long as it is a tracking error detection method similarly performed using the diffracted light beam 2dl-2d3.
  • a tracking error detection method similarly performed using the diffracted light beam 2dl-2d3.
  • the light receiving areas E and F are each formed as a light receiving surface pattern in which each of the light receiving areas E and F is divided at least into two in the y direction, tracking error detection by the differential push-pull method can be performed.
  • the position may be adjusted so as to be a predetermined initial target value instead of the calculated value SO!
  • the photodetector 122 When the photodetector 122 is arranged near the circle of least confusion as described above, the light beam 2f reflected by the optical disc information recording medium 8 and incident on the optical disc information recording medium 8 is affected by the effect of astigmatism. On 122, it is folded in the tangential D2 direction, which is almost 90 degrees, that is, in the y direction. Therefore, in the fourth embodiment, when the objective lens 9 moves in the radial direction D1, the light beam is shifted on the photodetector 122 in the y direction.
  • the light emitting component 5, the diffraction grating element 6, the flat plate half mirror 120, the detection optical element 121, and the light detector 122 are made of a metal such as a resin. Each is fixed to a powerful optical base and integrated.
  • three diffraction grating elements 6 are formed on track TR or guide groove GR on optical disc information recording medium 8 as described in the first embodiment. It is necessary to adjust the rotation of the diffraction grating element 6 so that the light beams 2dl-2d3 are arranged in a predetermined direction. Therefore, for example, a cylindrical diffraction grating element 6 having a cylindrical outer shape, or a cylindrical diffraction grating element holder indirectly holding the diffraction grating element 6 is fitted into a cylindrical hole provided in the optical base. Thus, the diffraction grating element 6 can be rotated about the ⁇ -axis (however, in FIG.
  • the outer shape of the diffraction grating element 6 is shown as a square instead of a cylinder in order to make the cylindrical surface easier to see).
  • the fixing method is not limited to the embodiment using the fitting structure as in the above example, but a structure in which the optical base and the diffraction grating element 6 or the diffraction grating element holder are fixed with an adhesive.
  • another mode such as fixing via a fixing member such as a panel panel or a screw may be used.
  • the structure involves rotation adjustment, in order to facilitate adjustment during rotation adjustment of the diffraction grating element 6, the diffraction grating element 6 and the optical base or the diffraction grating element holder and the optical Some gap is required between the base and the scientific base. Furthermore, since the diffraction grating element 6, the optical base and the holder for the diffraction grating element usually have an outer dimension tolerance of at least several tens of meters, gaps may be widened within this tolerance range.
  • the gap is filled with the adhesive, or the gap is fixed, and the gap is fixed.
  • a fixing member such as a screw-and-panel panel, it is limited.
  • the diffraction grating element 6 is pressed against the optical base and held at the contact point thus set.
  • FIG. 25 is a cross-sectional view of the cylindrical surface of the diffraction grating element 6 along the curvature direction (that is, the y-axis direction) at this time.
  • the light beam Since the angle of incidence on the entrance surface 101c of the central optical axis of 2a changes with respect to the initial incident angle, the central optical axis of the light beam 2b after passing through the diffraction grating element 6 is the designed optical axis Ala. Bla with inclination to.
  • a state where the central axis of the diffraction grating element 6 is located on the design optical axis Ala is represented as an outer shape 6a indicated by a dotted line.
  • the light beam 2f moves on the photodetector 122 accordingly.
  • the movement of the light beam 2f is a force that affects operations such as the focus error detection described above. The influence depends on the direction in which the light beam 2f on the detector 122 shifts.
  • the control operating point changes, and the light beam 2d is defocused on the optical disk information recording medium 8. Then, the recording / reproducing characteristics of the optical head device are deteriorated due to the influence of the defocus.
  • an optical configuration for minimizing the displacement of the light beam in the X direction is desirable.
  • the curvature direction of the cylindrical surface of diffraction grating element 6 is arranged so as to correspond to tangential direction D2, as shown in FIG. Even if is moved, the direction of displacement of the light beam 2f on the photodetector 122 can be limited to the y direction, and the above-described deterioration of the recording / reproducing characteristics of the optical head device can be suppressed.
  • the diffraction grating element 6 may have a shape shown in FIG. Also in this case, the direction of the light beam shift on the photodetector 122 caused by the movement of the position of the diffraction grating element 6 can be limited to the y direction, and the same effect as described above can be obtained.
  • the diffraction grating element 6 may have a shape shown in FIG. 15 or FIG.
  • the cylindrical surface has a curvature in the j8-axis direction, unlike the case of using the shape of FIG. 13 or FIG. 14 having a cylindrical surface curvature in the ⁇ -axis direction, it is caused by the position movement of the diffraction grating element 6.
  • the shift direction of the light beam on the light detector 122 is the X direction.
  • the displacement of the light beam in the X direction causes the deterioration of the recording and reproducing characteristics of the optical head device. Therefore, when the diffraction grating element 6 having the shape shown in FIG. 15 or FIG.
  • the diffraction grating is used, when the light beam is fixed using a fixing member or the like in order to suppress the occurrence of the displacement of the light beam in the X direction, the diffraction grating is used.
  • the element 6 is kept pressurized in the axial direction, that is, press-fitted against the optical base.
  • the position of the diffraction grating element 6 in the direction of curvature of the cylindrical surface of the diffraction grating element 6 that is, in the ⁇ -axis direction, which is usually set to the radial direction D1 due to rotation adjustment and time-dependent change of the diffraction grating element 6 is prevented. Can be suppressed.
  • This embodiment is a modification of the optical head device according to the first embodiment.
  • the curvature direction of the cylindrical surface of the diffraction grating element 6 is substantially radially changed.
  • the light beam on the light-receiving surface of the photodetector 10 shifts due to position fluctuations in a plane perpendicular to the design optical axis Ala of the diffraction grating element 6, and the recording and reproduction characteristics of the optical head device are It is intended to reduce deterioration.
  • FIG. 27 is a perspective view showing an optical head device according to the present embodiment, and the basic optical configuration is the same as FIG.
  • the configuration and operation of the optical head device will be described with reference to FIG. 27, but there are no special points V or changes to the contents described in Embodiment 1 with reference to FIG. The description of the configuration, operation, and the like is omitted.
  • the diffraction grating element 6 has the shape shown in FIG. 15, and splits the light beam 2a emitted from the semiconductor laser 1 (not shown) inside the light emitting component 5 into a diffracted light beam 2bl-2b3. I do.
  • FIG. 27 only the optical path of the 0th-order diffracted light beam 2bl among the diffracted light beams is indicated by lines, and the ⁇ 1st-order diffracted light beams 2b2 and 2b3 are not shown. Therefore, in FIG. 27, the path of each light beam is indicated by a line substantially the same as the design optical axis.
  • the deflecting prism 140 corresponds to the deflecting prism 7 shown in FIG. 1 of the first embodiment, and deflects the light beam 2bl-2b3 to make it incident on the objective lens 9.
  • the light beam 2d reflected by the optical disc information recording medium 8 again enters the objective lens 9, is converted into convergent light having the optical axes Alb and Ale as central axes, and passes through the deflecting prism 140.
  • the hologram element 141 has a function of dividing the light beam 2e transmitted through the deflecting prism 140 into four half light beams 2fl-2f4 in order to detect a spot size method focus error.
  • the condenser function of the condenser lens 142 may be included in the hologram element 141 and integrated.
  • the hologram element 141 has a concentric shape or a curved shape having different centers in two regions bounded by a line BL parallel to the tangential direction D2 of the optical disc information recording medium 8. As shown in FIG.
  • the half-flux beams 2fl and 2f2 diffracted in the holo-holum region 141a and transmitted through the condenser lens 142 converge at different focal lengths FC1 and FC2 (here, FCKFC2 force FC1 may be greater than FC2).
  • FCKFC2 force FC1 may be greater than FC2
  • the half beam beams 2f3 and 2f4 diffracted by the hologram region 141b and transmitted through the condenser lens 142 similarly converge to different focal lengths FC1 and FC2.
  • the focal lengths FC1 and FC2 are determined by the set value of the focus error detection range of the optical head device.
  • the + 1st-order diffracted light beam 2d2 and the 1st-order diffracted light beam 2d3 are similarly split into half-beam beams, and then pass through the condenser lens 142 and enter the photodetector 143.
  • the photodetector 143 includes four pairs of rectangular light-receiving areas divided into three by a dividing line parallel to at least the radial direction D1 (that is, corresponding to the x-axis direction). , Plb, Pic, and Pld, and light receiving areas A2—D2 and A3—D3 for receiving the half light beam generated by splitting the + 1st-order diffracted light beam 2d2 and the 1st-order diffracted light beam 2d3 by the holo-drum element 141, respectively.
  • the photodetector 143 is disposed at an intermediate distance between the focal lengths FC1 and FC2 of the half beam 2fl-2f4 (that is, in the vicinity of (FC1 + FC2) Z2), and as shown in FIG. Since the short-beam beam having a short distance is converged before the photodetector 143 and the power is spread again, the arcs of the outer shape of the half-beam beam are in the directions shown in FIG. 30, respectively.
  • the photodetector 143 shown in FIG. 30 is provided with a light receiving region or a light receiving region pair for each of the half-beam beams.
  • An embodiment having a light receiving surface pattern in which the region pairs are shared may be used.
  • FIG. 27 shows the optical configuration for performing the tracking error detection by the differential push-pull method
  • an embodiment in which the tracking error detection method using the three-beam method may be used.
  • the arrangement direction of the diffracted light beams 2dl-2d3 with respect to the track direction on the optical disc information recording medium 9 Is set to ⁇ a or ⁇ b.
  • the displacement of the light beam generated when the objective lens 9 moves in the radial direction has the least effect on the calculation of the focus error detection.
  • the direction of the dividing line of the pair of strip-shaped light receiving regions is set to the radial direction so as not to give.
  • the light beam in the y direction that is, the direction corresponding to the tangential direction D2 is used. It is desirable to have an optical configuration that minimizes the deviation of the system.
  • the curvature direction of the cylindrical surface of the diffraction grating element 6 is made to correspond to the radial direction D1 as shown in FIG. 27, the displacement of each light beam on the photodetector 143 caused by the position movement of the diffraction grating element 6
  • the direction can be limited to the X direction, and the deterioration of the recording / reproducing characteristics of the optical head device as described above can be suppressed.
  • the diffraction grating element 6 may have the shape shown in FIG. Also in this case, the direction of the light beam shift on the photodetector 143 caused by the movement of the position of the diffraction grating element 6 can be limited to the X direction, and the same effect as described above can be obtained.
  • the hologram element 141 has a function of splitting a half-beam beam at least in parallel to the X-axis direction corresponding to the radial direction D1, and each of the half-beam beams generated by the hologram element 141 is Alternatively, the light may be detected by the photodetector 143 having a light receiving pattern divided into two by a dividing line parallel to the X-axis direction corresponding to the radial direction.
  • the light receiving pattern having a dividing line parallel to the X-axis direction corresponding to the radial direction for each half-beam beam. Therefore, it is desirable to use an optical configuration that has as much likelihood as possible with respect to the displacement of the half-beam in the y direction, that is, the direction corresponding to the tangential direction D2. This can be realized by the method described above in 4.
  • the diffraction grating element 6 has a cylindrical surface curvature in the ⁇ -axis direction as the force diffraction grating element 6 held by the optical base in the same manner as described in the fourth embodiment.
  • the photodetector generated by the displacement of the diffraction grating element 6 is used.
  • the light beam shift direction on 143 is the y direction.
  • the present invention can be used for an apparatus that performs recording and reproduction on an information recording medium using a light beam, for example, a CD (Compact Disc), a DVD (Digital Versatile Disc), and an MD (Mini Disc) It can be applied to an optical disk recording / reproducing device that performs recording / reproduction via an optical disk information recording medium such as.
  • a CD Compact Disc
  • DVD Digital Versatile Disc
  • MD Mini Disc

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Head (AREA)
  • Moving Of The Head For Recording And Reproducing By Optical Means (AREA)

Abstract

L'invention concerne un dispositif à tête optique possédant une structure dans laquelle un faisceau lumineux divergent non parallèle est mis en incidence sur une lentille de focalisation, l'influence de l'aberration d'onde sur les caractéristiques d'enregistrement/reproduction étant supprimée même si la taille, l'épaisseur et le coût sont réduits. Un élément optique de diffraction (6) présente une fonction de diffraction, voire, par exemple, une fonction causant un astigmatisme annulant l'astigmatisme causé lorsque la source lumineuse est écartée de l'axe optique de la lentille de focalisation (9) dans un sens radial d'un support d'enregistrement d'informations (8) sous forme de disque optique. Plus particulièrement, la formation de la surface de diffraction ou de la surface arrière de l'élément optique de diffraction (6) en une surface torique ou cylindrique ainsi que le réglage de la courbure permettent de réguler le degré d'astigmatisme.
PCT/JP2004/013047 2004-01-09 2004-09-08 Dispositif a tete optique WO2005066947A1 (fr)

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CN117108944A (zh) * 2023-07-13 2023-11-24 荣谕科技(成都)有限公司 光源模组及显示装置

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63291219A (ja) * 1987-05-22 1988-11-29 Asahi Optical Co Ltd 光ピックアップの光学系
JPH0323528A (ja) * 1989-06-21 1991-01-31 Mitsubishi Electric Corp 光学ヘッド装置
JPH09259458A (ja) * 1996-03-22 1997-10-03 Sony Corp 光学装置及びこの光学装置を用いた光ピックアップ装置
JP2000182267A (ja) * 1998-12-11 2000-06-30 Tdk Corp 光記録再生装置
JP2002063731A (ja) * 2000-08-21 2002-02-28 Sony Corp 光学ピックアップ及びディスク装置
JP2003187488A (ja) * 2001-12-14 2003-07-04 Sharp Corp 光ピックアップ装置
JP2004005903A (ja) * 2002-03-29 2004-01-08 Matsushita Electric Ind Co Ltd 光ピックアップ装置および光ディスク装置

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63291219A (ja) * 1987-05-22 1988-11-29 Asahi Optical Co Ltd 光ピックアップの光学系
JPH0323528A (ja) * 1989-06-21 1991-01-31 Mitsubishi Electric Corp 光学ヘッド装置
JPH09259458A (ja) * 1996-03-22 1997-10-03 Sony Corp 光学装置及びこの光学装置を用いた光ピックアップ装置
JP2000182267A (ja) * 1998-12-11 2000-06-30 Tdk Corp 光記録再生装置
JP2002063731A (ja) * 2000-08-21 2002-02-28 Sony Corp 光学ピックアップ及びディスク装置
JP2003187488A (ja) * 2001-12-14 2003-07-04 Sharp Corp 光ピックアップ装置
JP2004005903A (ja) * 2002-03-29 2004-01-08 Matsushita Electric Ind Co Ltd 光ピックアップ装置および光ディスク装置

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JPWO2005066947A1 (ja) 2007-07-26
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TW200523912A (en) 2005-07-16

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