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Volume specific characterization of human skin by electrical immittance

a technology of electrical immittance and human skin, which is applied in the field of volume specific immittance measurement system on human skin, can solve the problems of inability to use conventional techniques to measure the described method does not provide the possibility of mapping the characteristics of skin layers through impedance measurements, and the system is impractical

Inactive Publication Date: 2011-03-10
IDEX BIOMETRICS ASA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

Thus it is an object of this invention to provide a method and sensor assembly for measuring characteristics of a surface giving reliable in depth measurements of tissue close to a surface e.g. for live finger confirmations and skin hydration measurements.

Problems solved by technology

Impedance spectroscopy on a well-defined skin volume is hence impossible with conventional techniques, since each frequency will represent a different volume of the skin.
The described method does not provide possibilities to measure map the characteristics of the skin layers through the impedance measurements, e.g. being necessary for confirming if a finger is constituted by living tissue.
In reality this system is impractical and does not take into account the complex part of the impedance signal.
In practice the latter will not give sufficient reliability because it is easy to make false fingers having the same impedance characteristics as required in the application.

Method used

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  • Volume specific characterization of human skin by electrical immittance
  • Volume specific characterization of human skin by electrical immittance
  • Volume specific characterization of human skin by electrical immittance

Examples

Experimental program
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Effect test

example 1

Live Finger Detection

In any electronic system for fingerprint recognition, it will always be important to be able to detect the presence of a dummy finger or a dead (cut-off) finger. While a dummy finger made of a material like e.g. rubber would be rather easy to detect with any one of several different techniques, a thin layer of pattern-imprinted latex covering a real, living finger would be a greater challenge. Such a finger would share most characteristics with a genuine finger, like e.g. temperature, blood pulse, etc. Any conventional electrical immittance measurement (like e.g. the one described in U.S. Pat. No. 6,175,641) will also easily fail if the user e.g. applies some moisture (e.g. saliva) on the latex surface.

In the case of a dead (cut-off) finger, the most obvious differences to a living finger are that a living finger presumably is warmer than a dead one, that a living finger will have blood pulse and that this blood will be oxygenated. Research has furthermore shown...

example 2

Skin Hydration Measurements

Skin function is extremely dependent on the hydration state of the epidermal SC. By monitoring the hydration state of the stratum corneum, an early diagnosis of non-visible skin conditions may be accomplished. In addition, measurement of SC hydration is also important in the evaluation of the effects of topical formulations like e.g. skin moisturisers.

We have earlier developed an electrical method for skin hydration measurements, based on low frequency susceptance measurements (see e.g. U.S. Pat. No. 5,738,107). There is reason to believe that multi-frequency measurements on SC will provide additional information that may be useful in the assessment of SC hydration and condition, but the fact that multi-frequency measurements on pure SC in vivo has been impossible to accomplish until now, has prevented further investigation in this area.

The invention described here will thus enable focused multi-frequency measurements on selected skin layers like e.g. the ...

example 3

Localized Measurement of Exogenic Electrodermal Response

The sweat activity on palmar and plantar skin sites is very sensitive to psychological stimuli or conditions. The changes are easily detected by means of electrical measurements and since the sweat ducts are predominantly resistive, a low frequency or dc conductance measurement is typically used in electrodermal response (EDR) measurements.

The lie detector is perhaps the most commonly recognized instrument where the electrical detection of EDR activity is utilized. There are, however, several other applications for such measurements, mainly within the two categories; neurological diseases or psychophysiological measurements. Examples of the first category are neuropathies (e.g. diabetes), nerve lesions, depressions and anxiety. The latter category may include emotional disorders, pain assessment and lie-detection.

EDR measurements are conventionally performed with skin electrodes that are much larger than the area typically occu...

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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.

Description

FIELD OF THE INVENTIONThis invention relates to a sensor assembly and a method for measuring characteristics of a surface, preferably skin, and more specifically a system for volume specific immittance measurements on human skin. The measurements are done in order to characterize the physiological conditions of the specific skin volume, like e.g. viability, moisture content, structure, composition, etc. Examples of possible applications for this invention are for life detection in fingerprint recognition systems, depth specific skin hydration measurements or detection of electrodermal response localized to discrete sweat duct orifices.BACKGROUND OF THE INVENTIONMeasurement depth for bioimpedance measurements on skin will in general greatly depend on the frequency of the applied signal—higher frequency will mean measurements at a greater depth in the skin, as is discussed in Martinsen O. G., Grimnes S., Haug E.: Measuring depth depends on frequency in electrical skin impedance measur...

Claims

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Application Information

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IPC IPC(8): A61B5/053A61B5/103A61B5/05A61B5/117
CPCA61B5/0531A61B5/442G06K9/00906A61B5/6838A61B5/6826G06V40/45
Inventor MARTINSEN, ORJAN G.GRIMNES, SVERRE
Owner IDEX BIOMETRICS ASA
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