Hybrid implementation of nonlinear joint-transform correlator

Abstract

Nonlinear joint transform correlator (JTC) uses nonlinearity at the Fourier plane to nonlinearly transform the Fourier transform interference intensity.1,2 The nonlinear transformation is implemented by two methods. In one method, an optically addressed spatial light modulator (SLM) that operates in nonlinear mode is used at the Fourier plane to nonlinearly transform the joint power spectrum. In the second method, a hybrid optical processor is used to produce the nonlinear transformation. A charge-coupled device array is used to produce the joint power spectrum and electronic circuit device is used to nonlinearly transform the joint power spectrum. The transformed joint power spectrum is written onto a SLM and the nonlinear correlation signals are produced. In this paper, we provide an experimental investigation of the hybrid optical processor to implement the nonlinear JTC. Experiments are used to determine the correlation peak intensity and peak to sidelobe ratio, and correlation width for various degrees of the nonlinearity used at the Fourier plane. The results are compared with the linear JTC. The nonlinear transformations are performed using a computer interfaced with the CCD array. The experiments are performed in the presence of the input scene noise. The nonlinear JTC experiments indicate that reasonably good correlation performance can he obtained using the hybrid nonlinear JTC.