Abstract: A fingerprint recognition and retrieval system in which the positions of fingerprint minutiae points and an index number for each minutiae point are recorded in a storage medium. The local ridge flow direction in the vicinity of each minutiae point defined by ridge endings and ridge bifurcations is determined and a generating line is projected at an angle to the local ridge flow direction. The generating line has a length sufficient to span a predetermined number of ridges to each side of each of the minutiae points. Each ridge is traced, in two directions, from the point of crossing of the projected generating line along any crossed ridge line. The first occurring topological event is assigned a type code (T) to the topological event. A topological event code vector is generated for each minutiae comprising an ordered sequence of topological type codes encountered during the tracing and any associated minutiae reference numbers and sets of the vectors are stored in a machine searchable database.

Abstract: Fingerprints are scanned by a scanning system (13). Topological systems for coding and comparing fingerprints are described including a system for recording a description of fingerprints. In a preferred embodiment, a central point of the fingerprint is selected as a center of rotating scan line. The scan line is rotated to different topological characteristics. A code (T) representing the type of irregularity is recorded (16, 17). A measure (M) of the scanning position when encountering the irregularity is made (16, 17). In the case of a rotating scan line the angular cordinate (.theta.) is recorded. The ridge count (R) (16) is also recorded. A list of coordinate sets (T, .theta., R) specifies the topology of a sector. For fragmentary prints similar coordinate sets are generated. A fourth coordinate can be added corresponding to the radial distance (D) (16). A full set of coordinates (T, .theta., R, D) gives a complete topological and spatial description of a fingerprint.

Abstract: Fingerprints are scanned by a scanning system (13). Topological systems for coding and comparing fingerprints are described, including a system for recording a description of fingerprints. In a preferred embodiment, a central point of the fingerprint is selected as a center of rotating scan line. The scan line is rotated to different topological characteristics. A code (T) representing the type of irregularity is recorded (16, 17). A measure (M) of the scanning position when encountering the irregularity is made (16, 17). In the case of a rotating scan line the angular coordinate (.theta.) is recorded as the measure (M) of scanning position. The ridge count (R) (16) is also recorded. A list of coordinate sets (T, .theta., R) specifies the topology of a sector. For fragmentary prints similar coordinate sets are generated. A fourth coordinate can be added corresponding to the radial distance (D) (16). A full set of coordinates (T,.theta.