| 摘要 |
PURPOSE:To control a light beam to a constant moving speed by providing a speed detecting means which detects the speed when the light beam crosses tracks and a speed control meanswhich controls the speed according to its output signal. CONSTITUTION:The moving speed pattern of the light beam is generated by using a counted value inputted to a polarity switching signal generator 10. This speed pattern becomes the target of the moving speed of the light beam and a pattern like (S) is generated; and the threshold level of the comparator in a signal generator 10 is on the basis of the difference between the target speed signal and relative speed signal. In this case, the light beam moving speed is lower than the target speed, so absolute value of threshold levels Q2 and Q3 decrease and acceleration is required; when the moving speed approximates to the target value, the threshold levels Q2 and Q3 approximate to some constant values. When the moving speed of the light beam reaches the target value, the light beam moving speed is controlled to the constant value.
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