| 摘要 |
PURPOSE:To make an effective aperture follow precisely a set diaphragm by superposing a high frequency preventing approximately the exposure from the influence of the amplitude of vibration to the DC output of an electrostrictive element generated by applied DC voltage. CONSTITUTION:A variable resistor 10a connected to a DC voltage source 10 interlocks with a diaphragm not shown in the drawing, its voltage dividing ratio is fixed and the output from the variable resistor 10a is amplified by a buffer amplifier 12a to drive the electrostrictive element 1. A high frequency generator 11 generates a bias voltage and applies its output to the electrostrictive element 1 through a buffer amplifier 12b. If the variable resistor 10 is reduced from the DC voltage corresponding to a diaphragm F2 to that corresponding to diaphragms F5.6, the voltage is dropped stepwise, because high frequency voltage is superposed to the voltage in spite of the linear drop of the DC voltage. Consequently, the electrostrictive element 1 executes histeresislike vibration. Thus, the effective aperture of the diaphragm is made to follow precisely the set diaphragm independently of the changing direction of the diaphragm or its quantity of change. |
