Back to results
US 4,789,777 AGranted
Photelectric amplifier having plural actuable feedback paths
AssigneeAsahi Kogaku Kogyo Kabushiki Kaisha
InventorsSatoshi Takami, Yutaka Ohsawa
Life of this patent
Estimating the term…
Abstract
A photoelectric amplifier in a camera exposure system, in which a photodiode is connected across the inputs of an operational amplifier and charges an integrating circuit in a feedback path across the operational amplifier. The resistance of the feedback path can be varied in response to the film sensitivity. The output of the operational amplifier is compared against a films speed reference voltage. Thereby, a reduced range of film speed reference voltages need to be provided because of the optional gain of the photovoltage.
Claims5
A photoelectric amplifier comprising:
- a photosensitive element;
- an operational amplifier receiving an output of said photosensitive element;
- integrating means having a first terminal connected to said photosensitive element and being charged by said photosensitive element;
- a first electrical path connecting a second terminal of said integrating means to a non-inverting input terminal of said operational amplifier through a first resistance;
- an actuable second electrical path connecting an output terminal of said operational amplifier to said second terminal of said integrating means;
- an actuable third electrical path connecting said output terminal of said operational amplifier to an inverting input terminal of said operational amplifier;
- selecting means for selectively actuating said second and third paths, an integration voltage based on an input offset voltage of said operational amplifier being stored in said integrating means as an output of said operational amplifier when said third path is actuated.
4 more elements
Dependencies are inferred from the claim text.