System and method for varying the reflectance or transmittance of light

• US 20050057701A1
• Filed: 08/13/2004
• Published: 03/17/2005
• Est. Priority Date: 02/15/2002
• Status: Active Grant

• Current Assignee: Eliav Korakh
• Original Assignee: ELOP Electro-Optics Industries Limited
• Inventors: Weiss, Victor
• Granted Patent: US 7,411,637 B2
• Time in Patent Office: Days
• US Class Current: 349/10
• CPC Class Codes: A61F 9/023 with variable transmission, e.g. photochromic for welding A61F9/067
• CPC Class Codes: A61F 9/067 with variable transmission
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/281 used for attenuating light intensity, e.g. comprising rotatable polarising elements
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00
• CPC Class Codes: G02F 1/0136 for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation G02F1/0353 takes precedence
• CPC Class Codes: G02F 1/1313 specially adapted for a particular application
• CPC Class Codes: G02F 1/13318 Circuits comprising a photodetector
• CPC Class Codes: G02F 1/133565 inside the LC elements, i.e. between the cell substrates
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 1/13475 in which at least one liquid crystal cell or layer is doped with a pleochroic dye, e.g. GH-LC cell G02F1/13476 takes precedence
• CPC Class Codes: G02F 1/13731 based on a field-induced phase transition G02F1/13781 takes precedence
• CPC Class Codes: G02F 2203/48 Variable attenuator
• CPC Class Codes: G02F 2413/01 Number of plates being 1

Abstract

Device for transmitting light at variable intensity, the device including a front variable polarizer, polarizing incoming light at a first selected polarization level, in a first direction and a rear variable polarizer, optically coupled with the front variable polarizer, polarizing light exiting the front variable polarizer at a second selected polarization level, in a second direction, wherein the first selected polarization level and the second selected polarization level are substantially zero, when no substantial electric power is applied respectively, to the front variable polarizer and the rear variable polarizer.

Claims

1. Device for transmitting light at variable intensity, the device comprising:

a front variable polarizer, polarizing incoming light at a first selected polarization level in a first direction; and

a rear variable polarizer, optically coupled with said front variable polarizer, polarizing light exiting said front variable polarizer at a second selected polarization level, in a second direction,

wherein said first selected polarization level and said second selected polarization level are substantially zero, when no substantial electric power is applied respectively, to said front variable polarizer and said rear variable polarizer.

2. The device according to claim 1, wherein said first selected polarization level is selected by controlling the electric field at said front variable polarizer.

3. The device according to claim 1, wherein said second selected polarization level is selected by controlling the electric field at said rear variable polarizer.

4. The device according to claim 1, wherein each of said first selected polarization level and said second selected polarization level is selected by setting said front variable polarizer and said rear variable polarizer, respectively, to one of a plurality of states.

5. The device according to claim 44, wherein said states comprise at least one homeotropic state.

6. The device according to claim 4, wherein said states comprise at least one planar state.

8. The device according to claim 1, wherein at least one of said front variable polarizer and said rear variable polarizer is a multi-stable liquid crystal device.

9. The device according to claim 1, wherein each of said front variable polarizer rear variable polarizer is constructed by applying a mixed homeotropic and planar surface alignment procedure thereto.

10. The device according to claim 1, wherein each of said front variable polarizer and said rear variable polarizer comprises a light affecting substance, said light affecting substance comprises:

an optically active substance; and

a plurality of anisotropic light absorbing particles

wherein said light affecting substance polarizes said incoming light according to the direction of said anisotropic light absorbing particles.

11. The device according to claim 10, wherein the dielectric anisotropy of said optically active substance is selected from the list consisting of:

positive; and

negative.

12. The device according to claim 10, wherein the optical anisotropy of said anisotropic light absorbing particles is selected from the list consisting of:

positive; and

negative.

13. The device according to claim 10, wherein said optically active substance is selected from the list consisting of:

liquid crystal;

liquid crystal polymer;

bireferingent crystal;

bireferingent polymer; and

bireferingent plastic.

14. The device according to claim 10, wherein said anisotropic light absorbing particles are selected from the list consisting of:

dichroic dye molecules;

dichroic microcrystals; and

pleochroic dye stuff.

15. The device according to claim 10, wherein said anisotropic light absorbing particles are distributed within said optically active substance, in a phrase distribution selected from the list consisting of:

dispersed; and

homogeneous.

16. The device according to claim 15, wherein each of said dispersed phase distribution and said homogeneous phase distribution, is in a form selected from the list consisting of:

mixture; and

chemical compound.

17. The device according to claim 15, wherein said homogeneous phase distribution is derived from liquid crystal materials and phases selected from the list consisting of:

nematic;

twisted nematic,

supertwisted nematic;

cholesteric,

smectic;

multi-stable; and

a combination of the above.

18. The device according to claim 15, wherein said dispersed phase distribution is derived from liquid crystal materials and phases selected from the list consisting of:

Guest-Host Polymer Dispersed Liquid Crystal;

Dichroic Polymer Dispersed Liquid Crystal;

Polymer Stabilized Cholesteric Texture Liquid Crystal;

Surface Stabilized Cholesteric Texture Liquid Crystal; and

Nematic Curved Aligned Polymeric Liquid Crystal.

19. The device according to claim 15, wherein said dispersed phase distribution has a non-spherical anisotropic geometry selected from the list consisting of:

elliptical;

elongated;

sheared; and

a combination of the above.

20. The device according to claim 15, wherein the refractive index anisotropy of said dispersed phase distribution, between the ordinary index of said dispersed phase distribution and the extraordinary index of said dispersed phase distribution, is sufficiently small, that each of said front variable polarizer and said rear variable polarizer polarizes incident light without substantially scattering said incident light.

21. The device according to claim 1, wherein the plane defined by said device is selected from the list consisting of:

flat;

concave;

convex; and

curved.

22. The device according to claim 1, wherein the type of said device is selected from the list consisting of:

rigid; and

flexible.

23. The device according to claim 1, wherein said first direction is substantially perpendicular to said second direction.

24. The device according to claim 1, wherein said first selected polarization level and said second selected polarization level are selected by controlling the electric field at said front variable polarizer and at said rear variable polarizer, respectively.

25. The device according to claim 1, wherein setting said front variable polarizer and said rear variable polarizer to said first polarization level and said second polarization level, respectively, determines the contrast and brightness of an image produced by said device.

26. The device according to claim 1, further comprising a controller, controlling at least one of said variable polarizer and said rear variable polarizer.

27. The device according to claim 26, wherein said controller is coupled with said front variable polarizer,

wherein said front variable polarizer is divided into a plurality of sections, and

wherein said controller sets each of said sections to a respective polarization level.

28. The device according to claim 26, wherein said controller is coupled with said rear variable polarizer,

wherein said rear variable polarizer is divided into a plurality of rear end sections, and

wherein said controller sets each of said rear end sections to a respective polarization level.

29. The device according to claim 28, wherein said controller is further coupled with said front variable polarizer,

wherein said front variable polarizer is divided into a plurality of front end sections, said front end sections being compatible with said rear end sections, and

wherein said controller sets each of said front end sections to another respective polarization level.

30. The device according to claim 26, further comprising at least one light detector, coupled with said controller, wherein said at least one light detector provides at least one light-intensity value.

31. The device according to claim 30, wherein said at least one light value is produced according to a meeting scheme selected from the list consisting of:

spot;

center-weighted;

multi-zone; and

ambient.

32. The device according to claim 30, wherein said controller sets said front variable polarizer and said rear variable polarizer to said first selected polarization level and to said second selected polarization level, respectively, according to said at least one light-intensity value.

33. The device according to claim 30, wherein at least one of said at least one light detector is a active-region light detector, respective of an active region of interest.

34. The device according to claim 30, wherein at least one of said at least one light detector is a passive-region light detector, respective of a passive region of interest.

35. The device according to claim 30, wherein said controller, at least one of said at least one light detector, said front variable polarizer and said rear variable polarizer are coupled together in a control system loop.

36. The device according to claim 1, wherein said front variable polarizer comprises:

a first protective layer;

a second protective layer;

a first pair of multi-pronged electric conductors located between said first protective layer and said second protective layer, a first set of prongs of said first pair lying along a first multi-prong direction, said first set of prongs being intermingled; and

a light affecting substance said light affecting substance comprises;

an optically active substance; and

a plurality of anisotropic light absorbing particles being substantially aligned with the molecules of said optically active substance,

wherein said front variable polarizer comprises,

a third protective layer;

a fourth protective layer;

a second pair of multi-pronged electric conductors located between said third protective layer and said fourth protective layer, a second set of prongs of said second pair lying along a second multi-prong direction, said first multi-prong direction being rotated by substantially ninety degrees relative to said second multi-prong direction, said second set of prongs being intermingled, and

another light affecting substance similar to said light affecting substance,

wherein said optically active substance is aligned along said first direction, when said electric power is applied to said first pair, thereby said anisotropic light absorbing particles polarizing said incoming light at a first powered condition polarization level, and

wherein said other optically active substance is aligned along said second direction, when said electric power is applied to said second pair, thereby said anisotropic light absorbing particles polarizing said incoming light at a first powered condition polarization level, and

37. The device according to claim 36, wherein said front variable polarizer further comprises a first alignment layer located between said first protective layer and said second protective layer, said first pair being located between said first protective layer and said first alignment layer, said first alignment layer affecting a molecular direction of said molecules, such that when substantially no electric power is applied to said first pair, said anisotropic light absorbing particles polarize said incoming light at an un-powered condition polarization level, and

wherein said rear variable polarizer further comprises a second alignment layer located between said third protective layer and said fourth protective layer, said second pair being located between said third protective layer and said second alignment layer, said second alignment layer affecting said molecular direction, such that when substantially no electric power is applied to said second pair, said anisotropic light absorbing particles polarize said incoming light at said un-powered condition polarization level.

38. The device according to claim 37, wherein each of said first alignment layer and second alignment layer is selected from the list consisting of:

homeotropic;

planar;

inorganic dielectric; and

organic dielectric.

39. The device according to claim 36, wherein said front variable polarizer further comprises:

a first insulating layer located between said first protective layer and said second protective layer, said first pair being located between said first protective layer and said first insulating layer; and

a first electrically conducting layer located between said first insulating layer and said second protective layer,

wherein said rear variable polarizer further comprises;

a second insulating layer located between said third protective layer and said forth protective layer, said second pair being located between said third protective layer and said second insulating layer; and

a second electrically conducting layer located between said second insulating layer and said fourth protective layer,

wherein said optically active substance is aligned along said first direction, when said electric power is applied to said first pair and to said first electrically conducting layer, and

wherein said optically active substance is aligned along said second direction, when said electric power is applied to said second pair and to said second electrically conducting layer.

40. The device according to claim 39, wherein said front variable polarizer further comprises:

a third insulating layer located between said first insulating layer and said first pair; and

a first alignment layer located between said first insulating layer and said third insulating layer, said first alignment layer affecting a molecular direction of said molecules, such that when substantially no electric power is applied to said first pair and to said first electrically conducting layer, said anisotropic light absorbing particles polarize said incoming light at an un-powered condition polarization level, and

wherein said rear variable polarizer further comprises,

a fourth insulating layer located between said second insulating layer and said second pair; and

a second alignment layer located between said second insulating layer and said fourth insulating layer, said second alignment layer affecting said molecular direction, such that when substantially no electric power is applied to said second pair and to said second electrically conducting layer, said anisotropic light absorbing particles polarize said incoming light at said un-powered condition polarization level.

41. The variable polarizer according to claim 39, wherein said first pair, said second pair, said first electrically conducting layer, and said second electrically conducting layer are coupled with a power source and with a controller,

wherein said controller controls said electric power across said first pair and said first electrically conducting layer on one hand and said second pair and said second electrically conducting layer on the other hand, and

wherein said anisotropic light absorbing particles polarize said incoming light at said first powered condition polarization level, in a first region of said front variable polarizer corresponding to said first pair and to said first electrically conducting layer, and said other anisotropic light absorbing particles polarize said incoming light at said second powered condition polarization level, in a second region of said rear variable polarizer corresponding to said second pair and to said second electrically conducting layer.

42. The device according to claim 39, wherein each of said first electrically conducting layer and said second electrically conducting layer is made of substantially thin, transparent and electrically conductive material, selected from the list consisting of:

conductive polymer;

glass coated by indium-tin-oxide;

tin-oxide; and

metal.

43. The device according to claim 36, wherein each of said first protective layer, said second protective layer, said third protective layer, and said fourth protective layer is made of a substantially transparent material selected from the list consisting of:

glass;

crystal;

polymer; and

plastic.

44. The device according to claim 36, wherein each of said first pair and said second pair is made of a substantially thin transparent and electrically conductive material, selected from the list of:

conductive polymer;

glass coated by indium-tin-oxide;

tin-oxide; and

metal.

45. The device according to claim 36, wherein said first pair and said second pair are coupled with a power source and with a controller,

wherein said controller controls said electric power across said first set of prongs and across said second set of prongs, and

wherein said anisotropic light absorbing particles polarize said incoming light at said first powered condition polarization level, in a first region of said front variable polarizer corresponding to said first pair, and at said second powered condition polarization level, in a second region of said rear variable polarizer corresponding to said second pair, when said electric power is applied across said first of prongs and across said second set of prongs.

46. Devise for transmitting light at variable intensity, the device comprising:

a front variable polarizer, polarizing incoming light at a first selected polarization level, in a first direction;

a rear variable polarizer, optically coupled with said front variable polarizer; and

at least one controllable optical phase shifter, located between said front variable polarizer and said rear variable polarizer, said at least one controllable optical phase shifter shifting the relative phase between linearly polarized components of light which exits said front variable polarizer, by a selected phase shift,

wherein said rear variable polarizer polarizes light received from said at least one controllable optical phase shifter, at a second selected polarization level, in a second direction.

7. The device according to claim 64, wherein said states comprise at least one state wherein at least one of said first selected polarization level and said second selected polarization level is substantially zero.

47. The device according to claim 46, wherein said selected phase shift is substantially zero.

48. The device according to claim 46, wherein said controller optical phase shifter comprises at least a material selected from the list consisting of:

glass;

organic crystal;

inorganic crystal;

organic polymer;

inorganic polymer; and

liquid crystal.

49. The device according to claim 46, wherein said controllable optical phase shifter is coated with at least a substantially thin film.

50. The device according to claim 49, wherein said substantially think film is located between two substantially thin layers of said material.

51. The device according to claim 46, wherein said at least one controllable optical phase shifter is selected from the list consisting of:

multi-stable optical phase shifter; and

switchable optical phase shifter.

52. The device according to claim 51, wherein said multi-stable optical phase shifter is a bi-stable liquid crystal selected from the list consisting of:

twisted nematic liquid crystal;

polymer stabilized liquid crystal; and

surface stabilized liquid crystal.

53. The device according to claim 46, wherein said at least one controllable optical phase shifter has substantially no phase shifting effect on light, when said controllable optical phase shifter is in the on state, and

wherein said at least one controllable optical phase shifter shifts the relative phase between two linearly polarized components of light, when said controllable optical phase shifter is in the off state.

54. The device according to claim 46 wherein said first direction is substantially perpendicular to said second direction.

55. The device according to claims 46, wherein said first selected polarization level, said second selected polarization level and said selected phase shift, are selected by controlling the electric field at said front variable polarizer, at said rear variable polarizer and sat said at least one controllable optical phase shifter, respectively.

56. The device according to claim 46, further comprising a controller, controlling at least one of said front variable polarizer, said rear variable polarizer and said at least one controllable optical phase shifter.

57. The device according to claim 56, further comprising at least one light detector, coupled with said controller, wherein said light detector provides at least one light-intensity value.

58. The device according to claim 57, wherein said controller, sets at least one of said front variable polarizer, said rear variable polarizer and said at least one controllable optical phase shifter, to said first selected polarization level, said second selected polarization level and to said selected phase shift, respectively, according to said at least one light-intensity value.

59. The device according to claim 58, wherein at least one of said at least one light detector is an active region light detector, respective of an active region of interest.

60. The device according to claim 58, wherein at least one of said at least one light detector is a passive-region light detector, respective of a passive region of interest.

61. The device according to claim 58, wherein said controller, at least one of said at least one light detector said front variable polarizer, said at least one controllable optical phase shifter and said rear variable polarizer are coupled together in a control system loop.

62. The device according to claim 46, wherein said controller is coupled with said front variable polarizer,

wherein said front variable polarizer is divided into a plurality of front end sections, and

wherein said controller sets each said front end sections to a respective polarization level.

63. The device according to claim 62, wherein said controller is further coupled with said front variable polarizer,

wherein said front variable polarizer is divided into a plurality of front end sections, said front end sections being compatible with said rear end sections, and

wherein said controller sets each of said front end sections to another respective polarization level.

64. The device according to claim 46, wherein said at least one controllable optical phase shifter operates as a substantially transparent medium, when substantial electric power is available, and

wherein said at least one controllable optical phase shifter shifts the relative phase between two linearly polarized components of light, when substantial electric power is not available.

65. The device according to claim 64, wherein said at least one controllable optical phase shifter shifts said relative phase by substantially π

radians, when substantial electric power is not available.

66. Method for transmitting light at variable intensity, the method comprising the procedures of:

polarizing light, at a first selected polarization level, by a front variable polarizer;

polarizing said light, at a second selected polarization level, by a rear variable polarizer,

wherein said first selected polarization level and said second polarization levels are substantially zero, when no substantial power is available.

67. The device according to claim 66, further comprising a preliminary procedure of controlling the electric field at at least one of said front variable polarizer and said rear variable polarizer, thereby selecting at least one of said first selected polarization level and said second selected polarization level, respectively.

68. The method according to claim 67, wherein at least one of said first selected polarization level and said second selected polarization level is selected according to at least one light-intensity value.

69. The method according to claim 66, further comprising a preliminary procedure of detecting the intensity of light, thereby providing at least one light-intensity value.

70. The method according to claim 69, wherein said procedure of detecting comprises the sub-procedure of detecting the intensity of active-region light, thereby providing at least one active-region light-intensity value.

71. The method according to claim 69, wherein said procedure of detecting comprises the sub-procedure of detecting the intensity of passive-region light, thereby providing at least one passive-region light-intensity value.

72. Method for transmitting light at variable intensity, the method comprising the procedures of:

polarizing light, at a first selected polarization level, by a front variable polarizer;

shifting the relative phase between two linearly polarized components of said light, by a selected phase shift; and

polarizing said light, at a second selected polarization level, by a rear variable polarizer.

73. The method according to claim 72, wherein said selected phase shift is substantially equal to π

radians, when substantial electric power is not available.

74. The method according to claim 72, wherein said selected phase shift substantially equal to zero, when substantial electric power is available.

75. The method according to claim 72, further comprising a preliminary procedure of controlling the electric field at at least one of said front variable polarizer, said rear variable polarizer and a controllable optical phase shifter, thereby selecting at least one of said first selected polarization level, said second selected polarization level, and said selected phase shift, respectively.

76. The method according to claim 75, wherein at least one of said first selected polarization level and said second selected polarization level, is selected according to at least one light-intensity value.

77. The method according to claim 72, further comprising a preliminary procedure of detecting the intensity of light, thereby providing at least one light-intensity value.

78. The method according to claim 77, wherein said procedure of detecting comprises the sub-procedure of detecting the intensity of active-region light, thereby providing at least one active-region light intensity value.

79. The method according to claim 77, wherein at said procedure of detecting comprises the sub-protective of detecting the intensity of passive-region light, thereby providing at least one passive-region light-intensity value.

80. Apparatus, for viewing an image at variable intensity, the apparatus comprising:

an optical assembly; and

a variable transmitter, said variable transmitter including;

a front variable polarizer; and

a rear variable polarizer, optically coupled with said front variable polarizer,

wherein said front variable polarizer applies substantially no polarization to an incoming light and transmits said incoming light as an outgoing light, when a first change in an electric field is applied to said front variable polarizer,

wherein said front variable polarizer polarizes said incoming light in a first direction, thereby producing a polarized incoming light, when a second change in said electric field is applied to said front variable polarize,

wherein said rear variable polarizer applies substantially no polarization to said outgoing light, when said first change is applied to said rear variable polarizer, and

wherein said rear variable polarizer said polarized incoming light in a second direction, when said second change is applied to said rear variable polarizer.

81. The apparatus according to claim 80, wherein said optical assembly is selected from the list consisting of:

spectacles;

helmet visor;

welding visor;

periscope;

telescope;

microscope;

binoculars;

ground vehicle window;

aircraft window;

spacecraft window;

marine vehicle window;

grazing;

greenhouse window.

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