One of the challenges to be overcome in automated fingerprint matching is the construction of a ridge pattern representation that encodes all the relevant information while discarding unwanted detail. Research published recently has shown how this might be achieved by representing the ridges and valleys as a periodic wave. However, deriving such a representation requires assigning a consistent unambiguous direction field to the ridge flow, a task complicated by the presence of singular points in the flow pattern. This disambiguation problem appears to have received very little attention.
We discuss two approaches to this problem — one involving construction of branch cuts, the other using a divide-and-conquer approach, and show how either of these techniques can be used to obtain a consistent flow direction map, which then enables the construction of a phase based representation of the ridge pattern.