| 摘要 |
PURPOSE:To perform leading-in operation stably in a short time by driving a light spot according to a detected speed at which the light spot scans across tracks, and detecting when the detected speed decreases below a specific value and generating a timing signal for closing a tracking servo loop. CONSTITUTION:The movement 10 of a track and the movement 11 of the spot are supplied to a track shift detection part 12, which detects their position shift optically and outputs a track shift signal 7. This signal 7 is inputted to a switch circuit 13, which is controlled with a servo ON timing signal 14; and the output of the switch circuit 13 drives an actuator 17 through a compensation system 15 and an actuator driving part 16 to position the light spot. The servo ON timing signal 14 which controls the operation of a tracking servo system is outputted by detecting the timing of stable leading-in operation by using the track shift signal 7 and a total light quantity signal 6 through a control circuit 19 which is actuated with a tracking ON signal 18 commanded by a host control circuit so that tracking is carried out.
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