FOURIER-PLANE WINDOWING IN THE BINARY JOINT TRANSFORM CORRELATOR FOR MULTIPLE-TARGET DETECTION

With recent advances in state-of-the-art spatial light modulators, the optical joint transform correlator (JTC) and the binary joint transfo rm correlator (BJTC) are becoming practical signal-processing tools. T he performance of these devices is limited by the difficulty of separa ting the cross correlation between the reference and the targets in th e scene from signals resulting from cross correlations between objects in the target scene. One technique that reduces this problem is to us e a sliding window in the Fourier plane as a convolution mask filter t o set an adaptive binarization threshold. This suppresses the autocorr elation response and reduces the dynamic range of the Fourier-plane si gnal. This results in correlation performance improvement by a factor of 2 to 4. A mathematical model is developed to describe the windowing process for both the JTC and BJTC for the case in which the scene con tains multiple targets and background clutter. The derivation of the w indowing process is general and includes any spatial high-pass or band pass filtering in the Fourier plane. The results are supported with ex perimental data.