Electronic shutter apparatus for cameras

Claim 1

An electronic shutter apparatus for cameras, comprising an electromagnet for holding shutter blades at their opened position when the electromagnet is energized; a photoelectric single pulse generating circuit for generating single pulses by the initial part of action of a shutter release button, said single pulse having a pulse width inversely proportioned to the brightness of the object to be photographed; a standard clock pulse generating circuit for generating continuous CLOCK pulses each having a constant frequency; a trigger pulse generating circuit containing a trigger switch actuated by the shutter when this shutter is released by the advanced action of the shutter release button and generating trigger pulses by this trigger switch; a first AND circuit connected to said photo electric single pulse generating circuit and also to said standard clock pulse generating circuit to pass therethrough the input CLOCK pulses throughout the inputting period of the photoelectric single pulses; a second AND circuit connected to said standard clock pulse generating circuit and also to said trigger pulse generating circuit to pass therethrough the input CLOCK pulses throughout the inputting period of the trigger pulses; a first counter circuit connected to the output side of said first AND circuit and containing output stages for dividing the frequency of the CLOCK pulses having passed through said first AND circuit and for memorizing the resulting CLOCK pulses; a second counter circuit connected to the output side of said second AND circuit and containing output stages for dividing the frequency of the CLOCK pulses having passed through said second AND circuit and for reading-out the resulting CLOCK pulses; binary counters respectively corresponding with each other in said respective output stage of said first and second counter circuits; a detecting circuit for detecting the coincidence of the number of pulses; an RS flipflop circuit having a reset input terminal connected to the output terminal of said detecting circuit and having a set input terminal connected to said photoelectric single pulse generating circuit; and a transistor to said RS flip-flop circuit and having said electromagnet controlling the shutter at the time when said detecting circuit generated its output, and containing said electromagnet adapted to be released of its energized state by the output of said coincidence circuit, whereby the shutter is adapted to be closed when the numerical value indicating the brightness of the object to be photographed and having been memorized period to photographing coincides with the numerical value of same at the time of actual photographing.