Abstract: An optical pickup device includes a diffraction grating 12 for separating a light beam emitted from a semiconductor laser element into at least three light beams. The diffraction grating 12 is divided into three regions by a straight line extending in a direction parallel to a tangent line of a track of an optical information recording medium. A second region 12B is divided into a first sub-block 13 and a second sub-block 14 by a straight line extending in a direction parallel to a radius direction of the optical information recording medium. The first sub-block 13 has a phase difference of approximately 180 degrees from the second sub-block 14. The first region 12A has a phase difference of approximately 90 degrees from the first sub-block 13 and has a phase difference of approximately 180 degrees from the third region 12C.

Abstract: An optical controller includes a light source for emitting light, an object lens for condensing light emitted from the light source, a light detection unit for receiving light reflected on an optical information recording medium and outputting a signal corresponding to the amount of the light, and a laser control unit for controlling the amount of the light emitted from the light source to the information recording surface on which information is to be recorded or reproduced, based on the recording state of an information recording surface disposed closer to the object lens than an information recording surface on which the information is to be recorded or reproduced.

Abstract: An optical pickup apparatus includes a semiconductor laser for emitting a laser light, an objective lens for irradiating the light flux emitted from the semiconductor laser onto an optical disc, and a light detector for receiving the light flux reflected from the optical disc. The light detector has a light receiving part that comprises five regions of a region 1, a region 2, a region 3, a region 4 and a region 5.

Abstract: An optical pickup device includes a diffraction grating 12 for separating an emitted light beam into at least three light beams. The diffraction grating 12 is divided into three regions by dividing lines D1 and D2 extending in a first direction parallel to a tangent line of a track of an optical information recording medium. A second region 12B is divided into four sub-blocks by a dividing line D3 extending in the first direction and a dividing line D4 extending in a second direction that crosses the first direction. The sub-blocks located diagonally opposite to each other have a same phase, and the sub-blocks located adjacent to each other have a phase difference of approximately 180 degrees. The first region 12A has a phase difference of approximately 90 degrees from each sub-block of the second region 12B, and the first region 12A has a phase difference of approximately 180 degrees from the third region 12C.

Abstract: An optical pickup includes: a first emitting unit to emit an optical beam of a first wavelength; a second emitting unit to emit an optical beam of a second wavelength; a third emitting unit to emit an optical beam of a third wavelength; an object lens to condense optical beams emitted from the first through third emitting units onto a signal recording face of an optical disc; and a diffraction unit provided on one face of an optical element or the object lens positioned on the optical path of the optical beams of the first through third wavelengths; wherein the diffraction unit includes a generally circular first diffraction region provided on the innermost perimeter, a ring zone shaped second diffraction region provided on the outer side of the first diffraction region, and a ring zone shaped third diffraction region provided on the outer side of the second diffraction region.

Abstract: An optical pickup apparatus includes an astigmatic element, an angle adjusting element for contradicting propagation directions of luminous fluxes within four different luminous flux regions out of a reflected light, a polarization adjusting element. Two of the luminous flux regions are placed in a direction in which aligned are a set of opposite angles made by the two mutually crossing straight lines respectively parallel to a first convergence direction and a second convergence direction vertical to the first convergence direction by the astigmatic element, and the remaining two luminous flux regions are placed in a direction in which an alternate set of opposite angles are aligned. The polarization adjusting element differentiates polarization directions of luminous fluxes which are selected out of the luminous fluxes within the four luminous flux regions and which are adjacent in a peripheral direction in which the optical axis of reflected light serves as an axis.

Abstract: A complex objective lens composed of a hologram and an objective lens, capable of realizing stable and high-precision compatible reproducing/recording of a BD with a base thickness of about 0.1 mm for a blue light beam (wavelength ?1) and a DVD with a base thickness of about 0.6 mm for a red light beam (wavelength ?2). In an inner circumferential portion of the hologram, a grating is formed, which has a cross-sectional shape including as one period a step of heights in the order of 0 time, twice, once, and three times a unit level difference that gives a difference in optical path of about one wavelength with respect to a blue light beam, from an outer peripheral side to an optical axis side. The hologram transmits a blue light beam as 0th-order diffracted light without diffracting it, and disperses a red light beam passing through an inner circumferential portion as +1st-order diffracted light and allows it to be condensed by an objective lens.

Abstract: An optical system for spatially controlling light polarization, and method for manufacturing the same, includes a light source for generating a light beam of a designated wavelength, a beam shaper for splitting the light beam generated from the light source into a plurality of partial beams, and a polarization controller controlling the polarization states of the partial beams. The polarization controller may be formed on the beam shaper or separate from the beam shaper.

Abstract: An optical pickup apparatus includes a semiconductor laser for emitting a laser light, an objective lens for irradiating the light flux emitted from the semiconductor laser onto an optical disc, and a light detector for receiving the light flux reflected from the optical disc. The light detector has a light receiving part that comprises a region 1, a region 2, a region 3, a region 4, a region 5, a region 6 and a region 7.

Abstract: An optical pickup including a light source, a light focus device, a diffraction element, an optical split element, a ¼ wavelength board, a light reception device and a correction element wherein the correction element is divided into multiple areas in a surface vertical to an optical axis, each area of the multiple areas has a sub-wavelength convexo-concave structure having a pitch equal to or shorter than a wavelength of the outgoing light beam and the sub-wavelength convexo-concave structures of the multiple areas adjacent to each other have groove directions perpendicular to each other, and the filling factors of adjacent areas of the multiple areas are determined to substantially equalize effective refractive indices with regard to the polarization direction of the outgoing beam emitted from the light source and impart a phase difference of ? with regard to a polarization direction perpendicular to the polarization direction of the outgoing beam.

Abstract: The present invention provides a first light source (21) that emits light of a first wavelength, that at least either records onto or reproduces information from an information recording medium (30), a light source (22) that emits light of a second wavelength that records onto or reproduces information from an information recording medium (33), a light source (23) that emits light of a third wavelength that records onto or reproduces information from an information recording medium (23), focusing means, an optical element (28) that passes light of the first wavelength and diffracts light of the second and third wavelengths, wherein the optical element (28) is an optical element in which grooves are formed in a substrate, wherein the expression: 380 nm?(n?1)×d?420 nm is satisfied, where n is a refractive index of the substrate at a wavelength of 400 nm, and d (nm) is a depth per step of the grooves, and wherein the grooves are formed in two steps of depth d and depth 2d.

Abstract: An optical pickup apparatus comprises first, second and third light sources to emit light fluxes of wavelength ?1, ?2 and ?3 for conducting recording and/or reproducing information for first, second and third optical information recording mediums having respective protective substrates of thickness t1, t2 and t3 and a diffractive optical element located on a common optical path for the first, second and third light sources. A converged-light spot is formed on the first optical information recording medium with m-th order diffracted-light ray of the wavelength ?1, on the second optical information recording medium with n-th order diffracted-light ray of the wavelength ?2, and on the third optical information recording medium with k-th order diffracted-light ray of the wavelength ?3 generated by the diffractive optical element respectively, wherein one of m, n and k is different from one of other two numbers.

Abstract: An aberration detection device of the present invention is such that an absolute value of detection sensitivity of an aberration error signal is increased, and variation in detection sensitivity of the aberration error signal is little even when displacement between the center of light beam dividing means and the center of a bundle of light beams occurs due to a shift of a condensing optical system at the time of tracking control. A hologram element (2) divides light beams reflected from an information storage medium into at least two positive first order diffracted light beams. The hologram element (2) has a line (D1) extending in a radial direction and passing through an optical axis (OZ) and a division line (D2) having segments at least both ends thereof and a bulge in a center thereof, wherein the segments are substantially parallel to the line (D1), and the bulge (44) bulges toward the periphery of the hologram element (2) so that a top (D5) of the bulge (44) is substantially parallel to the line (D1).

Abstract: There is provided an objective lens used for an optical information recording/reproducing device for recording information to and/or reproducing information from two types of optical discs, by selectively using one of two types of substantially collimated light beams including first and second light beams. When wavelengths of the first and second light beams are respectively represented by ?1 (nm) and ?2 (nm), ?1<?2 is satisfied. The objective lens includes a first optical element, and a second optical element made of material different from that of the first optical element. The first and second optical elements are cemented via a cementing surface. Further, the objective lens is configured to satisfy a condition: 0.006 < { ( nR ? ? 2 - nR ? ? 1 ) - ( nB ? ? 2 - nB ? ? 1 ) } × ? [ { ( k ? ? 2 r ? ? 2 3 ) + 8 × A ? ? 42 } × f ? ? 1 3 + 2.29 ] < 0.038 ? .

Abstract: An offset-free tracking signal enables stable tracking control even if an optical disc is a multi-layer disc having three or more layers. Light receiving portions of a main region light receiving portion group are arranged between a projection line of a third dividing line on a photodetector and a projection line of a fourth dividing line on the photodetector by stray lights from information layers adjacent to the one, on which a light beam is focused, out of a plurality of information layers. Further, light receiving portions of a subregion light receiving portion group is arranged between a projection line of a first dividing line on a photodetector and a projection line of a second dividing line on the photodetector by the stray lights from the information layers adjacent to the one, on which a light beam is focused, out of the plurality of information layers.

Abstract: An optical pickup device includes a diffraction grating 12 for separating a light beam emitted from a semiconductor laser element into at least three light beams. The diffraction grating 12 is divided into three regions by a straight line extending in a direction parallel to a tangent line of a track of an optical information recording medium. A second region 12B is divided into a first sub-block 13 and a second sub-block 14 by a straight line extending in a direction parallel to a radius direction of the optical information recording medium. The first sub-block 13 has a phase difference of approximately 180 degrees from the second sub-block 14. The first region 12A has a phase difference of approximately 90 degrees from the first sub-block 13 and has a phase difference of approximately 180 degrees from the third region 12C.

Abstract: An optical pickup device is equipped with a diffraction element (8) that includes liquid crystal, two transparent electrodes sandwiching the liquid crystal, and a liquid crystal control portion (21) with electrodes connected electrically to the transparent electrode for controlling a voltage to be applied between the two transparent electrodes. The diffraction element (8) is provided with two types of diffraction areas (19) and (20). Each of the diffraction areas (19) and (20) generate predetermined diffracted light only from one of different wavelengths of light beams. The transparent electrodes of the diffraction areas (19) and (20) that are patterned are connected electrically to different electrodes (22c) and (22a), respectively.

Abstract: An optical pickup device includes a diffraction grating 12 for separating an emitted light beam into at least three light beams. The diffraction grating 12 is divided into three regions by dividing lines D1 and D2 extending in a first direction parallel to a tangent line of a track of an optical information recording medium. A second region 12B is divided into four sub-blocks by a dividing line D3 extending in the first direction and a dividing line D4 extending in a second direction that crosses the first direction. The sub-blocks located diagonally opposite to each other have a same phase, and the sub-blocks located adjacent to each other have a phase difference of approximately 180 degrees. The first region 12A has a phase difference of approximately 90 degrees from each sub-block of the second region 12B, and the first region 12A has a phase difference of approximately 180 degrees from the third region 12C.

Abstract: An optical pickup device and an optical disc apparatus which is capable to reduce variation of a detected signal due to unnecessary beam and detect a signal with high quality are provided. Amplification of sup PP signals necessary to produce a tracking error signal by a DPP method can be realized by an amplification factor smaller than a spectral radio of main and sub beams by the following structure. The optical pickup device includes an optical element having an area in which part of beam is diffracted and light shielding zones or insensitive zones having predetermined width are formed on center division lines in the light receiving planes of sub beams of the optical detector. The shape of a diffraction area is optimized to the shift amount of objective lens. The width of the light shielding zones or insensitive zones is optimized from the shift amount of objective lens and the shape of the diffraction area.

Abstract: A data reproducing method reproducing data recorded in a super resolution information storage medium in a form of marks having magnitudes less than a resolving power of an incident light beam, and an apparatus thereof. The data reproducing method includes irradiating a first beam having a resolving power causing a super resolution phenomenon and a second beam having a resolving power not causing a super resolution phenomenon into different places on the information storage medium, detecting a first reproduction signal based on the first beam and a second reproduction signal based on the second beam, and compensating for and calculating a temporal delay between the first reproduction signal and the second reproduction signal. Therefore, a signal reflected from a peripheral area of a reproduction beam spot other than a super resolution area can be excluded, thereby improving reproduction signal characteristics.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical integrated unit includes a semiconductor laser (11), a polarized light beam splitter (14), a light receiving element (12), and a polarized light diffraction element (15) for diffracting an optical beam (20) and returning light. The polarized light diffraction element (15) is so provided as to receive the light beam (20) having passed through a polarized light beam splitter surface (14a), and as to diffract the returning light such that an optical path of the returning light is changed to lead to the light receiving element (12). This makes it possible to provide (i) an optical integrated unit in which the beam diameter of light incidenting on a diffraction element is large and in which an optical path length from the diffraction element to a light receiving element is long, and (ii) an optical pickup device including such an optical integrated unit.

Abstract: There is provided an optical pickup apparatus that can obtain a stable servo signal by reducing stray light generated by diffraction in a recording layer other than a recording layer on which light is condensed. A hologram element provided in an optical pickup apparatus for recording information onto a recording medium and/or reproducing information on the recording medium by use of light includes fourth and fifth divisions where at least first-order diffracted light among diffracted light beams obtained by reflection and diffraction on a recording layer other than a light-condensed recording layer on which light is condensed by an objective lens so as not to be directed toward first and second light-receiving elements for detecting focus position information and third to eighth light-receiving elements for detecting track position information.

Abstract: An optical pickup apparatus according to the present invention includes: a first light source for emitting a first light flux; a second light source for emitting a second light flux; a third light source for emitting a third light flux; and an objective optical element. The objective optical element has an optical surface including at least two areas provided with optical path difference providing structures. The objective optical element converges the first to third light fluxes each passing through the predetermined areas on the objective optical element onto respective information recording surfaces of the first to third optical disks. The first optical path difference providing structure is a ring-shaped structure which includes a plurality of ring-shaped zones including respective steps having at least two kinds of amounts selected from the predetermined expressions.

Abstract: An optical pickup apparatus according to the present invention includes: a first light source for emitting a first light flux; a second light source for emitting a second light flux; a third light source for emitting a third light flux; and an objective optical element. The objective optical element has an optical surface including at least two areas provided with optical path difference providing structures. The objective optical element converges the first to third light fluxes each passing through the predetermined areas on the objective optical element onto respective information recording surfaces of the first to third optical disks. In the optical pickup apparatus, the third light flux which has passed through an optical path difference providing structure forms a first best focus and a second best focus.

Abstract: According to one embodiment, an optical pickup unit which can record, reproduction and erase information in/from an information recording medium has tracks with different pitches, the dividing means has at least a part of a dividing boundary line placing between an end of a 1st order diffraction light with the largest diffraction angle and an end of a 1st order diffraction light with the smallest diffraction angle of the reflected laser beam.

Abstract: An optical pickup apparatus according to the present invention includes: a first light source for emitting a first light flux; a second light source for emitting a second light flux; a third light source for emitting a third light flux; and an objective optical element. The objective optical element has an optical surface including at least two areas provided with optical path difference providing structures. The objective optical element converges the first to third light fluxes each passing through the predetermined areas on the objective optical element onto respective information recording surfaces of the first to third optical disks. One of the optical path difference providing structures includes a first basic structure and a second basic structure which are predetermined optical path difference providing structures and overlap with each other.

Abstract: An object of the invention is to provide a splitter, a light emitter, and an optical pickup apparatus which can realize a stable track servo. Because of the structure of an optical system including an objective lens (27) and a hologram pattern (25), even when the hologram pattern (25) is irradiated with a reflected light from one recording layer other than another recording layer in a focused state, first and second TES splitting portions (35, 36) are not irradiated with the reflected light from the one recording layer, but the reflected light is led to an axis vicinity portion (38) only. Accordingly, light reception by first and second TES light receiving portions (45, 46) is prevented, accurate track position information and deviation information can be positively acquired, and troubles such as the objective lens (27) being driven beyond a movable range can be eliminated.

Abstract: A diffraction element for an optical pick-up apparatus is capable of precisely controlling the tracking of the pick-up apparatus. The diffraction element includes a diffraction grating divided into a first, a second, and a third region. The second region is located between the first and third regions. Any one of the first region and the third region is inclined at a predetermined angle ? with respect to the second region.

Abstract: The present invention is related to a chromatic aberration-correcting element which allows the adoption of BDs even when DVD/CD light beams are incident. The chromatic aberration-correcting element has a diffractive structure formed thereon, which can correct chromatic aberration in BD wavelength light beams in addition to adopting DVD/CD wavelength light beams. Also provided is an optical pickup device whose structure is simplified by employing the chromatic aberration-correcting element.

Abstract: An optical pickup apparatus and an optical disc apparatus are adapted to raise the efficiency of utilization of the lasers of the apparatus for accurately detecting tracking errors by raising the intensity ratio of the beam of the 0-th order to the beams of the ±1st orders produced by splitting of the laser beam of the wavelength to be subjected to division by three. The optical pickup apparatus includes a light emitting section for emitting a first laser beam having wavelength ?1 and a second laser beam having wavelength ?2 different from the wavelength ?1.

Abstract: An objective optical system focuses light from a light source onto at least two different types of optical recording media having different substrate thicknesses in order to record or reproduce information on the optical recording media by using a variable refractive power element and an objective lens. The variable refractive power element may be a liquid crystal element with concentric zones that serves as a transparent plate having no convergence effect when no voltage is applied when selecting an AOD, DVD, or CD and as a converging lens when a voltage is applied when selecting a BD. Alternately, the variable refractive power element may electrically vary the refractive index of a nanoparticle dispersion or at least one liquid of a two-liquid lens element. A diffractive optical element may be used to assist in focusing light to four recording media. An optical pickup device includes the objective optical system.

Abstract: An optical pickup apparatus is provided with a dividing element having a plurality of regions. The dividing element is capable of dividing a light flux reflected by the optical disc into a plurality of light fluxes having different outgoing directions. Each region of the dividing element and light receiving parts of a light detector are structured such that when a target information recording layer of the optical disc is brought into focus, a light flux reflected from the target information recording layer is focused on the light receiving parts of the light detector, and a light flux reflected from other information recording layer than the target information recording layer is not irradiated onto the light receiving parts of the light detector.

Abstract: An information recording/reproducing device includes a radiation light source 1 such as a semiconductor laser, a spatial modulation element 6 that splits laser light 2 emitted from the radiation light source 1 into a large number of diffracted light rays, and an objective lens 7 that converges the large number of diffracted light rays onto different points. The laser light 2 emitted from the radiation light source 1 is split into a large number of diffracted light rays by the spatial modulation element 6, the large number of diffracted light rays are converged onto different points in the photosensitive layer 8b of the information recording medium 8 by the objective lens 7, and information is recorded in the photosensitive layer 8b of the information recording medium 8, using an assembly of these converging points. Accordingly, it is possible to provide an information recording device capable of realizing high-contrast recording in which stray light or diffraction has no influence during signal recording.

Abstract: A diffraction element for use in an optical pick-up is capable of calculating a TE signal more stably irrespective of any assembly error in optical elements. The diffraction element of the invention is divided into three areas, a first, a second, and a third area. Each area comprises a diffraction grating with a predetermined period, and the second area is provided between the first area and the third area. The diffraction grating of the first area is substantially parallel to the diffraction grating of the third area, and the diffraction grating of the second area is substantially perpendicular to the diffraction gratings of the first and the third area.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical pickup apparatus comprises first, second and third light sources to emit light fluxes of wavelength ?1, ?2 and ?3 for conducting recording and/or reproducing information for first, second and third optical information recording mediums having respective protective substrates of thickness t1, t2 and t3 and a diffractive optical element located on a common optical path for the first, second and third light sources. A converged-light spot is formed on the first optical information recording medium with m-th order diffracted-light ray of the wavelength ?1, on the second optical information recording medium with n-th order diffracted-light ray of the wavelength ?2, and on the third optical information recording medium with k-th order diffracted-light ray of the wavelength ?3 generated by the diffractive optical element respectively, wherein one of m, n and k is different from one of other two numbers.

Abstract: An optical pickup apparatus is provided with a dividing element having a plurality of regions. The dividing element is capable of dividing a light flux reflected by the optical disc into a plurality of light fluxes having different outgoing directions. Each region of the dividing element and light receiving parts of a light detector are structured such that when a target information recording layer of the optical disc is brought into focus, a light flux reflected from the target information recording layer is focused on the light receiving parts of the light detector, and a light flux reflected from other information recording layer than the target information recording layer is not irradiated onto the light receiving parts of the light detector.

Abstract: A diffractive optical element for dividing a light emitted from a light source into a main beam and at least one sub-beam, an objective lens for focusing the beams on a disk-shaped optical recording medium with spiral tracks, and a photodetector for receiving the beams reflected from the optical recording medium are provided. At least a part of the diffractive optical element includes a diffraction grating divided into four or more plural areas by three or more plural lines in parallel with a direction corresponding to a tangential direction of the optical recording medium, and in two adjacent areas among the plural areas, phases of the lattices are shifted by n to each other.

Abstract: An optical system for use in an optical pickup apparatus comprises a first optical surface having a superposition type diffractive structure including a plurality of ring-shaped zones which are formed concentrically around an optical axis, wherein each ring-shaped zone is composed of a plurality of stepped sections stepwise, and a second optical surface having a diffractive structure including a plurality of ring-shaped zones which are formed concentrically around an optical axis, wherein each of the plurality of ring-shaped zones are divided by a stepped section to generate a diffractive light ray of diffractive order whose absolute value is not small than 1 for the light flux.

Abstract: An optical reading unit which ensures that address information recorded as guide groove wobbles on an optical recording medium is easily played back. A light-receiving device (20) for detecting returning light from the optical recording medium has detection areas (21A to D) delimited by a plurality of split lines (22), (23), and (24). The position of one of the split lines functioning as a detection reference line is changed according to the position of a returning light spot S on a light-receiving surface (21) of the light-receiving device (20) and push-pull signals (PP1 to 3) are acquired by calculating the difference between signals received on two detection areas delimited by the split line to eliminate common-mode components.

Abstract: An optical pickup device is adapted to read information signals from optical recording media of two different types such as a “DVD” and a “CD” for which two light beams with different wavelengths are used and comprises a photodetector having a single light receiving section that can be shared by optical recording media of two different types. Both the light beam reflected from the signal recording surface of the “DVD” 106a and the light beam reflected from the signal recording surface of the “CD” 106b are diffracted by the diffraction element 6 and focused to a same spot on the light receiving surface of the photodiode of a photodetector 7.

Abstract: An optical pickup apparatus for reading/reproducing data on an optical recording medium, includes a plurality of laser diodes configured to emit laser light of different wavelengths respectively, a photodetection device configured to detect each laser light, a diffraction type-optical device configured to transmit each laser light from the plurality of laser diodes to the optical recording medium, and to diffract the light reflected from the optical recording medium to the photodetection device, and wherein the diffraction type-optical device includes a plurality of reflecting type-diffraction elements configured to reflect and diffract each laser light of a corresponding wavelength in the laser light from the plurality of light diodes, to the photodetection device so that the photodetection device can detect each laser light of the corresponding wavelength for monitoring each of the laser light, and a suppression setting device configured to set each of the plurality of reflecting type-diffraction elements t

Abstract: A hybrid objective lens has a refractive lens and a diffractive optical element constructed by plural coaxial ring-shaped zones on at least one optical surface thereof. When n1, n2 and n3 each is a diffraction order of a diffracted ray having a maximum light amount among diffracted rays of each of first, second and third light flux having wavelength ?1, ?2 and ?3 when respective light flux comes to be incident into the diffractive structure respectively, the following formulas are satisfied: |n1|>|n2|, and |n1|>|n3|, and the hybrid objective lens converges a n1-th, n2-th and n3-th order diffracted ray of the first, second and third light flux onto an information recording plane of each of the first, second ant third optical information recording medium respectively so as to form an appropriate wavefront within respective prescribed necessary image side numerical apertures.

Abstract: Provided are optical information processing apparatus and method. In the optical information processing apparatus and method, when the recording regions in which optical information is recorded in an angular multiplexing scheme overlap with each other, a recording angle and a recording position for optical information is adjusted so as to improve reproducing efficiency of readout beams reproduced from the overlap recording regions, so that heights of “null” for diffraction energy reproduced from the recording regions and overlap recording regions can be lowered.

Abstract: An optical pickup device for reading a signal recorded in an optical disc including a first signal recording layer and a second signal recording layer, comprising: a laser diode configured to emit laser light; and a diffraction grating configured to be applied with laser light emitted from the laser diode, and to generate a main beam including zero order light, and a sub beam including plus first order light and minus first order light, such that a ratio of light amount of the sub beam to that of the main beam is substantially 1:7.

Abstract: An objective lens of an optical pickup apparatus converges a divergent light flux onto an information recording surface. The following conditional formula is satisfied: |?SA1/?U|·|?U|+|?SA2/?T|·|?T|?0.07 ?rms where ? represents a wavelength of a light source, ?SA1/?U represents a change of a spherical aberration for an object-to-image distance change ?U (|?U|?0.5 mm) and ?SA2/?T represents a change of spherical aberration for a temperature change ?T (|?T|?30° C.), the object-to-image distance is a distance between the light source (a light emitting point) and the information recording surface.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical head includes the following: a light beam separator (35) that includes substantial interference regions for light that is reflected from an information recording medium and travels in a straight path and ±first-order diffracted light produced by information tracks of the information recording medium, and diffracts each of plural light beams in regions (32a, 32b) of the substantial interference regions, where the amount of light is changed by a change in the relative angle between the information recording medium and the objective lens and by a shift of the objective lens in the radial direction of the information recording medium; a light-receiving element (36a, 36b) for receiving the light beam that is reflected by the information recording medium and separated by the light beam separator (35); and an arithmetic circuit that corrects a value of an electrical signal detected by the light-receiving element (36a, 36b) in accordance with a radial position signal corresponding to the amount of shift of