Abstract: A record carrier is described for optically writing and reading information, which record carrier is provided with a pre-formed track. This track is formed by a ridge disposedon the substrate surface and the recording layer comprises a dye layer having such a thickness at the location of the ridge that a write beam can produce a maximum optical effect therein, the dye layer being thicker at locations outside the ridge.

Abstract: An optical record carrier having a surface layer which includes a substantially circular information track structure, such surface layer extending without interruption substantially up to the center of the track structure. When the record carrier is supported on a rotating turntable and scanned by a scanning beam producing a scanning spot having a width transverse to the track direction of at least a few times the period of the track structure, a diffracted beam is produced by the track structure in a direction transverse to the local track direction. A radiation-sensitive detection system in the path of the diffracted beam produces output signals indicating any centering error between the center of the track structure and the axis of rotation of the turntable. Such signals can be employed to control positioning means to position the record carrier on the turntable so as to eliminate such centering error.

Abstract: An optical storage medium comprises a thermoplastic resin substrate having a concave and convex surface grating on one surface thereof, and a metal layer covering the concave and convex surface grating. The period of the concave and convex surface grating is less than a wavelength of light so that light reflected from the concave and convex surface grating is changed from linear polarization to elliptical polarization, while there is no change in the polarization of light reflected from a recording pit in which the concave and convex surface grating has collapsed. Therefore, information can be read out of the optical storage medium in accordance with the change of light polarization.

Abstract: A digital recording medium formed of a thermoplastic substrate having a regular array of microscopic optically-alterable mirrors each supported by a mesa projecting from one surface of the substrate. The parallel rows of the mirrors are the same distance apart as the mirrors in each row. The medium can be formed from a single transparent thermoplastic substrate with an array of indentations in a first surface. The bottom of each indentation is coated with a reflective material. When viewed from the opposite surface of the substrate, the indentations become mesas. The reflective coating is sputtered onto the first surface thereby coating the first surface and the bottoms of the mesas. The reflective coating is then removed by abrasion from the first surface.Recording is by exposure through a second surface of the substrate to a laser beam that reduces the reflectivity of selected mirrors.

Abstract: There is disclosed an improved method of and apparatus for transporting an optical recording card along a predetermined path to a rotational reference axis whereat the card is rotated about so that concentric and/or spiral data tracks can be read by the optical reader.

Abstract: An apparatus for recording and reproducing data into/from an optical disc, which includes an optical disc having an optical recording medium into and from which data can be written and erased, a laser diode to write, erase, and read out data into and from the optical disc, and a power setting circuit for sampling and holding a detection output from a photo diode to detect the light emission power of the laser diode, for comparing the value sampled and held with a target value, and for setting the power of laser diode. A light emission power of laser diode in each of the data writing, erasing, and reading modes is controlled by the power setting means. A part of a recording area of the optical disc is provided with an extracting area to sample and hold the detection output from the photo diode.

Abstract: The invention relates to disc-shaped information carriers which can be read optically in reflection and which contain an annular information zone which is bounded by a concentric inner zone and a concentric outer zone. The information carrier consists of a transparent substrate and has a readout side and opposite side (back) which at least in the information zone has a reflective coating. The light entering the outer zone from the readout side is reflected at least partially diffusely or absorbed by the information carrier. In this way, manufacturing defects such as, for example, inclusions, inhomogeneities etc. are at least partially masked or concealed.

Abstract: A disk-type recording medium having circular or spiral tracks storing information. The tracks are radially and regularly spaced from one another. Each track has pregrooves (2), ridges, or protrusions, and discrete depressions (7,9), ridges, or protrusions. The depressions (7,9) are so disposed that the depressions of neighboring tracks do not neighbor one another. In playback, the depressions (7,9) of neighboring tracks do not cause crosstalk. Thus, the disk permits the identifying signals to be stably and correctly reproduced.

Abstract: The invention relates to disc-shaped information carriers which can be read optically in reflection and which contain an annular information zone which is bounded by a concentric inner zone and a concentric outer zone. The information carrier consists of a transparent substrate and has a readout side and an opposite side (back) which at least in the information zone has a reflective coating. The light entering the outer zone from the readout side is reflected at least partially diffusely or absorbed by the information carrier. In this way, manufacturing defects such as, for example, inclusions, inhomogeneities etc. are at least partially masked or concealed.

Abstract: An optical recording disc comprises a first bonding recess formed near an outside surface of an optical recording disc in a bonding boundary portion between a cylindrical hub and a transparent disc substrate, a disc member bonded with said transparent disc substrate through said cylindrical hub, and a second bonding recess formed near the outside surface of said optical recording disc in a bonding boundary portion between said cylindrical hub and said disc member. Accordingly, said optical recording disc can prevent remainder of a bonding material for bonding a pair of said transparent disc substrates or said transparent disc substrate and said disc member together from pushing out of the outside surface of the optical recording disc, resulting in that focusing for reading and writing an information signal can be properly performed.

Abstract: A recording disc in which two recording sheets are bonded to bonding rings at the inner and outer periphery on both sides of a circular substrate with a recess between the recording portion of the recordings sheets and the substrate. The sheets are formed of a support material anisotropy and a recording material deposited on the support. The sheets are bonded to the bonding rings with their directions of anisotropy aligned.

Abstract: A flexible magnetic disk comprises a jacket and a flexible magnetic disk sheet housed in the jacket. The flexible magnetic disk sheet is provided at the center with a circular hole for engagement with a sheet positioning member of an information writing and read-out apparatus. The jacket has an aperture for exposing the circular hole of the flexible magnetic disk sheet. The peripheral edge portion of the circular hole which comes into contact with the sheet positioning member is embossed to decrease the coefficient of friction of the peripheral edge portion to 0.45 or less, so that the flexible magnetic disk sheet is correctly positioned by the sheet positioning member.

Abstract: High storage density, optically-readable information carriers not only require a read-out side free of contaminants or dust for a faultless reading, but must also be protected against unintentional scratching when being handled on this side. For protection against scratches that usually occur due to dislocation of a disc deposited on its support, concentric elevations are provided that are structured under given conditions by clearances on the read-out side in the edge region and in the central region of the disc outside of the information structure which fills a concentric annular surface. The disc is able to slide on the elevations when deposited on the support without the annular surface, provided with the microstructure, coming into contact with the support.

Abstract: Stretched surface recording disk (SD) 10 comprises an annular support 12 having raised annular ridges 42 and 28 at its inside and outside diameters 22 and 30 with a base portion 24 in between the two ridges, and an annular recording medium film 14 held in radial tension and stretched across the base portion by adhering the film to attachment surfaces 48 and 36 near the inside and outside diameters respectively. The SD is annealed twice duringmanufacture to relieve stress in the stretched film 14. This annealing results in SD essentially free from track anisotropy and stress distribution anisotropy in the plane of the disk. As a result, data tracks are more stable than in previous SD, track density can be greater, and the SD is generally more reliable.

Abstract: An interchangeable optically readable storage disk has a substrate with a recording surface, and a cover thereon which may comprise a second substrate with a further recording layer. The disk includes a protecting arrangement at the circumference of the substrate, which includes a balancing arrangement. The balancing may be effected by apertures in the protecting arrangement, or balancing masses affixed thereto.

Abstract: A protective canister for computer discs comprises a hollow tube and a pair of end caps for closing the tube and fixing a central post therein. A stack of alternate computer discs and spacers having aligned central apertures is loaded onto the center post and clamped in the canister by way of a pair of platforms carried by the end caps about the central post. The elements of the canister are preferably constructed from hydrocarbon-based polymers and, after loading, the canister is sealed in shrink film so that the discs are protected in an environment which is free of particulate matter.

Abstract: An optical recording/reproducing disc is formed of round plastic plates between which is a recording layer capable of optically recording and reproducing signals, and a round protective layer of plastic material provided on the recording layer and having at the outer peripheral end a projection higher by 10 to 200.mu. than the inner peripheral surface of an effective recording/reproducing surface. Thus, when the disc is placed on a flat plane, a space is formed between the flat plane and the recording layer due to the projection, thereby preventing flaws from being produced by contact with dust or a foreign object.

Abstract: A record (12) comprising a convex protrusion (12a) at its center, one or more protrusions (12b) extending perpendicularly from the plane of the record at its circumferential edge, and a recording area between the center and the circumferential edge. The protrusions engage similar indentations (3b, 3e) formed in a turntable to facilitate centering and holding the record for playing and to prevent rotational slippage.

Abstract: An optical recording and reproducing disc for recording and/or reproducing information by the application of laser beams having a wavelength .lambda. in the range of 0.7 to 1.0 .mu.m, the disc being constituted by a disc-shaped base having at least one spiral guide track thereon with top surfaces parallel to the surface of the base at a height above the base different from the top surfaces of the portions of the base between the spires of the track, which height is in the range of .lambda./12 to .lambda./6, the guide track having a width approximately equal to the effective diameter of the laser beams; and a uniform thickness coating of a light recording material on the top surface of the guide track and the portions of the base between the spires of the guide track, the light recording material being a material the transmittance and/or the reflectance of which is varied by irradiation by the laser beams.

Abstract: A playback instrument for a record disc, the instrument including a turntable for supporting the disc to be played on which the disc is centered by means of a central bore, is provided with two annular, concentrically disposed, radially spaced flat bearing surfaces mounted on the turntable for the disc, the surfaces forming a rigid support, one bearing surface being disposed in the vicinity of the location of the center of such disc and the other bearing surface being disposed radially to the outside of the one surface at a distance from the location of the center of such disc, and disc holding components provided for exerting on such disc an attracting force of such magnitude as to cause the disc to contact the bearing surfaces over the entire area thereof.