Two stage discriminant analysis has been proposed for multi class recognition. In the second stage, multiple discriminant analysis is applied to the identification for each set of classes, which are not distinctly classified in the first stage. The proposed method is applied to character recognition for the method estimation. The recognition rate was 99.3% for 91 categories of alphanumerics and special symbols. The recognition speed was 20 milliseconds per character, when this analysis program was executed on image pipelined processors. It has been shown that this method is further applicable to character sequence recognition without the need for a character isolation process.
"Recognition By Two Stage Discriminant Analysis", Proc. SPIE 0754, Optical and Digital Pattern Recognition, (21 August 1987); doi: 10.1117/12.939960; https://doi.org/10.1117/12.939960