Abstract: The present invention relates to various improvements to a device for access and tracking to a track carried by an information medium, the information being readable and/or recordable optically by a focused radiation, this track forming, on the medium, regularly-spaced or variably spaced revolutions, the revolutions forming a spiral or having the form of concentric circular elements, the device comprising an optical head (1) with optical axis A orthogonal to the plane of the medium, a fixed magnetic circuit comprising at least one core (7) secant to the set of revolutions of the track, in the gap of which two coils (14, 15) move permitting respectively track access and radial tracking to be achieved, as well as focusing of the radiation onto the track, the optical head and the two coils being fixed rigidly to one another in such a way as to form a single compact mobile unit.

Abstract: A control device for servocontrolling an object to a given position includes a motor, a coder connected to the motor, and a rig connected to the coder and the motor, the rig including (a) a counter and a subtractor which generate a position discrepancy signal on the basis of an output of the coder and an external set-point signal input to the subcontractor; (b) circuit paths each having a sampling device which receives the position discrepancy signal and samples this signal at a distinct frequency, each circuit path performing a different degree of differentiation; (c) a summing unit for receiving and summing outputs of each of the circuit paths; and (d) an amplifier for receiving an output of the summing unit and outputting a control signal which controls the motor.

Abstract: A mobile optically-readable data medium, arranged in the form of a set of tracks having a sampled type format, each track having pre-engraved zones, known as pre-format zones, and zones reserved for user data, access to said tracks being obtained using pre-engraved marks, known as access marks, representing on each track at least one part of the address of the latter. This medium has no specific radial tracking marks. A reading device for information engraved on the surface of a medium such as that described above; this device performs the radial tracking using information read from the access marks. The invention applies to digital optical disks.

Abstract: A device for accessing and following tracks on a surface of mobile media on which data is optically readable and writable by a laser beam. The device includes at least one optical head made of a rigid carriage which enables a laser beam (F) to access the track. A lens is rigidly linked to the rigid carriage (3) and focuses the laser beam on the surface of the mobile data medium. A return mirror is rigidly linked to the rigid carriage to direct the laser beam towards the lens. At least one motor coil allows movements of the carriage to focus the laser beam. A mirror which is not fixed to the optical head allows the laser beam to be directed towards the optical head, and a motor coil allows the mirror to pivot. Also means are provided for detecting and correcting any decentering of the beam in relation to the axis perpendicular to the plane of a pupil of the lens and passing through its center.

Abstract: Disclosed is a device for access to and follower control of a track of an optical disk. This device has an optical head with an axis orthogonal to the plane of the disk, at least one fixed magnetic circuit comprising a core that is secant with all the turns of the track, the gap of which forms a plane that is substantially perpendicular to the support, a first motor device allowing for the access to and radial tracking of the track formed by at least one first coil mounted so that it moves on the core of the magnetic circuit and a second motor device that enables the focusing of the radiation on the track consisting of a second coil cooperating with a magnetic circuit. The optical head, the coil of the first motor device and the coil of the second motor device are rigidly fixed to one another so as to form a single compact moving element that moves in the gaps of the magnetic circuits. The disclosed device can be applied to digital optical disks.

Abstract: A disk player-recorder for cartridge disks, the cartridge including a disk mounted in a housing, the player-recorder having a frame which includes an aperture for insertion of the cartridge, a mechanism to set the cartridge to the play and/or record position and a mechanism for transporting the cartridge between the aperture and the cartridge positioning mechanism and vice-versa. The cartridge transport mechanism includes a cartridge support mounted on a player-recorder frame by a pivoting parallelogram system and a mechanism for moving the support with a virtually sinusoidal motion between the aperture and the positioning mechanism.