A Real-Time Edge-Detection CMOS Image Sensor for Machine Vision Applications

Abstract

This paper presents a real-time edge image extraction CMOS image sensor (CIS) with an edge detection counter for machine vision applications. By examining a conventional column-parallel CIS imaging structure with a single-slope analog-to-digital convertor, it discovered an additional time slot available to extract information of an additional image during a normal imaging operation of two adjacent columns. While obtaining a normal image in this study, the prototype CIS with the proposed edge detection counter effectively utilizes the spare time for extracting an additional column edge image without an image signal processor and any computational latency. In addition, by applying a proposed variable edge thresholding function, the proposed CIS can adopt an optimum edge threshold value according to its imaging condition, alleviating an inherent limitation of a column edge image. This prototype CIS was fabricated using a 0.18-μm 1P6M CMOS process with an effective pixel resolution of 320 (H) × 320 (V). The prototype consumes 17.72 mW power with a frame rate of 240 frames per second. The prototype CIS demonstrated a figure of merit of 721 pW/frame pixel.