JPS6443733A - Photometry circuit - Google Patents

Abstract

PURPOSE:To attain photometry to the quantity of object field light in the shortest time by providing an area sensor, a driving circuit, and a decision circuit, etc., and then utilizing the area sensor whose charge storage time is controllable effectively. CONSTITUTION:The driving circuit 14 drives the area sensor whose charge storage time is adjusted in normal photography, a driving circuit 16 for photometry drives the sensor 10 at the time of light measurement, and a stop driving circuit 26 actuates a stop mechanism 24 which controls the quantity of light incident on the sensor 10. Further, the circuit 16 generates a driving clock for outputting a signal which differs in storage time from the sensor 10 at intervals of a horizontal scanning line. In the video signal outputted by the sensor 10, a signal integral value of each scanning line reflects on the result of the simulation of photography with a different shutter speed. Then the decision circuit 28 integrates the output signal of the sensor 10 at intervals of a horizontal scanning line and compares the integral value with a specific reference value to decide which storage time the best quantity of exposure is obtained with. Thus, the quantity of subject field light is measured in the shortest time.