| 摘要 |
PROBLEM TO BE SOLVED: To move a light spot to a focus servo pull-in region in a short time. SOLUTION: Level shift quantity Vs is set from the total sum of voltage values of a focus error signal FE, and it is selected by using an output signal (a) of a pull-in range discrimination, an output signal (b) of a comparative circuit, and a polarity discriminating signal whether a region is for performing focus servo pull-in operation or the region is for giving level shift quantity Vs. In the region for performing focus servo pull-in operation, control voltage having reverse polarity to level shift quantity Vs is outputted from a PID compensation circuit 20 to a focus actuator driving circuit 22, force of a direction reverse to force accelerated by level shift quantity Vs is applied to a focus actuator 23, and a target position is attained in a state in which overshoot is small.
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