Method and apparatus for absolute-coordinate three-dimensional surface imaging

• US 7,929,751 B2
• Filed: 11/09/2006
• Issued: 04/19/2011
• Est. Priority Date: 11/09/2005
• Status: Expired due to Fees

• Current Assignee: Hangzhou Conformal & Digital Technology Limited Corporation
• Original Assignee: GI, LLC
• Inventors: Zhang, Song, Royer, Dale, Wang, Yalin, Gu, Xianfeng, Yau, Shing-Tung
• Primary Examiner(s): PERUNGAVOOR, SATHYANARAYA V
• Application Number:
  US12/084,799
• Publication Number:
  US 20090238449A1
• Time in Patent Office: 1,622 Days
• Field of Search: 382/154
• US Class Current: 382/154
• CPC Class Codes: G01B 11/2536 using several gratings with variable grating pitch, projected on the object with the same angle of incidence
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light

Abstract

A method and associated apparatus for capturing an image of a 3D object (100) which encodes the surface geometry of at least a portion of the object, comprising: 1. projecting (304) a plurality of fringe patterns (312A, 314A) onto the object; 2. capturing (306) phase alterations in reflections of the fringe patterns (312B, 314B) from the object; 3. projecting a uniform image (310A) onto the object; 4. capturing a reflection of the uniform image (310B) from the object; and 5. combining (310) captured phase alterations and captured uniform image reflection on a pixel-by-pixel basis, thereby forming a holoimage representation of the object.

Claims

1. A method of determining absolute coordinates of a three-dimensional surface of an object, the method comprising:

projecting only two phase-shifted illumination patterns, wherein each of the illumination patterns encodes a marker, onto the surface of the object;

projecting a uniform illumination pattern onto the surface of the object;

capturing images of reflections of the illumination patterns from the surface of the object, including a black and white texture of the object surface;

combining the captured images as to generate a phase-wrapped image;

generating a relative unwrapped phase image by unwrapping the phase-wrapped image;

generating an absolute phase image from the relative unwrapped phase image; and

determining absolute coordinates of the surface of the object from the absolute phase image as well as surface texture of the object at said coordinates.

2. The method of claim 1, wherein capturing the images of the reflections of the illumination patterns comprises capturing said images in a black and white mode and in a color mode.

3. The method of claim 2, further including projecting a uniform illumination pattern, wherein a color texture of the surface of the object is captured simultaneously with determining the absolute coordinates of the surface of the object, using an image of a reflection from the surface of the object of the uniform illumination pattern captured in the color mode.

4. The method of claim 1, wherein capturing the black and white texture includes removing the encoded marker from the captured image of the uniform illumination pattern.

5. The method of claim 3, wherein capturing the color texture includes removing the encoded marker from the captured image of the uniform illumination pattern.

6. The method of claim 4, wherein the illumination patterns are color encoded.

7. The method of claim 5, wherein the illumination patterns are color encoded.

8. The method of claim 1, wherein phase unwrapping comprises:

generating a quality map;

dividing the quality map into multiple quality levels; and

applying a phase unwrapping algorithm to each of the levels separately, in order of decreasing quality.

9. The method of claim 8, wherein generating the quality map comprises generating a gradient map of the phase-wrapped image.

10. The method of claim 8, wherein generating the quality map comprises generating a variance map of the phase-wrapped image.

11. The method of claim 10, wherein the phase unwrapping algorithm is a fast scan-line phase unwrapping algorithm.

12. The method of claim 1, wherein the two phase-shifted illumination patterns are separated by approximately 90 degrees of phase shift.

13. The method according to claim 12, wherein generating the two phase-shifted illumination patterns comprises generating only two phase-shifted illumination patterns.

14. The method according to claim 1, wherein generating the two phase-shifted illumination patterns comprises generating only two phase-shifted illumination patterns.

15. The method of claim 1, wherein generating the absolute phase image from the relative unwrapped phase image includes detecting a phase of the encoded marker and adjusting the relative unwrapped phase image according to the detected phase of the encoded marker.

16. An apparatus for determining absolute coordinates of a three-dimensional surface of an object, the apparatus comprising:

at least one illumination pattern generator for generating only two phase-shifted and one uniform illumination patterns, wherein each of the illumination patterns encodes a phase marker;

at least one projection device for projecting the illumination patterns onto the surface of the object;

at least one imaging device for capturing images of reflections of the illumination patterns from the surface of the object; and

at least one image processor for processing the captured images to determine the surface texture of the object and the absolute coordinates of the surface of the object as a function of a decoded phase of the marker.

17. The apparatus of claim 16, wherein the at least one projection device is synchronized with the at least one imaging device.

18. The apparatus of claim 16, wherein the at least one illumination pattern generator and the at least one image processor are part of an integral unit.

19. The apparatus of claim 16, wherein the at least one image processor is adapted and configured, when processing the captured images, to:

combine the captured images as to generate a phase-wrapped image;

generate a relative unwrapped phase image by unwrapping the phase-wrapped image;

generate an absolute phase image from the relative unwrapped phase image; and

determine absolute coordinates of the surface of the object from the absolute phase image.

20. The apparatus of claim 19, wherein the at least one imaging device comprises at least one imaging device capturing images in a black and white mode and at least one imaging device capturing images in a color mode.

21. The apparatus of claim 20, wherein the at least one imaging device capturing images in the black and white mode and the at least one imaging device capturing images in the color mode operate independently and in synchronization.

22. The apparatus of claim 21, wherein the illumination patterns are color encoded patterns, and the images of the reflections of the patterns are captured in the black and white mode.

23. The apparatus of claim 20, wherein the illumination patterns are color encoded patterns, and the images of the reflections of the patterns are captured in the black and white mode and in the color mode.

24. The apparatus of claim 22, wherein a black and white texture of the surface of the object is captured simultaneously with determining the absolute coordinates of the surface of the object, using the image of the reflection of the uniform illumination pattern.

25. The apparatus of claim 23, wherein a color texture of the surface of the object is captured simultaneously with determining the absolute coordinates of the surface of the object, using the image of the reflection of the uniform illumination pattern, and wherein the image was captured in the color mode.

26. The apparatus of claim 24, wherein capturing the black and white texture includes removing the encoded marker from the image of the uniform illumination pattern.

27. The apparatus of claim 25, wherein capturing the color texture includes removing the encoded marker from the captured image of the uniform illumination pattern.

28. The apparatus of claim 19, wherein the at least one image processor, is configured and arranged, when phase unwrapping, to:

generate a quality map;

divide the quality map into multiple quality levels; and

apply a phase unwrapping algorithm to each of the levels separately, in order of decreasing quality of data points in the levels.

29. The apparatus of claim 28, wherein the at least one image processor when generating the quality map comprises generating a gradient map of the phase-wrapped image.

30. The apparatus of claim 28, wherein the at least one image processor when generating the quality map comprises generating a variance map of the phase-wrapped image.

31. The apparatus of claim 28, wherein the phase unwrapping algorithm is a fast scan-line phase unwrapping algorithm.

32. The apparatus of claim 16, wherein the two phase-shifted illumination patterns are separated by approximately 90 degrees of phase shift.

33. The apparatus of claim 18, wherein generating the absolute phase image from the relative unwrapped phase image includes detecting a phase of the encoded marker and adjusting the relative unwrapped phase image according to the detected phase of the encoded marker.

34. The apparatus of claim 16, wherein generating the two phase-shifted illumination patterns comprises generating only two phase-shifted illumination patterns.

35. The apparatus of claim 19, wherein determining the absolute coordinates of the surface of the object from the absolute phase image is performed by a graphics processing unit.