Focus acquiring method and optical disk drive

Details Focus acquiring method and optical disk drive Focus acquiring method and optical disk drive

1993-10-19

1995-10-17

Sikes, William L.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

269 54, G11B 700

Patent

active

054593093

ABSTRACT:
The present invention ensures successful focus acquisition in an optical disk drive independent of a travelling speed of an objective lens at the time when a focus servo circuit loop is closed. The present invention provides sending a signal to a focus actuator for bringing an objective lens close to an in-focus position while a focus servo circuit loop is opened; closing the loop by shutting off the signal sent to the focus actuator; adding an offset of a predetermined level to the focus error signal; detecting that the focus error signal to which the offset is added reaches a predetermined level; and closing the loop when it is detected that the predetermined level is reached, and gradually decreasing the value of the offset to be added to the focus error signal.

REFERENCES:
patent: 5233586 (1993-08-01), Morisada
patent: 5289447 (1994-02-01), Kobayashi et al.

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