Low-power, high-speed, accurate computation of centroid from a pre-defined window in the image plane is important for a number of space-based and commercial applications. These include object tracking in robotic systems [1], autonomous navigation, image compression [2], and document copyright protection [3], as well as space guidance and navigation systems [4], and deep-space optical communication systems that require accurate and stable beam pointing for high speed data transfer [5].

Off-focal-plane digital processors yield accurate centroid values, but only at the cost of increased latency, power and size. On or near focal plane centroid computation using current mode circuits [6], and neuro­MOS circuits [7] have been implemented. However, neither approaches are integrated with high performance image sensors, nor are they entirely compatible with one. In this paper, we present a CMOS active pixel sensor (APS) with an integrated centroid-computation circuit that allows accurate X and Y centroid computation from a user-selectable window of interest. Such an imager offers real-time centroid computation while dissipating low-power and realizing a miniature tracking system.