| 摘要 |
PURPOSE:To shorten an access time of a tracking mechanism by giving initial speed nearly equal to track decentering speed of a medium to the tracking mechanism when the tracking mechanism is shifted to track follow-up operation. CONSTITUTION:A displacement detector 8 that detects the amount of displacement of a tracking mechanism 5 to a reference position and a medium eccentricity information detector 9 that detects medium eccentricity information of a track are additionally installed, and when a coarse driving mechanism 4 is being driven, the tracking mechanism 5 is controlled corresponding to the medium eccentricity by the displacement detector 8 and medium eccentricity information detector 9. When driving of the coarse driving mechanism 4 is terminated, controlling signals of the tracking mechanism 5 are switched to the output of a tracking error detecting section 7. Thus, at the time of the coarse driving mechanism 4 is driven, the tracking mechanism 5 is moving, and thereby, relative speed between the tracking mechanism 5 and medium eccentricity becomes relatively small, and necessary time for retraction can be shortened.
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