A modified circular harmonic filter may be used for the rotation-invariant discrimination of a target from another object which contains the same pattern as the target. The method is illustrated by the experimental rotation-invariant detection of the letter F in the presence of the letter E.
© 1983 Optical Society of America
H. H. Arsenault and Yuan-Neng Hsu, "Rotation-invariant discrimination between almost similar objects," Appl. Opt. 22, 130-132 (1983)