Thomson-brandt

Thomson-csf

Roland Malissin

Claude Monlouis

Daniel Lecomte

Gerald Roullet

Jean-Claude Lehureau

Lucien Lainez

An optical head is provided for writing and reading a disk by means of at least one focused beam, the disk being provided with at least one track having uniformly spaced grooves. The optical head makes use of a motor comprising a fixed magnetic circuit provided with at least one air-gap in which a moving system is capable of displacement and is also provided with an access and radial tracking magnetic circuit including at least one core which is secant with all the grooves. The moving system is constituted by two actuators, the first actuator being intended to permit access and radial tracking while the second actuator permits focusing of the light beam on the track, the two actuators being coupled by flexible attachment means. Guiding means comprising magnetic elements permit lifting of the access and radial tracking actuator with respect to the core of its magnetic circuit.

Optical read/write head for recording and playback of an optical disk

The invention provides an optical head for writing-reading a disk by means of at least a focussed radiation. This apparatus has at least one track, this track having evenly spaced apart grooves. An optical head using a motor having a fixed magnetic circuit with an air-gap in which a mobile assembly moves is provided. A magnetic circuit is additionally used which has a magnetic access and radial tracking circuit having at least one core intersecting all the grooves. The mobile assembly is formed of two actuators. The first of these actuators providing access to and radial tracking of the track. The second provides focussing of the light radiation on this track. There is a flexible fixing device connecting together these two actuators, along with a guide comprising friction sliding elements flexibly mounted on the radial and access actuator and allowing the actuator to slide over the core of the magnetic access and radial tracking circuit.

Focusing optical head movable radially by a carriage

The invention relates to a power supply system for a semiconductor light source of which the power is regulated in the steady state by a regulating loop comprising an electronic switching circuit controlled by a signal characteristic of the power emitted by the laser which closes the regulating loop when the output power has reached, a threshold power, a ramp generator supplying a ramp of current to the laser solely from the instant when the feed voltage is established for reaching the threshold.

Power supply system for a semiconductor light source

The invention relates to the detection of the tracking error of a track using a process of periodic excursion of a reading beam in a direction which forms an angle with the direction of exploration of the track. The detection system comprises a mirror deflection by a bar vibrating in a flexural mode which is clamped to a base. Two plates of piezoelectric elements mechanically coupled with said vibrating bar are provided to excite the vibrating plate and to supply a reference signal in constant phase relation with the movement of the vibrating bar.

System for detecting the tracking error in optical readers and recorders

The invention relates to the focusing of an optical system by variation of the radius of curvature of a reflecting element, comprising two prepolarized thin plates of piezoelectric material which are joined together and each of which carries an electrode, the outer surface of one of the two thin plates being made reflective. An electrical signal characteristic of the correction to be made is applied between the two electrodes and produces a variation in the radius of curvature of the thin plates. This reflecting element is used in an optical system of the Cassegrin type or as a reflecting mirror.

Automatic optical focusing device

The invention relates to methods for controlling the starting and stopping of the reading of recording supports read in appropriate readers. The method according to the invention comprises providing a zone free from information at least at the beginning of the track of such a support. The reading head of the reader advances rapidly to that zone and, after having detected the presence thereof, continues its advance at a normal speed.

Head control means for optical videodisc player

A pick-up device particularly suitable for optical read-out of video-frequency discs, comprising a fixed pick-up and a mobile plate, element of which, carrying the recording substrate, is mobile. The transfer of the recording tracks before the pick-up is produced by a rotational movement on the part of the carrier element, in association with a rectilinear displacement d.sub.1 on the part of said carrier element in relation to the fixed pick-up, this displacement being associated with the rotational speed of the carrier element and with the pitch of the recording tracks.

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Paris, France

Roland Malissin