| 摘要 |
PROBLEM TO BE SOLVED: To improve reliability of the device by arranging it so that a control process based on more accurate and stable middle point error signal is executed. SOLUTION: At first, an eccentricity amount (x) of a disk is detected to obtain an amplitude Vp-p of a middle point error signal appearing at one revolution cycle of the disk. And, sensitivity Ers of the middle point error signal is obtained by executing an operation processing of Ers=Vp-p/x [V/μm] on the eccentricity amount (x) and the amplitude Vp-p of the middle point error signal. And, based on the sensitivity Ers of this middle point error signal, the transition amount of an actual object lens corresponding to the level of the middle point error signal is obtained and this is used for a necessary control processing.
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