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Temporal filtering for point target detection in staring IR imagery: II. Recursive variance filter

We describe a recursive temporal filter based on a running estimate of the temporal variance followed by removal of the baseline variance of each pixel. The algorithm is designed for detection/tracking of 'point' targets moving at sub- pixel/frame velocities, 0.02 to 0.50 p/f, in noise-dominated scenarios on staring IR camera data. The technique responds to targets of either polarity. A preprocessing technique, morphological in origin but implemented by median filters, further improves the S/N sensitivity of the algorithm while restricting the result to positive contrast targets. The computationally simple algorithm has been implemented in hardware and real-time operation is in evaluation. The performance is characterized by some specific examples as well as plots over our extensive database of real data. Detection down to S/N approximately 3 or less and sensitivity to the appropriate range of velocities is demonstrated.