<title>Optical wavelet correlators for cluttered target identification</title>

Abstract

Quantex Corporation2 Research Court, Rockville, MD 20850Nicholas P. CavirisNaval Surface Warfare Center, Code B4210901 New Hampshire Avenue, Silver Spring, MD 20903Mary WenSensci Corporation1423 Powhatan Street, Suite 6, Alexandria, VA 22314ABSTRACTNovel optical wavelet correlators are presented in this paper. Instead of computing the correlation betweenthe target and the reference patterns, these optical wavelet correlators compute the correlation between the wavclcttransform coefficients of the target and reference patterns. It incorporates the efficient feature detection and flOISCsuppression capabilities ofwavelet transformation and the inherent high speed and 2-D nature of optics. The featureextraction and target identification operations are performed in a single step. By suitably choosing the waveletfunctions and their dilation factors, these wavelet correlators are capable of effectively recognizing targets in thepresence of clutter and noise. Architectures for both Vander Lugt type wavelet correlator and wavelet joint transformcorrelator are discussed in the paper. A wavelet function especially suitable for optical implementation is described.Preliminary experimental results are provided.1. INTRODUCTIONSince Vander Lugt introduced the concept of the spatial matched filter in 1964 1 1 J, optical correlators havebeen widely used as a powerful tool in many optical pattern recognition applications [2J. The Vander Lugt typecorrelator, as well as the joint transform optical correlator developed later [3,4, compute the correlation betweenthe reference templates and the input scene. If there is a match between the input signal and any of the reh.reneepatterns, a correlation peak occurs. In most of the real-world applications, however, the target to he identified is