Abstract: A focus controller for a player for rotating optically scanned information-based disks has an optical scanner with a focus actuator driven by a transformer. The loop amplification of the control circuit is controlled in accordance with a control signal that varies inversely as a function of the type and frequency of the disk errors.

Abstract: The invention provides a reader and scanner, in particular for the reading of audio and/or video information recorded on plate-shaped information carriers. A scanning head can be pivoted around an axis in order to provide fine control. The scanning head is maintained in a defined middle position with springs. A magnetic circuit is constructed of a permanent magnet, pole shoes and a coil with a core provides a controllable or automatically controllable movement of the scanning head. The displacement of the scanning head can be determined with a piezoelectric converter, which is disposed between one of the two springs and the support associated with the pole shoes. Desired displacements of the scanning head can be obtained with a second electromechanical converter, which is disposed between the other spring and the other support, after application of a suitable voltage.