apparatus for avlesning of a plan, reflecting uppteckningsberare, what information you stored in an optical lesbar structure

摘要

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.