The application of optical correlators for pattern recognition is well known, both with Vander Lugt (VLC) 4f correlator~1 and with joint transform correlator (JTC)~(2,3). A classical application of these correlators was mainly for the recognition of objects in complex images. The most important performance was the capability to identify an object, or classes of objects, even if it was magnified, shifted, rotated and surrounded by noise. The application of optical correlation for digital words recognition has a few examples in literature~4. The main performance needed for digital words recognition is very different from the one related to historical pattern recognition, and lays in the capability to discriminate the target word (the one to be recognized) from any other one, also if different in one bit only.
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