Optical pick=up for disc systems - has reflected signals separated into polarised components for precise track control

摘要

A laser (1) generates an output that is transmitted through a collimator lens (2), halfwave plate (3) and a beam splitter (4) to allow the beam to be focussed (5) onto the disc (15). The signals reflected back fromt he disc are directed by the beam splitter through a halfwave plate onto a second splitter (7). This produces two polarisation components that are each received by cylinder lenses (8,9,11,12). Quadrant detectors (10,13) provide signals that can be processed for automatic adjustment of focussing and track alignment. ADVANTAGE - Improved track location.