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Filter-feature-based rotation-invariant joint Fourier transform correlator

Summary: Filter-feature-based rotation-invariant
joint Fourier transform correlator
Farid Ahmed and Mohammad A. Karim
Rotation-invariant target detection using a trained filter-feature-based joint Fourier transform 1JFT2
correlator is investigated. First, a composite reference image is obtained from a training set of
targets. An optimum filter formulation is then applied on this composite image to come up with a new
feature that we refer to as a filter feature. This feature is then used in a JFT correlator, which results in
a simple and robust rotation-invariant target recognition system. r 1995 Optical Society of America
1. Introduction
Classical matched correlation1 and joint Fourier trans-
form 1JFT2 correlation24 are the two most widely
used techniques in optical pattern recognition. A
phase-only filter5 and its variants were developed to
improve correlation performance, however, none of
these techniques is inherently rotation invariant.
Rotation invariance in the literature is addressed in
two different ways. The first approach uses geomet-
ric invariance properties in the filter formulation.68
For these studies circular harmonic filter expansion
for rotation invariance was used. The main draw-


Source: Ahmed, Farid - Department of Electrical Engineering and Computer Science, Catholic University of America


Collections: Engineering