Quality testing of optical discs - having laser intensity and amplifier gains varied during test cycle

摘要

A solid state laser (4) generates an output that is passed through a semi-reflecting mirror (6) and onto a lens system (7) that focusses the beam onto the surface of an optical disc (8). The signals reflected back from the surface are directed by the mirror onto a detector (11), coupled to an HF amplifier circuit (12). The signal is demodulated (13) and a test unit (2) evaluates the quality of the read information. A regulating state (15) receives an input to control the intensity of the laser beam, with the gain of both amplifiers (12,14) being also increased during testing. ADVANTAGE - Improved testing of optical discs.