Real time camera exposure control

Abstract

The present invention discloses an electronic camera which processes the exposure of light by means of an imaging surface comprising a plurality of active pixel sensor circuits. Each pixel sensor circuit produces a small current inversely proportional to the amount of light that has fallen on a photodiode within the pixel sensor circuit. The individual currents produced by the active pixel sensor circuits are aggregated onto one or more current collection busses and operatively channeled to an operational amplifier assigned to a given bus. If a single operational amplifier is used, its output voltage is compared to a preset voltage level. When the voltage level decays to a preset level, a control signal is signaled. The control signal may be used to terminate further light exposure through traditional means such as triggering a “snubber” tube which immediately discharges the flash tube storage capacitor or turning off an IGBT high power transistor controlling the current through the flash tube, or, it may trigger an electronic shutter which prevents further photographic development of the imaging surface. Through the use of multiple operational amplifiers, different sectors of the imaging surface can be “weighted,” thereby giving greater effect to the light falling on select portions of the imaging surface.