Rapid automated infrared thermography for inspecting large composite structures

Patent metadata

Field	Value
Publication number	US-9645012-B2
Application number	US-201514827788-A
Country	US
Kind code	B2
Filing date	Aug 17, 2015
Priority date	Aug 17, 2015
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

Systems and methods for infrared thermographic inspection of large-scale composite structures such as sections of an aircraft fuselage. Optical metrology is used to precisely locate the infrared images relative to a three-dimensional coordinate system of the composite structure. The optical metrology may comprise laser tracking or photogrammetry or both. In some embodiments, the optical metrology comprises laser tracking merged with photogrammetry. Once the infrared images have been precisely located relative to the coordinate system of the composite structure, structural data about the composite structure (e.g., thickness data) can be retrieved from a database containing a three-dimensional model of the composite structure. In the case of thermographic porosity measurements, the infrared imaging data can be correlated with thickness data to determine the porosity of the composite structure in the inspection area.

First claim

The invention claimed is:

1. A method for infrared thermographic inspection of a composite structure comprising:
(a) moving an infrared camera to a first location whereat a field of view of the infrared camera encompasses a first inspection area of a surface of the composite structure;
(b) determining a first coordinate location of the field of view of the infrared camera in a coordinate system of the composite structure using optical metrology while the infrared camera is at the first location;
(c) activating at least one flash lamp to output light that illuminates at least portions of the first inspection area;
(d) activating the infrared camera to acquire first infrared imaging data while the field of view of the infrared camera encompasses at least the first inspection area;
(e) moving the infrared camera to a second location whereat the field of view of the infrared camera encompasses a second inspection area of the surface of the composite structure;
(f) determining a second coordinate location of the field of view of the infrared camera in the coordinate system of the composite structure using optical metrology while the infrared camera is at the second location;
(g) activating at least one flash lamp to output light that illuminates at least portions of the second inspection area;
(h) activating the infrared camera to acquire second infrared imaging data while the field of view of the infrared camera encompasses at least the second inspection area; and
(i) stitching the first and second infrared imaging data together based on at least the first and second coordinate locations of the field of view of the infrared camera in the coordinate system of the composite structure.

2. The method as recited in claim 1 , wherein said optical metrology comprises laser tracking.

3. The method as recited in claim 2 , wherein steps (b) and (f) collectively comprise:
placing optical targets on the composite structure;
directing respective pulses of light from a laser tracker toward the optical targets on the composite structure;
processing light returned from the optical targets on the composite structure to the laser tracker to determine first location data representing a coordinate location of the composite structure in a coordinate system of the laser tracker;
placing optical targets on a robot base that supports a robotic arm which supports the infrared camera;
directing respective pulses of light from the laser tracker toward the optical targets on the robot base;
processing light returned from the optical targets on the robot base to the laser tracker to determine second location data representing a coordinate location of the robot base in the coordinate system of the laser tracker;
encoding movements of the robotic arm; and
computing the first and second coordinate locations of the field of view of the infrared camera in the coordinate system of the composite structure based on at least the first and second location data and encoded movements of the robotic arm.

4. The method as recited in claim 2 , wherein steps (b) and (f) collectively comprise:
placing optical targets on the composite structure;
directing respective pulses of light from one or more laser trackers toward the optical targets on the composite structure;
processing light returned from the optical targets on the composite structure to determine first location data representing a coordinate location of the composite structure in a coordinate system of the one or more laser trackers;
attaching respective sets of optical targets to first, second and third bars;
placing the first, second and third bars adjacent the composite structure in respective locations so that the first and second bars are separated by the first inspection area, and the second and third bars are separated by the second inspection area;
directing respective pulses of light from the one or more laser trackers toward the optical targets on the first and second bars during activations of the infrared camera in step (d);
directing respective pulses of light from the one or more laser trackers toward the optical targets on the second and third bars during activations of the infrared camera in step (h);
processing light returned from the optical targets on the first, second and third bars to determine second location data representing respective coordinate locations of the first, second and third bars in the coordinate system of the one or more laser trackers; and
computing the first and second coordinate locations of the field of view of the infrared camera in the coordinate system of the composite structure based on at least the first and second location data and the first and second infrared imaging data.

5. The method as recited in claim 4 , wherein computing the first and second coordinate locations of the field of view of the infrared camera in the coordinate system of the composite structure comprises identifying portions of the first infrared imaging data which correspond to light returned from the optical targets on the first and second bars.

6. The method as recited in claim 1 , wherein said optical metrology comprises photogrammetry.

7. A method for infrared thermographic inspection comprising:
(a) attaching a pair of photogrammetry cameras to an infrared camera to form a camera assembly;
(b) moving the camera assembly to a first location whereat respective fields of view of the photogrammetry cameras encompass a first inspection area of a surface of the composite structure;
(c) determining a first coordinate location of a field of view of the photogrammetry cameras in a coordinate system of the composite structure using optical metrology while the camera assembly is at the first location;
(d) activating at least one flash lamp to output light that illuminates at least portions of the first inspection area;
(e) activating the infrared camera to acquire first infrared imaging data while the field of view of the infrared camera encompasses at least the first inspection area;
(f) activating a projector to project a pattern of light onto the first inspection area while the camera assembly is at the first location;
(g) activating the photogrammetry cameras to acquire first photogrammetry data while the field of view of the photogrammetry cameras encompasses at least a portion of the projected pattern of light on the first inspection area;
(h) moving the camera assembly to a second location whereat the field of view of the photogrammetry cameras encompasses a second inspection area of the surface of the composite structure;
(i) determining a second coordinate location of the field of view of the photogrammetry cameras in the coordinate system of the composite structure using optical metrology while the camera assembly is at the second location;
(j) activating at least one flash lamp to output light that illuminates at least portions of the second inspection area;
(j) activating the infrared camera to acquire second infrared imaging data while the field of view of the infrared camera encompasses at least the second inspection area;
(k) activating a projector to project a pattern of light onto the second inspection area while the camera assembly is at the second location;
(l) activating the photogrammetry cameras to acquire second photogrammetry data while the field of view of the photogrammetry cameras encompasses at least a portion of the projected pattern of light on the second inspection area;
(m) stitching the first and second photogrammetry data together based on at least the first and second coordinate locations of the field of view of the photogrammetry cameras in the coordinate system of the composite structure;
(n) correlating the first and second infrared imaging data to the first and second

Assignees

• Boeing Co

Inventors

• Marsh Bobby J
• Georgeson Gary E
• Thompson Jeffrey R

Classifications

• G01J2005/0077

  Imaging · CPC title

• G01N25/72

  Investigating presence of flaws · CPC title

• H04N23/56

  provided with illuminating means · CPC title

• H04N23/90

  Arrangement of cameras or camera modules, e.g. multiple cameras in TV studios or sports stadiums · CPC title

• G01S17/66

  Tracking systems using electromagnetic waves other than radio waves · CPC title