WO2010084784A1 - 光学ヘッド及び光情報装置 - Google Patents
光学ヘッド及び光情報装置 Download PDFInfo
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- WO2010084784A1 WO2010084784A1 PCT/JP2010/000428 JP2010000428W WO2010084784A1 WO 2010084784 A1 WO2010084784 A1 WO 2010084784A1 JP 2010000428 W JP2010000428 W JP 2010000428W WO 2010084784 A1 WO2010084784 A1 WO 2010084784A1
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- WIPO (PCT)
- Prior art keywords
- optical head
- cylindrical lens
- photodetector
- holder
- optical
- Prior art date
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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
- G11B7/0908—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
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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
- G11B7/13—Optical detectors therefor
- G11B7/131—Arrangement of detectors in a multiple array
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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
- G11B7/1372—Lenses
- G11B7/1378—Separate aberration correction lenses; Cylindrical lenses to generate astigmatism; Beam expanders
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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
- G11B7/22—Apparatus or processes for the manufacture of optical heads, e.g. assembly
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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
- G11B2007/0003—Recording, reproducing or erasing systems characterised by the structure or type of the carrier
- G11B2007/0009—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage
- G11B2007/0013—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage for carriers having multiple discrete layers
Definitions
- the present invention relates to an optical head and an optical information apparatus for recording information on an information recording medium such as an optical disk or an optical card or reproducing the recorded information.
- FIG. 27 and FIG. 28 show the optical head described in Patent Document 1 and its light detection unit.
- the light beam emitted from the semiconductor laser 101 is separated into a plurality of different light beams by the diffraction grating 102.
- the light beam that has passed through the diffraction grating 102 is reflected by the beam splitter 103 and converted into a parallel light beam by the collimator lens 104.
- This light beam enters the objective lens 105 and is irradiated onto the optical disc 201 as so-called three-beam convergent light.
- the objective lens 105 is driven by the objective lens actuator 106 in the optical axis direction (focus direction) and the radial direction of the optical disc 201 (radial direction).
- the light beam reflected and diffracted by the information layer 202 of the optical disc 201 passes through the objective lens 105 again and passes through the beam splitter 103.
- the light beam that has passed through the beam splitter 103 passes through the cylindrical lens 115 and enters the photodetector 120.
- FIG. 28 is a partial schematic view of the optical head 200.
- the optical base 113 holds the semiconductor laser 101, the diffraction grating 102, the beam splitter 103, the collimator lens 104, and the objective lens actuator 106.
- the cylindrical lens 115 is installed such that a concave cylindrical lens surface having a negative (concave lens effect) lens power is on the photodetector side.
- the cylindrical lens 115 can be adjusted in position in the optical axis direction on the optical base 113 while being fixed to the lens holder 159, and is held by an external jig in this state.
- the position of the photodetector 120 can be adjusted in a plane (XY plane) orthogonal to the optical axis while being held by an external jig.
- FIG. 29 schematically shows the light receiving surface 121 of the photodetector 120.
- the light beam transmitted through the cylindrical lens 115 is received by the four-divided light receiving region 140.
- a so-called focus signal is detected by calculating a difference between the sum signals of the diagonal areas in the quadrant light receiving area 140.
- the RF signal is detected by calculating the sum signal of the four-divided light receiving region 140.
- the push-pull signal obtained by calculating the signal obtained from the four-divided light receiving area 140 and the signal corresponding to the amount of light received by the sub-beam light receiving area 141 are calculated by the adding amplifier 144 and the differential amplifier 145.
- a tracking error signal of a three-beam method (so-called DPP method) is generated, and tracking servo for causing the objective lens 105 to follow the track of the information layer 202 is performed.
- the photodetector 120 is arranged away from the concave cylindrical lens surface of the cylindrical lens 115 in order to ensure symmetry and linearity of the focus error signal. Therefore, the position of the photodetector 120 on the XY plane is adjusted alone or integrally with the holder. This position adjustment is performed while looking at the detection signal from the photodetector 120 so that the light beam enters the approximate center of the four-divided light receiving unit 140. Thereafter, the photodetector 120 (or holder) is fixed to the optical base 113.
- the lens holder 159 to which the cylindrical lens 115 is fixed is held on the optical base 113 so as to be movable in the optical axis direction.
- the relative position to the photodetector 120 is adjusted, and the optical base 113 and the lens holder 116 are fixed thereon.
- This adjustment in the Z direction eliminates the focus error signal offset at a distance at which the objective lens 105 and the information layer 202 are just focused. That is, the output of the focus error signal becomes 0 at the distance for the just focus.
- a cylindrical lens may have a concave lens surface with a small radius of curvature to generate a large negative lens power. Necessary.
- An object of the present invention is to provide a small optical head capable of improving signal characteristics when recording and reproducing on a high recording density multilayer optical information recording medium.
- An optical head includes a light source that emits a light beam, an objective lens that focuses the light beam emitted from the light source as convergent light on an information recording medium, and a reflected light beam that is reflected by the information recording medium.
- a cylindrical lens for generating astigmatism to be incident and forming a focus error signal; a photodetector for receiving a reflected light beam transmitted through the cylindrical lens; a holder for holding the cylindrical lens and the photodetector; .
- the holder has a first main surface and a second main surface extending in a direction intersecting with the optical axis of the reflected light beam, the cylindrical lens is bonded to the first main surface, and the photodetector is Bonded to the second main surface.
- FIG. 1 is a diagram schematically showing an optical system of an optical head according to a first embodiment of the present invention.
- A is a side view schematically showing a photodetector provided in the optical head according to the first embodiment of the present invention
- (b) is a front view schematically showing the photodetector
- (C) is a side view schematically showing the photodetector. It is a figure for demonstrating arrangement
- FIG. 1 is a perspective view of the cylindrical lens provided in 1st Embodiment of this invention
- (b) is a front view of the said cylindrical lens
- (c) is a direction different from (a). It is the perspective view of the said cylindrical lens seen from. It is the schematic which shows partially the optical head by 1st Embodiment of this invention.
- (A) is a side view schematically showing a detector unit provided in the optical head according to the first embodiment of the present invention
- (b) is a front view schematically showing the detector unit
- (C) is a side view schematically showing the detector unit. It is a figure for demonstrating the light beam which permeate
- FIG. 8 is a diagram for explaining a light beam that passes through the cylindrical lens when the cylindrical lens is disposed in the opposite direction to the state of FIG. 7 (the cylindrical surface is on the photodetector side).
- A is a figure for demonstrating the positional relationship of the spot diameter and cylindrical surface in the focus position in the state of FIG. 7
- (b) is the spot diameter and cylindrical in the focus position in the state of FIG. It is a figure for demonstrating the positional relationship with a surface
- (c) is a figure which shows an example of the focus error signal in the case of (a)
- (d) is the focus in the case of (b). It is a figure which shows an example of an error signal.
- the optical head is a diagram for explaining the shape of a light beam incident on a quadrant light receiving region of the photodetector. It is a figure for demonstrating the fixing method of the detector unit and optical base in the optical head by 1st Embodiment of this invention.
- (A) is a figure which shows the relationship between the magnification of a detection optical system, and spot position shift
- (b) is a figure for demonstrating the definition of PD balance (Y direction).
- (A) is a figure explaining the light beam which injects into the recording layer of a two-layer disc
- (b) is a figure explaining the light beam which injects into the recording layer of a multilayer disk (four layer disk).
- (A) is a figure for demonstrating the other layer stray light which injects on the photodetector as a comparative example
- (b) is the photodetector provided in the optical head by 1st Embodiment of this invention. It is a figure for demonstrating the other layer stray light which injects on.
- (A) is a figure for demonstrating the aperture diameter at the time of the Z direction adjustment of the cylindrical lens in a comparative example
- (b) is Z of the detector unit in the optical head by 1st Embodiment of this invention. It is a figure for demonstrating the aperture diameter at the time of direction adjustment.
- (A) is a figure for demonstrating the aperture diameter at the time of the X direction adjustment of the cylindrical lens in a comparative example
- (b) is the X direction of the cylindrical lens in the optical head by 1st Embodiment of this invention. It is a figure for demonstrating the aperture diameter at the time of adjustment
- (c) is a figure for demonstrating the aperture diameter in the optical head by 1st Embodiment of this invention. It is a figure which shows schematically the aperture shape in the modification of the optical head by 1st Embodiment of this invention.
- 1 is a diagram schematically showing an optical disc drive of an optical information device to which an optical head according to a first embodiment of the present invention is applied.
- FIG. (A) is a side view schematically showing a detector unit in an optical head according to a second embodiment of the present invention
- (b) is a front view schematically showing the detector unit
- (c) ) Is another side view schematically showing the detector unit.
- FIG. (A) is a side view schematically showing a detector unit in an optical head according to a third embodiment of the present invention
- (b) is a front view schematically showing the detector unit
- (c) ) Is another side view schematically showing the detector unit
- (d) is a side view schematically showing a modification of the detector unit.
- (A) is a figure which shows schematically the optical system of the optical head by 4th Embodiment of this invention
- (b) is a figure for demonstrating the area
- (A) is a front view which shows roughly the photodetector provided in the optical head by 4th Embodiment of this invention
- (b) is a figure for demonstrating the light reception area
- (C) is a cross-sectional view for explaining the relative positional relationship between the photodetector and the aperture.
- FIG. (A) is a figure which shows schematically the optical system of the optical head by 5th Embodiment of this invention, (b) is for demonstrating the direction around the axis
- FIG. (A) is a side view schematically showing a detector unit provided in an optical head according to a fifth embodiment of the present invention, and (b) is a front view schematically showing the detector unit.
- (C) is a side view schematically showing the detector unit.
- (A) is a side view of a detector unit for explaining a bonding position between a holder and an optical base provided in an optical head according to a sixth embodiment of the present invention, and (b) is a diagram illustrating the holder and the optical base.
- FIG. 1 It is a front view of the detector unit which showed the adhesion position of (c), (c) is a side view of the modification of the said detector unit.
- FIG. 1 It is a figure which shows schematically the optical system of the optical head by 7th Embodiment of this invention. It is a figure which shows schematically the structure of the optical system of the conventional optical head. It is a figure which shows the conventional optical head partially. It is a figure for demonstrating arrangement
- FIG. 1 schematically shows an optical system of an optical head 200 according to a first embodiment of the present invention.
- FIG. 1 schematically shows an optical system of an optical head 200 according to a first embodiment of the present invention.
- the same components as those shown in FIG. 27 will be described with the same reference numerals.
- the optical system of the optical head 200 includes a semiconductor laser 101 as a light source, a diffraction grating 102, a beam splitter 103, a collimator lens 104, an objective lens 105, a cylindrical lens 115, a light A detector 120 is provided.
- the light beam emitted from the semiconductor laser 101 is separated into a plurality of light beams by the diffraction grating 102.
- the light beam that has passed through the diffraction grating 102 is reflected by the beam splitter 103, converted into a parallel light beam by the collimator lens 104, and incident on the objective lens 105, and becomes so-called three-beam convergent light.
- This convergent light is applied to the optical disc 201.
- the objective lens 105 is driven by the objective lens actuator 106 in the optical axis direction (focus direction) and the tracking direction (radial direction) of the optical disc 201.
- the light beam reflected and diffracted by the information layer 202 of the optical disc 201 passes through the objective lens 105 again, passes through the collimator lens 104, and enters the beam splitter 103.
- the light beam that has passed through the beam splitter 103 passes through the cylindrical lens 115, passes through the aperture 131 of the holder 130, and enters the photodetector 120.
- the photodetector 120 includes a light receiving unit 124, a cover glass 125, and an adhesive layer 126.
- the light receiving unit 124 includes a light receiving surface 121 having a light receiving region, a circuit unit 122, and a terminal unit 123.
- the adhesive layer 126 adheres the light receiving unit 124 and the cover glass 125. That is, the light receiving unit 124 is fixed to the cover glass 125.
- the terminal portion 123 is mounted on an FPC or a substrate and soldered. The terminal unit 123 outputs a signal corresponding to the amount of received light detected on the light receiving surface 121.
- FIG. 3 schematically shows the light receiving surface 121 of the photodetector 120.
- a four-divided light receiving region 140 and a sub beam light receiving region 141 are formed on the light receiving surface 121.
- the main beam 142 is received by the four-divided light receiving region 140.
- the difference between the signals of the two pairs of diagonal regions in the four-divided light receiving region 140 (the two sum signals of the diagonal regions are obtained, and the difference) is calculated by the addition amplifier 144 and the differential amplifier 145.
- a focus signal is detected.
- the sum signal of each area of the four-divided light receiving area 140 is calculated by the addition amplifier 144, thereby detecting the RF signal.
- a sub-beam of the three-beam method that is a reflected light beam reflected by the track of the information layer 202 of the optical disc 201 and becomes a tracking error signal is incident on the sub-beam receiving area 141 of the photodetector 120.
- the sub beam 143 is received by the sub beam light receiving region 141.
- a signal corresponding to the amount of light received by the sub-beam light receiving region 141 is calculated by the addition amplifier 141 and the differential amplifier 142, thereby obtaining the three-beam method (so-called DPP). Method) tracking error signal is generated.
- FIG. 4 (a) to 4 (c) show the configuration of the cylindrical lens 115.
- FIG. 4B is a front view of the cylindrical lens 115
- FIG. 4A is a perspective view seen from the incident surface side
- FIG. 4C is a perspective view seen from the exit surface side.
- the cylindrical lens 115 is formed in a cylindrical shape as a whole.
- a cylindrical surface 116 is formed on one end surface in the axial direction, and a concave lens surface 117 having a lens power and its surroundings are formed on the other end surface in the axial direction.
- the flat surface 128 is formed.
- the cylindrical lens 115 is disposed such that the cylindrical surface 116 is a light incident surface and the concave lens surface 117 is an output surface.
- the flat surface 128 is a surface perpendicular to the lens optical axis 118 of the cylindrical lens 115 and has an annular shape that is coaxial with the lens optical axis.
- reference numeral 119 denotes a central bus line of the cylindrical surface 116.
- This central bus line coincides with a bus line that intersects the optical axis of the lens among the bus lines forming the cylindrical surface 116.
- the lens optical axis 118 passes through the center of the concave lens surface 117.
- the cylindrical surface 116 is located at the innermost side in the lens optical axis direction at the position of the central bus 119.
- the optical head 200 in the first embodiment includes a detector unit 127.
- the detector unit 127 includes a cylindrical lens 115, a holder 130, and a photodetector 120, and is arranged so that the cylindrical lens 115, the holder 130, and the photodetector 120 are positioned in order from the side where the reflected light beam enters. ing.
- the optical head 200 of the present embodiment includes a holder 130 between the cylindrical lens 115 and the photodetector 120, and the cylindrical lens 115.
- Each of the photodetectors 120 is in contact with the holder 130.
- the cylindrical lens 115 is adhered to the holder 130 in a state of being disposed on one side of the holder 130 in the Z direction (the optical axis direction of the reflected light beam), while the photodetector 120 is attached to the holder 130 in the Z direction. It is bonded to the holder 130 in a state of being disposed on the side.
- FIG. 5 partially shows the optical head 200.
- the optical head 200 is provided with an optical base 113.
- the optical base 113 is, for example, a semiconductor laser 101 (see FIG. 1), a diffraction grating 102 (see FIG. 1), and a beam splitter 103.
- the collimator lens 104 and the objective lens actuator 106 are held.
- the detector unit 127 has a Z direction (optical axis) on the optical base 113 in a state where the holding portion 132 (see FIG. 6A) is chucked with respect to the optical base 113 by an external jig (not shown).
- the position can be adjusted in the XY plane, and the position can be adjusted in the XY plane (in the plane orthogonal to the optical axis).
- Adjustment of the detector unit 127 in the XY plane is performed by moving the detector unit 127 so that the main beam 142 is incident on the approximate center of the four-divided light receiving region 140.
- the position adjustment in the Z direction is performed by moving the detector unit 127 in the Z direction so that the light receiving surface 121 is positioned at the focal position of the astigmatic difference in a state where the objective lens 105 and the information recording layer 202 are in a just-focus state. This is done by fine-tuning.
- the main beam incident on the four-divided light receiving region 140 becomes circular and the focus error signal is offset, and the focus error signal output is 0 because the objective lens 105 and the information recording layer 202 are just focused. It becomes.
- the sub beam 143 enters the approximate center of the sub beam light receiving region 141.
- the balance of the focus error signal is adjusted (defined later) by adjusting the X and Y directions, the offset of the tracking error signal is adjusted by rotating ( ⁇ z), and the focus offset of the focus error signal is adjusted by adjusting the Z direction. I do.
- the position of the detector unit 127 in the Z direction and the XY direction is adjusted.
- the cylindrical lens and the photodetector 120 are fixed to the holder 130, respectively. Therefore, relative positional deviation between the cylindrical lens 115 and the photodetector 120 can be reduced as compared with the conventional optical head.
- FIG. 6A to 6C show the configuration of the detector unit 127.
- FIG. 6A is a side view seen from the photodetector side
- FIG. 6C is a side view seen from the cylindrical lens side
- FIG. 6B is a front view.
- the holder 130 is formed in a flat plate shape having a constant thickness, and as an example, a cylindrical aperture 131, a holding unit 132, a photodetector pressing unit 137, a photodetector positioning unit 135, and a cylindrical lens pressing unit 138. And a cylindrical lens positioning part 136 and the like.
- a cylindrical lens 115 is bonded to a surface on which light reflected by the optical disk is incident, and a photodetector 120 is bonded to a surface opposite to this surface.
- one main surface (one end surface in the optical axis direction of the reflected light beam) of the holder 130 to which the cylindrical lens 115 is bonded is the first main surface, and the other main surface of the holder 130 to which the photodetector 120 is bonded. You may call it the 2nd main surface.
- the first main surface and the second main surface are set parallel to each other.
- the photodetector pressing portion 137 is a portion formed on the second main surface of the holder 130, and is located at a substantially central portion of the second main surface. That is, a part of the second main surface functions as the photodetector pressing portion 137.
- the photodetector 120 is in surface contact with the photodetector pressing portion 137.
- the photodetector positioning unit 135 is provided on the second main surface, and by using the photodetector positioning unit 135, the photodetector 120 can be positioned in the X direction and the Y direction.
- the cylindrical lens pressing portion 138 is a portion formed on the first main surface of the holder 130 and is located at a substantially central portion of the first main surface. That is, a part of the first main surface functions as the cylindrical lens pressing portion 138.
- the flat surface 128 of the cylindrical lens 115 is in surface contact with the cylindrical lens pressing portion 138.
- the cylindrical lens positioning unit 136 is provided on the first main surface and has an arc surface formed concentrically with the aperture 131. This arc surface is a surface facing the peripheral surface of the cylindrical lens 115.
- the aperture 131 is an opening having a circular cross section formed in the range of the photodetector pressing portion 137 and the cylindrical lens pressing portion 138 as viewed in the optical axis direction and penetrating in the thickness direction of the holder 130.
- the thickness of the holder 130 is controlled to be constant, the distance between the photodetector 120 and the cylindrical lens 115 can be accurately defined, and the direction of the cylindrical lens 115 is set in the optical axis direction of the reflected light beam. Can be adjusted with high accuracy.
- the thickness of the holder 130 is about 1.5 mm, for example.
- the holding portion 132 of the holder 130 is chucked by an external jig (not shown), and in this state, the photodetector 120 is pressed against the photodetector pressing portion 137 to detect light.
- the optical detector 120 is positioned by the detector positioning unit 135. Thereby, the photodetector 120 is accurately positioned with respect to the holder 130 in the X direction, the Y direction, and the Z direction. In this state, the photodetector 120 is bonded and fixed by the photodetector bonding portion 133.
- the positional error between the cylindrical lens 115 and the photodetector 120 in the Z direction is only the dimensional error of the holder 130. .
- This dimensional error is determined by the accuracy of the part, which is the molding accuracy or processing accuracy of the holder 130, and can be suppressed to about 5 to 20 ⁇ m or less.
- the positional deviation between the photodetector and the cylindrical lens is about 300 ⁇ as will be described later. Therefore, the positional deviation can be greatly reduced by the configuration of this embodiment. Become.
- the positional deviation of the light beam incident on the photodetector 120 can be reduced, it is possible to prevent the deterioration of the recording / reproducing signal characteristics.
- the cylindrical lens 115 is positioned in the X direction and the Y direction by the cylindrical lens positioning unit 136, and the flat surface 128 of the cylindrical lens 115 is pressed against the cylindrical lens pressing unit 138, thereby causing the cylindrical lens 115 to move in the Z direction. Is positioned. Furthermore, since the cylindrical lens 15 is disposed so that the incident surface side becomes the cylindrical surface 116, the cylindrical surface 116 is irradiated with a parallel light beam by an unillustrated autocollimator or the like, and the shape of the reflected light beam (the central generatrix of the cylindrical surface 116). By confirming 119), the direction of the central bus bar 119 of the cylindrical surface 116 can be confirmed easily and with high accuracy.
- the angle of the cylindrical surface 116 (the direction of the central generatrix 119 of the cylindrical surface 116) is detected and the rotational direction of the cylindrical lens 115 is adjusted, and the cylindrical surface is adjusted.
- the cylindrical lens 115 and the holder 130 may be bonded and fixed by the lens bonding portion 134. Thereby, the photodetector 120 and the cylindrical lens 115 can be positioned with higher accuracy with respect to the holder 130 and the aperture 131.
- the cylindrical surface 116 of the cylindrical lens 115 is located on the incident side of the reflected light beam from the optical information medium.
- an optical head with a small magnification of the detection optical system is not assumed to be close to the distance between the cylindrical lens and the photodetector, a configuration in which the cylindrical surface 116 is disposed on the photodetector side is employed.
- the cylindrical lens 115 and the detector 120 are arranged so as to sandwich the holder 130 therebetween.
- the cylindrical lens 115 is arranged so that the cylindrical surface 116 comes to the light incident surface side. With this configuration, the astigmatic difference can be increased even when the magnification of the detection optical system is large.
- FIG. 7 shows the front focal line, the focal position, and the rear focal line.
- the rotation adjustment is to adjust the direction of the central bus bar 119 of the cylindrical surface 116 with respect to the direction of the dividing line of the four-divided light receiving region 140. For example, as shown in FIG.
- FIG. 8 shows a configuration in which the cylindrical surface 116 of the cylindrical lens 155 is arranged on the photodetector 120 side for comparison with the configuration of FIG.
- FIGS. 9A and 9B show the relationship between the position of the cylindrical surface 116, the position of the front focal line, and the position of the rear focal line with respect to the focal position on the photodetector 120 in FIGS. ing.
- FIG. 9A corresponds to the configuration of FIG. 7 and shows a configuration in which the cylindrical surface 116 and the focal position (the light receiving surface of the photodetector 120) are separated from each other.
- FIG. 9B corresponds to the configuration of FIG. 8 and shows a configuration in which the cylindrical surface 116 and the focal position are close to each other.
- the ratio between the distance from the focal position to the front focal line and the distance from the focal position to the rear focal line is 1: 3, a focus error signal in which the symmetry of the S-shaped signal with respect to the GND is significantly deteriorated (FIG. 9D), resulting in an unstable focus servo.
- the astigmatic distance is also the configuration of FIG. 9B in which the cylindrical surface 116 is disposed on the opposite side of the photodetector 120 with respect to the configuration of FIG. 9A in which the cylindrical surface 116 is disposed on the photodetector 120 side. Then, it can be increased by about 20 to 30%. For this reason, in the configuration of FIG. 9A, it is possible to obtain an S-shaped signal (focus error signal) that secures a wide pull-in range, and a stable focus servo can be realized.
- the flat surface 128 of the cylindrical lens 115 and the holder 130 are in close contact with each other. It is fixed by. Since the cylindrical lens pressing portion 138 and the flat surface 128 are adhered to each other by the cylindrical lens bonding portion 134, the relative displacement and the relative angular displacement between the cylindrical lens 115 and the holder 130 due to the expansion and contraction of the adhesive are prevented. Get smaller. As a result, the quality of the focus error signal can be stabilized. In addition, since the cylindrical surface 116 is disposed on the incident surface side, the rotation adjustment of the cylindrical lens 115 can be performed in a short time and with high accuracy. Therefore, the optical head 200 with excellent performance can be realized.
- the cylindrical surface 116 and the concave lens surface 117 are compared, the cylindrical surface 116 is more difficult to mold and mold even with a lens surface having the same curvature.
- the relative distance between the cylindrical surface 116 and the light receiving surface 121 of the detector 120 can be increased. By increasing this distance, the lens power of the cylindrical surface 116 can be made relatively small, so that the mold processing and molding of the cylindrical surface 116 are facilitated.
- the present embodiment is characterized in that the friction coefficient is low in a predetermined range of the photodetector pressing portion 137 that is a contact surface with the photodetector 120 out of the surface of the holder 130.
- the position of the photodetector 120 can be easily adjusted.
- the surface roughness of a portion corresponding to a predetermined range of the photodetector pressing portion 137 is smaller than the surface roughness of other portions. Yes. For this reason, the surface of the part concerned is smooth.
- the photodetector 120 is pressed against the photodetector pressing portion 137 of the holder 130, and in this state, the XY The position adjustment of the photodetector 120 in the plane is performed. Therefore, by reducing the friction coefficient of the surface of the holder 130 that makes contact with the photodetector 120, a minute movement of 1 micron or less becomes possible, and the positioning adjustment of the photodetector 120 can be accurately performed. become able to.
- the holder 130 can be formed at a lower price.
- the surface in contact with the photodetector 120 is a center portion of the photodetector pressing portion (also referred to as a second main surface) of the holder 130, that is, a region including the position of the center of gravity. That is, by reducing the surface roughness of the region including the barycentric point, it is possible to achieve the desired effect that at least the plane adjustment can be performed smoothly.
- the friction coefficient is low in a predetermined range of the cylindrical lens pressing portion 138 that is a contact surface with the cylindrical lens 115 out of the surface of the holder 130.
- the position of the cylindrical lens 115 can be easily adjusted.
- the cylindrical lens 115 is pressed against the cylindrical lens pressing portion 138 of the holder 130 in a state where the holding portion 132 of the holder 130 is chucked by an external jig (not shown), and in this state, in the XY plane. The position of the cylindrical lens 115 is adjusted.
- the friction coefficient of the surface of the holder 130 that is in contact with the cylindrical lens 115 is reduced. Therefore, by reducing the friction coefficient of the surface of the holder 130 that is in contact with the cylindrical lens 115, a minute movement of 1 micron or less is possible, and the positioning adjustment of the cylindrical lens 115 can be performed accurately. become. Further, by lowering the friction coefficient of the portion in contact with the cylindrical lens 115 intensively, the friction coefficient of the entire cylindrical lens pressing portion 138 (also referred to as the first main surface) is lowered compared to the case where the friction coefficient is lowered. There is an advantage that the holder 130 can be formed at a price.
- the surface that contacts the cylindrical lens 115 is highly likely to be a central portion of the cylindrical lens pressing portion (also referred to as a first main surface) of the holder 130, that is, a region including the position of the center of gravity. That is, by reducing the surface roughness of the region including the barycentric point, it is possible to achieve the desired effect that at least the plane adjustment can be performed smoothly.
- the arc surface of the cylindrical lens positioning portion 136 may have a surface roughness that is comparable to the surface roughness of the cylindrical lens pressing portion 138.
- the positioning adjustment of the photodetector 120 is performed with the photodetector 120 in contact with the holder 130. Therefore, in a predetermined range of the photodetector pressing portion 137 of the holder 130 (for example, a range where the holder 130 and the photodetector 120 are in contact with each other and a range of 300 microns which is a position adjustment range on the second main surface). By making the coefficient of friction of the holder surface lower than that of the surrounding surface, more accurate alignment is possible.
- the positioning adjustment of the cylindrical lens 115 is performed in a state where the cylindrical lens 115 is in contact with the holder 130. Therefore, in a predetermined range of the cylindrical lens pressing portion 138 of the holder 130 (for example, a range in which the holder 130 and the cylindrical lens 115 are in contact with each other and a range of 300 microns serving as a position adjustment range on the first main surface), By making the coefficient of friction lower than that of the surrounding surface, more accurate alignment is possible.
- the surface roughness of at least a part of the second main surface is smaller than the surface roughness of other portions, but the present invention is not limited to this configuration.
- the surface roughness of the entire second main surface may be smaller than the surface roughness of the side surface (surface parallel to the optical axis) of the holder 130.
- the surface roughness of at least a part of the first main surface is smaller than the surface roughness of other portions.
- the present invention is not limited to this configuration. Absent.
- the surface roughness of the entire first main surface may be smaller than the surface roughness of the side surface of the holder 130 (surface parallel to the optical axis).
- FIG. 11 is a diagram showing a method for fixing the detector unit 127 and the optical base 113.
- an adhesive is applied to the holder bonding portion 139 that is the bonding portion between the optical base 113 and the holder 130. Then, the detector unit 127 is fixed to the optical base 113.
- the lateral magnification of a so-called detection optical system having the objective lens 105, the collimating lens 104, and the photodetector 120 is increased, and reflection is performed on other layers. It is necessary to reduce the size of the detection optical system while preventing the stray light from entering the sub-beam receiving region. This is because when the stray light reflected by the other layer enters the sub-beam light receiving region, an offset occurs in the tracking error signal, and the performance of the tracking servo is greatly deteriorated, resulting in a decrease in recording / reproducing performance.
- FIG. 12A shows the relationship between the magnification of the detection optical system (lateral magnification ⁇ ) and the radius of the concave lens portion (concave lens surface) of the cylindrical lens, and the deviation of the sub beam from the main beam on the photodetector.
- the detection optical system here is an optical system of a path through which a reflected light beam passes from the objective lens 105 to the photodetector 120, and includes the objective lens 105, a collimating lens 104, and a cylindrical lens 115.
- the lateral magnification represents the ratio of the focal length in the optical system in which the collimating lens 104 and the cylindrical lens 115 are synthesized to the focal length of the objective lens 105.
- Deviation of the sub beam with respect to the main beam on the photodetector 120 is caused by an error in the distance between the cylindrical lens 115 and the photodetector 120.
- FIG. 12A shows the result of calculating the spot position deviation of the sub beam when the amount of deviation of the distance between the cylindrical lens and the photodetector is about 100 ⁇ m.
- the magnification (horizontal magnification) of the detection optical system is increased to more than 10 times instead of the conventional 5 to 10 times in order to cope with the multilayer optical disk, and the magnification is increased.
- the radius of the concave lens portion rapidly decreases. For this reason, it becomes sensitive to the positional deviation in the optical axis direction between the cylindrical lens and the photodetector, and the deviation of the sub beam with respect to the main beam increases.
- the amount of sub-beam misalignment is converted to PD balance and examined.
- the PD balance is shifted by 30%, the tracking servo characteristics are greatly deteriorated, and the influence on the reproduction or recording signal characteristics cannot be ignored.
- FIG. 7 is a diagram showing the relationship between the central bus bar 119 of the cylindrical surface of the cylindrical lens 115 and the four-divided light receiving region 140.
- the cylindrical lens 115 generates astigmatic differences having different focal positions. This astigmatic difference occurs between the front focal line and the rear focal line that are at an angle of 90 degrees in the XY plane (in the plane orthogonal to the optical axis of the reflected light beam).
- the central bus bar 119 of the cylindrical surface is set in a direction perpendicular to the paper surface, but is arranged at an angle inclined by 45 degrees with respect to the dividing line of the quadrant light receiving region 140 of the photodetector 120 (FIG. 7). 10).
- the magnification (lateral magnification ⁇ ) of the detection optical system is determined by the focal length of the objective lens 105, the focal length of the collimating lens 104, and the optical power of the concave lens surface 117 of the cylindrical lens 115.
- FIG. 10 shows the shape of the front focal line and the rear focal line when viewed in the optical axis direction, and the shape of the light flux on the four-divided light receiving region 140.
- the focus error signal is calculated by (A + C) ⁇ (B + D)
- PD balance (X direction) is obtained as PD balance. Is calculated by ((A + B) ⁇ (C + D)) / (A + B + C + D)
- the PD balance (Y direction) is calculated by ((A + D) ⁇ (B + C)) / (A + B + C + D).
- the position of the detector unit 127 is adjusted in the X direction and the Y direction so that the PD balance (X direction) and the PD balance (Y direction) are closer to zero.
- the 1 ⁇ m deviation of the sub beam on the photodetector corresponds to a deviation of about 5% in the PD balance of the sub beam. For this reason, when the magnification of the detection optical system is 16 times, the PD balance of the sub beam is shifted by about 20%. In addition, when the distance between the cylindrical lens and the photodetector is shifted by 300 ⁇ m, the PD balance is shifted by about 60%. For this reason, the offset of the tracking error signal is increased, and the performance of the tracking servo is greatly deteriorated.
- the lateral magnification is desirably 14 to 16 times.
- the curvature radius of the cylindrical surface may be 2.6 mm or less.
- FIG. 13A schematically shows the surface reflection from another recording layer in the two-layer optical disc 201
- FIG. 13B shows the surface from the other recording layer in the multilayer optical disc 301.
- the reflection is schematically shown.
- FIG. 13A shows how stray light is generated from other recording layers when the focused light 300 is focused on a certain recording layer in the case of the optical disc 201 which is a two-layer disc.
- FIG. 13B shows a state in which stray light is generated from other recording layers when the focused light 300 is focused on a certain recording layer in the case of the optical disc 301 which is a four-layer disc.
- the focus is on the L2 layer (recording layer), and the light reflected by the L0 layer, the L1 layer, and the L3 layer (recording layer) becomes the other layer stray light.
- the layer interval d2 between the L0 layer and the L1 layer is 25 ⁇ 5 ⁇ m in accordance with the standard, and is 20 ⁇ m at the minimum and 30 ⁇ m at the maximum.
- the magnitude of the other-layer stray light on the photodetector 120 is limited to some extent.
- the smallest layer spacing d4min in the example shown, the layer spacing between the L2 layer and the L3 layer
- the distance d4max between the most distant layers is much larger than that of the two-layer stray light incident on the photodetector 120 compared to the case of two layers. Become bigger.
- the magnification (lateral magnification ⁇ ) of the detection optical system is set so that stray light from other layers does not leak into the sub-beam light receiving area 141.
- FIGS. 14A and 14B show the relationship between the distance between the main beam 142 and the sub beam 143 on the photodetector 120 and the size of the other-layer stray light 147.
- FIG. The distance between the main beam 142 and the sub beam 143 on the photodetector 120 is obtained by multiplying the interval between the main beam and the sub beam focused on the track of the information recording layer 202 (see FIG. 1) by the lateral magnification of the detection optical system. Value.
- the distance between the main beam and the sub beam on the track of the information recording layer 202 is 20 ⁇ m and the lateral magnification of the detection optical system is about 6 times
- the distance between the main beam 142 and the sub beam 143 on the photodetector 120 is , About 120 ⁇ m.
- the lateral magnification of the detection optical system is required to be about 10 times with the size of the stray light of the other layer being about 150 ⁇ m.
- the distance between the main beam 142 and the sub beam 143 is about 200 ⁇ m.
- the interval between the main beam and the sub beam on the track of the information layer 202 is set to approximately 20 ⁇ m, but this value is a value that affects the offset of the tracking error when moving from the inner periphery to the outer periphery of the optical disc 201. This value is preset for each device. Generally, 10 ⁇ m to 20 ⁇ m is selected.
- the size of the optical head 200 it is necessary to reduce the size of the detection optical system, but it is necessary to reduce the size of the detection optical system in consideration of the effect of stray light from other layers.
- the focal length of the objective lens 105 is reduced, and thus the surface of the optical disc 201 and the objective lens are reduced.
- the working distance with the lens 105 is shortened. For this reason, it is difficult to realize the focus servo, which is difficult.
- the lateral magnification can be increased without changing the focal length of the objective lens 105, and the size of the detection optical system can be decreased. It becomes possible.
- the lateral magnification of the detection optical system including the objective lens 105, the collimating lens 104, and the concave lens 117 of the cylindrical lens 115 is increased from about 10 times to 20 times. It is desirable that the range be doubled.
- the radius of curvature is about 5 mm to 1 mm ( A lens having an extremely large lens power of 1 mm or more and 5 mm or less is required.
- the detection optical is caused by an error in the relative distance between the cylindrical lens 115 and the light receiving surface 121 of the photodetector 120.
- the lateral magnification of the system changes greatly. Therefore, there is an increased possibility that the sub beam 143 necessary for generating the tracking error signal is incident on a position outside the sub beam receiving area 141. For example, when the distance between the cylindrical lens 115 and the photodetector 120 becomes shorter than a predetermined distance, the lateral magnification of the detection optical system becomes small, and the sub beam 143 approaches the quadrant light receiving region 140 side.
- the cylindrical lens 115 and the photodetector 120 can be accurately positioned in advance with respect to the holder 130 when the position of the detector unit 127 is adjusted. Therefore, when adjusting the position of the photodetector 120 in the XY plane on the optical base 113 and when adjusting the position of the cylindrical lens 115 in the Z direction (optical axis direction), the cylindrical lens 115 with respect to the holder 130 and The relative position error of the photodetector 120 can be greatly reduced. For this reason, the error of the lateral magnification of the detection optical system can be greatly reduced, and the deterioration of the tracking error signal can be greatly reduced.
- the positional error in the Z direction of the cylindrical lens 115 relative to the photodetector 120 is a dimensional error of the holder 130. It becomes only by. Since this dimensional error can be suppressed to about 5 to 20 ⁇ m, the positional error in the Z direction between the cylindrical lens 115 and the photodetector 120 can be reduced to 50 ⁇ m or less.
- the optical head 200 having a large lateral magnification can be adopted for the multilayer optical disc 301, and the optical The head 200 can be reduced in size and performance.
- the cylindrical lens 115 and the photodetector 120 are fixed to the holder 130 in advance, so that the position of the detector unit 127 itself can be adjusted in the XY plane on the optical base 113, and the optical axis. Position adjustment in the direction (Z direction) can also be performed. Thereby, the change of the lateral magnification of a detection optical system can be reduced. For this reason, it is possible to realize a stable recording / reproducing performance of the optical head 200 with little fluctuation in offset of the tracking error signal, and it is possible to realize the optical head 200 having excellent reliability.
- the adjustment amount of the photodetector 120 is different from that of the aperture 131. It is inevitable to give an error to the relative position with respect to the cylindrical lens 115. For this reason, at least a dimensional margin of an opening diameter that is greater than the adjustment amount (generally about 0.05 mm to 1 mm) in a plane orthogonal to the optical axis of the photodetector 120 is required.
- the aperture diameter of the aperture 131 can be reduced.
- FIG. 15A shows an optical head of a comparative example.
- the relative position of the cylindrical lens 115 and the holder 130 changes by adjusting the cylindrical lens 115 in the front-rear direction (Z direction)
- the diameters of the light beams that pass through the aperture 131 in the main beam a and the main beam b. Changes significantly. For this reason, it is necessary to increase the diameter of the aperture 131, and the amount of stray light incident on the sub-beam light receiving region 141 of the photodetector 120 is greatly increased.
- the detector unit 127 is integrally adjusted in the Z direction. For this reason, since the relative distance between the cylindrical lens 115 and the holder 130 does not change, the diameter of the light beam passing through the aperture 131 hardly changes. For this reason, the diameter of the aperture 131 can be reduced to the limit, and the amount of stray light incident on the sub-beam light receiving region 141 of the photodetector 120 can be significantly reduced.
- FIG. 16A shows an optical head of a comparative example.
- the relative positional relationship between the cylindrical lens 115 and the holder 130 is changed by adjusting the photodetector 120 to the left and right (X direction).
- the diameter of the light beam passing through the aperture 131 varies greatly between the main beam a and the main beam b.
- the detector unit 127 moves integrally in the X direction, so the relative distance between the cylindrical lens 115 and the holder 130 does not change.
- the diameter of the light beam passing through the aperture 131 hardly changes. Therefore, the diameter of the aperture 131 can be reduced to the limit, and thereby the amount of stray light incident on the sub-beam light receiving region 141 of the photodetector 120 can be greatly reduced.
- the aperture diameter includes the reflected light beam diameter, the amount of displacement of the cylindrical lens 115 in the X direction (or Y direction) with respect to the aperture 131 of the holder 130, and the X direction (or Y direction) of the photodetector 120 with respect to the aperture 131 of the holder 130.
- the amount of increase in the reflected light beam diameter at the position of the aperture 131 by adjusting the position of the photodetector unit 127 in the Z direction can be made the sum. That is, since the adjustment dimension (about 0.05 mm to 1 mm) in the X direction (or Y direction) of the photodetector unit 127 can be excluded, the aperture diameter can be greatly reduced.
- the aperture 131 has a cylindrical hole shape, but may have a truncated cone shape as shown in FIG. With this configuration, the aperture diameter can be further reduced even when the case where there is a sub-beam 143 incident obliquely is considered.
- the oscillation wavelength of the semiconductor laser 1 serving as the light source can be any of approximately 780 nm for CD, approximately 650 nm for DVD, and approximately 405 nm for BD.
- FIG. 18 shows a configuration example of an optical disc drive 400 as an optical information device to which the optical head 200 is applied.
- the optical disk 201 is sandwiched and fixed by a clamper 401 and a turntable 402, and is rotated by a motor (rotating system) 403 in this state.
- the optical head 200 is placed on a traverse (transfer system) 404 so that the point irradiated with light can move from the inner periphery to the outer periphery of the optical disc 201.
- the control circuit 405 performs focus control, tracking control, traverse control, rotation control of the motor 403, and the like based on a signal received from the optical head 200.
- the signal processing circuit 406 reproduces information from the reproduction signal and outputs the information to the input / output circuit 407, or sends the signal input from the input / output circuit 407 to the optical head 200 through the control circuit 405.
- the optical head 200 having the cylindrical lens 115 with high concave lens power and a large magnification of the detection optical system has a more remarkable effect. Furthermore, since the cylindrical surface 116 of the cylindrical lens 115 is located on the side opposite to the photodetector 120, the performance of the servo signal can be further improved.
- the present invention is applicable regardless of the lens power of the cylindrical lens, and does not prevent application to other optical heads. Even in this case, it is possible to reduce the relative position error between the cylindrical lens and the photodetector.
- the cylindrical lens 115 is made of glass and bonded to a holder made of metal such as zinc or aluminum.
- the cylindrical lens 115 and the holder 130 may be made of resin.
- the structure which integrally molds the cylindrical lens 115 and the holder 130 with resin may be sufficient.
- FIGS. 19A to 19C show the detector unit 127 provided in the second embodiment, and show the relationship between the photodetector 120, the cylindrical lens 115, the holder 130, and the aperture 131.
- FIG. 19A to 19C show the detector unit 127 provided in the second embodiment, and show the relationship between the photodetector 120, the cylindrical lens 115, the holder 130, and the aperture 131.
- the detector unit 127 of this embodiment does not have the photodetector positioning unit 135 and the cylindrical lens positioning unit 136, and the holder 130 of the detector unit 127 includes an aperture 131, a holding unit 132, and a photodetector pressing unit 137. And a cylindrical lens pressing portion 138, a photodetector bonding portion 133, and a cylindrical lens bonding portion 134.
- the relative positional relationship between the aperture 131 and the photodetector 120 is adjusted, and the relative positional relationship between the aperture 131 and the cylindrical lens 115 is adjusted.
- the light receiving surface 121 of the photodetector 120 is adjusted in the X and Y directions with respect to the holding portion 132 and the aperture 131 of the holder 130 on the XY plane, and the angle around the optical axis. ⁇ z is adjusted and then fixed to the holder 130. Thereby, the photodetector 120 is accurately positioned with respect to the holder 130.
- the position adjustment of the cylindrical lens 115 is performed on the holder 130 or the aperture 131 so that the outer shape of the cylindrical lens 115 or the lens optical axis 118 of the cylindrical lens 115 and the center of the aperture 131 coincide.
- This position adjustment is performed by adjusting the positions in the X direction and the Y direction on the XY plane. Further, the angle ⁇ z around the optical axis of the cylindrical lens 115 is adjusted. This adjustment is performed by rotating the cylindrical lens 115 around the optical axis so that the central generatrix 119 of the cylindrical surface 116 is in a predetermined direction.
- the cylindrical lens 115, the aperture 131, and the light receiving surface 121 of the photodetector 120 are accurately positioned and fixed to each other.
- the inner diameter of the aperture 131 can be reduced to the minimum necessary. For this reason, it becomes possible to further block the other layer stray light from the multilayer recording medium incident on the light receiving surface 121 of the photodetector 120.
- the shape of the holder 130 can be reduced, the optical head 200 can be thinned.
- the cylindrical lens 115 is bonded and fixed to the holder 130 at the cylindrical lens bonding portion 134.
- the present invention is not limited to this, and the position of the cylindrical lens 115 is adjusted in the Z-axis direction without pressing the cylindrical lens 115 against the cylindrical lens pressing portion 138. Thereafter, the cylindrical lens bonding portion 134 is bonded and fixed to the holder 130.
- the structure to do may be sufficient.
- 20A to 20C show the configuration of the detector unit 127 provided in the third embodiment.
- a photodetector 120, a cylindrical lens 115, a holder 130, an aperture 131, a four-divided light receiving region 140, and a sub-beam light receiving region 141 are shown.
- the third embodiment is different from the first embodiment in that the shape of the aperture 131 is not cylindrical but non-cylindrical.
- the shape of the aperture 131 is a non-circular cross-sectional shape extending in this direction. ing.
- this non-cylindrical aperture shape With this non-cylindrical aperture shape, the other layer stray light incident on the light receiving surface 121 can be reduced, and more stable focus servo and tracking servo can be realized.
- the shape of the aperture 131 is a rectangular shape.
- a part of the peripheral surface may be an arc-shaped long hole shape, or an elliptical shape or the like. .
- the shape and arrangement of the aperture 131 are different from those in the first to third embodiments.
- FIG. 21A shows the configuration of the optical system of the optical head 200 according to the fourth embodiment.
- the semiconductor laser 101 emits a light beam having an oscillation wavelength of about 405 nm.
- a hologram element 150 is disposed between the beam splitter 103 and the cylindrical lens 115.
- This optical head generates a tracking error signal of a so-called one-beam method (APP method).
- APP method one-beam method
- FIG. 21B shows a configuration of the hologram element 150.
- the solid line in the figure indicates the division pattern of the hologram element 150, and the broken line indicates the cross-sectional shape of the light beam passing through the hologram element 150.
- the hologram element 150 includes a main beam region 151, APP main regions 152 and 153 in which interference light of ⁇ first order light and zero order light diffracted by the information recording layer 202 is incident, and an APP sub region in which only zero order light is incident. Regions 154 and 155.
- FIG. 22A and 22B schematically show a relative positional relationship between the light receiving surface 121 of the photodetector 120 and the aperture 131.
- the light receiving unit 124 of the photodetector 120 includes a circuit unit 122, an adhesive layer 126, and a cover glass 125.
- the light receiving surface 121 is formed with a four-divided light receiving region 140, APP main regions 152 and 153, and APP sub regions 154 and 155.
- the sectoral broken line in FIG. 22B indicates the shape of the aperture 131. That is, in the present embodiment, the light receiving surface 121 has a rectangular shape, and the aperture 131 has a fan shape. The fan-shaped center position is located in the vicinity of one corner of the light receiving surface 121.
- the luminous flux that has passed through each divided region of the hologram element 150 enters the respective light receiving surfaces 121.
- the light beam that has passed through the main region 151 of the hologram element 150 is incident on the four-divided light receiving region 140 of the light receiving surface 121, and the light beam that has passed through the APP main regions 152 and 153 or the APP sub regions 154 and 155 of the hologram element 150 is shown in FIG.
- the light enters the light receiving area (sub-beam light receiving area 141).
- a focus error signal is generated by calculating a difference between the sum signals of the diagonal areas (two difference signals are obtained from the diagonal areas).
- An RF signal is generated from the sum of the signals in each region.
- the tracking error signal is generated from the light reception signal of the sub-beam light receiving region 141. That is, a so-called push-pull signal is generated from the differential of the light beam received by the sub-beam light receiving region 141 (light beam transmitted through the APP main regions 152 and 153), and this signal and the light beam received by the sub-beam light receiving region 141 (APP sub-light). The light receiving signal of the light flux transmitted through the regions 154 and 155) is calculated.
- a tracking error signal is generated by a so-called APP method.
- the quadrant light receiving region 140 and the sub beam light receiving region 141 are arranged at a distance from each other so that other layer stray light does not enter the sub beam receiving region 141. Further, in order to reduce the thickness of the optical head 200, the four-divided light receiving region 140 and the sub-beam light receiving region 141 are not arranged in a straight line but in an L shape on the light receiving surface 121. That is, the four-divided light receiving region 140 is disposed in the vicinity of one corner of the rectangular light receiving surface 121, and the sub-beam light receiving region 141 is disposed in the vicinity of one corner adjacent to the corner, Another sub-beam light receiving region 141 is disposed in the vicinity of the other corner adjacent to the corner.
- the optical axis center coincides with the center of the quadrant light receiving region 140.
- the gravity center positions of the four-divided light receiving area 140 and the sub beam light receiving areas 141 and 141 are the optical axis center position (center position of the aperture 131) and the gravity center of the light receiving surface 121. It is out of position.
- the aperture 131 and the light receiving surface 121 of the photodetector 120 are arranged such that the center (optical axis center) of the four-divided light receiving region 140 coincides with the center of the aperture 131.
- the aperture 131 has a fan shape (non-circular shape), and the center of the fan 131 of the aperture 131 and the center of the four-divided light receiving region 140 (the center of the light beam transmitted through the main beam region 151). The configuration does not match. With this configuration, the aperture 131 can be made as small as possible with respect to the four-divided light receiving region 140 and the sub beam light receiving regions 141 and 141.
- the amount of stray light incident on the light receiving surface 121 and stray light due to surface reflection of the optical element can be significantly reduced. Therefore, the offset of the focus error signal and the tracking error signal can be greatly reduced, and the optical head 200 can be greatly reduced in thickness.
- the stray light incident on the four-divided light receiving region 140, the sub beam light receiving region 141, and the adhesive layer 126 will be described.
- stray light reflected by the surface of the optical disc 201, the surface of the optical element, the surface of the optical base 113, and the like is indicated by arrows. Since the peripheral portion of the aperture 131 is brought close to the vicinity of the four-divided light receiving region 140 and the sub beam light receiving region 141 in the state viewed in the optical axis direction, stray light can be easily blocked by a portion other than the aperture 131 of the holder 130. The incidence of stray light on the quadrant light receiving region 140 and the sub beam light receiving region 141 can be greatly reduced.
- the holder 130 is configured to completely cover the adhesive layer 126 so that the adhesive layer 126 does not protrude inside the aperture 131.
- the adhesive is located in the vicinity of the peripheral edge of the rectangular light receiving surface 121 in the light receiving unit 124.
- the peripheral part of the aperture 131 is located inside the inner edge part of the adhesive seeing in the optical axis direction. Accordingly, the adhesive layer 126 is not irradiated with a light beam having a wavelength of 405 nm.
- the holder 130 shields other-layer stray light that is incident mainly in the diverging system, reflects off the surface of the optical disc 201, the surface of the optical element, the surface of the optical base 113, and the like, and shields stray light that is incident mainly in the converging system. .
- This configuration can suppress the deterioration of the adhesive layer 126 due to irradiation with a light beam having a wavelength of about 405 nm, so that the reliability of the optical head 200 can be greatly improved.
- FIGS. 23A and 23B show the configuration of an optical system provided in the optical head 200 according to the fifth embodiment of the present invention.
- the fifth embodiment is different from the other embodiments in that the cylindrical lens 115 is inclined with respect to the light receiving surface 121 of the photodetector 120.
- a light beam emitted from a semiconductor laser 101 as a light source is separated into a plurality of light beams by a diffraction grating 102.
- the light beam that has passed through the diffraction grating 102 is reflected by the flat plate beam splitter 160, converted into a parallel light beam by the collimator lens 104, and then incident on the objective lens 105.
- the light beam is irradiated onto the optical disc 201 as so-called three-beam convergent light.
- the objective lens 105 is driven in the optical axis direction (focus direction) and the radial direction of the optical disc 201 (radial direction) by an objective lens actuator.
- the light reflected and diffracted by the information recording layer 202 of the optical disc 201 passes through the objective lens 105 again and passes through the plate beam splitter 160.
- the light beam that has passed through the flat beam splitter 160 passes through the cylindrical lens 115 and enters the photodetector 120.
- the holder 130 is formed in a wedge-shaped cross section in which the first main surface (cylindrical lens pressing portion) is an inclined surface 158 inclined with respect to the second main surface (photodetector pressing portion) of the holder 130. Therefore, the plane perpendicular to the lens optical axis 118 of the cylindrical lens 115 is inclined by the angle ⁇ a with respect to the light receiving surface 121 of the photodetector 120.
- the holder 130 is disposed such that the first main surface is inclined in the opposite direction with respect to the direction in which the flat beam splitter 160 is inclined.
- the angle ⁇ a is set to correct the coma aberration of the reflected light beam, and an optimum value of the angle ⁇ a can be set according to the thickness and the angle of the flat optical element arranged in the detection optical system.
- the angle ⁇ a is preferably inclined by about 5 to 20 degrees, more preferably about 5 to 15 degrees.
- the inclination angle ⁇ a is 9.5 degrees.
- the tilt angle ⁇ a of the cylindrical lens 115 can be appropriately set within the above range according to the thickness of the beam splitter 160, that is, the amount of aberration generated in the beam splitter 160.
- the angle ⁇ b indicating the circumferential direction of the central bus bar 119 of the cylindrical surface 116 is set to 45 degrees.
- the flat beam In order to cancel the astigmatism generated in the light beam transmitted through the splitter 160, the angle ⁇ b indicating the circumferential direction of the central bus 119 is set to about 40 to 30 degrees with respect to the X-direction axis in FIG. The range.
- the X direction of Fig.23 (a) is a direction which goes to the direction where the thickness of the holder 130 becomes thin gradually.
- FIGS. 24A to 24C show the configuration of the detector unit 127 provided in the optical head 200 of the fifth embodiment.
- the detector unit 127 includes a photodetector 120, a holder 130 having an aperture 131, and a cylindrical lens 115.
- the photodetector 120 is fixed to the holder 130 and the cylindrical lens 116 is fixed in a state of being pressed against the inclined surface 158 of the holder 130, the lens optical axis 118 of the cylindrical lens 115 is reflected light.
- the angle is fixed at an angle that cancels coma aberration with respect to the axis.
- coma generated in the light beam transmitted through the plate beam splitter 160 can be greatly reduced, and the quality of the light beam incident on the photodetector 120 can be improved. That is, the detection performance of the focus error signal, tracking error signal, and RF signal can be improved.
- the central generatrix 119 of the cylindrical surface 116 of the cylindrical lens 115 has an angle ⁇ b with respect to the axis in the X direction on the light receiving surface 121 of the holder 130 or the photodetector 120 around the lens optical axis 118 of the cylindrical lens 115. Fixed in a rotated state. With this configuration, it is possible to cancel astigmatism that occurs due to transmission through the flat plate beam splitter 160, and it is possible to significantly reduce astigmatism of a light beam incident on the light receiving surface 121.
- the detection performance of the focus error signal, tracking error signal and RF signal can be further improved, and stable focus servo and tracking servo can be realized, and recording / reproduction performance can be greatly improved.
- FIGS. 25A and 25B show the adhesion state between the detector unit 127 and the optical base 113 provided in the sixth embodiment.
- the sixth embodiment is different from the first embodiment in that the holder additional bonding portion 161 is provided on a different surface from the holder bonding portion 139, so that three or more bonding portions between the holder 130 and the optical base 113 are provided. This is the point.
- the holder adhesion part 139 is provided in two places.
- a holder bonding portion 139 and a holder additional bonding portion 161 indicate bonding portions between the holder 130 and the optical base 113.
- the optical base 113 is formed with a through hole 113 a that penetrates in the thickness direction.
- the holder 13 is positioned on one side of the optical base 113 with a portion inserted into the through hole 113 a. A region is provided. A portion located on one side with respect to the optical base 113 is fixed to the optical base 13 by the holder bonding portion 139, and a portion inserted into the through hole 113a is fixed to the optical base 113 by the holder additional bonding portion 161. It is fixed.
- an adhesive is applied to the left and right portions of the holder 130, and the holder 130 is fixed to the optical base 113 by the adhesive portion 139.
- the weight of the cylindrical lens 115 acts as a moment in a direction perpendicular to the paper surface with the holder adhesive portion 139 as a fulcrum when the adhesive structure is used.
- the detector unit 127 may be tilted in the vertical direction (gravity direction) with respect to the holder bonding portion 139 as a fulcrum.
- the optical axis is inclined, the focus and tracking servo signals and the RF signal may be deteriorated.
- the holder additional bonding portion 161 is disposed at a position different from the holder bonding portion 139 in the optical axis direction (Z direction).
- the holder 130 is enlarged in the optical axis direction, and the holder additional bonding portion 161 is provided between the optical base 113 and the holder 130.
- FIG. As shown in the figure, a holder additional adhesive portion 161 may be provided between the cylindrical lens 115 and the optical base 113.
- the holder 130 is formed in a flat plate shape and is not inserted into the through hole 113a of the optical base 113, and the cylindrical lens 115 is disposed in the through hole 113a. Further, as long as the place to be bonded is a place where the moment due to the weight of the cylindrical lens 115 is canceled, another place may be used, and the number of bonded parts may be further increased.
- the light beam from the semiconductor laser 101 as the light source is incident on the photodetector 120.
- the optical head 200 of the seventh embodiment as the first light source, as shown in FIG.
- the light beam from the semiconductor laser 409 enters the photodetector 120, and the light beam from the semiconductor laser 408 as the second light source enters the photodetector 120.
- the semiconductor laser 409 as the first light source is a semiconductor laser that emits a light beam with a wavelength of, for example, 405 nm
- the semiconductor laser 408 as a second light source is a two-wavelength semiconductor laser, for example, with a light beam with a wavelength of 780 nm.
- a light beam having a wavelength of 650 nm can be emitted.
- the optical head 200 of the seventh embodiment includes a diffraction grating 102, a beam splitter 103, a collimator lens 104, an objective lens 105, a flat plate beam splitter 160, a hologram element 150, and a cylindrical element.
- a lens 115, a holder 130, and a photodetector 120 are provided.
- the beam splitter 103 reflects the light beam emitted from the semiconductor laser 408, and the plate beam splitter 160 reflects the light beam emitted from the semiconductor laser 409.
- the hologram element 150 is disposed between the flat beam splitter 160 and the cylindrical lens 115.
- the holder 130 is formed in a wedge-shaped cross section in which the first main surface (cylindrical lens pressing portion) is an inclined surface 158 inclined with respect to the second main surface (photodetector pressing portion) of the holder 130. .
- the plane perpendicular to the lens optical axis 118 of the cylindrical lens 115 is inclined with respect to the light receiving surface 121 of the photodetector 120 by an angle ⁇ a.
- the holder 130 is disposed such that the first main surface is inclined in the opposite direction with respect to the direction in which the flat beam splitter 160 is inclined.
- the optical head of the embodiment includes a light source that emits a light beam, an objective lens that collects the light beam emitted from the light source as convergent light on an information recording medium, and a reflected light beam reflected by the information recording medium.
- a cylindrical lens that generates astigmatism for forming a focus error signal a photodetector that receives a reflected light beam that has passed through the cylindrical lens, and a holder that holds the cylindrical lens and the photodetector
- the holder has a first main surface and a second main surface extending in a direction intersecting the optical axis of the reflected light beam, and the cylindrical lens is bonded to the first main surface, and the light A detector is bonded to the second main surface.
- the photodetector and the cylindrical lens can be integrally adjusted in two orthogonal directions and in the rotational direction, so that It is possible to reduce the occurrence of a relative position error between the cylindrical lens and the photodetector.
- the optical head further includes a collimating lens that changes the parallelism of the light beam from the light source
- the lateral magnification of the detection optical system including the objective lens, the collimating lens, and the cylindrical lens Is preferably 10 times or more.
- the cylindrical lens preferably has a cylindrical surface on the surface on which the reflected light beam is incident and a concave lens surface on the output surface.
- the cylindrical lens and the photodetector are integrated, and the relative positional error between the cylindrical lens and the photodetector is reduced, thereby increasing the detection magnification (lateral magnification) of the detection optical system corresponding to the multilayer optical disk. Configuration can be realized.
- the magnification of the detection optical system can be increased and the size of the detection optical system can be shortened, so that a stable tracking servo that can handle a multilayer optical disk can be realized.
- the optical head can be downsized.
- the cylindrical surface is arranged on the side opposite to the photodetector, a well-balanced focus error signal can be obtained even in a small detection optical system. For this reason, stable focus servo can be realized. Furthermore, since the astigmatic difference can be secured relatively large, a focus error signal with a long pull-in range can be obtained.
- the cylindrical surface is exposed to the outside, so it is easy to adjust the direction of the central bus bar of the cylindrical surface with respect to the dividing direction of the light receiving area of the photodetector using an autocollimator or the like.
- the cylindrical lens and the photodetector can be adjusted integrally in the Z direction (optical axis direction), the change in the magnification of the detection optical system can be reduced, and the offset variation of the tracking error signal is small and stable.
- the recording / reproducing performance of the optical head can be realized.
- the curvature radius of the concave lens surface may be 5 mm or less.
- the cylindrical lens may have a flat surface formed on the exit surface in addition to the concave lens surface.
- the cylindrical lens can be bonded and fixed in a state where the flat surface of the cylindrical lens and the holder are in close contact with each other, an optical head having excellent reliability can be realized.
- the rotation adjustment of the cylindrical lens can be performed in a short time and with high accuracy, so that an optical head with excellent performance can be realized.
- the holder has an aperture at a position where at least a part of the reflected light beam is incident.
- the light beam that has passed through the cylindrical lens can be incident on the photodetector through the aperture of the holder.
- the cylindrical lens, the photodetector, and the holder can be moved integrally to adjust the position, so that the optical axis between the cylindrical lens, the aperture, and the photodetector can be adjusted.
- the relative positional deviation in the direction orthogonal to the direction and the optical axis direction can be reduced.
- the aperture diameter can be reduced, it is possible to reduce the amount of light flux reflected by other layers as stray light and leaking into the photodetector, especially when recording and reproducing information on a multilayer optical disc. .
- the recording / reproducing performance can be improved and the holder can be reduced in size and thickness, so that the optical head can be reduced in size and thickness.
- the aperture includes a size of the reflected light beam, a relative positional error between the cylindrical lens and the aperture, a relative positional error between the cylindrical lens and the aperture, the holder and the cylindrical lens. It is preferable that the dimension corresponds to a value obtained by adding the amount of increase in the dimension of the reflected light beam at the position of the aperture due to the adjustment of the optical detector and the photodetector in the optical axis direction.
- the aperture may have a non-circular cross section.
- the center of the aperture may be arranged at a position different from the center of the reflected optical axis. In this configuration, since the size of the aperture can be further reduced, stray light reaching the photodetector can be reduced.
- the surface roughness of the second main surface to which the photodetector is bonded may be smaller than the surface roughness of the side surface of the holder.
- the surface roughness of the predetermined region including the central portion of the second main surface may be smaller than the surface roughness of the outer peripheral region of the predetermined region on the second main surface.
- the surface roughness of the first main surface to which the cylindrical lens is bonded may be smaller than the surface roughness of the side surface of the holder. In this configuration, since the minute movement is possible at the time of adjusting the position of the cylindrical lens, more accurate positioning is possible.
- the surface roughness of the predetermined region including the central portion of the first main surface may be smaller than the surface roughness of the outer peripheral region of the predetermined region on the first main surface.
- the first main surface to which the cylindrical lens is bonded may be inclined with respect to a plane perpendicular to the reflected optical axis. In this configuration, coma generated in the light beam transmitted through the flat beam splitter can be greatly reduced, and the quality of the light beam incident on the photodetector can be improved.
- the light source emits a light beam having a wavelength of about 405 nm
- the photodetector has a light receiving part, a cover glass, and an adhesive part that bonds the light receiving part and the cover glass.
- the inner end portion of the bonding portion that bonds the photodetector and the second main surface, or the inner end portion of the bonding portion that bonds the light receiving portion and the cover glass is located outside the aperture. It may be arranged. In this configuration, since the adhesive can be prevented from being deteriorated by irradiation with a light beam having a wavelength of about 405 nm, the reliability of the optical head can be greatly improved.
- the fluorescent information device includes the optical head, a transfer unit for transferring the optical head, and a control circuit for controlling the transfer unit and controlling the optical head.
- the optical head device and the optical information device according to the present invention have a stable tracking control function and a function capable of realizing a low information error rate, and are useful as an external storage device of a computer having stable recording / reproducing performance.
- the optical head device and optical information device according to the present invention can also be applied to video recording devices such as DVD recorders, BD recorders, HD-DVD recorders, and video reproducing devices.
- the present invention can be applied to storage devices for car navigation systems, portable music players, digital still cameras, and digital video cameras.
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Abstract
Description
図1は、本発明の第1実施形態による光学ヘッド200の光学系を概略的に示す。なお、図1において、図27に示す構成要素と同じ構成要素については同じ符号を付して説明する。
次に、本発明の第2実施形態による光学ヘッドについて説明する。
次に、本発明の第3実施形態による光学ヘッドについて説明する。
次に、本発明の第4実施形態による光学ヘッド200について説明する。
次に、本発明の第5実施形態について説明する。
次に、本発明の第6実施形態による光学ヘッド200について説明する。
次に、本発明の第7実施形態による光学ヘッド200について説明する。
前記実施形態をまとめると、以下の通りである。
Claims (15)
- 光束を出射する光源と、
前記光源から出射された光束を情報記録媒体に収束光として集光する対物レンズと、
前記情報記録媒体によって反射された反射光束が入射し、フォーカスエラー信号を形成するための非点収差を発生するシリンドリカルレンズと、
前記シリンドリカルレンズを透過した反射光束を受光する光検出器と、
前記シリンドリカルレンズ及び前記光検出器を保持するホルダと、を備え、
前記ホルダは、前記反射光束の光軸と交差する方向にそれぞれ延びる第1主面及び第2主面を有し、
前記シリンドリカルレンズが前記第1主面に接着され、前記光検出器が前記第2主面に接着されている光学ヘッド。 - 請求項1に記載の光学ヘッドにおいて、
前記光学ヘッドは、前記光源からの光束の平行度を変化させるコリメートレンズをさらに備え、
前記対物レンズ、前記コリメートレンズ及び前記シリンドリカルレンズを備えた検出光学系の横倍率が10倍以上であり、
前記シリンドリカルレンズは、前記反射光束が入射する面にシリンドリカル面を有し、出射面に凹レンズ面を有する光学ヘッド。 - 請求項2に記載の光学ヘッドにおいて、
前記凹レンズ面の曲率半径は、5mm以下である光学ヘッド。 - 請求項3に記載の光学ヘッドにおいて、
前記シリンドリカルレンズは、前記出射面に、前記凹レンズ面に加えて平面が形成されている光学ヘッド。 - 請求項1から4の何れか1項に記載の光学ヘッドにおいて、
前記ホルダには、前記反射光束の少なくとも一部が入射する位置にアパーチャが形成されている光学ヘッド。 - 請求項5に記載の光学ヘッドにおいて、
前記アパーチャは、前記反射光束の寸法と、前記シリンドリカルレンズと前記アパーチャとの相対的な位置誤差と、前記シリンドリカルレンズと前記アパーチャとの相対的な位置誤差と、前記ホルダと前記シリンドリカルレンズと前記光検出器とを一体として光軸方向に調整したことによる前記アパーチャの位置での前記反射光束の寸法の増加量と、を加算した値に相当する寸法である光学ヘッド。 - 請求項5又は6に記載の光学ヘッドにおいて、
前記アパーチャの断面が非円形である光学ヘッド。 - 請求項7記載の光学ヘッドにおいて、
前記アパーチャの中心が、前記反射光軸の中心とは異なる位置に配置されている光学ヘッド。 - 請求項1から8の何れか1項に記載の光学ヘッドにおいて、
前記光検出器が接着される前記第2主面の表面粗度が、前記ホルダの側面の表面粗度よりも小さい光学ヘッド。 - 請求項1から9の何れか1項に記載の光学ヘッドにおいて、
前記第2主面の中心部を含む所定領域の表面粗度が、前記第2主面における前記所定領域の外周の領域の表面粗度よりも小さい光学ヘッド。 - 請求項1から10の何れか1項に記載の光学ヘッドにおいて、
前記シリンドリカルレンズが接着される前記第1主面の表面粗度が、前記ホルダの側面の表面粗度よりも小さい光学ヘッド。 - 請求項1から11の何れか1項に記載の光学ヘッドにおいて、
前記第1主面の中心部を含む所定領域の表面粗度が、前記第1主面における前記所定領域の外周の領域の表面粗度よりも小さい光学ヘッド。 - 請求項1から12の何れか1項に記載の光学ヘッドにおいて、
前記シリンドリカルレンズが接着される前記第1主面は、前記反射光軸に垂直な面に対して傾いている光学ヘッド。 - 請求項1から13の何れか1項に記載の光学ヘッドにおいて、
前記光源は約405nmの波長の光束を出射するものであり、
前記光検出器は、受光部と、カバーガラスと、前記受光部及び前記カバーガラスを接着する接着部と、を有し、
前記光検出器と前記第2主面を接着する接着部の内側端部、又は前記受光部と前記カバーガラスとを接着する前記接着部の内側端部が、前記アパーチャよりも外側に配置されている光学ヘッド。 - 請求項1から14の何れか1項に記載の光学ヘッドと、
前記光学ヘッドを移送するための移送部と、
前記移送部の制御及び前記光学ヘッドの制御を行う制御回路と、を備えている光情報装置。
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CN201080001277.6A CN101978423B (zh) | 2009-01-26 | 2010-01-26 | 光学头及光信息装置 |
JP2010547452A JP5566915B2 (ja) | 2009-01-26 | 2010-01-26 | 光学ヘッド及び光情報装置 |
US12/933,899 US8427928B2 (en) | 2009-01-26 | 2010-01-26 | Optical head and optical information device |
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JP2014044764A (ja) * | 2012-08-27 | 2014-03-13 | Funai Electric Co Ltd | 光ピックアップ |
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WO2011161904A1 (ja) * | 2010-06-21 | 2011-12-29 | パナソニック株式会社 | 光学ヘッド及び光情報装置 |
TWI665239B (zh) * | 2014-09-29 | 2019-07-11 | 日商富士軟片股份有限公司 | 組成物、片的製造方法、片、積層體及帶有元件晶圓的積層體 |
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US20110019524A1 (en) | 2011-01-27 |
CN101978423B (zh) | 2014-08-13 |
JP5566915B2 (ja) | 2014-08-06 |
CN101978423A (zh) | 2011-02-16 |
US8427928B2 (en) | 2013-04-23 |
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