JP2007164902A - Optical element and optical pickup unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element and an optical pickup unit that can generate three beams suitable for signal processing for tracking servo as to each of a plurality of coherent lights having different wavelengths when the plurality of coherent lights are used, and suitably perform recording to and/or reproduction from optical information recording media corresponding to the respective lights. <P>SOLUTION: A first virtual center line passing a center position in a direction orthogonal to a period direction of a first periodic structure 14 provided on a first grating surface 11 and a second virtual center line passing a center position in a direction orthogonal to a period direction of a first periodic structure 18 provided on a second grating surface 12 deviate from each other in the direction of a deviation between the center of a first light and the center of a second light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical element and an optical pickup device, and more particularly to an optical element and an optical pickup device suitable for performing at least one of recording and reproduction for optical information recording using two coherent lights having different wavelengths. About.

  Conventionally, in various fields such as audio, video, and computers, an optical information recording apparatus and an optical information reproducing apparatus that optically record and reproduce information on an optical information recording medium such as an optical disk have been employed. It was.

  In such an optical information recording apparatus and optical information reproducing apparatus, in order to irradiate the light emitted from the light source (for example, laser light) onto the recording surface of the optical information recording medium through the objective lens, An optical pickup device was used.

  In such an optical pickup device, in order to properly irradiate the light emitted from the light source onto the track formed on the recording surface of the optical information recording medium through the objective lens, the light is caused to follow the track. Was supposed to track.

  In this tracking, the reflected light of the light spot irradiated on the recording surface is detected by a photodetector (PDIC or the like), and a tracking error signal is detected by calculation by this photodetector. .

  Then, according to the tracking error signal, the position of the objective lens is corrected by a servo mechanism.

  As a method for detecting such a tracking error signal, various detection methods such as a DPD method, a three-spot method, a push-pull method, and a differential push-pull method (hereinafter referred to as a conventional DPP method) have been conventionally used. It was.

  Among these, the conventional DPP method is particularly advantageous in reducing tracking error signal offset and tracking even if the objective lens is displaced in the radial direction (radial direction) of the optical disk during tracking. It was.

  In the optical pickup device adopting this conventional DPP method, for example, as shown in FIG. 2 of Patent Document 1, light emitted from the light source is placed on the optical path between the light source that emits laser light and the half mirror. Are diffracted to generate three beams of zero-order light (hereinafter referred to as main beam) and ± first-order light (hereinafter referred to as sub-beam).

  The three beams emitted from the light source are reflected by a half mirror, converted to parallel light by a collimator lens, then condensed by an objective lens, and irradiated as three light spots on the recording surface of the optical disk. The

  At this time, as shown in FIG. 4 of Patent Document 1, when the light spot of the main beam is irradiated onto the guide groove of the recording surface among the three light spots, the light spots of the two sub beams are The guide groove is irradiated onto two adjacent tracks on the inner side and the outer side in the radial direction of the optical disc. On the other hand, when the light spot of the main beam is irradiated onto the track on the recording surface, the light spot of the two sub beams is on the two guide grooves adjacent to the track on the inner side and the outer side in the radial direction of the optical disc. Are irradiated respectively.

  In this way, the irradiation position of each light spot is adjusted by means such as rotating the diffraction grating around the optical axis.

  The reflected light from the three-beam optical disc reaches the half mirror through the objective lens and the collimator lens, and is transmitted by the half mirror and then enters the photodetector through the detection lens.

  With reference to FIG. 4 of Patent Document 1, this photodetector is divided into four divided light receiving surfaces (one) and four divided light receiving surfaces each having four divided light receiving surfaces divided into four by push-pull dividing lines. And two split light receiving surfaces (two). The four-divided light receiving surface corresponds to reference numeral 20a in FIG. 4 of Patent Document 1, and the two-divided light receiving surface corresponds to reference numerals 20b and 20c in FIG.

  Reflected light from the main beam optical disc is incident on the four-divided light receiving surface, and reflected light from the two sub-beam optical discs is incident on the two two-divided light receiving surfaces.

  When three beams of reflected light are incident on each light receiving surface, a detection light spot of each reflected light is formed on each light receiving surface.

  This detection light spot is converted into an electric signal for each divided light receiving surface on each light receiving surface.

  Then, in the above-described four-divided light receiving surface, the sum signal of the electric signals of the two sets of two divided light receiving surfaces is calculated, and this sum signal is subtracted by a subtracter indicated by reference numeral 50a in FIG. Thus, a push-pull signal (hereinafter referred to as a main push-pull signal) for the main beam is detected. This main push-pull signal is indicated by a symbol Sa in FIG.

  Further, in the two split light receiving surfaces described above, the electric signals of the two split light receiving surfaces are subtracted by subtracters indicated by reference numerals 50b and 50c in FIG. The push-pull signal (hereinafter referred to as a sub push-pull signal) is detected. These two sub push-pull signals are indicated by symbols Sb and Sc in FIG.

  Here, the main push-pull signal and the two sub push-pull signals have a phase difference (reverse phase) of 180 °. This is because the push-pull signal waveform of the reflected light from the main beam optical disc and the push-pull signal waveform of the reflected light from the sub-beam optical disc have a phase difference of 180 °.

  The two sub push-pull signals are added by the adder indicated by reference numeral 51 in FIG. 4 of Patent Document 1 and converted into a sum signal, and then the amplifier indicated by reference numeral 52 in FIG. 4 of Patent Document 1 Is amplified by.

  Finally, the sum signal of the sub push-pull signal amplified by the amplifier is subjected to subtraction processing by the subtracter indicated by reference numeral 53 in FIG. 4 of Patent Document 1 with the main push-pull signal. As a result, as shown in FIG. 4 of Patent Document 1, a tracking error signal of the conventional DPP method is detected.

  At this time, even if an offset of the same polarity (positive in FIG. 4 in Patent Document 1) due to the displacement of the objective lens in the radial direction of the optical disk occurs in each push-pull signal, the main push-pull signal and the two Since there is a phase difference of 180 ° with respect to the sub push-pull signal, a tracking error signal in which the offset component is removed and the signal component is amplified is detected.

  However, such a conventional DPP method has a problem that a tracking error signal cannot be detected properly when an optical disk having a different track pitch from that shown in FIG. 4 of Patent Document 1 is used. Yes.

  Therefore, in order to solve such a problem of the conventional DPP method, even when the main beam and the sub beam are irradiated on the same track or guide groove, it is possible to detect the tracking error signal. A method (hereinafter referred to as a first generation inline type DPP method) has been proposed (see, for example, Patent Document 2).

  The characteristic difference between the first generation in-line DPP method and the conventional DPP method is that, as also referred to in FIG. The periodic structure consisting of convex portions and concave portions formed on the other and the periodic structure consisting of convex portions and concave portions formed on the other substantially half surface use a diffraction grating having a phase difference of 180 °.

  If such a diffraction grating is used, as shown in FIG. 6 of Patent Document 1, even in the case of irradiating the light spot of the main beam and the light spot of two sub beams on the same guide groove in the optical disk, the conventional type is used. Similarly to the DPP method, a phase difference of 180 ° can be given between the main push-pull signal and the two sub push-pull signals.

  As a result, the tracking error signal can be detected as in the conventional DPP method.

  However, even in the first generation inline type DPP method, when the objective lens is displaced in the radial direction on the optical disk, the visual field characteristics are such that the amplitude of the tracking error signal is greatly reduced according to the amount of displacement. Has a problem of deterioration.

  Accordingly, a tracking error signal detection method (hereinafter referred to as a second generation inline DPP method) has been proposed that aims to solve the problem of deterioration of visual field characteristics while taking advantage of the first generation inline DPP method. (For example, refer to Patent Document 1).

  The characteristic difference between the second generation inline type DPP method and the first generation inline type DPP method is that, as shown in FIG. 9 of the present application, the first periodic structure 3 including the convex portion 1 and the concave portion 2 A diffraction grating 7 having a grating surface 6 on which three periodic structures 3, 4 and 5 of a second periodic structure 4 and a third periodic structure 5 including a convex portion 1 and a concave portion 2 sandwiching the first periodic structure 3 are used. In the point.

  This diffraction grating 7 is different from the first periodic structure 3 in the phase of the second periodic structure 4 and the third periodic structure 5 by 90 °, and the second periodic structure 4 and the periodic structure of the third periodic structure 5 are different from each other. The phases are 180 ° different from each other.

  If such a diffraction grating 7 is used, it is possible to suppress deterioration of the visual field characteristics even if the objective lens is displaced in the radial direction of the optical disk.

  The diffraction grating 7 used in such a second generation inline DPP method is used for DVD laser light with a wavelength of 660 nm for recording and reproduction on a DVD and for CD with a wavelength of 780 nm for recording and reproduction on a CD. It can be applied to both laser light.

  In this case, if the grating surface 6 shown in FIG. 9 is a DVD grating surface 6 that diffracts a DVD laser beam to generate three beams, the back side of the DVD grating surface 6 in the diffraction grating 7 is provided. As shown in FIG. 10, a CD grating surface 8 having first to third periodic structures 43, 44, and 45 for generating three beams by diffracting CD laser light may be formed on the surface. .

  The first to third periodic structures 43, 44, 45 on the CD grating surface 8 have the same periodic direction as the first periodic structure 3 on the DVD grating surface 6. Further, the second periodic structure 44 and the third periodic structure 45 are each 90 degrees out of phase with the first periodic structure 43, and the second periodic structure 44 and the third periodic structure 45 are out of phase with each other. 180 ° different.

  As described above, if the diffraction grating 7 is a double-sided diffraction grating having three periodic structures 3 to 5 and 43 to 45 on both surfaces in the thickness direction, the laser beam for DVD and the laser beam for CD are used. And both.

  The depth (grating depth) of the concave portion 2 of the grating surface 6 for DVD in the double-sided diffraction grating 7 is determined when the DVD grating surface 6 is irradiated with laser light for DVD. When the laser beam for CD is dispersed and the laser beam for CD is irradiated, the laser beam for CD is formed to such a depth that the laser beam passes through as if there is no recess 2 (lattice).

  On the other hand, the depth (grating depth) of the concave portion 2 of the grating surface 8 for CD in the double-sided diffraction grating 7 is such that when the laser beam for CD is irradiated to the grating surface 8 for CD. When the laser beam for DVD is dispersed and the laser beam for DVD is irradiated, the laser beam for DVD is formed to such a depth that it passes through as if there is no recess 2 (lattice).

JP 2004-145915 A Japanese Patent Laid-Open No. 9-81942

  Conventionally, in an optical pickup device, a DVD laser that emits the above-described DVD laser light (λ = 660 nm) and a CD laser that emits a laser light for CD (λ = 780 nm) are used as a two-wavelength light source. A twin laser in which a laser for use is housed in a single package has been used.

  Such a twin laser is advantageous in reducing the number of parts and the effort for adjusting the optical axis as compared with the case where the DVD laser and the CD laser are separately mounted on the optical pickup device. .

Here, on the grating surface 6 for DVD, in order to appropriately diffract the DVD laser light and generate three beams suitable for signal processing for tracking servo, the center of the DVD laser light is the grating. It is desirable to irradiate one point on the virtual center line CL _DVD passing through the center position in the direction orthogonal to the periodic direction in the first periodic structure 3 of the surface 6 (lateral direction in FIG. 9). This is because it is necessary to irradiate the second periodic structure 4 and the third periodic structure 5 with the same amount of laser light.

Similarly, in order to diffract the CD laser light appropriately on the CD grating surface 8 and generate three beams suitable for signal processing for tracking servo, the center of the CD laser light is the grating. it is desirable that the irradiation to a point on the imaginary center line CL _CD passing through the center position in the direction orthogonal to the periodic direction of the first periodic structure 43 faces 8 (lateral direction in FIG. 10). This is also because it is necessary to irradiate the second periodic structure 44 and the third periodic structure 45 with the same amount of laser light as in the case of the grating surface 6 for DVD.

However, as shown in FIG. 11, in the double-sided diffraction grating 7 of FIGS. 9 and 10, the two virtual center lines CL _DVD and CL _CD are perpendicular to the periodic direction of the first periodic structures 3 and 43 (see FIG. 11 in the horizontal direction), the DVD laser light emission point O _DVD and the CD laser light emission point O _CD in the twin laser 9 are the same distance in the same direction. Just away. Note that the distance between the light emitting points O _DVD and O _CD is about 110 μm.

In other words, the double-sided diffraction grating 7 shown in FIGS. 9 and 10 is such that the center of the DVD laser beam and the center of the CD laser beam are perpendicular to the periodic direction of the first periodic structures 3 and 43. A direction in which two virtual center lines CL _DVD and CL _CD that are desirably irradiated with the center of each laser beam despite being shifted are orthogonal to the periodic direction of the first periodic structures 3 and 43. Are formed at the same position.

In the conventional case where such a double-sided diffraction grating 7 is employed, the center of the DVD laser beam is set so as to appropriately generate three beams of the DVD laser beam with priority on recording / reproduction with respect to the DVD. The double-sided diffraction grating 7 must be arranged so as to intersect with a point on the virtual center line CL _DVD in the first periodic structure 3 of the grating surface 6 for DVD.

  As a result, conventionally, it is not possible to generate three beams suitable for signal processing for tracking servo on the grating surface 8 for CD at the time of recording or reproducing with respect to the CD, resulting in trouble with recording or reproducing with respect to the CD. There was a problem.

  Therefore, the present invention has been made in view of such problems, and when using a plurality of coherent lights having different wavelengths, any of the lights is suitable for signal processing for tracking servo. It is an object of the present invention to provide an optical element and an optical pickup device that can generate a beam and can appropriately perform at least one of recording and reproduction on an optical information recording medium corresponding to each light. is there.

  In order to achieve the above-described object, the optical element according to claim 1 of the present invention is characterized in that each of the first grating surface and the second grating surface has a first periodic structure and the first periodic structure. A second periodic structure formed so as to have a phase different from that of the first periodic structure at a position adjacent in one direction orthogonal to the periodic direction of the first periodic structure with respect to the first periodic structure; A third periodic structure formed so as to have a phase different from at least the first periodic structure at a position adjacent to the periodic structure in the other direction orthogonal to the periodic direction of the first periodic structure. The first virtual center line passing through the center position in the direction orthogonal to the periodic direction in the first periodic structure provided on the first lattice plane, and the first provided on the second lattice plane. In the direction perpendicular to the periodic direction in the periodic structure of A second virtual center line passing through the position is a direction of deviation between the center of the first light and the center of the second light and is orthogonal to the periodic direction of the two first periodic structures. It is in a point shifted in the direction.

  According to the first aspect of the present invention, the first lattice plane and the second lattice plane are the first virtual center in the direction of deviation between the center of the first light and the center of the second light. By having the first to third periodic structures such that the line and the second virtual center line are shifted from each other, it becomes possible to irradiate the center of the first light to one point on the first virtual center line, In addition, the center of the second light can be irradiated to one point on the second virtual center line.

  The optical element according to claim 2 is characterized in that each of the first grating surface and the second grating surface has a first periodic structure and the first periodic structure with respect to the first periodic structure. A second periodic structure formed so as to have a phase different from that of the first periodic structure at a position adjacent in one direction orthogonal to the periodic direction of the first periodic structure with respect to the first periodic structure. The first periodic structure and the first periodic structure are adjacent to each other in one direction orthogonal to the periodic direction of the periodic structure and adjacent to the second periodic structure in the periodic direction of the first periodic structure. A third periodic structure formed to have a phase different from that of the two periodic structures, adjacent to the first periodic structure in the other direction orthogonal to the periodic direction of the first periodic structure, and The first periodic structure with respect to the second periodic structure. A fourth periodic structure formed so as to have a phase different from that of at least the first periodic structure at a position opposed to each other, and in a periodic direction of the first periodic structure with respect to the first periodic structure Adjacent in the other orthogonal direction, and opposed to the third periodic structure with the first periodic structure in between, and further, the first periodic structure of the fourth periodic structure A first periodic structure and a fifth periodic structure formed so as to have a phase different from that of the first periodic structure and the fourth periodic structure at positions adjacent to each other in the periodic direction, and provided on the first lattice plane; A first virtual center line passing through a center position in a direction orthogonal to the periodic direction in the first periodic structure, and a direction orthogonal to the periodic direction in the first periodic structure provided on the second lattice plane. In the second virtual path through the center position The line is at a point shifted from each other in the direction of deviation between the center of the first light and the center of the second light and perpendicular to the periodic direction of the two first periodic structures. .

  According to the second aspect of the present invention, the first lattice plane and the second lattice plane are the first virtual center in the direction of deviation between the center of the first light and the center of the second light. By having the first to fifth periodic structures such that the line and the second virtual center line are shifted from each other, it becomes possible to irradiate the center of the first light to one point on the first virtual center line, In addition, the center of the second light can be irradiated to one point on the second virtual center line.

  Further, the optical element according to claim 3 is characterized in that each of the first grating surface and the second grating surface has a first periodic structure and the first periodic structure with respect to the first periodic structure. Are sequentially formed along the periodic direction of the first periodic structure so as to be adjacent to each other in the periodic direction of the first periodic structure at positions adjacent to each other in one direction orthogonal to the periodic direction of the first periodic structure. A plurality of n-th periodic structures (n: a natural number of 3 or more, the same applies hereinafter), the phases of which are different from those of the first periodic structure, and adjacent to each other in the periodic direction of the first periodic structure The second to nth periodic structures formed so that the phases of the periodic structures are different from each other, and adjacent to the first periodic structure in the other direction orthogonal to the periodic direction of the first periodic structure Around the first periodic structure A plurality of n + 1 to 2n-1 periodic structures sequentially formed along the periodic direction of the first periodic structure so as to be adjacent to each other in the direction, and at least with respect to the first periodic structure The phases are different, and the periodic structures adjacent to each other in the periodic direction of the first periodic structure are formed so that the phases thereof are different from each other. Further, n + k (k: a natural number of 1 to n−1, and so on) ) In the second to nth periodic structures and the n + 1 to 2n-1 periodic structures formed so as to face each other across the first periodic structure; A first virtual center line passing through a center position in a direction perpendicular to the periodic direction in the first periodic structure provided on the first lattice plane, and provided on the second lattice plane. The first The second virtual center line passing through the center position in the direction orthogonal to the periodic direction in the periodic structure is the direction of deviation between the center of the first light and the center of the second light, and the two It is in a point shifted in a direction perpendicular to the periodic direction of the first periodic structure.

  According to the invention of claim 3, the first and second lattice planes have the first virtual center in the direction of deviation between the center of the first light and the center of the second light. It is possible to irradiate the center of the first light to one point on the first virtual center line by having the first to second n-1 periodic structures in which the line and the second virtual center line are shifted from each other In addition, the center of the second light can be irradiated to one point on the second virtual center line.

  Furthermore, the optical pickup device according to claim 4 is characterized in that each of the first grating surface and the second grating surface in the diffractive structure includes the first periodic structure and the first periodic structure. A second periodic structure formed at a position adjacent in one direction orthogonal to the periodic direction of the first periodic structure so that the phase is different from that of the first periodic structure; and And a third periodic structure formed at a position adjacent in the other direction orthogonal to the periodic direction of the first periodic structure so as to have a phase different from that of the first periodic structure. A first virtual center line passing through a center position in a direction perpendicular to the periodic direction in the first periodic structure provided on the first lattice structure; and a first virtual structure provided on the second lattice surface. In the direction perpendicular to the periodic direction A second virtual center line passing through the center position is a direction of deviation between the center of the first light and the center of the second light, and is orthogonal to the periodic direction of the two first periodic structures. It is in the point which is shifted in the direction to do.

  According to the fourth aspect of the present invention, the first lattice plane and the second lattice plane are the first virtual center in the direction of deviation between the center of the first light and the center of the second light. When the diffraction structure has the first to third periodic structures in which the line and the second virtual center line are shifted from each other, the center of the first light can be irradiated to one point on the first virtual center line. It becomes possible, and it becomes possible to irradiate one point on the second virtual center line with the center of the second light.

  The optical pickup device according to claim 5 is characterized in that, in claim 4, the first light source and the second light source are two-wavelength light sources formed integrally with each other. .

  According to the fifth aspect of the present invention, the center of the first light emitted from the two-wavelength light source can be irradiated to one point on the first virtual center line, and the light is emitted from the two-wavelength light source. It becomes possible to irradiate one point on the second virtual center line with the center of the second light.

  Further, the optical pickup device according to claim 6 is characterized in that, in claim 4 or 5, the first optical information recording in which the three beam light spots generated by the first grating surface correspond to the three beams. The same track on the recording surface of the second optical information recording medium corresponding to the three beams is irradiated onto the same track on the recording surface of the medium and the three beam light spots generated by the second grating surface correspond to the three beams. It is in the point irradiated on the top.

  According to the sixth aspect of the present invention, the waveform of the sum signal of the sub push-pull signals corresponding to each of the first light and the second light can be made closer to an ideal waveform. It becomes possible.

  Furthermore, the optical pickup device according to claim 7 is characterized in that each of the first grating surface and the second grating surface in the diffractive structure includes the first periodic structure and the first periodic structure. A second periodic structure formed at a position adjacent in one direction orthogonal to the periodic direction of the first periodic structure so that the phase is different from that of the first periodic structure; and The first periodic structure is adjacent in one direction orthogonal to the periodic direction of the first periodic structure and adjacent to the second periodic structure in the periodic direction of the first periodic structure. A third periodic structure formed in a phase different from that of the periodic structure and the second periodic structure, and the other direction orthogonal to the periodic direction of the first periodic structure with respect to the first periodic structure. Adjacent and the second A fourth periodic structure formed so as to have a phase different from that of at least the first periodic structure at a position opposed to the periodic structure with the first periodic structure interposed therebetween, and the first periodic structure Adjacent in the other direction orthogonal to the periodic direction of the first periodic structure, and opposed to the third periodic structure with the first periodic structure interposed therebetween, and further, the fourth period And a fifth periodic structure formed at a position adjacent to the structure in the periodic direction of the first periodic structure so that the phase is different from at least the first periodic structure and the fourth periodic structure. The first virtual center line passing through the center position in the direction orthogonal to the periodic direction in the first periodic structure provided on the first lattice plane, and the first provided on the second lattice plane. Perpendicular to the periodic direction in the periodic structure of A second virtual center line passing through the center position in the direction is a direction in which the center of the first light and the center of the second light are shifted from each other, and the periodic directions of the two first periodic structures It is in the point which has shifted in the direction orthogonal to.

  According to the seventh aspect of the present invention, the first lattice plane and the second lattice plane are the first virtual center in the direction of deviation between the center of the first light and the center of the second light. When the diffraction structure has the first to fifth periodic structures in which the line and the second virtual center line are shifted from each other, the center of the first light can be irradiated to one point on the first virtual center line. It becomes possible, and it becomes possible to irradiate one point on the second virtual center line with the center of the second light.

  The optical pickup device according to claim 8 is characterized in that, in claim 7, the first light source and the second light source are two-wavelength light sources formed integrally with each other. .

  According to the eighth aspect of the present invention, the center of the first light emitted from the two-wavelength light source can be irradiated to one point on the first virtual center line, and the light is emitted from the two-wavelength light source. It becomes possible to irradiate one point on the second virtual center line with the center of the second light.

  Furthermore, the optical pickup device according to claim 9 is characterized in that, in claim 7 or 8, the first optical information recording in which the three beam light spots generated by the first grating surface correspond to the three beams. The same track on the recording surface of the second optical information recording medium corresponding to the three beams is irradiated onto the same track on the recording surface of the medium and the three beam light spots generated by the second grating surface correspond to the three beams. It is in the point irradiated on the top.

  According to the ninth aspect of the invention, the waveforms of the sum signals of the sub push-pull signals corresponding to the first light and the second light can be made to be waveforms that are closer to ideal. It becomes possible.

  Furthermore, the optical pickup device according to claim 10 is characterized in that each of the first grating surface and the second grating surface in the diffractive structure includes the first periodic structure and the first periodic structure. Sequentially formed along the periodic direction of the first periodic structure at adjacent positions in one direction orthogonal to the periodic direction of the first periodic structure so as to be adjacent to each other in the periodic direction of the first periodic structure A plurality of periodic structures of the second to n-th (n: natural number of 3 or more, the same shall apply hereinafter), the phases of which are different from those of the first periodic structure, and the period of the first periodic structure The second to nth periodic structures formed so that the phases of the periodic structures adjacent to each other in the direction are different from each other, and the other perpendicular to the periodic direction of the first periodic structure with respect to the first periodic structure Adjacent in the direction of A plurality of periodic structures of (n + 1) to (2n-1) sequentially formed along the periodic direction of the first periodic structure so as to be adjacent to each other in the periodic direction at the position. , At least with respect to the first periodic structure, and the periodic structures adjacent to each other in the periodic direction of the first periodic structure are different from each other, and further, n + k (k: 1 to n-1 or less natural number (same below) periodic structures are formed to face each other across the first periodic structure with the k + 1-th periodic structure in the second to n-th periodic structures A first virtual center line that passes through a center position in a direction perpendicular to the periodic direction in the first periodic structure provided on the first lattice plane, and at least an n + 1 to 2n-1 periodic structure The above A second virtual center line passing through a center position in a direction orthogonal to the periodic direction in the first periodic structure provided on the two lattice planes, the center of the first light and the second light This is in the direction of deviation from the center and in the direction perpendicular to the periodic direction of the two first periodic structures.

  According to the tenth aspect of the present invention, the first lattice plane and the second lattice plane are the first virtual center in the direction of deviation between the center of the first light and the center of the second light. The diffraction structure has the first to second n-1 periodic structures in which the line and the second virtual center line are shifted from each other, so that the center of the first light is irradiated to one point on the first virtual center line. In addition, it is possible to irradiate one point on the second virtual center line with the center of the second light.

  The optical pickup device according to claim 11 is characterized in that, in claim 10, the first light source and the second light source are two-wavelength light sources formed integrally with each other. .

  According to the eleventh aspect of the present invention, the center of the first light emitted from the two-wavelength light source can be irradiated to one point on the first virtual center line, and the light is emitted from the two-wavelength light source. It becomes possible to irradiate one point on the second virtual center line with the center of the second light.

  Furthermore, the optical pickup device according to a twelfth aspect of the present invention is the optical pickup device according to the tenth or eleventh aspect, wherein the three optical spots generated by the first grating surface correspond to the three beams. The same track on the recording surface of the second optical information recording medium corresponding to the three beams is irradiated onto the same track on the recording surface of the medium and the three beam light spots generated by the second grating surface correspond to the three beams. It is in the point irradiated on the top.

  According to the twelfth aspect of the present invention, the waveform of the sum signal of the sub push-pull signals corresponding to each of the first light and the second light can be made closer to an ideal waveform. It becomes possible.

  According to the present invention, it is possible to irradiate one point on the first virtual center line with the center of the first light, and to irradiate one point on the second virtual center line with the center of the second light. As a result, when a plurality of coherent lights having different wavelengths are used, three beams suitable for signal processing for tracking servo can be generated for any of the lights, and optical information corresponding to each light can be generated. It is possible to appropriately perform at least one of recording and reproduction on the recording medium.

  According to the present invention, any light emitted from the two-wavelength light source can generate three beams suitable for signal processing for tracking servo, and an optical information recording medium corresponding to each light It is possible to appropriately perform at least one of recording and reproduction with respect to.

  Furthermore, according to the present invention, the waveform of the sum signal of the sub push-pull signals corresponding to each of the first light and the second light can be made closer to the ideal waveform. It is possible to more appropriately perform at least one of recording and reproduction with respect to the optical information recording medium corresponding to the above.

  Hereinafter, embodiments of an optical element and an optical pickup device according to the present invention will be described with reference to FIGS.

(First Embodiment of Optical Element)
As shown in FIGS. 1 and 2, the optical element 10 in the present embodiment has a predetermined thickness in a direction perpendicular to the paper surface in FIGS.

  The optical element 10 in the present embodiment has a DVD grating surface 11 as a first grating surface formed on the front surface in the thickness direction, and a second surface on the back surface in the thickness direction. The double-sided diffraction grating is formed with a CD grating surface 12 as a grating surface.

  As shown in FIG. 1, the DVD grating surface 11 has a first periodic structure 14 for DVD as a first periodic structure in which a plurality of convex portions 14a and concave portions 14b are alternately arranged along the vertical direction in FIG. have.

  A position adjacent to the first periodic structure for DVD 14 in one direction (left direction in FIG. 1) perpendicular to the periodic direction (vertical direction in FIG. 1) of the first periodic structure 14 for DVD is A second periodic structure 15 for DVD is formed as a second periodic structure whose phase is 90 ° different from that of the one periodic structure 14.

  Similar to the first periodic structure 14 for DVD, the second periodic structure 15 for DVD is formed by arranging a plurality of convex portions 15a and concave portions 15b in the vertical direction in FIG.

  Further, the phase of the second periodic structure 15 for DVD is −90 ° when the phase of the first periodic structure 14 for DVD is 0 °.

  At the position adjacent to the first periodic structure 14 for DVD in the other direction (right direction in FIG. 1) orthogonal to the periodic direction of the first periodic structure 14 for DVD, the third periodic structure for DVD is provided. A three-period structure 16 is formed.

  The third periodic structure 16 for DVD is formed by arranging a plurality of convex portions 16a and concave portions 16b in the vertical direction in FIG.

  Further, the third periodic structure for DVD 16 has a phase difference of 90 ° (+ 90 °) with respect to the first periodic structure for DVD 14 and a phase difference of 180 ° with respect to the second periodic structure for DVD 15. Is formed.

  Such a grating surface 11 for DVD diffracts coherent light (hereinafter referred to as DVD light) having a wavelength of 660 nm corresponding to DVD as the coherent first light emitted from the light source, thereby diffracting the main beam (referred to as DVD light). Three beams for DVD composed of zero-order light) and two sub-beams (± first-order light) are generated.

  According to the DVD grating surface 11 on which such three periodic structures 14, 15, 16 are formed, as the periodic structures 3, 4, 5 shown in FIG. 9, the first optical information recording medium is used. Even when the objective lens arranged immediately before the DVD is displaced in the radial direction of the DVD during recording or reproduction of the DVD, it is possible to suppress the deterioration of the visual field characteristics.

  On the other hand, as shown in FIG. 2, the CD grating surface 12 has a first period for CD as a first periodic structure in which a plurality of convex portions 18a and concave portions 18b are alternately arranged along the vertical direction in FIG. It has a structure 18.

  At the position adjacent to the first periodic structure for CD 18 in one direction (right direction in FIG. 2) orthogonal to the periodic direction (vertical direction in FIG. 2) of the first periodic structure 18 for CD, A CD second periodic structure 19 is formed as a second periodic structure whose phase is 90 ° different from that of the one periodic structure 18. Note that the second periodic structure 19 for CD is adjacent to the first periodic structure 18 for CD in the left direction when viewed from the surface side of the CD grating surface 12.

  Similar to the first periodic structure 18 for CD, the second periodic structure 19 for CD is formed by arranging a plurality of convex portions 19a and concave portions 19b in the vertical direction in FIG.

  Further, the phase of the second periodic structure 19 for CD is −90 ° when the phase of the first periodic structure 18 for CD is 0 °.

  At the position adjacent to the first periodic structure for CD 18 in the other direction (left direction in FIG. 2) orthogonal to the periodic direction of the first periodic structure for CD, the third periodic structure for CD is provided. A three-period structure 20 is formed.

  The third periodic structure 20 for CD is formed by arranging a plurality of convex portions 20a and concave portions 20b in the vertical direction in FIG.

  Further, the third periodic structure 20 for CD is 90 ° (+ 90 °) different in phase from the first periodic structure 18 for CD and 180 ° different in phase from the second periodic structure 19 for CD. Is formed.

  Such a CD grating surface 12 diffracts coherent light (hereinafter referred to as CD light) having a wavelength of 780 nm corresponding to CD as coherent second light emitted from the light source, thereby diffracting the main beam (referred to as CD light). Three beams for CD composed of zero-order light) and two sub beams (± first-order light) are generated.

  According to the CD grating surface 12 on which the three periodic structures 18, 19, and 20 are formed, as the periodic structures 43, 44, and 45 shown in FIG. 10, the second optical information recording medium is used. Even when the objective lens arranged immediately before the CD is displaced in the radial direction of the CD during recording or reproduction of the CD, it is possible to suppress the deterioration of the visual field characteristics.

As shown in FIGS. 1 to 3, in the present embodiment, the DVD-side virtual center line CL _DVD (first virtual center line) passing through the center position in the direction orthogonal to the periodic direction in the first periodic structure 14 for _DVD . And the CD-side virtual center line CL _CD (second virtual center line) passing through the center position in the direction orthogonal to the periodic direction in the first periodic structure 18 for CD is the first periodic structure 14, 18 for DVD, CD. Are shifted from each other in a direction perpendicular to the periodic direction (lateral direction in FIG. 3).

Here, the direction of deviation between the DVD-side virtual center line CL _DVD and the CD-side virtual center line CL _CD is the deviation between the center of the DVD light emitted from the two-wavelength light source 22 such as a twin laser and the center of the CD light. Equal to direction.

The deviation between the center of the DVD light and the center of the CD light is caused by the fact that the light emission point O _DVD of the DVD light and the light emission point O _{CD of the} CD light in the two-wavelength light source 22 are separated.

  The deviation between the center of the DVD light and the center of the CD light is not limited to the case of the two-wavelength light source 22, and the DVD light source and the CD light source are separately arranged so It can also occur when guiding.

As described above, the optical element 10 according to the present embodiment has a period in which the DVD-side virtual center line CL _DVD and the CD-side virtual center line CL _CD are shifted from each other in the direction of deviation between the center of the DVD light and the center of the CD light. By having the structures 14, 15, 16, 18, 19, and 20, the center of the DVD light can be irradiated to one point on the DVD side virtual center line CL _DVD , and the center of the CD light is set to the CD side virtual center. A point on the line CL _CD can be irradiated.

  As a result, the second periodic structure 15 for DVD and the third periodic structure 16 for DVD can be irradiated with the same amount of DVD light, which is suitable for signal processing for tracking servo on the grating surface 11 for DVD. 3 beams for DVD can be generated.

  Similarly, since the CD second periodic structure 19 and the third CD periodic structure 20 can be irradiated with the same amount of CD light, the CD grating surface 12 is suitable for signal processing for tracking servo. 3 beams for CD can be generated.

(Second Embodiment of Optical Element)
As shown in FIGS. 4 and 5, the optical element 25 in the present embodiment has a predetermined thickness in a direction orthogonal to the paper surface in FIGS. 4 and 5.

  As in the first embodiment, the optical element 25 in the present embodiment has a DVD grating surface 26 as a first grating surface formed on the front surface in the thickness direction, and is located on the back side in the thickness direction. A double-sided diffraction grating having a CD grating surface 27 as a second grating surface is formed on the surface.

  However, in the present embodiment, the specific configuration of each of the lattice surfaces 26 and 27 is different from that of the first embodiment.

  That is, as shown in FIG. 4, the DVD grating surface 26 has a first period for DVD as a first periodic structure in which a plurality of convex portions 29a and concave portions 29b are alternately arranged along the vertical direction in FIG. It has a structure 29.

  At the position adjacent to the first periodic structure 29 for DVD in one direction (left direction in FIG. 4) orthogonal to the periodic direction (vertical direction in FIG. 4) of the first periodic structure 29 for DVD, A second periodic structure 30 for DVD is formed as a second periodic structure whose phase is 90 ° different from that of the one periodic structure 29.

  Like the first periodic structure 29 for DVD, the second periodic structure 30 for DVD is formed by alternately arranging a plurality of convex portions 30a and concave portions 30b along the vertical direction in FIG. . That is, the periodic direction of the second periodic structure 30 for DVD is parallel to the periodic direction of the first periodic structure 29 for DVD.

  Further, the phase of the second periodic structure 30 for DVD is −90 ° when the phase of the first periodic structure 29 for DVD is 0 °.

  It is adjacent to the first periodic structure 29 for DVD in one direction (left direction in FIG. 4) orthogonal to the periodic direction of the first periodic structure 29 for DVD and is DVD to the second periodic structure 30 for DVD. A third periodic structure 31 for DVD is formed at a position adjacent to the first periodic structure 29 for use in the periodic direction (vertical direction (downward) in FIG. 4).

  The third periodic structure 31 for DVD is formed by alternately arranging a plurality of convex portions 31a and concave portions 31b along the vertical direction in FIG. That is, the periodic direction of the third periodic structure 31 for DVD is also parallel to the periodic direction of the first periodic structure 29 for DVD.

  Further, the third periodic structure 31 for DVD is 90 ° (+ 90 °) out of phase with the first periodic structure 29 for DVD and 180 ° out of phase with the second periodic structure 30 for DVD. Is formed.

  It is adjacent to the first periodic structure 29 for DVD in the other direction (right direction in FIG. 4) orthogonal to the periodic direction of the first periodic structure 29 for DVD and is DVD to the second periodic structure 30 for DVD. A fourth periodic structure 32 for DVD is formed at a position facing the first periodic structure 29 for DVD.

  The fourth periodic structure 32 for DVD is formed by alternately arranging a plurality of convex portions 32a and concave portions 32b along the vertical direction in FIG. That is, the periodic direction of the fourth periodic structure 32 for DVD is also parallel to the periodic direction of the first periodic structure 29 for DVD.

  Further, the fourth periodic structure 32 for DVD is different in phase by 90 ° (+ 90 °) from the first periodic structure 29 for DVD and 180 ° different in phase from the second periodic structure 30 for DVD. Is formed.

  It is adjacent to the first periodic structure 29 for DVD in the other direction (right direction in FIG. 4) perpendicular to the periodic direction of the first periodic structure 29 for DVD, and the third periodic structure 31 for DVD. The first periodic structure 29 is opposed to the fourth periodic structure 32 for DVD and is adjacent to the fourth periodic structure 32 for DVD in the periodic direction (vertical direction (downward) in FIG. 4) of the DVD. A five-period structure 33 is formed.

  The fifth periodic structure 33 for DVD is formed by alternately arranging a plurality of convex portions 33a and concave portions 33b along the vertical direction in FIG. That is, the periodic direction of the fifth periodic structure 33 for DVD is also parallel to the periodic direction of the first periodic structure 29 for DVD.

  Further, the fifth periodic structure 33 for DVD has a phase difference of 90 ° (−90 °) with respect to the first periodic structure 29 for DVD, and a phase difference of 180 ° with respect to the third periodic structure 31 for DVD, Further, the fourth periodic structure 32 for DVD is formed so that the phase differs by 180 °.

  Such a DVD grating surface 26 diffracts DVD light to generate three DVD beams.

  According to the grating surface 26 for DVD in which such five periodic structures 29, 30, 31, 32, and 33 are formed, the objective lens arranged immediately before the DVD is used for recording or reproduction on the DVD. Even if it is displaced in the radial direction, it is possible to suppress the deterioration of the visual field characteristics.

  On the other hand, as shown in FIG. 5, the CD grating surface 27 has a first period for CD as a first periodic structure in which a plurality of convex portions 35a and concave portions 35b are alternately arranged along the vertical direction in FIG. It has a structure 35.

  The CD first periodic structure 35 is adjacent to the CD first periodic structure 35 in a position adjacent in one direction (right direction in FIG. 5) perpendicular to the periodic direction (vertical direction in FIG. 5) of the CD first periodic structure 35. A CD second periodic structure 36 is formed as a second periodic structure whose phase is 90 ° different from that of the one periodic structure 35.

  Similar to the first periodic structure 35 for CD, the second periodic structure 36 for CD is formed by alternately arranging a plurality of convex portions 36a and concave portions 36b along the vertical direction in FIG. . That is, the periodic direction of the second CD periodic structure 36 is parallel to the periodic direction of the first CD periodic structure 35.

  Further, the phase of the second CD periodic structure 36 is −90 ° when the phase of the first CD periodic structure 35 is 0 °.

  Adjacent to the first periodic structure for CD 35 in one direction (right direction in FIG. 5) perpendicular to the periodic direction of the first periodic structure for CD 35 and to the second periodic structure for CD 36 A third periodic structure 37 for CD is formed at a position adjacent to the first periodic structure 35 for use in the periodic direction (vertical direction (downward) in FIG. 5).

  The third periodic structure 37 for CD is formed by alternately arranging a plurality of convex portions 37a and concave portions 37b along the vertical direction in FIG. That is, the periodic direction of the third periodic structure for CD 37 is also parallel to the periodic direction of the first periodic structure for CD 35.

  Further, the third periodic structure 37 for CD is 90 ° (+ 90 °) different in phase from the first periodic structure 35 for CD and 180 ° different in phase from the second periodic structure 36 for CD. Is formed.

  It is adjacent to the first periodic structure for CD 35 in the other direction (left direction in FIG. 5) orthogonal to the periodic direction of the first periodic structure for CD 35, and is CD to the second periodic structure for CD 36. A fourth CD periodic structure 38 is formed at a position opposite to the first periodic structure 35 for CD.

  The fourth periodic structure for CD 38 is formed by alternately arranging a plurality of convex portions 38a and concave portions 38b along the vertical direction in FIG. That is, the periodic direction of the fourth periodic structure for CD 38 is also parallel to the periodic direction of the first periodic structure 35 for CD.

  Further, the fourth periodic structure for CD 38 is 90 ° (+ 90 °) out of phase with respect to the first periodic structure 35 for CD, and 180 ° out of phase with respect to the second periodic structure 36 for CD. Is formed.

  It is adjacent to the first periodic structure for CD 35 in the other direction (left direction in FIG. 5) perpendicular to the periodic direction of the first periodic structure for CD 35, and the third periodic structure for CD 37 The CD first periodic structure 35 is opposed to the CD fourth periodic structure 38 in the periodic direction (vertical direction (downward) in FIG. 5) of the CD. A five-period structure 39 is formed.

  The fifth periodic structure 39 for CD is formed by alternately arranging a plurality of convex portions 39a and concave portions 39b along the vertical direction in FIG. That is, the periodic direction of the fifth periodic structure 39 for CD is also parallel to the periodic direction of the first periodic structure 35 for CD.

  Further, the fifth periodic structure 39 for CD has a phase that is 90 ° (−90 °) different from the first periodic structure 35 for CD, and a phase that is 180 ° different from the third periodic structure 37 for CD, Furthermore, it is formed so that the phase is 180 ° different from that of the fourth periodic structure 38 for CD.

  Such a grating surface 27 for CD generates three beams for CD by diffracting CD light.

  According to the CD grating surface 27 on which such five periodic structures 35, 36, 37, 38, 39 are formed, the objective lens arranged immediately before the CD is the CD when the CD is recorded or reproduced. Even if it is displaced in the radial direction, it is possible to suppress the deterioration of the visual field characteristics.

As in the first embodiment, the optical element 25 in the present embodiment includes the DVD-side virtual center line CL _DVD passing through the center position in the direction orthogonal to the periodic direction in the first periodic structure 29 for _DVD, and the first period for CD. The CD-side virtual center line CL _CD passing through the center position in the direction perpendicular to the periodic direction in the structure 35 is perpendicular to the periodic direction of the first periodic structures 29 and 35 for DVD and CD (lateral direction in FIGS. 4 and 5). ).

Thereby, also in this embodiment, it becomes possible to irradiate the center of the DVD light to one point on the DVD side virtual center line CL _DVD , and the center of the CD light is set to one point on the CD side virtual center line CL _CD. Irradiation is possible.

  As a result, the second periodic structure 30 for DVD, the third periodic structure 31 for DVD, the fourth periodic structure 32 for DVD, and the fifth periodic structure 33 for DVD can be irradiated with the same amount of DVD light. Similar to the first embodiment, three DVD beams suitable for signal processing for tracking servo can be generated on the grating surface 26 for DVD.

  Further, since the second periodic structure for CD 36, the third periodic structure for CD 37, the fourth periodic structure for CD 38, and the fifth periodic structure for CD 39 can be irradiated with the same amount of CD light, CD On the grating surface 27, three CD beams suitable for signal processing for tracking servo can be generated.

(Third embodiment of optical element)
As shown in FIGS. 6 and 7, the optical element 48 in the present embodiment has a predetermined thickness in a direction perpendicular to the paper surface in FIGS. 6 and 7.

  As in the first and second embodiments, the optical element 48 in the present embodiment has a grating surface 49 for DVD as a first grating surface formed on the front surface in the thickness direction, and the paper surface in the thickness direction. It is a double-sided diffraction grating in which a CD grating surface 50 as a second grating surface is formed on the back surface.

  However, in the present embodiment, the specific configuration of each of the lattice planes 49 and 50 is different from that of the first and second embodiments.

  That is, as shown in FIG. 6, the DVD lattice plane 49 has a first period for DVD as a first periodic structure in which a plurality of convex portions 51a and concave portions 51b are alternately arranged along the vertical direction in FIG. It has a structure 51.

  In the position adjacent to the first periodic structure 51 for DVD in one direction (left direction in FIG. 6) perpendicular to the periodic direction (vertical direction in FIG. 6) of the first periodic structure 51 for DVD, A second periodic structure 52 for DVD is formed as a second periodic structure whose phase is 90 ° different from that of the one periodic structure 51.

  Similar to the first periodic structure 51 for DVD, the second periodic structure 52 for DVD is formed by alternately arranging a plurality of convex portions 52a and concave portions 52b along the vertical direction in FIG. . That is, the periodic direction of the second periodic structure 52 for DVD is parallel to the periodic direction of the first periodic structure 51 for DVD.

  Further, the phase of the second periodic structure 52 for DVD is −90 ° when the phase of the first periodic structure 51 for DVD is 0 °.

  It is adjacent to the first periodic structure 51 for DVD in one direction (left direction in FIG. 6) orthogonal to the periodic direction of the first periodic structure 51 for DVD and is DVD to the second periodic structure 52 for DVD. A third periodic structure 53 for DVD is formed at a position adjacent to the first periodic structure 51 for use in the periodic direction (vertical direction (downward) in FIG. 6).

  The third periodic structure 53 for DVD is formed by alternately arranging a plurality of convex portions 53a and concave portions 53b along the vertical direction in FIG. That is, the periodic direction of the third periodic structure 53 for DVD is also parallel to the periodic direction of the first periodic structure 51 for DVD.

  Further, the third periodic structure 53 for DVD is 90 ° (+ 90 °) out of phase with the first periodic structure 51 for DVD and 180 ° out of phase with the second periodic structure 52 for DVD. Is formed.

  It is adjacent to the first periodic structure 51 for DVD in one direction (left direction in FIG. 6) orthogonal to the periodic direction of the first periodic structure 51 for DVD and is DVD to the third periodic structure 53 for DVD. A fourth DVD periodic structure 54 is formed at a position adjacent to the first periodic structure 51 for use in the periodic direction (vertical direction (downward) in FIG. 6).

  The fourth periodic structure 54 for DVD is formed by alternately arranging a plurality of convex portions 54a and concave portions 54b along the vertical direction in FIG. That is, the periodic direction of the fourth periodic structure 54 for DVD is also parallel to the periodic direction of the first periodic structure 51 for DVD.

  Further, the fourth periodic structure for DVD 54 is 90 ° (−90 °) out of phase with the first periodic structure 51 for DVD and 180 ° out of phase with the third periodic structure 53 for DVD. Is formed.

  It is adjacent to the first periodic structure 51 for DVD in the other direction (right direction in FIG. 6) orthogonal to the periodic direction of the first periodic structure 51 for DVD and is DVD to the second periodic structure 52 for DVD. A fifth periodic structure 55 for DVD is formed at a position opposite to the first periodic structure 51 for DVD.

  The fifth periodic structure 55 for DVD is formed by arranging a plurality of convex portions 55a and concave portions 55b alternately along the vertical direction in FIG. That is, the periodic direction of the fifth periodic structure 55 for DVD is also parallel to the periodic direction of the first periodic structure 51 for DVD.

  Further, the fifth periodic structure 55 for DVD is 90 ° (+ 90 °) out of phase with the first periodic structure 51 for DVD and 180 ° out of phase with the second periodic structure 52 for DVD. Is formed.

  It is adjacent to the first periodic structure 51 for DVD in the other direction (right direction in FIG. 6) orthogonal to the periodic direction of the first periodic structure 51 for DVD, and the third periodic structure 53 for DVD. The first periodic structure 51 is opposed to the fifth periodic structure 55 for DVD and is adjacent to the fifth periodic structure 55 for DVD in the periodic direction (vertical direction (downward) in FIG. 6) of the DVD. A six-period structure 56 is formed.

  The sixth periodic structure for DVD 56 is formed by alternately arranging a plurality of convex portions 56a and concave portions 56b along the vertical direction in FIG. That is, the periodic direction of the sixth periodic structure for DVD 56 is also parallel to the periodic direction of the first periodic structure 51 for DVD.

  Further, the sixth periodic structure for DVD 56 has a phase difference of 90 ° (−90 °) with respect to the first periodic structure for DVD 51, and a phase difference of 180 ° with respect to the third periodic structure for DVD 53, Furthermore, it is formed so that the phase is 180 ° different from that of the fifth periodic structure 55 for DVD.

  Adjacent to the first periodic structure 51 for DVD in the other direction (right direction in FIG. 6) orthogonal to the periodic direction of the first periodic structure 51 for DVD, and to the fourth periodic structure 54 for DVD. The first periodic structure 51 is opposed to the sixth periodic structure for DVD 56 and is adjacent to the sixth periodic structure for DVD 56 in the periodic direction (vertical direction (downward) in FIG. 6) of the DVD. A seven-period structure 57 is formed.

  The seventh periodic structure 57 for DVD is formed by alternately arranging a plurality of convex portions 57a and concave portions 57b along the vertical direction in FIG. That is, the periodic direction of the seventh periodic structure 57 for DVD is also parallel to the periodic direction of the first periodic structure 51 for DVD.

  Further, the seventh periodic structure 56 for DVD has a phase difference of 90 ° (+ 90 °) with respect to the first periodic structure 51 for DVD, and a phase difference of 180 ° with respect to the fourth periodic structure 54 for DVD. The sixth periodic structure 56 for DVD is formed so that the phase is 180 ° different.

  Such a DVD grating surface 49 generates three beams for DVD by diffracting DVD light.

  According to the DVD lattice plane 49 on which such seven periodic structures 51, 52, 53, 54, 55, 56, and 57 are formed, an objective placed immediately before the DVD during recording or reproduction on the DVD. Even if the lens is displaced in the radial direction of the DVD, it is possible to suppress the deterioration of the visual field characteristics.

  On the other hand, as shown in FIG. 7, the CD grating surface 50 has a first period for CD as a first periodic structure in which a plurality of convex portions 58a and concave portions 58b are alternately arranged along the vertical direction in FIG. It has a structure 58.

  The CD first periodic structure 58 is adjacent to the CD first periodic structure 58 in a position adjacent in one direction (right direction in FIG. 7) perpendicular to the periodic direction (vertical direction in FIG. 7) of the CD first periodic structure 58. A CD second periodic structure 59 is formed as a second periodic structure whose phase is 90 ° different from that of the one periodic structure 58.

  Similar to the first periodic structure 58 for CD, the second periodic structure 59 for CD is formed by alternately arranging a plurality of convex portions 59a and concave portions 59b along the vertical direction in FIG. . That is, the periodic direction of the second CD periodic structure 59 is parallel to the periodic direction of the first CD periodic structure 58.

  Further, the phase of the second periodic structure 59 for CD is −90 ° when the phase of the first periodic structure 58 for CD is 0 °.

  It is adjacent to the first periodic structure 58 for CD in one direction (right direction in FIG. 7) orthogonal to the periodic direction of the first periodic structure 58 for CD, and is CD to the second periodic structure 59 for CD. The third periodic structure 60 for CD is formed at a position adjacent to the first periodic structure 58 for use in the periodic direction (vertical direction (downward) in FIG. 7).

  The third periodic structure 60 for CD is formed by alternately arranging a plurality of convex portions 60a and concave portions 60b along the vertical direction in FIG. That is, the periodic direction of the third periodic structure for CD 60 is also parallel to the periodic direction of the first periodic structure 58 for CD.

  Further, the third periodic structure 60 for CD is 90 ° (+ 90 °) different in phase from the first periodic structure 58 for CD and 180 ° different in phase from the second periodic structure 59 for CD. Is formed.

  It is adjacent to the first periodic structure 58 for CD in one direction (right direction in FIG. 7) orthogonal to the periodic direction of the first periodic structure 58 for CD, and to the third periodic structure 60 for CD. The fourth periodic structure 61 for CD is formed at a position adjacent to the first periodic structure 58 for use in the periodic direction (vertical direction (downward) in FIG. 7).

  The fourth periodic structure 61 for CD is formed by alternately arranging a plurality of convex portions 61a and concave portions 61b along the vertical direction in FIG. That is, the periodic direction of the fourth periodic structure for CD 61 is also parallel to the periodic direction of the first periodic structure for CD 58.

  Further, the fourth periodic structure 61 for CD is 90 ° (−90 °) different in phase from the first periodic structure 58 for CD and 180 ° different in phase from the third periodic structure 60 for CD. Is formed.

  It is adjacent to the first periodic structure 58 for CD in the other direction (left direction in FIG. 7) orthogonal to the periodic direction of the first periodic structure 58 for CD, and to the second periodic structure 59 for CD. A CD fifth periodic structure 62 is formed at a position opposite to the first periodic structure 58 for CD.

  The fifth periodic structure 62 for CD is formed by arranging a plurality of convex portions 62a and concave portions 62b alternately along the vertical direction in FIG. That is, the periodic direction of the fifth periodic structure for CD 62 is also parallel to the periodic direction of the first periodic structure for CD 58.

  Further, the fifth periodic structure 62 for CD is 90 ° (+ 90 °) different in phase from the first periodic structure 58 for CD and 180 ° different in phase from the second periodic structure 59 for CD. Is formed.

  It is adjacent to the first periodic structure 58 for CD in the other direction (left direction in FIG. 7) orthogonal to the periodic direction of the first periodic structure 58 for CD, and the third periodic structure 60 for CD. Opposite the first periodic structure 58 in the periodic direction of the first periodic structure 58 for CD (vertical direction (downward) in FIG. 7) with respect to the fifth periodic structure 62 for CD, A six-period structure 63 is formed.

  The sixth periodic structure 63 for CD is formed by alternately arranging a plurality of convex portions 63a and concave portions 63b along the vertical direction in FIG. That is, the periodic direction of the sixth periodic structure for CD 63 is also parallel to the periodic direction of the first periodic structure for CD 58.

  Further, the sixth periodic structure for CD 63 has a phase difference of 90 ° (−90 °) with respect to the first periodic structure for CD 58, and a phase difference of 180 ° with respect to the third periodic structure for CD 60, Further, it is formed so that the phase is 180 ° different from that of the fifth periodic structure 62 for CD.

  It is adjacent to the first periodic structure 58 for CD in the other direction (left direction in FIG. 7) orthogonal to the periodic direction of the first periodic structure 58 for CD, and is connected to the fourth periodic structure 61 for CD. The CD first periodic structure 58 is opposed to the sixth periodic structure 63 for CD in the periodic direction (vertical direction (downward) in FIG. 7) of the first periodic structure 58 for CD. A seven-period structure 64 is formed.

  The CD seventh periodic structure 64 is formed by alternately arranging a plurality of convex portions 64a and concave portions 64b along the vertical direction in FIG. That is, the periodic direction of the seventh periodic structure for CD 64 is also parallel to the periodic direction of the first periodic structure for CD 58.

  Further, the seventh periodic structure for CD 64 has a phase difference of 90 ° (+ 90 °) with respect to the first periodic structure for CD 58 and a phase difference of 180 ° with respect to the fourth periodic structure for CD 61, and The sixth periodic structure 63 for CD is formed so that the phase is 180 ° different.

  Such a CD grating surface 50 diffracts CD light to generate three CD beams.

  According to the CD grating surface 50 on which such seven periodic structures 58, 59, 60, 61, 62, 63, and 64 are formed, an objective placed immediately before the CD when recording or reproducing the CD is performed. Even if the lens is displaced in the radial direction of the CD, it is possible to suppress the deterioration of the visual field characteristics.

As in the first embodiment, the optical element 48 in the present embodiment includes a DVD-side virtual center line CL _DVD passing through the center position in the direction orthogonal to the periodic direction in the first periodic structure 51 for _DVD, and the first period for CD. The CD-side virtual center line CL _CD passing through the center position in the direction orthogonal to the periodic direction in the structure 58 is orthogonal to the periodic direction of the first periodic structures 51 and 58 for DVD and CD (lateral direction in FIGS. 6 and 7). ).

Thereby, also in this embodiment, it becomes possible to irradiate the center of the DVD light to one point on the DVD side virtual center line CL _DVD , and the center of the CD light is set to one point on the CD side virtual center line CL _CD. Irradiation is possible.

  As a result, the third periodic structure 53 for DVD and the sixth periodic structure 56 for DVD can be irradiated with the same amount of DVD light, and the second periodic structure 52 for DVD, the fourth periodic structure 54 for DVD, Since the fifth periodic structure 55 for DVD and the seventh periodic structure 57 for DVD can be irradiated with the same amount of DVD light, as in the first embodiment, the tracking surface 49 for DVD is used for tracking servo. It is possible to generate three beams for DVD suitable for signal processing.

  The third periodic structure for CD 60 and the sixth periodic structure for CD 63 can be irradiated with the same amount of CD light, and the second periodic structure for CD 59, the fourth periodic structure for CD 61, the CD Since the fifth periodic structure 62 for CD and the seventh periodic structure for CD 64 can be irradiated with the same amount of CD light, the CD grating surface 50 is suitable for signal processing for tracking servo. Three beams can be generated.

(Embodiment of optical pickup device)
Next, an embodiment of an optical pickup device according to the present invention will be described with reference to FIG.

  As shown in FIG. 8, the optical pickup device 67 in this embodiment has a two-wavelength light source 22 that selectively emits DVD light and CD light as a light source.

  At the position on the light emission side with respect to the two-wavelength light source 22, any one of the optical elements 10, 25, 48 in the first to third embodiments described above has the DVD grating surface 11, 26 and 49 are arranged so as to face the two-wavelength light source 22 side.

  When DVD light is emitted from the two-wavelength light source 22, the optical elements 10, 25, and 48 diffract the DVD light by the DVD grating surfaces 11, 26, and 49 to generate three DVD beams (hereinafter referred to as “DVD”). (Referred to as DVD forward path 3 beam). At this time, the CD grating surfaces 12, 27, and 50 transmit the DVD outward three beams as they are without being diffracted.

  Further, when the CD light is emitted from the two-wavelength light source 22, the optical elements 10, 25, and 48 diffract the CD light by the CD grating surfaces 12, 27, and 50 to obtain three CD beams ( Hereinafter, this is referred to as a CD forward path 3 beam). At this time, the DVD grating surfaces 11, 26, and 49 transmit the CD light as it is without being diffracted.

  A polarizing beam splitter 69 is disposed at a position on the light emission side with respect to the optical elements 10, 25, and 48, and the DVD outgoing path emitted from the optical elements 10, 25, and 48 is disposed in the polarizing beam splitter 69. Three beams or three CD forward beams are incident.

  The DVD forward path 3 beam or CD forward path 3 beam incident on the polarization beam splitter 69 is reflected by the polarization beam splitter 69.

  A collimator lens 70 is disposed at a position on the reflection side of the DVD forward path 3 beam or the CD forward path 3 beam with respect to the polarization beam splitter 69. Three beams or three CD forward beams are incident.

  The DVD forward three beams or CD forward three beams incident on the collimator lens 70 are converted into parallel light by the collimator lens 70 and emitted.

  A rising mirror 71 is disposed at a position on the exit side of the DVD outward path 3 beam or the CD outward path 3 beam with respect to the collimator lens 70, and the DVD outbound path emitted from the collimator lens 70 is disposed on the rising mirror 71. Three beams or three CD forward beams are incident.

  The DVD forward path 3 beam or CD forward path 3 beam incident on the rising mirror 71 is totally reflected by the rising mirror 71.

  A quarter-wave plate 72 is disposed at a position on the reflection side of the DVD outward path 3 beam or the CD outward path 3 beam with respect to the rising mirror 71. The DVD outward path 3 beam or CD outbound path 3 beam reflected by is incident.

  The DVD outward three beams or CD outward three beams incident on the quarter wavelength plate 72 are converted from linearly polarized light to circularly polarized light by the quarter wavelength plate 72 and emitted.

  An objective lens 73 is disposed at a position on the exit side of the DVD outward path 3 beam or CD outward path 3 beam with respect to the quarter wavelength plate 72, and the objective lens 73 emits light from the quarter wavelength plate 72. The DVD forward path 3 beam or CD forward path 3 beam is incident.

  The DVD outward three beams or CD outward three beams incident on the objective lens 73 are converted into convergent light by the objective lens 73 and emitted.

  A DVD 75 or CD 76 is selectively disposed at a position on the exit side of the DVD outward path 3 beam or the CD outward path 3 beam with respect to the objective lens 73.

  A DVD 75 is irradiated with three DVD forward beams emitted from the objective lens 73 and is irradiated as a light spot. Further, the CD 76 is irradiated with three CD forward beams emitted from the objective lens 73 and irradiated as a light spot.

  The DVD outward three beams incident on the DVD 75 are reflected by the recording surface of the DVD 15 and then travel in the reverse direction as the DVD backward three beams. Further, the CD outward three beams incident on the CD 76 are reflected by the recording surface of the CD 76 and then travel in the opposite direction as the CD backward three beams.

  In other words, the DVD return path 3 beam or the CD return path 3 beam exits the DVD 75 or CD 76, enters the objective lens 73, is converted into parallel light by the objective lens 73, and is emitted to the quarter wavelength plate 72 side. .

  The DVD return path 3 beam or the CD return path 3 beam emitted from the objective lens 73 is incident on the ¼ wavelength plate 72, and by this ¼ wavelength plate 72, the linearly polarized light whose direction of polarization is orthogonal to the forward path from the circular polarization And is output to the rising mirror 71 side.

  The DVD return path 3 beam or CD return path 3 beam emitted from the quarter-wave plate 72 is incident on the rising mirror 71 and is totally reflected by the rising mirror 71 toward the collimator lens 70.

  The DVD return path 3 beam or the CD return path 3 beam reflected by the rising mirror 71 enters the collimator lens 70, is converted into convergent light by the collimator lens 70, and is emitted to the polarization beam splitter 69 side.

  The DVD return path 3 beam or the CD return path 3 beam emitted from the collimator lens 70 enters the polarization beam splitter 69.

  The DVD return path 3 beam or CD return path 3 beam incident on the polarization beam splitter 69 passes through the polarization beam splitter 69 as it is.

  In order to properly enter both the DVD return 3 beam and the CD return 3 beam on the light receiving surface of the photodetector 78 at a position on the transmission side of the DVD return 3 beam or the CD return 3 beam with respect to the polarization beam splitter 69. An optical axis correction element 77 is arranged. The DVD return path 3 beam or the CD return path 3 beam transmitted through the polarization beam splitter 69 is incident on the optical axis correction element 77.

  The three DVD return path beams incident on the optical axis correction element 77 are emitted straight through the optical axis correction element 77 as they are. On the other hand, the CD return three beams incident on the optical axis correction element 77 are emitted after being deflected by the optical axis correction element 77.

  A sensor lens 79 is disposed between the optical axis correction element 77 and the photodetector 78. The sensor lens 79 has a DVD return path 3 beam or a CD return path 3 beam emitted from the optical axis correction element 77. Is incident.

  The DVD return path 3 beam or CD return path 3 beam incident on the sensor lens 79 is given astigmatism by the sensor lens 79 and is condensed and emitted to the photodetector 78 side.

  The DVD return path 3 beam or the CD return path 3 beam emitted from the sensor lens 79 enters the photodetector 78, and detects one light receiving surface for detecting the main beam and two sub beams in the photodetector 78. Two detection light spots are detected as two detection light spots.

  According to the optical pickup device 67 having such a configuration, at least one of information recording and reproduction can be performed on both the DVD 75 and the CD 76.

Further, when recording and / or reproducing information on the DVD 75, the center of the DVD light can be irradiated to one point on the DVD side virtual center line CL _DVD . Further, it is possible to generate a DVD forward three beam suitable for signal processing for tracking servo. As a result, it is possible to appropriately detect the detection light spot of the DVD backward three beams on the light receiving surface of the photodetector 78, and to record and / or reproduce information on the DVD 75 with high accuracy under accurate tracking servo. It can be carried out.

Further, when recording and / or reproducing information with respect to the CD 76, the center of the CD light can be irradiated to one point on the CD-side virtual center line CL _CD . Further, it is possible to generate three CD forward beams suitable for signal processing for tracking servo. As a result, it is possible to appropriately detect the detection light spot of the three beams in the CD backward path on the light receiving surface of the photodetector 78, and to record and / or reproduce information with respect to the CD 76 with high accuracy under accurate tracking servo. It can be carried out.

  In a more preferred embodiment, the DVD outward path 3 beam is irradiated onto the same track on the recording surface of the DVD 75, and the CD outward path 3 beam is irradiated onto the same track on the recording surface of the CD 76. To do.

  This is because the periodic directions of the DVD lattice planes 11, 26, 49 and the periodic structures of the CD lattice planes 12, 27, 50 are configured to face the radial direction of the DVD 75, CD76. Can be realized.

  By doing so, the waveform of the sum signal of the sub push-pull signals corresponding to each of the DVD light and the CD light can be made to be more ideal waveforms. Thus, at least one of recording and reproduction of information can be performed more appropriately.

  In addition, this invention is not limited to embodiment mentioned above, A various change is possible as needed.

  For example, in the above-described embodiment, DVD light and CD light are used as the first light and the second light selectively emitted from the two-wavelength light source 22, but it is not necessary to be limited to this. DVD light and Blu-ray light (λ = 405 nm) may be used, or DVD light and HD-DVD light (λ = 405 nm) may be used. Alternatively, CD light and HD-DVD light may be used, or CD light and Blu-ray light may be used.

  In addition, the first light source and the second light source are separately provided, and the first or second light emitted from each light source is used together with the optical element 10 by using a mirror or a prism as necessary. 25 and 48 may be used.

  Further, the number of periodic structures of the DVD grating surfaces 11, 26, 49 and the CD grating surfaces 12, 27, 50 need not be limited to the seventh shown in the third embodiment of the optical element.

  For example, four or more periodic structures are formed adjacent to each other along the periodic direction of the first periodic structure at positions adjacent in one direction orthogonal to the periodic direction of the first periodic structure, Four or more periodic structures may be formed adjacent to each other along the periodic direction of the first periodic structure at positions adjacent to each other in the other direction orthogonal to the periodic direction of the periodic structure.

Also in this case, the DVD-side virtual center line CL _DVD and the CD-side virtual center line CL _CD are configured to be shifted in the direction of shift between the center of the DVD light and the center of the CD light, and the first period If all the periodic structures other than the structure are configured so that the phase is different from that of the first periodic structure, and further, the phases of adjacent periodic structures in the periodic direction of the first periodic structure are configured to be different from each other, The same effects as those of the above-described embodiment can be obtained.

The top view which shows the grating | lattice surface for DVD in 1st Embodiment of the optical element which concerns on this invention. FIG. 3 is a perspective plan view showing a CD grating surface in the first embodiment of the optical element according to the present invention. The side view which shows 1st Embodiment of the optical element which concerns on this invention with a 2 wavelength light source The top view which shows the grating | lattice surface for DVD in 2nd Embodiment of the optical element which concerns on this invention. In the second embodiment of the optical element according to the present invention, a plan perspective view showing a lattice plane for CD The top view which shows the grating | lattice surface for DVD in 3rd Embodiment of the optical element which concerns on this invention. In the third embodiment of the optical element according to the present invention, a plan perspective view showing a lattice plane for CD The block diagram which shows embodiment of the optical pick-up apparatus which concerns on this invention The top view which shows the grating | lattice surface for DVD in an example of the conventional optical element Plane perspective view showing a lattice plane for CD in an example of a conventional optical element The figure which shows the problem of the conventional optical element

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical element 11 Lattice surface for DVD 12 Lattice surface for CD 14 1st periodic structure for DVD 15 2nd periodic structure for DVD 16 3rd periodic structure for DVD 18 1st periodic structure for CD 19 2nd periodic structure for CD 20 CD Third Periodic Structure 22 Two-wavelength Light Source 67 Optical Pickup Device

Claims (12)

A first grating surface that diffracts coherent first light to generate at least three beams is formed on one surface in the thickness direction, and the first light and wavelength are formed on the other surface in the thickness direction. An optical element formed with a second grating surface that diffracts different coherent second light to generate at least three beams,
Each of the first lattice plane and the second lattice plane is
A first periodic structure;
A second periodic structure formed so as to have a phase different from that of the first periodic structure at a position adjacent to the first periodic structure in one direction orthogonal to the periodic direction of the first periodic structure. When,
A third period formed at a position adjacent to the first periodic structure in the other direction orthogonal to the periodic direction of the first periodic structure so that the phase is different from at least the first periodic structure. A first virtual center line passing through a center position in a direction perpendicular to the periodic direction in the first periodic structure provided on the first grating surface, and the second grating surface. Further, the second virtual center line passing through the center position in the direction orthogonal to the periodic direction in the first periodic structure is a direction in which the center of the first light and the center of the second light are shifted from each other. An optical element that is shifted in a direction perpendicular to the periodic direction of the two first periodic structures. A first grating surface that diffracts coherent first light to generate at least three beams is formed on one surface in the thickness direction, and the first light and wavelength are formed on the other surface in the thickness direction. An optical element formed with a second grating surface that diffracts different coherent second light to generate at least three beams,
Each of the first lattice plane and the second lattice plane is
A first periodic structure;
A second periodic structure formed so as to have a phase different from that of the first periodic structure at a position adjacent to the first periodic structure in one direction orthogonal to the periodic direction of the first periodic structure. When,
Adjacent to the first periodic structure in one direction orthogonal to the periodic direction of the first periodic structure, and adjacent to the second periodic structure in the periodic direction of the first periodic structure A third periodic structure formed at a position to be different in phase from the first periodic structure and the second periodic structure;
Adjacent to the first periodic structure in the other direction orthogonal to the periodic direction of the first periodic structure, and opposed to the second periodic structure with the first periodic structure interposed therebetween A fourth periodic structure formed at a position different in phase from at least the first periodic structure;
Adjacent to the first periodic structure in the other direction orthogonal to the periodic direction of the first periodic structure, and opposed to the third periodic structure with the first periodic structure interposed therebetween. Furthermore, at a position adjacent to the fourth periodic structure in the periodic direction of the first periodic structure, the phase is different from at least the first periodic structure and the fourth periodic structure. A fifth periodic structure, and
A first virtual center line passing through a center position in a direction perpendicular to a periodic direction in the first periodic structure provided on the first lattice plane; and the first virtual center line provided on the second lattice plane. The second virtual center line passing through the center position in the direction orthogonal to the periodic direction in the periodic structure is the direction of deviation between the center of the first light and the center of the second light, and the two An optical element that is shifted in a direction orthogonal to the periodic direction of the first periodic structure. A first grating surface that diffracts coherent first light to generate at least three beams is formed on one surface in the thickness direction, and the first light and wavelength are formed on the other surface in the thickness direction. An optical element formed with a second grating surface that diffracts different coherent second light to generate at least three beams,
Each of the first lattice plane and the second lattice plane is
A first periodic structure;
The first periodic structure is adjacent to the first periodic structure in a direction perpendicular to the periodic direction of the first periodic structure, and adjacent to each other in the periodic direction of the first periodic structure. A plurality of periodic structures of 2nd to nth (n: natural number of 3 or more, the same shall apply hereinafter) sequentially formed along the periodic direction of the periodic structure, the phase being different from that of the first periodic structure, And the 2nd-nth periodic structure formed so that the phases of mutually adjacent periodic structures may differ from each other in the periodic direction of the first periodic structure;
The first periodic structure is adjacent to the first periodic structure in the other direction perpendicular to the periodic direction of the first periodic structure, and is adjacent to the first periodic structure in the periodic direction. A plurality of (n + 1) to (2n-1) periodic structures sequentially formed along the periodic direction of the periodic structure, the phase being different from at least the first periodic structure, and the first periodic structure The periodic structures adjacent to each other in the periodic direction are formed so that the phases thereof are different from each other, and the n + k (k: a natural number of 1 to n−1, hereinafter the same) periodic structure is the second to nth. At least the (k + 1) th periodic structure of the periodic structure and the (n + 1) th to (2n-1) th periodic structures formed so as to face each other across the first periodic structure,
A first virtual center line passing through a center position in a direction perpendicular to a periodic direction in the first periodic structure provided on the first lattice plane; and the first virtual center line provided on the second lattice plane. The second virtual center line passing through the center position in the direction orthogonal to the periodic direction in the periodic structure is the direction of deviation between the center of the first light and the center of the second light, and the two An optical element that is shifted in a direction orthogonal to the periodic direction of the first periodic structure. A first light source that emits coherent first light;
A second light source that emits coherent second light having a wavelength different from that of the first light;
A first grating surface that diffracts the first light to generate at least three beams is formed on one surface in the thickness direction, and the second light is diffracted on the other surface in the thickness direction. A diffractive structure formed with a second grating surface for generating at least three beams;
An objective lens for condensing the three beams generated by the diffraction structure and irradiating the light spot of the three beams on the recording surface of the optical information recording medium;
An optical pickup device comprising at least a photodetector that receives and detects reflected light from the optical information recording medium of the three-beam light spot,
Each of the first grating surface and the second grating surface in the diffractive structure is
A first periodic structure;
A second periodic structure formed so as to have a phase different from that of the first periodic structure at a position adjacent to the first periodic structure in one direction orthogonal to the periodic direction of the first periodic structure. When,
A third period formed at a position adjacent to the first periodic structure in the other direction orthogonal to the periodic direction of the first periodic structure so that the phase is different from at least the first periodic structure. With structure and
A first virtual center line passing through a center position in a direction perpendicular to a periodic direction in the first periodic structure provided on the first lattice plane; and the first virtual center line provided on the second lattice plane. The second virtual center line passing through the center position in the direction orthogonal to the periodic direction in the periodic structure is the direction of deviation between the center of the first light and the center of the second light, and the two The optical pick-up apparatus which has shifted | deviated to the direction orthogonal to the periodic direction of a 1st periodic structure.   5. The optical pickup device according to claim 4, wherein the first light source and the second light source are two-wavelength light sources formed integrally with each other. Three light spots generated by the first grating surface are irradiated on the same track on the recording surface of the first optical information recording medium corresponding to the three beams,
The light beam of three beams generated by the second grating surface is irradiated on the same track on the recording surface of the second optical information recording medium corresponding to the three beams. Or the optical pick-up apparatus of 5. A first light source that emits coherent first light;
A second light source that emits coherent second light having a wavelength different from that of the first light;
A first grating surface that diffracts the first light to generate at least three beams is formed on one surface in the thickness direction, and the second light is diffracted on the other surface in the thickness direction. A diffractive structure formed with a second grating surface for generating at least three beams;
An objective lens for condensing the three beams generated by the diffraction structure and irradiating the light spot of the three beams on the recording surface of the optical information recording medium;
An optical pickup device comprising at least a photodetector that receives and detects reflected light from the optical information recording medium of the three-beam light spot,
Each of the first grating surface and the second grating surface in the diffractive structure is
A first periodic structure;
A second periodic structure formed so as to have a phase different from that of the first periodic structure at a position adjacent to the first periodic structure in one direction orthogonal to the periodic direction of the first periodic structure. When,
Adjacent to the first periodic structure in one direction orthogonal to the periodic direction of the first periodic structure, and adjacent to the second periodic structure in the periodic direction of the first periodic structure A third periodic structure formed at a position to be different in phase from the first periodic structure and the second periodic structure;
Adjacent to the first periodic structure in the other direction orthogonal to the periodic direction of the first periodic structure, and opposed to the second periodic structure with the first periodic structure interposed therebetween A fourth periodic structure formed at a position different in phase from at least the first periodic structure;
Adjacent to the first periodic structure in the other direction orthogonal to the periodic direction of the first periodic structure, and opposed to the third periodic structure with the first periodic structure interposed therebetween. Furthermore, at a position adjacent to the fourth periodic structure in the periodic direction of the first periodic structure, the phase is different from at least the first periodic structure and the fourth periodic structure. A fifth periodic structure, and
A first virtual center line passing through a center position in a direction perpendicular to a periodic direction in the first periodic structure provided on the first lattice plane; and the first virtual center line provided on the second lattice plane. The second virtual center line passing through the center position in the direction orthogonal to the periodic direction in the periodic structure is the direction of deviation between the center of the first light and the center of the second light, and the two The optical pick-up apparatus which has shifted | deviated to the direction orthogonal to the periodic direction of a 1st periodic structure.   8. The optical pickup device according to claim 7, wherein the first light source and the second light source are two-wavelength light sources formed integrally with each other. Three light spots generated by the first grating surface are irradiated on the same track on the recording surface of the first optical information recording medium corresponding to the three beams,
The light beam of three beams generated by the second grating surface is irradiated on the same track on the recording surface of the second optical information recording medium corresponding to the three beams. Or the optical pickup device according to any one of 8; A first light source that emits coherent first light;
A second light source that emits coherent second light having a wavelength different from that of the first light;
A first grating surface that diffracts the first light to generate at least three beams is formed on one surface in the thickness direction, and the second light is diffracted on the other surface in the thickness direction. A diffractive structure formed with a second grating surface for generating at least three beams;
An objective lens for condensing the three beams generated by the diffraction structure and irradiating the light spot of the three beams on the recording surface of the optical information recording medium;
An optical pickup device comprising at least a photodetector that receives and detects reflected light from the optical information recording medium of the three-beam light spot,
Each of the first grating surface and the second grating surface in the diffractive structure is
A first periodic structure;
The first periodic structure is adjacent to the first periodic structure in a direction perpendicular to the periodic direction of the first periodic structure, and adjacent to each other in the periodic direction of the first periodic structure. A plurality of periodic structures of 2nd to nth (n: natural number of 3 or more, the same shall apply hereinafter) sequentially formed along the periodic direction of the periodic structure, the phase being different from that of the first periodic structure, And the 2nd-nth periodic structure formed so that the phases of mutually adjacent periodic structures may differ from each other in the periodic direction of the first periodic structure;
The first periodic structure is adjacent to the first periodic structure in the other direction perpendicular to the periodic direction of the first periodic structure, and is adjacent to the first periodic structure in the periodic direction. A plurality of (n + 1) to (2n-1) periodic structures sequentially formed along the periodic direction of the periodic structure, the phase being different from at least the first periodic structure, and the first periodic structure The periodic structures adjacent to each other in the periodic direction are formed so that the phases thereof are different from each other, and the n + k (k: a natural number of 1 to n−1, hereinafter the same) periodic structure is the second to nth. At least the (k + 1) th periodic structure of the periodic structure and the (n + 1) th to (2n-1) th periodic structures formed so as to face each other across the first periodic structure,
A first virtual center line passing through a center position in a direction perpendicular to a periodic direction in the first periodic structure provided on the first lattice plane; and the first virtual center line provided on the second lattice plane. The second virtual center line passing through the center position in the direction orthogonal to the periodic direction in the periodic structure is the direction of deviation between the center of the first light and the center of the second light, and the two The optical pick-up apparatus which has shifted | deviated to the direction orthogonal to the periodic direction of a 1st periodic structure.   The optical pickup device according to claim 10, wherein the first light source and the second light source are two-wavelength light sources formed integrally with each other. Three light spots generated by the first grating surface are irradiated on the same track on the recording surface of the first optical information recording medium corresponding to the three beams,
The three-beam light spot generated by the second grating surface is irradiated on the same track on the recording surface of the second optical information recording medium corresponding to the three beams. Or the optical pickup device according to 11;