When optical correlation employing holographic Vander Lugt filters is applied to pattern recognition the detector output is easily influenced by size variations in the pattern. A method is proposed and tested to compensate these influences by tuning the light source to a different wavelength. The theoretical basis for this operation is developed and examples are presented where the correlator output has been evaluated quantitatively for changes in size and wavelength. It is demonstrated that the correlation functions agree well with theoretical expectations and that the correlation peak which is degraded by size variation may be restored by tuning to the appropriate wavelength.
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