Sensitivity and uniformity of a 0.18µm CMOS temporal contrast pixel array

Abstract

A QVGA array of autonomous, event-based temporal contrast sensitive pixels is at the basis of an asynchronous, time-based CMOS dynamic vision and image sensor (ATIS). In this sensor, exposure measurements are initiated and carried out locally by individual pixels upon detection of temporal contrast in their field-of-view. The change detection pixel circuits respond with low latency to temporal contrast (i.e. relative changes in illumination) by generating `spike' pulse events. The vision sensor has been implemented in a 0.18μm CMOS process, fabricated and characterized. To assess the quality of the change detector array, contrast sensitivity, noise behavior and response uniformity are crucial performance figures. In this paper, we propose a test method that allows acquiring and evaluating these three performance parameters simultaneously. The results are shown to agree well with predictions from theoretical considerations, validating the proposed test method. The ATIS change detector array exhibits RMS noise equivalent contrast between 2% and 4% and achieves array response mismatch of 1.9% RMS.