Electronic flash system

An electronic flash system used for obtaining light energy to illuminate the object to be photographed, comprising:

• a flashtube;
• an electric energy storage means for storing light energy to be applied to the flashtube;
• a discharge circuit connecting the storage means to the flashtube to produce a flash of light;
• a trigger circuit connected to said flashtube for actuating the emission of the flashtube;
• switching means for controlling the closing and opening of the discharge circuit;
• monitoring means connected to said switching means for monitoring luminous intensity of reflected light from the object subjected to a flashlight, said monitoring means being adapted to produce an output signal when said luminous intensity of reflected light reaches a predetermined value;
• control means connected to said switching means for controlling actuation of said switching means, said control means being adapted to produce a control signal for operating said switching means to close the discharge circuit when said trigger circuit triggers the flashtube, said switching means being prevented from being actuated by said control means to maintain the discharge circuit in open condition after the passage of a predetermined time from actuation of said switching means to open the discharge circuit whenever said monitoring means provides an output signal, the intensity of reflected light incident upon the film from the object to be photographed being at a predetermined level, independent of the distance to the object, the intensity of the flash being substantially constant independent of the distance of the object, the exposure time constant being maintained to maintain a predetermined photographic density, said switching means being actuated initially to close the discharge circuit by a control signal from said control means when said trigger circuit triggers said flashtube, said switching means being actuated by said control means to maintain the discharge circuit in closed state until said monitoring means provides an output signal, said switching means being actuated by said control means to repeatedly close and open said discharge circuit for a predetermined period when said monitoring means provides said output signal, said switching means being actuated by said control means to maintain said discharge circuit in open state after lapse of said predetermined period.