Since VanderLugt's famous 1964 paper showing that complex valued filters for optical matched filters could be
made, an extremely large number of papers have been written - some by me and some by Professor Goodman, and
many more by others. Yet optical Fourier transform filtering is almost never used for anything but university
research. The reasons are fairly well known but seldom stated. We have found one new approach to pattern
recognition that solves most of the problems and introduces a totally new and very useful thing that can be done
with Fourier filtering.