On-line Adaptation in Recognition of Handwritten Alphanumeric Characters

We have developed an adaptive on-line recognizer suitable for recognizing isolated alphanumeric characters. It is based on the k nearest neighbor rule. Various dissimilarity measures, all based on dynamic time warping (DTW), have been studied. The main focus of the work is on on-line adaptation. The adaptation is performed by modifying the prototype set of the classifier according to its recognition performance and the user’s writing style. These adaptations include: 1) adding new prototypes, 2) inactivating confusing prototypes, and 3) reshaping existing prototypes. The reshaping algorithm is based on Learning Vector Quantization (LVQ). The writers are allowed to use their own natural style of writing, and the adaptation is carried out during normal use in a self-supervised fashion and thus remains otherwise unnoticed by the user.