System for detecting structural defects and features utilizing blackbody self-illumination

• US 7,164,146 B2
• Filed: 10/22/2004
• Issued: 01/16/2007
• Est. Priority Date: 10/22/2004
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Chu, Steven, DiMarzio, Donald, Weir, John Douglas, Silberstein, Robert P.
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US10/971,217
• Publication Number:
  US 20060086912A1
• Time in Patent Office: 816 Days
• Field of Search: 250/559.4, 250/559.27, 250/559.45, 356/239.1, 356/239.2
• US Class Current: 250/559.4
• CPC Class Codes: G01J 2005/0077 Imaging
• CPC Class Codes: G01N 2021/8472 Investigation of composite materials
• CPC Class Codes: G01N 21/3563 for analysing solids; Preparation of samples therefor
• CPC Class Codes: G01N 21/8422 Investigating thin films, e.g. matrix isolation method
• CPC Class Codes: G01N 21/88 Investigating the presence of flaws or contamination
• CPC Class Codes: G01N 25/72 Investigating presence of flaws

Abstract

A system is disclosed which utilizes the substantially steady-state temperature of a coated object, in conjunction with an optical detection system, to selectively view defects and features of the object below the coating without the necessity of transient heating or IR illumination and reflectance imaging. The optical detector, such as an IR camera, may be tailored for the wavelengths at which the coating material is substantially transparent, thereby maximizing the viewing clarity of the defects and features under the coating, and distinguishing them from any spurious features on the top surface of the coating. The present system enables the inspection of small or large areas in real time, without requiring complex image acquisition, storage and image processing equipment and software.

Claims

1. A method of inspecting a coated object, the method comprising:

maintaining substantially steady state blackbody radiation from the object; and

detecting structural features of the object under the coating based on the blackbody radiation.

2. The method of claim 1, wherein the object is held at room temperature to maintain the substantially steady state blackbody radiation.

3. The method of claim 2, wherein the room temperature is from about 32 to about 80°

F.

4. The method of claim 1, wherein the object is held at an elevated temperature to maintain the substantially steady state blackbody radiation.

5. The method of claim 4, wherein the elevated temperature is less than about 120°

F.

6. The method of claim 4, wherein the elevated temperature is from about 80 to about 110°

F.

7. The method of claim 4, wherein the elevated temperature is maintained by exposing the object to sunlight.

8. The method of claim 4, wherein the elevated temperature is maintained by heating the object with a heat gun, a heat lamp and/or a thermal blanket.

9. The method of claim 1, wherein the structural features of the object are detected using an infrared camera.

10. The method of claim 9, wherein the infrared camera detects mid-infrared radiation having wavelengths between about 3 and about 5 microns.

11. The method of claim 9, wherein the infrared camera detects near-infrared radiation having wavelengths between about 0.7 and about 3 microns.

12. The method of claim 9, wherein the infrared camera detects far-infrared radiation having wavelengths between about 3 and about 12 microns.

13. The method of claim 1, wherein the structural features of the object are detected using an imaging device which detects radiation having at least one wavelength at which the coating is substantially transparent.

14. The method of claim 1, wherein the structural features of the object are detected using a movable camera.

15. The method of claim 14, wherein the movable camera is a hand-held camera.

16. The method of claim 14, wherein the movable camera is mounted at a single location during the detection, and includes a pan feature and/or a tilt feature.

17. The method of claim 1, wherein the structural features of the object are detected using a camera and a filter located in an optical path between the object and the camera.

18. The method of claim 17, wherein the filter removes a portion of the blackbody radiation having wavelengths at which the coating is non-transparent.

19. The method of claim 1, wherein the structural features of the object are detected using a camera and a polarizer located in an optical path between the object and the camera.

20. The method of claim 1, wherein the structural features comprise defects.

21. The method of claim 1, wherein the defects are on a surface of the object under the coating.

22. The method of claim 21, wherein the surface defects comprise corrosion, cracks, pits and/or gouges.

23. The method of claim 20, wherein the defects are under a surface of the object.

24. The method of claim 23, wherein the defects comprise corrosion, cracks and/or voids.

25. The method of claim 1, wherein the structural features comprise surface features on a surface of the object under the coating.

26. The method of claim 25, wherein the surface features comprise indicia.

27. The method of claim 26, wherein the indicia comprises alphanumeric symbols, marks or codes.

28. The method of claim 1, wherein the structural features comprise features under a surface of the object.

29. The method of claim 28, wherein the features comprise composite reinforcements and/or composite matrix materials.

30. The method of claim 1, wherein the object comprises an aircraft component.

31. The method of claim 1, wherein the coating comprises paint, a composite matrix material, primer, top coat and/or intermediate coatings.

32. The method of claim 1, further comprising displaying an image of the object including the detected structural features.

33. The method of claim 1, further comprising storing an image of the object including the detected structural features.

34. The method of claim 1, further comprising transmitting an image of the object including the detected structural features.

35. The method of claim 34, wherein the image is transmitted over the internet.

36. The method of claim 1, further comprising comparing an image of the object including the detected structural features with a reference image.

37. The method of claim 35, wherein the reference image is generated from another object similar to the coated object that is substantially free of defects.

38. A system for inspecting a coated object comprising:

means for maintaining substantially steady state blackbody radiation from the object; and

means for detecting structural features of the object under the coating based on the blackbody radiation.

39. A system for inspecting a coated object comprising a camera structured and arranged to detect structural features of the object under the coating based on substantially steady state blackbody radiation generated from the object.