Abstract: The magnetic recording device with rotating head according to the invention comprises a magnetic recording medium, a cylindrical and rotating head, a fixed magnetic excitation circuit; the head comprising, on its surface, two movable pole pieces separated by a gap and each magnetically linked to an initial and a second magnetic circuit in the shape of a portion of a ring and providing a rotating joint to the passage of the magnetic flux, with the fixed, magnetic excitation circuit possessing an excitation coil that induces an magnetic field in a magnetic circuit having two fixed pole pieces, each magnetically coupled by a gap to one of the said rings.Application: Video tape recorders in particular.

Abstract: 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.

Abstract: 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.

Abstract: 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.