Fingerprint Identification - Feature Extraction, Matching, and Database Search

This chapter discusses the estimation of a high resolution directional field of fingerprints. Traditional methods are compared to a new method, based on principal component analysis. The method is adapted to compute the directional field and its coherence in each pixel. By combining a non-uniform window with efficient filter techniques, the method can also be used to estimate a block directional field with higher accuracy, without being computational much more complex. Parts of this chapter have been published in [Baz00a] and [Baz02d]. 18 CHAPTER 2. DIRECTIONAL FIELD ESTIMATION (a) Fingerprint (b) Directional field Figure 2.1: Examples of a fingerprint, and its directional field. The orientation of the small lines represents the estimated direction, while the length of the lines gives an indication of the certainty.