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: The optical head in the recording-reading device of a data carrier comprises a semiconductor laser source. A lens makes it possible to focus the beam from this source on to the data carrier via a reflecting or deviating mirror. According to the invention the rotation axis of this mirror is in the plane of the entrance pupil and of the focus of the focusing lens.

Abstract: An optical head is provided for an information carrier recording-reading device. Such an optical head comprises a pivoting mirror for reflecting the light towards the data carrier. According to the invention, this pivoting mirror is mounted on a pivoting seat having a sliding surface and resting on the sliding surface of the cradle shaped base. Said mirror is mounted on the seat so that the center of curvature of the sliding surfaces is in the reflecting plane of the mirror. Adjustment of the orientation of the mirror is thus made easy.

Abstract: The optical head in the recording - reading device of a data carrier comprises a semiconductor laser source. A lens makes it possible to focus the beam from this source on to the data carrier via a reflecting or deviating mirror. According to the invention the rotation axis of this mirror is in the plane of the entrance pupil and of the focus of the focusing lens.

Abstract: The optical head in a data carrier recording-reading device comprises a semiconductor laser source. A lens makes it possible to focus the beam from this source. A polarization beam splitter makes it possible to deflect the beam reflected by this carrier towards a group of photodetectors. According to the invention the splitter is an isosceles prism, which serves as an anamorphotic-splitting means. A quarter-wave plate is bonded to one of the faces of the prism. A planoconvex lens can also be bonded to the other face of the prism upstream of the photodetector.

Abstract: An optical device for forming a stigmatic image of a laser source positioned at a predetermined point is intended to illuminate a reflecting surface while also providing a separation between the beam emerging from the source and the beam reflected from the surface. The device comprises a cube placed against a converging lens, the dimensions of the assembly thus formed being such that the cube face remote from the lens passes through a Weierstrass point of the spherical refracting surface formed by the lens. The laser source is positioned at the Weierstrass point. The cube is formed by two prisms cemented together, the interface being treated so as to have a polarization-separating effect.