Object detection from a real scene using the correlation peak coordinates of multiple circular harmonic filters

Theory and optical implementation of the geometrical approach of multiple circular harmonic filters

The circular harmonic filter contains only one component of the image. Its discrimination capability has been questionable. The geometrical approach of multiple circular harmonic filters uses relative locations of the correlation peaks as the rotation-, shift-, and intensity-invariant features for pattern recognition. Each feature depends on the entire image. This approach has a good discrimination capability. Optical real-time implementation of the on-axis continuous phase-only circular harmonic filters by the use of a commercial liquid-crystal television is shown. A harmonic analysis shows that the phase-mostly filter can tolerate coupled amplitude modulation at the acceptable expense of the output signal-to-noise ratio. An optical experiment of the geometrical approach of multiple circular harmonic filters for a multiple-image input is described. The cross-correlation peaks between the individual filters and the clutter are eliminated, because they are not in good locations.

Fast design of circular-harmonic filters using simulated annealing

A new method is presented for determining the proper center of the circular-harmonic filter using an analytical expression for circular-harmonic expansion about an arbitrary center and simulated annealing for the automatic search of the maximum. The new method is two orders of magnitude faster than the previous method.

Tutorial survey of composite filter designs for optical correlators

A tutorial survey is presented of the many composite filter designs proposed for distortion-invariant optical pattern recognition. Remarks are made throughout regarding areas for further investigation.

Circular-harmonic function, minimum average correlation energy filters

New distortion-invariant correlation filters for in-plane rotation invariance are considered. These use circular-harmonic functions combined with minimum-average correlation-plane filter techniques. Various circular-harmonic function shortcomings are quantified.