| 摘要 |
PURPOSE:To prevent overrun of a pickup even during disturbed servo control by detecting a track pulse erasure over a prescribed time or over and applying inhibition of track jump and countermeasure of focus servo means fault. CONSTITUTION:Track jump of a disk 7 is applied by a light spot by a pickup 1 to retrieve the address. Then a tracking error signal from an RF amplifier 15 is fed to a tracking servo circuit 19 and a focus servo circuit 18 and a track pulse is generated corresponding to the track jump from a track pulse generating circuit 20 based on the level change in the tracking error signal. When the loss of the track pulse over a prescribed period is detected, the processor of the controller 21 applies out of focus to stop the track jump and the focusing abnormity processing by the circuit 18 is applied to restart the track jump after the end of focus control and the pickup overrun even at the occurrence of disturbance in the focus servo control is prevented.
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