| 摘要 |
PURPOSE:To enable a motor to rapidly and smoothly reach a reference scanning speed by applying a phase comparison signal of a speed signal and a reference signal to an amplifier of the gain in response to the signal. CONSTITUTION:Since the rotating frequency ff of a motor 21 is lower than the reference frequency fr when a scanning unit starts from its home position, the output of a phase comparator 25 becomes high level H. On the other hand, the LD output of a phase comparator 25 is converted by an integrator 43 into DC becoming high level H at the time of starting scanning, and the output of a comparator 44 becomes low level L, and a changeover switch 40 is connected to an amplifier 28 of high amplification gain. When the rotating speed of the motor 21 reaches the prescribed value, the output of the integrator 43 decreases, the output of the comparator 44 becomes high level H, and the switch 40 is connected to an amplifier 28' of low amplification gain. In this manner, the scanning unit can smoothly reach reference scanning speed. |
