Robust biometric feature extraction with and without reference point

Abstract

A basic idea of the present invention is to selectively employ one of at least two different feature extraction processes when generating a biometric template of an individual. An individual offers a physiological property, such as a fingerprint, an iris, an ear, a face, etc., from which biometric data can be derived, to a sensor of an enrollment authority. In the following, the property to be discussed will be fingerprints, even though any suitable biometric property may be used. From the fingerprint, a positional reference point of the biometric data is derived. The derivation of the positional reference point may be accomplished using any appropriate method out of a number of known methods. Such a reference point could be the location of a core, a delta, a weighted average of minutiae coordinates, or alike. Typically, the reference point includes a core of a fingerprint expressed as a three-dimensional coordinate denoted by means of x, y, and angle α. A contribution indicator is calculated for the derived positional reference point, and it is determined whether the derived positional reference point can be considered reliable. Depending on the reliability of the derived reference point, one of the two different feature extraction processes is selected; either the first feature set is extracted using a method which is invariant of the derived reference point, or a method is used taking into account the derived reference point. The better the estimation of the reference point is, the more reliable the reference point-dependent extraction method is. Finally, the biometric template is generated using the extracted first feature set.