A 148dB focal-plane tone-mapping QCIF imager

Abstract

This paper presents a QCIF HDR imager where visual information is simultaneously captured and adaptively compressed by an in-pixel tone-mapping scheme [1]. The tone mapping curve (TMC) is calculated from the histogram of an auxiliary previous image, which serves as a probability indicator of the distribution of illuminations within the current frame. The chip maps 148dB scenes onto 7-bit/pixel coding, containing illuminations from 2.2mlux (SNR10) to 55.33klux -with extreme values captured at 8s and 2.34µs, respectively. Pixels use an Nwell-Psubstrate photodiode and autozeroing for establishing the reset voltage. Measured sensitivity is 5.79 V over lux·s. Dark current effects in the final image are attenuated by an automatic programming of the DAC levels. The chip has been fabricated in the 0.35µm OPTO technology from AMS.