Abstract: A semiconductor laser device includes: a semiconductor laser chip which is composed of a semiconductor substrate and a plurality of semiconductor layers stacked on an element formation face of the semiconductor substrate and which outputs an irradiation light for irradiating an optical disk; and a light receiving element which receives the irradiation light reflected by the optical disk as a feedback light. The semiconductor laser chip includes on one face thereof an electrode facing an optical element and is fixed in a package so that at least one of sub-beams reflected by the optical disk is incident on the one face. A chip exposing portion for exposing a region of the one face where the sub-beam is incident is formed in the electrode.

Abstract: An object of the present invention is to reduce the influence of a stray light incident on a light receiving device by reflection of an unnecessary diffraction light not contributing to write or read on a disc surface at write or read of an optical disc having a large surface reflectivity with respect to an information recording surface. A position in which a diffraction light with an n-order in an advancing path and the n-order in a returning path, reflected on the information recording surface of a first information recording medium, is focused by a condensing lens is different from a position in which a diffraction light different from the n-order diffraction light in at least one of the advancing path and the returning path, reflected on a surface of the first information recording medium, is focused by the condensing lens.

Abstract: A diffractive optical element (DOE) corrector for use with three different wavelengths includes a first diffractive element on a first surface of a first material, the first diffractive element diffracting a first wavelength of the three wavelengths, while directing a majority of light of second and third wavelengths of the three wavelengths into a zero-th order, and a second diffractive element on a second surface of a second material, the second material being different from the first material, the second surface being different from and in an optical path of the first surface, the second diffractive element diffracting the second wavelength, while directing a majority of light of the first and third wavelengths into a zero-th order.

Abstract: An optical pickup device is constituted to enable stable recording or reproduction on/from a recording medium.

Abstract: To reduce the optical path length of the entire optical system in a reproduction or recording optical system of an optical recording medium, and promote miniaturization and reductions in costs of apparatuses. An optical head apparatus has an optical system an including a light source and a translucent optical element and irradiates light exiting from the light source, after having been transmitted through the optical element, onto the optical recoding medium. The optical element has a surface or surfaces having negative power on the light-source side and a surface or surfaces having positive power on the optical-recording-medium side. In order to increase the power of the surface or surfaces, one or more of these surfaces are formed as a hologram surface on which a concentric hologram pattern is formed.

Abstract: An optical pickup includes a first optical source producing a first optical beam having a wavelength ?1, a second optical source producing a second optical beam having a wavelength ?2 (?1<?2), and a single objective lens focusing any of the first and second optical beams to an optical recording medium, the first optical beam is incident to the objective lens as a parallel beam and the second optical beam is incident to the objective lens as a divergent optical, wherein an aperture is provided at a front side of the objective lens with offset from a principal point at the front side by a distance t given by an equation t=L?NA1·f/tan(a sin(NA2obj)), wherein f represents a focal distance of the objective lens, NA1 represents the numerical aperture at the side of the image surface when the first optical source is turned on, NA2obj represents the numerical aperture at the front side when the second optical source is turned on, and L represents the object distance at the time when the second optical source is

Abstract: An objective optical system 10 includes a diffraction plane 15 for separating a laser light beam into at least 0th-order diffracted light and 1st-order diffracted light. The objective optical system 10 is configured to focus the 0th-order diffracted light onto an information recording surface 22a of a first information recording medium 20a and the 1st-order diffracted light onto an information recording surface 22b of a second information recording medium 20b and meet the following conditional expression (1): ?0>?1 ??(1) wherein ?0 is the diffraction efficiency of the 0th-order diffracted light and ?1 is the diffraction efficiency of the 1st-order diffracted light.

Abstract: An optical pickup device includes a beam shaping mirror. The mirror has a first optical surface on which a wavelength selection film is formed and a second optical surface on which a diffraction grating is formed. The wavelength selection film transmits a first laser beam and reflects a second laser beam. Light intensity distribution of the first laser beam is converted from an elliptic shape to a circular shape by reflecting the first laser beam transmitted by the wavelength selection film and input to the beam shaping mirror by the diffraction grating, then transmitting it by the wavelength selection film and outputting it from the beam shaping mirror. The diffraction grating diffracts the first laser beam in order that directions of the first and second laser beams which are output from the beam shaping mirror become the same.

Abstract: An optical pickup device in which light via a beam shaping mirror is input to an objective lens and the light is directed to an optical disc, includes a collimator lens which changes the light input to the beam shaping mirror into infinite system light and the beam shaping mirror includes a diffraction grating which changes the infinite system light into finite system light.

Abstract: The present invention provides an optical element for use in an optical pickup apparatus which records and/or reproduces information, and for converging a laser light flux with a wavelength ?1 on an information recording medium. The optical element includes; a main body; and an antireflection film arranged on at least one surface of the main body and including an optical functional surface. In the optical element, a maximum angle ?1 formed by a normal of the optical functional surface and the laser light flux satisfies 40°??1?70°, and a phase difference between a phase of a P-polarized light and a phase of a S-polarized light of the laser light flux when the laser light flux enters into the optical element, is the substantially same to the phase difference when the laser light flux is emitted from the optical element.

Abstract: The optical miniaturized module includes a semiconductor laser for irradiating an optical disk with laser light, a diffraction grating for forming a main beam and two sub beams from the laser light, a polarization hologram for dividing reflected light from the optical disk, and a photodetector for detecting the reflected light. The polarization hologram includes a first parting line defined in a direction optically corresponding to a radial direction as the optical disk rotates. A main beam M incident area is divided with a boundary defined by the first parting line. A sub beam A incident area and a sub beam B incident area are each arranged avoiding the first parting line.

Abstract: An optical pickup apparatus for reproducing information from an optical information recording medium or for recording information onto an optical information recording medium, is provided with a first light source for emitting first light flux having a first wavelength; a second light source for emitting second light flux having a second wavelength, the first wavelength being different from the second wavelength; a converging optical system having an optical axis and a diffractive portion, and a photo detector; wherein in case that the first light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the first light flux is greater than that of any other ordered diffracted ray of the first light flux, and in case that the second light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the second light flux is greater than that of any other ordered diffracted

Abstract: An optical system including a light source that generates light, a mirror changing an optical path of the light generated by the light source and an aberration correcting element that corrects aberrations generated in the light reflected from the mirror due to an error in the surface shape of the mirror.

Abstract: An optical pickup device compatible with two types of optical recording media in accordance with the present invention includes: a first light source emitting a first laser beam with a first wavelength; a second light source emitting a second laser beam with a second wavelength greater than the first wavelength; an objective lens with parameters according with the first wavelength and adapted to focus the first and second laser beams on the at least two types of optical recording media; a collimating lens for collimating an incident beam of light and transmitting the collimated light beam to the objective lens; an optical path synthesizer/separator for receiving the first and second laser beams and transmitting the first and second laser beams to the collimating lens; and a compensator for correcting the second laser beams and transmitting the corrected second laser beams to the optical path synthesizer/separator.

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: A diffraction element is interposed between a semiconductor laser and collimator lens. Other diffracted light than zero-order light output from the diffraction element will not be focused on an optical recording medium and the amount of light condensed to the focus of the zero-order light is thus smaller. The diffraction element is variable in diffraction efficiency. When the diffraction efficiency of the diffraction element is raised, an optical pickup device will utilize the light with a lower efficiency. With the diffraction efficiency being lowered, the optical pickup device will utilize the light with a higher efficiency. Thus, the optical pickup device can utilize the light with a variable efficiency without having to being designed larger.

Abstract: A laser beam emitted from a light source is divided into a main beam and two sub-beams by a diffraction grating. A filter is arranged between a collimator lens and an objective lens. A filter unit is arranged in a predetermined pattern in the filter. The filter unit gives a maximum transmittance or a maximum reflectance at an incident angle at which the laser beam is incident in a parallel light state. The filter unit is formed in a pattern in which at least the laser beam reflected from a layer except a recording layer of an irradiation target is prevented from entering a sub-beam sensor pattern.

Abstract: An integrated unit in which a light source and a light emitting diode are combined into one component is fixed to an optical bench. Then, relative position adjustment of an objective lens actuator is carried out with respect to the optical bench so that a desired detection signal can be obtained through reflected light from a disk information recording medium and then the objective lens actuator is fixed. The relative position adjustment of the integrated unit is no longer required and it is no longer necessary preliminarily to provide a margin for adjusting the integrated unit. Thus, an optical head can be reduced in size and thickness.

Abstract: An optical pickup includes a first optical source producing a first optical beam having a wavelength ?1, a second optical source producing a second optical beam having a wavelength ?2 (?1<?2), and a single objective lens focusing any of the first and second optical beams to an optical recording medium, the first optical beam is incident to the objective lens as a parallel beam and the second optical beam is incident to the objective lens as a divergent optical, wherein an aperture is provided at a front side of the objective lens with offset from a principal point at the front side by a distance t given by an equation t=L?NA1·f/tan(asin(NA2obj)), wherein f represents a focal distance of the objective lens, NA1 represents the numerical aperture at the side of the image surface when the first optical source is turned on, NA2obj represents the numerical aperture at the front side when the second optical source is turned on, and L represents the object distance at the time when the second optical source is t

Abstract: A Bragg-grating-based liquid crystal element is disposed on an optical axis of a first objective lens with a tilt angle of more than 45° with respect to the optical axis of the first objective lens. By inputting a laser beam to the Bragg-grating-based liquid crystal element in such a manner that a reflection direction of the light beam by the Bragg-grating-based liquid crystal element is in parallel with a short axis of a shape of the laser beam, the reflected laser beam has a shape whose dimension is elongated in the short axis direction.

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: In an optical pickup apparatus of the present invention, either a first laser diode emits a laser beam having a first wavelength or a second laser diode emits a laser beam having a second wavelength. An optical system focuses one of the two laser beams onto a recording surface of an optical recording medium. A photodetector unit receives reflection beams, which are reflected from the recording medium, to generate detection signals from the received reflection beams. A holographic unit has a first hologram suited to the first laser diode and a second hologram suited to the second laser diode, the first hologram provided to diffract a reflection beam of the laser beam of the first laser diode to the photodetector unit, and the second hologram provided to diffract a reflection beam of the laser beam of the second laser diode to the photodetector unit.

Abstract: On an optical path between a light source and an objective lens, there is provided an optical path changing section for changing a predetermined optical path of undesired light passing through, from the predetermined optical path to another optical path. The optical path changing section includes a plate having an aperture portion for allowing a laser beam emitted from the light source to pass through, and an aperture wall which defines the aperture portion of the plate includes a taper portion which is formed in a tapered-shape and slants so as to come close to an optical axis L1 of the light source in association with movement toward a laser beam outgoing direction. The undesired light from the light source is reflected by the taper portion to change the predetermined optical path of the undesired light passing through, from the predetermined optical path to another optical path.

Abstract: An optical recording media objective lens is disclosed for converging either of two working lights of a first wavelength or a second wavelength. The working light of the first wavelength is converged at a first numerical aperture onto the first optical recording medium and the working light of the second wavelength is converged at a second numerical aperture onto the second optical recording medium. An aperture adjusting zonal part is included on at least one of the objective lens surfaces for apparently eliminating light at the periphery of a light flux having a wavelength ?1 while maintaining light at the periphery of a light flux having a wavelength ?2, where ?1 is one of the first and second wavelengths and ?2 is the other wavelength. The aperture adjusting zonal part is formed so as to satisfy two conditions.

Abstract: An optical pickup is configured to emit a light beam to an optical disk having a plurality of recording layers and is configured to receive a reflection light beam obtained when the emitted light beam is reflected at a recording layer of the optical disk. The optical pickup includes an objective lens configured to focus the light beam emitted from a light source at a focused recording layer of the optical disk and receive the reflection light beam; a focusing lens configured to focus the reflection light beam received by the objective lens; and a stray-light removing element including the boundary surface and being configured to remove stray light from the reflection light beam by reflecting only the stray light included in the reflection light beam reflected at an unfocused recording layer at the boundary surface.

Abstract: An optical pickup apparatus comprising: a first light source emitting first light flux having wavelength ?1 (380 nm??1?450 nm); a second light source emitting second light flux having wavelength ?2 (600 nm??2?700 nm); a third light source emitting third light flux having wavelength ?3 (750 nm??3?800 nm); a first divergent angle-converting element through which the first light flux passes; a second divergent angle-converting element through which the second light flux and the third light flux pass; and an objective optical element through which the first, second, and third light fluxes pass. Optical magnification m2 of the second divergent angle-converting element for the second light flux and optical magnification m3 of the second divergent angle-converting element for the third light flux are different from each other.

Abstract: When recording/reproducing an optical disc having a recording layer of multi-layer structure, an unwanted optical beam reflected from a recording layer other than a target layer for recording/reproduction is incident on a photodetector to cause an unwanted disturbance component to leak to a detection signal, giving rise to a degradation in the quality of a tracking control signal. In an optical pickup apparatus, for suppression of the degradation, an optical element is mounted having a diffraction area for diffracting part of the optical beam and light receiving planes for sub-optical beams are provided each of which has a light shielding zone or dead zone of a predetermined width on its central sectioning line.

Abstract: An optical disk apparatus includes an optical pickup and a disk-rotation driving unit configured to rotationally drive the optical disks. The optical pickup includes a first emission unit configured to emit a first wavelength beam; a second emission unit configured to emit a second wavelength beam; a third emission unit configured to emit a third wavelength beam; an objective lens configured to focus the first to third wavelength beams emitted from the first to third emission units, respectively, at a signal recording surface of an optical disk; a light-path combining unit configured to combine an optical path of the first wavelength beam emitted from the first emission unit and an optical path of the second and third wavelength beams emitted from the second and third emission units, respectively; and an aberration correcting unit provided on the optical path of the second and third wavelength beams.

Abstract: The present invention relates to an optical pickup and a disc drive for preventing aberrations of laser light due to variations in temperature and humidity to ensure satisfactory characteristics of the laser light. A compound lens (14) is disposed in the optical path of the laser light, which is emitted by a light-emitting device (11) to be incident on a beam splitter (15), and in the optical path of the laser light, which exits from the beam splitter to be incident on a photodetector (13). The compound lens includes a diffractive section (23) for diffracting the laser light and a lens section (24) having a predetermined function for the laser light. The compound lens is formed by integrating individual sections including the diffractive section and the lens section. The compound lens is provided with a passage hole (14c) that lets in the laser light emitted by the light-emitting device to be incident on the beam splitter.

Abstract: The present invention provides an optical pickup apparatus including: a first light source; a second light source; and a light-converging optical system including a coupling lens and an objective lens. The coupling lens includes a first diffractive structure. The optical pickup apparatus satisfies a predetermined condition according to the chromatic aberration, focal length, and dispersion of the material.

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-information recording medium includes a substrate that includes a servo surface; an information recording layer laminated on the servo surface of the substrate capable of recording information as a hologram produced by interference between an information beam containing the information and a reference beam; a tracking servo area that is formed in a track direction on the servo surface, and that records therein tracking information for tracking servo control; and a following up servo area that is formed in the track direction on the servo surface, and that is to be irradiated by a beam emitted from an optical-information recording apparatus for recording the information in the information recording layer so as to make the beam follow a rotation of the optical-information recording medium.

Abstract: An objective lens for use in an optical pickup apparatus, comprises an objective lens satisfying the following expression: 0.01?|?SA3obj/??|<0.1 (?rms/nm), where ?SA3obj/?? represents the wavelength dependency of the 3rd order spherical aberration of the objective lens when the oscillation wavelength is fluctuated between ±2 nm.

Abstract: An optical pickup apparatus for recording and/or reproducing information for an optical information recording medium, comprising a light converging optical system including a coupling lens and an objective lens, wherein a first diffraction structure is installed on the objective lens, and a second diffraction structure is arranged on the coupling lens, whereby the spherical aberration and chromatic aberration caused by the difference in the thickness of the protective layer are corrected in the light converging optical system as a whole.

Abstract: An optical pickup includes: a frame, having a first face formed with a groove, a second face opposite to the first face, a first hole in which a diffraction grating is disposed, and a second hole communicated with the groove and the second face; a spring plate, attached to the first face; and a spring member, including a ring portion disposed in the first hole and abutting on the diffraction grating, a first arm portion extended from an outer peripheral edge of the ring portion and inserted in the groove, and a second arm portion connected to the first arm portion and inserted in the second hole.

Abstract: Disclosed are a module to detect a tracking error signal that is easy to be assembled and robust against variation in a track angle, a diffraction grating, an optical pickup, and an optical disc apparatus that enable the module to be realized, wherein a diffraction grating divided into at least three areas, first, second, and third areas, is used; the second area is an area that do not diffract light; and focusing positions of light diffracted by the first and third areas sandwiching the second area therebetween on an optical disc are arranged with a spacing of (2n?1)×t/2 in an optical disc radial direction, respectively, where n is a nonnegative integer and t is a spacing of guide grooves of the optical disc.

Abstract: An optical pickup includes: a first projector for projecting a first light beam of a first wavelength so as to record and reproduce information with respect to an optical disk having a first light transmissive layer; a second projector for projecting a second light beam of a second wavelength longer than the first wavelength so as to record and reproduce information with respect to an optical disk having a second light transmissive layer; an objective lens common to the first and second light beams; and a diffraction optical element made of a lens with a diffraction grating and a refracting face and disposed in an optical path between the first and second projectors and the objective lens. The diffraction optical element is set to satisfy a predetermined equation.

Abstract: An optical pickup device is equipped with a diffraction element that includes a transparent substrate. At least one surface of the transparent substrate is provided with a first region and a second region that encloses the first region. The surface is provided with a plurality of types of diffraction areas each of which generates predetermined diffracted light from only a light beam having a specific wavelength and permits other light beams having other wavelengths to pass through without diffraction. The first region is provided with each of the plurality of types of diffraction areas, while the second region is provided with only a diffraction area that generates the predetermined diffracted light from only a light beam having the maximum incident diameter among the plurality of types of diffraction areas.

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

Abstract: An optical pickup apparatus, comprising: a light source to emit a light flux; a light converging system including an objective lens to converge the light flux emitted from said light source onto an optical information recording medium; a first diffraction element placed within an optical path up to the optical information recording medium; a light flux splitting element that is placed within the optical path from said light source up to the optical information recording medium and that splits an incident light flux emitted by the light source; a monitor element that receives a light flux split by said light flux splitting element and outputs a signal according to a received light amount; a second diffraction element placed between said light flux splitting element and said monitor element; and a control section that controls the drive of said light source according to the signal from said monitor element.

Abstract: Disclosed is an optical head in which position adjustment of a photodetector light receiving surface or component parts may be simplified, production costs may be reduced and operational reliability may be improved. The optical head includes a light source 22, radiating light of a preset wavelength, an objective lens 27 for condensing the outgoing light from the light source 22 on an optical disc 2 and for condensing the return light from the optical disc 2, a beam splitter 25 for branching the optical path of the return light reflected by the optical disc 2, and for collimating the branched return light so as to be parallel to the outgoing light from the light source 22, a composite optical component including a splitting prism 30 arranged on a site of incidence of the branched return light for spatially splitting the return light, and a light receiving unit for receiving plural return light beams spatially split by the splitting prism 30 for producing focusing error signals.

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. 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. Because of this, the focal length of the red light beam becomes longer than that of the blue light beam, whereby a working distance is enlarged.

Abstract: There is disclosed an optical pickup device including: a blue semiconductor laser which emits a first laser light having a wavelength of 450 nm or less to record on or reproduce from an extra-high density optical disc; a red semiconductor laser which emits a second laser light having a wavelength longer than that of the first laser light to record on or reproduce from a DVD having a low recording density; an objective lens; and an aberration correction element. The objective lens is designed for the extra-high density optical disc, and has a numerical aperture (NA) of 0.75 or more. The aberration correction element passes the first laser light as such and thereafter allows the light to be incident upon the objective lens, whereas the element limits an aperture with respect to the second laser light and diffracts the second laser light so as to correct an aberration with respect to the DVD and thereafter allows the light to be incident upon the objective lens.

Abstract: An optical device for scanning an optical record carrier (20) has a radiation source (25) that can emit two radiation beams of different wavelength along different optical paths (28, 29). The emitted radiation is focused on the record carrier and reflected back to a detection system (40). A beam combiner 43 is arranged in the optical path between the radiation source and the detection system for combining the two radiation beams on one optical path, thereby allowing the use of a single detection system for both radiation beams. The beam combiner includes a grating that passes one of the beams undiffracted and diffracts the other beam mainly in the first order. The profile of the grating lines show alternating slanting grooves and slanting lands.

Abstract: Laser beams respectively emitted from a SHG blue laser unit and a red semiconductor laser unit that have photo detectors respectively are turned into parallel lights by a collimator lens and then coupled by a dielectric multi-layer film mirror so as to be propagated on the same optical axis. The dielectric multi-layer film mirror is configured so as to transmit light with a wavelength of 500 nm or shorter and reflect light with a wavelength of 500 nm or longer for both P wave and S wave. The lights that are transmitted and reflected by the dielectric multi-layer film mirror pass through a polarizing hologram and a phase variable wave plate and are focused on an optical disk by an objective lens. In this manner, a simple configuration can realize a compatibility with many types of optical disks and a stable signal detection even when using a polarizing optical detection system.

Abstract: An optical system of an optical pick-up, which is provided with a light source that emits a light beam, and an objective lens that converges the light beam emitted by the light source onto a data recording layer of an optical disc. The optical system satisfies a condition: 0.75<d·(M?1)/(M·L)<1.0, where d (mm) represents a thickness of the objective lens, M represents magnification of the optical system, and L (mm) represents an O/I distance which is defined as a distance between an object and an image. A beam spot suitable for the optical disc is formed by the objective lens on the data recording layer of the objective lens without using a coupling lens.

Abstract: An integrated unit in which a light source and a light emitting diode are combined into one component is fixed to an optical bench. Then, relative position adjustment of an objective lens actuator is carried out with respect to the optical bench so that a desired detection signal can be obtained through reflected light from a disk information recording medium and then the objective lens actuator is fixed. The relative position adjustment of the integrated unit is no longer required and it is no longer necessary preliminarily to provide a margin for adjusting the integrated unit. Thus, an optical head can be reduced in size and thickness.

Abstract: An aberration correction element is disposed between first to third laser light sources and an objective lens, first and second laser lights emitted from the first and second laser light sources are incident upon the aberration correction element in the form of parallel lights, and a third laser light emitted from the third laser light source is incident upon the aberration correction element in the form of a divergent light.

Abstract: An optical pickup apparatus includes first, second and third light sources; a light converging optical system including a first objective optical element and a second objective optical element, wherein the first objective optical element converges the light flux emitted from the first light source on a first information recording surface, the second objective optical element converges the light flux emitted from the third light source on a third information recording surface, and the first objective optical element or the second objective optical element converges the light flux emitted from the second light source on a second information recording surface; a lens holder holding the first objective optical element and the second objective element therein; and a chromatic aberration correcting element which corrects a chromatic aberration caused by a wavelength variation in a light flux emitted by the first light source.

Abstract: An optical pickup converts a laser beam from a semiconductor laser (1) into a parallel ray with a collimator lens (2), and divides it into a main beam (30), a sub-beam (+1st order component) (31), and a sub-beam (?1st order component) (32) with a gradient multiple-division type phase difference grating (3). After passing through a beam splitter (4), an objective lens (5) condenses the light beams on a track (61) of an optical disc (6), and the reflected light that has passed through the objective lens 5 is reflected at the beam splitter (4) and is guided into optical detectors (8A, 8B, and 8C) by a condensing lens (7). Accordingly, in a tracking error signal detecting method using the push-pull signals of the main beam and sub-beams, an offset produced by an objective lens shift or a disc tilt can be cancelled at low cost without lowering the efficiency of using light.