| 摘要 |
A tracking error signal (TE') which is generated by a push-pull method and has an offset component caused by misalignment of the optical axis of the objective resulting from tracking is fed to an offset component extracting circuit (12). The circuit (12) extracts the offset component from the signal (TE'). A holding circuit (13) outputs an offset component (S1) fed from the circuit (12) as it is as an offset component (S2) during a servo-off period based on a servo command signal fed from a system controller (61), holds the offset component (S1) when the servo control is changed from OFF to ON and outputs the offset component (S1) as the offset component (S2). A differential amplifier (14) subtracts the offset component (S2) from the signal (TE') and feeds a tracking error signal (TE) including no offset component (S2) to a tracking control circuit (16). The circuit (16) is provided with, for example, a phase compensating circuit for servo control and drives, for example, the two-shaft device of an optical pickup based on the tracking error signal (TE). Therefore, tracking servo is actuated and the spot of a light beam comes on a track.
|
