| 摘要 |
PURPOSE:To abolish a rotational speed detecting means for a rotor and to miniaturize a device and to reduce the device in weight by performing low-speed inching control over a motor which drives an optical quantity control member with a driving control signal obtained by adding a continuous pulse waveform having a shorter period than the time constant of the motor to an optical quantity control signal. CONSTITUTION:The device is provided with a pulse generating means 8 which generates the pulse output having the shorter continuous period than the time constant of the motor and an adding means 9 adds its output to the optical quantity control signal P0 90 and sends its output to a power amplifier 10 for motor driving to drive the motor on an inching basis. Namely, the voltage applied to the driving coil 12 of the motor are in a pulsating shape and the rotor 13 of the motor rotates is in fine switching rotation at all times, so the rotor 13 stops immediately by stopping the application of a controlled variable error signal to the driving coil 12, so the momentum and stop position of the optical quantity adjusting member such as an aperture blade can be controlled with high accuracy. Consequently, the need for a damping coil for speed detection is eliminated and the device is miniaturized and reduced in weight. |
