| 摘要 |
PURPOSE:To execute the retrieval at a high speed, by photodetecting a reflected ray from a groovelike guide track by a photodetector, detecting a retrieval crossing direction of the groovelike guide track by a difference signal of an output of the photodetector, a sum signal and a recording and reproducing signal, and counting the number of crossed tracks. CONSTITUTION:In case when the center of a track of a disk 3 is shifted, an optical spot 6 on the disk 3 does not follow a track exactly but crosses the track, and the optical distribution is varied on a photodetector 13. When this variation is detected and is inputted to a predifferential amplifier 19, a tracking difference signal 20 is obtained. This difference signal 20 is inputted to a driving circuit 21 and drives a tracking mirror 4. As for this mirror 4, its angle is varied in accordance with the difference signal so that the optical spot 6 exactly follows the track on the disk 3, and the tracking control is executed. |
