Abstract: An apparatus is described for reading a radiation-reflecting record carrier on which information is stored in an optically readable track-shaped phase structure. The apparatus inter alia includes a radiation source, an objective system and a radiation-sensitive detection system. By a suitable arrangement and a suitable choice of the power of a cylindrical lens, which lens in conjunction with a four-quadrant detector supplies a focussing signal, it is possible to detect centering-errors with the aid of only two additional detectors in the plane of the four-quadrant detector.

Abstract: An apparatus is described for reading a record carrier on which information is stored in an optically readable structure. Between a radiation source and an objective system a mirror system is disposed, by means of which the entrance pupil of the objective lens can be imaged onto beam-controlling elements which deflect the read beam over the information structure.

Abstract: An apparatus is described for reading a record carrier on which information is stored in an optically readable structure. Between a radiation source and an objective system, a polarization-sensitive beam splitter and a .lambda./4 plate are disposed. The optic axis of the .lambda./4 plate is perpendicular to the end faces, so that the plate may be thick and may be rotated in its own plane.