| 摘要 |
PURPOSE:To reduce noises mixed in a tracking error signal due to the hurt or dirt on the surface of a transparent protective layer for a disc by removing low- frequency components with much noise from a differential error signal by filters and then AM-demodulating the filtered signals to obtain the tracking error signal. CONSTITUTION:High-pass filters 20a, 20b remove low-frequency components from a differential error signal respectively and then AM demodulators 21a, 21b AM- demodulate the filtered signals, respectively. The frequency of the AM demodulators 21a, 21b is set higher than the cutoff frequency of the high-pass filters 20a, 20b. The high-pass filters 20a, 20b, the AM demodulators 21a, 21b and a differential amplifier 5 constitute an error detecting means, and a compensating circuit 6, a driving circuit 7 and an actuator 8 constitute a tracking controlling means. Said constitution of the tracking controlling means makes it possible to reduce the disturbance of tracking control which may be generated by the hurt or dirt of the surface of the transparent protective layer of the disc. |
