SIGNAL PROCESSING APPROACH TO OPTIMUM PREPROCESSING FOR ON-LINE RECOGNITION OF HANDWRITTEN JAPANESE CHARACTERS.

Tablet digitizers, they are expected to be used as the input device for handwritten characters and drawings. As the preprocesing for the point coordinate sequence read from a tablet, only empirical methods have been applied. This paper discusses the preprocessing from the viewpoint of signal processing, and a quantitative evaluation was made for the following two points: (1) directional stability of the preprocessed coordinate sequence; and (2) follow-up (fidelity) of the preprocesses point sequence to the original point sequence. A performance superior to the traditional methods was obtaned by using the following four phases; (1) Adaptive sampling, where sharp corners are stresses, while the sampling points are set uniformly for slow pen movement; (2) interpolation, where the point interval is made uniform for fast pen movement; (3) smoothing by the moving-average filter; and (4) thinning to eliminate redundant points.