Abstract: An optical lens to be arranged in an optical information recording and/or reproducing apparatus includes at least one lens main body; an antireflective film arranged on a first lens surface which has the largest surface angle on an outer peripheral portion in an effective radius of lens surfaces on the lens main body; wherein for a light entering perpendicularly to a central portion of the first lens surface whose central portion has a surface angle of 0 degree, a spectral reflectance of the antireflective film has one or more regions in which the spectral reflectance is continuously 4% or below and the wavelength includes at least a part of a wavelength region of 300 to 1000 nm, the broadest wavelength region of the one or more wavelength regions extends from wavelength ?1 to wavelength ?2 and the wavelength ?1 is in a range of 348-460 nm.

Abstract: An optical disk apparatus for correcting astigmatism that influences the read/write. If there is astigmatism, and auto-focus and tracking control are in operation, then a push-pull signal amplitude and a 2T signal amplitude vary with the variation of an amount of spherical aberration, resulting in two cases. In one case, the amount of spherical aberration to give the maximum value of push-pull signal amplitude agrees with the amount of spherical aberration to give the maximum value of 2T signal amplitude, and in the other case the two amounts do not agree. If there is no astigmatism, two amounts agree each other. If there in no agreement, then correction is made by using an astigmatism correcting element until the agreement is reached between the two. In the case where two amounts agree, specification is made for the existence and angle of astigmatism, and correction is made by using focus error signals from adjacent tracks.

Abstract: The present invention discloses a method and an apparatus for compensating astigmatism in an optical storage system. Firstly, the optical storage system focuses on an optical disc and proceeds track seeking. While track seeking, the astigmatism compensator continues adjusting and an astigmatism index signal is also measured. At last, an optimal astigmatism compensated value of the astigmatism compensator is acquired based on the measured result of the astigmatism index signal.

Abstract: A method for setting the spherical aberration correction of a scanning beam in a device for scanning an information layer of an optical record carrier.

Abstract: A pickup lens with a phase compensator is composed of a condenser lens and a phase compensator. At least one surface of the condenser lens has a step-like annular zone structure to compensate wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t1 with a laser beam having a wavelength ?1 and wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t2 with a laser beam having a wavelength ?2. The phase compensator compensates wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t3 with a laser beam having a wavelength ?3.

Abstract: An optical pickup apparatus has a semiconductor laser source which emits a laser beam in a wavelength band of 405 nm having an elliptic light intensity distribution; a beam shaping element which shapes the light intensity distribution of the laser beam; a polarizing beam splitter having a polarized light separation film in contact with the air and reflecting the laser beam shaped by the beam shaping element on the polarized light separation film; and an objective lens which focuses the laser beam reflected on the polarized light separation film onto an optical information recording medium.

Abstract: An optical pickup includes a light source, an objective lens, light detectors, an optical system, and an error-signal generator. The light-receiving surface of at least one of the light detectors has a width extending in a first direction corresponding to a radial direction of an optical disk, and is formed by first to sixth photoreceptors arrayed along the first direction. The first and second photoreceptors, the third and fourth photoreceptors, and the fifth and sixth photoreceptors are disposed axisymmetrically with respect to a center line extending perpendicularly to the first direction. The error-signal generator generates a focus-error signal using a sum signal of detection signals output from the first and second photoreceptors or a sum signal of detection signals output from the first to fourth photoreceptors in a light spot size method, and generates a tracking-error signal using the other sum signal in a differential compensate push-pull method.

Abstract: The invention presents an optical element with which an optical head can be configured, in which there is little deterioration of the correctional effect when the objective lens shifts, as well as an optical head and an optical recording/reproducing apparatus using such an optical element. The invention also presents a novel optical recording/reproducing apparatus and optical recording/reproducing method. The optical element, includes a first voltage application electrode 13, a first opposing electrode 17 arranged in opposition to the first voltage application electrode 13, and a first phase changing layer 15 arranged between the first voltage application electrode 13 and the first opposing electrode 17. By changing a voltage between the first voltage application electrode 13 and the first opposing electrode 17, a phase that converts plane waves into spherical waves is imparted on light that is incident on the first phase changing layer 15.

Abstract: An optical pickup includes a hologram element. The hologram element is provided with a hologram pattern including a splitting section for focus which splits light used for the detection of an FES and a splitting section for tracking which splits light used for the detection of a TES. The splitting section for tracking is formed in a region excluding a region interposed between a first virtual straight line and a second virtual straight line. The first virtual straight line is drawn on the hologram element in parallel to an X direction and passes through an optical axis of reflected light entering the hologram element in a state where the objective lens is in a neutral position, and the second virtual straight line is drawn in parallel to the first virtual straight line, while being spaced at a distance d from the first virtual straight line.

Abstract: An optical head including a housing that supports an objective lens driving device, which drives an objective lens. A main-shaft and sub-shaft support the housing such that the housing slides along a radial direction of an optical recording medium along the main-shaft and the sub-shaft. A main-bearing is formed on the housing that supports the main-shaft so that the main-shaft can slide free through the main-bearing. A sub-bearing is formed on the housing and supports the sub-shaft so that the sub-shaft can slide free through the sub-bearing. At least one slot is formed in the sub-bearing at a portion that contacts the sub-shaft.

Abstract: This optical pickup has a nonvolatile memory from which data can be electronically read out, and stores as data the difference between the spherical aberration when the readout signal jitter reaches a minimum, and the spherical aberration when the tracking error signal amplitude reaches a maximum. The positioning of an optical detector or detection lens is adjusted so that the focus error signal is almost zero when the readout signal jitter reaches a minimum. The invention provides a method for performing high-precision adjustment of the focus offset and spherical aberration, even in the case of a disk which does not have data recorded on it.

Abstract: An optical pickup device includes: a light source; a light receiving sensor, having main tracking light detection faces and sub-tracking light detection faces; and a hologram, having tracking areas that are divided into main tracking areas and sub-tracking areas along division lines in the tangential direction. In the hologram, each of the tracking areas is alternately divided into the main tracking areas and the sub-tracking areas along the division lines in the radial direction, and the same width is employed in the radial direction for the main tracking areas and the sub-tracking areas.

Abstract: An apparatus for optically recording information in a recording medium and for optically reproducing the recorded information includes a semiconductor laser, an objective lens that focuses light beams from the laser on the recording medium, and a light-attenuating element for attenuating an amount of light of the light beams. The light-attenuating element has a transmittance distribution for shaping the section of the light beams into an approximate circle.

Abstract: A light focusing optical system focuses light, for recording to and/or reproducing from a plurality of optical recording media of different kinds, onto the recording media by using a diffraction element and lens. The diffraction element has at least first and second diffractive surfaces. The first diffractive surface diffracts light whose wavelength is 630 nm or more and 670 nm or less to perform aberration correction on an optical recording medium whose cover layer has a thickness of approximately 0.6 mm. The second diffractive surface diffracts light whose wavelength is 400 nm or more and 415 nm or less to perform aberration correction on an optical recording medium whose cover layer has a thickness of approximately 0.1 mm or approximately 0.6 mm.

Abstract: According to one embodiment, a spherical aberration correction apparatus includes a pickup which applies laser light to an optical disk through an objective lens, a photodetector which detects laser light incident through the objective lens as reflected light from the optical disk, a liquid crystal panel which corrects a spherical aberration of the objective lens with respect to the laser light, a flash-ROM which stores in advance an optimum relationship between a defocus position and a spherical aberration for various optical disk thicknesses, and a control module which measures a thickness of the optical disk by detection of laser light applied to and reflected from the optical disk, and controlling the liquid crystal panel to collect the spherical aberration in accordance with the defocus position of the relationship stored in the flash-ROM for the measured optical disk thickness.

Abstract: A disk drive apparatus includes: an optical pickup irradiating a laser beam onto an optical disk having one or more recording layers through an objective lens and receiving the laser beam reflected from the optical disk; a driving unit moving the objective lens in an optical axial direction of the laser beam to the optical disk in accordance with a driving signal; an interlayer distance measuring unit measuring interlayer distances of a plurality of recording layers of the optical disk; and a spherical aberration correcting unit obtaining a spherical aberration correction value for correcting a spherical aberration due to the objective lens to one of the recording layers of the optical disk. A spherical aberration correction value to another one of the recording layers is obtained on the basis of the measured interlayer distances and the obtained spherical aberration correction value to the one recording layer.

Abstract: When an image is formed on an optical disk, an optical disk image forming device reads information written in an information area of the optical disk. When a reflection preventing process is applied to an image forming area of the optical disk, the optical disk image forming device corrects at least one of a laser power or a focus gain in accordance with information about the image forming areawritten in the information area. Thus, the optical disk image forming device can form the image with a clear brightness and a good visibility on the image forming area of the optical disk without allowing a rainbow-color to appear or a face or a background to be reflected due to the interference of light.

Abstract: An optical reading apparatus with aberration-correcting functionality includes a light source, a lens, a liquid crystal layer and an electrode set. The light source of the optical reading apparatus emits light, which is converged onto a storing medium by the lens for accessing data stored in the storage medium. The liquid crystal layer is disposed in an optical path between the light source and the storage medium. The electrode set provides a variable electrical field across the liquid crystal layer for changing the refractive index of the liquid crystal layer. Aberration of the optical reading apparatus can thus be corrected.

Abstract: A near-field light-emitting element includes a transparent medium having a plane of incidence into which a laser beam enters, and a light-condensing plane on which the laser beam having entered the plane of incidence is concentrated, and a metal body provided on the light-condensing plane of the transparent medium having a first surface contacting the light-condensing plane, a second surface opposing the first surface, and an aperture which is formed to penetrate through the first and second surfaces at a position where the laser beam is concentrated and which emits a near-field light obtained from the laser beam. The metal body is arranged apart from a center of the aperture by a predetermined distance to connect together the first and second surfaces, and has a plasmon reflection plane that reflects toward the aperture a surface plasmon excited on the first and second surfaces by the laser beam concentrated at the aperture.

Abstract: The present invention provides an apparatus of an optical disc drive for adjusting a focus error signal. The apparatus includes a focus offset determining unit and an adjusting module. The focus offset determining unit is utilized for determining a target focus offset corresponding to a target condition, and the adjusting module is coupled to the focus offset determining unit and utilized for receiving the focus error signal and adjusting the focus error signal with the target focus offset to generate an adjusted focus error signal.

Abstract: An aberration correction apparatus includes an optical pickup having a liquid crystal panel for correcting an aberration of a light beam emitted from a light source and irradiated on a recording medium and a control unit which applies, to the liquid crystal panel, a bias voltage in order to correct the aberration. The bias voltage is a voltage at which a diffraction generated in the light beam passing through an electrode gap portion between electrode portions of the liquid crystal panel is minimum. For instance, the bias voltage is the voltage at which a phase difference between the light beam passing through the electrode portions of the liquid crystal panel and the light beam passing through the electrode gap portion is an integral multiple of a wavelength of the light beam. It is thereby possible to prevent unnecessary diffracted light from being generated by the liquid crystal panel for correcting the aberrations.

Abstract: An optical disk unit capable of correcting a spherical aberration without using special patterns is provided. Also provided is an aberration correcting method used for such an optical disk unit. An objective lens 7 is moved along an optical axis by a predetermined distance from an in-focus position in a first direction, and then, is moved by the predetermined distance from the in-focus position in a second direction that is opposite to the first direction. In each of the objective lens moved states, a random signal having a plurality of amplitudes and periods is reproduced from an optional area of an information recording layer 12 of an optical disk 11.

Abstract: To achieve stable, high capacity, high speed recording. Of two light beams emitted from a light irradiation means, one or two beams are made pass through an optical path changeable member whereof at least one of the thickness and refractive index changes continuously or in two or more steps immediately after emission from the light irradiation means, so that a difference is introduced into the optical path length of the two beams, and the focusing point of one beam is made to vary to coincide with a position in the recording layer used for playback or recording. Another light beam is used for servo. Converging of light during recording or read of a multilayer recording medium is performed with higher precision than in the prior art, so higher density, higher capacity recording/playback can be performed.

Abstract: Defocus detection device and method capable of detecting a defocus accurately during recording of information to an optical disk having a plurality of recording layers and an optical disk unit using the device and method are provided. A temporal restriction is imposed on defocus detection and besides, in comparison with a level for detection of a first change of a focus error signal developing during a defocus, a level for detection of a successively occurring second change of a polarity inverse to that of the first change is made to be smaller. When the first level is exceeded and thereafter the second level is exceeded within a restricted time, a defocus is detected.

Abstract: An optical information apparatus of the present invention includes: an optical pick-up head including: a light source; a diffraction unit; a condensing unit; a beam splitter; a photodetector; and a tracking error signal generator. An optical recording medium has tracks arranged substantially at a constant pitch. An average of a pitch is tp. When a main beam is placed on the track, a first sub-beam and a second sub-beam are placed between the tracks.

Abstract: An optical disc device of the present invention includes spherical aberration changing means for changing spherical aberration occurring on a converging position of a light beam converged by a lens, an actuator for moving the spherical aberration changing means in a relatively precise manner, and an actuator for moving the spherical aberration changing means in a relatively rough manner. The optical disc device drives a second actuator and a third actuator based on a signal of spherical aberration detecting means and performs control so that spherical aberration is almost 0. The third actuator moves the spherical aberration changing means based on a direct current component included in a signal of the spherical aberration detecting means, and the second actuator moves the spherical aberration changing means based on an alternating current component included in the signal of the spherical aberration detecting means.

Abstract: A rewritable optical disk apparatus, optical information recording and reproducing apparatus or the like is allowed to automatically and properly adjust the optical system to the optimum focal condition regardless of the readout signal detector's positional error and the residual aberration in the optical system. The spherical aberration and defocus are coarsely adjusted using the amplitude (PP amplitude) of the tracking error signal and then finely adjusted using the amplitude (RF amplitude) of the readout signal. Since the spherical aberration can properly be adjusted, it is possible to raise the reliability of the readout signal.

Abstract: The present invention relates to a method and a corresponding apparatus for recording an information on a recordable optical record carrier (2) by irradiation of a light beam through optical means (3-7) onto said record carrier (2) for forming marks and lands representing said information along an information recording direction (t). To obtain a higher recording density, and thus higher data capacity, it is proposed according to the present invention to reduce the numerical aperture of the optical means (3-7) in the direction (r) orthogonal to the information recording direction (t), which is the radial direction for an optical disc, during recording of information to obtain a light beam having a substantially oval spot profile having a shorter axis in the information recording direction (t), i.e. the tangential direction for an optical disc, compared to the direction (r) orthogonal that to, i.e. the radial direction.

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: There is provided a recording/playback device able to differentiate the type of an optical disc or another such optical recording medium with a high degree of precision while correcting wavefront aberrations. The recording/playback device has a detection part for sequentially detecting the surface of a cover layer and one or a plurality of signal recording surfaces of an object to be detected on the basis of an output signal of a photodetector, a medium differentiation part for differentiating the type of the detected object on the basis of the detection results, an aberration correction element, and an aberration control part for controlling the aberration correction state of the aberration correction element.

Abstract: According to one embodiment, a laser drive circuit which supplies a drive current to a laser element which outputs light at a predetermined wavelength, and a laser control circuit which supplies a predetermined timing pulse for generation of relaxation oscillation in a laser drive current supplied to the laser drive circuit, the laser control circuit supplying a laser drive current higher than a threshold value which is supplied from the laser drive circuit to the laser element to enable laser light to be output from the laser element, the laser control circuit setting the laser drive current to a level lower than the threshold value on the basis of the timing pulse.

Abstract: According to one embodiment, a laser drive circuit includes a photodetector which receives part of laser light emitted from a laser element to a recording medium independently of reflection laser light reflected by the recording medium, and outputs an output corresponding to the strength thereof, an integration circuit which integrates the output from the photodetector for a predetermined time, and a setting circuit which sets the intensity of a laser drive current supplied to the laser element on the basis of the output from the integration circuit.

Abstract: An electron beam recorder includes an electron optical system for irradiating an electron beam on a master of an information recording medium and an electron beam irradiation position detecting unit for detecting an irradiation position of the electron beam in the electron optical system while the electron beam is being irradiated on the master by the electron optical system.

Abstract: An optical disc device comprises a spherical or coma aberration correction unit to pre-correct spherical or coma aberration occurring in the light beam, a focus or tracking detection unit operable to detect a focus or tracking error signal, and an FE or TE amplitude adjustment unit operable to adjust the signal amplitude of the focus or tracking detection unit to a specific value after the amount of spherical or coma aberration has been matched to a specific value by the spherical or coma aberration correction unit.

Abstract: An optical information processor reads information from a storage medium or writes information on a storage medium by irradiating it with light radiated from a light source. The processor includes: the light source for radiating the light; a condensing element for converging the light, radiated from the light source, toward the storage medium; and a detector for detecting a portion of the light radiated from the light source. Supposing that in a far-field pattern of the light radiated from the light source, an aperture area A is defined by a portion of the light entering the condensing element and a photosensitive area B is defined by another part of the light entering the detector and that the light has the narrower angle of radiation in an x direction and the wider angle of radiation in a y direction, respectively, the center of the photosensitive area B in the x direction is offset with respect to that of the far-field pattern in the x direction.

Abstract: A method for determining runout disc is disclosed. The method comprises: focusing on a focal point on a disc; driving the disc to spin the disc; generating a crossover signal according to a track of the disc crossing the focal point; and determining that the disc is a runout disc when the frequency of the crossover signal exceeds a pre-determine value.

Abstract: A lensless optical servo system (100) has an unfocused light source (102) and patterned photodetectors (104, 106, 108). The unfocused light is reflected by the markings on an LS-120 disk (40) and the reflected light carries the pattern of the markings the considerable distance in its far-field to the photodetectors (104, 106, 108). The convolution of this light pattern and a mating geometric pattern (110, 112, 114) on the photodetectors (104, 106, 108) causes the photodetectors to generate signals representing the position of the track on the disk. According to a presently preferred embodiment, a laser diode (102) and three detectors (104, 106, 108) are formed on the same silicon substrate (101). Sinusoidal metalization (110, 112, 114) is applied to the detectors (104, 106, 108) in the radial direction. The period of the sinusoidal metalization is two times the tracking pitch of the disk radially and tangentially.

Abstract: An optical disc apparatus includes: a light irradiation unit irradiating light to an optical disc to record and reproduce data; a focus position adjustment unit adjusting a focus position of the light irradiated from the light irradiation unit to the optical disc; a measurement unit measuring a correspondence relation between a light amount at a recording time of data to the optical disc at a predetermined focus position and a recording quality by controlling the irradiation unit; and a determination unit determining an optimum focus position based on a result of the measurement.

Abstract: It is aimed to provide an optical head, an optical head manufacturing method and an optical disc device capable of correcting coma aberration generated due to different positions of emission points of a plurality of laser lights having different wavelengths. A two-wavelength laser light source 1 is arranged to correct coma aberration generated in a radial direction of a CD 80 in the case where an objective lens 6 is tilted to locate an inner peripheral end of the objective lens 6 in the radial direction of the CD 80 lower than an outer peripheral end thereof, and an objective lens actuator 9 tilts the objective lens 6 to locate the inner peripheral end of the objective lens 6 in the radial direction of the CD 80 lower than the outer peripheral end thereof.

Abstract: An optical pickup device comprises a light emitting element which emits laser light, a photodetector which monitors a state of the laser light emitted from the light emitting element and applies feedback to a control of the light emitting element, and a reflect mirror which allows a portion of the laser light emitted from the light emitting element to be irradiated to the photodetector, wherein a rough surface portion is provided on a surface of the reflect mirror to avoid an erroneous operation of the optical pickup device.

Abstract: A method and apparatus for recording and/or reproducing holographic data and a holographic information storage medium, wherein the apparatus for recording and/or reproducing holographic information includes an optical pickup emitting light onto a holographic information storage medium and receiving the emitted light. The optical pickup includes: a light source unit emitting a signal beam and a reference beam in a recording mode; and a focusing optical system focusing the signal beam and the reference beam on one focal point in the holographic information storage medium so that information can be recorded by using an interference pattern formed along a depth direction of the holographic information storage medium in the vicinity of the focal point, wherein the numerical aperture of the focusing optical system for the signal beam is different from the numerical aperture of the focusing optical system for the reference beam.

Abstract: An optical disk apparatus according to the present invention includes: a light emission section for emitting laser light; an optical system for irradiating the optical disk medium with the laser light; and an aberration control section for controlling aberration of the laser light. In one embodiment, the aberration control section repeatedly switches between a plurality of aberration setting states in a focus lock-in operation. In another embodiment, the aberration control section simultaneously sets a plurality of aberration setting states in a focus lock-in operation. As a result, a plurality of aberration setting states can be allowed to substantially coexist within a single optical system.

Abstract: The invention is to provide an optical pickup capable of performing a track search operation accurately by reducing noise occurring in a focus servo system during the track search operation and also accurately recording/reproducing information to/from an optical disk. An optical pickup PU for emitting a light beam B to an optical disk DK in which recording tracks having a land/groove structure are formed and receiving reflection light of the emitted light beam B, has: a liquid crystal panel 3 for correcting astigmatism included in light beam B by a cause peculiar to an optical system as a component of the optical pickup PU in a state where tracking servo is on, and correcting the astigmatism and a fundamental track crossing noise in a state where the tracking servo is off, and a liquid crystal panel control unit 8 for operating a liquid crystal panel 3 while making a switch in accordance with the state of the tracking servo.

Abstract: An apparatus and method control a disk drive servo, and more particularly, an apparatus and method control a servo when moving between layers of a disk in a multi-layered disk drive. A focus controlling method, as an example of the servo controlling method, includes the operations of performing aberration correction according to a change of a recording layer of a disk from a currently accessed recording layer to a recording layer desired to be accessed, and changing the value of a parameter set that determines characteristics of signals for use in servo control of an optical disk drive, according to an aberration correction amount that is used during the aberration correction.

Abstract: The invention relates to an optical disk drive. The optical disk drive has an objective lens to be driven by a focus actuator with a focus offset for focusing an incident beam onto an optical disk into a spot with a spherical aberration, and a processor to derive a first and a second characteristic from a sensor output signal and obtain a spherical aberration correction value (SA) from a pre-determined function, the pre-determined function defining a spherical aberration correction value in dependence on a focus offset difference value (?FO). The focus offset difference value (?FO) is determined from a difference between a second optimal focus offset at which the second characteristic is optimal and a first optimal focus offset at which the first characteristic is optimal. The spherical aberration correction value (SA) can be used to achieve a correction to the spherical aberration of the spot.

Abstract: An optical disk apparatus having an aberration correcting unit for correcting aberrations generated on the recording surface of an optical disk based on received correcting signals, a servo signal generating unit for generating servo signals based on the reflection lights from the optical disk and predefined parameters, and a birefringence detecting unit that detects the degrees of birefringent portions on the recording surface based on received the servo signals and generates the correcting signals for correcting aberrations according to the detected degrees of the birefringent portions and outputs the correcting signals.

Abstract: An aberration correction apparatus includes an optical pickup having a liquid crystal panel which gives a phase difference to a light beam emitted from a light source unit and irradiated onto a recording medium and corrects an aberration occurring to the light beam by a tilt of the recording medium, and a control unit which applies, to the liquid crystal panel, a correction voltage correspondent to an amount of the aberration in reference to a bias voltage. The bias voltage is set for each of the recording mediums so that the correction voltage applied for correcting the aberration of the same amount caused by the disc tilt becomes equal for different kinds of recording mediums. Namely, even when the plural kinds of recording mediums are used, if the disc tilt angles are same, the aberration can be corrected by applying the same correction voltage.

Abstract: An apparatus which stabilizes an operation of a disc driver in a mode conversion setting section includes a pickup which reads information from a disc that is inserted into the disc driver, a filter which performs a low-pass filtering of a servo error signal that is generated during an operation of the pickup, a selector which selects one of the servo error signal and the low-pass filtered servo error signal from the filter and outputs the selected servo error signal to drive the pickup using the selected servo error signal, and a control signal generator which generates a signal to control the selector to select the low-pass filtered servo error signal in a mode conversion setting section of the disc driver. Accordingly, a defocus and a detrack can be prevented in the mode conversion setting section of the disc driver.

Abstract: In a optical head, a beam is emitted from a light emitting element in which a plurality of light sources are integrally formed, the light sources being able to emit beams having different wave lengths from one another. An optical system converges the beam coming from any one of the light sources onto an optical information storage medium. An optical separator separates a reflected beam coming from the optical information storage medium from the beam coming from the light source. A light receiving element detects light quantities of the reflected beam separated by the optical separator.

Abstract: An optical disc apparatus for recording, reproducing or erasing an information signal by converging a light flux onto a recording layer through a transparent substrate. The apparatus includes one or a plurality of optical heads having a plurality of objective lenses whose aberrations have respectively been corrected for a plurality of disc substrates of different thicknesses, a cartridge for enclosing the optical disc, a discrimination hole which is formed on the cartridge, and a sensor for detecting the opening/closing state of the discrimination hole and for generating a discrimination signal. In accordance with the result of the discrimination as to the thickness of the loaded optical disc, the objective lens, in which the occurrence of the aberration is smallest, is used, so that the information signal can preferably be recorded, reproduced or erased onto/from the optical discs having different substrate thicknesses.