A feature-based optical character recognition system, employing a feature-based recognition device such as a neural network or an absolute distance measure device, extracts a set of features from segmented character images in a document, at least some of the extracted features being at least nearly impervious...http://www.google.com.au/patents/US5054094?utm_source=gb-gplus-sharePatent US5054094 - Rotationally impervious feature extraction for optical character recognition
