| 摘要 |
PROBLEM TO BE SOLVED: To attain a high density of an optical disk by obtaining a tangential skew amount based on a focus actuator drive signal for focus servo outputted from a focus servo circuit. SOLUTION: N pieces of data of the focus actuator drive signal S1 are sampled every revolution during M times of revolution. Thus, N×M pieces of data are sampled by a sampling circuit 24 as a whole to be stored in a storage means 25. A D/A conversion circuit 28 converts a differenceΔy detected from an inputted digital signal by a difference detection means 27 to a tangential skew error signal. An averaging means 26 reads out the data stored in the storage means 25 to average them. Then, by averaging M pieces of data, a random high frequency noise component is suppressed, and the precise data are obtained.
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