Optical nonlinear correlation based on nonuniform subband decomposition

We present a nonlinear correlation to improve the selectivity for optical p attern recognition. The approach is based on morphological correlation whic h involves a threshold decomposition concept. Hereby, we propose a subband decomposition in the Fourier domain to perform the threshold decomposition operation. We consider two frequency bands that give rise to two separate c hannels. We apply the morphological correlation to each channel using a loc alized threshold decomposition. Then, we define a two-channel morphological correlation. The final detection decision is made as a combination of both correlation outputs. The two-channel morphological correlation yields impr oved discrimination capability and noise robustness compared with common li near and morphological correlation. Computer simulations are presented as w ell as optical experiments performed using a joint transform correlator.