| 摘要 |
PROBLEM TO BE SOLVED: To permit simple wiring and circuit system by making opposite phases a wobble signal obtained from a main spot on an optical disk for adjustment and a wobble signal obtained from sub spots before and after the main spot, and making reverse phases a push-pull signal obtained from the main spot and a push-pull signal obtained from the sub spots. SOLUTION: A state in which three light spots trace an equal track is made sure in a first process. A wobble signal is used a this time. A grating is set to a predetermined angle of rotation in a second process, and a push-pull signal is used at this time. A sum signal SPPwo of preceding and succeeding wobble signals has a phase of -180 deg.C which is a reverse phae of a phase difference of 180 deg. to a wobble signal PPwo reproduced by a main beam. In the second process, phases of the push-pull signal by the main spot and push-pull signal by a sub spot are made opposite.
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