Effects of thresholding in joint-transform correlation

Abstract

The joint-transform power spectrum of two identical objects can be represented as a one-dimensional sinusoidal grating modulated by a Fourier transform, and the correlation peaks can be regarded as the first-order diffraction of the grating. The peak intensity and the width are then determined by the aperture and the modulation of the grating. Based on this analysis, it is shown that dc blocking, hard clipping, or binarization of the power spectrum results in higher correlation peak intensity and a narrower peak width. Direct-current blocking is also found to be preferable if the input pattern to the correlator is corrupted by noise.

Real-time joint transform correlator using compressed reference images

“…[11][12][13][14] A study of the performance of the JTC using compressed reference images is yet to be done. For these reasons, this work studies quantitatively the effects of the compression on the performance of the JTC.…”

Noise-robust low-contrast retinal recognition using compression-based joint wavelet transform correlator

“…Secondly, noise suppression ability of the JPEG compression has been verified to be useful for improving the CBJTC detection performance. Thirdly, the JTC has been widely employed for realtime implementation of pattern recognition [16][17][18][19][20][21].…”

Optical implementation of the weighted sliced orthogonal nonlinear generalized correlation for nonuniform illumination conditions

“…6 Some of those improvements are based on increasing the discrimination capability by applying various mathematical functions, such as thresholding, coding, or nonlinear functions in the power spectrum domain. [7][8][9][10] Moreover, some nonlinear correlation based on the addition of binary slices of the power spectra of the input scene and of the reference object have been implemented optically using a JTC. 11,12 Such nonlinear correlations provide higher discrimination capabilities than other JTC techniques.…”