| 摘要 |
PURPOSE:To measure the eccentricity quantity of a reliable optical disk without any measurement error by inputting a measurement timing signal and a pulse signal and counting pulses of the pulse signal in the output period of the measurement timing signal. CONSTITUTION:A waveform shaping circuit 3 inputs a track error signal and a track sum signal obtained from the reflected light of a light beam projected on the guide groove of the optical disk 1 and outputs the pulse signal (a) which is shaped into a pulse waveform. A rotational position information generating circuit 7 inputs a signal indicating the rotational position of a turntable 9 which rotates mounting the disk 1 and outputs a rotational position information signal (b). A timing circuit 16 inputs the signal (b) and outputs the measurement timing signal (c), which are supplied to an up/down counter 4, which counts pulses of the signals (c). Its output signal (d) of the counted value is A/D-converted 5 into a signal 101 which is proportional to the eccentric displacement quantity of the disk 1. This signal 101 is measured to find the number of tracks corresponding to the maximum amplitude and then the eccentricity quantity is calculated from the number of tracks and previously measured track pitch.
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