JP2012113767A - Optical pickup device and optical information recording and reproducing device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device which is made small so as to be mounted on an optical disk device made to be smaller and thinner, and keep the excellent quality of a signal such as FES and TES for an error of a mounting position of an optical component and the like, and to provide an optical information recording and reproducing device having the same.SOLUTION: In the optical pickup, an optical waveguide element including a two-divided holographic diffraction grating which is divided in at least two regions with a dividing line substantially parallel with a disk radial direction and has a function of adding a predetermined amount of astigmatism with a direction inclined by approximately 45 degrees with respect to the dividing line as a principal axis to positive/negative primary diffracted light, and a photodetector including a plurality of two-divided light receiving surface are arranged in a detection optical system.

Description

  The present invention relates to an optical pickup device and an optical information recording / reproducing device including the same.

  In recent years, along with the downsizing and thinning of optical disk devices, the downsizing of optical pickup devices mounted on the optical disk devices has been rapidly promoted. As a technique of such a small optical pickup device, there is JP-A-2007-66486 (Patent Document 1). This publication states that “a laser light source, a light receiving sensor, a light beam from the first light emitting point that is incident on the light receiving sensor in a substantially focused state, a light beam that is incident after focusing, and a light beam that is incident before focusing. A first hologram to be separated, and a second hologram that separates a light beam from the second light emitting point into a light beam that enters the light receiving sensor in a substantially focused state, a light beam that enters after focusing, and a light beam that enters before focusing. An optical pickup provided with the above "is disclosed, and it is disclosed that stable focus control can be performed even by using two laser light sources provided with light emitting points close to each other.

JP 2007-66486 A

  On the other hand, in recent years, in order to reduce the manufacturing cost of the optical pickup, there is an active movement to automate the assembly work process by actively using an industrial robot or the like. When such an optical pickup apparatus is automatically assembled, the problem that the mounting position accuracy of optical components such as a photodetector is lowered to some extent as compared with the precise assembly adjustment work by a conventional worker is unavoidable. I can't.

  However, when the existing detection means as described above is used to detect a focus error signal (hereinafter referred to as FES) or a tracking error signal (hereinafter referred to as TES), if there is an error in the mounting position of the optical component, Along with this, significant signal quality deterioration such as waveform distortion, amplitude reduction, or control pull-in point offset occurs in each control signal. That is, in order to realize fully automatic assembly of the optical pickup device, a new FES or TES detection means that can maintain the signal quality as good as possible even if an attachment position error occurs in an optical component such as a photodetector. Development is essential.

  In view of the above situation, in the present invention, an optical pickup device in which the FES or TES quality is satisfactorily maintained with respect to a signal deterioration factor such as an attachment position error of an optical component, and the optical pickup apparatus suitable for automation of an optical pickup assembly operation is provided. An optical information recording / reproducing apparatus including the above is provided.

  In order to solve the above problems, for example, the configuration described in the claims is adopted. The present application includes a plurality of means for solving the above-described problems. For example, a laser light source and a laser beam emitted from the laser light source are condensed on the information recording surface of the optical information recording medium. An objective lens that irradiates a focused spot, and reproduces an information signal recorded on the optical information recording medium by irradiating the optical information recording medium with a laser beam or a predetermined information signal on the optical information recording medium An optical waveguide that reflects a laser beam reflected from an information recording surface of a condensing spot and diffracts and emits a 0th-order beam and a ± 1st-order diffracted beam from the laser beam, and an optical waveguide element The optical waveguide element includes a light detector having a plurality of light receiving surfaces that output a light detection signal corresponding to the amount of light received by receiving a 0th-order light beam or a ± 1st-order diffracted light beam of the emitted laser light beam. Wave element The laser beam is divided into at least two divided areas by a dividing line that is substantially perpendicular to the direction corresponding to the recording track direction of the optical information recording medium. The folded light beam and the −1st order diffracted light beam are incident on different predetermined light receiving surfaces within the photodetector, and the + 1st order diffracted light beam and the −1st order diffracted light beam of the laser light beam are directed to the recording track direction or the dividing line. And a function of adding a predetermined amount of astigmatism with the main axis in the direction rotated about 45 degrees around the optical axis.

  According to the present invention, it is possible to realize an optical pickup in which the signal quality of FES and TES is kept good against an attachment position error or the like on an optical component, and an optical information recording / reproducing apparatus including the same.

1 is a schematic component arrangement diagram of an optical pickup device of the present invention. 1 is a schematic plan view showing a first embodiment of an optical waveguide element that is a main component of the present invention. It is a schematic perspective view of the main part of the optical pickup device showing a part of the condensing state of the return light beam emitted from the optical waveguide element and irradiated to the photodetector in the first embodiment. It is a schematic plan view of the main part of the optical pickup device showing an example of the configuration of the light receiving surface of the photodetector in the first embodiment and the condensing state of the light spot irradiated thereon. It is a schematic plan view of the main part of the optical pickup device showing another example of the condensing state of the light spot irradiated on the light receiving surface of the photodetector. It is a schematic plan view of the main part of the optical pickup device showing still another example of the light collection state of the light spot irradiated on the light receiving surface of the photodetector. Schematic showing an example of arithmetic processing for obtaining a predetermined control signal and the like from the arrangement of the light receiving surface of the photodetector and the light spot irradiated thereon and the detection signal obtained from each light receiving surface in the first embodiment It is a top view and a schematic circuit diagram. It is the diagram which showed an example of the amplitude change of FES detected with respect to the position shift of a photodetector. It is the diagram which showed an example of the offset change of TES detected with respect to the position shift of a photodetector. It is a schematic component arrangement | positioning figure which shows the 2nd Example of the optical pick-up apparatus of this invention. It is a schematic plan view which shows the 2nd Example of the optical waveguide element which is main components of this invention. It is a schematic plan view of the main part of the optical pick-up apparatus which showed an example of the structure of the photodetector light-receiving surface in 2nd Example, and the condensing state of the light spot irradiated there.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic component arrangement diagram showing an example of an optical system configuration of an optical pickup device according to the present invention. In the optical pickup 1, for example, a laser light source 2 that houses a semiconductor laser element 10 that emits a laser beam having a wavelength of 650 to 660 nm for DVD recording or reproduction is disposed.

  The light beam 100 emitted from the laser light source 2 reaches the coupling lens 4 through the beam splitter 3, and is converted into a substantially parallel light beam by the coupling lens 4 and then reaches the objective lens 5. Then, the light is condensed by the objective lens 5 and irradiated onto a recording track of a predetermined optical disk 6 such as a DVD to form a light spot. The light beam reflected from the optical disk 6 follows an optical path opposite to that of the incident light beam, passes through the objective lens 5 and the coupling lens 4 again, and reaches the beam splitter 3, and a light beam corresponding to at least a part of the light amount is the beam splitter. 3 is reflected, it becomes a return beam 101 for signal detection and reaches the optical waveguide element 7.

  The optical waveguide element 7 is a main component of this embodiment, and has a function of diffracting a light beam incident on the element in a predetermined direction, such as a diffraction grating. As will be described later, the optical waveguide element 7 is divided into two regions by a predetermined dividing line, and the light beams 101 incident on the divided regions are diffracted at different diffraction angles to detect light. It has a function of leading to different predetermined light receiving surfaces arranged on the device 8.

  In the optical system of the embodiment of FIG. 1 described above, the forward light beam 100 emitted from the laser light source 2 and incident on the disk 6 through the objective lens 5 is transmitted through the beam splitter 3 and reflected by the disk 6, and then the optical waveguide element 7. The return beam 101 that reaches the predetermined light receiving surface on the photodetector 8 through the optical system has an optical system configuration that reflects the beam splitter 3. However, as a matter of course, on the contrary, the configuration in which the forward beam 100 reflects the beam splitter 3 and the return beam 101 passes through the beam splitter 3 may be used in one direction. The beam splitter 3 is not limited to the quadrangular prism as shown in FIG. 1, and may be a flat half mirror disposed obliquely, for example.

  Next, specific examples relating to the optical waveguide element 7 and the photodetector 8 will be described. FIG. 2 is a schematic plan view showing a schematic configuration of the optical waveguide element 7. The optical waveguide element 7 is a diffraction grating provided with a predetermined grating groove on a transparent flat substrate surface. The optical waveguide element 7 extends substantially parallel to a direction substantially perpendicular to the recording track direction of the disk 6 on the lattice plane, that is, a direction corresponding to the disk radial direction (Z-axis direction in the example of FIG. 2). The return light beam 101 is divided into two regions 71 and 72 by a dividing line 73 arranged on or near the central optical axis (indicated by x in the figure). In both of the divided regions, a grating groove is provided so as to diffract the returning light beam 101 incident in both directions in a direction substantially parallel to the dividing line 73, that is, in a direction substantially parallel to the Z-axis direction in the figure.

  However, the pitches of the flat lattice grooves in the two divided regions are different from each other. As described above, the return beam 101 incident on each divided region is diffracted at different diffraction angles and arranged on the photodetector 8. They are guided to different light receiving surfaces. In addition, both the divided areas have a predetermined amount of a principal axis in a predetermined direction 74 inclined with respect to the X-axis and Z-axis in FIG. The arrangement pattern is optimally designed so that astigmatism is added, resulting in a so-called holographic diffraction grating having unequal intervals and curved grating groove patterns.

  For this reason, a + 1st-order diffracted light beam and a −1st-order diffracted light beam are newly generated from the return light beam 101 incident on the optical waveguide element 7 by the diffractive action. For example, as shown in FIG. From the returning light beam 101 incident on the region 71, light beams 102 and 103 are generated as ± first-order diffracted light beams, and are incident on the two-divided light receiving surfaces 82 and 83 among the plurality of light receiving surfaces disposed in the photodetector 8, respectively. The light spots 92 and 93 are formed on the respective light receiving surfaces. On the other hand, as shown in FIG. 3B, light fluxes 104 and 105 are generated from the return light flux 101 incident on the divided region 72 as ± first-order diffracted light flux, and in the photodetector 8 as in the case of the diffracted light fluxes 102 and 103. Are incident on the two-divided light receiving surfaces 84 and 85 to form light spots 94 and 95 on the respective light receiving surfaces.

  However, in the example shown in FIGS. 3A and 3B, the average in both divided regions is such that the diffraction angle of the ± first-order diffracted light beam in the divided region 72 is larger than the diffraction angle in the divided region 71. Since the grating groove pitch is set, the two-divided light receiving surfaces 84 and 85 on which the diffracted light beams 104 and 105 are incident are further returned from the two-divided light receiving surfaces 82 and 83 on which the diffracted light beams 102 and 103 are incident, respectively. 101 is arranged at a position away from the central optical axis.

  Further, a zero-order light beam 106 that passes through the optical waveguide element 7 as it is is also generated from the return light beam 101, and this light beam is a light receiving surface 86 disposed in the photodetector 8 as shown in FIGS. 3 (a) and 3 (b). A light spot 96 is formed by being condensed on the top.

  4 to 6 are schematic plan views showing the arrangement state of the light receiving surface in the photodetector 8 according to the present invention and the condensing state of the light spots 92 to 96 irradiated thereto. 4 shows a case where the light spot on the optical disk is in a just-focus state, and FIG. 5 shows a predetermined amount of the light spot on the disk in a predetermined direction (for example, a direction in which the distance between the objective lens and the disk widens). In the case of defocusing, FIG. 6 shows a case where a predetermined amount is defocused in the opposite direction to FIG.

  As shown in the drawings, in the photodetector 8, the light receiving surfaces 82 to 86 are arranged in a substantially straight line in the Z-axis direction in the drawing, that is, in a direction parallel to the dividing line provided in the optical waveguide element 7. The light receiving surfaces 82 and 84 irradiated with the condensing spots 92 and 94 of the + 1st order diffracted light beam, and the light receiving surfaces 83 and 85 irradiated with the light condensing spots 93 and 95 of the −1st order diffracted light beam, They are arranged at symmetrical positions around the light receiving surface 86 on which the condensed spot of the zero-order light beam is irradiated. Further, these light receiving surfaces 82 to 85 are each divided into two by a dividing line extending substantially parallel to the Z axis direction, that is, the dividing line 73 provided in the optical waveguide element 7, and two independent light receiving regions, ie, 82a and 82b, 83a and 83b, 84a and 84b, and 85a and 85b are formed. The focused spots 92 to 95 are irradiated at the center of the divided light receiving areas, that is, directly above the dividing lines.

  At this time, when the focused spot on the optical disc is in a just-focused state as shown in FIG. 4, the focused spots 92 to 95 each have a substantially semicircular shape. Moreover, due to the influence of astigmatism in the 45-degree direction added by the holographic diffraction grating of the optical waveguide element 7, the cross-sectional shape of the return beam 101 incident on the divided regions 71 and 72 of the optical waveguide element 7 is just light. It has a spot shape that is rotated approximately 90 degrees around the axis. Therefore, for the focused spots 92 to 95, the X-axis direction in the figure corresponds to the radial direction of the disk.

  In addition, at this time, since the condensing spots 92 and 93 and 94 and 95 are in the relationship between the + 1st order diffracted light and the −1st order diffracted light of the same light beam, their phases (wavefronts) are in a conjugate relationship, and are added as a result. The principal axis directions of astigmatism are inclined by 90 degrees. Therefore, for example, when the condensing spots 92 and 94 have a condensing spot shape rotated 90 degrees clockwise in the drawing, the condensing spots 93 and 95 have a shape rotated 90 degrees counterclockwise. Yes. That is, the condensing spots 92 and 93 and 94 and 95 are rotated 180 degrees relatively, and have a spot shape in which the left and right are reversed. Since the condensing spots are arranged and shaped as described above, in the state shown in FIG. 4, for example, the condensing spots detected in the light receiving areas 82a and 82b, 83a and 83b, 84a and 84b, and 85a and 85b, respectively. The detected light amounts of the spots 92 to 95 are almost equal.

  On the other hand, as shown in FIGS. 5 and 6, when the focused spot on the disc is defocused in a predetermined direction, the focused spots 92 to 95 have a large distortion from the semicircular shape as shown in FIG. As shown in the figure, it has a shape that greatly extends in the direction of 45 degrees obliquely with respect to the dividing line of each light receiving surface. Therefore, for example, in the example of FIG. 5, the light receiving area 82a in the light receiving surface 82 has a larger amount of detected light than 82b, and the light receiving area 83a in the light receiving surface 83 has a larger amount of detected light than 83b. .

  On the other hand, in the light receiving surface 84, the detected light amount is larger in the light receiving region 84b than in the light receiving region 84a, and in the light receiving region 85b in the light receiving surface 85, the detected light amount is larger than that in the 83a.

  On the other hand, in the example of FIG. 6 defocused in the opposite direction to the case of FIG. 5, each focused spot is large in the direction of 45 degrees obliquely with respect to the dividing line of each light receiving surface as in FIG. Although extending, the extending direction is symmetric with respect to the dividing line of each light receiving surface with respect to the case of FIG. Therefore, in the case of FIG. 6, in contrast to the case of FIG. 5, the light receiving areas 82b, 83b, 84a, and 85a have a larger amount of light detected than the light receiving areas 82b, 83a, 84b, and 85b.

  A circuit configuration for detecting FES and TES by a predetermined calculation using the characteristics of the shape of each condensing spot on the light receiving surface as described above and the characteristics of the detected light amount change in each divided light receiving area. Is shown in FIG. The light amount detection currents detected from the divided light receiving regions 82a and 82b to 85a to 85b are converted into signal voltages independently by current-voltage converters 302a to 305b, respectively. Now, these signal voltages are represented by S2a to S5b as shown in the figure.

  Each of these signal voltages is arithmetically processed by adders 401 to 404 and subtracters 501 and 502 as shown in the figure, and FES and TES are detected.

That is, FES can be detected from the following arithmetic expression.

  It should be noted that the method of detecting FES by the arithmetic processing as shown in (Equation 1) can basically be regarded as a method using optical characteristics substantially similar to the FES detection by the so-called astigmatism method. Therefore, a detailed description of the FES detection principle in this embodiment is omitted.

On the other hand, as described above, the X direction in the figure corresponds to the radial direction of the disk for the converging spots 92 to 95, and the converging spots 92 and 93 and 94 and 95 are reversed relative to each other. Considering the spot shape, TES can be detected from the following arithmetic expression.

  It should be noted that the technique for detecting TES by the arithmetic processing shown in the above (Equation 2) can be basically regarded as a technique using optical characteristics almost the same as the TES detection by the so-called push-pull method. Therefore, a detailed description of the TES detection principle in this embodiment is omitted.

  In the present embodiment, TES is detected from the reflected light of one light spot irradiated on the disk by a calculation process equivalent to the so-called push-pull method. Of course, other detection means may be used. Absent. For example, in the optical system configuration shown in FIG. 1, a diffraction grating that divides the forward beam 100 into three beams is arranged in the optical path between the laser light source 2 and the beam splitter 3, and three light spots are formed on the optical disk. A so-called differential push-pull method in which the TES is detected by the optical means and the computing means from each of them, and the TES offset due to the tracking displacement of the objective lens is removed or reduced satisfactorily by subtracting them. It is also possible to use it.

  By using the optical means and arithmetic means of the present invention as described above, extremely stable signal quality against error factors such as positional deviation of optical components such as photodetectors, and changes over time. Can detect FES and TES. For example, FIG. 8 is a graph showing an example of the relative change in the FES amplitude with respect to the X-direction positional deviation amount of the light receiving surface of the photodetector. Plots are made for the FES detected by the present invention and the FES detected by the conventional astigmatism method for comparison verification. In both cases, the condensing spot diameter on the light receiving surface is uniform at about 60 μm. As is apparent from the figure, it can be seen that the FES detected by the present invention has a smaller amplitude drop due to the displacement of the light receiving surface of the photodetector, and a better signal is obtained.

  Next, FIG. 9 is a graph showing an example of a change in TES offset with respect to the amount of positional deviation in the X direction of the light receiving surface of the photodetector. Similarly to FIG. 8, this graph also plots the FES detected by the conventional push-pull method for comparison with the present invention.

  As is apparent from the figure, the offset is generated in the TES almost in proportion to the positional deviation of the light receiving surface in the conventional push-pull method, whereas the light receiving surface is displaced in the TES of the present invention. Even with this, almost no offset occurs, and it can be clearly seen that the characteristics are better than those of the conventional method.

  As described above, according to the present invention, even if the light receiving surface of the photodetector is displaced, almost no offset of FES or TES is generated, and the decrease in amplitude is suppressed better than the conventional method. As described above, the converging spots 92 and 93 and 94 and 95 are in phase conjugate relation of ± first-order diffracted light, and the spot patterns at the time of just focus and defocus are mutually relative to the dividing line of the light receiving surface. This is because the other converging spot automatically compensates for the deterioration of the signal detected from one condensing spot because of the symmetrically inverted relationship.

  8 and 9 show changes in the signal characteristics by taking the X-direction positional deviation of the light receiving surface of the photodetector as an example. However, the FES and TES of the present invention are kept good against other error factors. be able to. For example, the positional deviation in the Z direction (perpendicular to the X direction) of the light receiving surface of the photodetector is a positional deviation parallel to the direction in which the light receiving area dividing line extends. As long as the surface does not protrude, there is no signal quality degradation. Further, when the wavelength of the light beam emitted from the laser light source changes, there is a problem that the diffraction angle of ± first-order diffracted light diffracted by the holographic diffraction grating in the optical waveguide element changes. The relative positional shift of the focused spot caused by the above is also a positional shift parallel to the direction in which the light receiving area dividing line extends. Therefore, as a matter of course, there is no deterioration in signal quality unless each focused spot protrudes from the light receiving surface.

  Next, as Example 2, using a multi-laser light source in which two or more laser light sources having different wavelengths are housed in the same package, recording on different disk media such as a DVD and a CD with one optical pickup device. Alternatively, an embodiment of a compatible optical pickup device that realizes reproduction will be described. FIG. 10 is a schematic component arrangement diagram showing an example of the optical system configuration of the optical pickup device in the present embodiment.

  In the optical pickup 11, for example, in addition to the semiconductor laser element 10 that emits a laser beam with a wavelength of 650 to 660 nm for DVD recording or reproduction, a semiconductor that emits a laser beam with a wavelength of 780 nm for recording or reproduction of a CD. A laser light source 2 that houses a laser 12 is disposed. Similar to the light beam 100 emitted from the laser light source 2, the light beam 107 emitted from the laser light source 12 reaches the coupling lens 4 through the beam splitter 3, and is converted into a substantially parallel light beam by the coupling lens 4, and then the objective. Reach lens 5. Then, the light is condensed by the objective lens 5 and irradiated onto a recording track of a predetermined optical disk 6 such as a CD to form a light spot. The light beam reflected from the optical disk 6 follows an optical path opposite to that of the incident light beam, passes through the objective lens 5 and the coupling lens 4 again, and reaches the beam splitter 3, and a light beam corresponding to at least a part of the light amount is the beam splitter. 3 is reflected, it becomes a return beam 108 for signal detection and reaches the optical waveguide element 13.

  FIG. 11 is a schematic plan view showing a schematic configuration of the optical waveguide element 13. The optical waveguide element 13 in the present embodiment not only diffracts the return beam 101, which is a laser beam having a wavelength of 650 to 660 nm, incident on the element, but also diffracts the laser beam having a wavelength of 780 nm that is incident on the element. 2 is different from the optical waveguide element 7 in that the return light beam 108 is also diffracted, but basically has the same configuration as the optical waveguide element 7 of FIG.

  FIG. 12 is a schematic plan view of the main part of the optical pickup device showing an example of the configuration of the light receiving surface of the photodetector and the condensing state of the light spot irradiated thereon in the second embodiment.

  A + 1st order diffracted light beam and a −1st order diffracted light beam are newly generated by the diffraction action from the return light beam 108 incident on the optical waveguide element 13, and among these, the ± 1st order diffracted light beam is generated from the return light beam 108 incident on the divided region 71. Is generated, and is incident on the two-divided light receiving surfaces 82 'and 83 among the plurality of light receiving surfaces disposed in the photodetector 14, respectively, and forms light spots 111 and 112 on each light receiving surface.

  On the other hand, a ± 1st-order diffracted light beam is generated from the return light beam 108 incident on the divided region 72, enters the two-divided light receiving surfaces 84 ′ and 85 arranged in the photodetector 14, and the light spot 113 on each light receiving surface. And 114 are formed. Here, 92 to 96 are light spots of a laser beam having a wavelength band of 650 nm to 660 nm as in the first embodiment.

  However, as in the first embodiment, the average grating groove pitch in both divided regions is set so that the diffraction angle of the ± first-order diffracted light beam in the divided region 72 is larger than the diffraction angle in the divided region 71. The two-divided light receiving surfaces 84 'and 85 on which the diffracted light beam from the divided region 72 is incident are further away from the central optical axis of the return light beam 108 than the two-divided light receiving surfaces 82' and 83 on which the diffracted light beam from the divided region 71 is incident. Placed in position. Further, a zero-order light beam that passes through the optical waveguide element 13 as it is is generated from the return light beam 108 and is condensed on the light receiving surface 86 disposed in the photodetector 14 to form a light spot 115.

  In this embodiment, the laser element 10 that emits a laser beam with a wavelength of 650 to 660 nm and the laser element 12 that emits a laser beam with a wavelength of 780 nm are arranged side by side in the Y-axis direction. Therefore, the positions on the diffraction grating where the respective light beams are incident are positions separated by a predetermined distance in the disk radial direction (Z-axis direction) as shown in FIG. For example, the light spot 115 on which the zero-order light beam is condensed is formed at a position away from the light spot 96 by a predetermined distance.

  In the photodetector 14, the light receiving surfaces 82 to 85 are arranged substantially linearly in the Z-axis direction in the drawing, that is, in a direction parallel to the dividing line provided in the optical waveguide element 14, as in the first embodiment. Further, the condensing spots 111 and 113 of the + 1st order diffracted light beam and the condensing spots 112 and 114 of the −1st order diffracted light beam are formed at substantially symmetrical positions around the condensing spot 115 of the 0th order light beam, respectively. The

  Furthermore, these light receiving surfaces 82 to 85 are each divided into two by a dividing line extending substantially parallel to the Z-axis direction, that is, the dividing line 73 provided in the optical waveguide element 14, and two independent light receiving regions, ie, 82a. 82b, 82'a and 82'b, 83a and 83b, 84a and 84b, 84'a and 84'b, and 85a and 85b. The condensed spots 92 to 96 and 111 to 115 are irradiated directly above the dividing lines of these divided light receiving regions.

  Here, since the diffraction angle by the diffraction grating is proportional to the wavelength, the diffraction angle of the wavelength of the 780 nm band is larger than the diffraction angle of the wavelength of the 650 to 660 nm band. The distance to the light spot is larger in the 780 nm band than in the 650 to 660 nm band. For example, the distance from the light spot 115 to the light spot 114 is larger than the distance from the light spot 96 to the light spot 95, and the distance from the light spot 115 to the light spot 113 is the distance from the light spot 96 to the light spot 94. Bigger than.

  The case where the laser element 10 and the laser element 12 are installed so that the light spot 115 is formed on the + 1st order diffracted light side from the light spot 86 will be described with reference to FIG. In this case, on the + 1st order diffracted light side, the deviation of the light spot formation position caused by the difference between the grating groove pitches of the diffraction grating region 71 and the region 72, and the laser element 10 and the laser element 12 are arranged at a predetermined distance. Therefore, the light spot 93 and the light spot 112 and the light spot 95 and the light spot 114 are relatively formed in a relatively different manner. It will be far away. On the other hand, on the −1st order diffracted light side, the deviation of the light spot formation position caused by the difference in the grating groove pitch between the diffraction grating region 71 and the region 72, and the laser element 10 and the laser element 12 are arranged at a predetermined distance. Since the deviation of the light spot formation position due to the light is offset in the opposite direction, the formation positions of the light spot 92 and the light spot 111 and the formation positions of the light spot 94 and the light spot 113 are relatively close. . For this reason, the light receiving surface can be shared on the minus first-order diffracted light side. For example, in FIG. 12, the light receiving surface that receives the light spot 92 and the light spot 111 is shared by the light receiving surface 82, and the light receiving surface that receives the light spot 94 and the light spot 113 is shared by the light receiving surface 84. Thereby, the number of light receiving surfaces can be reduced. In addition to the above-described examples, modified examples can be considered, but all fall within the scope of the present invention.

1: Optical pickup 2: Laser light source 5: Adaptive objective lens 6: Optical disk 7, 13: Optical waveguide element 8: Photo detectors 82 to 86: Light receiving surface

Claims (8)

A laser light source;
An objective lens that focuses the laser beam emitted from the laser light source and irradiates a focused spot on the information recording surface of the optical information recording medium;
An optical pickup that irradiates the optical information recording medium with the laser beam to reproduce an information signal recorded on the optical information recording medium or record a predetermined information signal on the optical information recording medium. ,
An optical waveguide element that receives a reflected laser beam from the information recording surface of the focused spot and diffracts and emits a zero-order beam and a ± first-order diffracted beam from the laser beam;
A photodetector having a plurality of light receiving surfaces for outputting a light detection signal corresponding to the amount of light received by receiving the 0th order light beam or the ± 1st order diffracted light beam of the laser light beam emitted from the optical waveguide element;
The optical waveguide element has at least two divided areas on the optical waveguide element by a dividing line substantially perpendicular to a direction corresponding to a recording track direction of the optical information recording medium. Depending on the region, the 0th-order light beam, the + 1st-order diffracted light beam, and the −1st-order diffracted light beam are incident on different predetermined light receiving surfaces in the photodetector, and the + 1st-order diffracted light beam and the −1st-order diffracted light beam An optical pickup characterized by adding a predetermined amount of astigmatism with the main axis in the recording track direction or a direction rotated about 45 degrees around the optical axis with respect to the dividing line. The optical pickup according to claim 1,
The optical pickup according to claim 1, wherein the parting line is disposed at least on a substantially central optical axis of a laser beam incident on the optical waveguide element. An optical pickup according to claim 1 or 2,
In the optical waveguide element, the diffraction directions of the + 1st order diffracted light beam and the −1st order diffracted light beam diffracted and emitted for each divided region divided by the dividing line are both substantially perpendicular to the recording track direction or An optical pickup having a direction substantially parallel to the dividing line. An optical pickup according to any one of claims 1 to 3,
2. The optical pickup according to claim 1, wherein the optical waveguide element has different average grating groove pitches for each of the divided regions divided by the dividing line. An optical pickup according to any one of claims 1 to 4,
2. The optical pickup according to claim 1, wherein the optical waveguide element is a holographic diffraction grating in which a curved grating groove pattern is formed at irregular intervals. An optical pickup according to any one of claims 1 to 5,
The optical pickup, wherein the plurality of light receiving surfaces on which the + 1st order diffracted light beam and the −1st order diffracted light beam of the laser light beam are incident are divided into at least two independent light receiving surfaces. An optical pickup according to any one of claims 1 to 6,
An optical pickup characterized in that both a focus control signal and a tracking control signal are generated from the light detection signals obtained from the plurality of light receiving surfaces on which the + 1st order diffracted light beam and -1st order diffracted light beam of the laser light beam are incident. An optical information recording / reproducing apparatus comprising the optical pickup according to claim 7,
The optical detector includes an arithmetic unit for generating both the focus control signal and the tracking control signal inside the optical detector.

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