Incoherent method for rotation-invariant recognition

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.

Computerized design and generation of space-variant holographic filters. 1: System design considerations and applications of space-variant filters to image processing

A computerized optical system has been constructed for the design and generation of space-variant holographic filters. Special considerations of the computerized design of the space-variant filters and the operation and performances of the system are addressed and discussed. The system was experimentally employed to generate holographic optical filters for the optical implementations of Hough transform, coordinate transformations, etc. Experimental performances of the generated space-variant filters are evaluated and discussed.

Effective optical processor for computing image moments at TV rate: use in handwriting recognition

An incoherent multiplexed optical processor is described that computes in real time the moments of images sensed by a TV camera and displayed on a monitor. The first ten moments are generated in parallel and are detected by a photodetector array. They are collected by a microcomputer for subsequent pattern recognition use. Calibration and resolution problems are discussed with regard to the effective 2% system accuracy. Its use in real-time processing of one hundred handwritten pages shows the processor to be a practical moment generator.

Rotation-invariant digital pattern recognition using circular harmonic expansion

A new method has been developed for rotation-invariant pattern recognition. One component of the circular harmonic expansion of the target is used in the preparation of the reference. Correlations between the input and reference objects are accomplished by FFT and multiplication in the frequency domain. In an experience with targets from an image with 192 x 192 pixels, target orientations were detected with an accuracy of approximately 0.1 degrees . This method is also suitable for optical implementation.

Optical pattern recognition using circular harmonic expansion

Presented in this paper is an optical implementation of a shift- and rotation-invariant pattern recognition technique. A computer-generated hologram is designed to match with one of the circular harmonic components of the target. Experimental results with simple photographic objects show that targets with different locations and orientations can be simultaneously recognized by the optical system.