| 摘要 |
PURPOSE:To prevent the generation of errors when noises are mixed into a servo device, by changing the servo loop gain after detecting the changing degree of a target. CONSTITUTION:For a tracking servo or focus servo of a video disk and a digital audio disk, an actuator of a pickup PV is driven through a level control amplifier L and an actuator driving amplifier A to the target value O. The error signal detected by a pickup Pu applies negative feedback to an adder circuit ADD1 through a feedback loop, and the servo is applied to always set the target error at O. At the same time, the undesired carrier leakage component of the driving voltage to be applied to the pickup is deleted, and only the component close to the basic wave component such as the disk eccentricity is extracted. For this purpose, the signal corresponding to a level is extracted by a wave detector DE through a filter F. Then the gain of the amplifier L is varied to obtain a gain corresponding to said extracted signal. |
