HDR 4T-APS Pixel for Event Generation by Frame Differencing

In this paper we address the concept of an event detection pixel through frame differencing implemented with a high dynamic range (HDR) 4-Transistor Active Pixel (4T-APS) with Correlated Double Sampling (CDS). The concept of the pixel is illustrated with simulations in 180 nm CMOS technology. The 4T-APS pixel naturally cuts down noise, expecting to decrease false event generation present in many asynchronous event-based sensors in the absence of intensity changes. HDR is implemented locally through a simple algorithm executed on a lateral overflow integration capacitor alongside additional pixel memories and a circuit for addition and subtraction. Such pixel memories and arithmetic circuits are reused for both CDS, frame differencing, and event generation, amortizing hardware utilization. Electrical simulations show that the pixel could reach 1000 fps.