Reference system for online vision inspection

1. A method for referencing a composite structure within a vision inspection system, the composite structure manufactured by an automated tool on a mold, the method comprising:

providing at least one reference target on a contour of a lay-up surface;

determining an absolute position of the at least one reference target in a mold reference system, the mold reference system setting out an absolute coordinate system for the mold;

acquiring an image of the at least one reference target;

determining a position of the at least one reference target from the image in an image reference system setting out a measuring coordinate system for pixels in the image;

correlating the mold reference system and the image reference system using the position of the at least one reference target in the mold reference system and the image reference system;

providing a measuring calibration target within a vision field of an image acquisition device, the measuring calibration target having known dimensions; and

acquiring an image of the measuring calibration target and using the known dimensions to determine a size of one pixel in the image, wherein the measuring calibration target has a plurality of thicknesses to represent a plurality of layers of the composite structure.

2. The method of claim 1 , wherein providing at least one reference target comprises providing at least one outer reference target on an outer contour of the mold.

3. The method of claim 2 , wherein the at least one outer reference target comprises a label having an optical machine-readable representation of identification data.

4. The method of claim 2 , wherein providing at least one outer reference target comprises providing the at least one reference target with a circular reflective zone.

5. The method of claim 1 , wherein providing at least one reference target comprises providing at least one inner reference target on a first layer of the composite structure to act as a reference for a second layer of the composite structure on top of the first layer.

6. The method of claim 5 , wherein providing at least one inner reference target comprises printing the at least one inner reference target on the first layer.

7. The method of claim 6 , wherein printing the at least one inner reference target comprises printing an ink marking on the first layer.

8. The method of claim 6 , wherein printing the at least one inner reference target comprises printing during a lamination of the first layer.

9. The method of claim 1 , wherein determining a position of the at least one reference target in the mold reference system comprises laser scanning the at least one reference target.

10. The method of claim 1 , wherein providing at least one reference target comprises providing at least one reference target per lay-up band of the composite structure.

11. The method of claim 1 , wherein acquiring an image of the at least one reference target comprises acquiring the image together with a feature to be inspected.

12. The method of claim 11 , further comprising determining a position of the feature to be inspected within the absolute coordinate system of the mold, through use of the image reference system.

13. A method for referencing a composite structure within a vision inspection system, the composite structure manufactured by an automated tool on a mold, the method comprising:

receiving a position of at least one reference target in a mold reference system, the mold reference system setting out an absolute coordinate system for the mold;

receiving an image of the at least one reference target;

determining a position of the at least one reference target from the image in an image reference system setting out a measuring coordinate system for pixels in the image;

correlating the mold reference system and the image reference system using the position of the at least one reference target in the mold reference system and the image reference system;

providing a measuring calibration target within a vision field of an image acquisition device, the measuring calibration target having known dimensions; and

acquiring an image of the measuring calibration target and using the known dimensions to determine a size of one pixel in the image, wherein the measuring calibration target has a plurality of thicknesses to represent a plurality of layers of the composite structure.

14. The method of claim 13 , wherein correlating the mold reference system and the image reference system comprises transferring the measuring coordinate system to the absolute coordinate system through angular projection on a theoretical Computer Aided Design (CAD) surface of the mold.

15. The method of claim 13 , wherein correlating the mold reference system and the image reference system comprises:

calculating tool positioning errors in a flat vision field;

applying a correction to measurements in the flat vision field; and

transferring corrected measurements into a 3D surface through angular projection.

16. The method of claim 13 , wherein correlating the mold reference system and the image reference system comprises:

calculating tool positioning errors in a flat vision field;

transferring uncorrected measurements to a 3D surface through angular projection;

determining absolute tool positioning errors; and

applying a correction to the measurements on the 3D surface using the absolute tool positioning errors.

17. The method of claim 13 , further comprising correcting a pixel value measurement in accordance with a variation in a vision distance and a vision angle.

18. The method of claim 13 , further comprising calibrating in real time a vision distance to a surface of the composite structure.

19. The method of claim 18 , wherein calibrating in real time comprises stereoscopically projecting a pair of calibration targets onto the composite structure and applying a corrective measure when an image formed by the projected calibration targets differs from a nominal image.

20. The method claim 13 , wherein receiving an image of the at least one reference target comprises receiving an image of the at least one reference target and a feature to be inspected.

21. The method of claim 20 , further comprising determining a position of the feature to be inspected within the absolute coordinate system of the mold, through use of the image reference system.

22. A system for referencing a composite structure within a vision inspection system, the composite structure manufactured by an automated tool on a mold, the system comprising:

a memory;

a processor coupled to the memory; and

an application stored in the memory and executable by the processor for:

receiving a position of at least one reference target in a mold reference system, the mold reference system setting out an absolute coordinate system for the mold;

receiving an image of the at least one reference target;

determining a position of the at least one reference target from the image in an image reference system setting out a measuring coordinate system for pixels in the image;

correlating the mold reference system and the image reference system using the position of the at least one reference target in the mold reference system and the image reference system;

providing a measuring calibration target within a vision field of an image acquisition device, the measuring calibration target having known dimensions; and

acquiring an image of the measuring calibration target and using the known dimensions to determine a size of one pixel in the image, wherein the measuring calibration target has a plurality of thicknesses to represent a plurality of layers of the composite structure.

23. The system of claim 22 , wherein correlating the mold reference system and the image reference system comprises transferring the measuring coordinate system to the absolute coordinate system through angular projection on a theoretical Computer Aided Design (CAD) surface of the mold.

24. The system of claim 22 , wherein correlating the mold reference system and the image reference system comprises:

calculating tool positioning errors in a flat vision field;

applying a correction to measurements in the flat vision field; and

transferring corrected measurements into a 3D surface through angular projection.

25. The system of claim 22 , wherein correlating the mold reference system and the image reference system comprises:

calculating tool positioning errors in a flat vision field;

transferring the tool positioning errors to a 3D surface;

transferring uncorrected measurements to the 3D surface through angular projection;

determining absolute tool positioning errors; and

applying a correction to the measurements on the 3D surface using the absolute tool positioning errors.

26. The system claim 22 , wherein the application is further configured for correcting a pixel value measurement in accordance with a variation in a vision distance and a vision angle.

27. The system of claim 22 , wherein the application is further configured for calibrating in real time a vision distance to a surface of the composite structure.

28. The system of claim 27 , wherein calibrating in real time comprises stereoscopically projecting a pair of calibration targets onto the composite structure and applying a corrective measure when an image formed by the projected calibration targets differs from a nominal image.

29. A method for referencing a composite structure within a vision inspection system, the composite structure manufactured by an automated tool on a mold, the method comprising:

providing at least one reference target on a contour of a lay-up surface;

determining an absolute position of the at least one reference target in a mold reference system, the mold reference system setting out an absolute coordinate system for the mold;

acquiring an image of the at least one reference target together with a feature under inspection;

determining a position of the at least one reference target from the image in an image reference system setting out a measuring coordinate system for pixels in the image;

correlating the mold reference system and the image reference system using the position of the at least one reference target in the mold reference system and the image reference system;

determining a position of the feature under inspection within the absolute coordinate system of the mold through use of the image reference system;

providing a measuring calibration target within a vision field of an image acquisition device, the measuring calibration target having known dimensions; and

acquiring an image of the measuring calibration target and using the known dimensions to determine a size of one pixel in the image, wherein the measuring calibration target has a plurality of thicknesses to represent a plurality of layers of the composite structure.

30. The method of claim 29 , wherein determining a position of the feature is performed while the automated tool is laying-up the composite structure.

31. A system for inspecting a feature of a composite structure manufactured by an automated fiber placement (AFP) tool, the AFP tool laying fiber tows on a mold in order to create multiple lay-up surfaces that form the composite structure, the system comprising:

a memory;

a processor coupled to the memory; and

an application stored in the memory and executable by the processor for:

receiving a position of at least one reference target in a mold reference system, the reference target being located on a contour of a lay-up surface, the mold reference system setting out an absolute coordinate system for the mold;

receiving an image of the at least one reference target together with the feature of the composite structure under inspection;

determining a position of the at least one reference target from the image in an image reference system setting out a measuring coordinate system for pixels in the image;

correlating the mold reference system and the image reference system using the position of the at least one reference target in the mold reference system and the image reference system; and

determining a position of the feature under inspection within the absolute coordinate system of the mold through use of the image reference system.