Focus error detecting circuit for disk player

Details Focus error detecting circuit for disk player Focus error detecting circuit for disk player

1989-12-05

1991-02-12

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

369 4441, H01J 4014

Patent

active

049926527

ABSTRACT:
This invention relates to a focusing error detection circuit employed in an optical pickup of an optical disk apparatus or the like. The laser light received from the recording medium is detected by a photodetector and processed in a focusing error computing device to form a first focusing error signal. The first focusing error signal is sampled and held at the timing of periodic turn-off of the laser beam and the sampled-and-held signal is subtracted from the first focusing error signals to produce a second focusing error signal. The second focusing error signal is freed of adverse effects caused by factors, such as temperature changes of the focusing error computing device thereby enabling the accurate focusing servo control of the optical pickup device.

REFERENCES:
patent: 4544838 (1985-10-01), Musha et al.
patent: 4654838 (1987-03-01), Sugiki
patent: 4658391 (1987-04-01), Nozu et al.
patent: 4695158 (1987-09-01), Kotaka et al.
patent: 4744069 (1988-05-01), Sugiyama et al.

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