| 摘要 |
PROBLEM TO BE SOLVED: To provide a disk playback device properly determining a disk type. SOLUTION: Semiconductors 11 (11a to 11c), photodiodes 20 (20a to 20c), APC circuits 21 (21a to 21c), and control circuits 22 (22a to 22c) are independently operated. Up-sweeping is carried out at a fixed speed while simultaneously emitting 3-wavelength laser beams for CD, DVD and BD. Depending on the time from the start to acquisition of a reflected light, the type of a disk D is determined. In other words, since focus up-searching is carried out by simultaneously emitting 3-wavelength laser beams, for any type of the disk D, at least a reflected light of a corresponding wavelength laser beam is surely obtained. COPYRIGHT: (C)2008,JPO&INPIT
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