Diffractive optical element and method of manufacture

• US 6,998,196 B2
• Filed: 12/28/2001
• Issued: 02/14/2006
• Est. Priority Date: 12/28/2001
• Status: Active Grant

• Current Assignee: Wavefront Technology, Inc.
• Original Assignee: Wavefront Technology, Inc.
• Inventors: Petersen, Joel, Rich, Chris
• Primary Examiner(s): ANGEBRANNDT, MARTIN J
• Application Number:
  US10/036,198
• Publication Number:
  US 20030124435A1
• Time in Patent Office: 1,509 Days
• Field of Search: 430/1, 430/2, 359/12
• US Class Current: 430/1
• CPC Class Codes: B29C 2035/0827 using UV radiation
• CPC Class Codes: B29C 2059/023 Microembossing
• CPC Class Codes: B29C 35/0888 using transparant moulds
• CPC Class Codes: B29C 59/022 characterised by the disposition or the configuration, e.g. dimensions, of the embossments or the shaping tools therefor
• CPC Class Codes: B29C 59/046 for layered or coated substantially flat surfaces
• CPC Class Codes: G03H 1/0244 Surface relief holograms replicating hologram without interference recording G03H1/0276
• CPC Class Codes: G03H 1/0276 Replicating a master hologram without interference recording surface relief holograms G03H1/0244
• CPC Class Codes: G03H 1/202 Contact copy when the reconstruction beam for the master H1 also serves as reference beam for the copy H2
• CPC Class Codes: G03H 2001/0284 by moulding
• CPC Class Codes: G03H 2001/2615 in physical contact, i.e. layered holograms
• CPC Class Codes: G03H 2001/2635 Mixed volume and surface relief holograms

Abstract

A diffractive optical element such as a diffuser, diffraction grating, and/or hologram, can be manufactured by using a surface relief pattern on a surface of a surface relief tool. A layer of curable material is physically contacted with the surface relief pattern on the surface of the surface relief tool to thereby imprint the pattern on a surface of the layer. Diffractive features are formed in the layer by propagating energy through the surface relief tool and into the layer such that refractive index variations corresponding to the pattern are created in the layer. The resultant product is a diffractive optical element comprising a layer of material having diffractive features formed by a predetermined pattern of refractive index variations. The diffractive features originate at an undulating boundary and extend only from one side of the boundary into the material. The undulating boundary has an undulating pattern that corresponds to the predetermined pattern of refractive index variations.

Claims

1. A method of using a medium having a surface relief pattern on a surface thereof to manufacture a volume holographic diffractive optical element, said method comprising:

physically contacting a layer of curable material comprising optical liquid with said surface relief pattern on said surface of said medium to thereby imprint said pattern on a surface of the layer; and

curing said curable material to form said volume holographic optical element, said curing comprising forming diffractive features comprising refractive index variations in said layer that correspond to said pattern, said forming comprising propagating energy through said medium and from said medium into said layer and producing said volume holographic optical element through non-interference effects.

2. The method of claim 1, wherein said energy comprises electromagnetic energy.

3. The method of claim 2, wherein said electromagnetic energy comprises ultraviolet (UV) light.

4. The method of claim 2, wherein said electromagnetic energy comprises light.

5. The method of claim 1, wherein said medium is substantially optically transmissive.

6. The method of claim 5, wherein said medium is substantially optically transmissive to ultraviolet (UV) radiation.

7. The method of claim 5, wherein said medium has an index of refraction that is substantially the same as the index of refraction of the curable material.

8. The method of claim 1, wherein said energy is in the form of an electron beam.

9. The method of claim 1, further comprising removing said medium from said curable material.

10. The method of claim 1, wherein said medium is selected from the group consisting of tape and a drum.

11. The method of claim 1, wherein said medium comprises a surface relief hologram.

12. The method of claim 1, wherein said curable material comprises a polymer selected from the group consisting of urethane, acrylate, and epoxy.

13. The method of claim 1, wherein said contacting creates an interface between said medium and said layer, said interface having a pattern corresponding to said surface relief pattern, said method further comprising using said interface pattern to mechanically influence the orientation of optical liquid in said layer.

14. The method of claim 13, wherein said optical liquid comprises liquid crystal.

15. The method of claim 14, wherein said liquid crystal comprises nematic liquid crystal.

16. The method of claim 15, wherein said nematic liquid crystal comprises materials selected from the group consisting of E7 materials, BL material, and TL compounds.

17. The method of claim 15, wherein said nematic liquid crystal comprises materials selected from the group consisting of mixtures of cyanobiphenyls and higher aromatic homologues, and mixtures of chloro and fluoro substituted mesogens.

18. The method of claim 12, wherein said layer has a surface opposite said interface, the method further comprising propagating energy through said interface pattern towards said opposite surface.

19. The method of claim 1, additionally comprising further curing said curable material.

20. The method of claim 19, wherein said further curing comprises exposing said curable material to additional energy.

21. The method of claim 20, wherein said energy comprises electromagnetic energy.

22. The method of claim 21, wherein said electromagnetic energy comprises UV light.

23. The method of claim 21, wherein said energy comprises heat.

24. The method of claim 1, wherein said optical liquid comprises liquid crystal and said method further comprises surrounding said curable material with a pair of electrodes for applying an electrical field across said liquid crystal to alter optical characteristics of said curable material.

25. The method of claim 24, further comprises providing electrically conductive substantially optically transmissive material to form said electrodes.

26. The method of claim 25, comprising depositing indium tin oxide (ITO) to form at least one of said electrodes.

27. The method of claim 24, further comprises laminating electrically conductive substantially optically transmissive material to form said electrodes.

28. The method of claim 24, further comprising:

removing said medium having a surface relief pattern from said layer of curable material; and

forming an index matching layer against said imprinted pattern on said layer of curable material, said index matching layer comprising material that has an index of refraction substantially identical to that of said curable material.

29. The method of claim 28, wherein said index matching layer is electrically conductive.

30. The method of claim 1, wherein said holographic diffractive optical element comprises a diffuser.

31. The method of claim 1, wherein said holographic diffractive optical element comprises a diffraction grating.

32. A method of using first and second media having first and second surface relief patterns on respective surfaces thereof to manufacture a volume holographic diffractive optical element, said method comprising:

physically contacting a layer of curable material comprising optical liquid with said first surface relief pattern on said surface of said first medium to thereby imprint said first pattern on a surface of the layer;

curing said curable material, said curing comprising forming diffractive features comprising refractive index variations in said layer that correspond to said first pattern on said first medium, said forming comprising propagating energy through said first medium and from said first medium into said layer and producing said holographic diffractive optical element through non-interference effects; and

physically contacting said layer of curable material comprising optical liquid with said surface relief features on said surface of said second medium to thereby imprint said second pattern on another surface of the layer such that two surface relief patterns on opposite sides of said layer surround said index of refraction variations.

33. A non-holographic method of using a medium having a surface relief pattern on a surface thereof to manufacture a volume hologram, said non-holographic method comprising:

physically contacting a layer of curable material comprising optical liquid with said surface relief pattern on said surface of said medium to thereby imprint said pattern on a surface of said layer; and

non-holographically forming volume holographic diffractive features in said layer by propagating energy through said medium and from said medium into said layer such that refractive index variations corresponding to said pattern are created in said layer thereby producing said volume hologram.

34. The method of claim 33, wherein said optical liquid comprises liquid crystal.

35. The method of claim 34, further comprising providing electrodes on opposite sides of said curable material for applying an electric field across said layer of curable material to alter one or more optical characteristics thereof.

36. The method of claim 35, further comprising forming a pair of layers of electrically conductive substantially optically transmissive material as said electrodes.

37. The method of claim 36, comprising providing indium tin oxide (ITO) to form said electrodes.

38. The method of claim 37, further comprising:

removing said medium having a surface relief pattern from said layer of curable material; and

forming an index matching layer against said imprinted pattern on said layer of curable material, said index matching layer comprising material that has an index of refraction substantially identical to that of said curable material.

39. The method of claim 38, wherein said index matching layer is electrically conductive.

40. A method of using surface relief features on a surface of a medium to manufacture a volume hologram comprising:

physically contacting said surface relief features on said surface of said medium with a surface of a layer of curable material comprising optical liquid; and

forming said volume hologram by forming a pattern of diffractive features comprising refractive index variations in said layer by propagating electromagnetic energy through the surface relief features of the medium and from the medium into said layer, the formation of said pattern of diffractive features being dependent on said surface relief features, and substantially independent of any diffraction of said energy by said surface relief features during propagation through said medium.

41. The method of claim 40, wherein said curable material comprises a polymer selected from the group consisting of urethane, acrylate, and epoxy.

42. The method of claim 40, wherein said electromagnetic energy comprises ultraviolet light.

43. The method of claim 40, wherein said physically contacting surface relief features comprises forming indentations in said layer of curable material.

44. The method of claim 40, wherein said medium comprise a surface relief hologram.

45. A method of utilizing a medium having a surface relief pattern on a surface thereof to manufacture a volume holographic optical element having a multiplicity of diffractive features comprising:

physically contacting said surface relief pattern with a layer of curable material comprising optical liquid such that said pattern and said layer are in contact over a contact area of said layer; and

forming said diffractive features comprising refractive index variations in said layer by illuminating said contact area with light having an intensity distribution substantially free of interference fringes, said diffractive features forming said volume holographic optical element.

46. The method of claim 45, wherein said volume holographic optical element is selected from the group consisting of a hologram of an object, a diffraction grating, and a diffuser.

47. The method of claim 45, wherein said illuminating comprises directing substantially incoherent light on said contact area.

48. The method of claim 47, wherein said incoherent light has a coherence length of less than or equal to about several wavelengths.

49. The method of claim 47, wherein said contact area is illuminated with white light.

50. The method of claim 47, wherein said contact area is illuminated with sunlight.

51. The method of claim 47, wherein said illuminating comprises directing light from a light source selected from the group consisting of an arc lamp, an incandescent lamp, and a fluorescent lamp onto said contact area.

52. The method of claim 45, wherein said optical liquid comprises liquid crystal.

53. The method of claim 52, further comprising providing electrodes on opposite sides of said curable material for applying an electric field across said layer of curable material to alter one or more optical characteristics thereof.

54. The method of claim 53, further comprising forming a pair of layers of electrically conductive substantially optically transmissive material as said electrodes.

55. The method of claim 54, comprising providing indium tin oxide (ITO) to form said electrodes.

56. The method of claim 53, further comprising:

removing said medium having a surface relief pattern from said layer of curable material; and

forming an index matching layer against said imprinted pattern on said layer of curable material, said index matching layer comprising material that has an index of refraction substantially identical to that of said curable material.

57. The method of claim 56, wherein said index matching layer is electrically conductive.

58. A method of manufacturing a volume holographic diffractive optical element using a first medium having a first surface relief pattern on a surface thereof and a second medium having a second surface relief pattern on a surface thereof, said method comprising:

physically contacting one side of a layer of curable material comprising optical liquid with said first surface relief pattern on said surface of said medium to thereby imprint said pattern on said side of the layer;

physically contacting another side of a layer of curable material with said second surface relief pattern on said surface of said medium to thereby imprint said pattern on said another side of the layer; and

curing said curable material to form said holographic diffractive optical element, said curing comprising forming diffractive features comprising refractive index variations in said layer that correspond to said pattern, said forming comprising propagating energy through said first medium and from said first medium into said layer and producing said diffractive features through non-interference effects.

59. The method of claim 58, wherein said optical liquid comprises liquid crystal and said method further comprises surrounding said curable material with a pair of electrodes for applying an electrical field across said liquid crystal to alter optical characteristics of said curable material.

60. The method of claim 59, further comprising providing electrically conductive substantially optically transmissive material to form said electrodes.

61. The method of claim 60, comprising providing indium tin oxide (ITO) to form said electrodes.