| 摘要 |
PROBLEM TO BE SOLVED: To generate correct track cross pulses even when seeked at a high- speed and improve control efficiency by passing a signal obtained by moving a pickup in a radial direction of an optical disk, through a band pass filter having a variable center frequency, binarizing the signal, obtaining the track cross pulse, and making the center frequency of the band pass filter track a frequency of the track cross pulse. SOLUTION: A digital band pass filter 12 is constituted of a shift register having a variable delay time, and has, e.g. a frequency band of±1 kHz. The digital band pass filter emphasizes a basic wave component of a digital tracking error signal received from a tracking error detection circuit 11 and sends a binarized track cross pulse to a seek control circuit 4 through a hysteresis comparator 13. An average value circuit 14 receiving an output of the hysteresis comparator 13 calculates a center frequency from an average time whereby track cross pulses of a constant count are counted, thereby controlling a center frequency of the digital band bass filter 12 with the center frequency.
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