Many real-world pattern recognition problems entail location of an image within a very cluttered environment. Hybrid processing can be valuable in such a situation by using the high-speed parallelism inherent in optical processing for the feature extraction step, since feature extraction is often the most time-consuming operation to perform digitally. The work reported here takes such an approach for finding addresses on cluttered mail. Two optical systems, a coherent spatial filtering system and an incoherent correlation system, are each discussed for use in combination with digital image processing techniques. Examples of mail processed and statistical results are presented.
"Hybrid Techniques For Postal Address Location", Proc. SPIE 0939, Hybrid Image and Signal Processing, (18 July 1988); doi: 10.1117/12.947057; https://doi.org/10.1117/12.947057