Volume specific characterization of human skin by electrical immittance

Abstract

This invention relates to a sensor assembly and a method for measuring characteristics of a surface, preferably skin, comprising a first pair of current supply electrodes coupled to a current source, providing an electrical current to the skin, at least one pickup electrodes at chosen positions relative to the current supply electrodes, at least a first of said pickup electrodes being coupled to an instrument for measuring the voltage between said first pickup electrode and at least one of the pickup or current supply electrodes.

1 . A sensor assembly for measuring characteristics of a surface, preferably skin, comprising:
 a first pair of current supply electrodes coupled to a current source, providing an electrical current to the skin; and   at least one first pickup electrode at a chosen position relative to the current supply electrodes being coupled to an instrument for measuring the voltage between the first pickup electrode and at least one of said current supplying electrodes.   
     
     
         2 . The sensor assembly according to  claim 1 , wherein the supplied current is oscillating within a chosen frequency range. 
     
     
         3 . The sensor assembly according to  claim 2 , wherein the chosen frequency range is in the range of 10-1000 kHz. 
     
     
         4 . The sensor assembly according to  claim 2 , wherein the current is oscillating at 100 kHz. 
     
     
         5 . The sensor assembly according to  claim 1 , wherein the first pickup electrode is positioned at a distance from the first current supply electrode being less than the distance between the current supply electrodes. 
     
     
         6 . The sensor assembly according to  claim 5 , wherein the distance is less than 1 mm. 
     
     
         7 . A system for inspecting whether an object consists of living skin, comprising:
 a sensor assembly for measuring electrical characteristics of a stratum corneum and living skin, said sensor assembly including:   two current supply electrodes configured to apply an alternating current or voltage with at least one frequency to the skin therebetween;   a first electrode positioned at a chosen distance from one of said current supply electrodes and configured to measure a complex voltage as a function of frequency between said first electrode and said one of said current supply electrodes; and   a second electrode positioned at a larger distance from said one of said current supply electrode than said first electrode and configured to measuring a complex voltage between said first electrode and said second electrode,   wherein said sensor assembly is configured to calculate an immittance for said stratum corneum and living skin based on said voltage measurements, and use said immittance as a basis for comparing with corresponding, known characteristics of a live, or possibly a dead, finger.   
     
     
         8 . The system of  claim 7 , wherein said comparison of electrical characteristics comprises comparing dispersion of resistivity for at least one skin layer. 
     
     
         9 . The system of  claim 7 , wherein said comparing of electrical characteristics comprises comparing dispersion of permittivity for at least one skin layer 
     
     
         10 . The system of  claim 7 , wherein said comparing of electrical characteristics comprises comparing resistivity for at least one skin layer. 
     
     
         11 . The system of  claim 7 , wherein said comparing of electrical characteristics comprises comparing relative permittivity for at least one skin layer. 
     
     
         12 . The system of  claim 7  wherein the distance between said first current supply electrode and said first electrode is less than 1 mm.