Diaphragm control circuit for camera

Claim 1

A diaphragm control circuit for a camera, comprising a stepping motor interlocked with a diaphragm mechanism of a camera to allow the latter to establish a diaphragm aperture in accordance with an angle of rotation thereof, a clock pulse generator for producing a drive pulse which enables said motor to be rotated either in a forward or reverse direction, a motor energization distributor for distributing said drive pulse to a plurality of exciting coils of said motor, a release circuit responsive to a shutter release operation for producing a release signal which causes said motor to rotate in reverse to return said motor to its initial position, a direction of rotation command circuit for controlling the direction in which said motor is rotated by applying a direction command signal to a direction command terminal of said distributor, said command circuit being responsive to said release signal to cause said motor to rotate in reverse, a reset means responsive to said release signal for applying a reset signal to said command circuit by detecting that said motor has been rotated in reverse stepwise to its initial position, said command circuit causing said motor to rotate in a forward direction in response to said reset signal, a diaphragm presetting circuit responsive to said reset signal for allowing said drive pulse to be fed to a pulse input terminal of said distributor for a time duration which corresponds to the amount of light reflected by an object being photographed, and a shutter drive circuit for causing a shutter to be released after a desired diaphragm aperture has been set as a result of a forward rotation of said stepping motor in response to the application of said drive pulse thereto through said distributor for said duration.