Camera with automatic exposure-determining structure

Details Camera with automatic exposure-determining structure Camera with automatic exposure-determining structure

1975-03-04

1976-07-13

Hix, L. T.

354 23D, 354 43, 354 50, 354 60L, 354268, G03B 714

Patent

active

039697355

ABSTRACT:
A camera which has the capability of automatically determining exposure of film. A light-responsive structure of the camera produces a number of pulses which is inversely proportional to light brightness while a reference pulse generating structure is capable of producing a series of reference pulses. A binary counter is connected through a switch structure to both the light-responsive structure and the reference pulse generating structure, with the switch structure first connecting the light-responsive structure to the binary counter so that the latter counts the number of pulses which is inversely proportional to light brightness. Thereafter an inverting structure which is connected to the binary counter inverts the number of pulses counted thereby, and then the switch structure disconnects the light-responsive structure from the binary counter and instead connects the reference pulse generating structure thereto so that the binary counter then counts reference pulses. The shutter is opened simultaneously with the connection of the reference pulse generating structure to the binary counter, and an automatic exposure-terminating structure detects when the number of reference pulses counted by the binary counter equals the number of pulses which were counted by the binary counter when it was connected by the switch structure to the light-responsive structure. Upon detecting this equality the exposure-terminating structure causes the shutter to be closed so that the exposure is terminated. In this way automatic exposure is capable of being determined by a digital counting structure rather than by a memory capacitor, for example.
The camera further includes a blocking circuit for preventing the opening of the shutter when the number of pulses received by the counter from the light responsive structure is beyond one end of a given range and a digital diaphragm control circuit for adjusting the diaphragm when such a condition occurs.

REFERENCES:
patent: 3813680 (1974-05-01), Wagensonner et al.
patent: 3827065 (1974-07-01), Wada

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