Wide dynamic range optical sensor

Abstract

A system and method is described for increasing effective integration time of an optical sensor including holding a first signal within each pixel cell, proportional to light integrated by the pixel cell over the previous frame period, generating a second signal within each pixel cell proportional to light integrated by the pixel cell over the current frame period, and summing the first signal and the second signal from each pixel, thereby producing an output signal representing the light integrated by each pixel over two frame periods. If saturation of pixel cells is possible, a further method of extending dynamic range is described including generating and storing a first signal in each pixel cell indicative of light integrated by the pixel cell over a long period, generating a second signal in each pixel cell indicative of light integrated by the pixel cell over a short period, and determining an output for each pixel as the first signal whenever the first signal is less than a threshold value, otherwise determining the output as the second signal. Also included are double correlated sampling for noise reduction, interlacing for increased integration time, and individual pixel reset for additional gains in dynamic range.