Ultra-Wide Dynamic Range CMOS Imager Using Pixel-Threshold Firing

摘要

In this paper, we present a novel CMOS imager that offers a dramatic improvement in dynamic range over standard CMOS imagers. The dynamic range of conventional CMOS imagers is usually limited to about 60 dB because the photodiode has a nearly linear response and all pixels have the same exposure time. In our imager, each pixel has a unique exposure time determined by the pixel's signal level. Using this scheme, the imager can achieve a dynamic range of more than 120 dB. Information about each pixel's illuminance is represented in the time domain. This allows a counter to report the pixel values as digital signals so no analog-to-digital converter is needed. Furthermore, the imager has lower power consumption compared with other wide dynamic range imagers. Block diagrams and preliminary simulation results are presented, and an imager with a 64 x 64 array of pixels is scheduled for fabrication through MOSIS in the AMI 0.5 μm process.