Abstract: An optical memory device comprising:a transparent substrate; anda recording film deposited on the transparent substrate, the recording film being formed by preparing a composition in which a diarylethene-type photochromic compound is dispersed in an ultraviolet-curing polyurethaneacrylate resin of solventless type and by curing the composition by an ultraviolet ray irradiation.

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: The invention provides an optical recording medium and a method of recording, reading, and erasing information to an optical recording medium, where information is recorded, read, and erased to the recording medium by applying beams projected from a light source capable of varying wavelength of beams. The recording medium contains at least two kinds of organic compounds each presenting photochromic phenomenon and being dispersed in binder. By projecting beams onto the optical recording medium, recording, reading, and erasure of information making use of a photochromic phenomenon can be executed independently against each organic compound dispersed in the recording medium. As a result, the optical recording medium promotes to increase the information recording density in proportion to the number of the kind of organic compounds.

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 magneto-optical head wherein a light flux, which is reflected from a recording medium, is separated into its central portion and remaining portion. The central light flux portion is only used as a magneto-optical signal while the remaining light flux portion is only used as an optical servo signal.

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 magneto-optical memory element has a multi-layer construction in the order from a side first receiving light from a light-source which includes a first transparent dielectric film, a rare earth transition metal alloy film, a second transparent dielectric film and a reflective film. The magneto-optical device uses circular dichroism effect of a magnetic mater for reading information. The rare earth transition metal alloy film has a refractive index represented by n.+-..DELTA.n wherein n=3.2-3.55i and .DELTA.n=0.05-0.03i. The thickness of film is about 18 to 46 nm. The second transparent dielectric film has a refractive index of 2.0.+-.0.2 and a film thickness of 80 to 108 nm.

Abstract: An optical head for a magneto-optical disk, including a diaphragm for cutting at least an outer portion of a bundle of rays, which is provided in the course of an optical system of a signal detecting portion.