| 摘要 |
PURPOSE:To perform a tracking servo favorably by varing a tracking error quantity linearly for a tracking slip. CONSTITUTION:If the regenerative output timing of a clock pit is assumed to be standard, a phase difference between the regenerative output of a phase pit 7 and the regenerative output of the clock pit 5, is setteled at a constant value as phi0 at the time of a just tracking. Then, at the time of a left side slipping it comes to the phase difference phi1, which is smaller than the said phase difference phi0, and at the time of a right side slipping, it comes to be the larger phase difference phi2. Then, by controlling the phase difference between the output of a first phase detecting means 30 and the output of a second phase detection means 40, while considering the phase difference phi0 as a target value, the tracking control of a beam is performed. Thus, the more exact servo can be performed, compared with a case that the servo is operated on the basis of the received light output level from the pit for the servo.
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