Abstract: An optical read system for a disk-shaped record carrier. By means of a tracking system the read spot is centerd at the information track. The control signal for this tracking system is obtained by means of additional radiation spots which are disposed on radially opposite sides of the read spot. By subjecting the detection signals corresponding to these additional radiation spots and the read spot to a special operation a control signal is obtained which is highly independent of variations in disk parameters, variations in the intensity of the radiation beams and focussing errors.

Abstract: An optical read apparatus for a disc-shaped record carrier. The read apparatus comprises an optical read unit which includes a deflection element for controlling the radial position of the scanning spot, for which purpose said deflection element is included in a closed servo control loop. In order to enable a desired program section on the record carrier to be located rapidly, the read unit can be moved in the radial direction. During this movement of the read unit the servo control loop is rendered inoperative each time after the deflection element has reached a preset maximum deflection, after which this deflection element is reset rapidly and the servo control loop is rendered operative again. Thus it is achieved that image reproduction is also maintained during the rapid search for a desired program section.

Abstract: An apparatus is described for reading a flat reflecting record carrier on which information is stored in an optically readable structure, which apparatus, inter alia, includes an objective system for focussing a read beam on the plane of the information structure and a focus detection system which is coupled to an electronic circuit for deriving a control signal for controlling the position of the objective system relative to the plane of the information structure. The electronic circuit is equipped so that the control signal ensures that during locking-in the objective system is moved with a low preferably constant, speed towards the record carrier until the required position is substantially attained, after which the objective system is subject to a high acceleration in the opposite direction.