Light-emitting devices providing asymmetrical propagation of light

• US 9,863,605 B2
• Filed: 11/23/2012
• Issued: 01/09/2018
• Est. Priority Date: 11/23/2011
• Status: Active Grant

• Current Assignee: Quarkstar LLC
• Original Assignee: Quarkstar LLC
• Inventors: Haitz, Roland H., Smith, George E., Gardner, Robert C., Lerman, Louis
• Primary Examiner(s): Husar, Stephen F
• Application Number:
  US14/360,046
• Publication Number:
  US 20150003059A1
• Time in Patent Office: 1,873 Days
• CPC Class Codes: F21K 9/60 Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction
• CPC Class Codes: F21V 13/02 Combinations of only two kinds of elements
• CPC Class Codes: F21V 13/08 the elements being filters or photoluminescent elements and reflectors
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0061 the light source comprising a LED semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission H01L33/00
• CPC Class Codes: G02B 19/0066 in the form of an LED array
• CPC Class Codes: G02B 5/0236 the diffusion taking place within the volume of the element
• CPC Class Codes: G02B 5/0278 used in transmission
• 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 33/58 Optical field-shaping elements

Abstract

A variety of light-emitting devices for general illumination utilizing solid state light sources (e.g., light emitting diodes) are disclosed. In general, the devices include a scattering element in combination with an extractor element. The scattering element, which may include elastic and/or inelastic scattering centers, is spaced apart from the light source element. Opposite sides of the scattering element have asymmetric optical interfaces, there being a larger refractive index mismatch at the interface facing the light emitting element than the interface between the scattering element and the extractor element. Such a structure favors forward scattering of light from the scattering element. In other words, the system favors scattering out of the scattering element into the extractor element over backscattering light towards the light source element. The extractor element, in turn, is sized and shaped to reduce reflection of light exiting the light-emitting device at the devices interface with the ambient environment.

Claims

1. A light-emitting device, comprising:

multiple light-emitting elements including

a first light-emitting element configured to provide light having a first spectral power distribution during operation, and

a second light-emitting element configured to provide light having a second spectral power distribution different from the first spectral power distribution during operation;

a first optical element having a first surface spaced apart from the first and second light-emitting elements and positioned to receive light from the first and second light-emitting elements, the first optical element comprising

a plurality of inelastic scattering centers arranged to convert the light from the first light-emitting element into converted light that is substantially isotropically scattered, and

a plurality of elastic scattering centers arranged to substantially isotropically scatter the light from the second light-emitting element, and provide mixed light comprising the scattered light from the second light-emitting element and the converted light, the mixed light having a mixed spectral power distribution; and

a second optical element formed from a transparent material having an exit surface, the second optical element being in contact with the first optical element, there being an optical interface between the first and second optical elements at a place of contact, the optical interface being opposite the first surface of the first optical element, the second optical element being arranged to receive a portion of the mixed light through the optical interface;

wherein;

the light-emitting device comprises a medium adjacent the first surface of the first optical element having a refractive index no, and the first optical element comprises a material having a first refractive index n₁, where n₀<

n₁;

the transparent material has a refractive index, n₂, where n₀<

n₂;

the exit surface being a transparent surface that is shaped such that an angle of incidence on the exit surface of the mixed light provided by the first optical element that directly impinges on the exit surface is less than a critical angle for total internal reflection; and

the light-emitting device outputs a predetermined portion of the mixed light through the exit surface.

2. The light-emitting device of claim 1, wherein the first optical element is a shell that defines an enclosure into which light from the light-emitting elements is emitted, wherein the shell is shaped such that at least some light from the first surface directly propagates through the enclosure to the first surface.

3. The light-emitting device of claim 2, wherein the shell has a concave shape with respect to the enclosure.

4. The light-emitting device of claim 3, wherein the shell has an ellipsoidal shape.

5. The light-emitting device of claim 4, wherein the ellipsoidal shape is prolate or oblate.

6. The light-emitting device of claim 5, wherein the ellipsoidal shape is triaxial.

7. The light-emitting device of claim 1 further comprising a reflector having a reflective surface, the reflective surface and the first surface together defining an enclosure into which all light from the light-emitting elements is emitted.

8. The light-emitting device of claim 7, wherein the reflective surface is planar.

9. The light-emitting device of claim 7, wherein the first surface is planar.

10. The light-emitting device of claim 7, wherein the first surface is convex with respect to the enclosure.

11. The light-emitting device of claim 7, wherein the reflective surface comprises specular reflective portions.

12. The light-emitting device of claim 7, wherein the reflective surface comprises diffuse reflective portions.

13. The light-emitting device of claim 7, wherein the reflective surface is configured to direct light from the light-emitting elements towards the first surface.

14. The light-emitting device of claim 1 further comprising a third element formed from a transparent material positioned between the light-emitting elements and the first surface to receive light from the light-emitting elements and provide light to the first surface.

15. The light-emitting device of claim 1, further comprising a sensor arranged to receive a fraction of the portion of the mixed light prior to being output through the exit surface, the sensor configured to provide a sensor signal based on the fraction of the portion of the mixed light;

and

a control circuit in communication with the sensor configured to control power provided to the light-emitting elements in response to the sensor signal.

16. The light-emitting device of claim 1, wherein the second optical element comprises a first portion and a light guide, the first portion having the exit surface and being arranged to receive a first portion of the mixed light from the optical interface, and the light guide being arranged to receive a second portion of the mixed light from the optical interface and having a guiding surface configured to guide the received second portion of the mixed light away from the optical interface by reflecting at least some of the received second portion of the mixed light.

17. The light-emitting device of claim 1, wherein the exit surface comprises a first exit surface and a second exit surface, the first and second exit surfaces being at least partially transparent, and a step arranged between the first and second exit surfaces.

18. The light-emitting device of claim 1, wherein the exit surface is shaped such that an angle of incidence on the exit surface of the mixed light that directly impinges on the exit surface is less than the Brewster angle.

19. The light-emitting device of claim 1, wherein, for a cross-section, each point, p, on the exit surface has a corresponding radius of curvature, R(p), and the first and second optical elements are arranged so that each point on the optical interface is at least a corresponding distance, d(p), from the exit surface, where

d(p)=R(p)*(1−

k/n₂),

and k is a positive real number such that k<

n₂.

20. The light-emitting device of claim 19, wherein k/n₂<

0.8.

21. The light-emitting device of claim 19, wherein k<

1.

22. The light-emitting device of claim 19, wherein each point on the optical interface is the distance d(p) from the corresponding nearest point on the exit surface.

23. The light-emitting device of claim 1, wherein an axis of symmetry of the first optical element and an axis of symmetry of the second optical element are collinear.

24. The light-emitting device of claim 23, wherein the first and second light-emitting elements are positioned symmetrically about the axis of symmetry of the first optical element.

25. The light-emitting device of claim 1, wherein the inelastic scattering centers comprise a light-conversion material.