Patent ID: 7696545

Claim:
An imaging device comprising: a plurality of pixels, each pixel comprising a photo sensor, a first gate for storing charge from the photosensor when activated by a first control signal during a sampling period, and a floating diffusion region for storing charge transferred from the photosensor after an integration period; a plurality of sense circuits, each sense circuit being connected to and associated with a column of pixels, each sense circuit generating the first control signal during the sampling period for a selected pixel in its respective column and sensing whether an amount of charge stored under the first gate of the selected pixel exceeds a predetermined threshold, each sense circuit outputting to the pixel a voltage flag representative of a number of times the sensed charge exceeds the predetermined threshold within the integration period, wherein each pixel stores the voltage flag in its floating diffusion region during the sampling period to indicate a number of times the sensed charge exceeds the predetermined threshold during the integration period; and an image processor adapted to modify pixel signals output after the integration period based on the number of times the sensed charge exceeded the predetermined threshold in the integration period, wherein at least one of said sense circuits comprises: a sensing portion for sensing the charge stored under the first gate and outputting the sensed charge as a first output; a first comparator portion for comparing the first output to the predetermined threshold, the first comparator portion generating a second output each time the first output exceeds the predetermined threshold; an adder connected to the first comparator portion and summing a number of second outputs from the first comparator portion; and a flag setting portion for setting a value of the voltage flag based on the summed number of second outputs.