Disclosed is a radiant energy optoelectronic position monitor system which detects the angular position of a "galvanometer mirror" (beam scanner) used in an optical disk memory arrangement. Using a single infra-red monitor beam, angular motion is converted to linear displacement of an image on a detector...http://www.google.de/patents/US4466088?utm_source=gb-gplus-sharePatent US4466088 - Galvo position sensor for track selection in optical data disk system
