A 1/4-inch 3.9Mpixel low-power event-driven back-illuminated stacked CMOS image sensor

Abstract

Wireless products such as smart home-security cameras, intelligent agents, and virtual personal assistants, are evolving rapidly to satisfy our needs. Small size, extended battery life, transparent machine interfaces: all these are required of the camera system in these applications. These applications, in battery-limited environments, can profit from an event-driven approach for moving-object detection. This paper presents a 1/4-inch 3.9Mpixel low-power event-driven (ED) back-illuminated stacked CMOS image sensor (CIS) deployed with a pixel readout circuit that detects moving objects for each pixel under lighting conditions ranging from 1 to 64,000lux. Utilizing pixel summation in a shared floating diffusion (FD) for each pixel block, moving object detection is realized at 10 frames per second while consuming only 1.1mW, a 99% reduction in power from the same CIS at a full-resolution 60fps power of 95mW.