Light wedge for illuminating a platen in a print scanner

• US 20030206287A1
• Filed: 04/09/2003
• Published: 11/06/2003
• Est. Priority Date: 01/17/2002
• Status: Active Grant

• Current Assignee: Cross Match Technologies Incorporated (Assa Abloy AB)
• Original Assignee: Cross Match Technologies Incorporated (Assa Abloy AB)
• Inventors: McClurg, Geroge W., Fedele, Dean J.
• Granted Patent: US 6,867,850 B2
• Time in Patent Office: Days
• US Class Current: 356/71
• CPC Class Codes: G06V 10/145 Illumination specially adapted for pattern recognition, e.g. using gratings
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence

Abstract

Light wedges that reflect light internally and produce diffuse light for uniformly illuminating a platen in a print scanner are presented. In one example, a light wedge has a first surface that receives light emitted from an illumination source and a second surface that limits specular reflections. The light wedge transmits light from the illumination source toward the platen, whereby uniform illumination is provided to the platen. In another example, a light wedge has an illumination surface that receives light emitted from the illumination source, a first surface that limits specular reflections, and a second surface that acts as a diffuser. The second surface reflects light out of the light wedge toward the platen, whereby uniform illumination is provided to the platen.

Claims

1. An illumination system that provides uniform illumination for a platen in a print scanner, comprising:

an illumination source array that emits light from a plurality of discrete light sources; and

a light wedge having an illumination surface that receives light emitted from said illumination source array, a first painted surface that limits specular reflections, and a second painted surface that acts as a diffuser, wherein said second painted surface reflects light out of said light wedge toward the platen, and whereby uniform illumination is provided to the platen.

2. The illumination system of claim 1, wherein said first painted surface is ground prior to being painted.

3. The illumination system of claim 1, wherein said second painted surface is ground prior to being painted.

4. The illumination system of claim 1, further comprising:

a diffuser provided near said light wedge such that light passing out from said light wedge passes through said diffuser before illuminating the platen.

5. The illumination system of claim 4, wherein said diffuser comprises a holographic diffuser.

6. The illumination system of claim 1, wherein said illumination source array comprises a plurality of sources that emit color light.

7. The illumination system of claim 6, wherein the color light is blue/green light.

8. The illumination system of claim 6, wherein the color light is red light.

9. The illumination system of claim 6, wherein said first painted surface is painted with a color similar to the color light emitted by said plurality of sources.

10. The illumination system of claim 6, wherein said second painted surface is painted with a color similar to the color light emitted by said plurality of sources.

11. The illumination system of claim 1, wherein said plurality of sources are divided into at least two separately controllable groups of lights.

12. The illumination system of claim 1, wherein said plurality of sources are divided into at least a center region and a perimeter region, wherein the density of sources provided in said perimeter region is greater than in said center region.

13. The illumination system of claim 1, wherein the intensity of each source can be independently controlled relative to other sources such that a flat, uniform illumination is provided to the platen.

14. The illumination system of claim 1, wherein said first painted surface is painted with a green paint.

15. The illumination system of claim 1, wherein said second painted surface is painted with a green paint.

16. The illumination system of claim 1, wherein said first painted surface and said second painted surface are painted with a paint having a color other than white.

17. The illumination system of claim 1, wherein said first painted surface and said second painted surface are painted with a green paint.

18. An illumination system that provides uniform illumination for a platen in a print scanner, comprising:

an illumination source that emits light; and

a light wedge having a first surface that receives light emitted from said illumination source and a second surface that limits specular reflections, wherein said light wedge transmits light from said illumination source toward the platen, and whereby uniform illumination is provided to the platen.

19. The illumination system of claim 18, wherein said light wedge is a Type-1 light wedge.

20. The illumination system of claim 18, wherein said light wedge is a Type-2 light wedge.

21. The illumination system of claim 18, wherein said light wedge is a Type-3 light wedge.

22. The illumination system of claim 18, wherein said light wedge is a Type-4 light wedge.

23. The illumination system of claim 18, wherein said second surface is ground.

24. The illumination system of claim 18, wherein said second surface is painted.

25. The illumination system of claim 24, wherein said second surface is painted with a paint having a color other than white.

26. The illumination system of claim 25, wherein said second surface is painted with a green paint.

27. The illumination system of claim 18, wherein said illumination source array comprises a plurality of sources that emit color light.

28. The illumination system of claim 27, wherein the color light is blue/green light.

29. The illumination system of claim 27, wherein the color light is red light.

30. The illumination system of claim 27, wherein said second surface is painted with a color similar to the color light emitted by said plurality of sources.

31. A print scanner having an illumination source and a platen, the print scanner comprising:

a light wedge having an illumination surface that receives light emitted from the illumination source, a first surface that limits specular reflections, and a second surface that acts as a diffuser, wherein said second surface reflects light out of said light wedge toward the platen, and whereby uniform illumination is provided to the platen.

32. The print scanner of claim 31, wherein said first surface is painted.

33. The print scanner of claim 32, wherein said first surface is ground prior to being painted.

34. The print scanner of claim 32, wherein said first surface is painted with a paint having a color other than white.

35. The print scanner of claim 34, wherein said first surface is painted with a green paint.

36. The print scanner of claim 31, wherein a diffused and absorbing material is optically coupled to said first surface.

37. The print scanner of claim 36, wherein said diffused and absorbing material is tape.

38. A light wedge for providing uniform illumination across a scanning area of a platen, comprising:

a first surface that passes light emitted from an illumination source into the light wedge, a second surface that limits specular reflections, and a third surface that outputs light internally transmitted and reflected within the light wedge toward the platen, whereby uniform illumination is provided to the platen.

39. The light wedge of claim 38, wherein said light wedge is a Type-1 light wedge.

40. The light wedge of claim 38, wherein said light wedge is a Type-2 light wedge.

41. The light wedge of claim 38, wherein said light wedge is a Type-3 light wedge.

42. The light wedge of claim 38, wherein said light wedge is a Type-4 light wedge.

43. The light wedge of claim 38, wherein said second surface is ground.

44. The light wedge of claim 38, wherein said second surface is painted.

45. The light wedge of claim 44, wherein said second surface is painted with a paint having a color other than white.

46. The light wedge of claim 45, wherein said second surface is painted with a green paint.

47. The light wedge of claim 38, wherein a diffused and absorbing material is optically coupled to said second surface.

48. The light wedge of claim 47, wherein said diffused and absorbing material is tape.