Noise robustness of optical correlation for amplitude or phase modulation of the input image

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Abstract
We analyze the influence of the phase or amplitude coding of the input information in an optical correlator. For binary images, we show that the ratio between the signal-to-noise ratios of both codings is independent of the images when the matched filter is modified in order to have a zero mean value. Moreover these signal-to-noise ratios can be equivalent, but the price is a decrease in the amplitude of the correlation peak in the phase-coding case. With the nonmodified matched filter, characteristics of the phase coding appear to be unattractive.