| 摘要 |
PROBLEM TO BE SOLVED: To make a servo operate properly by adjusting a focus bias value by using another element together even when the minimum value of a jitter value is not clear. SOLUTION: A focus servo circuit is provided with a means for picking up a reproduction signal from an optical disk, a means for extracting a focus error signal from the reproduction signal of the pickup means, and a bias setting means giving a bias to the focus error signal. In the focus servo circuit, a bias value to give to the focus error signal is varied by varying the focus balance value, and the jitter value at each focus balance value is measured. When the difference between the maximum value and the minimum value of the measured jitter value is equal to or smaller than a prescribed value, the focus balance value is varied and a tracking error signal value at each focus balance value is measured to set the focus balance value to be a focus balance value where the tracking error signal value is maximum. COPYRIGHT: (C)2005,JPO&NCIPI
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