A Motion Sensor with On-Chip Pixel Rendering Module for Optical Flow Gradient Extraction

This work introduces a pixel rendering module (PRM) into an asynchronous event-based dynamic vision sensor (DVS) targeting for optical flow extraction. Optical flow using event-based cameras draws more attention since DVSs directly provide motion related information related and greatly reduce the data redundancy compared to conventional frame-based cameras. Although event-based optical flow has a high potential on real-time performance, its accuracy is limited by event sparseness and lack of intensity, especially for fast motion and highly textured areas. This paper presents a motion sensor with PRM and asynchronous gray-level events to settle these issues. The PRM enables each pixel to communicate with its neighbor pixels such that a single active pixel can force activate its neighboring inactive pixels to provide sufficient data for optical flow calculation. Furthermore, the sensor outputs asynchronous event packages including pixel position, time-stamp and its corresponding illumination. A 64 × 64 prototype was fabricated in 0.35um 2P4M Opto process. Each pixel occupies a footprint of 40 × 40 μm2 with 17 7% fill factor.