Scale, rotation, and shift invariant image recognition

A circular harmonic filter illuminated with white light illumination is used to achieve scale, rotation, and shift invariant image recognition. The circular harmonic expansion of an object is utilized to achieve rotation and shift invariant image recognition. Scale invariance is added using a broadband dispersion-compensation technique. When illuminated with broadband light, the frequency-plane filter simply selects the wavelength from the spectrum that produces the same size transform as that recorded in the filter. Laboratory experiments that demonstrate the operation of the technique are presented.