Binarization of the joint transform correlator Fourier plane based on local window processing

One of the main factors determining the performance of a binary joint transform correlator is the method used to set the binarization threshold in the transform plane. An adaptive threshold can be set by computing the average of a small local window around each pixel. It is shown theoretically and verified experimentally that the optimum size of this window for a practical BJTC configuration is a single column wide and 3 - 5 pixels long. The detection peak amplitude in experimental runs using a local window was 2 - 4 times as large as in runs using the median of the Fourier plane as the threshold. Since these adaptive thresholds are easier to compute than the median of the entire Fourier plane, this technique can be used to improve BJTC performance while reducing system complexity.