Patent ID: 6539176
Filing Date: 2003-03-25
Classification: G03B

Abstract:
A photometry device provided in a camera, for detecting whether a subject brightness is less than or not less than a reference level, comprising:a photoconductive element located to receive light from a subject, a first end of said photoconductive element being connected to a first electrode of a power source; a resistor whose first end is set at the same potential as the first end of said photoconductive element; a first transistor connected at its base to a second end of said photoconductive element, at its collector to a second end of said resistor and at its emitter to a second electrode of the power source; a second transistor connected at its base to the second end of said resistor, at its collector to the second end of said photoconductive element, and at its emitter to the second electrode of said power source; and a switching transistor which is turned on in response to a predetermined one of said first and second transistors being turned on, wherein said first and second transistors are turned on and off in contradiction to each other depending upon whether a current flowing through said photoconductive element is less than or not less than a current flowing through said resistor, so the switching condition of said switching transistor is used for detecting whether the subject brightness is less than or not less than the reference level.