A Relative Imaging CMOS Image Sensor for High Dynamic Range and High Frame-Rate Machine Vision Imaging Applications

This paper proposes an unconventional image acquisition scheme for machine vision applications, based on detecting ratios of illumination (pixel) intensities. Detecting relative ratios enables capturing the scene features and patterns almost independently from the local scene illumination resulting in potentially extremely high dynamic range. Moreover, detecting signal ratios using a fully differential circuit optimally suits the intrinsic nature of VLSI design. A scalable and compact hardware implementation is proposed as a proof-of-concept towards relative image acquisition. The proposed photo-currentratio- detecting pixels completely bypass the need of conventional photo-current integration which enables high frame-rate operation of up to 24000 frames-per-second (fps). The pulse-widthmodulated output of the proposed pixel is captured by compact column-parallel readout circuits based on digital counters. The developed 3232 pixel array prototype CMOS image sensor consumes 4mW of power operating at a nominal 9765 fps frame rate, and 6.8mW of power operating at a maximum 24000fps. The presented prototype design is fully scalable towards newer CMOS fabrication nodes and higher sensor resolution.