| 摘要 |
PURPOSE:To prevent disabled tracking by providing a count means counting the number of times of code error detection and a control means controlling a loop gain of a focusing device a pickup reproducing digital information or that of a tracing device to a recording medium face. CONSTITUTION:A signal reproduced by an optical pickup 2 is converted into a digital signal by a preamplifier circuit 4 and a waveform shaping circuit 5, a clock component is extracted further by a clock recovery circuit 6 and a signal subject to an EFM modulation is demodulated by an EFA demodulation circuit 7 and the result is inputted to an error detection and correction circuit 8. The error detection and correction circuit 8 detects and corrects an error in the EFM demodulation signal in the unit of one information frame and outputs one pulse as error information when >1 code error in one information frame. The pulse of the error information is counted by a microcomputer 14 in the unit of, e.g., 1sec and the mean value in the unit of 10sec is obtained. Then flaws or dirt of the recording medium are detected surely independently of the kind to prevent tracking defect.
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