The invention relates to a method and an apparatus for the identification of not-enrolled fingerprints. Numerous methods and apparatuses are known, which allow the identification of a fingerprint. Generally the finger is pressed against a suitable optical device for producing contrast and e.g. by means of prisms and the inhibited total reflection principle, an image of the skin lines is produced. For example a digital grey value image is recorded, which is converted into a binary image and compressed by means of suitable algorithms to a biometric pattern with a relatively small storage requirement, which can then be compared with stored finger patterns of an associated data bank for identification purposes. The identification of fingerprints by enrolled finger line images is well established and proven in the police field. However, an increasing number of non-police uses require not-enrolled fingerprints. Thus, in most cases it is not possible or desirable to prescribe the enrolling of the fingerprint. In fact in many cases it is legally forbidden. In the case of not-enrolled fingerprints, which are required for normal applications, a very serious problem arises. Thus, if the orientation of the finger with respect to its longitudinal axis, i.e. a twisting or turning of the finger relative to the image recording surface occurs, then completely different partial image quantities of a complete enrolled fingerprint are identified, as a function of the twisting or rotation angle of the finger applied. In an extreme case this can mean that the identified partial image quantity of the surface of the finger on rotating the finger about its axis by e.g. +20.degree. and -20.degree. leads to a common image section quantity of these positions, which makes it impossible in practice to identify with the mathematical method used as a basis the person in question with an adequate accuracy using the differently applied finger. Thus, the information still contained in the common image section quantity can be too small to allow a reliable identification.
The problem of the invention is to give a method and an apparatus enabling this serious difficulty to be overcome and which allow a considerably increased identification reliability and accuracy and this is to be performable with a relatively small storage requirement for a significant pattern.