Tapered multilayer luminaire devices

• US 5,528,720 A
• Filed: 04/11/1994
• Issued: 06/18/1996
• Est. Priority Date: 03/23/1992
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Company
• Inventors: Gleckman, Philip, Winston, Roland, Emmons, Robert M., Holman, Robert L., Jacobson, Benjamin A.
• Primary Examiner(s): SCHOEPPEL, ROGER J
• Assistant Examiner(s): Palmer, Phan T. H.
• Application Number:
  US08/266,016
• Time in Patent Office: 799 Days
• Field of Search: 385/146, 385/147, 385/140, 385/129, 385/130, 385/131, 385/43, 385/901, 359/48, 359/50, 359/599, 359/833, 359/834, 359/869, 362/19, 362/31, 362/32
• US Class Current: 385/146
• CPC Class Codes: F21V 5/02 of prismatic shape F21V5/04 takes precedence
• CPC Class Codes: G02B 6/0001 specially adapted for lighting devices or systems lighting or signalling on vehicles using light guides B60Q1/00; lighting devices for vehicle dashboards B60Q3/10; lighting devices for vehicle interior using light guides B60Q3/62; lighting devices mounted on the vehicle rear part using light guides F21S43/235; measuring arrangements having light conducting pointers G01D13/265; illumination of liquid crystal displays G02F1/1336; illuminated signs G09F13/00
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• CPC Class Codes: G02B 6/4298 coupling with non-coherent light sources and/or radiation detectors, e.g. lamps, incandescent bulbs, scintillation chambers
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/13355 Polarising beam splitters [PBS]
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G09F 13/00 Illuminated signs; Luminous advertising G09F9/00, G09F11/00 take precedence; control of displays in general using static means to present variable information G09G
• CPC Class Codes: G09F 13/0409 Arrangements for homogeneous illumination of the display surface, e.g. using a layer having a non-uniform transparency arrangements of reflectors G09F13/14
• CPC Class Codes: G09F 2013/05 indicating exit way or orientation
• CPC Class Codes: G09F 2013/1827 Prismatic window
• CPC Class Codes: Y10S 385/901 Illuminating or display apparatus

Abstract

An optical device for collecting light and selectively outputting or concentrating the light. A wedge layer has an optical index of refraction n₁, and top, bottom and side surfaces intersecting to define an angle of inclination φ. A back surface spans the top, bottom and side surface. A first layer is coupled to the bottom surface of the layer and has an index of refraction n₂. The first layer index n₂ causes light input through the back surface of the layer to be preferentially output into the first layer. A second layer is coupled to the bottom of the first layer and selectively causes output of light into ambient. Additional layers, such as a light polarization layer, a polarization converting layer and a post LCD diffuser layer can be used to make preferential use of polarized light or diffuse light having passed through the LCD layer to enhance viewing of the output light.

Claims

1. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having a wedge-shaped cross-sectional area and having an optical index of refraction n₁, and a first and a second surface converging to define at least one angle of inclination φ

, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected therein decreases its angle relative to the normal to at least one of said first and second layer surfaces and achieves an angle of incidence less than a critical angle θ

_c relative to the normal;

first layer means including a layer having index n₂ less than n₁ disposed beyond said second surface relative to said base layer and for enabling light to enter said first layer means after output from said base layer when the light in said base layer achieves the angle of incidence less than the critical angle θ

_c characteristic of an interface between the base layer and said layer of index n₂ ; and

second layer means for preferably outputting light of a first polarization state compared to a second polarization state, said second layer means being disposed beyond said second surface relative to said base layer and said second layer means further able to reflect at least part of the light having the second polarization state.

2. The optical device as defined in claim 1 wherein at least one of said first and second layer means comprises a light converting means for at least partially changing light of one polarization to another polarization.

3. The optical device as defined in claim 1 further including light redirecting layer means for changing the angle of light for output to the viewer.

4. The optical device as defined in claim 3 wherein said light redirecting means further comprises means for controlling angular range of light output.

5. The optical device as defined in claim 3 further including converting means for at least partially changing light of one polarization to light of another polarization.

6. The optical device as defined in claim 5 wherein said converting means comprises a birefringent layer.

7. The optical device as defined in claim 1 further including light converting means for changing light of the second polarization state to light of the first polarization state.

8. The optical device as defined in claim 7 wherein said second layer means is disposed on the opposite side of said base layer relative to said converting means.

9. The optical device as defined in claim 7 further including light redirecting means for controlling angular range of light to be output from said device, said second layer means being disposed on the same side of said base layer as said light redirecting means and also closer to said base layer than said light redirecting means.

10. The optical device as defined in claim 1 further including light redirecting means for controlling angular range of light to be output from said optical device.

11. The optical device as defined in claim 1 wherein said base layer includes an additional layer coupled thereto.

12. The optical device as defined in claim 1 further including at least one intervening layer disposed between said base layer and said first layer means, said intervening layer allowing transmission of at least part of the light and said intervening layer wherein said first layer means is comprised of at least an air gap.

13. The optical device as defined in claim 1 wherein said first layer means is disposed one of (a) further from said second surface than said second layer means and (b) nearer said second surface than said second layer means.

14. The optical device as defined in claim 1 further including a liquid crystal display disposed adjacent said device with light redirected to said display by said optical device.

15. The optical device as defined in claim 1 wherein said first layer means includes an air gap.

16. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having a wedge-shaped cross-sectional area and having an optical index of refraction n₁, and a first and a second surface converging to define at least one angle of inclination φ

, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected therein decreases its angle relative to the normal to at least one of said first and second layer surfaces and achieves an angle of incidence less than a critical angle θ

_c relative to the normal; and

layer means coupled to said base layer for preferably outputting light of a first polarization state compared to a second polarization state, said layer means further able to reflect at least part of the light having the second polarization state.

17. The optical device as defined in claim 16 wherein said layer means includes a layer with index of refraction n₂ less than n₁.

18. The optical device as defined in claim 17 wherein said layer means is coupled directly to said base layer.

19. The optical device as defined in claim 17 wherein said layer means includes an air gap.

20. The optical device as defined in claim 17 wherein said layer means comprises light converting means for at least partially changing light of one polarization to light of another polarization and also includes light redirecting layer means for operating on the light to control the angular output range of the light to the viewer.

21. The optical device as defined in claim 20 wherein said light converting means and said light redirecting layer means are disposed adjacent one another.

22. The optical device as defined in claim 20 wherein said light converting means comprises a birefringent layer.

23. The optical device as defined in claim 22 wherein said birefringent layer is disposed on one side of said base layer compared to said light redirecting layer means.

24. The optical device as defined in claim 17 wherein said layer means comprises a birefringent layer, converting means for changing light of the second polarization state to light of the first polarization state and light redirecting layer means for operating on the light to exert control over angular output range of the light to the viewer.

25. The optical device as defined in claim 24 wherein said light redirecting layer means is disposed further from said base layer than said birefringent layer and said converting means.

26. The optical device as defined in claim 25 wherein said converting means is disposed closer to said base layer than said birefringent layer.

27. The optical device as defined in claim 17 wherein said layer means further provides light of the first polarization state being transmitted through said first surface of said base layer and part of the light of the second polarization state being transmitted through said second surface of said base layer.

28. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having a wedge-shaped cross-sectional area and having an optical index of refraction n₁, and a first and second surface converging to define at least one angle of inclination φ

, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected therein decreases its angle relative to the normal to at least one of said first and second surfaces and achieves an angle of incidence less than a critical angle θ

_c relative to the normal;

first layer means including an air gap disposed beyond said second surface relative to said base layer and for enabling light to enter said air gap after output from said base layer when the light in said base layer achieves the angle of incidence less than the critical angle θ

_c characteristic of an interface between the base layer and said air gap,

second layer means for preferably outputting light of a first polarization state compared to a second polarization state, said second layer means also disposed beyond said second surface relative to said base layer and said second layer means further enabling reflection of at least part of the light of the second polarization state; and

light redirecting means for operating on light having passed through said base layer to enable the light to be output from said device.

29. The optical device as defined in claim 28, wherein said redirecting means includes means for operating on the light having passed through said second layer means to control angular output of the light.

30. The optical device as defined in claim 29 wherein said light redirecting means operates on said reflected light and redirects the reflected light toward said second layer means.

31. The optical device as defined in claim 30 wherein said light redirecting means is disposed beyond said top surface relative to said base layer.

32. The optical device as defined in claim 31 wherein said light redirecting means includes at least a reflecting layer.

33. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having a wedge-shaped cross-sectional area and having an optical index of refraction n₁, and a first and second surface converging to define at least one angle of inclination φ

, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected therein decreases its angle relative to the normal to at least one of said first and second surfaces and achieves an angle of incidence less than a critical angle θ

_c relative to the normal;

first layer means comprising an air gap layer disposed at least beyond said first surface relative to said base layer and for enabling light to enter said first layer means after output from said base layer when the light in said base layer achieves the angle of incidence less than the critical angle θ

_c characteristic of an interface between said base layer and said air gap layer; and

second layer means for preferably outputting light of a first polarization state compared to a second polarization state, said second layer means disposed beyond said second surface relative to said base layer and said second layer means including an air gap and further enabling reflection of at least part of the light having the second polarization state.

34. The optical device as defined in claim 33 further including a redirecting layer overlying said first layer, said redirecting layer transmitting light toward the viewer over a controlled angular range.

35. The optical device as defined in claim 33 wherein said second layer means further comprises converting means for changing at least part of the light of the second polarization state to provide light of the first polarization state for output to the viewer.

36. The optical device as defined in claim 35 wherein said second layer means converts light from the second to the first polarization state with at least a ten percent efficiency.

37. The optical device as defined in claim 35 wherein said means for changing polarization has an index of refraction n>

1.4, thickness>

5 μ

m and is birefringent such that Δ

n>

0.05.

38. The optical device as defined in claim 37 wherein said birefringent second layer means is selected from the group consisting of polyester, acrylic and polycarbonate materials.

39. The optical device as defined in claim 33 wherein said second layer means causes less than a ten percent change of angular distribution of the light output to the viewer for light incident at an angle x relative to the surface normal wherein, ##EQU11## where n₁ =index of refraction of said base layer and n₂ =index of refraction of said first layer means.

40. The optical device as defined in claim 33 further including third layer means disposed between said base layer and the viewer, said third layer means for converting light of one polarization state to another polarization state.

41. The optical device as defined in claim 40 wherein said third layer means further includes a liquid crystal layer electrically activated for converting the polarization of light passing therethrough from one polarization state to another polarization state.

42. The optical device as defined in claim 33 further including an air gap layer between said liquid crystal layer and a separate layer portion forming said third layer means, for converting light from the first to the second polarization state.

43. The optical device as defined in claim 33 wherein said second layer means is transparent to light having both the first and second polarization states.

44. The optical device as defined in claim 33 wherein said birefringent second layer means comprises at least one of a biaxially oriented layer and a uniaxially oriented layer of birefringent material.

45. The optical device as defined in claim 33 wherein the light comprises at least one of linearly polarized light, circularly polarized light and elliptically polarized light.

46. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having a wedge-shaped cross-sectional area and having an optical index of refraction n₁, and a first and a second surface converging to define at least one angle of inclination φ

, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected therein decreases its angle relative to the normal to at least one of said first and second surfaces and achieves an angle of incidence less than a critical angle θ

_c relative to the normal;

first layer means including an air gap at least one of disposed beyond said first surface and beyond said second surface relative to said base layer and having an optical index of refraction n₂ for allowing transmission of light received from said base layer; and

converting layer means for changing light of one polarization state to another polarization state, said converting layer means disposed at least one of overlying and underlying said base layer.

47. The optical device as defined in claim 46 further including a reflecting layer beyond said second surface relative to said base layer for reflecting light of the second polarization state received from said base layer.

48. The optical device as defined in claim 47 further including means beyond said reflecting layer relative to said base layer for rotating light of the second polarization state to provide light of the first polarization state for output to the viewer.

49. The optical device as defined in claim 48 further including third layer means disposed between said first layer and the viewer, said third layer means for converting light of the first polarization state to light having an LCD preferred polarization state.

50. The optical device as defined in claim 49 wherein said third layer means comprises a birefringent layer.

51. The optical device as defined in claim 46 further including light redirecting means at least one of overlying and underlying said first layer means, said redirecting means for selectively redirecting light output from said first layer means.

52. The optical device as defined in claim 46 further including second layer means for preferably transmitting light of one polarization relative to another.

53. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having a wedge-shaped cross-sectional area and having an optical index of refraction n₁, and a first and a second surface converging to define at least one angle of inclination φ

, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected therein decreases its angle relative to the normal to at least one of said first and second surfaces and achieves an angle of incidence less than a critical angle θ

_c relative to the normal;

first layer means including an air gap beyond said second surface relative to said base layer and said base layer first surface for enabling light to enter said layer means from said base layer when the light in said base layer achieves the angle of incidence less than the critical angle θ

_c characteristic of the interface between the base layer and the layer means;

light redirecting means for operating on light having passed through said base layer and for outputting the light toward the viewer; and

second layer means disposed in a layer position being a layer beyond said first surface relative to said base layer and being a layer beyond said light redirecting means relative to said base layer, said second layer means for preferably transmitting light of a first polarization state compared to a second polarization state and for preferably reflecting light of the second polarization state.

54. The optical device as defined in claim 53 wherein said second layer means is disposed beyond said first surface relative to said base layer and the optical device further includes another light redirecting means disposed beyond both said second layer means and said first surface relative to said base layer.

55. The optical device as defined in claim 53 wherein said redirecting means comprises at least one of a reflective layer able to reflect light and a transmissive layer able to modify the angular distribution of light passing therethrough.

56. The optical device as defined in claim 53 wherein said second layer means is disposed beyond a first one of said light redirecting means, relative to said base layer, with an air gap disposed between said base layer and said second layer means and another air gap disposed between said second layer means and a second one of said light redirecting means.

57. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having a wedge-shaped cross-sectional area and having an optical index of refraction n₁, and a first and a second surface converging to define at least one angle of inclination φ

, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected therein decreases its angle relative to the normal to at least one of said first and second surfaces and achieves an angle of incidence less than a critical angle θ

_c relative to the normal;

first layer means including an air gap at least one of disposed beyond said first surface relative to said base layer and beyond said bottom layer surface relative to said base layer and having an optical index of refraction n₂ for allowing transmission of light received from said base layer;

second layer means for preferably transmitting light of a first polarization state relative to a second polarization state, said second layer means disposed at least one of (a) disposed beyond said first surface and said first layer means relative to said base layer and (b) disposed beyond said second surface and said first layer means and said second layer means further enabling reflection of at least part of the light having the second polarization state;

light redirecting means for operating on the light reflected by said second layer means and redirecting it back toward said second layer means; and

third layer means for converting at least part of the light of the second polarization state to light of the first polarization state.

58. The optical device as defined in claim 57 wherein said light redirecting means includes a reflective layer disposed underlying said second surface of said base layer and said second layer means overlying said base layer.

59. The optical device as defined in claim 58 wherein said third layer means is disposed between said reflective layer and said second layer means.

60. The optical device as defined in claim 59 wherein said third layer means is disposed above said first surface along with said second layer means.

61. The optical device as defined in claim 59 said third layer means is disposed below said second surface along with said reflective layer.

62. The optical device as defined in claim 57 wherein said second layer means comprises a plurality of layers of material having alternating high and low indices of refraction.

63. The optical device as defined in claim 62 wherein the indices of refraction n_H (high index) and n_L (low index) meet the requirement:

space="preserve" listing-type="equation">tanθ

.sub.H =n.sub.H /n.sub.L ;

space="preserve" listing-type="equation">tanθ

.sub.L =n.sub.L /n.sub.H

and

space="preserve" listing-type="equation">n.sub.H.sup.2 n.sub.L.sup.2 ≅

n.sub.H.sup.2 +n.sub.L.sup.2

64. The optical device as defined in claim 63 wherein the thickness of each layer of said plurality of layers is about one quarter the wavelength of light in said layers.

65. The optical device as defined in claim 63 wherein the thickness of each layer of said plurality of layers is at least twice the wavelength of light in said layers.

66. The optical device as defined in claim 57 wherein said third layer means is disposed between said second layer means and said light redirecting means.

67. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having a wedge-shaped cross-sectional area and having an optical index of refraction n₁, and a first and a second surface converging to define at least one angle of inclination φ

, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected therein decreases its angle relative to the normal to at least one of said first and second layer surfaces and achieves an angle of incidence less than a critical angle θ

_c relative to the normal;

layer means for preferably outputting light of a first polarization state compared to a second polarization state, said layer means including a first filter layer means for filtering the light to pass preferably said light of first polarization state and said layer means further including converting means for changing at least a part of said light of second polarization state to said light of first polarization state;

a liquid crystal display layer positioned to receive said light of first polarization state and output said light to the viewer; and

light diffuser means for diffusing light output from said layer means and said liquid crystal display layer to broaden the light in a narrow angular distribution in a plane thereby outputting light to a viewer over a range of viewing angle without distorting image quality.

68. The optical device as defined in claim 67 wherein said layer means comprises at least one polarization filter layer and at least one light polarization converting layer.

69. The optical device as defined in claim 67 wherein said light diffuser means comprises a parallel light diffuser.

70. The optical device as defined in claim 67 wherein said light diffuser means comprises a light redirecting layer having a prismatic faceted surface.

71. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having a wedge-shaped cross-sectional area and having an optical index of refraction n₁, and a first and a second surface converging to define at least one angle of inclination φ

, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected therein decreases its angle relative to the normal to at least one of said first and second layer surfaces and achieves an angle of incidence less than a critical angle θ

_c relative to the normal; and

first layer means including a layer having index n₂ less than n₁ disposed beyond said second surface relative to said base layer and for enabling light to enter said first layer means after output from said base layer when the light in said base layer achieves the angle of incidence less than the critical angle θ

_c characteristic of an interface between the base layer and said layer of index n₂ ; and

a liquid crystal display layer positioned to receive the light output from said first layer means and output said light to the viewer; and

light diffuser means for diffusing light output from said layer means and said liquid crystal display layer to broaden the light in a narrow angular distribution in a plane thereby outputting light to a viewer over a range of viewing angle without distorting image quality.

72. The optical device as defined in claim 71 further including at least one of a reflector layer, a light redirecting layer, and a transverse diffuser disposed nearer said base layer than said liquid crystal display layer.

73. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having a wedge-shaped cross-sectional area and having an optical index of refraction n₁, and a first and a second surface converging to define at least one angle of inclination φ

, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected therein decreases its angle relative to the normal to at least one of said first and second layer surfaces and achieves an angle of incidence less than a critical angle θ

_c relative to the normal;

first layer means including a layer having index n₂ less than n₁ disposed beyond said second surface relative to said base layer and for enabling light to enter said first layer means after output from said base layer when the light in said base layer achieves the angle of incidence less than the critical angle θ

_c characteristic of an interface between the base layer and said layer of index n₂ ;

second layer means for preferably outputting light of a first polarization state compared to a second polarization state, said second layer means being disposed beyond said second surface relative to said base layer and said second layer means further able to reflect at least part of the light having the second polarization state;

light redirecting means for controlling angular range of light to be output from said device; and

a liquid crystal display layer positioned to receive said light of said first polarization state for output to the viewer.

74. The optical device as defined in claim 73 wherein said second layer means comprises at least one of a polarization filter layer and a polarization converter layer.

75. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having a wedge-shaped cross-sectional area and having an optical index of refraction n₁, and a first and a second surface converging to define at least one angle of inclination φ

, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected therein decreases its angle relative to the normal to at least one of said first and second surfaces and achieves an angle of incidence less than a critical angle θ

_c relative to the normal;

layer means including an air gap at least one of disposed beyond said first surface and beyond said second surface relative to said base layer and having an optical index of refraction n₂ for allowing transmission of light received from said base layer;

converting layer means for changing light of one polarization state to another polarization state, said converting layer means disposed at least one of overlying and underlying said base layer; and

a liquid crystal display layer positioned to receive said light of said first polarization for output to the viewer.

76. The optical device as defined in claim 75 further including light diffuser means for diffusing light output from said layer means and said liquid crystal display layer to broaden the light in a selected narrow angular distribution.

77. The optical device as defined in claim 75 wherein said layer means comprises at least one polarization filter layer and at least one light polarization converting layer.

78. The optical device as defined in claim 75 wherein said light redirecting means comprises at least one of a light redirecting layer disposed above or below said base layer and (2) a light redirecting layer disposed adjacent said back surface.

79. An optical device for operating on light from a source and for selectively outputting light to a viewer, comprising:

a base layer having an optical index of refraction n₁, and a first surface and a second surface, said base layer further including a back surface spanning said first and second surfaces, and the light exiting said base layer when the light being reflected between the first and second surfaces progressively decreases its angle of incidence about 2φ

with each cycle of reflection relative to the normal to at least one of said first and second layer surfaces and leaves the base layer upon achieving an angle of incidence less than a critical angle θ

_c relative to the normal;

light redirecting means for controlling angular range of light in said device and to be output to the viewer from said device; and

layer means for preferably outputting light of a first polarization state compared to a second polarization state, said layer means including a filter layer means for filtering the light to pass preferably said light of first polarization state and said layer means further including converting means for changing said light of second polarization state to said light of first polarization state.

80. The optical device as defined in claim 79 further including a liquid crystal display layer positioned to receive said light of first polarization state and output said light to the viewer.

81. The optical device as defined in claim 80 further including light diffuser means for diffusing light output from said layer means and said liquid crystal display layer to broaden the light in a narrow angular distribution in at least one selected plane thereby outputting light to a viewer over a range of viewing angle without distorting image quality.

82. The optical device as defined in claim 79 wherein the range of angle of the output light has a redirected angle of output arising in part from the angle of output from the base layer upon decreasing its angle of incidence below θ

_c.