| 摘要 |
PURPOSE:To prevent effectively track jumps by dividing the band of a tracking error signal at appropriate frequencies and using a signal obtained by cutting off or adding the high band component with the low band component in response to the detection of an excessive inversion cycle as an error signal for control of the tracking error signal. CONSTITUTION:Both an LPF 60 and an HPF 61 have the same time constant and usually add the high and low band components of a tracking error signal. Two binary counter 52 and 53 measure alternately a period during which a bit signal is inverted to a high level, then inverted again to a low level and another period during which the bit signal is set again at a high level from a low level. Then the high range component is cut off by a switch circuit 62 for output of only the low range component in case the inversion cycle of the bit signal exceeds a prescribed level owing to the flaws or a bit omission part on the surface of an optical disk. such a signal is defined as an error signal for control of a tracking error. Thus the tracking error control is never disturbed by said flaws or bit omission part.
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