OPTICAL DEVICES FOR CONTROLLED COLOR MIXING

• US 20070268694A1
• Filed: 04/18/2007
• Published: 11/22/2007
• Est. Priority Date: 04/18/2006
• Status: Active Grant

• Current Assignee: Lighting Science Group Corporation (Pegasus Capital Advisors, L.P.)
• Original Assignee: Lamina Ceramics, Inc.
• Inventors: Harrah, Shane, Bailey, Edward
• Granted Patent: US 8,866,168 B2
• Time in Patent Office: Days
• US Class Current: 362/231
• CPC Class Codes: F21V 9/00 Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters coloured shades F21V1/00; elements characterised by cooling arrangements F21V29/502
• CPC Class Codes: G02B 19/0014 at least one surface having optical power
• 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 27/0955 Lenses lenses per se G02B3/00
• 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: H01L 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/54 having a particular shape
• CPC Class Codes: H01L 33/58 Optical field-shaping elements

Abstract

The present invention provides a multicolor LED assembly packaged with improved and controlled color mixing to create a more uniform color mixture. The assembly includes at least one lens overlying an encapsulant which encapsulates a plurality of LED dies. The lens includes a top surface and a bottom surface with the contour of the bottom surface designed to redirect light from each of the LED dies in different directions towards the top surface of the lens. The contoured shaped of the bottom surface of the lens redirects light from each of the plurality of LED dies such that illuminance and luminous intensity distributions of the plurality of LED dies substantially overlap, wherein the deviation from complete overlap is less than a predetermined amount which is substantially imperceptible to the average human eye.

Claims

1. An assembly of multicolor light emitting diodes packaged for controlled color mixing, comprising:

a substrate;

a plurality of light-emitting diode (LED) dies mounted overlying the substrate, each die emitting light of a corresponding color;

an optically transmissive encapsulant covering the plurality of LED dies; and

at least one lens having a top surface and a bottom surface overlying the encapsulant, the bottom surface of the lens including a predetermined shape to redirect light from each of the plurality of LED dies such that an overlap of the illuminance and luminous intensity distributions of the plurality of LED is substantially increased, wherein the deviation from complete overlap is substantially imperceptible to the average human eye.

2. The assembly of multicolor light emitting diodes of claim 1, wherein said deviation is equal to or less than a predetermined amount that falls within the areas of MacAdam ellipses plotted on chromaticity charts for the colors emitted and mixed together by the plurality of LED dies.

3. The assembly of multicolor light emitting diodes of claim 2, wherein the predetermined bottom surface comprises a microlenslet array.

4. The assembly of multicolor light emitting diodes of claim 3, wherein the microlenslet array has a microsurface roughness (MSR) prescription.

5. The assembly of multicolor light emitting diodes of claim 4, wherein the MSR is described by one of random distribution function, angle resolve scatter function, Harvey BSDF function, user-defined BSDF function, and phong distribution function.

6. The assembly of multicolor light emitting diodes of claim 5, wherein the random distribution function describes the contours of a V-cavity.

7. The assembly of multicolor light emitting diodes of claim 4, wherein the MSR is described by one or more of a forward Harvey, retro-Harvey, Lambertian, Poisson, forward phong, or retro phong distribution function.

8. The assembly of multicolor light emitting diodes of claim 4, wherein the microlenslet array is divided into two or more zones comprising two or more different MSR prescriptions.

9. The assembly of multicolor light emitting diodes of claim 4, wherein the top surface of the lens has a shape described by one of radius, radius plus conic constant, radius plus conic constant plus aspheric, radius plus conic constant plus aspheric plus global general polynomial, global Zernike deformation, dioptric total internal reflection (TIR), free-form Non-Uniform Rational B-Spline (NURBS) defined TIR, Fresnel plus TIR, diffractive optical element surface, biconic, cartoval, Dielectric Total Internal Reflecting Concentrator, Confocal Elliptic Concentrator, and Multi-Focal Parabolic Concentrator surface.

10. The assembly of multicolor light emitting diodes of claim 3, wherein the microlenslet array is a micro-fly'"'"'s eye lenslet array.

11. The assembly of multicolor light emitting diodes of claim 10, wherein the micro-fly'"'"'s eye lenslet array has polygonal-shaped lenslets.

12. The assembly of multicolor light emitting diodes of claim 10, wherein the micro-fly'"'"'s eye lenslet array has lenslets in the shape of one of hexagons, squares, rectangles, circles (radius), radius plus conic constant, aspheric, free-form NURBS, and Zernike polynomials.

13. The assembly of multicolor light emitting diodes of claim 10, wherein the micro-fly'"'"'s eye lenslet array undergoes a global deformation.

14. The assembly of multicolor light emitting diodes of claim 10, wherein the microlenslet arrays are distributed randomly.

15. The assembly of multicolor light emitting diodes of claim 10, wherein the top surface of the lens has a shape described by one of radius, radius plus conic constant, radius plus conic constant plus aspheric, radius plus conic constant plus aspheric plus global general polynomial, global Zernike deformation, dioptric total internal reflection (TIR), free-form Non-Uniform Rational B-Spline (NURBS) defined TIR, Fresnel plus TIR, diffractive optical element surface, biconic, cartoval, Dielectric Total Internal Reflecting Concentrator, Confocal Elliptic Concentrator, and Multi-Focal Parabolic Concentrator surface.

16. The assembly of multicolor light emitting diodes of claim 3, wherein the microlenslet array has a Voronoi lenslet array structure.

17. The assembly of multicolor light emitting diodes of claim 16, wherein the top surface of the lens has a shape described by one of radius, radius plus conic constant, radius plus conic constant plus aspheric, radius plus conic constant plus aspheric plus global general polynomial, global Zernike deformation, dioptric total internal reflection (TIR), free-form Non-Uniform Rational B-Spline (NURBS) defined TIR, Fresnel, diffractive optical element, biconic, cartoval, Dielectric Total Internal Reflecting Concentrator, Confocal Elliptic Concentrator, and Multi-Focal Parabolic Concentrator surface.

18. The assembly of multicolor light emitting diodes of claim 2, wherein the at least one lens comprises refractive microparticles.

19. The assembly of multicolor light emitting diodes of claim 18, wherein the predetermined bottom surface has one of an MSR, a micro-fly'"'"'s eye lenslet array, and a Voronoi lenslet array structure.

20. The assembly of multicolor light emitting diodes of claim 18, wherein the top surface of the lens has a shape described by one of radius, radius plus conic constant, radius plus conic constant plus aspheric, radius plus conic constant plus aspheric plus global general polynomial, global Zernike deformation, dioptric total internal reflection (TIR), free-form Non-Uniform Rational B-Spline (NURBS) defined TIR, Fresnel plus TIR, diffractive optical element, biconic, cartoval, Dielectric Total Internal Reflecting Concentrator, Confocal Elliptic Concentrator, and Multi-Focal Parabolic Concentrator surface.

21. The assembly of multicolor light emitting diodes of claim 2, wherein the at least one lens comprises reflective microparticles.

22. The assembly of multicolor light emitting diodes of claim 21, wherein the predetermined bottom surface has one of a micro-fly'"'"'s eye, and a Voronoi lenslet array structure.

23. The assembly of multicolor light emitting diodes of claim 21, wherein the top surface of the lens has a shape described by one of radius, radius plus conic constant, radius plus conic constant plus aspheric, radius plus conic constant plus aspheric plus global general polynomial, global Zernike deformation, dioptric total internal reflection (TIR), free-form Non-Uniform Rational B-Spline (NURBS) defined TIR, Fresnel plus TIR, diffractive optical element, biconic, cartoval, Dielectric Total Internal Reflecting Concentrator, Confocal Elliptic Concentrator, and Multi-Focal Parabolic Concentrator surface.

24. The assembly of multicolor light emitting diodes of claim 21, wherein the reflective microparticles are configured to form microtunnels.

25. The assembly of multicolor light emitting diodes of claim 2, wherein the top surface of the at least one lens is faceted.

26. The assembly of multicolor light emitting diodes of claim 25, wherein the predetermined bottom surface has one of a micro-fly'"'"'s eye, and a Voronoi lenslet array structure.

27. The assembly of multicolor light emitting diodes of claim 25, wherein the top surface of the lens has a shape described by one of radius, radius plus conic constant, radius plus conic constant plus aspheric, radius plus conic constant plus aspheric plus global general polynomial surface, global Zernike deformation, dioptric total internal reflection (TIR), free-form Non-Uniform Rational B-Spline (NURBS) defined TIR, Fresnel plus TIR, diffractive optical element, biconic, cartoval, Dielectric Total Internal Reflecting Concentrator, Confocal Elliptic Concentrator, and Multi-Focal Parabolic Concentrator.

28. The assembly of multicolor light emitting diodes of claim 2, wherein the at least one lens is formed of multiple lobes.

29. The assembly of multicolor light emitting diodes of claim 28, wherein the predetermined bottom surface has one of a micro-fly'"'"'s eye, and a Voronoi lenslet array structure.

30. The assembly of multicolor light emitting diodes of claim 28, wherein the top surface of each lobe has a shape described by one of radius, radius plus conic constant, radius plus conic constant plus aspheric, radius plus conic constant plus aspheric plus global general polynomial surface, global Zernike deformation, dioptric total internal reflection (TIR), free-form Non-Uniform Rational B-Spline (NURBS) defined TIR, Fresnel plus TIR, diffractive optical element, biconic, cartoval, Dielectric Total Internal Reflecting Concentrator, Confocal Elliptic Concentrator, and Multi-Focal Parabolic Concentrator.

31. The assembly of multicolor light emitting diodes of claim 2, wherein the optically transmissive encapsulant covering the plurality of LED dies is surrounded by a first reflector.

32. The assembly of multicolor light emitting diodes of claim 31, wherein the at least one lens is surrounded by a second reflector above said first reflector.

33. The assembly of multicolor light emitting diodes of claim 32, wherein the first reflector has a spline shape described by one of a polynomial, Bezier, and NURBS surface.

34. The assembly of multicolor light emitting diodes of claim 32, wherein the predetermined bottom surface has one of a micro-fly'"'"'s eye, and a Voronoi lenslet array structure.

35. The assembly of multicolor light emitting diodes of claim 32, wherein the top surface of the lens has a shape described by one of radius, radius plus conic constant, radius plus conic constant plus aspheric, radius plus conic constant plus aspheric plus global general polynomial surface, global Zernike deformation, dioptric total internal reflection (TIR), free-form Non-Uniform Rational B-Spline (NURBS) defined TIR, Fresnel plus TIR, diffractive optical element, biconic, cartoval, Dielectric Total Internal Reflecting Concentrator, Confocal Elliptic Concentrator, and Multi-Focal Parabolic Concentrator.

36. The assembly of multicolor light emitting diodes of claim 32, wherein the second reflector comprises a plurality of randomly-perturbed microfacets.

37. The assembly of multicolor light emitting diodes of claim 36, wherein interfacet spaces of randomly-perturbed microfacets are described by NURBS surfaces.

38. The assembly of multicolor light emitting diodes of claim 36, wherein the microfacets have shapes described by one of diamond, triangular, hexagonal, other polygonal shapes, and combinations thereof.

39. The assembly of multicolor light emitting diodes of claim 2, wherein the optically transmissive encapsulant and the at least one lens is surrounded by an RXI concentrator.

40. The assembly of multicolor light emitting diodes of claim 39, wherein the predetermined bottom surface has one of a micro-fly'"'"'s eye, and a Voronoi lenslet array structure.

41. The assembly of multicolor light emitting diodes of claim 39, wherein the top surface of the lens has a shape described by one of radius, radius plus conic constant, radius plus conic constant plus aspheric, radius plus conic constant plus aspheric plus global general polynomial surface, global Zernike deformation, dioptric total internal reflection (TIR), free-form Non-Uniform Rational B-Spline (NURBS) defined TIR, Fresnel plus TIR, diffractive optical element, biconic, cartoval, Dielectric Total Internal Reflecting Concentrator, Confocal Elliptic Concentrator, and Multi-Focal Parabolic Concentrator.

42. A lens for controlled color mixing of a plurality of light-emitting diode (LED) dies, the plurality having at least two colors, said lens having a top surface and a bottom surface overlying the LED dies, the bottom surface of the lens including a predetermined shape to receive and redirect light from each of the plurality of LED dies through and out of the top surface of the lens such that illuminance and luminous intensity distributions of the plurality of LED dies substantially overlap, wherein the deviation from complete overlap is substantially imperceptible to the average human eye.

43. The lens of claim 42, wherein the predetermined bottom surface comprises a microlenslet array.

44. The lens of claim 43, wherein the microlenslet array has a microsurface roughness (MSR) prescription.

45. The lens of claim 43, wherein the microlenslet array includes one of a micro-fly'"'"'s eye and a Voronoi lenslet array structure.

46. The lens of claim 43, wherein the at least one lens comprises refractive microparticles.

47. The lens of claim 43, wherein the at least one lens comprises reflective microparticles.

48. The lens of claim 47, wherein the reflective microparticles are configured to form microtunnels.

49. The assembly of multicolor light emitting diodes of claim 43, wherein the top surface of the at least one lens is faceted.

50. A lens for controlled color mixing of a plurality of light-emitting diode (LED) dies, the plurality having at least two colors, said lens overlying the plurality of LED dies and surrounded by a reflector having a spline shape, said lens having at least one surface predetermined to receive and redirect light from each of the plurality of LED dies such that illuminance and luminous intensity distributions of the plurality of LED dies substantially overlap, wherein the deviation from complete overlap is substantially imperceptible to the average human eye.

51. The lens of claim 50, wherein said deviation is equal to or less than a predetermined amount that falls within the areas of MacAdam ellipses plotted on a chromaticity charts for the colors emitted and mixed together by the plurality of LED dies.

52. The lens of claim 50, wherein said reflector has a shape described by one of a polynomial, Bezier, and NURBS surface.

53. The lens of claim 50, wherein the reflector comprises a plurality of randomly-perturbed microfacets.

54. The lens of claim 53, wherein interfacet spaces of randomly-perturbed microfacets are described by NURBS surfaces.

55. A lens for controlled color mixing of a plurality of light-emitting diode (LED) dies, the plurality having at least two colors, said lens overlying the plurality of LED dies and surrounded by an RXI concentrator, said lens having at least one predetermined surface to receive and redirect light from each of the plurality of LED dies such that illuminance and luminous intensity distributions of the plurality of LED dies substantially overlap, wherein the deviation from complete overlap is substantially imperceptible to the average human eye.

56. The lens of claim 55, wherein said deviation is equal to or less than a predetermined amount that falls within the areas of MacAdam ellipses plotted on a chromaticity charts for the colors emitted and mixed together by the plurality of LED dies.

57. A method for determining acceptable color uniformity of a light beam, comprising the steps of:

choosing three colors at which to make measurements, the each color being a constituent of white light;

for each selected color perform the steps of;

measuring a plurality of x,y chromaticity samples of the light beam, at the selected color, at points in vertical and horizontal distribution extrema where the intensity distribution falls to approximately e<sup>−

2</sup> of the on-axis or peak luminous intensity, thereby defining an outer periphery of the light beam;

measuring a plurality of x,y chromaticity samples of the light beam at points located on a spiral from the outer periphery to the on-axis or peak luminous intensity;

measuring a plurality of x,y chromaticity samples of the light beam, for the selected color, at selected angular radials at approximately the full width at half maximum (FWHM) point;

converting mathematically the x,y chromaticity samples for the selected color to a u,v space representation;

plotting MacAdam ellipses from the u,v space representation of the chromaticity samples for the selected color;

calculating a deltaE parameter for the selected color, the deltaE parameter representing the magnitude of the color difference perceived between two color samples which are specified in terms of tristimulus values;

determining acceptable color uniformity for the selected color, wherein acceptable color uniformity for the selected color is attained when the deltaE parameter for the selected color is less than the 2-step MacAdam'"'"'s ellipse or when the deltaE parameter for the selected color matches or exceeds the maximum chromaticity difference of a selected standard;

resulting in acceptable color uniformity of the light beam if the color uniformity for the first color, the second color, and the third color are all acceptable.

58. The method of claim 57, wherein the three colors are selected from the group consisting of red, green and blue.

59. The method of claim 57, wherein the three colors are selected from the group consisting of cyan, yellow and magenta.

60. The method of claim 57, wherein the steps of determining acceptable color uniformity for the three colors include the additional step of determining whether the Correlated Color Temperature (CCT) and chromaticity differences are less than a predetermined level over the field of measurement.

61. A method for using light control facets and randomized facet perturbations of the primary reflector to improve color uniformity, comprising the steps of:

dividing the primary reflector into horizontal slices and vertical slices, resulting in a plurality of facets, the facets each having a parametric surface described by x=x(φ

, φ

), y=y(φ

, φ

), z=z(φ

, φ

);

calculating transformation vectors a′

=[xφ

, yφ

, zφ

], b′

=[xΨ

, yΨ

, zΨ

] for each facet;

calculating a unit normal vector N′

=(a′

×

b′

)/(sqrt((abs(a′

ˆ

2)abs(b′

ˆ

2)−

abs(a‘

b’

)ˆ

2) for each facet;

calculating a metric tensor, by taking an inner product of a plurality of tangency spaces associated with a reflector facet manifold where the inner product is symmetric, nondegenerate, and bilinear in 3D vector space;

calculating a descriminant g of the metric tensor;

calculating a vector normal to the surface N=r1′

×

r2′

/(sqrt(g))=∈

ij*r′

ˆ

j;

applying a predetermined perturbation to each facet by deviating an angular facet control vector from the unit normal vector by a random angle between an upper and lower bound;

resulting in an integrated primary reflector which both collimates the light, and randomizes color specific phase to improve the intensity distribution function overlap of Cyan, Magenta, and Yellow.

62. A method to construct an RXI concentrator, comprising the steps of:

filling the intermediary air of a cassegrain telescope with a refractive dielectric media, the cassegrain telescope comprising a primary reflector and a secondary reflector;

adding a plurality of micro-facets to the primary reflector of the cassegrain telescope;

randomizing the micro-facets with respect to an angle from the normal of each micro-facet using a vector perturbation;

changing the micro-facets into an organic shape or into an arbitrary polygonal parameter shape;

applying the vector perturbation to the secondary reflector using a perturbation factors tessellating the surface of the refractive dielectric at the exit aperture of the RXI concentrator with a plurality of micro-lenslets, each micro-lenslet surface characterized by a sag;

randomizing the sag with one or more of radii, aspherics, NURBS and global Zernike deformation solving the Monge-Ampere partial differential equation, in terms of optimal global deformation on the primary reflector and the secondary reflector;

resulting in an RXI concentrator which optimally combines multi-primary phase in the far field.

63. The method of claim 62, wherein the refractive dielectric media includes a plurality of micro-spheres having an index of refraction different than the index of refraction of the surrounding dielectric media.