A digiuil image processing inspection system is under development at Oak Ridge National Laboratory that will locate image features on printed material and measure distances between them to accuracies of 0. 001 in. An algorithm has been developed for this system that can locate unique image features to subpixel accuracies. It is based on a least-squares fit of a paraboloid function to the surface generated by correlating a reference image feature against a test image search area. Normalizing the correlation surface makes the algorithm robust in the presence of illumination variations and local flaws. Subpixel accuracies of better than 1/16 of a pixel have been achieved using a variety of different reference image features.

Date Published: 1 March 1991
PDF: 10 pages
Proc. SPIE 1386, Machine Vision Systems Integration in Industry, (1 March 1991);

Published in SPIE Proceedings Vol. 1386:
Machine Vision Systems Integration in Industry
Bruce G. Batchelor; Frederick M. Waltz, Editor(s)