A wide dynamic range integrating pixel with controllable logarithmic photoresponse

Abstract

The digital imager sensors integrated into most current systems have a linear response and a dynamic range of 60dB or less. This is not a large enough dynamic range for some applications. Although suitable for most applications there are some emerging applications, such as automotive safety, that require a dynamic range of 120dB. In this paper a pixel circuit for a 0.35-µm CMOS technology is described that integrates the photocurrent in the pixel for time that depends upon the photocurrent to create a wide dynamic range response. Similar pixels have been described previously, however for this process the critical user defined reference voltage has been modified to compensate for capacitive coupling between nodes within the pixel. More importantly, a MOSFET functioning as a charge spill gate has been included in the pixel to improve the pixel's low light sensitivity.