| 摘要 |
PURPOSE:To position a beam spot to an object track by monitoring the pulse width for each one track passing in the track jump state and switching the control to the track tracing control when the pulse width reaches a prescribed value. CONSTITUTION:In case of track jump state, a computer 9 gives a command to a pulse generating circuit 10 to be accelerated in a direction of an object track. Moreover, the computer 9 opens a gate circuit 13 to monitor the moving quantity of the beam spot and the pulse width of a track zero cross signal. Then a pulse width Tw at each one track passing is compared with a value such as Tw'=(Tw1+Tw2), which is a value between the time Tw1 passing through the 1st track and the time Tw2 passing through the 2nd track. In case of Tw>Tw', a switch 12 is changed over, the control is transferred to the track tracing control to position the beam to an object track.
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