ELECTRONIC SHUTTER DEVICE

摘要

1340930 Photographic camera shutter control NIPPON KOGAKU KK 19 April 1971 [6 April 1970] 25679/71 Heading G2A Light incident upon a photo-sensitive element P from an object to be photographed induces a voltage whose magnitude is in proportion to a logarithm of the current flowing through the element, the voltage being compared with a second voltage induced by a correction current i for setting a film speed and a current whose magnitude is varied in response to a number of pulses counted by a binary counter CU so that when the difference between the first and second mentioned voltages reaches a predetermined value the counter is stopped and during a subsequent shutter operation a current in proportion to an expotential of a voltage representative of the count stored in the counter is used to charge a capacitor C, the shutter being closed when the integrated value reaches a predetermined level. Pulses from a pulse generator PG1 are fed to the counter CU via a gate GT, the counter being periodically reset by a further pulse generator PG2. The voltage difference is detected across a diode D and when it reaches a predetermined value the potential at the output of operational amplifier B goes negative to inhibit gate GT. Upon depression of the shutter button, switch S 4 is opened and switch S 3 is closed to inhibit gate GT after a time delay sufficient to allow CU to complete counting. Upon completion of counting switch S 1 is moved to contact u, switch S 2 is opened, and when the shutter opens switch S 5 is opened. The photo- voltaic element P may be replaced by a photoconductive element. An indicator IND connected to the counter via a decoder DEC indicates the state of the counter and may be a photo-emitting diode or a multi-tip or monothilic type of indicator.