A wide dynamic range integrating pixel with an accurately controlled logarithmic response

Abstract

A CMOS image sensor pixel is described that combines the sensitivity and speed of response at low light levels of a linear integrating pixel with the wide dynamic range of a logarithmic response. This is achieved by supplying an externally generated reference voltage to each pixel so that the effective integration time becomes a function of the photocurrent. In this paper the mathematical model of the pixel is extended to include non-ideal aspects of the pixels response so that the reference voltage can accommodate for these non-ideal aspects of the pixel so that the responsivity of the pixel can be accurately controlled.