FILTER MULTIPLEXING FOR CORRELATORS BY MEANS OF INCOHERENT-LIGHT

Optical correlators with incoherent light offer many of the advantages of correlators with coherent light, yet they are not as sensitive to coherent noise and alignment errors. Moreover, sophisticated and compl ex spatial modulators are not needed. The correlation is performed by comparing the input scene with some predefined reference object that w as recorded earlier in a single holographic filter. To increase the nu mber of objects that can be simultaneously correlated, or, alternative ly, allow rotation and scale changes of one object, we investigated ho w best to record holographically a multiplicity of different objects i n one composite filter. We determined that for high SNR it is necessar y to illuminate the recorded object with diffuse light. Results from c omputer simulation and laboratory experiments reveal that 16 different objects can be holographically recorded in one composite filter and t hen used for simultaneous correlation giving sharp correlation peak wi th good peak to background ratio. Alternatively, the range of rotation invariant correlation can be increased from a few degrees for a singl e filter to 160 deg for a composite filter of 16 objects.