HIGH SPEED, HIGH RESOLUTION, THREE DIMENSIONAL SOLAR CELL INSPECTION SYSTEM

• US 20110069154A1
• Filed: 09/21/2010
• Published: 03/24/2011
• Est. Priority Date: 09/22/2009
• Status: Active Grant

• Current Assignee: CyberOptics Corporation (Nordson Corporation)
• Original Assignee: CyberOptics Corporation (Nordson Corporation)
• Inventors: Case, Steven K., Skunes, Timothy A., Haugen, Paul R., Haugan, Carl E., Caruso, Beverly
• Granted Patent: US 8,388,204 B2
• Time in Patent Office: Days
• US Class Current: 348/46
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G01N 21/956 Inspecting patterns on the surface of objects contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: H04N 13/243 using three or more 2D image sensors
• CPC Class Codes: H04N 2013/0081 Depth or disparity estimation from stereoscopic image signals
• CPC Class Codes: H04N 7/188 Capturing isolated or intermittent images triggered by the occurrence of a predetermined event, e.g. an object reaching a predetermined position signal generation from motion picture films H04N5/253

Abstract

An optical inspection system and method are provided. A workpiece transport moves a workpiece in a nonstop manner. An illuminator includes a light pipe and is configured to provide a first and second strobed illumination field types. First and second arrays of cameras are arranged to provide stereoscopic imaging of the workpiece. The first array of cameras is configured to generate a first plurality of images of the workpiece with the first illumination field and a second plurality of images of the feature with the second illumination field. The second array of cameras is configured to generate a third plurality of images of the workpiece with the first illumination field and a fourth plurality of images of the feature with the second illumination field. A processing device stores at least some of the first, second, third, and fourth pluralities of images and provides the images to an other device.

Claims

1. An optical inspection system comprising:

a workpiece transport configured to transport the workpiece in a nonstop manner; and

an illuminator configured to provide a first strobed illumination field type and a second strobed illumination field type, the illuminator including a light pipe having a first end proximate the workpiece, and a second end opposite the first end and spaced from the first end, the light pipe also having at least one reflective sidewall, and wherein the first end has an exit aperture and the second end has at least one second end aperture to provide a view of the workpiece therethrough;

a first array of cameras configured to digitally image the workpiece, wherein the first array of cameras is configured to generate a first plurality of images of the workpiece with the first illumination field and a second plurality of images of the workpiece with the second illumination field;

a second array of cameras configured to digitally image the workpiece, wherein the second array of cameras is configured to generate a third plurality of images of the workpiece with the first illumination field and a fourth plurality of images of the workpiece with the second illumination field;

wherein the first and second arrays of cameras are configured to provide stereoscopic imaging of the workpiece; and

a processing device operably coupled to the illuminator and the first and second arrays of cameras, the processing device being configured to provide at least some of the first, second, third, and fourth pluralities of images to an other device.

2. The optical inspection system of claim 1, wherein the first array of cameras includes non-telecentric optics and wherein the cameras of the first array of cameras are aligned with one another along an axis perpendicular to a direction of workpiece motion and wherein the cameras of the first array of cameras have fields of view that overlap one another.

3. The optical inspection system of claim 1, wherein the first array of cameras includes non-telecentric optics and wherein the cameras of the second array of cameras are aligned with one another along an axis perpendicular to the direction of workpiece motion, but spaced from the first plurality of cameras in a direction of the workpiece motion.

4. The optical inspection system of claim 1, wherein:

the first array of cameras has telecentric optics, and wherein the cameras of the first array of cameras are aligned with one another along an axis perpendicular to a direction of workpiece motion, and have fields of view that do not overlap with one another; and

further comprising a third array of cameras having telecentric optics, and wherein the cameras of the third array of cameras are aligned with one another along an axis perpendicular to a direction of workpiece motion, and have fields of view that do not overlap with one another, wherein the first and third arrays of cameras have fields of view that are staggered;

wherein the second array of cameras has telecentric optics, and wherein the cameras of the second array of cameras are aligned with one another along an axis perpendicular to a direction of workpiece motion, and have fields of view that do not overlap with one another; and

further comprising a fourth array of cameras having telecentric optics, and wherein the cameras of the fourth array of cameras are aligned with one another along an axis perpendicular to a direction of workpiece motion, and have fields of view that do not overlap with one another, wherein the second and fourth arrays of cameras have fields of view that are staggered.

5. The optical inspection system of claim 1, and further comprising an encoder operably coupled to the workpiece transport to provide an indication of workpiece motion to the processing device.

6. The optical inspection system of claim 5, wherein the indication has a resolution of approximately 100 microns.

7. The optical inspection system of claim 1, wherein the illuminator includes at least one arc lamp.

8. The optical inspection system of claim 1, wherein the illuminator includes at least one light emitting diode.

9. The optical inspection system of claim 1, wherein the light pipe includes a plurality of reflective sidewalls.

10. The optical inspection system of claim 1, wherein the at least one reflective sidewall includes a curved reflective surface that preserves illumination elevation angle while mixing illumination azimuthally.

11. The optical inspection system of claim 1, wherein the illuminator includes at least one mirror disposed to reflect at least a portion of illumination to a desired source elevation angle.

12. The optical inspection system of claim 11, wherein the at least one mirror is angled to reflect the portion of illumination toward the at least one reflective sidewall at the desired elevation angle.

13. The optical inspection system of claim 1, wherein the illuminator includes an illumination mixing chamber disposed proximate the second end, and wherein the mixing chamber and the light pipe are separated by a translucent diffuser having at least one diffuser aperture aligned with each respective at least one second end aperture.

14. The optical inspection system of claim 13, wherein a first light source is configured to introduce strobed illumination into the mixing chamber.

15. The optical inspection system of claim 14, wherein a second light source is configured to introduce strobed illumination into the light pipe between the diffuser and the first end.

16. The optical inspection system of claim 15, and further comprising a third light source configured to introduce additional illumination into the light pipe between the diffuser and the first end.

17. The optical inspection system of claim 1, wherein the processing device includes a high-speed data transfer bus to provide the first, second, third and fourth pluralities of images to the other device.

18. The optical inspection system of claim 17, wherein the processing device is configured to simultaneously acquire and store images from the first and second arrays of cameras while providing images to the other device.

19. The optical inspection device of claim 18, wherein the high-speed data transfer bus operates in accordance with the peripheral component interconnect express (PCIe) bus.

20. The optical inspection system of claim 1, wherein the other device is configured to provide an inspection result relative to the feature on the workpiece based, at least in part, upon the first, second, third and fourth pluralities of images.

21. The optical inspection system of claim 1, and further comprising a structured light projector configured to project structured light onto the workpiece.

22. The optical inspection system of claim 21, wherein the structured light projector is configured to project a random dot pattern.

23. The optical inspection system of claim 21, wherein the structured light projector is configured to project at least one laser stripe.

24. The optical inspection system of claim 21, wherein the structured light projector is configured to project at least one sinusoidal fringe onto the workpiece.

25. The optical inspection system of claim 1, wherein the first and second arrays of cameras are angled with respect to a surface normal to the workpiece.

26. The optical inspection system of claim 1, wherein the first array of cameras is oriented to view the workpiece from an angle that is substantially perpendicular to a surface of the workpiece.

27. A method of inspecting an article of manufacture, the method comprising:

generating relative motion between the article of manufacture and a pair of camera arrays;

simultaneously acquiring a first set of images from a first camera array of the pair of camera arrays through a light pipe during the relative motion and while strobing a first illumination field type upon the article of manufacture;

generating at least a first stitched image with the first set of acquired images;

acquiring a second set of images from the second camera array through the light pipe while strobing the first illumination field type upon the article of manufacture;

generating at least a second stitched image from the second set of images acquired from the second camera array; and

determining the inspection result relative to the article of manufacture based, at least in part, upon the first and second stitched images.

28. The method of claim 27, and further comprising:

simultaneously acquiring a third set of images from the first camera array of the pair of camera arrays through a light pipe during the relative motion and while strobing a second illumination field type upon the article of manufacture;

generating at least a third stitched image with the third set of acquired images;

acquiring a fourth set of images from the second camera array through the light pipe while strobing the second illumination field type upon the article of manufacture;

generating at least a fourth stitched image from the fourth set of images acquired from the second camera array; and

determining the inspection result relative to the article of manufacture based, at least in part, upon the first, second, third and fourth stitched images.

29. The method of claim 28, wherein the first illumination field type is darkfield.

30. The method of claim 29, wherein the second illumination field type is cloudy day.

31. The method of claim 29, wherein the second illumination field type is brightfield.

32. The method of claim 28, wherein the first illumination field type is structured illumination.

33. The method of claim 28, wherein the first illumination field type is backlight.

34. The method of claim 33, wherein the backlight has a near-infrared wavelength.

35. The method of claim 28, wherein the first and second illumination field types are energized alternately.

36. The method of claim 27, wherein the image stitching is used to correct for positional error of the article of manufacture.

37. The method of claim 27, wherein stitching is used to correct for workpiece warpage.

38. The method of claim 27, and further comprising providing at least some images to an other device while collecting images from the pair of camera arrays.

39. The method of claim 27, wherein the pair of camera arrays are arranged to view the article stereoscopically, and wherein the method further comprises calculating three dimensional surface information based upon at least one of the first and second sets of images.

40. The method of claim 39, wherein the inspection result is based on two dimensional and three dimensional image data.

41. The method of claim 27, wherein the article of manufacture is a solar cell.

42. The method of claim 41, wherein the article of manufacture is a solar cell and wherein the method further comprises establishing a coordinate frame using solar cell fiducial marks.

43. The method of claim 41, wherein the inspection result is indicative of at least one of collector finger height, collector finger width, and collector finger registration.

44. The method of claim 41, wherein the inspection result is indicative of solar cell bowing.

45. The method of claim 41, wherein the inspection result is indicative of solar cell wafer geometry.

46. The method of claim 41, wherein the inspection result is indicative of the presence of chips in the solar cell.

47. The method of claim 41, wherein the inspection result is indicative of the presence of cracks in the solar cell.