| 摘要 |
PURPOSE:To make it possible to draw in stably servo operation by providing a counter-force generating methof of applying force to a focus lens during a generation period for a fixed control signal and a signal generating method of generating a signal closing a servo loop in an ending period. CONSTITUTION:The output control signal of comparator 20 is inputted to a post- stage differentiating circuit composed of C1 and R3, where it is converted into a signal of differential waveform. Time constants C1 and R3 of this differentiating circuit are so set that the amplitude of signal B will be attenuated gradually in its existence period, and this output C is used as a counter-force generating signal. Control signal B is inputted to a differentiating circuit of C2 and R4, where it is converted into negative trigger pulse D triggering poststage FF. Through resistance R6, the output of FF is inputted to the base of driving transistor Q1, whose base is applied with a voltage of +Vcc via resistance R5 while its collector is with -Vcc through resistance R7, so that the output E will be used as a servo drawing-in assignment signal. Consequently, servo operation can stably be drawn in. |
