| 摘要 |
Tracking servo control of a pickup to an optical card is performed by: obtaining an addition of two tracking error signals detected through respective sub-beam spots, detecting that at least one of the sub-beam spots has met a scratch, etc. from the addition signal, and suspending the tracking servo control while the sub-beam spot is in contact with or located on the scratch, etc. by interrupting a difference error signal and holding a value of the difference error signal just before the interruption.
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