PURPOSE: To stabilize focus servo operation by reducing the value of focus servo gain lower than the that of normal operation at the time of starting kick back operation and returning the focus servo gain to the original normal value at the time of ending the kick back execution.
CONSTITUTION: When the kick back operation is started, a focus servo control part 10 drops the gain value of a servo gain switching circuit 11 only for the crossing period of an optical head 30 through a track 21 based upon a gain switching signal GCS outputted from a control part. Thereby, the level (expressed by FESd) of a focus error signal FESp is dropped and a focus driving current proportional to the focus error signal FES outputted from the control part 10 is not saturated. Consequently, focus servo control in the kick back operation is stabilized and focus servo control in normal operation such as reading/writing after kick back operation can be stably and effectively executed.
MINAMI AKIRA
TANAKA SHIGEYOSHI
YANAGI SHIGETOMO
SASAKI MASATERU
| JPS5977638A | 1984-05-04 |