High-speed 3-D surface measurement surface inspection and reverse-CAD system

• US 5,175,601 A
• Filed: 10/15/1991
• Issued: 12/29/1992
• Est. Priority Date: 10/15/1991
• Status: Expired due to Term

• Current Assignee: Opton Co., Ltd.
• Original Assignee: Electro-Optical Information Systems
• Inventors: Fitts, John M.
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US07/775,432
• Time in Patent Office: 441 Days
• Field of Search: 356/376, 356/375, 250/237 G
• US Class Current: 356/604
• CPC Class Codes: G01B 11/2513 with several lines being projected in more than one direction, e.g. grids, patterns

Abstract

This invention relates to an apparatus and method for 3-D vision sensing or measurement to rapidly collect X-Y-Z surface data to support dimensional measurement, surface inspection and Reverse-CAD functions. The high-speed three-dimensional surface measurement system for use in determining the surface of an object from at least two electronic signals, has at least a first source for illuminating at least a surface area of the object with at least one fringe pattern. At least two cameras are provided for receiving reflected illumination from the surface area, each of the at least two cameras have a predetermined spacial orientation relative to the source for illuminating, a primary camera of the two cameras having a line-of-sight that forms a primary angle relative to a line-of-sight of the source for illuminating and a secondary camera of the two cameras having a line-of-sight that forms a secondary angle relative to the line-of-sight of the source for illuminating, the secondary angle being different than the primary angle. The primary camera provides a primary electronic signal representative of reflected illumination received thereby and the secondary camera providing a secondary electronic signal representative of reflected illumination received thereby.

Claims

1. A high-speed three-dimensional surface measurement system for use in determining the surface of an object from at least two electronic signals, comprising:

at least first means for illuminating at least a surface area of the object with at least one fringe pattern;

at least two means for receiving reflected illumination from said surface area, each of said at least two means for receiving reflected illumination having a predetermined spacial orientation relative to said means for illuminating, a primary means of said two means for receiving reflected illumination having a line-of-sight that forms a primary angle relative to a line-of-sight of said means for illuminating and a secondary means of said two means for receiving reflected illumination having a line-of-sight that forms a secondary angle relative to said line-of-sight of said means for illuminating, said secondary angle being different than said primary angle; and

said primary means providing a primary electronic signal representative of reflected illumination received thereby and said secondary means providing a secondary electronic signal representative of reflected illumination received thereby.

2. The system according to claim 1, wherein said first means for illuminating has a Ronchi grating through which illumination passes to produce said fringe pattern on said surface area of said object.

3. The system according to claim 1, wherein said first means for illuminating has a modified Ronchi grating through which illumination passes to produce said fringe pattern on said surface of said object, said modified Ronchi grating having alternating opaque and clear bands wherein said opaque bands are wider than said clear bands.

4. The system according to claim 3, wherein said opaque bands are approximately three time wider than said clear bands.

5. The system according to claim 1, wherein said first means for illumination has means for producing a variable fringe grating.

6. The system according to claim 5, wherein said means for producing a variable fringe grating is a liquid crystal display for forming patterns of illumination having transmissive and non-transmissive areas.

7. The system according to claim 1, wherein said primary means is a fine video camera such that said primary electronic signal contains at least information regarding a plurality X, Y, and Z points on said surface area and wherein said secondary means is a coarse video camera wherein said secondary electronic signal contains at least information for uniquely determining the position of the fringe pattern on the surface area when correlated with said information from said fine video camera.

8. The system according to claim 1, wherein said primary means is oriented approximately normal to said surface area and said primary angle is in the range of 19°

to 90°

, and wherein said secondary means is oriented such that line-of-sight of said secondary means forms a separation angle of at least 3°

with said line-of-sight of said primary means.

9. The system according to claim 1, wherein said system has a remotely located source of illumination connected to said means for illuminating via a fiber optic line.

10. The system according to claim 1, wherein said means for illuminating provides continuous illumination.

11. The system according to claim 1, wherein said means for illumination provides strobed illumination.

12. The system according to claim 1, wherein said means for illumination has a narrow spectral band visible laser and wherein each of said at least two means for receiving reflected illumination have narrow passband spectral filters.

13. The system according to claim 1, wherein said means for illumination has a strobe white light illuminator.

14. The system according to claim 1, wherein said system further comprises a second means for illuminating said surface area of said object with at least one fringe pattern;

said second means for illuminating having a line-of-sight oriented differently than said line-of-sight of said first means for illuminating;

said first means for illuminating projecting a vertical fringe pattern and said second means for illuminating projecting a horizontal fringe pattern, and wherein said vertical and horizontal fringe patterns are alternately projected onto said surface areas.

15. The system according to claim 14, wherein said system further comprises means for selecting said first means for illuminating responsive to part edges of said surface area oriented with approximately 45°

of a horizontal direction as indicated in a field of view of said at least two means for receiving reflected illumination and means for selecting said second means for illuminating response to part edge of said surface area oriented within 45°

of a vertical direction as indicated in a field of view of said at least two means for illumination.

16. The system according to claim 1, wherein said system further comprises a second means for illuminating said surface area of said object with at least one fringe pattern, said second means for illuminating having a line-of-sight oriented differently than said line-of-sight of said first means for illuminating, said first means for illuminating projecting simultaneously two vertical side-by-side fringe patterns and said second means for illuminating projecting simultaneously two horizontal side-by-side fringe patterns, wherein for each of said side-by-side fringe patterns one is a narrow field-of-view fringe pattern and the other is a wide field-of-view fringe pattern;

and wherein said system further comprises a third means for receiving reflected illumination;

said third means having a wide field-of-view for viewing the wide field-of-view fringe patterns and said primary and secondary means each having a narrow field-of-view for viewing said narrow field-of-view fringe patterns.

17. The system according to claim 1, wherein said at least first means for illuminating comprises a means for providing a beam of illumination, means for collimating the beam of illumination, means for providing a fringe grating through which the collimate beam of illumination passes, means for increasing the depth-of-field of said fringe patten on said surface area and means for focusing the fringe pattern on said surface area.

18. The system according to claim 17, wherein said means for collimating the beam of illumination is a condenser lens.

19. The system according to claim 17, wherein said means for increasing the depth-of-field is a pinhole aperture.

20. The system according to claim 17, wherein said means for collimating the beam of illumination is a cylindrical condenser lens and wherein said means for increasing the depth-of-field is a slit aperture oriented parallel to said means for providing a grating, said fringe grating being a plurality of alternating opaque and clear substantially straight line bands.

21. The system according to claim 17, wherein said means for providing a fringe pattern is a Ronchi grating.

22. The system according to claim 17, wherein said means for providing a fringe pattern is a modified Ronchi grating having alternating opaque and clear bands, and wherein said opaque bands are wider than said clear bands.

23. The system according to claim 22, wherein said opaque bands are approximately three times wider than said clear bands.

24. The system according to claim 17, wherein said at least one means for providing a fringe pattern is a liquid crystal display for forming different patterns of illumination having transmissive and non-transmissive areas.

26. The system according to claim 1, wherein said system further comprises means for moving said at least first means for illuminating and said at least two means for receiving reflected illumination relative to said object, said object being stationary.

27. The system according to claim 1, wherein said system further comprises means for moving said object relative to said at least first means for illuminating and said at least two means for receiving reflected illumination, and wherein said system further comprises means for moving said at least first means for illuminating and said at least two means for receiving reflected illumination.

25. The system according to claim wherein said system further comprises means for supporting in a stationary position said at least first means for illuminating and said two means for receiving reflected illumination relative to a position of said object, said object being moveable.

28. A high-speed three-dimensional surface measurement system for use in determining the surface of an object from at least two electronic signals, comprising:

first means for illuminating at least a surface area of the object with two vertical side-by-side fringe patterns;

second means for illuminating said surface area of said object with two horizontal side-by-side fringe patterns, for each of said side-by-side vertical and horizontal fringe patterns, one is a narrow field-of-view fringe pattern and the other is a wide field-of-view fringe pattern;

at least three means for receiving reflected illumination from said surface area, each of said at least three means for receiving reflected illumination having a predetermined spacial orientation relative to said first means for illuminating, a primary means of said three means for receiving reflected illumination having a line-of-sight that forms a primary angle relative to a line-of-sight of said first means for illuminating and a secondary means of said three means for receiving reflected illumination having a line-of-sight that forms a secondary angle relative to said line-of-sight of said first means for illuminating, said secondary angle being different than said primary angle, said second means for illuminating having a line-of-sight oriented differently than said line-of-sight of said first means for illuminating;

said third means having a wide field-of-view for viewing the wide field-of-view fringe patterns and said primary and secondary means each having a narrow field-of-view for viewing the respective narrow field-of-view fringe patterns;

said primary means providing a primary electronic signal representative of reflected illumination received thereby and said secondary means providing a secondary electronic signal representative of reflected illumination received thereby.

29. The system according to claim 28, wherein said primary means is a fine video camera such that said primary electronic signal contains at least information regarding a plurality X, Y, and Z points on said surface area and wherein said secondary means is a coarse video camera such that said secondary electronic signal contains at least information for uniquely determining the position of the fringe pattern on the surface area when correlated with said information from said fine video camera.

30. The system according to claim 28, wherein said primary means is oriented approximately normal to said surface area and said primary angle is in the range of 19°

to 90°

, and wherein said secondary means is oriented such that line-of sight of said secondary means forms a separation angle of at least 3°

with said line-of-sight of said primary means.

31. A high-speed three-dimensional surface measurement system for use in determining the surface of an object from at least two electronic signals, comprising:

first means for illuminating at least a surface area of the object with at least one first fringe pattern;

second means for illuminating said surface area of said object with at least one second fringe pattern;

at least two means for receiving reflected illumination from said surface area, each of said at least two means for receiving reflected illumination having a predetermined spacial orientation relative to said first and second means for illuminating, a primary means of said two means for receiving reflected illumination having a line-of-sight that forms a primary angle relative to a line-of-sight of said first means for illuminating and a secondary means of said two means for receiving reflected illumination having a line-of-sight that forms a secondary angle relative to said line-of-sight of said first means for illuminating, said secondary angle being different than said primary angle;

said second means for illuminating having a line-of-sight oriented differently than said line-of-sight of said first means for illuminating; and

said primary means providing a primary electronic signal representative of reflected illumination received thereby and said secondary means providing a secondary electronic signal representative of reflected illumination received thereby.

32. The system according to claim 31, wherein said first means for illuminating projects a vertical fringe pattern and said second means for illuminating projects a horizontal fringe pattern, and wherein said vertical and horizontal fringe patterns are alternately projected onto said surface area.

33. The system according to claim 31, wherein said system further comprises means for selecting said first means for illuminating responsive to part edges of said surface area oriented within approximately 45°

of a horizontal direction as indicated in a field-of-view of said at least two means for receiving reflected illumination and means for selecting said second means for illuminating response to part edge of said surface area oriented within approximately 45°

of a vertical direction as indicated in a field of view of said at least two means for illumination.

34. The system according to claim 31, wherein said primary means is a fine video camera such that said primary electronic signal contains at least information regarding a plurality X, Y, and Z points on said surface area and wherein said secondary means is a coarse video camera such that said secondary electronic signal contains at least information for uniquely determining the position of the fringe pattern on the surface area when correlated with said information from said fine video camera.

35. The system according to claim 31, wherein said primary means is oriented approximately normal to said surface area and said primary angle is in the range of 19°

to 90°

, and wherein said secondary means is oriented such that line-of-sight of said secondary means forms a separation angle of at least 3°

with said line-of-sight of said primary means.

37. The system according to claim 34, wherein said means for collimating the beam of illumination is a condenser lens.

38. The system according to claim 34, wherein said means for increasing the depth-of-field is a pinhole aperture.

39. The system according to claim 34, wherein said means for collimating the beam of illumination is a cylindrical condenser lens and wherein said means for increasing the depth-of-field is a slit operative oriented parallel to said means for providing a grating, said fringe grating being a plurality of alternating opaque and clear substantially straight line bands.

40. The system according to claim 34, wherein said means for providing a fringe pattern is a Ronchi grating.

41. The system according to claim 34, wherein said means for providing a fringe pattern is a modified Ronchi grating having alternating opaque and clear bands, and wherein said opaque bands are wider than said clear bands.

42. The system according to claim 39, wherein said opaque bands are approximately three times wider than said clear bands.

36. A high-speed three-dimensional surface measurement system for use in determining the surface of an object from at least two electronic signals, comprising:

at least first means for illuminating at least a surface area of the object with a fringe pattern, said at least first means for illuminating having a means for providing a beam of illumination, means for collimating the beam of illumination, means for providing a fringe grating through which the collimated beam of illumination passes, means for increasing the depth-of-field of said fringe pattern on said surface area and means for focusing the fringe pattern on said surface area;

at least two means for receiving reflected illumination from said surface area, each of said at least two means for receiving reflected illumination having a predetermined spacial orientation relative to said means for illuminating, a primary means of said two means for receiving reflected illumination having a line-of-sight that forms a primary angle relative to a line-of-sight of said means for illuminating and a secondary means of said two means for receiving reflected illumination having a line-of-sight that forms a secondary angle relative to said line-of-sight of said means for illuminating, said secondary angle being different than said primary angle; and

said primary means providing a primary electronic signal representative of reflected illumination received thereby and said secondary means providing a secondary electronic signal representative of reflected illumination received thereby.

43. A high-speed three-dimensional surface measurement system or use in determining the surface of an object from at least two electronic signals, comprising:

at least first means for illuminating at least a surface area of the object with at least one fringe pattern, said at least first means for illuminating having source means for providing light, cylindrical condenser lens arrangement that receives light from the source means and refocuses the light onto projector imaging optics, pattern means for generating a substantially parallel line fringe pattern located in close proximity to an output side of the cylindrical condenser lens arrangement, and slit aperture means located between the pattern means and the projector imaging of optics for providing a defocus along the length of each individual fringe of the fringe pattern without causing a defocus across the fringe pattern;

at least two means for receiving reflected illumination from said surface area, each of said at least two means for receiving reflected illumination having a predetermined spacial orientation relative to said means for illuminating, a primary means of said two means for receiving reflected illumination having a line-of-sight that forms a primary angle relative to a line-of-sight of said means for illuminating and a secondary means of said two means for receiving reflected illumination having a line-of-sight that forms a secondary angle relative to said line-of-sight of said means for illuminating, said secondary angle being different than said primary angle; and

said primary means providing a primary electronic signal representative of reflected illumination received thereby and said secondary means providing a secondary electronic signal representative of reflected illumination received thereby.

44. A method for determining the surface of an object in a high-speed three-dimensional surface measurement system, comprising the steps of:

illuminating with at least first means for illuminating at least a surface area of the object with at least one fringe pattern;

providing at least two cameras receiving reflected illumination from said surface area, each of said at least two cameras for receiving reflected illumination having a predetermined spacial orientation relative to said means for illuminating, a fine camera of said two cameras for receiving reflected illumination having a line-of-sight that forms a primary angle relative to a line-of-sight of said means for illuminating and a coarse camera of said two cameras for receiving reflected illumination having a line-of-sight that forms a secondary angle relative to said line-of-sight of said means for illuminating, said secondary angle being different than said primary angle;

providing three dimensional part coordinates indicative of the relation of the object to the fine and coarse cameras;

outputting a primary set of pixel coordinates and phase values from said fine camera;

outputting a secondary set of pixel coordinates and phase values from said coarse camera;

for each of the primary and secondary sets extracting primary and secondary raw unfolded phase values, respectively, from the pixel coordinates of the primary and secondary sets;

calculating first and second true integer values using the primary and secondary raw unfolded phase values and the pixel coordinates of the primary and secondary sets;

generating a phase map for the fine camera using the first and second true integer values; and

mapping the phase map onto a part map using the part coordinates to produce a final three dimensional coordinate set representative of the surface area of the object.

45. The method according to claim 44, wherein the method further comprises the step of performing a reverse - CAD operation by forming a representative surface description of the surface area of the object using the final three dimensional coordinate set.