Fast order-recursive algorithms for optimal stack filter design

For the nonlinear classes of filters based on the median archetype, e.g. stack, weighted order statistics (WOS), morphological filters the techniques exploiting recursiveness of embedded structures were not used yet. We investigate in this paper the possibilities of improving the speed of the optimal design techniques restating the optimal design problem as a sequence of optimal problems for embedded structures. The speed up effect of recursive-in-order design techniques is very significant but it is not the only benefit of this principle: it also allows the evaluation of the optimal structure of the filter, comparing the performances of the optimal filters having various structural parameters and observing where the performance index curve starts to flatten with the increase in the structure "size".