A logarithmic–logarithmic coordinate transformation is used to perform successfully scale and projection (tilt) invariant optical pattern recognition. The coordinate transformation is achieved optically using a computer generated hologram divided into four different quadrants since the logarithmic function does not exist for negative values of the argument. The transformed pattern is introduced into a VanderLugt correlator setup through a liquid crystal light valve. Initial experimental results are presented.
© 1989 Optical Society of America
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