METHODS AND APPARATUS FOR MEASURING 3D DIMENSIONS ON 2D IMAGES

• US 20100124369A1
• Filed: 11/20/2008
• Published: 05/20/2010
• Est. Priority Date: 11/20/2008
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Foster, Eric Scott, Wu, Yanyan, Kaucic, Robert August, Tao, Xiaodong, Howard, Donald Robert, Sun, Zhaohui, Ringermacher, Harry Israel, Howard, Patrick Joseph, Little, Francis Howard, Dragovich, Matthew Edward
• Granted Patent: US 8,238,642 B2
• Time in Patent Office: Days
• US Class Current: 382/141
• CPC Class Codes: G01B 11/02 for measuring length, width or thickness G01B11/08 takes precedence
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G06T 2207/10048 Infrared image
• CPC Class Codes: G06T 2207/30164 Workpiece; Machine component
• CPC Class Codes: G06T 7/001 using an image reference approach
• CPC Class Codes: G06T 7/337 involving reference images or patches

Abstract

A method for determining 3D distances on a 2D pixelized image of a part or object includes acquiring a real 2D pixelized image of the object, creating a simulated image of the object using the 3D CAD model and the 2D pixelized image, determining a specified cost function comparing the simulated image with the real 2D pixilated image and repositioning the simulated image in accordance with iterated adjustments of a relative position between the CAD model and the XID pixilated image to change the simulated image until the specified cost function is below a specified value. Then, the workstation is used to generate a 3D distance scale matrix using the repositioned simulated image, and to measure and display distances between selected pixels on a surface of the real image using 2D distances on the 2D pixelized image of the object and the 3D distance scale matrix.

Claims

1. A method for determining 3D distances on a 2D pixelized image of a part or object using a camera, a 3D CAD model of the object, and a workstation that includes a display, said method comprising:

acquiring a real 2D pixelized image of the object, using the camera;

operating the workstation to create a simulated image of the object using the 3D CAD model and the 2D pixelized image;

use the workstation to determine a specified cost function comparing the simulated image with the real 2D pixilated image;

repositioning the simulated image in accordance with interated adjustments of a relative position between the CAD model and the 2D pixilated image to change the simulated image until the specified cost function is below a specified value;

once below the specified value, using the workstation to generate a 3D distance scale matrix using the repositioned simulated image; and

using the workstation to measure and display distances between selected pixels on a surface of the real image using 2D distances on the 2D pixelized image of the object and the 3D distance scale matrix.

2. A method in accordance with claim 1 wherein acquiring the real 2D pixelized image comprises acquiring a real IR (thermal) image.

3. A method in accordance with claim 2 used for nondestructive inspection of CMC parts.

4. A method in accordance with claim 2 used for nondestructive inspection of CMC aircraft parts.

5. A method in accordance with claim 1 wherein said iterative adjustments use a statistic that depends upon a difference of grayscale values of corresponding pixels in the real image and the simulated image.

6. A method in accordance with claim 1 wherein performing said iterative adjustments comprises using an LM optimization method.

7. A method in accordance with claim 1 wherein performing said iterative adjustments comprises using a Newton algorithm.

8. A method in accordance with claim 1 wherein once below the specified value, generating a 3D distance scale matrix using the repositioned simulated image further comprises determining distances of the simulated image from a focal plane.

9. A method in accordance with claim 8 wherein said measuring and displaying distances between selected pixels on a surface of the real image using 2D distances on the pixelized image of the object comprises using geodesic distances treated as x-y coordinates and thickness data treated as z-axis distances in the 3D distance scale matrix corresponding to selected x-y coordinates to determine said distances between selected pixels on the surface of the real image.

10. An apparatus for determining 3D distances on a 2D pixelized image of a part or object, said apparatus comprising:

a camera;

a computer workstation configured to receive images from said camera and having a 3D CAD model of the object; and

a display;

said apparatus configured to;

acquire a real 2D pixelized image of the object;

create a simulated image of the object using the 3D CAD model;

determine a specified cost function comparing the simulated image with the real 2D pixilated image;

reposition the simulated image in accordance with interated adjustments of a relative position between the CAD model and the 2D pixilated image to change the simulated image until the specified cost function is below a specified value;

generate a 3D distance scale matrix using the repositioned simulated image; and

measure and display distances between selected pixels on a surface of the real image using 2D distances on the pixelized image of the object and the 3D distance scale matrix.

11. An apparatus in accordance with claim 10 wherein the camera is an IR camera and to acquire the real 2D pixelized image, said apparatus configured to acquire a real IR (thermal) image.

12. An apparatus in accordance with claim 10 wherein said iterative adjustments use a statistic that depends upon a difference of grayscale values of corresponding pixels in the real image and the simulated image.

13. An apparatus in accordance with claim 10 wherein to perform said iterative adjustments, said apparatus configured to use an LM optimization method.

14. An apparatus in accordance with claim 10 wherein to generate a 3D distance scale matrix using the repositioned simulated image, said apparatus configured to determine distances of the simulated image from a focal plane.

15. An apparatus in accordance with claim 14 wherein to measure and display distances between selected pixels on a surface of the real image using 2D distances on the pixelized image of the object and the 3D distance scale, said apparatus configured to use geodesic distances treated as x-y coordinates and thickness data treated as z-axis distances in the 3D distance scale matrix corresponding to selected x-y coordinates to determine said distances between selected pixels on the surface of the real image.

16. A machine-readable medium or media having recorded thereon instructions configured to instruct a computer workstation in an apparatus comprising a camera, a computer workstation configured to receive images from said camera and having a 3D CAD model of an object, and a display, to:

acquire a real 2D pixelized image of the object using the camera;

create a simulated image of the object using the 3D CAD model;

determine a specified cost function comparing the simulated image with the real 2D pixilated image;

reposition the simulated image in accordance with interated adjustments of a relative position between the CAD model and the 2D pixilated image to change the simulated image until the specified cost function is below a specified value;

generate a 3D distance scale matrix using the repositioned simulated image; and

measure and display distances between selected pixels on a surface of the real image using 2D distances on the pixelized image of the object and the 3D distance scale matrix.

17. A machine-readable media or medium in accordance with claim 16 wherein the camera is an IR camera and said media or medium further have recorded instructions configured to instruct the workstation to acquire a real IR (thermal) image.

18. A machine-readable media or medium in accordance with claim 16 wherein to iteratively change the alignment of the simulated image with the real image until a specified cost function is below a specified value, said recorded instructions further configured to instruct the workstation to use a statistic that depends upon a difference of grayscale values of, or thickness information associated with corresponding pixels in the real image and the simulated image.

19. A machine-readable media or medium in accordance with claim 16 wherein to perform said iterative adjustments, said recorded instructions further configured to instruct the workstation to use an LM optimization method.

20. A machine-readable media or medium in accordance with claim 19 wherein to generate a 3D distance scale matrix using the repositioned simulated image, said recorded instructions further configured to determine distances of the repositioned simulated image from a focal plane, and wherein to measure and display distances between selected pixels on a surface of the real image using 2D distances on the pixelized image of the object and the 3D distance scale, said recorded instructions further configured to use geodesic distance treated as x-y coordinates and thickness data treated as z-axis distances in the 3D distance scale matrix corresponding to selected x-y coordinates to determine said distances between selected pixels on the surface of the real image.