| 摘要 |
PROBLEM TO BE SOLVED: To accurately discriminate a track pitch without having influence of a time measuring error by moving two tracking control light spots in the track traversing direction and detecting the track traversing of both light spots after traversing of the precedent spot across the track. SOLUTION: The light spots from an optical system 21 are projected to home positions of an optical card C, and are moved in the direction of traversing a track after performing an AF setting operation. Changes of reflected beams of light at the time of track traversing of the two spots arranged apart from each other in the track traversing direction are detected by photodetectors 34 and 36 respectively. When a track pitch is 12μm, the 1st track is detected by the photodetector 36 before the 2nd track is detected by the photodetector 34. When the track pitch is 8μm, the 1st track is detected by the photodetector 36 after detecting first two tracks successively by the photodetector 34.
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