Linear versus logarithmic spatial filtering in the removal of multiplicative noises

Linear and logarithmic coherent spatial-filtering techniques are compared in the separation of multiplicative noise from an image in a coherent-optical image-processing system. It is demonstrated that both techniques are effective in the removal of simple grating-type high-frequency noises, but that linear filtering cannot remove noise of spatial frequencies lower than 5 lines/cm, whereas logarithmic filtering can.