A QCIF 145dB imager for focal plane processor chips using a tone mapping technique in standard 0.35μm CMOS technology

Abstract

This paper presents a QCIF HDR imager where visual information is simultaneously captured and adaptively compressed by means of an in-pixel tone mapping scheme [1]. The tone mapping curve (TMC) is calculated from a nonlinear histogram of the previous image, which serves as a probability indicator of the distribution of illuminations within the present frame. The chip produces 7-bit/pixel images that can map illuminations from 311 10-6lux to 5875 lux in a single frame in a way that each pixel decides when to stop observing photocurrent integration –with extreme values captured at 8s and 20 s respectively. Pixels use a 3x3 m2 Nwell-Psubstrate photodiode and an autozeroing technique for establishing the reset voltage, which cancels most of the o set contributions created by the analog processing circuitry. Measured sensitivity is 5.79 V lux s . Dark current e ects in the final image are attenuated by an automatic programming of the DAC top voltage. The chip has been designed in the 0.35 m OPTO technology from AMS.