Apparatus and methods for providing nonuniformity compensation of staring infrared focal plane array imaging systems, or other video imaging ssytem, or the like. The invention comprises a processor which implements nonuniformity compensation of the detectors comprising the array. The processor generates compensation terms that are stored in an offset term memory and which are subsequently combined with the output signals from the array. The processing accomplished by the present invention normalizes all detector elements in the array such that they all appear to respond to infrared energy in an identical manner. The processor comprises a median filter which selectively implements cross (X) shaped and plus (+) shaped filters. An antimedian calculator computes the antimedian of the output of the median filter. This value comprises the difference between the central pixel of a respective filter and the median value of all pixels in the cross (X) or plus (+) shaped filter. A third filter samples each of the signals from the detector array and compares them to a preset value indicative of an anticipated scene intensity level determined by the operator to provide an output signal indicative of the difference. Control circuity selects which output signal of the filter circuits is to be used to compensate the detector signals during a particlar video field. The ouptut signals of the antimedian calculator and average filter comprise sign information which is indicative whether the central pixel value is less than, equal to or greater than the median, or whether the central pixel is less than, equal to or greater than the preset value, respectively. The control circuitry increments or decrements the value of the offset terms stored in the offset term memory in resonse to the signal provided by the selected antimedian calculator or third filter, and convergence rate information supplied by the control circuitry which controls the rate of convergence of the offset terms toward the scene average.
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