Electronic shutter for photographic camera equipped with exposure condition checking circuit and exposure time control circuit

Claim 1

An electronic shutter for a photographic camera cOmprising: A. an exposure-time control circuit comprising: A1. a delay circuit consisting of a photo-conductive element and a capacitor, A2. a switching transistor circuit connected to be operated via said delay circuit, A3. an electromagnet connected to an output terminal of said switching transistor circuit for controlling the time for starting to close a shutter blade, B. shutter-driving means for opening and closing the shutter blade, C. manually operated release means having a non-operated position, a first operated position, and a second operated position occurring after the first position has been passed, D. first power switch means associated with said release means for opening and closing said exposure time control circuit and being closed when the shutter blade is opened and then being held in its closed condition by said shutter driving mechanism until the closing of the shutter blade, E. a first resistor selectively connectable in series with said photoconductive element for warning of possible danger from shaking the camera, F. a second resistor selectively connectable in series with said photoconductive element for warning of danger of over-exposure, G. a first lamp connected to said switching transistor circuit for warning of possible danger from shaking of the camera, H. a second lamp connected to said switching transistor circuit for warning of danger from over-exposure, I. second power switch means for checking exposure conditions, connected in parallel with said first power switch means and arranged to be closed during the initial stage of the releasing operation of said release means and to be opened upon the freeing of the releasing operation, J. a first checking switch means for checking exposure conditions and being operable to sequentially connect with said first and second resistors by the operation of said release means upon the closing of said first power switch means, K. a second checking switch means for checking exposure conditions operable simultaneously with said first switch means and sequentially connectable with said first and second lamps, L. a first changeover switch means adapted to switch a circuit including said first and second resistors and said first switch means to a circuit including said capacitor by the release means after the operation of said two switch means has been completed but before said shutter driving mechanism is released, whereby this state is retained by said shutter driving mechanism until the closing of said shutter blade, and M. a second changeover switch means operable to function simultaneously with said first changeover switch means and operable to connect with said electromagnet in place of a circuit including said second switch means and said first and second lamps, said release means functioning, when operated from the nonoperated position to the first position, to cause both checking means to function, whereby a photographer can examine the indicating means to decide whether to make an exposure, said release means functioning, when permitted to return directly to said non-operated position from said first position without entering said second position, to allow said camera to make no exposure, said release means functioning, when operated from the first position to the second position, to initiate and to cause the exposure-time control means to control the time duration of an exposure.