| 摘要 |
PURPOSE:To switch the operation of a disk turning device smoothly to control based upon an original error detecting signal when focus lock is executed again by controlling the objective number of revolution of the disk to the one obtained immediately before the generation of defocusing when the defocusing is generated during reproducing. CONSTITUTION:A pulse generating circuit 8 generates a sample holding (S/H) pulse and a sample holding (S/H) circuit 7 holds the output of an F/V converter on the basis of the S/H pulse. When a focus servo is unlocked, the generation of the S/H pulse is stopped in accordance with the level change of a focus locking signal. Since the unlocking of the focus servo due to a flaw on the disk surface or the adhesion of dust is executed for an extremely short period, the control of the number of revolution during the period can be attained by using the value obtained immediately before the unlocking.
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