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: The present invention relates to an optical pickup having a constant numerical aperture even if spherical aberration is compensated for. The optical pickup is used in an information recording and/or reproducing machine. The information recording and/or reproducing machine records and/or reproduces information in a recording medium upon radiation of a light beam from a light source. The optical pickup includes a condensing optical system for condensing the light beam from the light source onto a recording layer of the recording medium. The condensing optical system includes an object lens. The condensing optical system also includes an aperture positioned about a focal length of the object lens apart from a position of a principal incidence plane of the object lens toward the light source along an optical axis of the condensing optical system.

Abstract: An information recording at a high density to an information recording medium and a proper reproduction of information which has been recorded on the information recording medium at a high density are realized. Optical characteristics of an information recording medium are measured and information regarding the measured optical characteristics is previously recorded in a proper area on the information recording medium. When an information recording system records information to the information recording medium on which the information regarding the optical characteristics has been recorded, the information regarding the optical characteristics is read and a proper information recording state is adjusted on the basis of the information regarding the optical characteristics, thereby allowing the information recording to be performed.

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 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: The present invention provides an optical lens device capable of providing an optical pickup with a stable performance by restraining the influence of the birefringence even in the case of using a plurality of resin lenses. In the optical lens device having two lenses, by disposing the two lenses relative to each other such that the birefringence directions of the lenses form a predetermined angle, preferably 180 degrees, the influence of the birefringence can be reduced as a whole and an optical lens device with a good characteristic can be obtained.

Abstract: A multi-layer-information-recording medium is applied to an information recording and reproducing apparatus capable of recording or reproducing information on and from either of a single-layer-information-recording medium having a single recording layer on one side, and a multi-layer-information-recording layer having a plurality of recording layers layered on a spacer layer on one side as a change in reflectivity by irradiating a light beam. The multi-layer-information-recording medium is compatible in terms of at least reproducing and recording with a single-layer-information-recording medium having a cover layer having a predetermined refractive index “n” and a thickness “t” disposed on a recording layer on a light incident side surface. The multi-layer-information-recording medium includes a deepest recording layer deepest from the light incident side surface.

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: The present invention relates to a rewritable multi-layer recording medium that ensure appropriate data reading from and writing in an arbitrary recording layer of a plurality of recording layers. The recording layers are stacked via spacer layers. Each recording layer is made from a material of which reflectance changes upon radiation of a light beam. Information or data is written in the recording layer as a result of reflectance change. Each recording layer has at least one groove and/or at least one pit. A certain layer in which the information is to be written (recorded) has a rewritable region. An adjacent layer has a window region through which the light beam passes and reaches the rewritable region. The window region imparts a diffraction effect, which is different from a diffraction effect impartable from a region surrounding the window region, to the passing light beam.

Abstract: In an optical pickup, the focal position of the reflected light from the information bearing surface where information is to be reproduced and that of the reflected light from other information bearing surfaces are adjusted by an optical device such that the two reflected light components are separated optically.

Abstract: An information recording and reproducing apparatus for optically recording/reproducing information to/from a two-layer optical disk comprises a cylindrical lens, which gives astigmatism to a reflected light from a target information recording layer, two caustic curve positions are arranged in the front and in the rear of the optical detector, and an unnecessary reflected light from an another information recording layer has two caustic curve positions arranged in the rear of the optical detector. In this condition, assuming an astigmatism direction of the cylindrical lens is inclined at 45 degree angle to a track direction, a projected image of the target information recording layer is inclined at 90 degree angle to an another projected image of the another information recording layer in a light receiving surface of the optical detector.

Abstract: An information recording apparatus capable of detecting an accurate tracking error even if a reflectance or a transmittance of respective information recording layers varies when information is recorded onto a multilayer optical information recording medium having a plurality of information recording layers, wherein the apparatus comprises a detecting device for detecting a position of a boundary portion between a recorded area where the information has already been recorded and an unrecorded area in the information recording layer; an inhibiting device for inhibiting recording the information onto an area in one information recording layer in a case where the boundary portion in an information recording layer may affect a tracking servo for recording the information onto said one information recording layer.

Abstract: The collision preventing device is used for an optical pickup device for recording or reproducing information to or from an optical information recording medium. The collision preventing device has a shock absorbing layer to prevent a contact of an objective lens and a surface of the recording medium. The shock absorbing layer is laminated on the portion extending from the circumferential edge of the effective-diameter area of the objective lens to the outside edge or to the outside of the objective lens and has a thickness in such a manner that the shock absorbing layer comes in contact with the surface of the recording medium prior to the effective-diameter area, when the objective lens comes close to the surface of the recording medium.

Abstract: The present invention relates to an optical pickup having a constant numerical aperture even if spherical aberration is compensated for. The optical pickup is used in an information recording and/or reproducing machine. The information recording and/or reproducing machine records and/or reproduces information in a recording medium upon radiation of a light beam from a light source. The optical pickup includes a condensing optical system for condensing the light beam from the light source onto a recording layer of the recording medium. The condensing optical system includes an object lens. The condensing optical system also includes an aperture positioned about a focal length of the object lens apart from a position of a principal incidence plane of the object lens toward the light source along an optical axis of the condensing optical system.

Abstract: The present invention relates to an optical multi-layer information recording medium for recording information therein and/or retrieving information therefrom upon radiation of a convergent beam of light. The recording medium includes at least two pairs of recording layer and light-transmissive layer stacked one after another. A first recording layer proximal to a beam radiation side and a second recording layer distal from the beam radiation side are made from a material that satisfies a function including the following parameters; transmissivity and absorptance of the first recording layer, absorptance of the second recording layer, a numerical aperture on the first recording layer, a numerical aperture of the second recording layer, and transmissivity of between the first and second recording layers. Even if the numerical apertures change with spherical aberration compensation made to respective recording layers, a power density of a light spot does not change.

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 optical recording apparatus includes: a tilt detecting device for detecting a circumferential direction component of a tilt of a recording medium with respect to a laser beam light axis; a recording pulse signal generating device for generating a recording pulse signal by coding an information signal to be recorded and outputting the generated recording pulse; a modulating device for receiving the recording pulse from the recording pulse signal generating device, and modulating an intensity of a laser beam based on the received recording pulse signal; a laser beam irradiating device for applying the modulated laser beam onto the recording medium; and a recording pulse signal control device for controlling a sending timing at which the recording pulse signal is sent from the recording pulse signal generating device to the modulating device, based on the circumferential direction component detected by the tilt detecting device.

Abstract: An optical pickup apparatus includes a photodetector for receiving a diffracted light reflected from the recording medium; and a tilt detector for detecting a tilt amount of the recording medium on the basis of a light intensity within an interference region of a 0th-order diffraction light and at least one diffraction light other than the 0th-order diffraction light of the reflected light received by the photodetector.

Abstract: An optical pickup for reading information from a recording medium comprises a light illuminating portion for illuminating a plurality of light beams having different wavefronts onto a recording surface of the recording medium to create a plurality of light spots including a first light spot and a second light spot. The first and second light spots at least partially overlap with each other. A detector receives light beams reflected by the recording medium. The detector has a first light-receiving surface for receiving reflected light of the first light spot and a second light-receiving surface for receiving reflected light of the second light spot.

Abstract: The disclosure is a molded glass objective lens. The objective lens includes a first surface having a center symmetric convex surface shape at least in a range of an optical beam passing therethrough, a second surface having a center symmetric effective surface shape at least in a range of an optical beam passing therethrough on the opposite side opposing to the first surface, and a center symmetric cylindrical side surface crossing with the first surface. A center curvature radius of the first surface is defined in a particular range led by the volume of the molded glass objective lens and the volume of a virtual lens portion surrounded by a cylindrical surface including the first and second surfaces and the cylindrical side surface.