An incoherent optical correlation system for median filtering
Ellen Ochoa, Jan P. Allebach, Donald W. Sweeney · Annual Meeting Optical Society of America · 1986
Median filters are widely used in image processing because they remove impulsive noise while preserving edges. They are one example of a class of filter known as order statistic filters which require a ranking of pixels within the filter window. When only one of the ordered pixels (the i th pixel) is then selected as the output of the filter, the result is called the i th ranked-order operation. The median filter of window size N is therefore an (N + 1)/2 ranked-order operation while the maximum and minimum filters are, respectively, Nth and 1st ranked-order operations.