| 摘要 |
PURPOSE:To enable a tracking servo circuit to be closed at a time when speed goes to zero in relative travel speed, by providing a speed detecting means capable of detecting the relative speed between a track and an optical spot at the time of traversing in a state where almost no time delay is generated. CONSTITUTION:A signal CT-N from a comparator 11 is decreased according to the travel of an optical head 13 to which a jump command signal CT is inputted, and addressing to a targeted track can be obtained if the tracking servo can be closed at the time when it goes to zero. However, eccentricity >=100mum exists in a disk generally, and it is difficult to apply tracking servo at this time. Hereupon, the motion of a head 13 is controlled by returning a speed signal detected by a speed detection circuit 15 at the time when the displacement error signal CT-N outputted from the comparator 11 is decreased to the optical head 13 via a distributor 12, a coefficient circuit K1, and an adder 17. Thus, the switch SW of the circuit 10 is turned ON at the time when the speed signal goes to zero, and the tracking servo is locked immediately, then, fast access can be obtained.
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