| 摘要 |
PURPOSE:To hold a diaphragm in an open aperture state securely with less power consumption by releasing a stepping motor with self-holding ability for aperture control from being powdered on detecting the diaphragm being in an open state. CONSTITUTION:When a stepping motor SM is driven by the stepping motor driving circuit DR consisting of multistage flip-flops DF1-DF4 to make an aperture AP open, a switch SW9 is turned on. Then, AND gates A6 and A20 are closed by a low-level signal passed through the switch SW9 to stop driving clock supply to the circuit DR, and consequently while the motor SM is powdered off, a holding coil W is also powdered off. Then, the moment when the aperture AP is stopped down by oscillation, etc., and the switch SW9 is turned off, the motor SM holds itself by feeding electricity to the coil W, and if the aperture AP is stopped down to another value owing to abrupt oscillation, the gate A6 is opened to obtain an open aperture again. Thus, the open aperture state is held securely with less power consumption only by necessary power supply. |
