Abstract: An optical pickup includes an objective lens, a lens holder which holds the objective lens, a focusing coil attached to the lens holder having the winding axis directed at the optical axis of the objective lens, and a magnet provided opposite the side surface of the lens holder. A protruding portion is attached to the side surface of the lens holder at a side apart from the objective lens with respect to the optical axis direction of the objective lens farther than the focusing coil.

Abstract: An optical pickup apparatus comprising: a diffraction grating that a laser beam enters, the diffraction grating being configured to generate a main beam that is 0th order light and sub-beams that are +1st order diffracted light and ?1st order diffracted light; an objective lens configured to focus the main beam and the sub-beams onto a signal recording layer; a main-beam light-receiving portion that the main beam reflected by the signal recording layer is applied to; and sub-beam light-receiving portions that the sub-beams reflected by the signal recording layer are respectively applied to, each light-receiving area of the sub-beam light-receiving portions being smaller than a light-receiving area of the main-beam light-receiving portion.

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 head device compatible to different types of optical discs and capable of guaranteeing a sufficiently wide dynamic range for a low density optical disc, and the like are provided. The optical head device includes a plurality of light sources switchably usable; an objective lens for converging light emitted from one of the plurality of light sources to an information recording layer of an optical disc; and a light detector for receiving the light reflected by the information recording layer and outputting an electric signal based on the amount of the received light. The plurality of light sources include a first light source for emitting light having a first wavelength and a second light source for emitting light having a second wavelength shorter than the first wavelength.

Abstract: A light source unit comprises a plurality of light sources emitting a plurality of light beams. A plurality of volume hologram elements are provided for the plurality of light sources respectively, each volume hologram element having a plane of incidence of an incoming light beam and a plane of outgoing radiation of a diffracted light beam which are perpendicular to each other, the plurality of volume hologram elements having mutually different Bragg conditions in which an optical intensity of a diffracted light beam is set to a maximum.

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 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: A multilayer optical recording system to record information with light includes a lens unit, a recording medium, and a microscopic drive unit. The lens unit includes a metamaterial lens or a plasmon lens. The metamaterial lens has a first dielectric member in which first microstructures are implanted in a substantially regular manner. The plasmon lens has an aperture. The aperture is a hole or a slit created in a metal film. The microscopic drive unit is configured to adjust a relative position between the lens unit and the recording medium. In addition, the principal plane is placed to be in contact with the lens unit or to have a gap between the principal plane and the lens unit. Furthermore, the second microstructures are arranged periodically in a direction substantially perpendicular to the principal plane of the recording medium.

Abstract: An astigmatism element converges reflected light to generate focal lines, and a light separating element separates light fluxes of the reflected light entered into four first areas from each other. Two of the first areas are disposed in a direction along which a pair of vertically opposite angles defined by first and second straight lines are aligned, and the other two of the first areas are disposed in a direction along which the other pair of vertically opposite angles are aligned. Each of the four first areas is divided into two segment areas by a second area. The reflected light to be entered into the second area is guided to a position on the outside of sensors of a photodetector, and light fluxes of the reflected light to be entered into the paired segment areas are irradiated, on the photodetector, at positions away from each other.

Abstract: An optical pickup apparatus comprising: a laser diode; an objective lens made of synthetic resin arranged in an optical path of laser light between the laser diode and an optical disc so that the laser light from the laser diode is focused onto a signal recording layer through a protection layer of the optical disc; and an aberration correction element interposed in an optical path of the laser light between the laser diode and the objective lens, the aberration correction element configured to be operated so as to correct spherical aberration caused by moisture-absorption characteristics of the objective lens.

Abstract: According to one embodiment, an optical recording medium is provided in which interlayer crosstalk is low and in which stable and high-quality recording characteristics can be obtained. To this end, an optical recording medium comprises a first recording part which includes a first recording layer and a first light reflecting layer and which is disposed on a side closer to a light receiving surface, and a second recording part which includes a second recording layer and a second light reflecting layer and which is disposed on a side farther from the light receiving surface, the first recording part and the second recording part being stacked, wherein the thickness of the second light reflecting layer is larger than the thickness of the first light reflecting layer.

Abstract: An objective lens actuator comprises, two objective lenses, each for focusing lights upon an optical disc, an objective lens holder member for holding the objective lenses thereon, and lens protectors for preventing the objective lenses from being contacted on the optical disc, wherein the lens protectors include first and second lens protectors, which are provided on both end portions of the objective lens holder member in a tracking direction, and a third lens protector, which is provided in a middle of the two objective lenses, wherein the first and second lens protectors, which are provided on both end portions of the objective lens holder member in the tracking direction, are provided the objective lenses and end portion of the objective lens holder member in the tracking direction, and the third lens protector, which is provided between the objective lenses, has a height closer to that of the optical disc than the protectors, which are provided on both end portions of the objective lens holder member in

Abstract: A device includes: an objective lens that serves as a lens having a first numerical aperture when a first optical beam corresponding to a first optical disc converges on the first optical disc while serving as a lens having a second numerical aperture when a second optical beam corresponding to a second optical disc converges on the second optical disc; a section that generates a reflection optical signal from the first or second optical beam reflected by the first or second optical disc; and a section that determines whether an unknown disc is the first optical disc based on a degree of matching between the waveform of the reflection optical signal obtained when the first optical beam is emitted to the first optical disc, and the waveform of the reflection optical signal obtained when the first optical beam is emitted to the unknown disc.

Abstract: An optical pickup lens for focusing a light beam from a laser light source on an optical information recording medium is a single lens. The optical pickup lens has two surfaces, and a surface R2 opposite to a surface R1 closer to the laser light source has a continuous shape. When the surface R2 has radii h1, h2 and h3 (h1<h2<h3) from an optical axis to a lens periphery, and where sags in the radii h1, h2 and h3 are sag1, sag2 and sag3, and differentials in the sags are ?sag1, ?sag2 and ?sag3, respectively, 0>?sag1>?sag2 and ?sag2<?sag3 are satisfied.

Abstract: An optical pickup lens for focusing a light beam from a laser light source on an optical information recording medium is a single lens. The optical pickup lens has two surfaces, and a surface R2 opposite to a surface R1 closer to the laser light source has a continuous shape. When the surface R2 has radii h1, h2 and h3 (h1<h2<h3) from an optical axis to a lens periphery, and where sags in the radii h1, h2 and h3 are sag1, sag2 and sag3, and differentials in the sags are ?sag1, ?sag2 and ?sag3, respectively, 0>?sag1>?sag2 and ?sag2<?sag3 are satisfied.

Abstract: An optical pickup apparatus comprising: an objective lens configured to focus laser light having the Gaussian distribution properties emitted from a laser diode to a signal recording layer of an optical disc; and an adjustment coating formed on a surface of an incident face of the objective lens on which the laser light is to be made incident, the adjustment coating being configured to adjust transmittance of the laser light passing through the objective lens, the adjustment coating being formed on the surface of the incident face such that the transmittance is lowered as a numerical aperture of the objective lens is reduced.

Abstract: An optical unit including a lens unit including a lens and an optical element configured to receive a light beam focused by the lens, and a support member configured to support the lens unit. Cutouts are provided on joint surfaces of the lens unit and the support member, respectively, such that the cutouts on the joint surface of the lens unit match the cutouts on the joint surface of the support member. The cutouts are configured to accommodate a jig inserted thereinto and rotated to move the lens unit relative to the support member and adjust a position of the lens unit in a direction parallel to an optical axis of the lens.

Abstract: Disclosed is an objective lens used for an optical pickup apparatus to perform writing and/or reading of an optical information recording medium, comprising an antireflective film on a surface of a light source side, wherein a light flux of wavelengths including a wavelength ?1 of 380 nm??1?420 nm and a wavelength ?2 of 630 nm??2?810 nm, is condensed on the medium, a numerical aperture on the light source side with respect to the wavelength ?1 is within a range of 0.8-0.9, and that with respect to the wavelength ?2 is 0.7 or less, and a band of the antireflective film is within a range of 700 nm-800 nm in a state where a reflectance of a light flux perpendicularly entering a central portion of the surface in a wavelength region from 400 nm to 1200 nm is 3.0% or less.

Abstract: An optical pickup device, an optical drive using the same, and a method of forming a beam spot are provided. The optical pickup includes a light source system that includes a light source corresponding to at least one of a digital versatile disc (DVD) and a Blu-ray disc (BD). The light source forms a beam spot having an oval shape with a long axis and a short axis on an information recording track of the disc, and the light source is disposed such that the long axis is maintained at an angle ranging from 0° to 30° with respect to a radial direction passing through a rotation center of the disc.

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 disc drive according to the present invention can read and/or write data from/on an optical disc with information layers including first and second information layers (L0 and L1). The drive includes: an objective lens for converging a light beam; a lens actuator for driving the lens; a photodetector section that receives the beam reflected from the disc and converts it into an electrical signal; and a control section for determining the values of a first group of parameters, which are set to read data from the first layer (L0), and those of a second group of parameters, which are set to read data from the second layer (L1), during a disc loading process.

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: An optical head and an apparatus using the optical head are shown. The optical head includes a light-emitting element, a first polarized light diverging element for transmitting the light beam of a first polarization direction and reflecting the light beam of a second polarization direction orthogonal to the first polarization direction, a second polarized light diverging element for transmitting or reflecting the light beam of the first polarization direction, a converging element for converging the light beam on an information recording medium, a reflection element for reflecting a first reflected light beam reflected on the information recording medium and reflected on or transmitted through the second polarized light diverging element, and a detection element for detecting a second reflected light beam reflected on the reflection element and transmitted through or reflected on the second polarized light diverging element.

Abstract: A reproducing device includes a homodyne detection part that carries out homodyne detection by using reflected light of first light obtained from a recording layer as signal light and using reflected light of second light by a mirror as reference light, a signal reproducing part that obtains a reproduced signal based on the signal light, based on a result of homodyne detection, and a one-axis actuator that drives the mirror. The reproducing device further includes an optical path length servo control part that carries out driving control of the one-axis actuator in such a manner that the optical path length difference between the signal light and the reference light is kept constant, and an offset giving part that gives an offset that reduces or enlarges the amplitude difference of the reproduced signal of marks that are recorded in the recording layer and have sizes different from each other.

Abstract: An optical storage focus servo system may include an optical pickup unit that includes an astigmatic focusing lens, a focusing actuator that controls a position of the lens relative to an optical media, and a plurality of detectors that detect an intensity and shape of a reflected beam from the media. The system may also include a controller that controls the focusing actuator based on the intensity and shape of the reflected beam.

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 for selectively focusing each of light beams having three wavelengths ?1, ?2, and ?3 on a signal recording surface of a corresponding optical disc, the wavelengths ?1, ?2, and ?3 satisfying at least a relationship ?1<?2<?3, the objective lens including a diffraction section disposed on an entry-side surface thereof, the diffraction section including a first region disposed in an innermost radius portion, a second region disposed outside the first region, and a third region disposed outside the second region, the first to third regions being formed so that an aperture of the light beams are appropriately limited, the first region including a staircase-like diffractive structure having a certain number of levels configured so that diffracted light of a predetermined order has the highest diffraction efficiency and optical-path-difference phase amounts for the levels of the diffractive structure has a certain relationship.

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: A conventional optical pickup apparatus has a problem that due to multiple optical paths provided therein, the number of parts of optical systems becomes larger and a time required for attaching the parts and adjusting an optical axis becomes longer. In optical pickup apparatus 1 of the invention, a major part of optical path 21 of a laser beam emitted from first semiconductor laser device 2 and optical path 20 of a laser beam emitted from second semiconductor laser device 3 are shared. Then, the laser beam reflected from the optical disk 17 (optical feedback) is received by shared PDIC 19 and light-receiving processing is accurately performed on the laser beam as a light detector. With this structure, the number of parts of optical systems disposed in the optical pickup apparatus 1 is reduced, an attachment operation of the parts becomes easier, and a time required for adjusting an optical axis is reduced. Thus, an operational efficiency is greatly improved.

Abstract: A writing method according to the present invention is a method for writing a data sequence as a combination of marks and spaces on an information recording medium by condensing a laser beam through a lens. The writing method is characterized in that a cooling pulse for recording a mark that is even shorter than the limit of optical resolution of the laser beam and another cooling pulse for recording a mark that is still longer than the limit of the optical resolution of the laser beam are applied under mutually different conditions.

Abstract: An objective lens for an optical pickup device is provided with a light-source-side lens surface by which laser light is converged, and a disc-side lens surface by which the laser light converged by the light-source-side lens surface is converged. The first lens surface and the second lens surface are configured to guide a part of a light collecting portion of the laser light reflected on the second lens surface to a position on an outside of the first lens surface.

Abstract: An optical information recording and/or reproducing apparatus comprises: a focusing unit (11) which collects generated near-field light on an optical disc (1); a first detector (17) which receives light reflected by the optical disc (1) and outputs an electric signal according to the quantity of the received light; and a distance control circuit (22) which controls the distance between the focusing unit (11) and a light entrance surface of the optical disc (1), using the electric signal that is output from the first detector (17), and the optical disc (1) has at least N (N is an integer of 2 or greater) number of information layers, and a distance d0 from the light entrance surface to a first information layer which is most distant from the light entrance surface and a distance dn from the light entrance surface to an Nth information layer which is closest to the light entrance surface satisfy the relationship of dn?d0×(1/25).

Abstract: This optical disk device includes a pickup, an offsetting means, a focus servo means, a layer jump means, and a shift means. The pickup irradiates laser light upon an optical disk having a plurality of recording layers via a correction lens and an objective lens, and detects light reflected back from the optical disk. The offsetting means generates a focus error (FE) signal on the basis of the reflected light, and applies an offset voltage to the focus error signal. The focus servo means performs focusing servo on the basis of the FE signal. And, before layer jumping is executed by the layer jump means, the focus servo means displaces the correction lens to an intermediate position after having adjusted the offset voltage to a balance value. Then the layer jump means performs layer jumping.

Abstract: An optical pickup apparatus includes a light generating unit to generate a light to record or reproduce information, an objective lens to focus the light generated from the light generating unit onto a disk, and a multi-sectional polarizer disposed on a light path between the light generating unit and the objective lens and divided into a plurality of sectors having their individual optical axes.

Abstract: An objective lens includes: a solid immersion lens having a super-hemispherical or hemispherical shape, wherein a hyper-lens portion is formed in a part of an object-side surface of the solid immersion lens and integrated therewith by alternately stacking a first thin film having a positive dielectric constant and a second thin film having a negative dielectric constant along spherical shapes starting from a spherical shape having a radius Ri around a predetermined reference point Pr set outside the object-side surface of the solid immersion lens to a spherical surface having a radius Ro (Ro>Ri) around the reference point Pr.

Abstract: A spherical aberration correction mechanism includes an aberration correction lens, a movable portion for supporting the aberration correction lens, a fixing portion for supporting the aberration correction lens, in which the movable portion is disposed in a slidable manner, a shaft for supporting the movable portion in a rotatable manner about the axis and in a slidable manner in the axial direction, a feed screw having a helical groove, an engaging portion having an engaging groove like a male thread engaging with the helical groove from an direction, and a coil spring engaging with the outer surface of the shaft, for pressing the movable portion in the axial direction.

Abstract: Provided is an objective lens for which expressions 0.83<(pM/pL)<1.17 and 0.83<(pM/pT)<1.17 or expressions 0.80<(pM/pL)<1.20 and 0.86<(pM/pT)<1.14 are satisfied, where pL is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a difference in the thickness of a cover layer of an optical recording medium, pT is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a change in the temperature of an environment of the objective lens, and pM is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a change in incident magnification.

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: 0.40 < d · ( n - 1 ) f 2 < 0.70 ( 3 ) 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 pickup apparatus changes a propagation direction of luminous fluxes, out of a laser light reflected by a disc, in four luminous flux regions set about a laser optical axis so as to mutually disperse these luminous fluxes. A signal light region in which only a signal light is present appears on a detection surface of a photodetector. A plurality of sensors for a signal light are placed at positions irradiated with the signal light within the region. When an arithmetic process is performed on a detection signal outputted from each sensor, a DC component occurring in a tracking error signal is suppressed.

Abstract: An optical pickup lens for focusing a light beam from a laser light source on an optical information recording medium is a single lens. The optical pickup lens has two surfaces, and a surface R2 opposite to a surface R1 closer to the laser light source has a continuous shape. When the surface R2 has radii h1, h2 and h3 (h1<h2<h3) from an optical axis to a lens periphery, and where sags in the radii h1, h2 and h3 are sag1, sag2 and sag3, and differentials in the sags are ?sag1, ?sag2 and ?sag3, respectively, 0>?sag1>?sag2 and ?sag2<?sag3 are satisfied.

Abstract: A plastic objective lens is configured to collect a light beam with at least a wavelength ? on a recording layer of an optical disk and is used in an optical pickup for recording and/or reproducing an information signal by illuminating a light beam on the optical disk having one or a plurality of recording layers in an incident direction of the light beam.

Abstract: An objective-lens driving device includes a fixed block fixed to a moving base, a movable block having a lens holder configured to hold objective lenses, support springs configured to connect the fixed block and the movable block to each other, a focusing magnetic circuit including a first focusing coil, a second focusing coil, a first focusing magnet, and a second focusing magnet, and a tracking magnetic circuit. The first focusing coil is attached to the lens holder such that a first thrust-generating portion and a second thrust-generating portion are spaced from each other in a tangential direction. The second focusing coil is attached to the lens holder such that an axial direction of the second focusing coil coincides with the tangential direction. The first focusing magnet and the second focusing magnet are arranged in the tangential direction with the movable block disposed therebetween.

Abstract: An optical pickup is provided with a protector which prevents collision between an objective lens and an optical recording medium. The protector includes: a first sheet material which is arranged on an uppermost layer, has durability for abrasion against the collision with the optical recording medium that rotates in high speed, and is softer than a protecting member that protects a recording surface of the optical recording medium; a second sheet material which is provided in lower side than the first sheet material and has elasticity; and a plurality of adhesive sheets to perform adhesion between the sheet materials that form the protector, or adhesion between the lowermost sheet material among the sheet materials and a lens holder which holds the objective lens, or the objective lens.

Abstract: An optical pickup device has an astigmatism element which imparts astigmatism to reflected light of laser light reflected on a recording layer, and a spectral element into which the reflected light is entered, and which separates the reflected light. The spectral element is divided into four third areas by a first area having a certain width and formed along a straight line in parallel to a first direction, and by a second area having a certain width and formed along a straight line in parallel to a second direction. The spectral element is configured to guide the reflected light passing through the four third areas to respective corresponding sensors on a photodetector while making propagating directions of the reflected light different from each other, and to avoid guiding the reflected light entered into the first area and into the second area to the sensors.

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: A laminated half-wave plate includes: first and second wave plates having optical axes intersecting each other, wherein when phase differences of the first and second wave plates with respect to a wavelength ? are represented by ?1 and ?2, in-plane bearing angles formed by a polarization plane of a linearly-polarized beam incident on the laminated half-wave plate and the optical axes of the first and second wave plates are represented by ?1 and ?2, an angle formed by the polarization directions of the linearly-polarized beams incident on and emitted from the laminated half-wave plate is represented by ?, and an optical axis adjustment amount is represented by a, the following expressions are satisfied: ?1=180°+n×360°; ?2=180°+n×360° (where n in ?1 and ?2 is a non-negative integer); ?1=?/4+a; and ?2=3?/4?a.

Abstract: An optical head device (optical head) for a multi-layered optical recording medium has a focus control mechanism that makes use of astigmatism. The focus control mechanism has a sensor lens that includes a cylindrical lens. The focus control mechanism causes a light beam having passed through the sensor lens to have astigmatism, thereby being focused linearly in the Y direction on a front focal line located closer to the sensor lens and focused linearly in the X direction at a rear focal line located farther therefrom. The optical head also includes a photodetector which is disposed between the front focal line and the rear focal line to detect a focal position from the shape of a light beam. At the position of the front focal line, a shield plate with a window portion is disposed. The window portion has a size so as to allow the focal line to pass therethrough and shield stray light reflected from an unfocused recording layer.

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: A lens has a flange part at the outer periphery of its surface. A flange surface of the flange part is higher than the lens surface. The flange surface has a marking to identify a production jig, for example.

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.