Electronic shutter for a low differential light level photo-receiver cell

摘要

Circuitry provides an electronic shutter capability to photo-receiving circuitry for the purpose of disabling integration of a photo-generating charge on an integration capacitor until a reading device reads the integrated signal from the integrating capacitor. With an input from a shutter control line of a high logic voltage, the shutter discontinues charging of the integrating capacitor until the integration capacitor is selectively connected to a read line. Upon receipt of a low logic voltage signal from the shutter control line, the shutter allows the integration capacitor to integrate a photo-receiving charge. The electronic shutter therefore provides well controlled integration time via shutter control. Another advantage is that the integration time is completely independent of the cell reading rate. Since integration time is independent of the cell reading rate, the shutter module allows for automatic gain control of photo-receiver charge integration when exposed to a wide range of light through shutter control.