The centroid tracker is part of a PS 170 video image processing system which provides the precision beam position information that is the feedback portion of a stochastic control system for beam pointing. Mechanical vibration and electronic noise inherent in the system is used to enhance, rather than degrade, positional resolution. This system is capable of yielding centroid position information accurate to within a very small fraction of one pixel.
The centroid tracker is presently implemented on one Multibus board using primarily HCT 7400 series logic and large PLDs. Digitized R5170 video is supplied as the board's input. The video image's centroid information is supplied by the board every 33 milliseconds as the board's output. A unique hardware algorithm used on the board allows very high resolution, real time tracking with a relatively small amount of electronics. Included on the board is circuitry used to distinguish image pixels from noise and background pixels.
Other applications of the centroid tracker might include pick and place robot arm control, military target tracking and pointing, intruder localization and, in general, very high resolution, real time image position tracking.
The board can be modified relatively easily to allow real time, multiple object centroid tracking and we expect to do this in the future. The first of the Aurora beam control systems requires that 96 laser beams be simultaneously controlled. The multiple centroid tracker board will make it possible to do image processing at a higher rate, leading to increased position resolution, while still maintaining control system bandwidth.