Material classification apparatus and method

• US 6,545,945 B2
• Filed: 02/26/2001
• Issued: 04/08/2003
• Est. Priority Date: 02/26/2001
• Status: Expired due to Fees

• Current Assignee: Ocean Data Equipment Corporation
• Original Assignee: Ocean Data Equipment Corporation
• Inventors: Caulfield, David D.
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US09/791,671
• Publication Number:
  US 20020159334A1
• Time in Patent Office: 771 Days
• Field of Search: 367/87, 367/124, 367/135, 342/22, 342/189, 342/195
• US Class Current: 367/87
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 29/4418 with a model, e.g. best-fit, regression analysis
• CPC Class Codes: G01N 29/4436 with a reference signal amplitude comparison G01N29/48
• CPC Class Codes: G01N 29/4445 Classification of defects
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01V 1/001 Acoustic presence detection
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

The present invention provides signification improvements over the apparatus and method disclosed by U.S. Pat. No. 4,922,467. The invention provides an apparatus for material classification and substance identification of an object contained within an enclosure, or buried beneath the ground. The improvements to the present invention include the use of a source of either electromagnetic or acoustic energy, and electromagnetic or acoustic energy receivers, as appropriate. In addition, the present invention discloses the use of energy pulses of differing frequencies, such that the signal processor can compute the rate of change of energy absorption of the substance, as a function of frequency (dα/df). In this way, the apparatus permits the formulation of a highly detailed and accurate object signature, which can be compared with a database of known object signatures for exact substance identification.

Claims

1. An apparatus for detecting the substance of an object contained within an enclosure, said apparatus comprising:

electromagnetic or acoustic energy transmitter means for transmitting at least two pulses of electromagnetic or acoustic energy at a first side of said enclosure, said at least two pulses having differing frequencies;

first electromagnetic or acoustic energy receiver means for receiving electromagnetic or acoustic energy that has been reflected from the object to produce at least two reflected electromagnetic or acoustic energy signals;

second electromagnetic or acoustic energy receiver means for receiving electromagnetic or acoustic energy that has been transmitted or refracted through said object to produce at least two transmitted or refracted electromagnetic or acoustic energy signals;

signal processor means connected to said transmitter means and to said first and second receiver means for producing an object signature, wherein said object signature is generated by computing energy absorption for each frequency and calculating a rate of change of said energy absorption as a function of frequency; and

comparator means for comparing said object signature with signatures of known objects to determine the substance of said object.

2. The apparatus of claim 1, further including display means for providing an indication of the substance of the object.

3. The apparatus of claim 2, wherein said enclosure is a box and wherein said first electromagnetic or acoustic energy receiver means is located on said first side and said second electromagnetic or acoustic energy receiver means is located on a side of the box opposite said first side.

4. The apparatus of claim 2, wherein said enclosure is the earth and said first and second electromagnetic or acoustic energy receiver means are located on said first side, said second electromagnetic or acoustic energy receiver means being spaced further from said electromagnetic or acoustic energy transmitter means than said first electromagnetic or acoustic energy receiver means.

5. The apparatus of claim 3 or 4, wherein said signal processor means further processes said reflected electromagnetic or acoustic energy signals, and said transmitted or refracted electromagnetic or acoustic energy signals, to calculate an electromagnetic or acoustic impedance, an electromagnetic or acoustic velocity and a porosity of said object, wherein said object signature is further derived from the electromagnetic or acoustic impedance, the electromagnetic or acoustic velocity and the porosity of said object.

6. An apparatus according to claim 5, comprising at least one further electromagnetic or acoustic energy receiver means, for producing at least two further electromagnetic or acoustic energy signals, wherein each of said at least one further electromagnetic or acoustic energy receiver means is positioned to receive energy at a different angle relative to the energy transmitted at the object from the electromagnetic or acoustic energy transmitter means, said object signature being further derived from processing said at least two further electromagnetic or acoustic energy signals by said signal processor.

7. An apparatus for detecting the substance of an object within an enclosure, said apparatus comprising:

electromagnetic or acoustic energy transmitter means for transmitting at least two pulses of electromagnetic or acoustic energy at a first side of said enclosure, said at least two pulses having different frequencies;

movable electromagnetic or acoustic energy receiver means, movable about said object to receive reflected, transmitted or refracted energy in at least two positions relative to the energy transmitted at said object from the electromagnetic or acoustic energy transmitter means, said movable electromagnetic or acoustic energy receiver means producing at least two electromagnetic or acoustic energy signals at each of said at least two positions;

signal processor means connected to said transmitter means and to said movable receiver means for producing an object signature, wherein said object signature is generated by computing energy absorption for each frequency and calculating a rate of change of absorption as a function of frequency; and

comparator means for comparing said object signature with signatures of known objects to determine the substance of said object.

8. An apparatus for detecting the substance of an object contained within an enclosure, said apparatus comprising:

electromagnetic energy transmitter means for transmitting a pulse of electromagnetic energy at a first side of said enclosure;

first electromagnetic energy receiver means for receiving electromagnetic energy that has been reflected from the object to produce a reflected electromagnetic energy signal;

second electromagnetic energy receiver means for receiving electromagnetic energy that has been transmitted or refracted through said object to produce a transmitted or refracted electromagnetic energy signal;

signal processor means connected to said transmitter means and to said first and second receiver means, said signal processor means processing said transmitted pulse of electromagnetic energy, said reflected electromagnetic energy signal, and said refracted or transmitted electromagnetic energy signal to produce an object signature indicative of said object; and

comparator means for comparing said object signature with signatures of known objects to determine the substance of said object.

9. The apparatus of claim 8, further including display means for providing an indication of the substance of the object.

10. The apparatus of claim 8, wherein said enclosure is a box and wherein said first electromagnetic energy receiver means is located on said first side and said second electromagnetic energy receiver means is located on a side of the box opposite to said first side.

11. The apparatus of claim 9, wherein said enclosure is the earth and said first and second electromagnetic energy receiver means are located on said first side, said second electromagnetic energy receiver means being spaced further from said electromagnetic energy transmitter means than said first electromagnetic energy receiver means.

12. The apparatus of claim 10 or 11, wherein said signal processor means processes said reflected electromagnetic energy signal and said transmitted or refracted electromagnetic energy signal, to calculate an electromagnetic impedance, an electromagnetic absorption, an electromagnetic velocity and a porosity of said object, wherein said object signature of said object is derived from the electromagnetic impedance, the electromagnetic absorption, the electromagnetic velocity and the porosity of said object.

13. An apparatus according to claim 12, comprising at least one further electromagnetic energy receiver means, for producing at least one further electromagnetic energy signal, wherein each of said at least one further electromagnetic energy receiver means is positioned to receive energy at a different angle relative to the energy transmitted at the object from the electromagnetic energy transmitter means, said object signature being further derived from processing said at least one further electromagnetic energy signal by said signal processor.

14. An apparatus for detecting the substance of an object within an enclosure, said apparatus comprising:

electromagnetic energy transmitter means for transmitting a pulse of electromagnetic energy at a first side of said enclosure;

movable electromagnetic energy receiver means movable about said object to receive reflected, transmitted or refracted energy in at least two positions relative to the pulse transmitted at said object from the electromagnetic energy transmitter means, said movable electromagnetic energy receiver means producing an electromagnetic energy signal in at least said at least two positions;

signal processor means connected to said transmitter means and to said movable receiver means said signal processor means processing said transmitted pulse of electromagnetic energy, and said reflected or refracted electromagnetic energy signals to produce an object signature indicative of said object; and

comparator means for comparing said object signature with signatures of known objects to determine the substance of said object.

15. A method of determining the substance of an object located within an enclosure, the method comprising the steps of:

applying at least two pulses of electromagnetic or acoustic energy each of known intensities and differing frequencies to a first side of the enclosure and the object in the enclosure;

detecting at least two pulses of reflected electromagnetic or acoustic energy reflected from a surface of the object to provide reflected electromagnetic or acoustic energy signals;

detecting at least two pulses of transmitted or refracted electromagnetic or acoustic energy transmitted or refracted through the object to provide transmitted or refracted electromagnetic or acoustic energy signals;

processing said reflected and transmitted or refracted electromagnetic or acoustic energy signals to produce an object signature, said object signature comprising the electromagnetic or acoustic energy absorption of the substance as a function of frequency; and

comparing the object signature so obtained with signatures of known objects to determine the substance of said object.

16. The method of claim 15, wherein the step of processing further includes the step of calculating an electromagnetic or acoustic impedance, an electromagnetic or acoustic velocity, and a porosity of the object, wherein the object signature is further derived from the electromagnetic or acoustic impedance, the electromagnetic or acoustic velocity and the porosity of the object.

17. The method of claim 15, wherein the enclosure is a box and the reflected electromagnetic or acoustic energy is detected on said first side of the enclosure and the transmitted or refracted electromagnetic or acoustic energy is detected on a side of the enclosure opposite said first side.

18. The method of claim 16, wherein the enclosure is a box and the reflected electromagnetic or acoustic energy is detected on said first side of the enclosure and the transmitted or refracted electromagnetic or acoustic energy is detected on a side of the enclosure opposite said first side.

19. The method of claim 15, wherein the enclosure is the earth and the reflected electromagnetic or acoustic energy and the transmitted or refracted electromagnetic or acoustic energy is detected on said first side of the enclosure and the transmitted or refracted electromagnetic or acoustic energy is detected at a position further away from the object than the reflected electromagnetic or acoustic energy is detected.

20. The method of claim 16, wherein the enclosure is the earth and the reflected electromagnetic or acoustic energy and the transmitted or refracted electromagnetic or acoustic energy is detected on said first side of the enclosure and the transmitted or refracted electromagnetic or acoustic energy is detected at a position further away from the object than the reflected electromagnetic or acoustic energy is detected.

21. A method of determining the substance of an object located within an enclosure, the method comprising the steps of:

applying electromagnetic energy to a first side of the enclosure and the object in the enclosure;

detecting the reflected electromagnetic energy reflected from a surface of the object to provide a reflected electromagnetic energy signal;

detecting the transmitted or refracted electromagnetic energy transmitted or refracted through the object to provide a transmitted or refracted electromagnetic energy signal;

processing said reflected and transmitted or refracted electromagnetic energy signals to produce an object signature; and

comparing the object signature so obtained with signatures of known objects to determine the substance of said object.

22. The method of claim 21, wherein the step of processing further includes the step of calculating the electromagnetic impedance, the electromagnetic absorption, the electromagnetic velocity, and the porosity of the object, the object signature being further derived from the electromagnetic impedance, the electromagnetic absorption, the electromagnetic velocity and the porosity of said object.

23. The method of claim 21, wherein the enclosure is a box and the reflected electromagnetic energy is detected on said first side of the enclosure and the transmitted or refracted electromagnetic energy is detected on a side of the enclosure opposite said first side.

24. The method of claim 22, wherein the enclosure is a box and the reflected electromagnetic energy is detected on said first side of the enclosure and the transmitted or refracted electromagnetic energy is detected on a side of the enclosure opposite said first side.

25. The method of claim 21, wherein the enclosure is the earth and the reflected electromagnetic energy and the transmitted or refracted electromagnetic energy are detected on said first side of the enclosure and the transmitted or refracted electromagnetic energy is detected at a position further away from the object than the reflected electromagnetic energy is detected.

26. The method of claim 22, wherein the enclosure is the earth and the reflected electromagnetic energy and the transmitted or refracted electromagnetic energy are detected on said first side of the enclosure and the transmitted or refracted electromagnetic energy is detected at a position further away from the object than the reflected electromagnetic energy is detected.