WO2007105704A1 - 光ディスク装置 - Google Patents
光ディスク装置 Download PDFInfo
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- WO2007105704A1 WO2007105704A1 PCT/JP2007/054883 JP2007054883W WO2007105704A1 WO 2007105704 A1 WO2007105704 A1 WO 2007105704A1 JP 2007054883 W JP2007054883 W JP 2007054883W WO 2007105704 A1 WO2007105704 A1 WO 2007105704A1
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- light
- detection
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- 230000003287 optical effect Effects 0.000 title claims abstract description 162
- 238000001514 detection method Methods 0.000 claims description 263
- 239000000758 substrate Substances 0.000 description 20
- 239000010410 layer Substances 0.000 description 17
- 238000010586 diagram Methods 0.000 description 14
- 230000000694 effects Effects 0.000 description 7
- 101000606504 Drosophila melanogaster Tyrosine-protein kinase-like otk Proteins 0.000 description 3
- 206010041235 Snoring Diseases 0.000 description 2
- 239000012790 adhesive layer Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 201000009310 astigmatism Diseases 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000002355 dual-layer Substances 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
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
- G11B7/0901—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following only
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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
- G11B7/1353—Diffractive elements, e.g. holograms or gratings
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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 disc apparatus used for recording a signal on an optical disc or reproducing a signal recorded on an optical disc.
- Patent Document 1 discloses an optical disc apparatus.
- Patent Document 1 discloses an optical disc apparatus.
- FIG. 1 (a) shows a cross-sectional configuration of a main part of an optical disc apparatus in a conventional example.
- the conventional optical disc apparatus includes a light detection substrate 9 and a light source 1 attached on the light detection substrate 9.
- the light source 1 is, for example, a semiconductor laser.
- this optical disc apparatus includes a collimating lens 4, a polarizing hologram substrate 2 1 ⁇ 4 wavelength plate 3, and an objective lens 5 on the optical path of the laser light la from the light source 1.
- the quarter-wave plate 3 is provided on the back surface of the polarizing holographic substrate 2.
- FIG. 1 (b) is a cross-sectional view showing a configuration in which the light detection substrate 9 of FIG. 1 (a) is cut along a plane that includes the optical path of the laser light la and is perpendicular to the cross section of FIG. 1 (a). It is.
- the light detection substrate 9 is provided with a reflection mirror 10 having a reflection surface inclined by approximately 45 degrees with respect to the substrate surface.
- the laser beam la emitted from the light source 1 toward the reflecting surface of the reflecting mirror 10 is reflected by the reflecting surface, travels toward the collimating lens 4, and is converted into parallel light by the collimating lens 4.
- the parallel light emitted from the collimating lens 4 is transmitted through the polarizing hologram substrate 2, converted from linearly polarized light (S wave or P wave) to circularly polarized light by the quarter wavelength plate 3, and condensed by the objective lens 5. Then, the light is focused on the signal surface 6a of the optical disc 6. The light reflected by the signal surface 6a passes through the objective lens 5 and is converted into linearly polarized light (P wave or S wave) by the quarter wavelength plate 3.
- This linearly polarized light is incident on the hologram surface 2a of the polarizing hologram substrate 2, and is diffracted to be branched into the first-order diffracted light 8 and the first-order diffracted light 8 ′ having the optical axis 7 as the symmetry axis.
- the diffracted light passes through the collimating lens 4 and becomes convergent light, and enters the detection surface 9a of the light detection substrate 9.
- the quarter-wave plate 3 is bonded to the polarizing hologram substrate 2 and is configured in the same casing as the objective lens 5 and moves as a unit.
- the detection surface 9a is positioned substantially at the focal plane position of the collimating lens 4 (that is, the virtual light emitting point position of the light source 1).
- FIG. 7 (a) and FIG. 7 (b) show the configurations of the hologram surface 2a and the detection surface 9a of the conventional optical disk device.
- FIG. 7 (a) is a plan view when the detection surface 9a is viewed from the optical disc 6 side, and shows both the light spots formed on the detection surface 9a.
- FIG. 7 (b) is a plan view when the hologram surface 2a is viewed from the optical disk 6 side.
- the hologram surface 2a is divided into two lines (X-axis and Y-axis) orthogonal to each other at the intersection 20 between the hologram surface 2a and the optical axis 7 in the first quadrant 21 and the second quadrant 22. , Divided into 4 in 3rd quadrant 23 and 4th quadrant 24.
- the Y axis is parallel to the radial direction of the optical disc 6, and the diffracted light 80a, 80b generated by the guide groove formed on the signal surface 6a of the optical disc 6 is included in the return light 80 on the hologram surface 2a. It is shifted and superimposed.
- the outline of the light spot is indicated by a broken line. When this light passes through the hologram surface 2a, ⁇ 1st-order diffracted light is generated, and each diffracted light is divided into four parts and projected onto the detection surface 9a.
- the detection surface 9a is orthogonal to the intersection 90 of the detection surface 9a and the optical axis 7, and two straight lines parallel to the X axis and the Y axis are the X axis,
- trapezoidal tracking detection cells 91, 92, 93, and 94 are arranged on the + side of the y-axis.
- focus detection cells 95 and 96 having a comb shape along the y-axis are alternately arranged.
- the detection cells that are electrically connected are denoted by the same reference numerals, and the same applies to the following description of this specification.
- the outer shape of these detection cells is almost symmetrical with respect to the y-axis.
- the light la emitted from the light emitting point of the light source 1 travels in a plane parallel to the paper surface of FIG. 7 in parallel with the X axis, and is reflected by the reflecting mirror 10 in the optical axis direction (direction passing through the point 90 and perpendicular to the paper surface) Is done.
- the first-order diffracted light diffracted in the first quadrant 21 of the hologram surface 2a is detected in the light spot 81S that fits in the detection cell 91, and the first-order diffracted light is detected.
- the light is condensed on the light spot 81S ′ straddling the boundary between the cell 95 and the detection cell 96, respectively.
- the first-order diffracted light diffracted in the second quadrant 22 enters the light spot 82S that fits in the detection cell 92.
- the light is focused on the light spot 82S ′ straddling the boundary between 5 and the detection cell 96.
- the first-order diffracted light diffracted in the third quadrant 23 is focused on the light spot 83S that fits in the detection cell 93, and the first-order diffracted light is focused on the light spot 83S 'that straddles the boundary between the detection cell 95 and the detection cell 96.
- the first-order diffracted light diffracted in the fourth quadrant 24 is focused on the light spot 84S that fits in the detection cell 94, and the first-time folded light is focused on the light spot 84S ′ that straddles the boundary between the detection cell 95 and the detection cell 96.
- the focal line in the y-axis direction at each condensing spot may be on either side of the detection surface 9a, but the focal line in the X-axis direction is detected when viewed from the hologram surface 2a side for the first-order diffracted light.
- the first-order diffracted light is located in front of the detection surface 9a when viewed from the hologram surface 2a side.
- the focal line in the y-axis direction is aligned with the position of the focal line in the X-axis direction (re, so-called astigmatism, condensing).
- each quadrant of the hologram surface is further divided into strips along the X axis, and the same detection cell 95 and detection cell 96 Light that passes through a single strip area across the boundary is condensed on the back side of the detection surface 9a, and light that passes through the single strip area between them is in front of the detection surface 9a (1 (In the case of the next diffracted light).
- the hologram surface is not divided into strip regions, but the embodiment in which the hologram surface is divided into strip regions also belongs to the technical scope of the present invention. .
- T1 is a signal obtained by the detection cell 91
- T2 is a signal obtained by the detection cell 92
- T3 is a signal obtained by the detection cell 93
- T4 is a signal obtained by the detection cell 94
- F1 is obtained by the detection cell 95.
- the obtained signal, F2 is the signal obtained in the detection cell 96.
- a tracking error signal TE to the track of the optical disc 6 a focus error signal FE to the signal surface 6a of the optical disc 6, and a reproduction signal RF of the signal surface 6a of the optical disc 6 are expressed by the following equation (1 ) To (3).
- TE T1 + T2-T3-T4 ⁇ ⁇ (!)
- FE F1 -F2 '' (2)
- Such a conventional optical disc apparatus has the following problems.
- FIGS. 8 (a) and 8 (b) are diagrams showing the state of the light spot on the detection surface 9a when the focused light is defocused on the signal surface 6a of the optical disc 6 in the conventional example. is there.
- Fig. 8 (a) is a diagram when the signal surface 6a is closer to the objective lens 5 than at the time of focusing
- Fig. 8 (b) is a diagram when the signal surface 6a is farther from the objective lens 5 than at the time of focusing.
- the light spot of the first-order diffracted light is With the point 90 shown in FIG. 7 (a) as the origin, the shape is almost point-symmetric with respect to the light spot of the first-order diffracted light.
- the light spots 81S, 83S, and 84S are connected to the detection senors 92, 94, and 91, respectively.
- the light spots 81S, 82S, and 84S are connected to the detection spots 94, 91, and 93, respectively.
- An object of the present invention is to provide an optical disc device that can be made available.
- an optical disc apparatus is an optical disc apparatus including a light source, a light branching element, an objective lens, and a photodetector, wherein the objective lens is:
- the light source power condenses the emitted light on the signal surface of the optical disc, and the signal The light reflected by the surface is incident on the optical branching element, and the optical branching element is in a first region including an optical axis position of the light incident from the objective lens and in the vicinity of the first region.
- a second region located at a position separated from the optical axis, and splits the light incident on the first region and the light incident on the second region to enter the photodetector.
- a detection surface of the photodetector is provided at a position apart from the first detection region for detecting incident light from the first region of the optical branching element and the first detection region; and A second detection region for detecting incident light of the second region force of the element, and using the detection signal from the second detection region to detect a tracking error signal of the optical disc,
- the disc has a plurality of signal surfaces, the signal surface on which the objective lens is focused Of the light reflected outside the signal surface, the light incident to the photodetector from a first region of said optical branching device is characterized in that it does not enter into the second detection region.
- the photodetector detects a focus error signal of the optical disc using a signal detected in the first detection area.
- the optical branch element is formed so as not to enter the detection region.
- 13_1 which is defined in the range of the signal plane interval 0 111 to 70 111, it is not affected by stray light reflected on the signal plane other than the signal plane that is focused. Stable tracking with small control error is possible.
- the distance between the signal surface on which the objective lens is focused on the optical disk and another signal surface is represented by d, (1 is 20 111 to 30 111).
- the optical branching element is preferably formed so that it does not enter the second detection region, so that the distance between the signal planes is specified in a range of 20! -30 xm. -Stable tracking with small control error is possible without being affected by stray light reflected on the signal surface other than the signal surface that is focused during recording and playback of the Ray disk.
- the d when the distance between the signal surface focused by the objective lens on the optical disk and another signal surface is represented by d, the d is 17 ⁇ m to 23 ⁇ m. (Preferably, when d is 20 xm), the light incident on the photodetector from the first region of the optical branching element is reflected from the other signal surface.
- the optical branching element is formed so as not to enter the second detection region. This prevents the effects of stray light reflected on signal surfaces other than the signal surface that is subject to focusing during HD-DVD recording and playback, where the signal surface interval is specified in the range of 17 / im to 23 ⁇ m. Therefore, stable tracking with a small control error is possible.
- the optical disc apparatus described above has a straight line parallel to the radial direction of the optical disc passing through the origin, with the optical axis position of the light incident on the light detection surface without being branched by the optical branching element as the origin.
- a second detection region in the optical detector is formed along the y-axis
- the first detection region may be divided into two in the X-axis direction so as to sandwich the second detection region.
- the optical disc apparatus described above has a straight line parallel to the radial direction of the optical disc passing through the origin, with the optical axis position of the light incident on the light detection surface without being branched by the light branching element as the origin.
- a first detection region in the photodetector is formed along the y-axis
- the second detection region is Alternatively, the first detection region may be divided into two in the X-axis direction so as to sandwich the first detection region.
- the second detection region includes a first portion having a relatively small length in the X-axis direction and a second portion having a relatively large length. Further, when the length of the first portion in the second detection area in the X-axis direction is expressed as wl and the length of the second portion in the X-axis direction is expressed as w2, Of the light spots formed in the second detection region when the defocus is zero with respect to the signal surface, the light spot located in the second portion is substantially centered in the y-axis direction in the second portion. And, it is preferable to be formed at a position farther than wl / 2 from the y axis.
- the light reflected by the surface other than the signal surface to be recorded / reproduced does not enter the photodetector as stray light at the time of recording / reproduction of the double-layer disc or the multilayer disc. Therefore, a highly accurate tracking error signal can be obtained from the optical signal detected by the photodetector, and stable tracking control with a small error can be realized. Thereby, for example, even if the object lens has an eccentricity along the disk radial direction, it is possible to cancel the off-track generated during tracking control.
- FIG. 1 is a cross-sectional configuration diagram of an embodiment of the present invention and a conventional optical disc apparatus.
- FIGS. 2 (a) and 2 (b) are diagrams showing the configuration of a hologram surface and a detection surface of an optical disc device according to an embodiment of the present invention, together with the arrangement of light spots on these surfaces.
- FIG. 3 (a) and FIG. 3 (b) are explanatory views showing a state of a light spot on a detection surface at the time of defocus in the optical disc apparatus according to one embodiment of the present invention.
- FIGS. 4 (a) and 4 (b) are diagrams showing signal surfaces other than the signal surface to be recorded / reproduced when a multi-layer disc is recorded / reproduced in the optical disc apparatus according to the embodiment of the present invention. Is a diagram for explaining the conditions for preventing the reflected light from reaching the detection surface
- FIG. 5 is a diagram showing a configuration of a detection surface and an optical spot arrangement of an optical disc device that is useful in another embodiment of the present invention.
- FIGS. 7 (a) and 7 (b) show the hologram surface and the detection surface of a conventional optical disk device. Diagram showing configuration with light spot arrangement on each of these surfaces
- FIGS. 8 (a) and 8 (b) are explanatory diagrams of the light spot on the detection surface at the time of defocus in the conventional optical disc apparatus.
- the optical disk apparatus includes a light detection board 9 and a light source 1 attached on the light detection board 9, as in the conventional optical disk apparatus shown in FIG.
- the light source 1 is, for example, a semiconductor laser.
- this optical disk apparatus includes a collimating lens 4, a polarizing hologram substrate 2, a quarter-wave plate 3, and an objective lens 5 on the optical path of the laser light la from the light source 1, as in the conventional optical disk apparatus.
- the quarter-wave plate 3 is provided on the back surface of the polarizing holographic substrate 2.
- the optical disk apparatus according to the present embodiment is different from the conventional optical disk apparatus in the area configuration of the hologram surface 2a of the polarizing hologram substrate 2 and the arrangement of the detection cells on the detection surface 9a of the light detection substrate 9. Yes.
- FIG. 2 (a) and FIG. 2 (b) show the configurations of the hologram surface 2a and the detection surface 9a of the optical disc apparatus that are useful in this embodiment.
- FIG. 2 (a) is a plan view when the detection surface 9a is viewed from the optical disc 6 side.
- FIG. 2 (b) is a plan view when the hologram surface 2a is viewed from the optical disc 6 side.
- the hologram surface 2a of the polarizing hologram substrate 2 is two straight lines (X axis, Y axis) orthogonal to the origin 20 that is the intersection of the hologram surface 2a and the optical axis 7. It is divided into four quadrants 21, 22, 23, 24. Quadrants 21 to 24 extend in the direction of two arcs 71 and 72 line-symmetrical to the X axis and the ends of the arcs 71 and 72 parallel to the Y axis and away from the X axis. Lines 73, 74, 75, and 76, and points 77 and 78 that intersect with arcs 71 and 72 at both ends and perpendicular to the X axis, are divided into three regions.
- the first quadrant 21 is divided into regions 21a, 21b, and 21c.
- the second quadrant 22 is divided into regions 22a, 22b, and 22c.
- the third quadrant 23 is divided into regions 23a, 23b, and 23c.
- Quadrant 24 is demarcated into regions 24a, 24b, and 24c.
- Regions 21c, 22c, 23c, 24c are origin 20 This is the area that touches
- the regions 21a, 22a, 23a, and 24a are regions that are separated from the origin 20 in the X-axis direction, in other words, regions that are adjacent to the regions 21c, 22c, 23c, and 24c in the X-axis direction.
- the regions 21b, 22b, 23b, 24b are regions separated from the origin 20 in the Y-axis direction, in other words, regions adjacent to the regions 21c, 22c, 23c, 24c in the Y-axis direction.
- the saddle axis is parallel to the radial direction of the optical disk 6, and the return light 80 on the hologram surface 2a includes diffracted lights 80a and 80b generated by the guide grooves formed on the signal surface 6a of the optical disk 6. It is shifted and superimposed in the axial direction.
- the outline of the return light from the optical disc 6 when the optical disc 6 is in a narrow pitch format such as DVD-R or DVD-RW is indicated by a broken line.
- ⁇ 1st-order diffracted light is generated.
- Each diffracted light is divided into three regions provided in each of the four quadrants, thereby being divided into 12 lights and projected onto the detection surface 9a of the light detection substrate 9.
- the areas 21a to 21c in the first quadrant 21 have different hologram patterns (grating patterns).
- grating patterns grating patterns
- the detection surface 9a of the light detection substrate 9 is orthogonal to the origin 90, which is the intersection of the detection surface 9a and the optical axis 7, and the X axis and Y axis Focus detection cells 95 and 96 having a comb shape along the y-axis are alternately arranged on the + side of the y-axis with two straight lines parallel to the X-axis and the y-axis.
- the same reference numerals are assigned to the detection cells that are electrically connected.
- tracking detection cells 97 and 98 are arranged in the vicinity of the y-axis.
- the tracking detection cells 97 and 98 are symmetrical with respect to the y axis with the y axis as the boundary line.
- the partial force corresponding to one side of the y-axis protrudes in one direction or the + direction of the X-axis compared to other regions.
- the width in the X-axis direction of the tracking detection cells 97 and 98 is w2Z 2 in the region of height h from the end of the y-axis side in the-direction side. It is wl / 2 in the area on the + direction side of the y axis. Note that w2> wl.
- the focus detection cells 95 and 96 are arranged at positions separated from the tracking detection cells 97 and 98 so as to sandwich the tracking detection cells 97 and 98, and their outer shapes are almost symmetrical with respect to the y-axis. .
- Square detection cells 91, 92, 93, and 94 are distributed on the y-axis side.
- the same reference numerals are assigned to the detection cells that are electrically connected.
- the light la emitted from the light emitting point of the light source 1 travels in the plane parallel to the paper surface of FIG. 2 in parallel to the X axis, and is reflected by the reflecting mirror 10 in the optical axis direction (direction perpendicular to the paper surface through the origin 90). Reflected.
- the first-order diffracted light that diffracts the region 21a of the hologram surface 2a is in the light spot 81S that fits in the tracking detection cell 98, and the first-order diffracted light is in the light spot 81S 'that fits in the detection cell 91, respectively. Condensate. Note that the light spot 81S and the light spot 81S ′ are located symmetrically with respect to the origin 90. Further, the first-order diffracted light that diffracts the region 21b is focused on the light spot 81 ′S that fits in the tracking detection cell 97, and the _first-order diffracted light converges on the light spot 81 ′S that fits in the detection cell 91.
- the light spot 81 ′ S and the light spot 81 ′ S are also symmetric with respect to the origin 90.
- the first-order diffracted light that diffracts the region 21c is focused on the light spot 81 "S across the boundary between the focus detection cells 95 and 96, and the first-order diffracted light is focused on the light spot 81" S 'that fits in the detection cell 91. .
- the first-order diffracted light that diffracts the regions 22a and 22c is the light spot 82S, 82 "S that straddles the boundary between the focus detection cells 95 and 96, and the first-order diffracted light is the light spot that falls within the detection cell 92. Condensed to 82 S 'and 82 "S' respectively.
- the first-order diffracted light that diffracts the region 22b is collected at the light spot 82 ′ S that fits in the detection cell 97, and the ⁇ first-order diffracted light is collected at the light spot 82 ′ S 'that fits in the detection cell 92.
- the first-order diffracted light that diffracts the regions 23a and 23c is in the light spots 83S and 83 "S straddling the boundary between the focus detection cells 95 and 96, and the first-order diffracted light is in the light spot 83 in the detection cell 93. Condensed to S 'and 83 "S' respectively.
- the first-order diffracted light that diffracts the region 23b is focused on the light spot 83 ′ S that fits in the tracking detection cell 98, and the _first-order diffracted light is focused on the light spot 83 ′ S 'that fits in the detection cell 93.
- the first-order diffracted light that diffracts the region 24 a is a light spot that can be accommodated in the tracking detection cell 97.
- the first-order diffracted light is focused on the light spot 84S ′ that fits in the detection cell 94.
- the first-order diffracted light that diffracts the region 24b is focused on the light spot 84 ′ S that fits in the tracking detection cell 98, and the first-order diffracted light is focused on the light spot 84 ′ S that fits in the detection cell 94.
- the first-order diffracted light that diffracts the region 24c is focused on the light spot 84 "S across the boundary between the focus detection cells 95 and 96, and the first-order diffracted light is focused on the light spot 84" S 'that fits in the detection cell 94. To do.
- the first-order diffracted light (condensed spots 81S, 84S, 81, S, 82'S, 83'S, 84'Sf, and so on) are focused light on the detection surface 9a.
- the focal line in the y-axis direction can be on either side of the detection surface 9a, but the focal line in the x-axis direction Is located behind the detection surface 9a when viewed from the hologram surface 2a side, in Fig. 2 (a), the focal line in the y-axis direction is made to coincide with the position of the focal line in the X-axis direction.
- Focusing spots 81S, 84S ', 81'S', 82'S, 83'S ', 84'S' by the 1st-order diffracted light are spots that are focused on the detection surface 9a.
- T1 is a signal obtained by detection cell 91
- T2 is a signal obtained by detection cell 92
- T3 is a signal obtained by detection cell 93
- T4 is a signal obtained by detection cell 94
- F1 is a focus detection cell.
- F2 is the signal obtained in the focus detection cell 96
- S1 is the signal obtained in the tracking detection cell 97
- S2 is the signal obtained in the tracking detection cell 98.
- tracking error signal TE1 to a track of a wide pitch optical disk such as DVD-RAM tracking error signal TE2 to a track of a narrow pitch optical disk such as DVD-R or DVD-RW, Tracking error signal TE3 to the track of a read-only optical disc such as DVD—ROM, focus error signal FE to the signal surface of the optical disc, and playback signal RF to the signal surface of the optical disc are expressed by the following equations (4) to (8).
- TE1 T1 + T2-T3 -T4 (4)
- Light spots 81S and 84S can capture diffracted light components (80a, 80b) from narrow-pitch optical discs such as DVD-R and DVD-RW, resulting in intensity changes due to off-tracking. . This is a phenomenon that occurs due to the interference between so-called zero-order light and diffracted light.
- the light spots 81'S, 82'S, 83'S, and 84'S contain no diffracted light components, so there is no change in intensity due to off-tracking.
- the objective lens 5 is shifted with respect to the optical axis 7 (that is, the Gaussian center of the laser beam) in accordance with the tracking control, the intensity distribution of the return light 80 is also shifted in synchronization with this.
- the intensity center on the holodamal surface 2a is on the ⁇ axis, for example, Y> 0 increases light intensity, ⁇ 0 decreases, or 00 increases light intensity, ⁇ > 0 decreases. Appears as it moves along. Therefore, the light spot 84S and the light spots 81 ′S and 82 ′S have opposite directions of intensity change, and the light spot 81S and the light spots 83 ′S and 84 ′S have opposite directions of change. Therefore, only the off-tracking information can be detected with the signal TE2 with the influence of the objective lens shift canceled. In other words, the signal TE2 can completely cancel the influence of the lens shift of the objective lens 5 on the off-tracking by adjusting the area ratio of the three regions formed in each quadrant of the hologram surface 2a. it can.
- the intensity distribution of the return light 80 is almost uniform in an optical disc of a large pitch format of 1.2 ⁇ m or more such as DVD-RAM. Therefore, the offset of the signal TE1 with a small intensity change due to lens shift of each light spot is also small, and this can be used for tracking error detection.
- DVD-RAM a double-layer disc format has not been proposed, so it is possible to detect a tracking error by the signal TE1, which makes it unnecessary to worry about the effects of stray light.
- FIGS. 3 (a) and 3 (b) show detection surfaces in the present embodiment when the defocus of the collected light with respect to the signal surface of the optical disc 6 is zero and when it is defocused. It is a figure which shows the mode of the light spot on 9a.
- Fig. 3 (a) shows the light spot when the signal surface is closer to the objective lens 5 than when it is in focus
- Fig. 3 (b) shows the objective lens when the signal surface is in focus. This shows the light spot when it is far from 5.
- Fig. 3 (a) shows a light spot reflected by a signal surface (a signal surface with zero defocus) on the optical disc 6 (recorded with a reference symbol P).
- FIG. 6 is a diagram showing a light spot (those with S added to the reference symbol) by reflected light from another signal surface closer to the objective lens 5 than the signal surface.
- FIG. 3 (b) shows a light spot (having a reference sign attached) of reflected light from a signal surface (signal surface with zero defocus) to be recorded and reproduced on the optical disc 6, and the signal surface.
- FIG. 5 is a diagram showing a light spot (having S added to the reference symbol) by reflected light from another signal surface farther from the objective lens 5 than FIG.
- the force representing only the light spot on the first-order diffracted light side-the light spot on the first-order diffracted light side is almost the same as the light spot on the first-order diffracted light side.
- the shape is symmetric with respect to the origin 90.
- no light spot is placed on the detection senor 97 and the detection senor 98 at the time of defocusing.
- the light spot at the point 84 P on the detection cell 97 when the defocus is zero moves in the negative direction of the y axis when the defocus amount exceeds a certain value ( ⁇ 1 in one way).
- the light spot 84S is located outside the detection cell 97.
- the condition of ⁇ 1 will be described later.
- the light spot at the point 81P on the detection cell 98 moves in the + direction of the y axis, and becomes a light spot 81S at a position off the detection cell 98.
- the light spot when the defocus is zero is actually in the vicinity of the focal point on the detection surface 9a, so it forms a complicated shape due to light diffraction, and each quadrant 21 ⁇ Although it is not similar to the overlapping shape with the divided area when passing through the 24 divided areas, it is shown in a circular shape here.
- the reason why these light spots do not remain on the detection cells 97 and 98 is that the light spots 84S and 81S force S are regions separated from the origin 20 in the Y-axis direction on the hologram surface 2a (regions 24b and 21b). And that in the detection cell 98, a part of the y-axis side in the ⁇ direction side protrudes in the + direction of the X axis compared to the + side side of the y axis.
- the point 81P is located at the same point, the point 84P is located near the end of the detection cell 97 on one side of the y axis, and so on.
- the light spot at the point 81'P on the detection cell 97 when the defocus is zero is When the defocus amount exceeds the predetermined value ( ⁇ 1 in one way), it moves in the + direction of the X axis and becomes a light spot 81 ′S at a position off the detection cell 98.
- the light spot at the point 82′P on the detection cell 97 moves in the negative direction of the X axis, and becomes a light spot 8 2 ′S outside the detection cell 97.
- the light spot at the point 83′P on the detection cell 98 moves in one direction of the X axis, and becomes a light spot 83 ′S at a position off the detection cell 97.
- the light spot at the point 84′P on the detection cell 98 moves in the + direction of the X axis, and becomes a light spot 84 ′S at a position off the detection cell 98.
- the reason for the remaining rays on these force S detection senoles 97 and 98 is that the light spots 81, S, 82, S, 83'S and 84'S are separated on the hologram surface 2a by their origin 20 forces in the X-axis direction (region 21a, 2 2a, 23a, 24a) and the x-axis direction of the region where the light spots 81'P, 82'P, 83'P, 84'P are located in the detection cells 97, 98
- the width wl / 2 is small.
- the light spots in the vicinity of the points 81 "P and 84" P on the detection cell 96 are the light spots 81 enlarged toward the + direction of the X axis, respectively. "S, 8 4" S.
- the light spots in the vicinity of the points 82P and 83P on the detection cell 96 are the light spots 82S and 82 "S and the light spots 83S and 83" S that are expanded in one direction from the X car respectively. become.
- Light spot 84 "S, 82S, 82" Si detection snore 97, 98 is expanded in the direction away from force, so it can be applied to detection snore 97, 98 at any defocus amount Hana
- the light spot 81 "S, 83S, 83” Si, the force S that expands toward the detection senor 97, 98, and the detection cell 97, 98 are applied if the defocus amount does not exceed a certain value ( ⁇ 2 in one way) What is it? Even if the conditions of 52 are met, it will be described later.
- no light spot is placed on the detection cell 97 and the detection cell 98 at the time of defocusing.
- the light spot at the point 84P on the detection cell 97 when the defocus is zero exceeds the certain defocus amount ( ⁇ 1 in one way), and moves in the + direction of the y-axis for detection.
- the light spot 84S is located outside the cell 97.
- the light spot at the point 81P on the detection cell 98 moves in one direction of the y axis, and the detection senor 97, 9 It becomes the light spot 81S at a position off 8.
- the reason why these do not remain on the detection cells 97 and 98 is the diffracted light generated in the region (regions 24b and 21b) separated from the origin 20 in the Y-axis direction on the light spot 84S and 81S force hologram surface 2a.
- a part of the y-axis side of the y-direction protrudes in the x-axis direction compared to other areas, and the point 84P is located in this protruding area, and the point 81P It is located near the end of the y-axis side.
- the light spot at the point 81'P on the detection cell 97 when the defocus is zero causes the defocus amount to exceed the predetermined value ( ⁇ 1 in one way), so that the X-axis
- the light spot 81 ′S moves in one direction and is out of the detection cell 97.
- the light spot at the point 82′P on the detection cell 97 moves in the + direction of the X axis and becomes a light spot 82 ′S at a position off the detection cell 98.
- the light spot at the point 83′P on the detection cell 98 moves in the + direction of the X axis, and becomes a light spot 83 ′S at a position off the detection cell 98.
- the light spot at the point 84′P on the detection cell 98 moves in the ⁇ direction of the X axis, and becomes a light spot 84 ′S at a position off the detection cell 97.
- the reason why these forces S does not remain on the detection senor 97, 98 is that the light spots 81'S, 82'S, 83'S, 84'S are separated on the hologram surface 2a from the origin 20 in the X-axis direction (regions 21a, 22a). , 23a, 24a) and the x-axis direction of the region where the light spots 81'P, 82'P, 83'P, 84'P are located in the detection cells 97, 98.
- the width wl / 2 is small.
- the light spots in the vicinity of the point 81 "P and the point 84" P on the detection cell 96 are the light spots 81 "enlarged toward one direction of the X axis, respectively. S, 84 "S.
- the light spots in the vicinity of the points 82P and 83P on the detection cell 96 become the light spots 82S and 82 "S and the light spots 83S and 83" S that are enlarged toward the + direction of the x axis. . Since the light spots 81 "S, 83S, 83, and S expand in the direction away from the detection senor 97 and 98, any defocus amount can be applied to the detection cells 97 and 98.
- Light spot 84 , S, 82S, 82, Sf, detection senor 97, 98, magnifying force S, defocus amount exceeds a certain value ( ⁇ 2 in one way) Otherwise, it will not be applied to the detection cells 97, 98.
- These light spots (81 "S, 82S, 82", 83S, 83 “S, 84” S) force S will not be applied to the detection senor 97, 98 The reason is that their origin (spot position when defocus is zero) Is located at a position away from the detection cells 97 and 98.
- Double-layer discs are commercialized as DVD-R and Blu_Ray discs, etc., and are two-layer structures with two signal surfaces sandwiching an adhesive layer with thickness d and refractive index n.
- the value of d is 40 ⁇ m ⁇ d ⁇ 70 ⁇ m for the DVD-R standard, 20 m d ⁇ 30 ⁇ m for the Blu-Ray standard, and 17 ⁇ m ⁇ d ⁇ 23 ⁇ for the HD-DVD standard. It is stipulated as m.
- this defocus amount (dZn on one side) is within the range of the following equation (9), the light reflected from the signal surface other than the signal surface to be reproduced on the optical disc 6 is detected as stray light in the detection cells 97 and 98. It will not be mixed.
- the size condition of the detection snorets 97 and 98 for preventing the light spot from hitting the detection cells 97 and 98 at the time of defocusing will be described.
- the light spot at point 81P of the detection cell 98 when the defocus is zero is the y-axis when ⁇ 1 defocus occurs in one way.
- the light spot 81S moves in one direction or the + direction.
- the defocus is zero.
- the light spot at the point 84P of the detection cell 98 at the mouth becomes the light spot 84S moved in one direction or the + direction of the y axis when ⁇ 1 defocus occurs in one way.
- the following conditions must be satisfied.
- the light spots 81P and 84P have the length in the y-axis direction of the widened region in the detection senor 97 and 98, as shown in FIG. 4 (a). If h is set, it is preferable that the detection cells 97 and 98 are located at a distance of an end force h / 2 in one direction of the y-axis. These light spots 81P and 84P are located farther from the y-axis than wlZ2 in the wide area of the detection senore 97 and 98.
- the diameter D1 of the fully open spot on the detection surface 9a when the defocus amount is one way ⁇ 1 is obtained from the following equation (10).
- NA is the numerical aperture of the objective lens 5
- fc is the focal length of the collimating lens 4, and is the focal length of the objective lens 5.
- ⁇ l dl / n.
- dl is the minimum interlayer thickness of the dual-layer disc, and is, for example, 40 ⁇ or less for DVD-R or DVD-RW.
- n is the refractive index of the disk substrate of the optical disk 6.
- ⁇ is a distance on the y axis from the origin 20 to the boundary between the region 21c and the region 21b on the hologram surface 2a, as shown in FIG. 4 (b).
- the light spot 81 " ⁇ shown in FIG. 4 (a) is a signal as described with reference to FIG. 3 (a).
- a light spot 81 "S expanded in the + direction of the X-axis is obtained. Even if this light spot is 81" S and the defocus amount is one way ⁇ 2, the detector 97 The condition that does not apply to is that the following equation (13) is satisfied.
- c is the distance in the X-axis direction of the light spot 81 "P force to the detection cell 97.
- ⁇ 2 d2Zn.
- D2 is a two-layer disc. For example, in the case of DVD-R or DVD-RW, it is 70 xm or less D2 is the diameter of the fully open spot on the detection surface 9a when the defocus amount is one way ⁇ 2.
- the light spot 82'P shown in FIG. 4 (a) is the light that has moved in the + direction of the X axis when the signal surface moves away from the objective lens 5. Spot 82, S.
- the condition that this light spot 82'S does not hit the detection cell 98 when the defocus amount is one way ⁇ 1 is that the following equation (14) is satisfied.
- ⁇ is the distance on the X axis from the origin 20 to the boundary between the region 21c and the region 21a on the hologram surface 2a.
- the detection cells for tracking error signals are the detection cells 97, 98, the light spots 84S, 81'S, 82'S on the detection senor 97, and the light spots 81S, 83'S on the detection senor 98.
- the hologram surface 2a is configured so that 84'S is arranged.
- this is merely an example, and various combinations of the arrangement of these light spots on the detection cells 97 and 98 are possible.
- the light source 1 and the detection surface 9a are configured on the same substrate. However, these are configured separately, and further, two collimating lenses are provided and separated on the forward path side and the return path side. There is no change in the effect that can be obtained with the configuration used. [0068] Further, in the above-described embodiment, only the light spots generated from the regions 21a to 24a or the regions 21b to 24b that are regions away from the origin 20 on the hologram surface 2a are collected on the tracking detection cell. It is a feature. If it has the same characteristics, it can produce the same effect in other forms.
- the tracking detection cells 97 and 98 are arranged near the origin of the X axis, and the focus detection cells 95 and 96 are positioned on the + side of the X axis with respect to the tracking detection cells 97 and 98. And placed on one side.
- the detection cells 95 and 96 for detecting the focus error signal are arranged near the origin of the X axis, and the detection cell 97 for detecting the tracking error signal is set to the + side of the X axis and the detection cell 98 is set.
- a configuration that is arranged on the negative side of the X axis is also conceivable.
- FIG. 5 An example of the configuration in this case is shown in FIG. 5 as another embodiment of the present invention.
- Fig. 5 is the same as Fig. 2 except that the positions of the detection cell and the light spot are different.
- FIGS. 6 (a) and 6 (b) show a case where the defocus of the focused light with respect to the signal surface of the optical disk 6 is zero in the case of the detection cell arrangement shown in FIG. It is a figure which shows the mode of the light spot on the detection surface 9a in the case.
- Fig. 6 (a) shows the light spot when the signal surface is closer to the objective lens 5 than when focused
- Fig. 6 (b) shows that the signal surface is farther from the objective lens 5 than when focused. Shows the light spot. That is, FIG.
- FIG. 6 (a) shows a light spot (those with P added to the reference symbol) due to the reflected light from the signal surface to be recorded / reproduced on the optical disc 6 (the signal surface with zero defocus).
- FIG. 6 is a diagram showing a light spot (those with S added to the reference symbol) by reflected light from another signal surface closer to the objective lens 5 than the signal surface.
- Fig. 6 (b) shows an optical spot reflected by a signal surface (signal surface with zero defocus) on the optical disc 6 (recorded with a reference symbol P).
- FIG. 6 is a diagram showing a light spot (those with S added to the reference symbol) by reflected light from another signal surface farther from the objective lens 5 than the signal surface.
- the force representing only the light spot on the first-order diffracted light side _ The light spot on the first-order diffracted light side is almost the same as the light spot on the first-order diffracted light side.
- the shape is symmetric with respect to the origin 90.
- the area division on the hologram surface 2a is not limited to the mode shown in FIG. 2 (b).
- the shape of the regions 21c to 24c in contact with the origin 20 is not limited to the shape as shown in FIG. 2 (b), and may be any shape as long as it is in contact with the origin 20.
- the optical disc apparatus can realize stable tracking control by collecting only the light spots generated from the region away from the origin on the hologram surface on the tracking detector, and is particularly suitable for multilayer optical discs. It can improve the accuracy of recording and playback, and is useful as a device for various optical discs.
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Abstract
Description
Claims
Priority Applications (2)
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US12/282,598 US20090028036A1 (en) | 2006-03-14 | 2007-03-13 | Optical disc device |
JP2008505148A JPWO2007105704A1 (ja) | 2006-03-14 | 2007-03-13 | 光ディスク装置 |
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JP2006-068777 | 2006-03-14 | ||
JP2006068777 | 2006-03-14 |
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WO2007105704A1 true WO2007105704A1 (ja) | 2007-09-20 |
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PCT/JP2007/054883 WO2007105704A1 (ja) | 2006-03-14 | 2007-03-13 | 光ディスク装置 |
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US (1) | US20090028036A1 (ja) |
JP (1) | JPWO2007105704A1 (ja) |
CN (1) | CN101401159A (ja) |
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US7567495B2 (en) | 2006-10-18 | 2009-07-28 | Hitachi Media Electronics Co., Ltd. | Optical pickup apparatus and optical disc apparatus using same |
JP2009170060A (ja) * | 2008-01-21 | 2009-07-30 | Hitachi Media Electoronics Co Ltd | 光ピックアップ装置および光ディスク装置 |
JP2009170087A (ja) * | 2009-03-16 | 2009-07-30 | Hitachi Media Electoronics Co Ltd | 光学ヘッド及びそれを備える光ディスク装置 |
US8064317B2 (en) | 2008-03-04 | 2011-11-22 | Sanyo Electric Co., Ltd. | Optical pickup apparatus and focal-point adjusting method |
US8121013B2 (en) | 2008-09-29 | 2012-02-21 | Sanyo Electric Co., Ltd. | Optical pickup apparatus and optical disc apparatus |
US8345528B2 (en) | 2009-09-01 | 2013-01-01 | Sanyo Electric Co., Ltd. | Optical pickup device |
US8427923B2 (en) | 2009-07-29 | 2013-04-23 | Sanyo Electric Co., Ltd. | Optical pickup device, optical disc device and focus adjusting method |
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KR20140072742A (ko) * | 2012-12-05 | 2014-06-13 | 삼성전자주식회사 | 광 픽업장치 |
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- 2007-03-13 US US12/282,598 patent/US20090028036A1/en not_active Abandoned
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US7567495B2 (en) | 2006-10-18 | 2009-07-28 | Hitachi Media Electronics Co., Ltd. | Optical pickup apparatus and optical disc apparatus using same |
US7885166B2 (en) | 2006-10-18 | 2011-02-08 | Hitachi Media Electronics Co., Ltd. | Optical pick up apparatus with a single beam system and having a diffraction grating |
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US8223613B2 (en) | 2008-01-21 | 2012-07-17 | Hitachi Media Electronics Co., Ltd. | Optical pickup device and optical disc apparatus |
US8547815B2 (en) | 2008-01-21 | 2013-10-01 | Hitachi Media Electronics Co., Ltd. | Optical pickup device and optical disc apparatus |
US8064317B2 (en) | 2008-03-04 | 2011-11-22 | Sanyo Electric Co., Ltd. | Optical pickup apparatus and focal-point adjusting method |
US8121013B2 (en) | 2008-09-29 | 2012-02-21 | Sanyo Electric Co., Ltd. | Optical pickup apparatus and optical disc apparatus |
JP2009170087A (ja) * | 2009-03-16 | 2009-07-30 | Hitachi Media Electoronics Co Ltd | 光学ヘッド及びそれを備える光ディスク装置 |
US8427923B2 (en) | 2009-07-29 | 2013-04-23 | Sanyo Electric Co., Ltd. | Optical pickup device, optical disc device and focus adjusting method |
US8345528B2 (en) | 2009-09-01 | 2013-01-01 | Sanyo Electric Co., Ltd. | Optical pickup device |
Also Published As
Publication number | Publication date |
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CN101401159A (zh) | 2009-04-01 |
JPWO2007105704A1 (ja) | 2009-07-30 |
US20090028036A1 (en) | 2009-01-29 |
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