| 摘要 |
PROBLEM TO BE SOLVED: To successfully perform tracking and track counting by generating an objective lens movement detection signal at the time of track jump, and canceling direct current fluctuation of a push pull signal by an objective lens movement detection signal. SOLUTION: Time constants of a top hold circuit 104 for detecting a top level St and a bottom level Sb of the push pull signal and peak hold circuit 106 are controlled by a time constant control signal. The phase inverted push pull signal is inputted to the peak hold circuit 106. A signal St indicating a top level and a signal Sb indicating a bottom level are added, halved and averaged out is made an objective lens movement detection signal Sd. A tracking error signal is formed by subtracting the objective lens movement detection signal Sd from the push pull signal. The time constant is controlled corresponding to inclination of the direct current level fluctuation of the push pull signal Sp. COPYRIGHT: (C)2005,JPO&NCIPI
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