| 摘要 |
PROBLEM TO BE SOLVED: To precisely detect the amount of disk tilts without using a tilt sensor. SOLUTION: The amount of the disk tilts is detected based on the asymmetry between an upper and a lower wobble signals included in the output RF difference signal of an optical pickup 5 or based on the symmetry in amplitude of an upper and a lower land prepit signals included in the output RF difference signal. Further, the amount of the disk tilts is detected by the evaluation of the symmetry in the upper peak and lower peak values of the output RF difference signal.
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