Optical disc apparatus and method for controlling focus of...

Details Optical disc apparatus and method for controlling focus of... Optical disc apparatus and method for controlling focus of...

2005-09-20

2005-09-20

Allen, Stephone B. (Department: 2878)

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

C369S044250

Reexamination Certificate

active

06946633

ABSTRACT:
A focus error signal which is a differential signal indicative of a difference between a sum of amounts of reflected light detected by photodetector elements A and C of a four-split photodetector, and that of amounts of reflected light detected by photodetector elements B and D is measured. The level of the focus error signal at a timing when the amount of reflected light from the optical disc and detected by the four-split photodetector is at the maximum is set as a reference level. The gains of amplifiers23and24are individually adjusted so that the maximum and minimum values of the focus error signal are substantially symmetrical about the reference level. According to the configuration, the focus control can be performed by using the balance-adjusted focus error signal, and therefore can be stably conducted.

REFERENCES:
patent: 5793720 (1998-08-01), Nishikata
patent: 6295256 (2001-09-01), Kimikawa et al.
patent: 6760285 (2004-07-01), Hirashima et al.
patent: 08-212567 (1996-08-01), None
patent: 2000-276743 (2000-10-01), None
patent: 2000-339704 (2000-12-01), None
patent: 2001-222826 (2001-08-01), None

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