Patent ID: 7567690

Claim:
A method of determining a living character of a finger of a person carrying a fingerprint using a microprocessor to perform the steps of: (a) making a first measurement of impedance of the finger between two first electrodes with a first predetermined surface area and determining one curve among several curves, each of said several curves satisfying a law of variation of impedance Z measured by the two first electrodes as a function of the surface area (S) of the two first electrodes covered by the fingerprint of a finger at a time t, that is, Z=f Dt (S), said one curve being determined by selecting the curve containing the point with coordinates (first predetermined surface area, measured impedance); (b) making a second measurement of impedance between two second electrodes with a second predetermined surface area different from said first predetermined surface area; and (c) checking that the point defined by the second predetermined surface area and the second impedance measurement values belongs to an area of tolerance situated around said one curve.