OPTICAL SCANNING APPARATUS WITH FOCUSSING SYSTEM

摘要

8.8.1979 1 PHN 9486 An apparatus for optically scanning a record carrier, The scanning beam is focussed on said record carrier with the aid of a focussing system. For automatically correcting an incorrect control point of the focussing system the apparatus is provided with a phase detector, to which the focussing errorsignal generated in the focussing system is applied and a signal corresponding to the amplitude of the information signal being read. The output signal supplied by said phase detector is applied to the focussing system as correction signal and automatically performs a correction for an incorrect control point of said focussing system.