Abstract: A small-sized, large-capacity optical disk is provided which is superior in portability. The optical disk has a diameter less than 64 mm and a thickness less than 0.8 mm. Tracks are formed with a pitch less than 0.6 ?m, and the record area is divided into a plurality of zones alone the radium. The optical disk can store more than 650 MB of compressed data.

Abstract: A magneto-optic memory device includes a transparent dielectric film of a non-oxygen containing nitride material deposited by sputtering on a substrate such as glass, a rare-earth/transition metal alloy recording medium deposited by sputtering on the dielectric film and a reflecting film deposited over the recording medium with or without an intervening transparent dielectric film of non-oxygen containing nitride material. This arrangement prevents the recording medium from being oxidized, and stablizes coercive force characteristics and information recording characteristics of the recording medium.

Abstract: A magneto-optic memory device which comprises a recording medium deposited by sputtering on a substrate such as glass, a transparent dielectric film formed on the recording medium, and a reflecting film deposited on the transparent dielectric film. This arrangement prevents the recording medium from being oxidized, and stabilizes coercive force characteristics and information recording characteristics of the recording medium.

Abstract: In the optical recording element of the invention, alignments of long thin pits inclined in various directions with respect to the track direction are formed on the tracks and information is recorded therein according to the different inclines of the pits, thereby performing higher-density and larger-volume recording without reducing the spacing between each pit and the track pitch. The invention also discloses an optical data retrieval system for use with the above optical recording element, which scans the pit alignments with a laser beam spot, detects the inclines of the pits by obtaining the distribution of the intensity of reflected light which is caused by light diffraction at the pits, and plays back information in accordance with the inclines. Therefore, not only can the substantially same structure as that of a standard type optical data retrieval system be applied to the invention without making any complicated change, but also cross-talk is less likely to be produced in the read out signals.

Abstract: An optical recording element according to the present invention comprising: (i) a transparent substrate through which light passes; (ii) a transparent low-resistance layer having a specific resistance so as to prevent the adhesion of dust to the surface of the element caused by a static charge, the layer being formed on the surface, on which a light beam is incident, of the transparent substrate; and (iii) an optical thin film composed of at least one layer, formed on the other surface of the transparent substrate so as to transmit light beams used for recording, erasing and playback, and reflect lights which have wavelengths different from the wavelength of the above light beams and are within a specified visible region of the spectrum. With this arrangement, lights within a specified visible region of the spectrum are reflected so that the element appears to be colored according to the wavelengths of the reflected lights.

Abstract: In the optical recording element of the invention, alignments of long thin pits inclined in various directions with respect to the track direction are formed on the tracks and information is recorded therein according to the different inclines of the pits, thereby performing higher-density and larger-volume recording without reducing the spacing between each pit and the track pitch. The invention also discloses an optical data retrieval system for use with the above optical recording element, which scans the pit alignments with a laser beam spot, detects the inclines of the pits by obtaining the distribution of the intensity of reflected light which is caused by light diffraction at the pits, and plays back information in accordance with the inclines. Therefore, not only can the substantially same structure as that of a standard type optical data retrieval system be applied to the invention without making any complicated change, but also cross-talk is less likely to be produced in the read out signals.

Abstract: A process for preparing blazed holograms suitable for mass-production which includes fabricating a glass or metal plate having a surface of serrated cross section, disposing the glass or metal plate in an injection mold to allow the surface of serrated cross section to constitute an inner surface of the mold. Then injecting an acrylic resin in molten form into the mold under a specific molding pressure, and removing a molded acrylic resin from the glass plate or metal plate to obtain an acrylic blazed hologram.

Abstract: An object lens driving device causes partial rotation of movable members holding an object lens on an X-Y frame perpendicular to the optical axis of the object lens about a resilient hinge member as a fulcrum. The movable members are supported by base members. The hinge member interconnects the movable members and the base members. Electro-magnetic coils and magnets effectuate relative rotation of the movable members with respect to the base members about the hinge member. A rotational axis passing through the hinge member also passes through the position of center of gravity of the movable members and the balanced position of moment of inertia of the movable members.

Abstract: One of the preferred embodiments of the present invention provides an entirely novel thin-film magnetic-head assembly for a digital-signal recording/reproducing system using multiple tracks. The assembly comprises electronic-circuit components including a combined capacitor/resistor a constant-current source, an amplifier, and an analogue-signal multiplexer, all located inside a casing that surrounds the thin-film magnetic-head. These electronic circuits are present on the upper and lower surfaces of the casing and are connected by means of an elastomer so that these circuits are integrally connected to the thin-film magnetic head.The thin-film magnetic head of the casing may alternatively be bent and extended so that electronic-circuit components can be mounted to it.

Abstract: A magneto-optical memory device includes a recording medium having a magnetic anisotropy in a direction perpendicular to the main surface thereof. A semiconductor laser is employed in an optical system of the magneto-optical memory device for reproduction purposes. A polarization beam splitter is disposed in the optical system. A multi coated dielectric thin-film is deposited on the reflection surface of the polarization beam splitter in order to establish a desired relationship between the reflection of the P-polarization component and the S-polarization component.

Abstract: Disclosed below is a control device for positioning an optical focus in an optical disc apparatus that records, plays back, and erases any information by irradiating optical beams such as the laser beams onto a recording media composed of magnetic film, wherein the control device is characterized in that; it incorporates a focussing permanent magnet that makes up a closed magnetic circuit, a focussing yoke plate, a focussing yoke, and a focussing device coil installed so that it crosses a focussing magnetic space existing that exists between the focussing yoke plate and the focussing yoke so that the focussing magnetic space can be created in an area close to the recording media which is installed in the closed magnetic circuit. In addition, the optical focus position control device that executes both the tracking and focussing control operations for the optical disc apparatus also includes mechanism that drives the objective lens in the direction of dual axes, i.e.

Abstract: An optical memory disc includes a glass substrate on which a plurality of concentric circular guide grooves (or a spiral groove) are formed for tracking purposes. A centering plate is secured to the glass substrate in a manner that the center of a circular opening formed in the centering plate is exactly adjusted to the center of the plurality of concentric circular guide grooves (spiral groove). The circular opening formed in the centering plate is utilized to drive the optical memory disc on a turntable. Since the circular opening is not formed directly in the glass substrate, the center adjustment is easily conducted, and there is no possibility that the glass substrate is damaged when the circular opening is formed.

Abstract: An optical focus position control system in an opto-magnetic disc apparatus includes a tracking control device and a focus control device. The tracking control device includes an intermediate holder, a tracking parallel spring which connects an cylindrical objective lens support to the intermediate holder while ensuring movement of the cylindrical objective lens support in the radial direction of the opto-magnetic disc, and a tracking drive mechanism to shift the cylindrical objective lens support in the radial direction within the intermediate holder. The focus control device includes a stationary holder, a focusing parallel spring which connects the intermediate holder to the stationary holder while ensuring movement of the intermediate holder in the direction of the optical axis of laser beams emitted through the optical focus position control system, and a focusing drive mechanism to shift the intermediate holder in the optical axis direction within the stationary holder.

Abstract: Concentric guide grooves are formed on a glass substrate, and recording medium is disposed on the glass substrate having the concentric grooves. A centering device is secured to the glass substrate in a manner that the center of the centering device is positioned at the center of the concentric guide grooves. In a preferred form, photopolymer is disposed between the centering device and the glass substrate as adhesive. The centering device is provided with an aperture through which ultraviolet rays are applyed to the photo-polymer to cure it.

Abstract: A magneto-optic memory element includes a transparent substrate, a first transparent nitride film, a GdTbFe recording layer, a second transparent nitride film, and a reflection film formed in this order. The first transparent nitride film has an index of refraction higher than that of the second transparent nitride film. In a preferred form, the first transparent nitride film is a SiN film having the index of refraction of about 2.0, and the second transparent nitride film is an AlN film having the index of refraction of about 1.8 to 1.9.

Abstract: A magneto-optical head assembly for a reflection type magneto-optical memory apparatus uses a laser beam for recording, retrieving, and erasing data on a recording medium comprised of a vertical, magnetic, and anisotropic thin film. The light beam emitted from the head assembly is guided to a fixed position on said recording medium. Included are a light detection apparatus for receiving a control signal, and a separate light detection apparatus for receiving a data signal. A beam splitter, to which has been applied a multicoated thin film dielectric body capable of increasing the Kerr rotation angle of the laser beam reflected from the recording medium, is positioned in the optical system through which the laser beam passes.

Abstract: An optical memory element includes stripe-shaped grooves formed directly on a glass substrate. To manufacture the optical memory element, a resist film is disposed on the glass substrate, and a groove pattern is formed in the resist film. A reactive ion etching is conducted through the groove pattern formed in the resist film so as to form the guide grooves in the glass substrate. After removing the resist film from the glass substrate, a magneto-optical recording layer is formed on the glass substrate.