SYSTEM AND METHOD FOR 3D MEASUREMENT AND SURFACE RECONSTRUCTION

• US 20090102840A1
• Filed: 11/12/2008
• Published: 04/23/2009
• Est. Priority Date: 07/15/2004
• Status: Active Grant

• Current Assignee: City University of Hong Kong
• Original Assignee: City University of Hong Kong
• Inventors: Li, You Fu
• Granted Patent: US 8,213,707 B2
• Time in Patent Office: Days
• US Class Current: 345/419
• CPC Class Codes: G01B 11/2504 Calibration devices
• CPC Class Codes: G01B 11/2509 Color coding
• CPC Class Codes: G06T 17/10 Constructive solid geometry [CSG] using solid primitives, e.g. cylinders, cubes
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration

Abstract

A system and method for measuring and surface reconstruction of a 3D image of an object comprises a projector arranged to project a pattern onto a surface of an object to be imaged; and a processor stage arranged to examine distortion or distortions produced in the pattern by the surface. The processor stage is arranged to convert by, for example, a triangulation process the distortion or distortions produced in the pattern by the surface to a distance representation representative of the shape of the surface. The processor stage is also arranged to reconstruct electronically the surface shape of the object.

Claims

1. A method for measuring and surface reconstruction of a 3D image of an object comprising:

projecting a pattern onto a surface of an object to be imaged;

examining in a processor stage distortion or distortions produced in said pattern by said surface;

converting in said processor stage said distortion or distortions produced in said pattern by said surface to a distance representation representative of the shape of the surface; and

reconstructing electronically said surface shape of said object.

2. A method according to claim 1, wherein the step of projecting a pattern comprises projecting a pattern of rectangles onto a surface of an object to be imaged.

3. A method according to claim 1, wherein the step of projecting a pattern comprises projecting a striped pattern onto a surface of an object to be imaged.

4. A method according to claim 1, wherein the step of projecting a pattern comprises projecting a pattern of squares onto a surface of an object to be imaged.

5. A method according to claim 1, wherein the step of projecting a pattern comprises projecting a pattern using an LCD projector.

6. A method according to claim 1, wherein the step of projecting a pattern comprises projecting a colour-coded array pattern onto a surface of an object to be imaged.

7. A method according to claim 1, further comprising viewing using a camera said pattern projected onto said surface and passing one or more signals from said camera representative of said pattern to said processing stage.

8. A method according to claim 7, wherein the step of viewing using a camera comprises viewing using a CCD camera.

9. A method according to claim 7, wherein said step of projecting comprises projecting using a projector, said method further comprising arranging said camera and said projector to have 6 degrees of freedom relative to each other.

10. A method according to claim 9, wherein said step of arranging comprises arranging said camera and said projector to have 3 linear degrees of freedom and 3 rotational degrees of freedom relative to each other.

11. A method according to claim 1, wherein said step of projecting comprises projecting using a projector, the method further comprising calibrating said projector prior to projecting said pattern.

12. A method according to claim 9, further comprising automatically reconfiguring one or more settings of said degrees of freedom if said one or more settings are varied during operation.

13. A method according to claim 12, wherein said step of reconfiguring comprises taking a single image of said surface for reconfiguring one or more external parameters of said camera and/or said projector.

14. A method according to claim 13, wherein said step of reconfiguring comprises taking a further image of said surface for reconfiguring one or more internal parameters of said camera and/or said projector.

15. A method according to claim 1, further comprising viewing said surface obliquely to monitor distortion or distortions in said pattern.

16. A method according to claim 1, wherein said step of reconstructing comprises reconstructing said surface from a single image.

17. A method according to claim 1, wherein said step of reconstructing comprises reconstructing said surface from two or more images taken from different positions if one or more portions of said image are obscured in a first image taken.

18. A method according to claim 1, wherein said step of examining comprises:

slicing in said processor stage said pattern as distorted by said surface into a number of cross section curves;

reconstructing one or more of said cross-section curves by a closed B-spline curve technique;

selecting a control point number of B-spline models from said one or more curves;

determining using entropy techniques representation of uncertainty in said selected B-spline models to predict the information gain for each cross section curve;

mapping said information gain of said B-spline models into a view space; and

selecting as the Next Best View a view point in said view space containing maximum information gain for said object.

19. A method according to claim 18, wherein a Bayesian information criterion (BIC) is applied for selecting the control point number of B-spline models from said one or more curves.

20. A method according to claim 18, further comprising terminating said method when said entire surface of said object has been examined and it has been determined that there is no further information to be gained from said surface.

21. A method according to claim 1, further comprising taking metric readings from said reconstructed surface shape.

22. A method according to claim 1, wherein said step of converting said distortion or distortions comprises converting using a triangulation process.

23. A system for measuring and surface reconstruction of a 3D image of an object comprising:

a projector arranged to project a pattern onto a surface of an object to be imaged;

a processor stage arranged to examine distortion or distortions produced in said pattern by said surface;

said processor stage further being arranged to convert said distortion or distortions produced in said pattern by said surface to a distance representation representative of the shape of the surface; and

said processor stage being arranged to reconstruct electronically said surface shape of said object.

24. A system according to claim 23, wherein said pattern comprises an array of rectangles.

25. A system according to claim 23, wherein said pattern comprises an array of stripes.

26. A system according to claim 23, wherein said pattern comprises an array of squares.

27. A system according to claim 23, wherein said projector comprises an LCD projector.

28. A system according to claim 23, wherein said pattern comprises a colour-coded array pattern.

29. A system according to claim 23, further comprising a camera arranged to view said pattern projected onto said surface;

said camera being arranged to pass one or more signals representative of said pattern to said processor.

30. A system according to claim 29, wherein said camera comprises a CCD camera.

31. A system according to claim 29, wherein said projector and said camera are arranged to have 6 degrees of freedom relative to each other.

32. A system according to claim 31, wherein said projector and said camera are arranged to have 3 linear degrees of freedom and 3 rotational degrees of freedom relative to each other.

33. A system according to claim 23, wherein said projector is calibrated prior to projecting said pattern.

34. A system according to claim 29, wherein said processor is arranged to automatically reconfigure one or more settings of said degrees of freedom if said one or more settings are varied during operation.

35. A system according to claim 34, wherein processor is arranged to reconfigure said one or more settings by taking a single image of said surface for reconfiguring one or more external parameters of said camera and/or said projector.

36. A system according to claim 35, wherein processor is arranged to reconfigure said one or more settings by taking a further image of said surface for reconfiguring one or more internal parameters of said camera and/or said projector.

37. A system according to claim 29, wherein said camera is arranged to view said surface obliquely to monitor distortion or distortions in said pattern.

38. A system according to claim 23, wherein said processor is arranged to reconstruct said surface from a single image.

39. A system according to claim 23, wherein said processor is arranged to reconstruct said surface from two or more images taken from different positions if one or more portions of said image are obscured in a first image taken.

40. A system according to claim 23, wherein said processor is arranged to:

slice said processor stage said pattern as distorted by said surface into a number of cross section curves;

reconstruct one or more of said cross-section curves by a closed B-spline curve technique;

select a control point number of B-spline models from said one or more curves;

determine using entropy techniques representation of uncertainty in said selected B-spline models to predict the information gain for each cross section curve;

map said information gain of said B-spline models into a view space; and

select as the Next Best View a view point in said view space containing maximum information gain for said object.

41. A system according to claim 40, wherein said processor is arranged to apply a Bayesian information criterion (BIC) for selecting the control point number of B-spline models from said one or more curves.

42. A system according to claim 40, wherein said processor is arranged to terminate one or more processing steps when said entire surface of said object has been examined and it has been determined that there is no further information to be gained from said surface.

43. A system according to claim 23, wherein said processor is arranged to convert said distortion or distortions using a triangulation process.

44. An active vision system comprising the system according to claim 23.