Imaging method and apparatus

• US 20030189704A1
• Filed: 04/03/2002
• Published: 10/09/2003
• Est. Priority Date: 04/03/2002
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Masterman, James A., Floeder, Steven P.
• Granted Patent: US 7,023,542 B2
• Time in Patent Office: Days
• US Class Current: 356/239.1
• CPC Class Codes: G01N 21/896 Optical defects in or on transparent materials, e.g. distortion, surface flaws in conveyed flat sheet or rod for other objects G01N21/958

Abstract

The present invention relates to imaging apparatus and method for detecting optical properties of transparent media. The present invention superimposes, either optically or electronically, at least two images of the transparent media in order to obtain the optical properties. By superimposing the images, the present invention is capable of detecting various optical properties of the transparent medium in a single configuration.

Claims

1. A method for characterizing a transparent medium, comprising

(a) transmitting light from a point light source two times through said transparent medium and then through a lens onto a detector array to form an image of said transparent medium, wherein at least one converging mirror directs light to a point at a position substantially near the optical center of the lens;

and

(b) analyzing said image to characterize optical properties of said transparent medium.

2. A method according to claim 1, wherein said optical properties include defects, caliper, non-uniformities, clarity, optical density, diffusion or combinations thereof

3. A method according to claim 2, wherein defects include refracting defects, scattering defects, obstructing defects or combinations thereof.

4. A method according to claim 1, wherein said lens is focused on a plane corresponding to said transparent medium.

5. A method according to claim 1, wherein the combined distance between the point light source to the converging mirror and from the converging mirror to the detector array is about four times the focal length of the mirror.

6. A method according to claim 1, wherein a beam splitter is utilized to align light so that a first pass of light from said point light source through said transparent medium is coaxial with a second pass of light from said mirror through said transparent medium.

7. A method according to claim 1, wherein said point light source is selected from apertured lamps, fiber optic light or light emitting diodes.

8. A method according to claim 1, wherein said transparent medium is polymeric films, glass, coated films or coated glass.

9. A method according to claim 1, wherein the detector array is one-dimensional or two-dimensional.

10. A method according to claim 1, wherein said image is analyzed using filtering, blob analysis, thresholding or combinations thereof.

11. A method according to claim 1, further comprising identifying locations of one or more defects on said transparent medium.

12. A method according to claim 1, further comprising quantifying optical properties of said transparent medium.

13. A method according to claim 1, wherein said transparent medium includes webs or discrete parts.

14. A method according to claim 1, wherein said defects are one micron or greater.

15. A method according to claim 1, wherein said detector arrays include CCD, CMOS, or photodiodes.

16. A method according to claim 1, further comprising adjusting processing of said transparent medium based on said optical properties.

17. A method according to claim 1, wherein said light impacts said transparent medium in a telecentric manner.

25. A method according to claim 1, wherein said image is analyzed using filtering, blob analysis, thresholding or combinations thereof.

18. A method for characterizing a transparent medium, comprising

(a) passing light from a point light source through said transparent medium onto a converging mirror;

(b) reflecting light from said converging mirror back through said transparent medium and through a lens onto a detector array to form an image of said transparent medium, wherein light from said mirror converges to a point at a position substantially near the optical center of the lens; and

(c) analyzing said image to characterize optical properties of said transparent medium.

19. A method of characterizing a transparent medium, comprising,

superimposing two or more images of a transparent medium wherein each image is generated by reflecting light emitted from a point light source from a converging mirror such that the light converges to a single point substantially near the center of a lens with said light transmitting through said transparent medium either before or after reflecting from the mirror, wherein the two or more images are formed, each having unique focal planes, such that one of the unique focal planes corresponds to the transparent medium.

20. A method according to claim 19, wherein, the images are superimposed through a single lens onto a detector array.

21. A method according to claim 19, wherein, the images are formed using two or more lenses with separate detector arrays, and signals from said detector arrays are superimposed electronically.

22. A method according to claim 19, further comprising analyzing said superimposed image to characterize optical properties of said transparent medium.

23. A method according to claim 22, wherein said optical properties include defects, caliper, non-uniformities, clarity, optical density, diffusion or combinations thereof.

24. A method according to claim 23, wherein defects include refracting defects, scattering defects, obstructing defects or combinations thereof.

26. A method according to claim 22, further comprising quantifying optical properties of said transparent medium.

27. A method according to claim 19, further comprising adjusting processing of said transparent medium based on said optical properties.

28. An apparatus for detecting optical characteristics in a transparent medium, comprising

(a) a point light source for transmitting light through said transparent medium;

(b) a converging mirror for reflecting said light back through said transparent medium and to a point at a position substantially near the optical center of the lens;

(c) a detector array for receiving an image from said lens; and

(d) an analyzing device for analyzing said image to determine optical properties of said transparent medium.

29. An apparatus according to claim 28, wherein said optical properties include defects, caliper, non-uniformities, clarity, optical density, diffusion or combinations thereof.

30. An apparatus according to claim 29, wherein said defects include refracting defects, scattering defects, obstructing defects or combinations thereof.

31. An apparatus according to claim 28, wherein said lens is focused on a plane corresponding to said transparent medium.

32. An apparatus according to claim 28, wherein the combined distance between the point light source to the converging mirror and from the converging mirror to the detector array is about four times the focal length of the mirror.

33. An apparatus according to claim 28 further comprising a beam splitter to align the light so that a first pass of light from said point light source through said transparent medium is co-axial with a second pass of light from said mirror through said transparent medium.

34. An apparatus according to claim 28, wherein said point light source includes apertured lamps, fiber optic light or light emitting diodes.

35. An apparatus according to claim 28, wherein said transparent medium is polymeric films, glass, coated films or coated glass.

36. An apparatus according to claim 28, wherein the detector array is one-dimensional or two-dimensional.

37. An apparatus according to claim 28, wherein said image is analyzed using filtering, blob analysis, thresholding or combinations thereof.

38. An apparatus according to claim 28, wherein said analyzing device identifies locations of one or more defects on said transparent medium.

39. An apparatus according to claim 28, wherein said transparent medium includes webs or discrete parts.

40. An apparatus according to claim 29, wherein said defects are one micron or greater.

41. An apparatus according to claim 28, wherein said detector arrays include CCD, CMOS, or photodiodes.

42. An apparatus according to claim 29, further comprising processing said transparent medium based on said defects.

43. An apparatus according to claim 28, wherein said light impacts said transparent medium in a telecentric manner.

44. An apparatus for superimposing two or more images of a transparent medium, comprising:

two or more imaging systems, each system having a point light source for transmitting light through a transparent medium, a converging mirror positioned such that light from the point light source converges to a point substantially near a center of an imaging lens, and a detector array for receiving an image from said lens, wherein each system generates an image, each image having unique focal planes, such that one of the unique focal planes corresponds to the transparent medium.

45. An apparatus according to claim 44, wherein, the images are superimposed through a single lens onto a detector array.

46. An apparatus according to claim 44, wherein, the images are formed using two or more lenses with separate detector arrays, and signals from said detector arrays are superimposed electronically.

47. An apparatus according to claim 44, wherein said optical properties include defects, caliper, non-uniformities, clarity, optical density, diffusion or combinations thereof.

48. An apparatus according to claim 44, wherein defects include refracting defects, scattering defects, obstructing defects or combinations thereof.

49. An apparatus according to claim 44, wherein said image is analyzed using filtering, blob analysis, thresholding or combinations thereof.