| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical disk apparatus which determines where the focus position of a laser beam exists in a plularity of recording layers by using changes (history) of a focus drive signal and a focus error signal. SOLUTION: This optical disk apparatus is provided with: a pickup part 15 for outputting a reading signal by irradiating an optical disk having the plurality of recording layers L0, L1 with a laser beam; an RF amplifier part 12 for outputting the focus error signal from a reading signal; focus control parts 37, 21 for adjusting focus of the laser beam based on the focus drive signal and the focus error signal; a holding part 53 for holding variation of the focus error signal and the focus drive signal as history information; and a judging part 36 judging a focus position out of the plurality of recording layer of the optical disk, using the history information of the detected the focus error signal and the focus drive signal. COPYRIGHT: (C)2006,JPO&NCIPI
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