D. Asselin et Hh. Arsenault, ROTATION AND SCALE-INVARIANCE WITH POLAR AND LOG-POLAR COORDINATE TRANSFORMATIONS, Optics communications, 104(4-6), 1994, pp. 391-404
The optical implementation by means of holographic optical elements of
polar and log-polar coordinate transformations (CTs) for rotation and
scale invariant pattern recognition is attractive to achieve real-tim
e processing of input scenes. The quality of the CTs realized so far a
nd the image wrapping problem have limited this method to the processi
ng of the most simple objects. We propose a new CT implementation with
computer generated holograms partioned into non-uniform facets. The h
ologram recording is done with a commercial photo-typesetter at a very
low cost. The image wrapping problem is alleviated by means of juxtap
osed CTs. The intensity of the Fourier transform of the CTs is used to
correctly classify the objects, and only this classification step was
done numerically in our experiment. Optical results are presented and
demonstrate the quality of our CTs.