Classifying and identifying materials based on permittivity features

Patent metadata

Field	Value
Publication number	US-9341687-B2
Application number	US-201213402538-A
Country	US
Kind code	B2
Filing date	Feb 22, 2012
Priority date	Feb 22, 2011
Publication date	May 17, 2016
Grant date	May 17, 2016

Abstract

Systems and methods are provided for remotely identifying and classifying materials based on their respective complex permittivity features. Materials of interest to be identified in later inspections are cataloged according to their respective complex permittivity features by applying electromagnetic fields to them and determining their complex permittivity features. That library of features is used to compare field measurements taken during an inspection to determine the presence of a material of interest and to identify it.

First claim

What is claimed is:

1. A method for determining the presence, quantity, spatial distribution, and composition of a target material that may be present in an environment, the method comprising:
generating, using a pair of electrodes, a first electromagnetic field having a first set of characteristics, the first electromagnetic field interacting with the target material if present;
measuring a first trans-impedance between the pair of electrodes based on the generated first electromagnetic field;
generating, using the pair of electrodes, a second electromagnetic field having a second set of characteristics, the second electromagnetic field differing from the first electromagnetic field and the second electromagnetic field interacting with the target material if present;
measuring a second trans-impedance between the pair of electrodes based on the generated second electromagnetic field;
perturbing a forward model to compare the first trans-impedance to a first known intrinsic dielectric property of the target material and to compare the second trans-impedance to a second known intrinsic dielectric property of the target material, wherein the first known intrinsic dielectric property of the target material and the second known intrinsic dielectric property of the target material are stored in a library of known intrinsic dielectric properties of a plurality of materials, and the forward model is based on a lumped electrical circuit representation of the environment; and
determining the presence, quantity, and location of the target material within the environment based on the perturbing.

2. The method according to claim 1 , wherein the target material is one or more of explosives, explosive precursors, narcotics, narcotics precursors, chemical and biological agents and their precursors and any other contraband.

3. The method according to claim 1 , wherein the forward model is constructed and arranged so as to represent a two dimensional structure.

4. The method according to claim 1 , wherein the forward model is constructed and arranged so as to represent a three dimensional structure.

5. The method according to claim 1 , wherein at least one of the first and second electromagnetic fields is an AC field.

6. The method according to claim 1 , wherein the second electromagnetic field differs from the first electromagnetic field in frequency.

7. The method according to claim 1 , wherein the second electromagnetic field differs from the first electromagnetic field in a characteristic according to a predetermined program.

8. The method according to claim 1 , wherein the pair of electrodes is part of an electrode array and electrodes of the array are constructed and arranged to be bimodal in that any electrode can operate in a drive mode and in a sense mode of operation.

9. The method according to claim 8 , wherein a temporal and spatial sequence of drive and sense modes of operation occur according to a predetermined protocol or are adaptively modulated to resolve classification and spatial ambiguities.

10. The method according to claim 1 , wherein the second electromagnetic field differs from the first electromagnetic field in field orientation with respect to the target material.

11. The method according to claim 1 , further comprising controlling a characteristic of the second field interactively based on direct comparison of the measured first trans-impedance or based on residuals obtained from processing of the measured first trans-impedance with the forward model, intrinsic dielectric permittivity data stored in the library of known intrinsic dielectric properties, or both.

12. The method according to claim 1 , wherein a goodness or uniqueness of a candidate target material's intrinsic properties is determined by a distance and gradient between a best solution and a next best solution.

13. The method according to claim 1 , wherein the second electromagnetic field differs from the first electromagnetic field in voltage.

14. The method according to claim 1 , wherein the second electromagnetic field differs from the first electromagnetic field in waveform.

15. The method according to claim 1 , further comprising physically or otherwise moving the pair of electrodes interactively to resolve ambiguities in recovered estimates of dielectric properties of the target material being scanned.

16. The method of claim 15 , wherein a subsequent scan is initialized with different characteristics of an excitation electromagnetic field, including without limitation its individual frequencies, frequency band, voltage, waveform, electrode orientation and excitation pattern based on goodness metrics from a previous scan.

17. The method according to claim 16 , wherein the perturbing comprises utilizing a tomographic process.

18. The method according to claim 1 , wherein the perturbing comprises utilizing wavelet analysis to extract information of a dielectric response of the material to excitation.

19. The method according to claim 1 , wherein the determining comprises forming a complex dielectric permittivity data matrix consisting of trans-impedances, capacitance, dielectric constant, conductivity, and other related parameters and then analyzing that data matrix to extract information of a dielectric response of the material to excitation for any arbitrary combination of electrodes.

20. The method according to claim 1 , further comprising:
utilizing a position sensor to locate a position of an object being scanned for the target material with respect to the generating, the measuring the first trans-impedance, the measuring the second trans-impedance, and processing that position information to enhance the analysis of the object being scanned for the target material.

21. The method according to claim 20 , further comprising:
utilizing an optical sensor to identify the object under scan, wherein the identification of the object under scan is used to enhance the estimation of the material composition interior to the material under scan.

22. The method according to claim 1 , further comprising:
inducing, using an ancillary transducer, a particular response in the target material to aid in its differentiation from environmental materials and identification by altering its complex dielectric permittivity in a predictable fashion.

23. The method according to claim 22 , wherein the inducing comprises inducing changes in dielectric properties incidental to an applied magnetic field, acoustic, tone including sub aural tones, temperature change, density change or any other physical property of the target material.

24. The method according to claim 1 , wherein the pair of electrodes comprise N pairs of side by side electrodes that are employed to generate the first and second electromagnetic fields, an active electrode is switched to cause an effective change in distance of target and environmental materials with respect to the pair of electrodes, the resulting change in dielectric permittivity being useful for resolving classification ambiguities, wherein N is an integer greater than 1.

25. The method according to claim 1 , further comprising grounding a partially conducting object under test for the target material for the purpose of determining dielectric permittivity measurements of objects internal to the partially conducting object under test.

26. The method according to claim 25 , wherein the grounding is carried out by mea

Assignees

• Donnangelo Nicholas C
• Mamishev Alexander V
• Kuklinski Walter S
• Mitre Corp

Inventors

• Donnangelo Nicholas C
• Mamishev Alexander V
• Kuklinski Walter S

Classifications

• G01N22/00 Primary

  Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more (G01N3/00 - G01N17/00, G01N24/00 take precedence) · CPC title

• G01R33/16 Primary

  Measuring susceptibility {(G01R33/1238 takes precedence)} · CPC title

• G01R27/00

  Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom · CPC title

• G01N27/02 Primary

  by investigating impedance · CPC title