Abstract: A guide-layer separated optical recording medium includes a guide layer with a guide track formed therein and a plurality of recording layers, these layers being separately deposited from each other. A layer position information region for indicating position information of each of the recording layers, is formed on the guide track within a different range of the guide layer for each of the recording layers. Each of the recording layers includes a preformat region having a predetermined signal written on a record track along the guide track, and the preformat region on each of the recording layers is provided in a region corresponding to the layer position information region. An optical recording medium drive apparatus and a recording layer access method for the guide-layer separated optical recording medium are also provided.

Abstract: A reproducing apparatus includes: a first laser irradiation section irradiating an optical recording medium having a bulk recording layer and recording marks formed by focusing a laser beam on each predetermined layer position in the recording layer, with a first laser beam through an objective lens; a focus position adjusting section adjusting a focus position of the first laser beam; a beam receiving section receiving a reflected beam of the first laser beam from the marks and generating a light receiving signal; a reproducing section reproducing information recorded with the marks based on the light receiving signal; and a control section performing control to allow the focus position in reproduction of the information to correspond to a position shifted by a certain distance to an upper layer side from a focus position of the laser beam in forming the mark at the layer positions as a reproducing object.

Abstract: Provided are an optical head and an optical information device capable of inhibiting the temperature rise of a photodetector. An optical head (10) includes a semiconductor laser (101) which emits a luminous flux, an objective lens (105) which focuses the luminous flux emitted from the semiconductor laser (101) on the optical disk (21), and a photodetector (120) which detects the luminous flux reflected by the optical disk (21). The photodetector (120) includes a light receiving part (123) which receives the luminous flux reflected by the optical disk (21), a package (125) which covers the light receiving part (123), and a heat transfer adhesion layer (124) disposed between the package (125) and the light receiving part (123). The heat transfer adhesion layer (124) is formed in a region that is on the light receiving part (123) and includes a light path through which the luminous flux reflected by the optical disk (21) passes.

Abstract: When information is recorded or reproduced on or from an optical information medium having three or more recording layers using blue light, interference by another layer light is reduced and, when information is reproduced from an optical information medium using red light, an S/N ratio is held excellently high.

Abstract: In an optical disk including at least a rewritable phase change material and comprising a recording layer having a reflectivity of more than 15%, an address output value as an address pit signal component occupying in a reproduced signal in a non recording state is prescribed to be 0.18 though 0.27 or a numerical aperture of an address pit signal occupying in a reproduced signal in a non recording state is prescribed to be more than 0.3.

Abstract: Provided is an optical pickup apparatus that stably operates by accurately detecting a fluctuation in a light amount of a laser beam caused by movement of a collimating lens. In an optical pickup apparatus of the present invention, part of a laser beam emitted from a laser device is transmitted through a reflective mirror and detected by a laser beam FMD. An output of the laser device is adjusted based on the output from the FMD. Even when a collimating lens moves during the operation of the apparatus, the change in the light amount of the laser beam caused by the movement is immediately detected by the FMD and the output of the laser device is adjusted. Thus, the light amount of the laser beam radiated on an optical information recording medium is kept constant along a time axis. Accordingly, the optical pickup apparatus can stably perform reading and writing.

Abstract: Disclosed is an objective lens that favorably focuses multiple laser beams having different wavelengths on information recording layers of optical discs, and an optical pickup apparatus including the lens. The objective lens of the invention is provided with a first region for focusing laser beams of the BD, DVD and CD standards. The first region is provided with an annular zone step having a height calculated on the basis of a wavelength of the laser beam of the BD standard, and thus causes chromatic aberration of the laser beam of the DVD standard. This chromatic aberration corrects spherical aberration occurring due to a difference in thickness between coating layers of optical discs. In the invention, the curve surface shape of the first region is adjusted so that the BD and DVD standards can share the aberration for reducing the aberration of the laser beam of the DVD standard.

Abstract: An optical disc device and information recording/reading method for an optical disc in which a recording layer is formed through volume recording by aligning recording tracks, which hold information, in a homogenous recording region that does not internally have a layer defining a recording position. The information recording method includes a step in which a first recording layer forming a complex recording layer is formed by forming a recording track while recording information by focusing a main beam at a predetermined depth position in the recording region, and a step in which a second recording layer forming the complex recording layer is formed by forming a recording track while recording information by focusing the main beam at a depth position that is separated from the first recording layer in a depth direction by a depth offset greater than ? of a wavelength of the main beam.

Abstract: Provided are a single beam optical pickup device and a disc drive including the optical pickup device. The optical pickup device includes a light controlling device that prevents or limits stray light generated from a medium from being incident on a light sensor. The light controlling device may further include an additional auxiliary light sensor so as to reuse effective light among diffracted light.

Abstract: Provided is a method of, in movement between recording layers of an optical disc, resolving a problem caused by an increase in spherical aberration change as a result of widening of a layer interval at which the movement is made and executing appropriate interlayer movement. An upper limit value is defined for a recording layer interval at which the interlayer movement can be made, and if a layer interval from a moving-source layer to a moving-target layer is equal to or larger than the upper limit value, the interlayer movement and spherical aberration correction are once carried out where a predetermined recording layer for which a layer interval is less than the upper limit value is defined as a temporary shelter layer, and the processing is repeated with this temporary shelter layer defined as a new moving-source recording layer to thereby realize favorable interlayer movement to the target layer.

Abstract: The optical storage medium comprises a substrate layer and a data layer disposed on the substrate layer, the data layer having a mark/space data structure being arranged in tracks, wherein on a first track, the marks are enlarged in length and the spaces are shortened in length, and on an adjacent track, the marks are shortened in length and the spaces are enlarged in length. The track pitch between adjacent tracks is particularly below a diffraction limit of ?/2*NA of a pickup for reading of the data.

Abstract: An optical pickup having a first diffractive optical element that acts on light of a specific wavelength, the first diffractive optical element being arranged in an optical path for guiding reflected light from an optical disk to a photodetector. The photodetector comprises a first detector including a first main light receiver divided into a two-by-two square matrix, and a second detector including a second main light receiver divided into a two-by-two square matrix, the second detector being arranged in a row with the first detector. When the light of a specific wavelength is used, zero-order light of the first diffractive optical element is received by the first main light receiver, +first-order light (or ?first-order light) diffracted by the first diffractive optical element is received by the second main light receiver, and a tracking error signal is generated using an output signal from the second main light receiver.

Abstract: A recording apparatus includes: a light illumination and light sensing unit configured to illuminate an optical disc recording medium including a reference surface having address information recorded and a recording layer, with recording light and light for position control; a recording unit which performs recording on the recording layer; and a control unit which controls, when data instructed to be recorded is to be recorded from an instructed recording start address, the recording unit to perform recording of dummy data on an area adjacent to a front side at least from the recording start address over a range of equal to or greater than the maximum spot deviation amount between an illumination spot of the light for position control and an illumination spot of the recording light and to perform recording of the data instructed to be recorded in succession to a recorded area of the dummy data.

Abstract: An optical disk apparatus according to the present invention includes: a drive selector 28 that makes a switch between a setting for sending a drive signal generated by a focus drive generation section 25 to a focus drive section 29, and a setting for sending a drive signal generated by a focus filter 27 to the focus drive section 29; and a lock-in timing detection section 21 that, upon a light amount signal detected by a light amount signal detection section exceeding a predetermined light amount level, determines that an optical spot reaches a vicinity of any of recording layers, and sends to the drive selector 28 a focus lock-in timing instruction for switching to the setting for sending the drive signal generated by the focus filter 27 to the focus drive section 29. Such configuration provides an optical disk apparatus allowing a stable focus lock in operation to be performed without using a layer determination signal when locking a focus into a recording layer of an optical disk.

Abstract: To provide an information recording medium which is capable of reducing damage to a recording layer while improving environmental resistance of the recording layer and which enables information to be recorded or reproduced at a high density and a high sensitivity, an optical information recording and reproducing apparatus, an optical information recording and reproducing method, and a manufacturing method of an information recording medium.

Abstract: A first laser light source emits first laser light of a predetermined wavelength, and a second laser light source emits second laser light of a wavelength different from the wavelength of the first laser light. Reflected light of the first and second laser light is entered into an astigmatism portion. The astigmatism portion generates first and second focal lines. A light separating portion separates light fluxes of the reflected light of the first and second laser light from each other, the light fluxes obtained by dividing the reflected light of the first and second laser light into four light fluxes. The light separating portion is constituted of at least one prism having plural slopes, and the photodetector is provided with a common sensor portion which receives the light fluxes of the reflected light of the first and second laser light.

Abstract: An optical head device mounted in an optical disc device. The optical head device is provided with a diffractive optical element and a photodetector. The diffractive optical element has: a primary diffraction region at a location on which the positive and negative first-order components and some of the zero-order component of a reflectively diffracted light beam are incident; and secondary diffraction regions at locations on which the rest of the zero-order component but none of the positive or negative first-order components of the reflectively diffracted light beam are incident. A main light-receiving section of the photodetector receives the zero-order component of a transmissively diffracted light beam that has passed through the primary diffraction region and the secondary diffraction regions.

Abstract: An optical disk discriminating method and an optical disk device which can detect reflected rays for making discrimination among kinds of optical disks with high accuracies. By switching a plurality of lasers and moving a spherical aberration corrector while moving an objective lens to cause it to approach or keep away from an optical disk, rays reflected light from the optical disk can be detected with high accuracies. Discrimination among the kinds of a plurality of optical disks can be made on the basis of signals generated from the detected reflected rays. This ensures that the kind of an optical disk can be determined through one operation of sweeping.

Abstract: An optical recording medium includes a recording layer in which recording of a mark is selectively performed in a depth direction by irradiation of first light, and the mark is formed in multilayer form; and a reflection film reflecting second light of a wavelength different from a wavelength of the first light, and provided on a lower layer side of the recording layer.

Abstract: An astigmatism element converges laser light in first and second directions to generate focal lines. A spectral element makes propagating directions of light fluxes entered into first through fourth areas different from each other to disperse the four light fluxes from each other. The direction along which the first and second areas are aligned is in parallel to a direction of a track image of a recording medium projected onto the spectral element. Each of the first and second areas has a surface area larger than a surface area of each of the third and fourth areas, and a boundary portion between the first and second areas, and the third and fourth areas includes a straight portion extending in a direction perpendicular to the direction of the track image.

Abstract: An optical information recording/reproducing device includes a liquid optical element containing a liquid crystal polymer layer in an optical head. A liquid crystal optical element drive unit drives a liquid crystal optical element having a first pattern electrode divided into a plurality of region at one side of the liquid crystal polymer layer in the optical axis direction. The first pattern electrode includes a first region arranged to surround the optical axis and second to ninth regions arranged outside the first regions in such a manner that the circumference is divided eight portions. The liquid crystal optical element drive unit applies an effective voltage to each region. The voltage applied to the respective regions of the pattern region of the liquid crystal optical element is decided in a short time so as to optimize the quality of the reproduction signal.

Abstract: A method of designing an optical element to be used for an optical system in which each of a plurality of light beams having different design wavelengths passes through the optical element is provided. The method includes determining at least two types of optical path difference functions including first and second optical path difference functions in such a manner that proportion, brought by the first optical path difference function, between diffraction orders at which diffraction efficiencies of the plurality of light beams are maximized is different from proportion, brought by the second optical path difference function, between diffraction orders at which diffraction efficiencies of the plurality of light beams are maximized, and obtaining a shape defined by combining the at least two types of optical path difference functions so as to apply the obtained shape to at least one surface of surfaces of the optical element.

Abstract: An optical pickup device is provided which is compatible with at least two types of optical disc standards having different NAs and which controls an effective NA when a light beam for an optical disc standard having a relatively small NA is converged, thereby forming a desired spot. An inner part 131B and an outer part 131F of an objective lens element 143 are provided with diffraction structures different from each other. A condition (1), DO11×DO12>0, and a condition (2), DO21×DO22<0, are satisfied (DO11(DO21) is the diffraction order of the diffracted light beam having the highest diffraction efficiency among light beams of the wavelength ?1(?2) diffracted by the diffraction structure on the inner part; and DO12 (DO22) is the diffraction order of the diffracted light beam having the highest diffraction efficiency among light beams of the wavelength ?1 (?2) diffracted by the diffraction structure on the outer part).

Abstract: A method for evaluating a read signal obtained by irradiating a medium with a laser beam through an objective lens and reading data from the reflected laser beam by a PRML detection method is provided. The method includes: a sampling step of sampling the data obtained from the reflected laser beam at clock timings to obtain sampled values; and a step of, when a constraint length of a PR class in the PRML detection method is an even number, computing an intermediate sampled value for evaluation using at least adjacent two of the sampled values arranged in the order sampled at the clock timings. The provided method is an objective evaluation method when the PRML detection method is used, whereby the selection of a recording medium and a reading apparatus is facilitated.

Abstract: Provided is an objective lens, which is provided in an optical pickup including a spherical aberration correction mechanism which performs a spherical aberration correction with respect to laser light applied to a recording layer of an optical recording medium, having the recording layer on which information can be recorded at a plurality of positions in a depth direction, via the objective lens, and a tilt correction unit which varies a lens tilt angle which is a tilt angle of the objective lens, thereby performing a tilt correction.

Abstract: An optical-pickup apparatus includes: a laser diode having a first-laser element, which emits a first-laser beam, and a second-laser element, which emits a second-laser beam having a wavelength shorter than a wavelength of the first-laser beam, arranged in the same package; an objective lens to condense the first- and second-laser beams emitted from the laser diode to signal-recording layers of first- and second-optical discs, respectively, the second-optical disc being of a standard different from a standard of the first-optical disc; and a collimating lens arranged in an optical path between the laser diode and the objective lens, the collimating lens configured to change the first- and second-laser beams from divergent light to parallel light, the collimating lens being inclined with respect to optical axes of the first- and second-laser beams so that astigmatism in the first- and second-laser beams is corrected.

Abstract: A compound objective lens, an optical head device, an optical information device, and an information processing device that can inhibit the occurrence of aberration even when a light beam source wavelength shifts from the designed value. A diffraction structure having a sawtooth or stepwise cross section is formed in the region (R10) and region (R20). The height of the sawtooth or stepwise cross section formed in the region (R10) provides a light beam, which has a predetermined wavelength, with a difference in optical path length of N times the predetermined wavelength, as compared with a case of propagation in air. The height of the sawtooth or stepwise cross section formed in the region (R20) provides the light beam, which has the predetermined wavelength, with a difference in optical path length of J times the predetermined wavelength, as compared with a case of propagation in air.

Abstract: An optical information recording/reproducing apparatus for an optical disc using a light beam having a wavelength of ? including: an objective lens that converges the light beam onto a recording surface of the optical disc and satisfies a condition: 0.48 < d · ( n - 1 ) f 2 < 0.75 ( 1 ) where f represents a focal length (unit: mm) of the objective lens with respect to the wavelength ?, d represents a thickness (unit: mm) of the objective lens along an optical axis of the objective lens, and n represents a refractive index with respect to the wavelength ?; a photoreceptor to receive the beam reflected from the optical disc; a detector to detect quality of a signal, and an objective lens driving unit to tilt the objective lens in a direction to improve the quality of the signal based on a result of detection by the detector.

Abstract: An optical information recording reproduction apparatus includes: a first light beam source; a second light beam source emitting a beam with a wavelength shorter than that of the first light beam source; and an object lens condensing the beams from the first and second light beam sources to an optical information recording medium. When information is recorded in the optical information recording medium, a recording beam is emitted from the first light beam source and a beam used to generate a signal for controlling a position of the object lens is emitted from the second light beam source. When the information of the optical information recording medium is reproduced, a reproduction beam is emitted from the second light beam source.

Abstract: An optical pickup device includes a semiconductor laser for emitting laser light, an objective lens for irradiating luminous flux emitted from the semiconductor laser to an optical disc, a branching element having a plurality of regions for branching luminous flux reflected from the optical disc to a plurality of fluxes, and a photodetector having a plurality of light receiving parts which receive luminous flux branched by said branching element. Luminous flux which enters at least two regions arrayed along a direction which is made substantially coincident with a tangential direction of the optical disc in regard to substantially a center of the branching element is arranged along a direction which is made substantially coincident with a radial direction of the optical disc on the photodetector.

Abstract: An optical pickup includes a first source which emits a first beam with a first wavelength; a second source which emits a second beam with a wavelength shorter than the first wavelength; a first collimate lens which collimates the first beam; a second collimate lens which collimates the second beam; a first objective lens which converges the first collimated beam onto an optical disc; and a second objective lens which converges the second collimated beam onto the disc. The first and second objective lenses are arranged in the disc radial direction. The second objective lens is arranged closer to the side of the disc outer circumference than the first objective lens. The first collimate lens is arranged on the right-hand side when the second objective lens is viewed from the first objective lens. The second collimate lens is arranged on the left-hand side when the first objective lens is viewed from the second objective lens.

Abstract: Has an object of providing an optical pickup capable of realizing tracking control or focus control at a higher level of precision even when relative positions of a light source and a light detector are shifted due to a change in the environmental temperature, long-term deterioration or the like. The optical pickup includes a base member; a light source, fixed to the base member, for emitting a laser beam; an objective lens for collecting the laser beam onto an optical disc; a light detector, fixed to the base member, for detecting the laser beam reflected by the optical disc; fixing means for fixing the light source and/or the light detector to the base member; and a light blocking section for blocking a central portion of the laser beam in a circular shape on an optical path between the collimator lens and the light detector.

Abstract: An optical pickup which is configured to suppress resonances in the objective lens which are caused during tilt control of the objective lens is provided. The optical pickup device includes an objective lens, a lens holder for retaining the objective lens, and an actuator for rotating the lens holder to control tilt of the objective lens. The objective lens is bonded to the lens holder via adhesives applied at a plurality of adhesion positions. The adhesion positions at which the objective lens and the lens holder are bonded are asymmetrical relative to a plane which includes the rotation axis of the lens holder and the optical axis of each objective lens.

Abstract: An optical pickup device including: a laser diode for emitting laser light; an objective lens which irradiates an optical beam emitted from the laser diode; an actuator which displaces the objective lens in a radius direction of the optical disc; a grating for branches an optical beam reflected by an information recording layer into plural regions; and one photodetector having plural light receiving parts for receiving the branched optical beams, wherein the photodetector has a first light receiving part which detects zero-th order grating diffracted light and plural second light receiving parts which detecting grating diffracted light having an order not less than that of ±first order grating diffracted light; a detected signal of the zero-th order grating diffracted light is defined as a reproduction signal; and a detected signal of the grating diffracted light is defined as a signal for servo controlling.

Abstract: The present invention relates to an aberration correcting device comprising: an aberration correcting element which modulates the phase of incident light; and a position adjusting section which can move the aberration correcting element in a direction perpendicular to an optical axis of the incident light, wherein the aberration correcting element includes first and second aberration correction plates, each of which is disposed such that the phase of transmitted light beam differs with transmission position of the incident light beam with the same phase, and the aberration correcting element has a reference arrangement which is an arrangement of the first and second aberration correction plates in which the light beams transmitted through the aberration correcting element have the same phase, and assuming that a point on the first aberration correction plate crossing the optical axis is a point Oa and a point on the second aberration correction plate crossing the optical axis is a point Ob in the reference ar

Abstract: A laser device includes a semiconductor laser, a signal generating circuit generating a pulse signal for driving the semiconductor laser, an amplifying circuit amplifying the pulse signal, and a control circuit unit provided between the amplifying circuit and the semiconductor laser and controlling the pulse signal by letting alternating-current components of the pulse signal pass through and removing at least part of direct-current components of the pulse signal.

Abstract: An optical pickup device comprises a first objective lens fixed on a lens holder and configured to focus a first laser beam on a signal recording layer provided in an optical disc, the lens holder supported by support wires so that the lens holder is movable toward a signal surface of an optical disc and in a radial direction of the optical disc, and a second objective lens fixed on the lens holder and configured to focus a second laser beam on a signal recording layer provided in an optical disc. Bearing surfaces of the first and second objective lenses are tilted at predetermined angles, respectively, generation directions of coma aberrations by the first and second objective lenses are broadly divided by a simple method, and the objective lenses are fixed with the directions of the coma aberrations aligned.

Abstract: An optical pickup that can be downsized is suggested.

Abstract: Provided is an optical pickup including: a light-source emitting a light-beam; an objective lens collecting the light-beam on a desired recording layer among one or two recording layers or more installed in an optical disc and where spirally- or concentrically-shaped tracks are formed; a lens-moving unit moving the objective lens in a tracking direction toward at least an inner-circumference or outer-circumference side; a light splitting device splitting a reflected light-beam into reflected light-beams and propagating the light-beams; a light-detecting device generating central, inner-circumference-side, and outer-circumference-side light-detecting signals according to received light amounts thereof by central, inner-circumference-side, and outer-circumference-side light-detecting areas, receiving central, inner-circumference-side, and outer-circumference-side portions of an image of the reflected light-beam in the radial direction and allowing a signal processing unit to generate a tracking error signal by

Abstract: In an optical pickup equipped with a semiconductor laser, electro-optical components such as a lens, and an objective lens drive device, the objective lens drive device includes objective lenses, a holder holding the objective lenses, a focusing coil, and tracking coils. The focusing coil is wound in parallel to the optical surface of the objective lens, and formed in a parallelogram shape having inclined portions provided near the tracking coils. The two tracking coils are placed on diagonal portions of the lens holder.

Abstract: An objective lens including: a first region to respectively converge first and second light beams onto recording surfaces of first and second optical discs; and a second region located outside of the first region and configured to converge the first light beam onto the recording surface of the first optical disc and not to converge the second light beam onto the recording surface of each of the first and second optical discs, and wherein the first region is divided into a plurality of refractive surface zones concentrically formed about an optical axis and has a first step, a diffraction order at which a diffraction efficiency is maximized for each of the first and second light beams passing through the first step in the first region is a first order, and the objective lens satisfies a condition: 0.80<((Sout?Sd)/Sout)2/?in<1.45??(1).

Abstract: In an optical disk including at least a rewritable phase change material and comprising a recording layer having a reflectivity of more than 15%, an address output value as an address pit signal component occupying in a reproduced signal in a non recording state is prescribed to be 0.18 though 0.27 or a numerical aperture of an address pit signal occupying in a reproduced signal in a non recording state is prescribed to be more than 0.3.

Abstract: Provided are an objective lens with enhanced transmittance and an optical pickup apparatus which can record and/or reproduce information properly for three kinds of discs with different recording densities, even if a single lens is used as the objective lens. When all the expressions (1) to (3) are satisfied, excellent aberration characteristics can be obtained for the three kinds of discs: ?0.02?m1?0.02 (1); 0?(WD1?WD2)?1.57 m2+0.123 or 1.57 m2+0.24?(WD1?WD2)?0.7 (2); and 0?(WD1?WD3)?1.79 m3+0.333 or 1.66 m3+0.508?(WD1?WD3)?0.7 (3).

Abstract: An optical unit includes an optical system for shining a laser beam on an optical recording medium having a recording layer and a focus control reference surface. The optical system is composed of an objective lens for focusing a recording/reproducing beam emitting from a first light source in the recording layer and focusing a focus control beam emitted from a second light source on the focus control reference surface, a first lens system disposed along an optical path of the recording/reproducing beam and capable of discretely varying a focus position of the recording/reproducing beam in a direction of a thickness of the recording layer, and a second lens system disposed along an optical path common to the recording/reproducing beam and the focus control beam and capable of continuously varying focus positions of the recording/reproducing beam and the focus control beam in a direction of a thickness of the recording layer.

Abstract: The present invention relates to a high data density optical recording medium. The invention further relates to an apparatus for reading from such an optical recording medium. The optical recording medium has marks that are arranged in tracks. The tracks have a cross section with a curved shape and protrude above a surface of the optical recording medium.

Abstract: An optical system of an optical pick-up including a resin coupling lens and a resin objective lens with NA larger than 0.8, wherein, magnification ? satisfies a condition: ?0.13<?<?0.08, a focal length f of the objective lens satisfies a condition: 1.15<f<1.50, the objective lens has an annular zone structure on at least one surface of the objective lens, and the annular zone structure has a plurality of annular zones and has steps each of which extends in a direction of an optical axis of the objective lens and is formed at a boundary between adjacent ones of the plurality of annular zones to cause a predetermined optical path length difference between a light beam passing inside the boundary and a light beam passing outside the boundary, and the optical system of an optical pick-up satisfies a condition: 0.065 < ( ( ? ? 0.95 - 1.00 ) ( ? ? 0.00 - 1.00 ) × d 0 × n f 2 × ( NA 0.85 ) 4 ) P ave + 1 L < 0.

Abstract: An optical information recording/reproducing optical system, comprising a light source; an optical element converting a laser beam into a substantially collimated beam; and an objective lens, wherein a wavelength ? (unit: nm) of the laser beam falls within a range of 400<?<410, the optical element and the objective lens are made of same resin materials or different resin materials having a glass transition temperature of Tg>115° C., each of optical surfaces is configured not to have an optical thin film which contains at least one of or elements of titanium, tantalum, hafnium, zirconium, niobium, molybdenum and chromium, each of optical surfaces of the optical element is provided with an antireflection film made of one of or a mixture of at least two of silicon oxide, aluminum oxide, aluminum fluoride and magnesium fluoride, and a following condition is satisfied. ? i = 1 n - 1 ? ( 1 - R ( BL ) ? i 100 ) - ? i = 1 n - 1 ? ( 1 - R ( UV ) ? i 100 ) > 0.

Abstract: An optical pickup device is provided with a spectral element which imparts diffraction in such a manner that four light fluxes of the first laser light are separated from each other, when a light flux of the first laser light and a light flux of the second laser light reflected on a recording medium having laminated recording layers and servo layers are divided into four by a first straight line in parallel to a converging direction by an astigmatism element, and a second straight line perpendicular to the first straight line, and that the four light fluxes of the first laser light propagate on an outer side than the light flux of the second laser light; and a photodetector including a first sensor group which receives the first laser light, and a second sensor group which receives the second laser light.

Abstract: An optical information recording/reproducing optical system where resin material has Tg>115° C., first, second and third films are on an optical disc side of an objective lens and surfaces of an optical element, respectively, a light source side of the objective lens has a fourth film having four or more layers not containing Ti, each of the first, second and third films includes a non-high refractive index layer made of one of silicon oxide, aluminum oxide, aluminum fluoride and magnesium fluoride or a mixture of at least two of them, each of the first, second and third films is not made of one of Ti, Ta, Hf, Zr, Nb, Mo and Cr, a layer of the fourth film closest to a base material is the non-high refractive index layer. The fourth film satisfies 350<?max(2)<420 and 600<?min(2)<750, and reflectivity thereof decreases monotonously.

Abstract: Provided are an optical pickup apparatus and an objective lens which can appropriately record and/or reproduce information on three types of discs with different recording densities and improve the light-utilization efficiency using a simple structure. A first optical path difference providing structure is formed on an optical surface of the objective lens. The first optical path difference providing structure is a step structure in which plural ring-shaped step units each including the same number of steps are arranged concentrically about the optical axis as the center. The width w1 in the direction perpendicular to the optical axis of the highest step or the lowest step in at least one step unit in the step structure is approximately half of the average value w2 of two steps at both sides of the highest step or the lowest step in the direction perpendicular to the optical axis.