Reduction and Removal of Replication in an Optical Processor by Randomization of Pixel Positions in the Fourier Plane Filter

When a pixellated spatial light modulator (SLM) is used in an optical processor, replicated images occur in the output due to the underlying regular pixel structure of the SLM. These replicas arise through convolution with distinct spectral orders in the SLM's Fourier spectrum and in the case of a correlator can lead to false correlation signals. A means of suppressing or eliminating the spectral orders through randomization of the pixel positions is presented, with analysis of the Fourier spectrum of random arrays. Two specific randomization schemes are considered and the results are compared with that for a regular array.