Focus servo-circuit with ordered reference level setting means

Details Focus servo-circuit with ordered reference level setting means Focus servo-circuit with ordered reference level setting means

1987-08-24

1988-11-22

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

369 45, G01J 120

Patent

active

047867949

ABSTRACT:
In order to focus light beams which are projected onto an optical recording medium, the focusing optical system is moved in a vertical direction to the surface of the recording medium. A focus error signal produced by receiving the light returning from the recording medium is compared in turn with a predetermined plurality of reference levels. A focus servo-means is operated when this signal reaches the reference level within the focus pull-in region after passing through a predetermined order of reference levels.

REFERENCES:
patent: 4446546 (1984-05-01), Miller
patent: 4541084 (1987-09-01), Oku et al.
patent: 4544837 (1987-10-01), Tanaka et al.

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