Focus control device in optical recording and reproducing appara

Details Focus control device in optical recording and reproducing appara Focus control device in optical recording and reproducing appara

1993-04-30

1994-10-04

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

369 4441, G01J 120

Patent

active

053528816

ABSTRACT:
A focus control device for an optical head in an optical recording and reproducing apparatus for optically performing recording/reproducing. The focus control device includes an optical detector having a plurality of optical detecting sections for detecting reflected light of an optical beam irradiated to an optical recording medium, an error-signal generating circuit for generating a focus error signal on the basis of an output from the optical detector, and a focus regulating mechanism for regulating a focusing state on a surface of an optical recording medium of the optical beam on the basis of a focus error signal. The focus control device further includes a pseudo-focus-error-signal generating circuit which generates a pseudo focus error signal of a predetermined level for bringing back the focusing point of the optical beam to the control target position. The focus control device further includes an error signal selecting circuit for selectively switching an error signal supplied to the focus regulating mechanism such that a pseudo focus error signal is outputted in place of the focus error signal of an output from the error-signal generating circuit when the focusing point of the optical beam is shifted by a predetermined quantity from the control target position.

REFERENCES:
patent: 5070491 (1991-12-01), Horie
patent: 5107101 (1992-04-01), Ando
patent: 5157249 (1992-10-01), Hashimoto et al.
patent: 5189293 (1993-02-01), Leenknegt

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