1. Field of the Invention
The invention relates to an apparatus and method for the classification of a pattern, for example on a banknote or a coin.
2. Description of the Prior Art
Such an apparatus is advantageously used in automatic sales machines, automatic money changing machines and the like, where classification is effected on the one hand in accordance with value, for example as between one, two and five dollar notes, and/or on the other hand as between originals and copies (forgeries).
It is known for intensity values of electromagnetic radiation reflected from image portions of a test item to be processed in such a way that the test item can be compared to a pixel matrix (European patent EP 0 067 898 B1) of an original, or that differences in relation to an original are printed out and evaluated, in the form of an angle between two n-dimensional vectors (German patent application DE 30 40 963 A1) or as a cross-correlation function (European patent application EP 0 084 137 A2).
It is also known (Swiss patent application No. 640 433 A5) for various physical measurement parameters of a test item to be respectively compared to corresponding stored limit values substantially independently of each other, and, after successful classification, to improve the limit values by means of the measurement parameters of the accepted test item.
In addition various attempts at providing learning or self-adapting classifiers are known (H. Niemann: Klassifikation von Mustern (Classification of patterns)--Berlin, Heidelberg, Tokyo, Springer 1983) in which the class ranges are continually altered with classified patterns and which in the classification operation require a considerable amount of computing expenditure, which in practical use can result in unacceptable response times.