Synthetic discriminant functions (SDFs) allow distortion invariance to be achieved in optical correlators, thus making such systems more practical. The synthesis of four different types of SDFs is reviewed. Their performance in extensive projection tests on 144 images is presented, together with initial performance tests in the presence of noise. This distortion-invariant and shift-invariant pattern recognition algorithm can also be implemented digitally.
"Projection Synthetic Discriminant Function Performance," Optical Engineering 23(6), 236716 (1 December 1984). https://doi.org/10.1117/12.7973369