Terahertz imaging non-destructive inspection systems and methods

• US 20070090294A1
• Filed: 10/24/2005
• Published: 04/26/2007
• Est. Priority Date: 10/24/2005
• Status: Abandoned Application

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Safai, Morteza, Georgeson, Gary
• Application Number:
  US11/257,370
• Publication Number:
  US 20070090294A1
• Time in Patent Office: Days
• US Class Current: 250/341.8
• CPC Class Codes: G01N 21/3563 for analysing solids; Preparation of samples therefor
• CPC Class Codes: G01N 21/3581 using far infrared light; using Terahertz radiation
• CPC Class Codes: G01N 21/91 using penetration of dyes, e.g. fluorescent ink
• CPC Class Codes: G01N 2201/0221 Portable; cableless; compact; hand-held

Abstract

Provided are systems and methods using terahertz imaging techniques for performing non-destructive inspection of a structure for detection of surface recesses. A method may involve applying a terahertz-frequency absorbing liquid to a surface of the structure, whereby the liquid will naturally tend to flow into surface recesses present in the surface of the structure, removing excess liquid from the surface of the structure which has not penetrated into existing recesses in the surface of the structure, and, after excess liquid has been removed from the surface of the structure, transmitting electromagnetic radiation in the terahertz frequency range toward the surface of the structure and detecting reflections of radiation which is not absorbed at the surface of the structure. A system may use a liquid applicator, excess liquid remover, a terahertz transmitter, and a terahertz receiver to perform a terahertz imaging non-destructive inspection operation.

Claims

1. A method of inspection an aircraft structure, the method comprising:

applying a liquid to a surface of the aircraft structure such that the liquid is able to penetrate recesses in the surface of the aircraft structure, the liquid being absorbent of electromagnetic radiation in a terahertz frequency range; and

transmitting electromagnetic radiation in the terahertz frequency range toward the surface of the aircraft structure.

2. The method of claim 1, wherein the step of applying the liquid to the surface of the aircraft structure comprises applying the liquid to a composite aircraft structure.

3. The method of claim 1, further comprising the step of removing excess liquid from the surface of the aircraft structure which has not penetrated recesses in the surface of the aircraft structure.

4. The method of claim 1, further comprising the step of receiving a reflection of electromagnetic radiation in the terahertz frequency range from the surface of the aircraft structure.

5. A method of inspecting an aircraft structure, the method comprising:

transmitting electromagnetic radiation in a terahertz frequency range toward a surface of the aircraft structure, the surface having a terahertz-absorbent liquid received in recesses in the structure; and

receiving electromagnetic radiation in the terahertz frequency range reflected by the aircraft structure.

6. The method of claim 5, wherein the step of transmitting electromagnetic radiation in the terahertz frequency range comprises transmitting electromagnetic radiation in the frequency range from 100 GHz to 2.3 THz.

7. The method of claim 5, wherein the step of transmitting electromagnetic radiation in the terahertz frequency range comprises transmitting electromagnetic radiation in the frequency range from 100 GHz to 30 THz.

8. The method of claim 5,further comprising the step of creating a visual image of absorption of transmitted radiation on the surface of the structure.

9. A method of inspecting a structure comprising:

applying a liquid to a surface of the structure such that the liquid is able to penetrate into existing surface recesses in the surface of the structure, the liquid having an absorbency that is different than the structure for electromagnetic radiation in a terahertz frequency range; and

transmitting electromagnetic radiation in the terahertz frequency range toward the surface of the structure.

10. The method of claim 9, further comprising the step of removing excess liquid from the surface of the structure which has not penetrated into existing recesses in the surface of the structure.

11. The method of claim 9, further comprising the step of receiving a reflection of electromagnetic radiation in the terahertz frequency range from the surface of the structure.

12. The method of claim 9, wherein the step of applying a liquid to the surface of the structure comprises applying water to the surface of the structure.

13. The method of claim 12, wherein the step of transmitting electromagnetic radiation in the terahertz frequency range comprises transmitting electromagnetic radiation in the frequency range from 100 GHz to 2.3 THz.

14. The method of claim 9, wherein applying a liquid to the surface of the structure comprises spraying the liquid onto the surface of the structure.

15. The method of claim 9, wherein the step of removing excess liquid comprises wiping the surface of the structure.

16. The method of claim 9, wherein the step of removing excess liquid comprises allowing excess liquid to evaporate from the surface of the structure.

17. The method of claim 9, wherein the step of removing excess liquid comprises directing heat towards the surface of the structure to accelerate evaporation of excess liquid from the surface of the structure.

18. The method of claim 9, wherein the step of removing excess liquid comprises directing heated air towards the surface of the structure to accelerate evaporation of excess liquid from the surface of the structure.

19. The method of claim 9, wherein the step of transmitting electromagnetic radiation in the terahertz frequency range comprises transmitting electromagnetic radiation in the frequency range from 100 GHz to 30 THz.

20. The method of claim 9, further comprising the step of creating a visual image of absorption of transmitted radiation on the surface of the structure.

21. The method of claim 20, wherein the step of creating a visual image comprises creating a two dimensional representation of the surface of the structure.

22. The method of claim 9, further comprising the step of creating a visual image of reflection of transmitted radiation from the surface of the structure.

23. The method of claim 9, further comprising the steps of:

scanning at least a portion of the surface of the structure by transmitting electromagnetic radiation in the terahertz frequency range toward the portion of the surface of the structure and receiving the reflection of radiation from the portion of the surface of the structure; and

creating a visual image of absorption of transmitted radiation on the surface of the structure.

24. The method of claim 23, wherein the step of scanning at least a portion of the structure comprises automatically correlating the position of transmitted and received radiation in relation to the surface of the structure.

25. The method of claim 23, wherein the step of creating a visual image comprises creating a two dimensional representation of the scanning of the surface of the structure.

26. A system for inspecting a structure which includes a terahertz-absorbent liquid received in recesses of the structure, the system comprising:

a terahertz electromagnetic radiation system configured to;

transmit electromagnetic radiation in a terahertz frequency range toward a surface of the structure for absorption by the liquid;

receive radiation reflected by the structure; and

generate a signal indicative of the received radiation; and

a computer in communication with the terahertz electromagnetic radiation system and configured to process the generated signal from the terahertz electromagnetic radiation system.

27. The system of claim 26, wherein the terahertz electromagnetic system is further configured to transmit and receive electromagnetic radiation in at least a portion of the frequency range from 100 GHz to 30 THz.

28. The system of claim 26, wherein the computer is further configured to create a visual image of absorption of transmitted radiation on the surface of the structure.

29. The system of claim 26, further comprising:

a liquid applicator for applying the liquid to the surface of the structure to permit the liquid to be received in recesses of the structure;

an excess liquid remover for removing excess liquid from the surface of the structure;

wherein the terahertz electromagnetic radiation system comprises;

a terahertz transmitter for transmitting the electromagnetic radiation in the terahertz frequency range toward the surface of the structure; and

a terahertz receiver for receiving radiation reflected by the structure, wherein the terahertz transmitter is capable of transmitting and the terahertz receiver is capable of receiving electromagnetic radiation of the same frequency.

30. The system of claim 29, wherein the excess liquid remover comprises a heated air blower for blowing heated air towards the surface of the structure for accelerating evaporating of excess liquid from the surface of the structure.

31. The system of claim 29, further comprising a positional scanner for supporting the terahertz transmitter and terahertz receiver for scanning at least a portion of the surface of the structure.

32. The system of claim 29, wherein the terahertz receiver comprises a viewing portion that is configured for wearing on a human head and for providing an inspection operator the ability to immediately view the location of terahertz radiation absorbed by liquid remaining on the surface of the structure during an ongoing inspection operation.