| 摘要 |
PROBLEM TO BE SOLVED: To obtain a tracking error signal having a sufficient amplitude even when a track pitch changes. SOLUTION: A main spot SPm and side spots SPs1 and SPs2 are formed on a disk 101. When treating the disk 101 whose track pitches Tp are 1.6μm and 1.07μm, the spots SPs1 and SPs2 are formed at positions separated with a distance shorter than 1.6/2μm and longer than 1.07/2μm in the radial direction relative to the spot SPm. For example, in the disk 101 whose track pitch Tp is 1.3μm, the spots SPs1 and SPs2 are formed at positions corresponding to the track pitch Tp. In both disks 101 whose Tp(s) are 1.6μm and 1.07μm, the tracking error signal STE by a DPP method can be obtained with a sufficient amplitude. Thereby, the disk 101 whose Tp(s) are 1.6μm and 1.07μm can be treated without changing an optical system.
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