Characteristic discriminating landmine hand prodder

• US 5,754,494 A
• Filed: 12/05/1996
• Issued: 05/19/1998
• Est. Priority Date: 12/05/1996
• Status: Expired due to Fees

• Current Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Original Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Inventors: Gallagher, Patrick J.
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US08/761,211
• Time in Patent Office: 530 Days
• Field of Search: 367/87, 367/138, 367/135, 89/1.13, 73/591, 73/642, 73/644
• US Class Current: 367/87
• CPC Class Codes: F41H 11/12 Means for clearing land minefields; Systems specially adapted for detection of landmines
• CPC Class Codes: G01H 15/00 Measuring mechanical or acoustic impedance
• CPC Class Codes: G01V 1/001 Acoustic presence detection

Abstract

A hand-held prodder capable of distinguishing inert rock from potentially hazardous landmines or other unknown objects. The prodder comprises a rod which is placed into contact with an object. A high frequency acoustic or incident wave is introduced into rod and travels along the rod to the object where it is reflected back towards the piezoelectric crystal. The piezoelectric crystal converts the reflected wave to an electric signal and a signal processor determines values representative of the frequency-time-amplitude characteristics of the object. Different materials exhibit different mechanical impedances and frequency damping characteristics. By comparing reflected wave characteristics to pre-determined characteristics for known materials, inert rocks and potentially hazardous plastic or metallic objects are distinguishable. Visual or audible signals inform the user whether rock (safe) or unidentified or known hazardous object were contacted.

Claims

1. A prodding rod having a driver end and a sensing end for contacting an object of unknown material comprising:

means at the support end for imparting mechanical energy into the rod which travels as an incident elastic wave from the driver end towards the sensing end and reflects from the object as a reflected elastic wave traveling towards the driver end;

means for analyzing the reflected elastic wave for its acoustical characteristics and emitting electrical signals indicative of the acoustical characteristics of the object; and

means for processing the signals for comparing the object'"'"'s acoustic characteristics against stored values representative of the acoustic characteristics of known materials so as to categorize the object'"'"'s material.

2. A prodding rod as recited in claim 1 wherein the energy imparting means is a piezoelectric crystal.

3. A prodding rod as recited in claim 1 wherein the means for detecting the acoustic characteristic of the reflected wave is a piezoelectric crystal.

4. A prodding rod as recited in claim 1 wherein the means for processing the detected acoustic characteristics comprises:

a signal processor which Fast Fourier Transforms reflected wave signals into frequency-time-amplitude values and compares that data against stored frequency-time-amplitude values obtained from use of the prodding rod with materials having known acoustical characteristics so that the nature of the object'"'"'s material can be identified.

5. A hand-held, non-magnetic prodding rod used for the detection of land mines, the rod having a driver end and a sensing end for contacting an object of unknown material comprising:

means at the support end for imparting mechanical energy into the rod which travels as an incident elastic wave from the driver end towards the sensing end and reflects from the object as a reflected elastic wave traveling towards the driver end;

means for analyzing the reflected elastic wave for its acoustical characteristics and emitting electrical signals indicative of the acoustical characteristics of the object; and

means for processing the signals for comparing the object'"'"'s acoustic characteristics against stored values representative of the acoustic characteristics of known materials so as to categorize the object'"'"'s material.

6. A landmine prodding rod as recited in claim 5 wherein the energy imparting means and the acoustic characteristic detecting means are piezoelectric crystals.

7. A landmine prodding rod as recited in claim 5 further comprising a visual or audible signal which is representative of the category the object is determined to be in.

8. A landmine prodding rod as recited in claim 5 further comprising batteries for powering the energy imparting means and signal processing and comparing means.

9. A method of determining the nature of the material of an object prodded by a rod having first and second ends, comprising the steps of:

(a) placing the second end of the rod in contact with the object;

(b) imparting an incident elastic wave into the first end of the rod so that it travels longitudinally along the rod to the second end where the wave reflects to form a reflected wave travelling back towards the first end;

(c) measuring the acoustic characteristic of the reflected wave and emitting electrical signals indicative thereof; and

(d) processing the signals so as to establish measurements characteristic of the material of the object.

10. The method recited in claim 9 further comprising comparing the processed characteristics against stored characteristics of known materials so as to categorize the object'"'"'s material.

11. The method recited in claim 9 wherein the material characteristics for known materials are measured by:

calibrating the prodder by first performing steps (a)-(d) of the method on materials of a known nature and storing the measured characteristics; and

comparing the processed characteristics against the stored characteristics of known materials so as to categorize the object'"'"'s material.

12. The method recited in claim 9 wherein the prodder emits a unique visual or audible signal representative of the category the object is determined to be in.

13. The method recited in claim 9 further comprising:

(e) calibrating the prodder by first performing steps (a)-(d) of the method on materials of a known nature to measure gross characteristics representative of both the known material and the rod;

(f) performing steps (a)-(d) of the method without contacting an object at all to measure baseline characteristics of the rod alone;

(g) extracting the baseline from the gross characteristics so as to establish measurements of the characteristics of the known material alone;

(h) performing steps (a)-(d) of the method on an object of unknown characteristics to measure gross characteristics being representative of both the unknown material and the rod;

(i) extracting the baseline characteristics of the rod so as to establish measurement of the characteristics of the unknown material alone; and

(j) comparing the extracted characteristics of the unknown object and known objects so as to categorize the object'"'"'s material.

14. The method recited in claim 12 wherein the prodder emits a unique visual or audible signal representative of the category the object is determined to be in.

15. The method recited in claim 9 wherein the prodder is used to determine the nature of objects which are suspect as being landmines and accordingly emits a binary visual or audible signal to indicate whether the material of the object is determined to be in the category of either a non-hazardous rock or of other material of unknown hazard.