| 摘要 |
PURPOSE:To retrieve a desired track at high speed by shifting the irradiated position of a light spot in response to the difference between the address signal of the track irradiated by the light spot and the address signal corresponding to the desired track and positioning the light spot to the desired track. CONSTITUTION:A comparator 22 compares the output of a block counter 20 with the output of a target block number register 21. When the coincidence is obtained between both outputs, a signal is sent to a driving circuit 17 to shown the coincidence of track groups. The signal applies the mechanical brakes to a shift device 16 and the device 16 is stopped within a target track group. While the address detected by an address detecting circuit 25 is compared with the output of a target address register 26 by a comparator 27. Then the signal proportional to the difference obtained from the comparator 27 is supplied to a jump control circuit 29 to drive the galvanomirror of a reproduction optical system. Thus a light spot 8 is jumped up to the track where a target address is recorded and the desired information is read out.
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