Image filter design for fingerprint enhancement

Fingerprint filter design and a method of enhancing fingerprint image are discussed. Two distinct filters in the Fourier domain are designed, a frequency filter corresponding to ridge frequencies and a direction filter corresponding to ridge directions on the basis of fingerprint ridge properties. An energy function for selecting image features, i.e. frequencies and directions, is defined by intensities of images obtained with the above filters and a measure of smoothness of the features. Using the image features which minimize the energy function, an enhanced image is produced from the filtered images. This image enhancement method is applied to fingerprint matching. In experiments with rolled prints, it is shown that the matching error rate is reduced by about two-thirds compared with Asai´s method