Tracking controller for correcting a tracking error offset

摘要

A galvano-mirror recorder for moving the light beam in a circular pattern applied to a disk is rotated by a driving circuit. A track error signal is obtained from an output of a photosensor for detecting a deviation of a light beam applied position from a track on the disk. To detect a rotation angle when rotating the galvano-mirror recorder with a photosensor and cancel an offset generated due to rotation of the galvano-mirror recorder in accordance with the detected rotation angle, a differential amplifier for correcting the track error signal is used to correct the offset of the track error signal due to rotation. Moreover, in the case of retrieval of the tracks on the disk, the output of a phase compensation circuit for phase-compensating the sum of the output of a low-pass filter in accordance with the output of the photosensor and the output of a DC cut filter in accordance with the output of the photosensor is returned to the negative input terminal for driving the galvano-mirror recorder to lock the galvano-mirror recorder so that the center of a light spot is aligned with the center of the optical axis of an optical system even if a disturbance occurs.