Abstract: A spatial frequency filter device is for use with a laser beam. The device includes: a neutral region, which is configured to transmit or reflect the laser beam; and a deflecting region, which radially adjoins the neutral region and is configured to deflect beam components of the laser beam from a beam axis of the laser beam. The deflecting region has a constant portion, in which a deflecting effect on the beam components of the laser beam for each location in the constant portion is configured to be independent of a distance of a location from the neutral region. the deflecting region has a variation portion, in which the deflecting effect on the beam components of the laser beam is configured to vary, dependent on a distance from the neutral region.

Abstract: A data storage device is disclosed comprising a first actuator configured to actuate a first head over a first disk surface, and a second actuator configured to actuate a second head over a second disk surface. A seeking control signal is generated and used to control the first actuator to seek the first head over the first disk surface. The seeking control signal is filtered with a decoupler to generate a decoupler control signal, wherein the decoupler comprises a nominal decoupler and an adaptive decoupler. A tracking control signal is generated based on the decoupler control signal, and the tracking control signal is used to control the second actuator in order to access the second disk surface using the second head.

Abstract: An optical component for an optical pick-up for converging a laser beam having a particular wavelength onto a recording layer of an optical disc. The optical component comprises a base material formed of a resin composition, an undercoating which is formed of three layers of thin films having a same main constituent and is formed on a top surface of the base material, and a functional thin film formed on a top surface of the undercoating. In this configuration, each of a first layer and a third layer of the undercoating is a thin film formed without introducing oxygen, and a second layer is a thin film formed while introducing oxygen. A film thickness of the undercoating falls within a range of 160 nm to 270 nm, and film thicknesses of the thin films constituting the undercoating are substantially equal to each other.

Abstract: An objective lens for optical pickup and an optical pickup apparatus having the same are provided. The objective lens for optical pickup includes a light source side lens surface and a disc side lens surface. The light source side lens surface and the disc side lens surface each include an effective region disposed at a central region of the objective lens and a non-effective region disposed outside the effective region. An optical path changing element, disposed in the non-effective region of at least one of the light source side lens surface and the disc side lens surface, changes a path of light incident thereon.

Abstract: The present application discloses detection lens provided with lens portion and flange portion including first surface connected to lens portion and second surface opposite to first surface. Flange portion includes base along optical axis of lens portion, and first to fourth projections projecting from base. First and second projections are point-symmetric around optical axis. Third and fourth projections are point-symmetric around optical axis. Flange portion excludes projection extending beyond second surface. First projection includes first intersecting surface which intersects with first axis. Second projection includes second intersecting surface which intersects with first axis. Third projection includes third intersecting surface which intersects with second axis. Fourth projection includes fourth intersecting surface which intersects with second axis. First distance between first and second intersecting surfaces is longer than second distance between third and fourth intersecting surfaces.

Abstract: An optical element has at least one surface divided into a plurality of regions and includes: a first region configured to converge light with a wavelength ?1 onto a storage surface of a first optical disc and converge light with a wavelength ?2 onto a storage surface of a second optical disc; and a second region formed around the outer circumference of the first region and configured to converge light with the wavelength ?1 onto the storage surface of the first optical disc. The second region has a concave-convex structure concentrically formed on an aspheric surface and having a cross section being a saw teeth shape. The concave-convex structure is formed by a plurality of different saw teeth shapes, and the plurality of different saw teeth shapes respectively give different phase differences corresponding to substantially integer multiples of the wavelength ?1, for light with the wavelength ?1.

Abstract: The present application discloses detection lens provided with lens portion and flange portion including first surface connected to lens portion and second surface opposite to first surface. Flange portion includes base along optical axis of lens portion, and first to fourth projections projecting from base. First and second projections are point-symmetric around optical axis. Third and fourth projections are point-symmetric around optical axis. Flange portion excludes projection extending beyond second surface. First projection includes first intersecting surface which intersects with first axis. Second projection includes second intersecting surface which intersects with first axis. Third projection includes third intersecting surface which intersects with second axis. Fourth projection includes fourth intersecting surface which intersects with second axis. First distance between first and second intersecting surfaces is longer than second distance between third and fourth intersecting surfaces.

Abstract: Provided is an objective lens including a diffraction portion provided on a laser beam incident plane or output plane. The diffraction portion includes first second, and third diffraction regions, wherein first laser beams corresponding to a first optical disc having a first transmissive layer are condensed on a data recording portion of the first optical disc, second laser beams corresponding to a second optical disc having a second transmissive layer thicker than the first transmissive layer are condensed on a data recording portion of the second optical disc, and third laser beams corresponding to a third optical disc having a third transmissive layer thicker than the second transmissive layer are condensed on a data recording portion of the third optical disc. An evaluation parameter calculated on the basis of an in-plane efficiency distribution function has a value corresponding to a symbol error rate that is less than a predetermined value.

Abstract: An objective lens includes as a front lens disposed on the most objective side: a front lens configured to have a laminated structure wherein a first thin film of which the permittivity is negative, and a second thin film of which the permittivity is positive are mutually laminated, and also the films are formed so as to have a rectangular shape protruding on a side to which light from a light source is input, as a cross-sectional shape thereof.

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 pickup apparatus comprises: a first laser diode that generates a first laser beam having a first wavelength; a second laser diode that generates a second laser beam having a second wavelength longer than the wavelength; a third laser diode that generates a third laser beam having a third wavelength longer than the first wavelength and shorter than the second wavelength; an objective lens having an inner, outer, intermediate regions on an incident surface, the first laser beam being condensed on a signal recording layer of a first optical disc by condensing actions of the inner and outer regions, the second laser beam being condensed on a signal recording layer of a second optical disc by condensing actions of the inner and intermediate regions, the third laser beam being condensed on a signal recording layer of a third optical disc by condensing actions of the inner and intermediate regions.

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: An optical pickup device includes a photodetector which receives laser light reflected on a recording medium, and an optical system which guides laser light to the photodetector as convergent light. A light transmitting plate which imparts astigmatism to the laser light is disposed between the optical system and the photodetector with an inclination with respect to an optical axis of the laser light. The optical pickup device further includes an optical element which separates four light fluxes of the laser light from each other. The four light fluxes are obtained by dividing the laser light by two straight lines respectively in parallel to a first focal line direction of the laser light transmitted through the light transmitting plate, and a second focal line direction orthogonal to the first focal line direction.

Abstract: Provided are an optical pickup apparatus and an objective lens which can record and/or reproduce information for discs with different recording densities and can realize simplification of the structure of themselves and reducing cost. When the expression (1) is satisfied, step differences of a step structure can be further reduced than those in the case that d1=?1(n?1) holds, and fine grooves corresponding to a steps structure, formed on an optical-surface transfer surface of a mold for molding the objective lens become shallow, to be easily processed. In addition, the moldability is enhanced because the material of the objective lens easily enters the inner portion of the grooves. Further, a fluctuation of a diffraction efficiency caused when wavelength of a light flux changes or temperature changes is reduced so that information can be recorded and/or reduced stably.

Abstract: A disclosed optical pickup for performing at least recording, reproduction, or deletion of information on a first, second, third, and fourth optical recording media having different recording densities includes a first light source configured to emit first light having a first wavelength ?1 corresponding to the first and second optical recording media; a second light source configured to emit second light having a second wavelength ?2 corresponding to the third optical recording medium; a third light source configured to emit third light having a third wavelength ?3 corresponding to the fourth optical recording medium; an objective lens configured to focus the first light, the second light, and the third light on corresponding recording surfaces of the first, second, third, and fourth optical recording media; and an aberration correcting unit between the objective lens and the first, second, and third light sources.

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 pickup includes: a first emission unit emitting an optical beam with a first wavelength corresponding to a first optical disc; a second emission unit emitting an optical beam with a second wavelength, which is longer than the first wavelength, corresponding to a second optical disc different from the first optical disc; a third emission unit emitting an optical beam with a third wavelength, which is longer than the second wavelength, corresponding to a third optical disc different from the first and second optical discs; a condensing optical device condensing, on a signal recording surface of a corresponding optical disc, the optical beams emitted from the first to third emission units; and a diffraction unit provided in the condensing optical device, which is disposed on the optical path of the optical beams with the first to third wavelengths.

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 near-field detection optical component operating in transmission. It includes at least one portion (11b) forming at least one grating (11) of diffraction microstructures (11a) succeeding one another over several periods (p), this grating (11) being capable of converting evanescent waves (16), which are established between the component and an object (12) located in the near field, when it reflects or emits radiation having a wavelength, into propagating waves (16?) by a diffraction effect during transmission through the portion (11b) forming the grating (11) of diffraction microstructures (11a). The period (p) of the grating (11) being of the order of magnitude of the wavelength of the radiation.

Abstract: An objective lens for an optical pick-up which is used to record data to and/or to reproduce data from at least three types of optical discs by selectively using one of at least three light beams having different wavelengths is provided. When thicknesses of a first, second and optical discs are represented by t1, t2 and t3, respectively, a relationship t1?t2<t3 is satisfied. When numerical apertures required for the first, second and third optical discs are represented by NA1, NA2 and NA3, respectively, a relationship NA1?NA2>NA3 is satisfied. The first, second and third light beams are incident on the objective lens as substantially collimated light beams, respectively. In this configuration, at least one of surfaces of the objective lens includes a first area for attaining the numerical aperture required for recording data to and/or reproducing data from the third optical disc, and a second area located outside the first area.

Abstract: An objective lens used for an optical pickup device wherein the optical pickup device includes: light source; and a converging optical system including the objective lens for converging a light beam emitted from the light source to an information recording surface of an optical information recording medium, and the optical pickup device is capable of recording and/or reproducing information by converging the light beam emitted from the light source to the information recording surface of the optical information recording medium with the converging optical system, the objective lens being a plastic single lens and satisfying following formulas when NA is an image-side numerical aperture required for recording and/or reproducing information to the optical information recording medium and f (mm) is a focal length of the objective lens.

Abstract: An objective lens for use in an optical pickup apparatus for recording and/or reproducing information on a first optical information recording medium having a protective substrate with a thickness t1 using a light flux with a wavelength ?1, on a second optical information recording medium having a protective substrate with a thickness t2 using a light flux with a wave length ?2 and a third optical information recording medium having a protective substrate with a thickness t3 using a light flux with a wavelength ?2, the objective lens includes: an optical surface including a central area and a peripheral area, wherein when the objective optical lens forms the portion of the light flux with the wavelength ?2 passed the central area into a converged spot through a substrate with a thickness t4, the objective optical lens makes a spherical aberration of the converged spot a minimum value.

Abstract: The present invention provides an optical pickup apparatus including a first light source, a second light source, a third light source, and a light-converging optical system including an objective lens. The objective lens includes at least one optical surface with a diffractive structure. The diffractive structure includes a plurality of ring shaped zones. Each of the ring shaped zones is concentrically arranged around an optical axis and includes a step difference extending along the optical axis. In the objective lens, the predetermined conditions according to the offence against a sine condition, an average of step differences of the plurality of ring shaped zones, a focal length, and a magnification, are satisfied.

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: There is provided an optical pickup apparatus which includes a light source that generates light irradiating an optical recording medium; and an objective lens that collects the light irradiated from the light source on a recording surface of the recording medium, which further includes a coupling lens arranged on an optical path between the light source and the objective lens. In the optical pickup apparatus, a surface shape of the coupling lens is formed so that a preset spherical aberration amount is generated in the light irradiated from the light source at a position settled corresponding to a shift amount of the objective lens and where the light irradiated from the light source passes through the coupling lens, when the objective lens shifts.

Abstract: A multi-focal objective lens for use in an optical pickup apparatus for recording and/or reproducing information using a first light flux with a wavelength ?1 on a first and second optical discs, includes a first optical surface including a first diffractive structure. The multi-focal objective lens converges a diffracted light flux with one of the m-th diffraction order and the n-th diffraction order on an information recording surface of the first optical disc for recording and/or reproducing information of the first optical disc, and converges a diffracted light flux with another of the m-th diffraction order and the n-th diffraction order on an information recording surface of the second optical disc for recording and/or reproducing information of the second optical disc.

Abstract: An optical pickup has a photo detector which is divided into first, second, third and fourth quadrants, receives a laser beam reflected from an optical disc via an objective lens, and outputs first, second, third and fourth detection signals from the respective quadrants. A system controller controls a memory to store levels (A, B, C and D) of the first, second, third and fourth detection signals after a focus servo section performs a focus operation by shifting the objective lens in a direction perpendicular to the optical disc surface, and then, calculates a ratio of ((A+D)/(B+C)) in a radial direction of the optical disc. The system controller controls the tracking servo section to perform a tracking operation to shift the objective lens in the radial direction based on a correction table which represents a relationship between correction amount of the lens shift and the calculated ratio ((A+D)/(B+C)).

Abstract: An objective lens optical system includes a light beam splitting element and an objective lens and is configured to focus a light beam with a wavelength ? on an information recording surface of a first optical recording medium as a dual/double layer disc having a transparent substrate with a thickness t1 and to focus a light beam with a wavelength ? on an information recording surface of a second optical recording medium as a dual/double layer disc having a transparent substrate with a thickness t2 (t1<t2). The light beam splitting element is sectioned into regions that are designed to focus a light beams on an information recording surface of either one of the first optical recording medium and the second optical recording medium. Either one region has a negative or positive power so that a light focus position of a light beam having passed through the first region by the objective lens and a light focus position of a light beam having passed through the second region by the objective lens are different.

Abstract: An objective lens unit for use in an optical pickup apparatus, includes a first optical element arranged opposite to the optical information recording medium; a second optical element arranged at a light source side of the first optical element opposite to the first optical element and including a ring-shaped structure in which plural ring-shaped zones are formed on at least one optical surface of the second optical element such that neighboring ring-shaped zones cause a predetermined optical path difference for incident rays; and each of the first and second optical elements having a optical functional section and a flange section formed around the optical functional section, wherein the flange section of the first optical element and the flange section of the second optical element are formed so as to fix the first and second optical elements at predetermined respective relative positions.

Abstract: An objective lens for an optical information recording/reproducing device (executing information reading or writing on first through third optical discs having different data densities and different protective layer thicknesses t1-t3 (t1?t2?t3)) by selectively using first through third substantially collimated light beams having first through third wavelengths ?1-?3 (?1<?2<?3) respectively) includes a first optical member and a second optical member which are cemented together at a cementing surface. At least an area of the cementing surface within an incidence height necessary for securing a numerical aperture NA3 (required for the information read/write on the third optical disc) is provided with a diffracting structure including annular zones. The diffracting structure is formed so that diffraction orders m(?1), m(?2) and m(?3) of the first through third light beams maximizing their diffraction efficiency satisfy m(?1)>m(?2)?m(?3)?1.

Abstract: A diffraction element for diffracting a particular wavelength of incident optical beam includes: a base section made from a first resin and provided with a predetermined diffraction pattern; and a cover section made from a second resin and covering the diffraction pattern, wherein a rate of change of refraction index of the first resin is substantially the same as a rate of change of refraction index of the second resin in a temperature range between a first temperature and a second temperature.

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: The present invention provides an optical pickup apparatus including a first light source, a second light source, a third light source, and a light-converging optical system including an objective lens. The objective lens includes at least one optical surface with a diffractive structure. The diffractive structure includes a plurality of ring shaped zones. Each of the ring shaped zones is concentrically arranged around an optical axis and includes a step difference extending along the optical axis. In the objective lens, the predetermined conditions according to an average of step differences of the plurality of ring shaped zones, a focal length, a magnification, and the Abbe number, are satisfied.

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: The present invention provides an optical pickup apparatus including a first light source, a second light source, a third light source, and a light-converging optical system including an objective lens. The objective lens includes at least one optical surface with a diffractive structure. The diffractive structure includes a plurality of ring shaped zones. Each of the ring shaped zones is concentrically arranged around an optical axis and includes a step difference extending along the optical axis. In the objective lens, the predetermined conditions according to the offence against a sine condition, an average of step differences of the plurality of ring shaped zones, a focal length, and a magnification, are satisfied.

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 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 optical pickup apparatus provides a wavelength dependency of a spherical aberration so as to correct a change in a spherical aberration due to a refractive index change with a temperature change of the objective optical element.

Abstract: The present invention provides an optical pickup apparatus including a first light source, a second light source, a third light source, and a light-converging optical system including an objective lens. The diffractive structure includes a plurality of ring shaped zones. Each of the ring shaped zones is concentrically arranged around an optical axis and includes a step difference extending along the optical axis. In the objective lens, the predetermined conditions according to the offence against a sine condition, an average of step differences of the plurality of ring shaped zones, a focal length, and a magnification, are satisfied.

Abstract: The present invention provides an optical pickup apparatus for recording and/or reproducing information for different kinds of optical information recording media. The optical pickup apparatus 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; a light-converging optical system including an objective lens. The objective lens includes at least one optical surface including a diffractive structure which includes a plurality of ring shaped zones. Each of the ring shaped zones is concentrically arranged around an optical axis and includes a step difference extending along the optical axis. In the objective lens of the optical pickup apparatus, the offence against a sine condition, an average of step differences of the plurality of ring shaped zones, focal length, and magnification satisfy the predetermined conditions.

Abstract: An objective lens and an optical pickup device utilizing it are disclosed wherein the objective lens includes a specified aspheric surface profile having a discontinuity and a single specified diffraction optical surface so to provide a focusing effect which is usable with different optical recording media, such as a CD versus a DVD. By providing a single diffraction surface and an aspheric surface having a discontinuity, more freedom of design is achieved for the diffraction surface than would otherwise be possible. The objective lens according to the invention is designed so as to be both compact and inexpensive and enables recording/playback onto either type optical recording media using different wavelengths and different numerical apertures, depending on the recording medium used.

Abstract: A lens for an optical recording and reproducing system includes: a plane of incidence on which a light generated from a light source is made incident; a first reflection side for reflecting a light passing through a plane of incidence; and a second reflection side for reflecting again the light that has been reflected on the first reflection side, the second reflection side being formed to be an ellipsoid side, and the first reflection side and the second reflection side being coated with a reflection material. A very small optical system in its size and weight is possibly constructed, so that information recording and reproducing can be possible only with one focussing lens without a necessity of an objective lens. Accordingly, an ultra-thin optical recording and reproducing system of which height is remarkably reduced can be provided.

Abstract: An optical pickup having a light-emitting element, an objective lens unit, a reflecting mirror and a light-receiving element, emits a beam onto an optical recording medium and uses a reflected beam to read recorded information. In the objective lens unit, a central part of a surface, facing the light-emitting element, of an objective lens disposed so that an optical axis is substantially aligned with a chief ray of the beam emitted by the light-emitting element, is a transmissive diffraction grating, and a central part of a surface of the objective lens that will face the optical recording medium is a convex mirror which bulges toward the light-emitting element. The reflecting mirror, which is annular and encompasses the optical axis of the objective lens, reflects toward the objective lens the beam from the light-emitting element that has passed through the transmissive diffraction grating and been reflected by the convex mirror.

Abstract: An information recording medium 101 includes: a transparent substrate 109 having a first surface A and a second surface B opposite to the first surface A; reflectance reduction means 110 provided on the first surface A of the transparent substrate 109; and an information recording layer 120 provided on the second surface B of the transparent substrate 109.

Abstract: The invention discloses a flat-plate lens to be built in an optical recording medium for improving the image-forming characteristics of the recording medium. The flat-plate lens of the invention comprises a layered thin film having a periodical structure in the direction of thickness thereof corresponding to a wavelength slightly longer than the wavelength of the light used for recording and retrieving information into and from the recording medium. The thin film of a periodical structure is formed by alternate lamination of pluralities of layers two materials having different refractive indices such as a combination of MgF2 and ZnS. When the thin film having such a periodical structure is formed with good uniformity allover the surface, the image-forming performance on the recording layer can be uniform irrespective of the position on the flat-plate lens.

Abstract: An objective lens for use in an optical pickup apparatus has two positive lenses of a first lens arranged at a light source side and a second lens arranged at an information recording medium side and the objective lens comprises a first surface being a light source side optical surface of the first lens and a third surface being a light source side optical surface of the second lens, and at least two optical surfaces including the first surface and the third surface are made to be an aspherical surface respectively, and the objective lens satisfies the following formulas: NA?0.8 1.2 mm>f>0.3 mm ?0.06>?SAG>?0.24 ?SAG=(X1??X3?)/(NA4·f·(1+|m|)) X1?=X1·(N1?3)3/f1 X3?=X3·(N2?1)3/f2.

Abstract: An optical head (1) for scanning optical record carriers (2) is provided with a compensator (16) for compensating spherical aberration of the objective system (18) or defocus of the collimator lens (14) caused by operation of the optical head at a temperature different from the design temperature. A surface of the compensator (16) comprises a phase structure in the form of annular areas (52, 53, 54), the areas forming a non-periodic pattern of optical paths of different length. The optical paths change as a function of temperature and form a temperature-dependent wavefront deviation that compensates the spherical aberration and/or defocus.

Abstract: An optical head has objective lenses that converge a light beam, a light-emitting surface that faces an optical recording medium with an air layer therebetween and from which the light beam converged by the objective lenses exits towards the optical recording medium, and a light reflection preventing film that is provided at the light-emitting surface. A recess is formed in the light-emitting surface, and the light reflection preventing film is provided inside the recess.

Abstract: An optical element (16) introduces a first wavefront deviation when a first radiation beam having a first wavelength passes through it and a second wavefront deviation when a second radiation beam having a second wavelength different from the first wavelength passes through it. One surface of the optical element comprises a phase structure in the form of annular areas (52, 53, 54, 55), the areas forming a non-periodic pattern of optical paths of different length. The optical paths for the first wavelength form the first wavefront deviation and the optical paths for the second wavelength form the second wavefront deviation, the difference between the two deviations being proportional to the difference between the first and second wavelength.

Abstract: Disclosed is a lens for light collection for total reflection for a front monitor photodiode (PD) in an optical pick-up device. The optical pick-up device includes a light source provided with a holographic unit adapted to diffract a light beam, an optical disc arranged in front of the light source and adapted to allow data to be written thereof or to be read therefrom, a monitor photodiode arranged in front of the light source in a diagonal direction with respect to the light source, the monitor photodiode serving to monitor a laser power of the light source, and a lens for light collection arranged between the light source and the monitor photodiode and adapted to converge a first-order diffracted beam outputted from the holographic unit and to apply the converged first-order diffracted beam to the monitor photodiode.

Abstract: An optical lens whose focal length is different on first and second planes perpendicular to each other is provided. The optical lens is configured such that a convex element, which is formed integrally with a substrate having a flat face, has a convex curved face that functions as an optical lens and is shape such that the curvature on a first cross section and the curvature on a second cross section perpendicular to and intersecting with the first cross section are different from each other, whereby the focal lengths on the first and second cross sections are different from each other. A groove of a substantially elliptical shape or a substantially rectangular shape is formed along the boundary between the substrate and the convex element. The optical lens is used to produce a focus error signal or is incorporated into an optical pickup apparatus.