| 摘要 |
PROBLEM TO BE SOLVED: To realize stable tracking control by obtaining a tracking error signal of a fixed amplitude level even when phases of optical detection signals of two sub-beams for a main beam are changed. SOLUTION: This tracking signal generating device is provided with a middle signal generation part generating difference signals Sa, Sb as two middle signals from three position signals Sm, Ss1 and Ss2 according to positional relations among three light beams and tracks and a signal synthetic circuit 412 synthesizing a zero cross tracking signal from the difference signals, Sa, Sb at the optional phase with the tracks, and decides gains of variable gain amplifiers 501, 502 in the middle signal generation part so that the difference signals Sa and Sb whose phase is different by 90 degree in the track traverse direction, become equal amplitude.
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