Abstract: The disclosure relates to an optical disk of the type including at least one spiral track on which information marks are written in sectors whose addresses are substantially sequential along the track, wherein said disk includes a copy protection zone (PZ) comprising two parts of equal size each including a series of sectors designated by identical addresses on each of the two parts, the data written in this zone being shared between the sectors of the two parts, each sector of the zone also carrying an identifier (D1, D2) characteristic of the part to which the sector belongs, and specific protection data to enable verification of the presence and constitution of said protection zone (PZ) and to enable use of the data written in this zone, at least part of said specific protection data being recorded on said disk. The invention is notably applicable to anti-piracy protection of CD-ROM and DVD-ROM type disks.

Abstract: A pirate-proof optical recording disc and a process for reading such a disc. The disc includes a spiral main track and a secondary track span interposed between two successive turns of the main track. An initialization zone includes a datum regarding the nature of the pirate-proof disc and a datum for relative positioning of the span, to which the reader goes by travelling to an address of the main track and by effecting a track jump. The span is identified by an identification datum which it carriers and a check is then made as to whether the physical structure of the disc complies with that described in the initialization zone. The process applies to the pirate-proofing of any optical disc, especially of CD or DVD format.

Abstract: The disclosure relates to an optical disk of the type including at least one spiral track on which information marks are written in sectors whose addresses are substantially sequential along the track, wherein said disk includes a copy protection zone (PZ) comprising two parts of equal size each including a series of sectors designated by identical addresses on each of the two parts, the data written in this zone being shared between the sectors of the two parts, each sector of the zone also carrying an identifier (D1, D2) characteristic of the part to which the sector belongs, and specific protection data to enable verification of the presence and constitution of said protection zone (PZ) and to enable use of the data written in this zone, at least part of said specific protection data being recorded on said disk. The invention is notably applicable to anti-piracy protection of CD-ROM and DVD-ROM type disks.

Abstract: The information is recorded in the form of variable-length alterations (l.sub.0, l.sub.0 +N.DELTA.l), for example in the form of localized ablations of a thermosensitive layer of the medium. This type of coding of the information is sensitive to imprecisions in the form factor which are due to the non-linearity inherent in the recording method used. The method according to the invention consists in recording marks (M.sub.1, M.sub.2) serving as length reference, from place to place. These marks (M.sub.1, M.sub.2) are recorded at the same time and in the same conditions as the information proper (d.sub.1, d.sub.2, d.sub.3). During the read process, they serve as length references for the associated information area, and after conversion into electrical signals as time reference.

Abstract: The present invention relates to optical memories for storing data on the surface of an information-supporting medium including pre-formatted patterns. Such a memory may constitute a random access mass memory, and it may be read/write memory or it may be a write-once memory. The operations of writing to the memory and reading from the memory are based on the optical interaction which occurs at the point of impact of an incident optical beam which causes local changes in optical characteristics which are representative of the data when data is being written, and which produce optical modulation detectable by photoelectric means during data reading. The invention provides an optical memory in which the illumination mode common to reading data and to detecting pre-formatting patterns is modified in order to allow for operation in a standby mode or in order to delete areas reserved for storing data, for example.

Abstract: A protected optical disc adapted for optical recording and playback of information (particularly digital recording) with a rigid element carrying the recording surface, and a flexible element permeable to optical radiation, one of these two elements having the shape of a dish. At least one of the elements is provided with a central hole for receiving a driving shaft, with the joined annular portion or portions of the two elements concentric with the central hole.

Abstract: The device makes it possible to optically inscribe and/or read at least two facing sides of disks in an optical memory system, whose disks are stacked. A linear motor displaces a mobile means incorporating recording-reading heads. These heads receive via a bidirectional optical connection data to be inscribed and coming from fixed light emitters-receivers. Each of the recording heads comprises two focusing lenses associated with one of the two facing sides of the disk. According to a first variant, the two sides can be read simultaneously, each of the lenses being associated with its own control device. In a second variant, a single control device is provided and the two focusing lenses are integral with one another, each side being read or inscribed in succession.

Abstract: The transmission process comprises a coding of the sound signal consisting of converting it into words of n bits at a frequency double the line frequency and during each synchronization pulse transmitting four words of n bits corresponding to different samples, which introduces a redundancy of two and a decorrelation between the different samples. The process involves a decoding operation consisting of comparing the two representations of the sample transmitted during the two synchronization pulses and selecting one representation for each sample as a function of the result of the comparison.

Abstract: The process according to the invention uses a matrix engraved by any means, the tracks being perfectly centered on this matrix in relation to a center of rotation. The matrix is placed in a vacuum chamber on a supporting axis capable of rotating and is coated over its entire surface with a polymerizable material which is free from air bubbles and which does not adhere to the constituent material of the matrix. A substrate previously drilled at its center, balanced and coated with a material to which the polymerizable material adheres, is placed on the supporting shaft and held at a distance from the matrix. The vacuum is established in the chamber and the substrate is brought into contact with the matrix. On completion of polymerization outside or inside the chamber, the substrate carrying the moulded resin is readily separated from the matrix.

Abstract: The present invention relates to the read-out of a data carrier having a track along which there is transcribed an angularly modulated carrier wave. In accordance with the present invention, there is provided a system for processing the read-out signal, which uses a feedback loop correcting the duty factor of a restored rectangular waveform when its value deviates from the value 0.5.

Abstract: The present invention relates to methods which make it possible to partially eliminate the redundancy in television signals. It consists in splitting the spectrum of the video signal into two parts, one containing the low frequencies, this being transmitted integrally, and the other containing the high frequencies, this being transmitted once every n times and being repeated n-1 times at reception.

Abstract: The present invention relates to the protecting against scratching and fouling of a data carrier which carries a relief impression readable optically by transmission. The data carrier in accordance with the invention is protected by a transparent protective layer with substantially smooth faces, which adheres to the peaks in the relief of the impression in such a way as to prevent the troughs in said relief from being filled up.

Abstract: The present invention relates to the protection of relief impressions formed in order to store information on a data carrier which can be optically read out by transmission. The invention relates to a data carrier the relief impression in which is protected by at least one layer transparent vis-a-vis the read-out radiation. The protective layer has an index of refraction that differs from that of the data carrier, per se. Thus, a refractive boundary at the relief impression is maintained and the information encoded in the diffractive relief pattern is preserved.

Abstract: The present invention relates to an electro-optical converter with storage facility.The converter is constituted essentially by a panel comprising a substrate covered by two dielectric layers, cells containing a gas being made in said substrate and two sets of electrodes arranged on said dielectric layers, one of the dielectric layers being a flexible diaphragm capable of local and permanent deformation under the action of electrostatic forces.The invention is more particularly intended for the recording of optical information.

Abstract: The present invention relates to the dissemination of binary digital data by analogue transmission or storage. The object of the invention is a communication system in which, prior to dissemination, the binary data are grouped into blocks forming vectors with N components, which are transformed into orthogonal vectors with N analogue components; after dissemination, the vectors experience a reverse transformation which makes it possible to reconstitute the binary digital data.

Abstract: The present invention relates to the dissemination of binary digital data by analogue transmission or storage. The object of the invention is a communication system in which, prior to dissemination, the binary data are grouped into blocks forming vectors with N components, which are transformed into orthogonal vectors with N analogue components; after dissemination, the vectors experience a reverse transformation which makes it possible to reconstitute the binary digital data.