WO2005027109A1 - 対物レンズ、光ピックアップ及び光情報処理装置 - Google Patents
対物レンズ、光ピックアップ及び光情報処理装置 Download PDFInfo
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- WO2005027109A1 WO2005027109A1 PCT/JP2004/011934 JP2004011934W WO2005027109A1 WO 2005027109 A1 WO2005027109 A1 WO 2005027109A1 JP 2004011934 W JP2004011934 W JP 2004011934W WO 2005027109 A1 WO2005027109 A1 WO 2005027109A1
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- Prior art keywords
- objective lens
- recording medium
- light
- optical recording
- optical
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Classifications
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—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
- G11B7/095—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 specially adapted for discs, e.g. for compensation of eccentricity or wobble
- G11B7/0956—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 specially adapted for discs, e.g. for compensation of eccentricity or wobble to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
- G11B7/127—Lasers; Multiple laser arrays
- G11B7/1275—Two or more lasers having different wavelengths
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1372—Lenses
- G11B7/1374—Objective lenses
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1392—Means for controlling the beam wavefront, e.g. for correction of aberration
- G11B7/13925—Means for controlling the beam wavefront, e.g. for correction of aberration active, e.g. controlled by electrical or mechanical means
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B2007/0003—Recording, reproducing or erasing systems characterised by the structure or type of the carrier
- G11B2007/0006—Recording, reproducing or erasing systems characterised by the structure or type of the carrier adapted for scanning different types of carrier, e.g. CD & DVD
Definitions
- the present invention relates to an objective lens, an optical pickup, and an optical information processing device.
- Optical recording media such as a CD with a recording capacity of 0.65 GB and a DVD with a recording capacity of 4.7 GB are becoming widespread as means for storing video information, audio information, or data on a computer.
- Optical recording media such as a CD with a recording capacity of 0.65 GB and a DVD with a recording capacity of 4.7 GB are becoming widespread as means for storing video information, audio information, or data on a computer.
- Means for increasing the recording density of such an optical recording medium include increasing the numerical aperture (NA) of an objective lens in an optical pickup for writing or retrieving information on the optical recording medium, or By shortening the wavelength of the light source, it is effective to reduce the diameter of the beam spot converged by the objective lens and formed on the optical recording medium.
- NA numerical aperture
- the “CD optical recording medium” while the numerical aperture of the objective lens is 0.45 to 0.50 and the wavelength of the light source is approximately 785 nm, the “CD optical recording medium” In the “DVD-based optical recording medium”, which has a higher recording density than the “medium”, the numerical aperture of the objective lens is 0.60-0.65, and the wavelength of the light source is approximately 660 nm. As described above, it is desired that the optical recording medium further increase the recording density and increase the capacity. To this end, the numerical aperture of the objective lens is set to be larger than 0.65 or the light source It is desired to make the wavelength of 660nm shorter than 660nm.
- Patent Document 1 Japanese Patent Application Laid-Open No. 2002-107617
- the simplest method is to mount a conventional optical pickup and an optical pickup of an optical pickup for a new standard. There is a way to do that. However, it is difficult to achieve size reduction and cost reduction by this method. Disclosure of the Invention Problems to be Solved by the Invention
- a blue-based (large-capacity) optical recording medium using a light source in a blue wavelength band and an optical pickup compatible with existing DVDs or CDs are required.
- each light source having a different wavelength from each of the blue light source 100, the DVD light source 101, and the CD light source 102, and the light emitted from each of these light sources 100, 101, 102 are transmitted to a predetermined optical recording medium. It can be said that a configuration having a single objective lens 104 for converging and irradiating 103 is desirable.
- Patent Document 1 discloses the amount of aberration that occurs when an objective lens 110 designed at a light source wavelength of 405 ⁇ m as shown in FIG. 27 is used in a wavelength range of 400 to 800 nm (FIG. 28).
- 111 is an optical recording medium.
- the wavefront aberration generally needs to be about 0.07 rms or less.
- the wavelength is about 0.20 ⁇ rms near the wavelength of 660 nm and 785 nm used in DVD and CD systems.
- FIG. 29 shows the relationship between the object distance at a wavelength of 660 nm and the wavefront aberration for the objective lens 110 of FIG. A position with an object distance of 142 mm that minimizes the wavefront aberration may be selected.
- Another problem is that if the numerical aperture of the objective lens is made larger or the wavelength of the light source is made shorter, the coma caused by the tilt of the optical recording medium becomes larger. When coma aberration occurs, the spot formed on the information recording surface of the optical recording medium deteriorates, so that a normal recording / reproducing operation cannot be performed. Coma caused by tilt of an optical recording medium is generally given by the following equation.
- W ((n 2 -l) / (2n)) X (d X NA X ⁇ / ⁇ )
- ⁇ is the refractive index of the transparent substrate of the optical recording medium
- d is the thickness of the transparent substrate
- NA is the numerical aperture of the objective lens
- ⁇ is the wavelength of the light source
- ⁇ is the amount of tilt of the optical recording medium. From this equation, it can be seen that the shorter the wavelength and the higher the wavelength, the greater the aberration.
- an optical pickup or a carriage unit for moving the optical pickup is tilted so that the optical axis of the optical pickup is optically recorded.
- the optical recording medium is maintained substantially perpendicular to the medium, and the tilt of the optical recording medium is substantially optically corrected.
- the tilt correction operation is poor because the tilt target is large and heavy. There is a problem that it is difficult to tilt the optical pickup or the carriage at high speed. Further, since a mechanism for tilting the optical pickup or the carriage is required, there is a problem that the optical pickup or the carriage becomes heavy and high-speed access becomes difficult.
- a lens tilt actuator is provided, and a large-capacity light is provided.
- the optical system of the conventional medium it is assumed that the optical system of the conventional medium is used, or even a finite system is used.
- the tilt correction mechanism is not used in the CD generation and can tolerate coma, but the DVD generation is generally installed.
- FIGS. 30 (a) and 30 (b) show how coma aberration occurs when the objective lens 110 shown in FIG. 27 is tilted, and how coma aberration occurs when the optical recording medium 111 is tilted. In the cases shown in FIGS. 30A and 30B, coma aberration can be canceled by making the optical recording medium 111 and the objective lens 110 parallel. This is shown in Figure 30 (c).
- FIGS. 31 (a) and 31 (b) show how coma aberration occurs when the medium is tilted. From FIG. 31 (b), it can be seen that coma does not occur even if the objective lens 110 is tilted. In such a case, there is a problem that the coma caused by the inclination of the optical recording medium 111 in FIG. 31B cannot be corrected even if the objective lens 110 is shaken. This is shown in Figure 31 (b).
- the present invention when coma aberration correction is performed on a plurality of optical recording media having different wavelengths or substrate thicknesses while driving the lens tilt, favorable spot characteristics can be obtained for any of the optical recording media.
- the task is to be able to obtain
- the present invention uses an objective lens that satisfies a general sine condition when performing coma aberration correction by disc tilt while driving a lens tilt for a plurality of optical recording media having different wavelengths or substrate thicknesses.
- an object is to obtain good spot characteristics for any optical recording medium.
- the invention according to claim 1 is an objective lens for converging and irradiating light from a light source having a wavelength ⁇ ⁇ , 22 ( ⁇ 1 ⁇ 2) onto an optical recording medium through first and second substrates, respectively.
- the invention according to claim 4 is a method for transmitting light from a light source having a wavelength ⁇ , ⁇ 2, ⁇ 3 ( ⁇ 1 ⁇ 2 ⁇ 3) onto an optical recording medium through the first, second, and third substrates, respectively.
- an optical information processing apparatus that performs recording and reproduction in three generations of blue ZDVDZCD, two generations of blue ZDVD, or two generations of blue / CD is mainly applied.
- a wavefront aberration of 0.07 rms or less (referred to as Marshall criterion) at each wavelength.
- the actual amount of tilt of the optical recording medium that can occur varies depending on the type of optical recording medium. Around 0.5 deg for blue optical recording media, about 0.6 deg for DVD optical recording media, and 0 deg for CD optical recording media. It is necessary to expect about 9deg.
- r2 is the radius of curvature of the second surface of the objective lens
- rl is the radius of curvature of the first surface of the objective lens
- “Lens 1” in FIG. 1 is a so-called conventional lens shown in FIG. 27 in which the sine condition has been corrected.
- Coma aberrations generated when the blue optical recording medium, DVD optical recording medium, and CD optical recording medium are tilted by 1deg are about 0.22 ⁇ rms, 0.14 ⁇ rms, and 0.09 ⁇ rms, respectively.
- CDx (x l, 2, 3); each least-square error value of the third-order coma aberration component generated per unit angle when the substrate of the optical recording medium is tilted (unit: ⁇ rms)
- the invention according to claim 2 is the object lens according to claim 1, wherein the conditions (1) and (2) are such that the light from the light source having the wavelength ⁇ 1 is an incident light flux of an infinite system. For light from the light source of the wavelength ⁇ 2, it is specified for a finite incident light beam.
- the invention according to claim 3 is the objective lens according to claim 1 or 2, wherein the condition (1) is satisfied.
- (2) is defined for an incident light beam in the blue wavelength band as the wavelength 1 and in the red wavelength band as the wavelength ⁇ 2.
- the invention according to claim 5 is the object lens according to claim 4, wherein the conditions (3), (4), and (5) are satisfied with respect to light from the light sources having the wavelengths ⁇ 1 and ⁇ 2.
- the conditions (3), (4), and (5) are satisfied with respect to light from the light sources having the wavelengths ⁇ 1 and ⁇ 2.
- ⁇ 1 and ⁇ 2 are defined for an incident light beam of an infinite system, and are specified for an incident light beam of a finite system for light from the light source having the wavelength ⁇ 3.
- the invention according to claim 6 is the object lens according to claim 4, wherein the conditions (3), (4), and (5) are infinite for light from the light source having the wavelength; It is defined for the incident light flux of the system, and for the light from the light sources of the wavelengths ⁇ 2 and ⁇ 3, it is defined for the incident light flux of the finite system. [0030] Therefore, the invention described in claim 5 or 6 can be compatible with wavelengths ⁇ , 2, and 3.
- the invention according to claim 7 is the objective lens according to any one of claims 4 to 6, wherein the conditions (3), (4), and (5) are as follows:
- the wavelength ⁇ 2 is defined for the incident light beam in the red wavelength band and the wavelength ⁇ 3 is defined in the infrared wavelength band.
- the objective lens of these inventions is used with a finite incident light beam for long wavelength light.
- the objective lens of these inventions When used as an infinite objective lens in the blue wavelength band under the operating conditions of DVD and CD under the conditions of substrate thickness, differences in substrate thickness (0.6 mm, 0.6 mm, 1.2 mm) and differences in wavelength ( 405 nm, 660 nm, 785 nm).
- substrate thickness 0.6 mm, 0.6 mm, 1.2 mm
- wavelength 405 nm, 660 nm, 785 nm.
- correction can be made by making the luminous flux incident on the objective lens divergent light. That is, when recording, reproducing, or erasing a DVD or CD, use it as a finite objective lens.
- the invention according to claim 8 is the objective lens according to claim 1 or 4, wherein at least one surface is formed as a single lens having an aspherical surface by glass molding or resin molding.
- the invention according to claim 9 is the object lens according to claim 8, wherein rl is a radius of curvature of the objective lens on the light source side, and r2 is a radius of curvature of the objective lens on the optical recording medium side. r2 + rl) / (r2-rl) ⁇ 0.7.
- the invention according to claim 10 is the objective lens according to claim 1 or 4, which is a two-unit bonded objective lens.
- the invention according to claim 11 is the objective lens according to claim 8, wherein at least one surface has a diffraction surface or a phase step surface.
- At least one surface has a diffraction surface or a phase step surface.
- the optical axis of the objective lens is inclined with respect to the incident light beam.
- an optical pickup according to a fourteenth aspect of the present invention provides a plurality of light sources that emit light of wavelengths ⁇ ⁇ , 12, and 3, and convergent irradiation of light from these light sources onto an optical recording medium. And when the light source that satisfies at least two of the conditions (1), (2) and (3) is turned on, the optical axis of the objective lens with respect to the incident light beam. To make it tilt.
- the invention according to claim 15 is the optical pickup according to claim 13 or 14, wherein the objective lens tilts the objective lens in at least one of a radial direction and a rotation direction of the optical recording medium. It is mounted on the drive unit.
- An invention according to claim 16 is the optical pickup according to claim 14, wherein a relative angle between the optical recording medium and the objective lens, a relative angle between the optical recording medium and a predetermined reference surface of the optical pickup, An angle detecting means for detecting at least two or more of a relative angle between a lens and the predetermined reference surface of the optical pickup is provided.
- a correction means for giving a predetermined gain or offset to the relative angle signal detected by the angle detection means in accordance with a lighting light source Is provided.
- a coma aberration amount detecting means for detecting a coma amount generated according to a relative angle between the objective lens and the optical recording medium is provided.
- the optical pickup according to the nineteenth aspect of the present invention is the optical pickup according to the first aspect, wherein a plurality of light sources that emit light of wavelengths ⁇ 1 and ⁇ 2 and light from these light sources is convergently irradiated onto an optical recording medium.
- a lens an optical system for forming an infinite incident light beam with respect to the objective lens for each of the two wavelengths ⁇ 1 and ⁇ 2, and the objective lens, (2)
- the objective lens is tilted in at least one of the radial direction and the rotation direction of the optical recording medium so that the optical axis of the objective lens is tilted with respect to the incident light beam.
- a lens driving device When the light source that satisfies both of the conditions (2) is turned on, the objective lens is tilted in at least one of the radial direction and the rotation direction of the optical recording medium so that the optical axis of the objective lens is tilted with respect to the incident light beam.
- the objective lens has substantially the same numerical aperture on the optical recording medium side at the two wavelengths ⁇ 1 and ⁇ 2.
- a common aperture element for making the diameters of the light beams of the two wavelengths ⁇ ⁇ and ⁇ 2 incident on the objective lens substantially equal to each other. On the optical path between the light source and the objective lens.
- the objective lens and the two wavelength light beams for the optical recording medium having substantially the same substrate thickness form an infinite-system incident light beam with respect to the objective lens, respectively, and the above-described light beam with respect to the remaining wavelength light.
- an optical system that forms a finite system incident light beam with respect to the objective lens and a light source that satisfies at least two of the conditions (1), (2), and (3) are turned on, the optical axis of the objective lens is changed to the incident light beam.
- the optical pickup according to the twenty-third aspect of the present invention is the optical pickup according to the twenty-third aspect, wherein a plurality of light sources emitting light of wavelengths ⁇ 1, 12, and ⁇ 3, and light from these light sources is convergently irradiated onto an optical recording medium.
- the objective lens described above and two wavelength lights having substantially the same numerical aperture on the optical recording medium side each form an infinite incident light beam with respect to the objective lens described above, and the other wavelength lights do not.
- the optical system that forms a finite system incident light beam with respect to the objective lens and a light source that satisfies at least two of the conditions (1), (2), and (3) are turned on, the optical axis of the objective lens is changed to the incident light beam.
- a lens driving device for tilting the objective lens in at least one of a radial direction and a rotation direction of the optical recording medium so as to tilt the optical axis of the objective lens with respect to an incident light beam so as to tilt the objective lens with respect to the incident light beam.
- the invention according to claim 24 is the optical pickup according to claim 23, wherein the two light beams having substantially the same numerical aperture on the optical recording medium side have substantially equal diameters of light beams incident on the objective lens. Is provided on the optical path between the light source and the objective lens.
- the invention according to claim 25 is the optical pickup according to any one of claims 19, 22 and 23, wherein the objective lens satisfies the sine condition when the light having the shortest wavelength; It is optimally designed to help you.
- the invention according to claim 26 is the optical pickup according to claim 20, wherein the wavelength ⁇ 1 is approximately equal to the wavelength ⁇ 1.
- the invention according to claim 27 is the optical pickup according to claim 22 or 23, wherein the wavelength ⁇ 1 is approximately 405 nm, the wavelength ⁇ 2 is approximately 660 nm, and the wavelength ⁇ 3 is approximately 785 nm.
- the substrate thickness is approximately 0.6 mm, the third substrate thickness is 1.2 mm, the numerical aperture on the optical recording medium side of the objective lens at the two wavelengths ⁇ and ⁇ 2 is 0.6-0.7, and the remaining wavelengths; In 13, the numerical aperture of the objective lens on the optical recording medium side is 0.45-0.55.
- the objective lens When the light source that satisfies the above condition is turned on, the objective lens is held at a predetermined position. When the light source that is not satisfied is turned on, the objective lens is used with the optical axis inclined with respect to the incident light beam.
- the least-squares error value (unit: ⁇ rms) of the third-order coma aberration component generated per unit angle is
- phase correction unit is provided between the light source and the objective lens.
- the coma due to the tilt of the optical recording medium cannot be corrected even if the lens is tilted. Therefore, when the light source satisfies the condition, the lens tilt of the objective lens is held, or A liquid crystal or the like may be used in combination as another coma aberration correcting means.
- the invention according to claim 31 is the optical pickup according to claim 13, 14, 19, 22, 23, or 28, wherein the light having the wavelengths ⁇ 1 and ⁇ 2
- the substrate thickness of the optical recording medium to be used is substantially the same.
- the invention according to claim 32 is the optical pickup according to any one of claims 13, 14, 19, 22, 23, 28, and 30, wherein the light having the wavelengths ⁇ 1 and ⁇ 2 is The substrate thickness of the optical recording medium used for the light is approximately the same, and the substrate thickness of the optical recording medium used for the light of the wavelength ⁇ 3 is the optical recording medium used for the ⁇ 1 and ⁇ 2. About twice the substrate thickness of
- An optical information processing apparatus is an optical pickup provided with the objective lens according to claim 1 or 4, or the optical information processing apparatus according to claims 13, 14, 19, 22, 23, 28, 30. Information is recorded, reproduced, or erased on the optical recording medium using an optical pickup described in any one of the above.
- a good spot can be obtained for any of the optical recording media. Properties can be obtained.
- a plurality of optical recording media having different wavelengths or different substrate thicknesses can be used. Then, when performing coma aberration correction by disc tilt while driving the lens tilt, it is possible to obtain good spot characteristics for any optical recording medium using an objective lens satisfying a general sine condition. it can.
- FIG. 1 is a characteristic diagram showing coma aberration generated at a lens tilt of 1 deg of an objective lens as a feature of the present invention.
- FIG. 2 is an explanatory view showing a first embodiment of an objective lens.
- FIG. 3 is a characteristic diagram of disc tilt, lens tilt, tilt correction, and lens tilt amount with respect to a blue optical recording medium in the present embodiment.
- FIG. 4 is a characteristic diagram of disc tilt, lens tilt, tilt correction, and lens tilt amount for a DVD-based optical recording medium according to the present embodiment.
- FIG. 9 is a characteristic diagram of tilt correction and lens tilt amount.
- FIG. 6 is an explanatory view showing a second embodiment of the objective lens.
- FIG. 7 is a characteristic diagram of disc tilt, lens tilt, tilt correction, and lens tilt amount for a blue optical recording medium according to the present embodiment.
- FIG. 8 is a characteristic diagram of disc tilt, lens tilt, tilt correction, and lens tilt amount for a DVD-based optical recording medium according to the present embodiment.
- FIG. 9 is a characteristic diagram of tilt correction and lens tilt amount.
- FIG. 11 is a characteristic diagram of disc tilt, lens tilt, tilt correction, and lens tilt amount with respect to a blue optical recording medium in the present embodiment.
- FIG. 12 is a characteristic diagram of disc tilt, lens tilt, tilt correction, and lens tilt amount for a DVD-based optical recording medium according to the present embodiment.
- FIG. 13 is a characteristic diagram of disc tilt, lens tilt, and tilt correction for a CD-based optical recording medium in the present embodiment.
- FIG. 14 is a schematic overall configuration diagram showing a first embodiment of an optical pickup.
- FIG. 15 is a configuration diagram showing details of the fixed optical system.
- FIG. 16 is a schematic perspective view showing a configuration example of the actuator section.
- FIG. 17 is a schematic diagram showing a configuration example of a tilt detection optical system.
- FIG. 18 is a schematic circuit diagram showing a circuit configuration example for calculating a tilt signal.
- FIG. 19 is a front view showing a configuration example of a light receiving element for a 4-axis actuator.
- FIG. 20 is an explanatory diagram showing a relationship between an optical recording medium and an interference area.
- FIG. 21 is an explanatory diagram relating to an interference region.
- FIG. 22 is an explanatory diagram showing how an interference area changes with radial tilt.
- FIG. 23 is an explanatory diagram showing how an interference area changes with a tangential tilt.
- FIG. 24 is a front view showing a pattern configuration example of a light receiving element.
- FIG. 25 is a schematic perspective view showing an embodiment of the optical information processing device.
- FIG. 26 is a block diagram of a blue / DVDZCD compatible optical pickup generally assumed.
- FIG. 27 is a configuration diagram showing a conventional example of an objective lens.
- FIG. 28 is a graph showing a conventional light source wavelength-wavefront aberration characteristic.
- FIG. 29 is a characteristic diagram of a conventional disc tilt, lens tilt, and nose correction for a blue optical recording medium.
- FIG. 30 is a characteristic diagram of disc tilt, lens tilt, and tilt correction for a conventional DVD-based optical recording medium.
- FIG. 31 is a characteristic diagram of a conventional disc tilt, lens tilt, and nose correction for a CD-based optical recording medium.
- FIG. 32 is a configuration diagram showing a second embodiment of the optical pickup.
- FIG. 33 is a front view showing a configuration example of the hologram unit.
- FIG. 34 is a characteristic diagram of disc tilt, lens tilt, and tilt correction of a DVD infinite system.
- FIG. 35 is a configuration diagram showing a third embodiment of the optical pickup.
- a blue optical recording medium having a wavelength of ⁇ l; 405 nm, a substrate thickness of 0.6 mm, a numerical aperture NA of 0.65, a working wavelength of 2; 660 nm, a substrate thickness of 0.6 mm, DVD-type optical recording media with a numerical aperture of NA: 0.65 and three types of optical recording media: CD-based optical recording media with a working wavelength of 3; 785 nm, substrate thickness: 1.2 mm, and a numerical aperture of NA: 0.50
- the present invention relates to an objective lens used for an optical pickup for performing recording, reproduction, or erasing. First, FIG.
- the objective lens 2A has a numerical aperture NA of 0.65, a focal length f of 3.05 mm, a refractive index of d-line nd; l.50, Abbe woman v d; ffl Review
- the aspherical surface of the lens surface has coordinates in the optical axis direction; X, coordinates in the orthogonal direction to the optical axis; Y, paraxial radius of curvature; K, higher order coefficients; A, ⁇ , C, D, ⁇ , F,..., using the following well-known aspheric formula:
- the shape is specified by giving R, K, A, B, C, D, ....
- Table 1 (a) shows specific data.
- the symbols in the table are as follows.
- “OBJ” means the object point (semiconductor laser as a light source), while the objective lens 2A is “infinite”, and the radius of curvature; RDY and thickness; “INFINITY” of THI means that the light source is Meaning at infinity.
- “ST ⁇ ” is the entrance pupil plane, the radius of curvature is “INFINITY”, and the thickness is “0” by design.
- the unit of the quantity having the length dimension is "mm”.
- S2 means "the side of the light source” of the objective lens 2A
- S3 means "the side of the optical recording medium”.
- the thickness of the objective lens 2A is 1.85 mm, and the thickness described in “Right to the radius of curvature” in the column of S3; 1.694869 mm indicates “working distance”.
- S4 is the light source side surface of the light irradiation side substrate of the optical recording medium 1
- IMG is the surface that matches the recording surface. The distance between these surfaces S4 and IMG, that is, the light irradiation side substrate thickness is 0.6. mm, n; l.62.
- EPD entrance pupil diameter
- WL width
- W width
- the minimum two of the third-order coma components generated per angle Error value (unit: rms)
- a case where the present invention is applied to a DVD-based optical recording medium lb having a working wavelength of 660 nm will be described with reference to FIG. 2B and Table 1B.
- the shape of the objective lens 2A is the same as in the case of FIG. 2 (a) and Table 1 (a) except for the power refractive index and the working distance.
- a DVD-based optical recording medium lb is used with finite system incidence, and a single aperture on the first surface “ST ⁇ ” from the object point “ ⁇ BJ” (semiconductor laser as a light source).
- the distance to the part is 410mm. This is a value selected so that the wavefront aberration is minimized.
- a case where the present invention is applied to a CD-based optical recording medium lc having a wavelength of 785 nm will be described with reference to FIG. 2 (c) and Table 1 (c).
- the shape of the objective lens 2A is the same as that of FIG. 2 (a) and Table 1 (a), but the refractive index, working distance, and thickness of the light irradiation side substrate are different.
- a CD-based optical recording medium lc is used with a finite system incidence, and the object point “ ⁇ BJ” (semiconductor laser as a light source) to a single opening on the first surface “STO”
- the distance is 75. Omm. This is a value selected so that the wavefront aberration is minimized as in the case of the DVD system.
- FIGS. 3 (a) and (b), FIGS. 4 (a) and (b), and FIGS. 5 (a) and (b) show a blue optical recording medium using the objective lens of the present embodiment (Example 1).
- This section shows the aberration characteristics due to the tilt of the optical recording medium and the aberration characteristics due to the lens nose that occur when the DVD-based optical recording medium and the CD-based optical recording medium are used at a predetermined wavelength.
- FIGS. 3 (c), 4 (c) and 5 (c) show aberration characteristics when the coma due to the tilt of the optical recording medium is corrected by the lens tilt. It can be seen that the correction was good at all wavelengths.
- FIGS. 3 (d), 4 (d), and 5 (d) show lens drive amounts required for the objective lens to correct the tilt of the optical recording medium.
- the objective lens should be tilted by 0.8deg in the opposite direction.
- the DVD optical recording medium is tilted by 1deg
- the objective lens should be tilted by 0.6deg in the opposite direction.
- the objective lens may be tilted by 0.6 degrees in the opposite direction.
- a blue optical recording medium la having a wavelength ⁇ l of 405 nm, a substrate thickness of 0.6 mm, a numerical aperture NA of 0.70, a wavelength of 2 660 nm, a substrate thickness of 0.6 mm, DVD-type optical recording medium 1b with numerical aperture NA; 0.65, and 3 kinds of optical recording with CD-type optical recording medium lc with operating wavelength 3; 785nm, substrate thickness: 1.2mm, numerical aperture NA: 0.50
- the present invention relates to an objective lens 2B used for an optical pickup for recording, reproducing, or erasing a medium.
- the objective lens 2B of the present embodiment uses a focal length f of 3.05 mm, a refractive index of d-line nd of 1.55, and Abbe vd; Reply
- the ⁇ M objective lens 2B is used in the infinite system for the blue optical recording medium la as in the case of the first embodiment, and is used for the DVD optical recording medium lb and the CD optical recording medium.
- lc is a lens used in a limited system.
- Fig. 6 (a) and Table 2 (a) show the configuration used for the blue optical recording medium la
- Figs. 6 (b) and 2 (b) show the configuration used for the DVD optical recording medium lb
- Figure 6 (c) and Table 2 (c) show the configuration used for the CD-based optical recording medium lc.
- the aspherical shape of the objective lens 2B and the items described in Table 2 are the same as those in the first embodiment.
- the least squares error value (unit: rms) of the third-order coma aberration component generated per unit angle when tilted, CLx (x l, 2, 3);
- the least-square error value (unit: rms) of the third-order coma aberration component generated per unit angle when the objective lens is tilted
- FIGS. 7 (a) and (b), FIGS. 8 (a) and (b), and FIGS. 9 (a) and (b) show a blue optical recording medium using the objective lens of the present embodiment (Example 2).
- This figure shows the aberration characteristics due to lens tilt and the aberration characteristics due to tilt of the optical recording medium that occur when DVD optical recording media and CD optical recording media are used at a predetermined wavelength.
- FIGS. 7 (c), 8 (c) and 9 (c) are aberration characteristic diagrams when the coma due to the tilt of the optical recording medium is corrected by the lens tilt. Correction was successfully performed for all wavelengths.
- FIGS. 7 (d), 8 (d), and 9 (d) show the lens drive amount required for the objective lens for correcting the tilt of the optical recording medium.
- a blue optical recording medium la having a wavelength of 1; 405 nm, a substrate thickness of 0.6 mm, a numerical aperture NA of 0.65, a wavelength of 2; 660 nm, a substrate thickness of 0.6 mm, an aperture of 0.6 mm, DVD-type optical recording medium 1b with a numerical aperture of 0.65, and wavelength of 3; 785nm, substrate thickness; 1.2mm, CD-type optical recording medium with a numerical aperture of NA: 0.50
- the present invention relates to an objective lens 2C used for an optical pickup that performs recording, reproduction, or erasing.
- the objective lens 2C of the present embodiment is different from the objective lenses of the first and second embodiments (Examples 1 and 2) in that a single-lens objective lens and a two-unit bonded type lens are used.
- the point is to use an objective lens.
- chromatic aberration can be reduced by bonding a lens having a positive refractive power and a lens having a negative refractive power to each other. Chromatic aberration is corrected over the band.
- the focal length is f; 2.5 mm, and HOYA glass materials LAC8 and EFD8 are bonded to the light source side and optical recording medium side, respectively.
- the objective lens 2C of the present embodiment is used in an infinite system for the blue optical recording medium la, as in the first embodiment, and is used for the DVD optical recording medium lb and the CD optical recording medium.
- medium lc is the lens used in the finite system.
- Fig. 10 (a) and Table 3 (a) show the configuration used for the blue optical recording medium la
- Fig. 10 (b) and Table 3 (b) show the configuration used for the DVD optical recording medium 1b
- Fig. 10 (c) and Table 3 (c) show the configuration used for the CD-based optical recording medium lc.
- the aspherical shape of the objective lens 2C and the items described in Table 3 are the same as those in the first embodiment.
- the least squares error value (unit: rms) of the third-order coma aberration component generated per unit angle when tilted, CLx (x l, 2, 3);
- the least-square error value (unit: rms) of the third-order coma aberration component generated per unit angle when the objective lens is tilted
- EPD Injection diameter (mm) 2.76
- FIGS. 11 (a), (b), 012 (a), (b), and l3 (a), (b) show a blue optical recording medium and a DVD using the objective lens of the present embodiment (Example 3). It shows the aberration characteristics due to lens tilt and the aberration characteristics due to tilt of the optical recording medium, which occur when a system optical recording medium and CD system optical recording medium are used with a predetermined wavelength.
- FIGS. 11 (c), 12 (c) and 13 (c) show aberration characteristics when the coma due to the tilt of the optical recording medium is corrected by the lens tilt. It can be seen that blue and DVD were corrected well. On the other hand, there is almost no correction effect for CDs.
- FIGS. 11D and 12D show the amount of lens drive required for the objective lens to correct the tilt of the optical recording medium.
- a method may be employed in which the lens is fixed at a predetermined position without tilting.
- phase correcting means may be used in combination for coma (I CLx / CDx I 1 1) which cannot be corrected by lens tilt.
- phase correcting means a means for performing phase correction such as liquid crystal is provided so that it cannot be corrected by lens tilt. What is necessary is just to give by a liquid crystal.
- a double-sided aspherical single-lens objective lens is used in the first and second embodiments.
- a bonded double-sided aspherical objective lens is used in the third embodiment.
- an aspherical surface may be an objective lens used for only one surface.
- a diffraction surface or a phase step surface may be provided on the surface of the objective lens. This increases the degree of freedom, making it easier to ensure performance. It is also possible to select a shape such that these diffraction surfaces and phase steps act only on a specific wavelength, for example, a wavelength of 660 nm. Also, the order of the diffraction plane can be arbitrarily selected.
- FIG. 14 is a schematic diagram showing a configuration example of an optical pickup capable of recording, reproducing, and erasing data on an optical recording medium.
- the light from the fixed optical system 3 is condensed on the optical recording medium 1 by the objective lens 2, and the reflected light from the optical recording medium 1 is transmitted from a detection system (not shown) arranged in the fixed optical system 3.
- the recording and reproduction of information are performed based on the signal of.
- an actuator section 4 as a lens driving device for tilting the objective lens 2 and a tilt detection section 5 for detecting the tilt of the optical recording medium 1 are provided.
- the actuator section 4 is tilted in accordance with the detected tilt amount, and is controlled so that the optical axis of the objective lens 2 is always at a predetermined angle with respect to the surface of the optical recording medium 1.
- FIG. 15 is a schematic block diagram illustrating a configuration example of the fixed optical system 3 according to the present embodiment.
- An optical pickup capable of recording, reproducing, or erasing each of the CD-based optical recording media lc with a light irradiation side substrate thickness of 1.2 mm.
- the optical pickup 11 of the present embodiment includes a semiconductor laser (light source) 12, a collimator lens 15, a polarizing beam splitter 16, dichroic prisms 17, 18, a deflection prism 19, a 1Z4 wavelength plate 20, , Aperture 21, aperture switching means 22, objective lens 2 (lenses as described in the first to third embodiments relating to the above-described objective lens), detection lens 23, light beam splitting means 24, light receiving A blue optical system 26 composed of an element 25 through which light in the blue wavelength band passes, a hologram unit 27, a coupling lens 28, a dichroic prism 17, 18, a deflecting prism 19, a 1Z4 wavelength plate 20, an aperture 21, Aperture switching means 22, objective lens 2A force DVD-based red optical system through which light in the red wavelength band is composed 29 And a hologram unit 30, a coupling lens 31, a dichroic prism 18, a deflection prism 19, a quarter-wave plate 20, an aperture 21, an aperture switching means 22, and an infrared wavelength band light composed of an
- the hologram unit 27 is formed by integrating the chip of the semiconductor laser (light source) 13, the hologram 33, and the light receiving element 34.
- the hologram unit 30 is formed by integrating a chip of a semiconductor laser (light source) 14, a hologram 35, and a light receiving element 36.
- the optical recording media la, lb, and lc are optical recording media that use different wavelengths
- the optical recording medium la is a blue-based optical recording medium having a substrate thickness of 0.6 mm, and an optical recording medium.
- lb is a DVD optical recording medium with a substrate thickness of 0.6 mm
- optical recording medium lc is a CD optical recording medium with a substrate thickness of 1.2 mm.
- a rotating mechanism not shown
- the opening 21 can be restricted on a bobbin holding the objective lens 2 on an actuator unit 4 that moves the objective lens 2 in the focus direction and the track direction. No need to use parts.
- the light reflected by the optical recording medium la becomes circularly polarized light in the opposite direction to the outward path, becomes substantially parallel light again, passes through the quarter-wave plate 20, becomes linearly polarized light orthogonal to the outward path, and is deflected.
- Prism 19 The light passes through the dichroic prisms 18 and 17, is reflected by the polarization beam splitter 16, is converged by the detection lens 23, is deflected by the light beam splitting means 24 into a plurality of optical paths, and reaches the light receiving element 25. From the light receiving element 25, an information signal and a servo signal are detected.
- the light reflected by the optical recording medium 1A is deflected by the deflecting prism 19, passes through the dichroic prism 18, is reflected by the dichroic prism 17, is converged by the coupling lens 28, and is converged by the hologram 33.
- the light is diffracted in the direction of the light receiving element 34 in the same can as the laser 13 and received by the light receiving element 34. From the light receiving element 34, an information signal and a servo signal are detected.
- the infrared wavelength is transmitted and the infrared wavelength is
- the light in the region is reflected in the direction of the deflecting prism 19 by the dichroic prism 18 that reflects the light, the optical path is deflected by 90 degrees by the deflecting prism 19, passes through the wave plate 20, is converted into elliptically polarized light or circularly polarized light, and passes through the opening 21.
- the aperture is switched to NA 0.50 by the aperture switching means 22, and the light is incident on the objective lens 2A and focused on the optical recording medium lc as minute spots. The reproduction, recording, or erasing of information is performed by the spot.
- the light reflected by the optical recording medium lc is deflected by the deflecting prism 19, reflected by the dichroic prism 18, converged by the coupling lens 31, and condensed by the hologram 35.
- the light is diffracted in the direction of the light receiving element 36 in the same can as the one 14 and is received by the light receiving element 36. From the light receiving element 36, an information signal and a servo signal are detected.
- FIG. 16 is a schematic perspective view showing a configuration example of the actuator section 4.
- An objective lens 2 and an objective lens holder 41 that holds the objective lens 2 are provided.
- a base 42 for supporting the objective lens holder 41 and elastic support mechanisms 43 and 44 interposed between the base 42 and the objective lens holder 41 are provided.
- the elastic supporting mechanisms 43 and 44 support the objective lens holder 41 in four directions, namely, the focusing direction, the tracking direction, the radial tilt direction, and the tangential tilt direction.
- the focus direction refers to the Z-axis direction (the optical axis direction of the objective lens 2) in FIG. 16
- the tracking direction refers to the X-axis direction (the radial direction of the optical recording medium 1) in FIG.
- the radial tilt direction refers to the tilt direction around the Y axis in FIG. 16 (the direction of the chinole with respect to the radial direction of the optical recording medium 1)
- the tangential tilt direction refers to the tilt direction around the X axis in FIG. Tilt direction with respect to the rotation direction of the recording medium 1).
- a driving unit not shown in FIG. 16 is provided, and this driving unit includes, for example, a permanent magnet provided on the objective lens holder 41 and a driving coil fixed relatively to the base unit 42. It is composed of a so-called voice coil motor.
- the driving means drives the objective lens holder 41 in the four directions according to the input current to the driving coil.
- focus servo and tracking servo for following a predetermined laser light spot on a recording track on the information recording surface of the optical recording medium 1 are performed, and laser light is input.
- the tilt servo is performed such that the direction (ie, the optical axis of the objective lens 2) suppresses coma on the information recording surface of the optical recording medium 1.
- FIG. 17 is a schematic diagram illustrating a configuration example of a tilt detection optical system as the tilt detection unit 5.
- the essential parts of the tilt detection optical system are a semiconductor laser 51, a collimator lens 52, a half mirror 53, a quarter-wave plate 20, a polarizing beam splitter 54, a first light receiving element 55, and a second light receiving element. It consists of element 56. Divergence of linearly polarized light emitted from semiconductor laser 51 The light is deflected by 90 degrees in the optical path by the half mirror 53 and is converted into substantially parallel light by the collimator lens 52.
- the surface on the light source side of the subsequent quarter-wave plate 105 is coated with a predetermined coating, and a part of the light from the half mirror 53 is reflected, and the remaining components are transmitted.
- the light transmitted through the 1/4 wavelength plate 20 is converted into circularly polarized light by passing through the 1Z4 wavelength plate 20, and is reflected by the optical recording medium 1.
- the reflected light from the optical recording medium 1 becomes circularly polarized light in the opposite direction to the outward path, passes through the quarter-wave plate 20 again, and becomes linearly polarized light orthogonal to the outward path.
- the light reflected on the surface of the 1Z4 wavelength plate 20 and the light passing through the 1Z4 wavelength plate 20 and reflected on the optical recording medium 1 are incident on the collimator lens 52 as reflected light with the polarization directions orthogonal to each other. Then, each reflected light passes through substantially the same optical path, passes through a half mirror 53, and enters a polarization beam splitter 54.
- the optical path of the reflected light from the surface of the quarter-wave plate 20 and the reflected light from the optical recording medium 1 are separated by the polarizing beam splitter 54.
- the reflected light from the optical recording medium 1 is reflected by the polarizing beam splitter 54 and is transmitted to the first light receiving element 55, and the reflected light from the quarter wave plate 20 is transmitted through the polarizing beam splitter 54 and transmitted to the second light receiving element 56. Leads to.
- a tilt signal a method of dividing a light receiving element and a method of calculating an output signal will be described.
- the first light receiving element 55 (similarly to the second light receiving element 56) uses a four-division light receiving element divided into light receiving parts 55c-55f as shown in FIG.
- a two-segment light receiving element having only the light receiving portions 55a and 55b (in the second light receiving element 56, a two-segment light receiving element having only the light receiving portions 56a and 56b) Shall be used.
- the light receiving element 55 that detects reflected light from the optical recording medium 1 includes a pair of light receiving sections 55a and 55b.
- the pair of light receiving sections 55a and 55b are arranged along the radial direction of the optical recording medium 1. Therefore, when the optical recording medium 1 is tilted, the level of the detection signal from one of the pair of light receiving sections 55a and 55b becomes higher than the other in accordance with the direction.
- the pair of light receiving sections 55a and 55b are connected to preamplifiers 61 and 62, respectively.
- the preamplifiers 61 and 62 are connected to a difference circuit 63 that outputs a difference between output signals from the preamplifiers 61 and 62 as a difference output signal.
- Difference circuit 63 By calculating the force difference output signal, the amount of inclination of the optical recording medium 1 is obtained.
- the reflectivity of the optical recording medium 1 fluctuates, or the light intensity of the light beam emitted from the light source 301 fluctuates with time, as a result, the characteristics of the detection signals from the preamplifiers 311 and 312 change. Is corrected by a subsequent circuit. That is, the signals from the preamplifiers 61 and 62 are added by the adding circuit 64, and the added output is input to the dividing circuit 65.
- the division circuit 65 the difference output from the difference circuit 63 is standardized on the basis of the added output, the fluctuation component included in the difference output is removed, and the tilt signal of the optical recording medium 1 is output from the division circuit 65. Generated.
- the second light receiving element 56 includes a pair of light receiving portions 56a and 56b.
- the pair of light receivers B56a and 56b are connected to preamplifiers 66 and 67, respectively, and are laid out.
- the preamplifiers 66 and 67 are similarly connected to a difference circuit 68 that outputs a difference between output signals from the preamplifiers 66 and 67 as a difference output signal.
- the tilt amount of the actuator unit 4 that is, the objective lens 2
- the light intensity of the light beam emitted from the light source 51 fluctuates with time, and the characteristics of the detection signals from the preamplifiers 66 and 67 are changed. This change in the characteristics is corrected by a subsequent circuit. That is, the signals from the preamplifiers 66 and 67 are similarly added by the adding circuit 69, and the added output is input to the dividing circuit 70.
- the difference output from the difference circuit 68 is standardized on the basis of the addition output, and the fluctuation component included in the difference output is removed.
- the tilt signal of the objective lens 2 is output from the division circuit 70. Is output.
- the division circuits 65 and 70 that output a tilt signal corresponding to the amount of tilt of the optical recording medium 1 and the objective lens 2 are connected to a difference circuit 72, and the difference between the tilt signals is generated from the difference circuit 72. I do.
- the difference output from the difference circuit 72 corresponds to the relative tilt amount of the objective lens 2 with respect to the optical recording medium 1.
- a switch 71 is provided at a stage preceding the differential circuit 72, and selects an objective lens tilt signal and a relative tilt signal according to a control procedure as described later. To perform tilt control.
- control may be performed based on a map stored in advance. For example, when a signal indicating that the relative angle between the optical recording medium 1 and the predetermined reference plane of the optical pickup 11 is tilted by 0.6 deg in FIG. 3A is first detected, the object lens 2 and the optical pickup 11 are successively detected. Feedback may be performed so that the relative angle with respect to the predetermined reference plane is 0.6 deg.
- a predetermined gain (not shown) may be added (correction means). Further, the gain may be switched according to the light source (correction means). For example, as described above, since the correction lens tilt amount differs depending on the type of the optical recording medium 1, a gain is added to one of the above (2) and (3) so that a signal of the same level is always output. Moore.
- the lens tilt actuator 4 is designed to correct the inclination error of the light beam incident on the objective lens 2 generated during the assembly adjustment of the optical pickup 11 and the coma aberration caused by the manufacturing error of the objective lens 2.
- the tilt is adjusted during assembly. This tilt adjustment is desirably performed for a lighting light source in which the coma aberration is largely degraded due to lens tilt.
- the assembly adjustment is not performed for the other wavelengths, but according to the present embodiment, the inclination error of the light beam incident on the objective lens 2 and the Confirm the optimal position of the objective lens to correct coma due to the manufacturing error of Fig. 3 (d), 4 (d), 05 (d), 07 (d), and 8 ( By offsetting the relations of (d), FIGS. 9 (d), 011 (d), and FIG. 12 (d), it is possible to correct the coma aberration corresponding to the assembly manufacturing error by adjusting the lens tilt.
- the former may be corrected by the tilt signal offset without performing the former tilt adjustment.
- a force S using a tilt angle between the objective lens 2 and the optical recording medium 1 and a driving signal between the objective lens 2 and the optical recording medium 1 are used as drive signals for the actuator section 4.
- a method of correcting coma caused by relative tilt may be used.
- the optical recording medium 1 has a plan groove 81 as shown in FIG.
- the reflected light from the guide groove 81 includes the 0th-order light, which is directly reflected light, and the diffracted ⁇ 1st-order diffracted light, and these lights interfere with each other.
- FIG. 21 is a diagram of the 0th-order light (straight-forward light) and ⁇ 1st-order diffracted light received on the light receiving surface of the light receiving element 56 as viewed from above the light receiving surface of the light receiving element 56.
- the 0th-order light (straight-forward light) and the 1st-order diffracted light have overlapping portions, and this overlapping portion is called an interference region 82.
- FIG. 22 shows a change in the interference area 82 when the optical recording medium 1 is inclined in the radial direction (radial direction).
- the amount of light is biased on the left and right in FIG. This is because coma aberration occurs in spots projected on the optical recording medium 1 due to the inclination of the optical recording medium 1.
- This deviation occurs in the opposite direction between the one interference area 82 and the other interference area 82.
- FIG. 23 shows a change in the interference area 82 when the optical recording medium 1 is tilted in the rotation direction (tangential direction).
- a plurality of divided light receiving elements 83 that can detect a change in the pattern of the interference area 82 are used.
- FIG. 32 is a schematic block diagram showing a configuration example of the optical pickup 200 of the present embodiment corresponding to FIG.
- the optical pickup 200 of the present embodiment includes a semiconductor laser 201 in the blue wavelength band, a collimating lens 202, a polarizing beam splitter 203, a dichroic prism 204, a deflecting prism 205, a 1Z4 wavelength plate 206, an aperture 207, an objective lens 208, An infinite blue optical system through which light in the blue wavelength band composed of the lens 210, the light beam splitting means 211, and the light receiving element 212 passes, a hologram unit 221, a collimating lens 222, a phase correction element 223, and a dichroic prism 204.
- An infinite DVD optical system through which light in the red wavelength band passes which includes a deflecting prism 205, a 1,4-wavelength plate 206, an aperture 207, and an objective lens 208. That is, the dichroic prism 204, the deflecting prism 205, the quarter-wave plate 206, the aperture 207, and the objective lens 208 are in the common optical path of the two optical systems.
- the hologram unit 221 has a laser chip 221a in the DVD wavelength band and a light receiving element 221b integrated with a hologram 221d having a hologram 221c for detection (see FIG. 33).
- the objective lens 208 has a wavelength ⁇ 1 of 405 nm, a numerical aperture NA of 0.65, and a light irradiation side substrate thickness of 0.6 mm. It is optimally designed to satisfy the requirements. Also, since the numerical aperture NA of the blue system and the DVD system is equal to 0.65, the diameter of the luminous flux incident on the objective lens 208 should be approximately equal so that the aperture (aperture element) 207 is shared and the objective lens 208 is shared. Place it just before.
- the optical recording media 209a and 209b are optical recording media having different working wavelengths.
- the optical recording medium 209a is a blue optical recording medium having a substrate thickness of 0.6 mm.
- the optical recording medium 209b is a substrate thickness. Is a 0.6 mm DVD-based optical recording medium.
- a rotating mechanism not shown
- an objective lens tilt actuator (lens driving device) 224 capable of inclining the objective lens 208 in a radial direction or a tangential direction of the optical disk is provided.
- a blue optical recording medium 209a having a wavelength ⁇ l of 405 nm, a numerical aperture NA of 0.65, and a light-irradiation side substrate thickness of 0.6 mm.
- An example of the operation in this case will be described.
- the divergent light of linearly polarized light is converted into substantially parallel light by the collimating lens 202, passes through the polarizing beam splitter 203 and the dichroic prism 204, is deflected by 90 degrees in the optical path by the deflecting prism 205, and passes through the quarter-wave plate 206.
- the light is converted into circularly polarized light, passes through the aperture 207, enters the objective lens 208, and is focused as a minute spot on the optical recording medium 209a.
- the information is reproduced, recorded or erased by this spot.
- the light reflected from the optical recording medium 209a becomes circularly polarized light in the opposite direction to the outward path, becomes almost parallel light again, passes through the quarter-wave plate 206, becomes linearly polarized light orthogonal to the outward path, and becomes a polarization beam splitter.
- the light is reflected by the light 203, is converged by the condenser lens 210, is deflected by the light beam splitting means 211 into a plurality of light paths, and reaches the light receiving element 212. From the light receiving element 212, an information signal and a servo signal are detected.
- the hologram unit 221 is used for the DVD system, and the 660 nm light emitted from the laser chip 221a of the hologram unit 221 passes through the hologram 221d, and is converted into substantially parallel light by the collimating lens 222.
- spherical aberration is added by the phase correction element 223 so as to correct chromatic aberration that occurs when the objective lens 108 optimized for blue is used in the red wavelength region.
- the light in the region is reflected in the direction of the deflection prism 205 by the dichroic prism 204 that reflects the light, the optical path is deflected by 90 degrees by the deflection prism 205, passes through the quarter-wave plate 206, becomes circularly polarized light, and passes through the aperture 207. Then, the light enters the objective lens 208 and is focused as a minute spot on the optical recording medium 209b. The information is reproduced, recorded or erased by the spot.
- the light reflected from the optical recording medium 209b is deflected by the deflecting prism 205, reflected by the dichroic prism 204, and converged by the collimating lens 222, and is received by the hologram 221d in the same can as the laser chip 221a.
- the light is diffracted in the direction and is received by the light receiving element 221b.
- An aberration signal, an information signal, and a servo signal are detected from the light receiving element 221b.
- the configuration itself of the objective lens tilt actuator 224 is the same as the configuration of the actuator section 4 shown in FIG.
- the numerical aperture NA of the DVD or the disc substrate thickness, or the numerical aperture NA and the substrate thickness Need to be substantially the same as blue, which is the design wavelength. If the numerical apertures NA or the substrate thicknesses of the two differ greatly, aberration degradation during use of the DVD infinite system increases, making it difficult or impossible to correct the phase with the phase correction element 223 described above. Also, by making the substrate thickness the same, the manufacturing infrastructure for blue and DVD optical disk substrates can be shared, so that the manufacturing cost of a new blue optical disk can be reduced.
- the numerical aperture NA if the numerical aperture NA in blue is smaller than that of a DVD, the focused spot on the optical disk cannot be made sufficiently small, and it is difficult to achieve the intended purpose of increasing the capacity. Become. Also, when the numerical aperture NA is set to be larger than that of a DVD, in addition to the above-mentioned problem that the aberration degradation when using the infinite DVD system increases, the occurrence of coma due to the disc tilt increases and the disc tilt margin decreases. This is because it becomes extremely difficult to perform correction within the margin even with the tilt correction means according to the present embodiment.
- This embodiment has a configuration in which an optical system for CD is added to the second embodiment to provide a three-wavelength optical pickup 300, and an optical system for CD is added to the second embodiment. Is different. That is, in this embodiment, a blue light having a wavelength of l; 405 nm, a numerical aperture NA of 0.65, and a light irradiation side substrate thickness of 0.6 mm is used. Recording medium and working wavelength 2; 660 nm, numerical aperture NA; 0.65, light-irradiation side substrate thickness; 0.6 mm DVD system optical recording medium and working wavelength 3; 785 nm, numerical aperture NA; 0.50, light irradiation side Substrate thickness: 1. Related to an optical pickup that records, reproduces, or erases three types of optical recording media, including a 2 mm CD optical recording media.
- FIG. 35 is a schematic block diagram showing a configuration example of the optical pickup 300 of the present embodiment, similarly to FIG.
- the optical pickup 230 of the present embodiment first, a semiconductor laser 201 having a wavelength of I l; 405 nm, a collimating lens 202, a polarizing beam splitter 203, dichroic prisms 204 and 301, a deflecting prism 205, a wavelength plate 206, an aperture switch
- An infinite blue optical system through which light having a wavelength of 405 nm passes is provided with an element 207, an objective lens 208, a detection lens 210, a light beam splitting means 211, and a light receiving element 212.
- the hologram unit 221, collimating lens 222, phase correction element 223, dichroic prisms 204 and 301, deflection prism 205, wavelength plate 206, aperture switching element 207, and objective lens 208 allow light with a wavelength of 660 nm to pass.
- An infinite DVD optical system is constructed.
- the hologram unit 302 the coupling lens 303, the dichroic prism 301, the deflecting prism 205, the wave plate 206, the aperture switching element 207, and the objective lens 208 are provided, and a finite system CD optic through which light of 785 nm wavelength passes.
- the system is configured.
- the dichroic prisms 204 and 301, the prism 205, the wavelength plate 206, the aperture switching element 207, and the objective lens 208 shown in FIG. 35 are common components used in two or three optical systems.
- the objective lens 208 of the present embodiment has a wavelength ⁇ 1 of 405 nm, a numerical aperture NA of 0.65, a light irradiation side substrate thickness of 0.6 mm, and a blue optical recording medium 209 a. It is optimally designed to satisfy the sine condition by infinite system incidence.
- the numerical aperture NA for blue and DVD is equal to 0.65, the diameter of the luminous flux incident on the objective lens 208 can be set to be approximately equal. Place it just before
- the optical recording medium 209a is a blue optical recording medium having a substrate thickness of 0.6 mm
- the optical recording medium 209b is a DVD optical recording medium having a substrate thickness of 0.6 mm
- the optical recording medium 209c is a substrate thickness. This is a 1.2 mm CD optical recording medium.
- only one of the optical recording media 209a, 209b or 209c is set in a rotating mechanism (not shown) and rotated at high speed.
- an objective lens tilt actuator 224 capable of tilting the objective lens 208 in the radial direction or the tangential direction of the optical disk 209 is provided.
- a hologram unit is generally used for picking up a CD system as well as a DVD system, in which a light receiving / emitting element is installed in one can and a light beam is separated using a hologram. Similarly to the hologram unit 221 shown in FIG.
- a hologram unit 302 in which the semiconductor laser 302a, the hologram 302d, and the light receiving element 302c are integrated is configured.
- the 780 nm light emitted from the semiconductor laser 302 a of the hologram unit 302 passes through the hologram 302 d and is converted into a predetermined divergent beam by the coupling lens 303.
- the light in the wavelength range is reflected in the direction of the prism 205 by the dichroic prism 301 that reflects the light, the optical path is deflected by 90 degrees by the deflecting prism 205, passes through the wavelength plate 206, and is converted into elliptically polarized light or circularly polarized light.
- the numerical aperture is limited to NA; 0.50, the light enters the objective lens 208, and is focused as a minute spot on the optical recording medium 209c. The reproduction, recording, or erasing of information is performed by the spot.
- the light reflected from the optical recording medium 209c is deflected by the prism 205, reflected by the dichroic prism 301, is converged by the coupling lens 303, is folded in the direction of the light receiving element 302c, and is folded in the direction of the light receiving element 302c.
- an aberration signal, an information signal, and a servo signal are detected.
- the configuration of the objective lens tilt actuator 221 for correcting coma aberration and the tilt correction operation are the same as those in the second embodiment, and a description thereof will be omitted. I do.
- the numerical aperture NA or the DVD of the DVD is used. It is necessary to make both the disk substrate thickness or the numerical aperture NA and the substrate thickness approximately the same as the design wavelength, blue. If the numerical aperture NA or the substrate thickness of both differ greatly, DVD Aberration degradation when using an infinite system becomes large, and it becomes difficult or impossible to perform correction by the phase correction element 223 described above. In addition, by making the substrate thickness the same, the manufacturing infrastructure for blue and DVD optical disc substrates can be shared, and it is possible to reduce the manufacturing cost of new blue optical discs.
- the numerical aperture NA if the numerical aperture NA in blue is smaller than that of DVD, the focused spot on the optical disc cannot be made sufficiently small, and the desired purpose of increasing the capacity and achieving the desired performance will be achieved. It becomes difficult.
- the numerical aperture NA is set to be larger than that of a DVD, the above-mentioned problem that the deterioration of aberrations when using the infinite DVD system is large increases, and the occurrence of coma due to the disc tilt increases, thereby increasing the disc tilt margin. This is because it is extremely difficult to correct within the margin even with the tilt correcting means according to the present embodiment.
- the diameter of the incident light beam to the objective lens 208 has a difference due to the difference in the refractive index depending on the wavelength.
- a single aperture element 207 can be used in common, and an increase in the number of parts can be suppressed.
- the optical information processing device 91 of the present embodiment has a configuration as shown in FIG. 15 (FIG. 32 or FIG. 35) for a plurality of types of optical recording media la, lb, or lc having different application wavelengths and numerical apertures NA.
- This is a device that uses the optical pickup 11 (200 or 300) to record, reproduce, or erase information with compatibility.
- the optical recording medium l (la, lb or 1c) has a disk shape and is stored in the protective case 93.
- optical recording medium l (la, lb or 1c) is inserted and set together with the protective case 93 from the entrance 94 into the optical information processing device 91 in the direction indicated by the arrow, and rotated by the spindle motor 95.
- the information is recorded, reproduced, or erased by the optical pickup 11.
- Optical recording medium 1 (la, lb or lc) need not be in protective case 93 and may be bare.
- the third generation of blue / DVD / CD (or blue) that does not require an aberration correction element is used.
Landscapes
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Head (AREA)
- Lenses (AREA)
- Optical Recording Or Reproduction (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP04771895A EP1667134B1 (en) | 2003-09-08 | 2004-08-19 | Object lens, optical pickup and optical information processor |
DE602004028261T DE602004028261D1 (de) | 2003-09-08 | 2004-08-19 | Objektlinse, optischer abnehmer und optischer informationsprozessor |
US11/369,967 US20060198254A1 (en) | 2003-09-08 | 2006-03-08 | Objective lens, optical pickup, and optical information processing apparatus |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2003315147 | 2003-09-08 | ||
JP2003-315147 | 2003-09-08 | ||
JP2004-163082 | 2004-06-01 | ||
JP2004163082A JP2005108398A (ja) | 2003-09-08 | 2004-06-01 | 対物レンズ、光ピックアップ及び光情報処理装置 |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/369,967 Continuation US20060198254A1 (en) | 2003-09-08 | 2006-03-08 | Objective lens, optical pickup, and optical information processing apparatus |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2005027109A1 true WO2005027109A1 (ja) | 2005-03-24 |
Family
ID=34315622
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2004/011934 WO2005027109A1 (ja) | 2003-09-08 | 2004-08-19 | 対物レンズ、光ピックアップ及び光情報処理装置 |
Country Status (5)
Country | Link |
---|---|
US (1) | US20060198254A1 (ja) |
EP (1) | EP1667134B1 (ja) |
JP (1) | JP2005108398A (ja) |
DE (1) | DE602004028261D1 (ja) |
WO (1) | WO2005027109A1 (ja) |
Families Citing this family (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2007133967A (ja) | 2005-11-10 | 2007-05-31 | Canon Inc | 光学式情報記録再生装置 |
JP2008084490A (ja) * | 2006-09-28 | 2008-04-10 | Sony Corp | 対物レンズ、光ピックアップ装置及び光ディスク装置 |
TW200844987A (en) * | 2007-03-22 | 2008-11-16 | Koninkl Philips Electronics Nv | Optical apparatus |
JP5075681B2 (ja) * | 2008-03-05 | 2012-11-21 | 日立マクセル株式会社 | 対物レンズ |
JP2009223936A (ja) * | 2008-03-14 | 2009-10-01 | Ricoh Co Ltd | 光ピックアップおよびこれを用いる光情報処理装置 |
JP2009223938A (ja) * | 2008-03-14 | 2009-10-01 | Ricoh Co Ltd | 光ピックアップおよびこれを用いる光情報処理装置 |
JP2009223937A (ja) * | 2008-03-14 | 2009-10-01 | Ricoh Co Ltd | 光ピックアップおよびこれを用いる光情報処理装置 |
US8467282B2 (en) * | 2008-08-07 | 2013-06-18 | Panasonic Corporation | Optical disc device, optical head, and information processing device |
JPWO2010044355A1 (ja) * | 2008-10-17 | 2012-03-15 | コニカミノルタオプト株式会社 | 対物レンズ及び光ピックアップ装置 |
JP4849134B2 (ja) * | 2009-01-26 | 2012-01-11 | ソニー株式会社 | 対物レンズ、光ピックアップ及び光ディスク装置 |
JP5884081B2 (ja) * | 2009-09-17 | 2016-03-15 | パナソニックIpマネジメント株式会社 | 対物レンズ素子及びこれを用いた光ピックアップ装置 |
JP2012033213A (ja) * | 2010-07-29 | 2012-02-16 | Hitachi Media Electoronics Co Ltd | 光学的情報記録再生装置 |
WO2013147014A1 (ja) * | 2012-03-29 | 2013-10-03 | コニカミノルタ株式会社 | 対物レンズ、光ピックアップ装置及び光情報記録再生装置 |
CN111307063B (zh) * | 2020-03-25 | 2021-08-24 | 江南大学 | 一种消除单幅干涉条纹波面恢复中的符号模糊问题的方法 |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
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WO2001013369A1 (fr) * | 1999-07-30 | 2001-02-22 | Matsushita Electric Industrial Co., Ltd. | Objectif et dispositif a tete optique |
JP2003279851A (ja) * | 2002-03-20 | 2003-10-02 | Matsushita Electric Ind Co Ltd | 高開口数単レンズおよびそれを用いた光ヘッド装置、光学情報記録再生装置 |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3384393B2 (ja) * | 1999-12-15 | 2003-03-10 | 日本電気株式会社 | 光ヘッド装置及び光学式情報記録再生装置並びにラジアルチルト検出方法 |
JP2002008301A (ja) * | 2000-06-23 | 2002-01-11 | Hitachi Ltd | 情報記録再生装置及びそのディスク判別方法 |
US6590717B2 (en) * | 2000-09-26 | 2003-07-08 | Matsushita Electric Industrial Co., Ltd. | Optical system for optical disk, optical head unit for optical disk, and optical drive device |
JP2002107617A (ja) * | 2000-09-29 | 2002-04-10 | Toshiba Corp | 対物レンズ、それを用いた光ヘッド装置及び光ディスク装置 |
JP2002163830A (ja) * | 2000-11-24 | 2002-06-07 | Toshiba Corp | 光学的収差を利用した光情報処理システムおよび厚みムラのある透明層で保護された記録層を持つ情報媒体 |
JP2003296959A (ja) * | 2002-03-26 | 2003-10-17 | Samsung Electro Mech Co Ltd | 波長選択性開口制限素子と波長選択性ビームスプリッタ及びそれを備えた光ピックアップ装置 |
AU2003235244A1 (en) * | 2002-04-18 | 2003-11-10 | Matsushita Electric Industrial Co., Ltd. | Optical element, optical head, optical information recording/reproduction device, computer, video recording device, video reproduction device, server, and car navigation system |
JP2004327003A (ja) * | 2002-07-26 | 2004-11-18 | Sharp Corp | 光ピックアップ |
US7277366B2 (en) * | 2003-02-28 | 2007-10-02 | Matsushita Electric Industrial Co., Ltd. | Optical head and optical recording and reproducing apparatus |
-
2004
- 2004-06-01 JP JP2004163082A patent/JP2005108398A/ja active Pending
- 2004-08-19 EP EP04771895A patent/EP1667134B1/en not_active Expired - Lifetime
- 2004-08-19 WO PCT/JP2004/011934 patent/WO2005027109A1/ja active Application Filing
- 2004-08-19 DE DE602004028261T patent/DE602004028261D1/de not_active Expired - Lifetime
-
2006
- 2006-03-08 US US11/369,967 patent/US20060198254A1/en not_active Abandoned
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001013369A1 (fr) * | 1999-07-30 | 2001-02-22 | Matsushita Electric Industrial Co., Ltd. | Objectif et dispositif a tete optique |
JP2003279851A (ja) * | 2002-03-20 | 2003-10-02 | Matsushita Electric Ind Co Ltd | 高開口数単レンズおよびそれを用いた光ヘッド装置、光学情報記録再生装置 |
Non-Patent Citations (1)
Title |
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See also references of EP1667134A4 * |
Also Published As
Publication number | Publication date |
---|---|
US20060198254A1 (en) | 2006-09-07 |
JP2005108398A (ja) | 2005-04-21 |
EP1667134A4 (en) | 2009-01-07 |
DE602004028261D1 (de) | 2010-09-02 |
EP1667134A1 (en) | 2006-06-07 |
EP1667134B1 (en) | 2010-07-21 |
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