Optical disc recording and playback unit - has laser controlled by detector circuit to limit amount of light within period

摘要

The optical disc recording/playback system has the disc (1) driven by a motor under control of signals from a drive circuit (3) coupled to a main controller (4). The disc is accessed by an optical head (5) that has a laser (6), lens (7), beam splitter (8), focussing lens (9), photodetector (11) and photodiode (12). The light intensity of the laser is monitored by the photo detector (12) and this provides an input to the laser control circuit (15) which operates to regulate the intensity. Coupled to the circuit is a unit (16) that inhibits the supply relay (17) when the lighting amount within a period exceeds a set limit. ADVANTAGE - Inhibition circuit limits amount of laser light in set period.