Live finger detection by four-point measurement of complex impedance

US8195285B2 · kind B2 · utility

Assignee

• IDEX ASA · NO

Inventors

• Orjan Grottem Martinsen · Kongsberg, NO
• Jon Nysaether · Oslo, NO
• Knut Riisnaes · Oslo, NO
• Geir Mostad · Oslo, NO
• Rune Pedersen · Heggedal, NO
• Nicolai W. Christie · Sandefjord, NO
• Sigmund Clausen · Haugesund, NO

Key dates

• Filing date: Dec 6, 2010
• Grant date: Jun 5, 2012
• Expiry date: Dec 6, 2030

Classification

• Technology area (CPC G): Physics
• CPC primary: G06V40/40
• WIPO field: Medical technology
• WIPO sector: Instruments

Abstract

A method and sensor assembly for determining the condition of a structure, especially for confirming if a measured fingerprint is on a live finger, measures characteristics of close to the structure surface. The sensor includes a first pair of current supply electrodes coupled to a current source, providing an electrical current to the skin, at least two pickup electrodes at chosen and different positions relative to the current supply electrodes, at least a first of the pickup electrodes being coupled to an instrument for measuring the voltage between the first pickup electrode and at least one of the pickup or current supply electrodes, storage for a predetermined set of values characterizing a certain condition of the surface, and means for comparing the characteristics from each pickup electrode with the measurements of the other pickup electrodes and with the predetermined set of characteristics for determining the surface condition.