| 摘要 |
PURPOSE:To improve the recovery response at the missing of information data by retarding a tracking error signal at the preceding beam at a detection signal amplifier circuit to apply phase adjustment thereby eliminating out-of-tracking even to a black-dot form disk defect. CONSTITUTION:A delay is provided to a detection signal amplifier 1 means for a preceding sub beam spot. In inputting sub beam spots 102, 103 to sub beam spot detectors 4, 5 respectively, since the sub beam 102 corresponds to the preceding sub beam at the head in the disk turning direction, the output phase of the detection signal amplifier 2 is adjusted. In selecting a time delay element 6 as C=330pF, R=160kOMEGA and R1=R2=160kOMEGA, the radial resistance due to a flaw on the disk, that is, the trace distance of the objective lens by a radiated beam with respect to a black dot of no reflection (the size is 800mum) is -0.3mm, +0.3mm, the interruption of the flaw for irregular reflection is -0.35mm, +0.35mm, and the both are nearly the same values. Thus, the phase difference between the sub beam spots goes to almost zero.
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