A method is presented that performs the optical wavelet transform with liquid-crystal televisions as spatial light modulators operating only on the phase of the incident coherent light. The architecture is the joint-transform correlator, and the wavelets and the image to be transformed are encoded in the input plane of the system. The mathematical formalism describing the adaptation of the joint-transform correlator to the wavelet transform is given and extended to the operation of the phase-only joint-transform correlator. A new wavelet is described for two-dimensional image processing, and experimental results are presented for optical wavelet transforms done in real time by use of this wavelet in the phase-only joint-transform-correlator architecture. The analysis is extended to multiwavelet (multispectral) analysis by the joint-transform correlator, and simulation results are given. Finally experimental results with the phase-only joint-transform correlator applied to multi-wavelet analysis are presented.

An analysis of the popular joint-transform optical correlator is presented for architectures employing spatial light modulators that operate only on the phase of the coherent light. Experimental results are also presented, for simple scenes that produce analytic solutions, which support the analysis.

A noninterferometric technique is presented for determining the phase modulating characteristics of spatial light modulators. Examining the far-field diffraction pattern intensity distribution for specific input functions enables the phase modulation to be calculated. Results are compared with usual interferometric techniques for a liquid crystal based modulator. © 1996 Society of Photo-Optical Instrumentation Engineers.

In this paper, a multichannel optical wavelet processor and a matching pursuit processor capable of enhancing the detection of cluttered targets are presented. Wavelet functions have zero-mean and are virtually band-pass filters. In many cases, targets and clutter are separable in the spatial spectral domain. Therefore, by selecting wavelet functions that represent features of targets but are insensitive to that of clutter, targets can be extracted from the input scene while clutter is suppressed. Due to dyadic sampling, a multichannel optical wavelet processor with a limited number of channels can detect regions of interest for different targets. With matching pursuit decomposition. features of targets are extracted and represented in a few wavelets known as coherent structure: whereas clutter and noise are diluted across the dictionary. Clutter and noise can then be effectively removed from the signal by a simple thresholding operation. A time-frequency energy distribution can be derived from matching pursuit decomposition, which contains no interference terms and thus clearly characterizes the input signal in the time-frequency plane. Optical architectures of these processors are described. Simulated and experimental results are provided.

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