PREPROCESSING MEANS FOR USE IN A PATTERN CLASSIFICATION SYSTEM

A method for recognizing an object by processing reference feature vectors a collection of reference feature vectors is generated; each representing a reference pattern that belongs to one of a plurality of predefined classes. Each class has associated all reference feature vectors representing reference patterns belonging to that class. For a selected class, an associated hierarchy of one or more sets of possibility regions is generated, wherein for a selected set in the hierarchy the number of possibility regions in said selected set is significantly less than the number of reference feature vectors belonging to said selected class, and such that each reference feature vector belonging to said selected class is contained in at least one possibility region of said selected set, and such that each possibility region of said selected set contains relatively few reference feature vectors not belonging to said selected class.