Patent ID: 7657066

Claim:
A method using a processor or computer to perform the steps of determining a living character of a finger, of a user carrying a fingerprint and said finger being placed on a fingerprint sensor having an optical system, the method comprising the steps of: (a) measuring an electrical quantity of the finger; (b) taking an image of the fingerprint carried by the finger by means of the optical system; (c) measurement of a particular characteristic of the image, said particular characteristic being selected from the group consisting of: the contrast of the image, the average greyscale of the image, the width of the images of the ridges formed by the said fingerprints, and the average greyscale of the ridges; (d) deducing from the particular characteristic thus measured, a range of values for the electrical quantity of the finger judged in principle acceptable using a relationship established between values of the particular characteristic of the image and the range of said values of the electrical quantity of the finger judged acceptable; and (e) validation of the living character of the finger when the measured electrical quantity belongs to the deduced of values.