Abstract: Disclosure is a collision preventive device of a pickup device in an apparatus for performing recording or reproducing, with relative movement, to or from an optical information recording medium recorded with information on a track. The device includes a contact portion to be contacted with a surface of the optical information recording medium earlier than an objective lens when the objective lens approaches the surface of the optical information recording medium, and a non-contact portion provided adjacent the contact portion not to be contacted with the surface of the optical information recording medium in an area corresponding to a path of a light spot defined by a diameter of the light spot of a light beam on the track.

Abstract: A recording method of a multilayer recording medium includes a first initializing step of initializing a lower recording layer based on a first initializing condition and a second initializing step of initializing an upper recording layer on the basis of a second initializing condition different from the first initializing condition. The second initializing condition is determined so that a transmittance of the recording layer after execution of the second initializing step is approximately equal to a transmittance of the recording layer after a predetermined data signal is recorded on an upper recording layer.

Abstract: A lens made of at least one of a resin and glass includes a lens effective diameter area, a peripheral area formed integral with the lens effective diameter area and located at a periphery of the lens effective diameter area, and at least one marker area located in the peripheral area and formed on a circle whose center is a center of the lens effective diameter area.

Abstract: A complex objective lens includes a first optical element having a first surface including a convex aspherical surface shape and an opposite side surface opposing to the first surface; and a second optical element having an exit surface through which an optical beam passing and an entry surface opposing to the exit surface. The opposite side surface opposing to the first surface of the first optical element and the entry surface opposing to the exit surface of the second optical element are directly contacted to each other.

Abstract: A light source is provided for emitting a light beam. The light beam from the light source is applied to a recording and reproducing plane of an optical disc and to a front surface of a transparent substrate of the optical disc. A photodetector is provided for detecting return light beams from the recording and reproducing plane and the front surface. A first signal is generated based on an output signal of the photodetector dependent on the return light beam from the recording and reproducing plane, and a second signal is generated based on an output signal of the photodetector dependent on the return light beam from the front surface. A signal relating to thickness information on a thickness of the transparent substrate is produced by comparing the first and second signals with each other.

Abstract: An optical information recording and reproducing apparatus capable of recording and reproducing information data accurately with respect to an optical recording medium. The optical information recording and reproducing apparatus includes an aberration correction part which corrects aberration of the optical system. The apparatus determines whether or not an aberration correction by the aberration correction part is completed based on the signal level read from the optical recording medium, while changing a spherical aberration correction amount of the aberration correction part. The apparatus commences a recording operation or a reproducing operation of the optical information recording and reproducing apparatus if it is determined that the aberration correction was completed.

Abstract: A recording layer formed between a first substrate and a second substrate. The recording layer has recording surfaces on both sides thereof. A reflecting film is formed on an outside surface of the first substrate. The first and second substrates adjacent the recording layer have different refractive indexes from each other.

Abstract: An optical recording apparatus for writing information on an optical recording medium in which a recording surface is covered with a transparent layer. The information to be written on the optical recording medium is converted into a pulse signal, and spherical aberration occurring due to an error of a thickness of the transparent layer is detected, the pulse signal being controlled in accordance with the detected spherical aberration.

Abstract: An aberration correcting apparatus and an optical pickup apparatus using this apparatus, in which a spherical aberration based on a thickness error of an optical disc substrate can be preferably eliminated and a thickness error permission range of the optical disc substrate can be widened even if an objective lens of a high numerical aperture is used.

Abstract: A tracking servo apparatus in which reflection light obtained when a laser beam is irradiated onto a recording surface of an optical disc is photoelectrically converted, thereby obtaining a photoelectric conversion signal, a tracking error signal showing a deviation amount of an irradiating position of said laser beam for a track in a disc radial direction on the recording surface is generated by the photoelectric conversion signal, a spherical aberration occurring in an optical system is detected, a level of the tracking error signal is corrected on the basis of the detection result, and the irradiating position of the laser beam is moved in the disc radial direction in accordance with the level-corrected tracking error signal.

Abstract: An aberration detector for easily detecting aberration of a lens in a short time period by utilizing an interferometer. The aberration detector includes a laser diode, a beam splitter for dividing a light beam into two light beams, an optical system for supporting a lens and converging a light beam passing through the lens to a converging point, a spherical mirror for reflecting the light beam passing through the lens, an image pickup element for detecting an interference pattern obtained by interference of a reference light and the light reflected on the spherical mirror, and an analyzer for analyzing the interference pattern. A center of a sphere constituting the spherical mirror is arranged in a position displaced from the converging point such that a plurality of circular fringes are concentrically arranged on the interference pattern.

Abstract: An information recording medium includes a substrate, and one or a plurality of layers formed on the substrate, wherein at least one of the layers is formed by mixing a base material and a hard material which has a predetermined thickness and determines a predetermined thickness of the layer.

Abstract: A variable optical unit is provided with at least two phase-shift regions for providing light with phase differences. Phase-shift amount of the phase-shift region is adjusted by the applied voltage in accordance with birefringence of an information medium. A light beam emitted from a light source is incident on the variable optical unit through a collimator lens and a beam splitter. The light beam is polarized in accordance with the aforementioned phase-shift amount of the variable optical unit and converged by an objective lens to radiate the information medium. The reflected light polarized due to the effect of the birefringence of the information medium is polarized again according to the phase-shift amount of the variable optical unit. The reflected light is thereby polarized in the direction in which the beam splitter can reflect the reflected light and then the reflected light reflected by the beam splitter is detected by the condenser lens and an optical detector.

Abstract: A phase device for providing a phase difference between an inner radius portion and an outer radius portion of a light beam which is emitted from a light source is provided in an optical path between the light source of an optical pickup apparatus and an objective lens. The light beam to which the phase difference has been provided is converged by the objective lens and irradiated to an optical disc. An interference of an inner radius portion and an outer radius portion of the returning light beam caused when the light beam is diffracted by the optical disc with ±1 primary diffracted light caused by the diffraction is suppressed. Therefore, an intensity fluctuation of the returning light beam caused by the interference is suppressed. A spherical aberration error showing a thickness error of the optical disc and a focusing error having a high linearity can be detected with high precision on the basis of the returning light.

Abstract: A pickup device and an information recording/reproducing apparatus for reproducing information in which crosstalks have been suppressed without causing an erasure or the like of the information which has already been recorded on an information recording medium. The apparatus has a light source 1 for emitting first and second lights whose polarizing directions cross perpendicularly. The first and second lights are transmitted through a grating for merely transmitting the first light and diffracting the second light at a predetermined diffraction efficiency and those lights are converged by an objective lens, thereby forming a laser beam and irradiating it onto an optical disc. At the time of the recording of information, the second light is set to a light-off mode or a low power state and the recording of information is performed by the laser beam caused by the first light.

Abstract: An optical information recording and reproducing apparatus is provided that is capable of preventing recorded data from being deleted by mistake under a recording operation mode, and, under a reproduction operation mode, is capable of highly accurately reproducing and reading information data in which crosstalk has been removed. Under the reproduction operation mode, a single laser beam is divided into a plurality of divided laser beams, and they are individually irradiated onto a recording medium. On the other hand, under the recording operation mode, the quantity of light of each divided laser beam other than one beam of all the divided beams is reduced lower than that of the one beam, and they are all irradiated onto the recording medium.

Abstract: An information recording/reproducing apparatus of the invention is equipped with an objective lens, a light source and a variable optical element having a grating which demonstrates a piezo-electric effect by means of an electric field. The light source emits and irradiates a laser beam onto the grating to generate a 0th order diffraction beam and +/− 1st order diffraction beams in accordance with first order diffraction efficiency, and the objective lens converges the 0th diffraction beam and +/− 1st order diffraction beams which are irradiated onto an information recording medium for the purpose of information recording or information reproducing. By controlling an electric field applied to the grating, the first order diffraction efficiency of the grating is adjusted, whereby light beams are generated which have power levels appropriate for various kinds of information recording media.

Abstract: A tracking error signal generating method includes: a light irradiating process of irradiating a plurality of tracks, which are on an information record medium and adjacent to each other with an interval smaller than a size of a light beam in a radial direction of the information record medium, with the light beam, while relatively moving the light beam in the radial direction and a tangential direction of the tracks with respect to the tracks; a light receiving process of receiving a reflection light from the tracks irradiated with the light beam, and generating a detection signal based on the received reflection light; a judging process of performing a judgment of a recording portion and a non-recording portion on at least one of the tracks irradiated with the light beam, on the basis of the detection signal; a signal acquiring process of acquiring a specific signal, which indicates a change of the detection signal in correspondence with a displacement in the radial direction of the light beam relative to t

Abstract: An optical pickup apparatus for properly detecting crosstalk amounts to a read signal for one track from adjacent tracks thereof and their balance. A difference between a second read signal value for one track at a time point when a first read signal value for one adjacent track is smaller than a first threshold value and a third read signal value for the other adjacent track is larger than a second threshold value and a second read signal value at a time point when the first read signal value is larger than the second threshold value and the third read signal value is smaller than the first threshold value is formed as a value indicative of a balance level of crosstalks to the second read signal.

Abstract: An optical pickup device for writing or reading data from an optical information recording medium has a recording layer whose state changes in response to a density of intensity of an irradiated light beam and a track being used for a tracking servo control system. The device includes a first light spot irradiating element for irradiating a writing or reading light beam onto the recording layer to form a writing or reading spot and a second light spot irradiating element for irradiating at least one controlling light beam onto the recording layer to form a controlling spot having a major axis extending along the track and being longer than a transverse axis perpendicular to the major axis within a level of luminous flux density keeping an original state of the recording layer, whereby a tracking servo control signal having a sufficient level is obtained.