Patent ID: 7053354

Claim:
A method of operating a plurality of imaging cells, each imaging cell including: a reset transistor having a gate; and a photodiode connected to the reset transistor, the method comprising the steps of: placing a first magnitude of a reset voltage on the gate of each reset transistor of the plurality of imaging cells, the first magnitude being non-zero and insufficient to turn on the reset transistor; placing a second magnitude of the reset voltage on the gate of each reset transistor of the plurality of imaging cells for a pulse width period of time, the second magnitude being sufficient to turn on a reset transistor and set a diode voltage on a photodiode to have a first integration magnitude; reading the diode voltage on each photodiode a first integration period after the diode voltage has been set to determine a second integration magnitude of the diode voltage; reading the first integration magnitude of the diode voltage on each photodiode; determining a plurality of pixel values for the plurality of imaging cells so that a pixel value is determined for each imaging cell by subtracting the second integration magnitude from the first integration magnitude read; wherein the plurality of imaging cells are exposed to no light during the first integration period; and determining a number of cells which have pixel values that exceed a predetermined threshold.