Optical scanning system for laser discs - controls laser beam deflection by acousto=optical unit, that has frequency varied w.r.t. feedback from signal reflected back from disc

摘要

The optical scanner passes the output of a laser (31) through a collimator (32) to be received by an acousto-optical deflection (41) coupled to a control unit (42). The beam is received by a splitter (51) and the transmitted signal is focussed (52) onto the surface of the disc (70). The signal reflected back from the disc has a component directed onto an optical detector (60) providing feedback to the acousto-optical deflector controller (42). This controls the ultrasonic frequency dependent upon the required access position. ADVANTAGE - Reduced access time, improved accuracy of locations. Tracking accuracy is increased and is unaffected by external vibrations. Increased compactness.