Abstract: A photo-mask comprises a light-permeable substrate, a plurality of light-shielding films that are disposed on the substrate, the light-shielding films forming a mask pattern, and a light-permeable protective film that is disposed over the surface of the substrate including the light-shielding films so as to protect the light-shielding films.

Abstract: An optical recording element comprising a recording medium which includes an information recording area formed at every unit in a non-continuous condition, the recording medium further including sample pits disposed at intervals of a fixed distance for providing basic information about the locations of recording units in the same track. Each sample pit comprises a plurality of pits disposed next to the sequence of the recording units so that the spacing between the pits differs from the spacing between the recording units. At least one of the plurality of pits is a long-sized inclined pit which is inclined at an angle in the range of 6.degree. to 80.degree. to a recording track.

Abstract: An optical disk with a substrate made of glass at least partially has its inner and outer peripheral surfaces polished to surface roughness of 5 .mu.m or less so as to reduce the amount of glass powder generated from these surfaces and to thereby improve the yield.

Abstract: A method of and a photomask for manufacturing an optical memory element. The manufacturing method includes the steps of: subjecting a positive type photoresist coated on a glass substrate to exposure by using the photomask capable of irradiating light onto a portion of the photoresist other than the remaining portion for forming pits of the glass substrate such that the portion of the photoresist is solubilized against developing solution; developing the photoresist by using the developing solution so as to remove the portion of the photoresist; and etching the glass substrate so as to directly form, as convex portions, the pits on a surface of the glass substrate.

Abstract: An optical memory device has grooves for guiding a light spot and pits for serving as track number indicators. The width W.sub.1 and depth d.sub.1 of the grooves and the width W.sub.2 and depth d.sub.2 of the pits are so selected that 2D(W.sub.1, d.sub.1)=1+D(W.sub.2, d.sub.2) where D(W.sub.1, d.sub.1) and D(W.sub.2, d.sub.2) are respectively the reflectivity of the groove and the pit.

Abstract: A photo-mask and a method of manufacturing a photo-mask, which includes the steps of applying a resist film onto a substrate of quartz, glass and the like, subjecting the resist film to light exposure and development to form a fine resist pattern, etching the mask substrate covered by the fine resist pattern causing a non-light transmitting thin film of Cr, Ta, etc. to adhere thereon by vapor deposition, sputtering and the like, and removing the thin film on the resist pattern together with the resist film, thereby to form the photo-mask.

Abstract: A photo-mask comprises a light-permeable substrate, a plurality of light-shielding films that are disposed on the substrate, the light-shielding films forming a mask pattern, and a light-permeable protective film that is disposed over the surface of the substrate including the light-shielding films so as to protect the light-shielding films.

Abstract: A method of and a photomask for manufacturing an optical memory element. The manufacturing method includes the steps of: subjecting a positive type photoresist coated on a glass substrate to exposure, by using the photomask capable of irradiating light onto a portion of the photoresist other than the remaining portion, for forming pits on the glass substrate such that the portion of the photoresist is solubilized against developing solution; developing the photoresist by using the developing solution so as to remove the portion of the photoresist; and etching the glass substrate so as to directly form, as convex portions, the pits on a surface of the glass substrate.

Abstract: A method for manufacturing an optical memory element including the steps of disposing a resist film on a substrate, placing a photo-mask carrying a guide groove pattern on the resist film so as to position the photo-mask over a predetermined position of the substrate, forming a guide groove pattern latent image on the resist film, developing the guide groove pattern latent image formed on the resist film, conducting an etching operation through the developed guide groove pattern as to form guide grooves in the substrate, removing the resist film from the substrate, and disposing a recording medium layer on the substrate having the guide grooves formed therein.

Abstract: In an optical head of an optical memory device which records, reproduces or erases information onto or from a recording medium by applying a laser beam to the recording medium, a beam splitter is disposed in an optical path to conduct a portion of the laser beam emitted from a laser device to a light detector. In accordance with a detected value from this light detector, the influence of a stray beam generated in an optical system is removed from a servo error signal.

Abstract: A photo-mask for use in manufacturing an optical memory disc has a substrate having a disc shape and made of a transparent material, and a film deposited on the substrate and formed with a predetermined pattern of grooves extending spirally or concentrically to the center of the disc shaped substrate such as to leave a thin film at the bottom of the grooves, and a number of microscopic pits in the form of minute indentations with a predetermined spacing aligned along the grooves so as to substantially leave no film at the bottom of the indentations. Thus, a light which has passed through the thin film at grooves is weakened and a light which has passed through the indentations loses substantially no power, and a light applied elsewhere on the film is cut off.

Abstract: An optical memory element comprising a substrate with grooves functioning as grooves for, for example, controlling the position of a laser beam, wherein said substrate is composed of a glass containing SiO.sub.2 in the range of 51 to 71% by weight, Na.sub.2 O in the range of 10 to 18% by weight, K.sub.2 O in the range of 0 to 8% by weight, Al.sub.2 O.sub.3 in the range of 12 to 22% by weight, and B.sub.2 O.sub.3 in the range of 0 to 9% by weight.

Abstract: A tracking system for positioning a light spot onto a magneto-optic disc having a beam guide track preformatted thereon, includes a main light beam and two auxiliary light beams, and a circuit for switching between a low frequency component of a tracking error signal, detected by respective auxiliary light beam detectors, and a tracking error signal detected by a main light beam detector.

Abstract: A method of manufacturing an optical memory element, which includes the steps of applying a first photo-resist layer onto a glass substrate for an optical memory element, laying a mask plate on the glass substrate applied with the first photo-resist layer, with the mask plate being prepared by covering a surface of a transparent substrate with metallic layers formed into a guide pattern configuration, irradiating ultraviolet rays onto the first photo-resist layer through the mask plate, transferring the guide patterns of the mask plate onto the first photo-resist layer, and engraving the guide patterns in the glass substrate by etching after developing the first photo-resist layer.

Abstract: A photo-mask which is used for the production of a substrate for an optical memory element includes a reflective film formed over an ultraviolet non-transmissive film on a substrate. Alternatively, a multi-layer dielectric film which is not transmissive to light of wavelength about 400 nm but transmissive to light of wavelength about 450 nm is formed on a substrate.

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: A light beam position controlling apparatus includes a linear motor for driving an optical head in the radial direction of an optical disk, a radial actuator built-in within said optical head and adapted to drive an objective lens for causing the light beam to be accurately positioned in the radial direction of the optical disk and to rotate a mirror for causing the light beam to be deflected in the radial direction of the optical disk, which can be improved in the compression factor of the servo performance, by providing a phase lag compensation circuit and a damping correction circuit for increasing the gain of the transfer function at the resonance frequency of both the linear motor and radial actuator.

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 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: 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.