Uniform illumination system

• US 7,400,439 B2
• Filed: 02/21/2006
• Issued: 07/15/2008
• Est. Priority Date: 12/14/2001
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Digital Optics International Corporation
• Inventors: Holman, Robert L.
• Primary Examiner(s): Ben; Loha
• Application Number:
  US11/358,828
• Publication Number:
  US 20060152931A1
• Time in Patent Office: 875 Days
• Field of Search: 359/298, 359/618, 359/619, 359/621, 359/631, 359/634, 359/457, 359/599, 362/19, 362/27, 362/30, 362/31, 362/33, 362/242, 362/243, 362/245, 362/328, 362/331, 362/318, 362/297, 362/555, 362559-561, 362/800, 353/20, 353/31, 353/33, 353/34, 353/94, 349/62, 349 64- 66, 349/102, 349/112
• US Class Current: 359/298
• CPC Class Codes: F21S 41/12 characterised by the type of emitted light
• CPC Class Codes: F21S 41/141 Light emitting diodes [LED]
• CPC Class Codes: F21S 8/08 with a standard F21S6/00 takes precedence
• CPC Class Codes: F21W 2102/00 Exterior vehicle lighting devices for illuminating purposes
• CPC Class Codes: F21W 2131/10 Outdoor lighting
• CPC Class Codes: F21W 2131/406 for theatres, stages or film studios
• CPC Class Codes: F21Y 2105/10 comprising a two-dimensional array of point-like light-generating elements
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0066 in the form of an LED array
• CPC Class Codes: G02B 27/0994 Fibers, light pipes optical fibers per se G02B6/02
• CPC Class Codes: G02B 27/1026 for use with reflective spatial light modulators
• CPC Class Codes: G02B 27/1033 having a single light modulator for all colour channels
• CPC Class Codes: G02B 27/1046 for use with transmissive spatial light modulators
• CPC Class Codes: G02B 27/1053 having a single light modulator for all colour channels
• CPC Class Codes: G02B 27/1066 for enhancing image performance, like resolution, pixel numbers, dual magnifications or dynamic range, by tiling, slicing or overlapping fields of view
• CPC Class Codes: G02B 27/1073 characterized by manufacturing or alignment methods
• CPC Class Codes: G02B 27/123 The splitting element being a lens or a system of lenses, including arrays and surfaces with refractive power
• CPC Class Codes: G02B 27/126 The splitting element being a prism or prismatic array, including systems based on total internal reflection
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 27/147 : using averaging effects by spatially variable reflectivity on a microscopic level, e.g. polka dots, chequered or discontinuous patterns, or rapidly moving surfaces G02B27/1086 takes precedence
• CPC Class Codes: G02B 27/149 : using crossed beamsplitting surfaces, e.g. cross-dichroic cubes or X-cubes
• CPC Class Codes: G02B 27/283 : used for beam splitting or combining
• CPC Class Codes: G02B 5/045 : Prism arrays
• CPC Class Codes: G02B 6/0028 : Light guide, e.g. taper
• CPC Class Codes: G02B 6/0031 : Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0043 : provided on the surface of the light guide
• CPC Class Codes: G02B 6/0053 : Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02F 1/133603 : with LEDs
• CPC Class Codes: G02F 1/133604 : with lamps
• CPC Class Codes: G02F 1/133605 : including specially adapted reflectors
• CPC Class Codes: H01L 25/0753 : the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 : Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H04N 9/3105 : for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/315 : Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20

Abstract

A compact and efficient optical illumination system featuring planar multi-layered LED light source arrays concentrating their polarized or un-polarized output within a limited angular range. The optical system manipulates light emitted by a planar light emitters such as electrically-interconnected LED chips. Each light emitting region in the array is surrounded by reflecting sidewalls whose output is processed by elevated prismatic films, polarization converting films, or both. The optical interaction between light emitters, reflecting sidewalls, and the elevated prismatic films create overlapping virtual images between emitting regions that contribute to the greater optical uniformity. Practical illumination applications of such uniform light source arrays include compact LCD or DMD video image projectors, as well as general lighting, automotive lighting, and LCD backlighting.

Claims

1. An illuminating system comprising:

one or more light emitting diodes (“

LEDs”

), having an input aperture;

a mounting plate disposed behind said one or more LED, the mounting plate supporting and in electrical communication with the one or more LEDs;

a set of substantially identical four-sided reflecting elements associated with each one of the one or more LEDs, arranged to radiate substantially all emitted light into the input aperture of each of the reflecting elements, each of the reflecting elements having a metallic surface substantially bounding a dielectric medium, the input aperture having a first width, and defining an input aperture plane, and an output aperture having a second width, the input aperture of the reflecting element in communication with and sized to match or approximate the output aperture of each corresponding LED, said output aperture of each reflecting element being larger in area than said input aperture, such that at least two opposing sidewalls of said four-sided reflecting elements mathematically curved between said input and output apertures according to the Sine Law so that the distance between said sidewalls at said output aperture (the second width) times the Sine of a chosen output illumination angle corrected for refractive index of said reflecting elements dielectric medium disposed within the reflecting elements, substantially equals the distance between said sidewalls at said input aperture (the first width) with the focal point of one such sidewall surface shape located at the line of intersection existent between the reflecting element'"'"'s input aperture plane and the opposing sidewall surface shape, and the focal point of the opposing sidewall surface shape located at the line of intersection existent between the reflecting element'"'"'s input aperture plane and said first sidewall surface shape, such that at least two opposing sidewalls are mathematically curved between said input and output apertures in such way that said opposing sidewalls have equivalent conicoidal surface shapes, the common conicoidal vertex located on an optical axis perpendicular to said input aperture plane, said vertex being substantially centered within said reflecting element input aperture, the common focal point of said conicoidal surface shapes being located substantially at a height H above the input aperture plane with at least one of a first light redirecting layer and second light redirecting layer, which is positioned between the first light redirecting layer and the input aperture plane, positioned substantially at a height H/2 parallel to and above said input aperture plane;

the first light redirecting layer for receiving light of a first polarization state and transmitting light of a second polarization state orthogonal to said first polarization state, said first light redirecting layer being substantially perpendicular to the optical axis and in optical communication with the one or more LEDs and located beyond said output aperture substantially mid-way between said input aperture plane and said common focal point;

the second light redirecting layer substantially parallel to said first light redirecting layer located between said input aperture plane and said output aperture plane and arranged for the purpose of scattering light such that a first fraction of the incoming light is transmitted in an angular direction, a second fraction of the incoming light is reflected in a different angular direction, and a third fraction of the incoming light is transmitted with substantially no change to its incoming direction; and

a third light redirecting layer disposed above said first and second light redirecting layers for receiving light from the second light redirecting layer and which is polarization neutral.

2. The illuminating system as defined in claim 1 wherein the one or more LEDs comprise two or more LEDs arranged in an array.

3. The illuminating system as defined in claim 2 wherein the two or more LEDs are arranged in a planar array.

4. The illuminating system as defined in claim 3 wherein the first light redirecting layer is substantially parallel to said planar array.

5. The illuminating system as defined in claim 3 wherein the two or more LEDs are not parallel to each other with respect to the plane of the planar array.

6. The illuminating system as defined in claim 5 wherein the first light redirecting layer is in itself sub-divided as an array of the same size, spacing and order as the two or more LEDs, and the optical axis of each array element is substantially parallel to the optical axis of each element in said planar array.

7. The illuminating system as defined in claim 2 wherein the two or more LEDs are parallel to each other.

8. The illumination as defined in claim 2 wherein the first width is substantially equal to the width W of a cavity containing an LED, and the second width is substantially equal to center-to-center spacing, W+W′

, of the two or more LEDs where W′

is substantially equal to the spacing between two cavities each containing an LED.

9. The illuminating system as defined in claim 1 wherein the first light redirecting layer comprises a layer selected from the group consisting of at least one of a quarter-wave phase retardation film, a reflective polarizer and a combination thereof.

10. The illuminating system as defined in claim 9 wherein said second light redirecting layer contains light scattering features selected from the group consisting of physical deposition, geometric patterns of squares, circles, dots, lines, bars, films, related deposition geometries, and combinations thereof, whose optical result is to scatter, reflect, refract, diffract, or otherwise change direction of some fraction of incoming light.

11. The illuminating system as defined in claim 1 wherein the third light redirecting layer comprises a layer selected from the group consisting of at least one of a fresnel lens, an array of micro-lenses, an array of prism grooves, a light guiding plate containing a distribution of light extracting elements whose redirecting nature does not cause any changes in the polarization of light passing through said third redirecting layer, and combinations thereof.

12. The illuminating system as defined in claim 1 wherein said one or more LEDs comprise flip chip style LEDS and substantially fit within said reflecting element input apertures.

13. The illuminating system as defined in claim 1 wherein said one or more LEDs are contained within a package or packages each having a region of fluorescent containing material that receives light from said one or more LEDs, the output surface of said fluorescent containing material substantially fitting within, through or lying immediately below said reflective element input apertures.

14. The illuminating system as defined in claim 1 wherein said reflecting elements are filled with a medium consisting of either air or a clear, optically transparent dielectric gel or polymer material that makes optical contact with said input apertures and said one or more LEDs.

15. The illuminating system as defined in claim 1 wherein said first light redirecting layer includes a quarter-wave phase retardation film and a polarizer for absorbing or reflecting light of a first polarization state and transmitting light of a second polarization state orthogonal to said first polarization state, the polar axis of said quarter-wave phase retardation film oriented at substantially 45-degrees to the polar axis of said polarizer for absorbing or reflecting light of a first polarization state and transmitting light of a second polarization state orthogonal to said first polarization state.

16. The illuminating system as defined in claim 1 wherein said set of substantially identical four-sided reflecting elements comprise thin multilayered metallic films of high reflectivity silver or aluminum in combination with thin dielectric multilayers made of silica, sapphire, titanium dioxide, magnesium fluoride, polymer, or some equivalent combination of the same or similar dielectric layers.

17. The illuminating system as defined in claim 1 wherein said set of substantially identical four-sided reflecting elements are fabricated simultaneously from mandrels whose mirror smooth surface has been made to replicate the air space within the array of said set of substantially identical four-sided reflecting elements a method selected from the group of injection molding, compression molding, compression-injection molding, embossing, casting and curing, powder coating, tape casting or sintering of polymeric materials, metallic materials, glass materials, ceramic materials, or some combinations of the same.

18. The illuminating system as defined in claim 1 wherein said set of substantially identical four-sided reflecting elements are fabricated from a forming mandrel made to replicate the air space within the array of said set of substantially identical four-sided micro reflecting elements by a method selected from the group consisting of electroforming, electroplating, and

chemical vapor deposition of a nickel based precursor, so as to yield a substantially nickel replica of the forming mandrel.

19. The illuminating system as defined in claim 1 wherein said second light redirecting layer is made to scatter, diffuse, or otherwise misdirect a portion of the transmitted light reflecting from said mathematically curved sidewalls of said reflecting elements within said set of substantially identical four-sided reflecting elements.

20. The illuminating system as defined in claim 1 wherein said third light redirecting layer is a light guide plate whose light extracting features are a spatial distribution selected from the group consisting of one or more of prism facets, prism grooves, prism elements and combinations thereof whose redirecting nature operates without change in the state of light polarization.

21. The illuminating system as defined in claim 20 wherein said light guide plate is made from a clear and transparent glass of polymeric material that is free of mechanical strain and optical birefringence.

22. The illuminating system as defined in claim 21 wherein said light guide plate is made of an ultra-high purity form of poly methyl methacrelate (aka, PMMA or acrylic).

23. The illuminating system as defined in claim 21 wherein said light guide plate is made of a sheet of glass.

24. The illuminating system as defined in claim 23 wherein said sheet of glass is of the type used in the construction of commercial display devices.

25. The illuminating system as defined in claim 1, wherein the one or more LEDs are selected from the group consisting of semiconductor type light organic-type light emitting diodes, “

OLEDs”

, LED/OLED excited fluorescent materials, and combinations thereof.

26. An illuminating system comprising:

one or more light emitting diodes (LED);

a four-sided rectangular reflecting element whose input aperture has an aperture area that bounds said one or more LEDs and whose aperture shape generally follows the boundary of said one or more LEDs, and having an output aperture elevated above said input aperture at a height H established by the physical position of two opposing pairs of optically reflecting sidewalls having a mathematical curvatures substantially satisfying the geometric Sine Law expression d_i×

Sin θ

_i=d_j×

Sin θ

_j for each opposing pair of reflecting side walls, said output aperture height H being determined by the interrelated geometric Sine law expression H=[(d_i+dj)/2]/Tan θ

_j, d_i being the distance between said opposing pair of reflecting sidewalls measured at their input aperture, θ

_i being the distance between said opposing pair of reflecting sidewalls measured at their output aperture, θ

_i being half the full emission angle of said one or more LEDs at said input aperture of each said opposing pair of reflecting sidewalls, θ

_j being half the maximum emission angle occurring at said output aperture of each said opposing pair of reflecting sidewalls, each said maximum emission angle θ

_j combining to form the periphery of a substantially rectangular output beam; and

a light redirecting layer disposed in optical communication with said four-sided rectangular reflecting element for receiving light from said reflecting element and change the direction of at least a portion of the light.

27. The illuminating system as defined in claim 26 wherein said four-sided rectangular reflecting element is filled with air as its internal dielectric medium.

28. The illuminating system as defined in claim 27 wherein the output beam is substantially square in cross-section, making a substantially square illumination pattern on a flat surface distant from said illumination system and perpendicular to said illumination system'"'"'s optical axis.

29. The illuminating system as defined in claim 26 wherein said four-sided square or rectangular reflecting element is filled with a dielectric medium selected from the group consisting of a clear transparent polymeric material, clear and transparent glass, a clear and transparent dielectric gel, a clear and transparent glass-polymer composite, a clear and transparent dielectric resin, other optically transparent material that makes optical contact with said one or more LEDs and otherwise substantially fills the volume between said optically reflecting sidewalls, and combinations thereof.

30. The illuminating system, as defined in claim 29 wherein said optically reflecting sidewalls comprise one or more of layers of material selected from the group consisting of a silver film, an aluminum film, a gold film, a sapphire film, a silicon dioxide film, a polymer film, a magnesium dioxide film, a titanium dioxide film and combinations thereof.

31. The illuminating system, as defined in claim 29 wherein said optically reflecting sidewalls reflect light by total internal reflection.

32. The illuminating system as defined in claim 26, comprising a plurality of four-sided rectangular reflecting elements grouped in a linear array wherein one edge of said output apertures of each said four-sided rectangular reflecting elements are either substantially common or separated by an equal flat reflecting space connecting said output apertures.

33. The illuminating system as defined in claim 31 wherein each of said four-sided reflecting elements is fabricated simultaneously from a common mandrel having mirror smooth surface finish made to replicate substantially the exact interior volumes between each set of said input and said output apertures defined by each adjacent set of said opposing pairs of reflecting sidewalls by process selected from the group consisting of injection molding, compression molding, compression-injection molding, embossing, casting, powder coating or tape casting of polymeric materials, metallic materials, glass materials, ceramic materials, and combinations thereof.

34. The illuminating system as defined in claim 26 comprising a plurality of four-sided rectangular reflecting elements grouped in a two-dimensional array wherein all four edges of said output apertures of each said four-sided rectangular reflecting element are either substantially common with equivalent edges of said output apertures of surrounding four-sided rectangular reflecting elements, or there is an equal plane reflecting space connecting said output apertures between every pair of said four-sided rectangular reflecting elements.

35. The illuminating system as defined in claim 34 wherein the optical axis of array elements in said two-dimensional array are directed towards a target aperture or portions thereof to be illuminated by said two-dimensional array.

36. The illuminating system as defined in claim 34 wherein each of said four-sided reflecting elements is fabricated simultaneously from a common mandrel having mirror smooth surface finish made to replicate substantially the exact interior volumes between said input and said output apertures defined by each adjacent set of said opposing pairs of reflecting sidewalls by one of injection molding, compression molding, compression-injection molding, embossing, casting, powder coating or tape casting of polymeric materials, metallic materials, glass materials, ceramic materials, and combinations thereof.

37. The illuminating system as defined in claim 26 wherein said four-sided reflecting element is fabricated from a mandrel having mirror smooth surface finish made to replicate substantially the exact interior volume between said input and said output apertures defined by said opposing pairs of reflecting sidewalls by a process selected from the group consisting of injection molding, compression molding, compression-injection molding, embossing, casting, powder coating, tape casting or sintering of polymeric materials, metallic materials, glass materials, ceramic materials, and combinations thereof.

38. The illuminating system as defined in claim 26 further comprising three four-sided rectangular reflecting elements wherein said output apertures of said three four-sided rectangular reflecting elements are arranged on three of the four available surfaces of a dichroic x-cube, each of said reflecting elements attached to single-colored light emitting diode chips or emitters, one set being red, one set being blue, and one set being green, the output of said dichroic x-cube being a composite multi-colored beam of light having substantially the same beam shape and bean angle as output by any one of said rectangular reflecting elements.

39. The illuminating system as defined in claim 26 wherein said rectangular output beam is deliberately directed at a pre-established distance towards at least one rectangular surface so as to create rectangular field of illumination on said at least one surface, said at least one surface selected from the group consisting of a table top, a portion of a floor, a portion of a walkway, a portion of a sidewall on a building or a structure, the entry way area of a building or structure, a wall-mounted painting, a square or rectangular advertising billboard or sign, a roadway section, portion or intersection, a sidewalk, one or more photographic subjects within a square or rectangular illumination field, printed pages as of those of a person reading said printed pages, the square or rectangular personal seating area of a train, automobile, bus, or plane, an object or objects arranged on a square or rectangular display surface to be illuminated, a theatrical performance stage, and combinations thereof.

40. The illuminating system as defined in claim 39 wherein said rectangular output beam is deliberately directed at a pre-established distance towards at least one rectangular surface so as to create at least one rectangular field of illumination on said at least one surface.

41. The illuminating system as defined in claim 40, wherein said at least one surface is chosen from a group consisting of a table top, a portion of a floor, a portion of a walkway, a portion of a sidewall on a building or a structure, the entry way area of a building or structure, a wall-mounted painting, a rectangular advertising billboard or sign, a roadway section, portion or intersection, a sidewalk, one or more photographic subjects within a rectangular illumination field, printed pages as of those of a person reading said printed pages, the rectangular personal seating area of a train, automobile, bus, plane, an object or objects arranged on a rectangular display surface to be illuminated, a theatrical performance stage, and combinations thereof.

42. The illuminating system as defined in claim 26 wherein all four optically reflecting sidewalls are identical forming a square input aperture and a square output aperture.

43. The illuminating system as defined in claim 26, wherein each set of two opposing optically reflecting sidewalls are not identical and so form a rectangular input aperture and a rectangular output aperture.

44. The illuminating system as defined in claim 26 wherein the first light redirecting layer comprises at least one layer selected from the group consisting of refracting facets, refracting prisms, refracting lenses, prism grooves, fresnel lenses, micro lens arrays, reflecting mirror, regions of physically deposited reflective media, regions of physically deposited light scattering media, geometric patterns of physically deposited media arranged as squares, circles, dots, lines, or bars, and combinations thereof whose result is to scatter, reflect, refract, diffract, or otherwise change direction of some fraction of light passing out from said output aperture.

45. The illuminating system as defined in claim 26 wherein the one or more LEDs are selected from the group consisting of semiconductor type light organic-type light emitting diodes, “

OLEDs”

, LED/OLED excited fluorescent materials, and combinations thereof.

46. An illuminating system comprising:

one or more sets of light emitting diodes (LEDs);

one or more rectangular reflecting elements, each of whose input aperture has an aperture area that bounds at least one of said one or more sets of LEDs and whose aperture shape generally follows the boundary of said one or more sets of LEDs, each of the one or more rectangular reflecting elements having an output aperture which is elevated above said input aperture at a height H established by the physical position of two opposing pairs of optically reflecting sidewalls having a mathematical curvatures substantially satisfying the geometric Sine Law expression d_i×

Sin θ

_i=d_j×

Sin θ

_j for each opposing pair of reflecting side walls, said output aperture height H being determined by the interrelated geometric Sine law expression H=[(d_i+d_j)/2]/Tan θ

_j, d_i being the distance between said opposing pair of reflecting sidewalls measured at their input aperture, d_j being the distance between said opposing pair of reflecting sidewalls measured at their output aperture, θ

_i being half the full emission angle of said one or more sets of LEDs at said input aperture of each said opposing pair of reflecting sidewalls, θ

_j being half the maximum emission angle occurring at said output aperture of each said opposing pair of reflecting sidewalls, each said maximum emission angle θ

_j combining to form the periphery of a substantially square or rectangular output beam;

a first light redirecting layer, positioned in optical communication with the output aperture of each of the one or more rectangular reflecting elements, opposite the one or more sets of sets of LEDS , each first light redirecting layer changing the direction of at least a portion of light received from the output aperture of each corresponding one or more reflecting elements; and

a second light redirecting layer in optical communication with said first light redirecting layer for receiving light from said first light redirecting layer.

47. The illuminating system as defined in claim 46 wherein said one or more rectangular reflecting elements are filled with air as a dielectric medium.

48. The illuminating system as defined in claim 46 wherein one or more rectangular reflecting elements are filled with a clear polymeric or glass-based material as a dielectric medium.

49. The illuminating system as defined in claim 46 wherein said first light redirecting layer is a clear and transparent optical coupling media of refractive index chosen to substantially match that of the internal medium of said one or more rectangular reflecting elements with that of the internal medium of said second light redirecting layer.

50. The illuminating system as defined in claim 49 wherein said one or more four-sided rectangular reflecting elements provide rectangular output light whose angular range satisfies conditions for total internal reflection within said second light redirecting layer.

51. The illuminating system as defined in claim 49 wherein the rectangular output beam from said one or more rectangular reflecting elements are substantially a mixture of wavelengths whose net color falls within the color coordinate and color temperature range classified generally as white.

52. The illuminating system as defined in claim 46 further comprising a third light redirecting layer, wherein said third light redirecting layer is a light guide plate having light redirecting and extracting features selected from the group consisting of a spatial distribution of one or more of prism facets, prism grooves or prism elements whose redirecting and extracting nature operates without change in the state of light polarization.

53. The illuminating system as defined in claim 52 wherein said light guide plate is made from a clear and transparent glass of polymeric material that is free of mechanical strain and optical birefringence.

54. The illuminating system as defined in claim 53 wherein said light guide plate is made of an ultra-high purity form of poly methyl methacrelate (aka, PMMA or acrylic).

55. The illuminating system as defined in claim 53 wherein said light guide plate is made of a sheet of glass.

56. The illuminating system as defined in claim 55 wherein said sheet of glass is of the type used within the construction of commercial display devices or within other reflective displays requiring top or front illumination.

57. The illuminating system of claim 46 wherein the first light redirecting layer is selected from the group consisting of at least one of light redirecting refracting facets, light redirecting refracting prisms, light redirecting refracting prism grooves, light redirecting dichroic reflectors, clear and transparent optical coupling medium, or a second four-sided square or rectangular reflecting element whose output aperture is elevated above said input aperture a height H established by the physical position of two opposing pairs of optically reflecting sidewalls having a mathematical curvatures substantially satisfying the geometric Sine Law expression d_m×

Sin θ

_m=d<sub>n×

Sin θ

n</sub> for each opposing pair of reflecting side walls, said output aperture height T being determined by the interrelated geometric Sine law expression T=[(d_m+dn)/2]/Tan θ

_k, d_m being the distance between said opposing pair of reflecting sidewalls measured at their input aperture, d_n being the distance between said opposing pair of reflecting sidewalls measured at their output aperture, θ

_k being half the full emission angle as appearing at either said input θ

_n or said output θ

_m aperture of each said opposing pair of reflecting sidewalls, θ

_k being the lesser of θ

_n or θ

_m, each said emission angle combining to form the periphery of a substantially square or rectangular out beam, that otherwise change directions and intermix colors of some fraction of light passing out from said output aperture.

58. The illumination system of claim 46 wherein the one or more four-sided rectangular reflecting elements have a square cross-section when cut on any plane intersecting the optical axis of said rectangular reflecting elements parallel to said input aperture or said output aperture and have a square output beam.

59. The illumination system of claim 46 wherein the one or more four-sided rectangular reflecting elements have a rectangular cross-section when cut on any plane intersecting the optical axis of said rectangular reflecting elements parallel to said input aperture or said output aperture and have a square output beam.

60. The illumination system of claim 46 wherein the second light redirecting layer comprises light redirecting features selected from the group consisting of a light guiding bar having a constant square, rectangular or trapezoidal cross-section, a light guiding bar having a constant square, rectangular or trapezoidal cross-section containing a distribution of light extracting elements within or on one or more surfaces, and a light guiding bar surrounded by three non-contacting mirror surfaces.

61. The illumination system of claim 60, wherein the cross-sectional area is substantially constant along the second light redirecting layer.

62. The illumination system of claim 60, wherein the cross-sectional area varies along at least a portion of the second light redirecting layer.