Illumination system with optical concentrator and wavelength converting element

• US 20070081336A1
• Filed: 10/11/2005
• Published: 04/12/2007
• Est. Priority Date: 10/11/2005
• Status: Active Grant

• Current Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Harbers, Gerard, Bierhuizen, Serge
• Granted Patent: US 7,543,959 B2
• Time in Patent Office: Days
• US Class Current: 362/293
• 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 light emitting device includes a light emitting element, an optical concentrator, such as a compound parabolic concentrator, a dichroic filter between the light emitting element and the optical concentrator and a wavelength converting material, such as a phosphor. The optical concentrator receives light from the light emitting element, via the dichroic filter, and emits the light from an exit surface, which is smaller than the entrance surface. The optical concentrator may be manufactured from a material with a high refractive index, such as sapphire. The wavelength converting material is, e.g., disposed over the exit surface. The radiance of the wavelength converting material is increased by pumping the wavelength converting material through a high index of refraction material and outputting the converted light into a low refractive index medium, such as air.

Claims

1. An apparatus comprising:

a light emitting element;

an optical concentrator having an entrance surface and an exit surface, the entrance surface optically coupled to the light emitting element, the optical concentrator concentrating the light received at the entrance surface to the exit surface which is smaller than the entrance surface;

a wavelength converting material mounted on the exit surface of the optical concentrator, the wavelength converting material converting at least a portion of the light emitted by the light emitting element to a one or more wavelengths; and

a dichroic filter disposed between the light emitting element and the wavelength converting element, wherein the dichroic filter reflects light emitted by the wavelength converting element having the one or more wavelengths.

2. The apparatus of claim 1, wherein the dichroic filter is disposed between the light emitting element and the optical concentrator so that light emitted from the light emitting element passes through the dichroic filter before reaching the entrance surface of the optical concentrator.

3. The apparatus of claim 1, wherein the light emitting element is at least one light emitting diode.

4. The apparatus of claim 3, wherein the light emitting element is an array of light emitting diodes.

5. The apparatus of claim 3, wherein the light emitting element is a plasma light source.

6. The apparatus of claim 1, wherein the optical concentrator has an index of refraction of approximately 1.4 or higher and the wavelength converting material generates light into a medium with an index of refraction of approximately 1.0.

7. The apparatus of claim 6, wherein a layer is disposed between the wavelength converting material and the medium into which the wavelength converting material generates light.

8. The apparatus of claim 1, wherein the wavelength converting element emits converted light having the one or more wavelengths and unconverted light, the apparatus further comprising:

a collection optic after the wavelength converting material, the collection optic reducing a cone angle of the light emitted by the wavelength converting material; and

a second dichroic coupled to the collection optic with the collection optic between the second dichroic and the wavelength converting material, the second dichroic filter transmits at least a portion of at least one the converted light and the unconverted light and reflects at least a portion of at least one of the converted light and the unconverted light.

9. The apparatus of claim 7, wherein the layer is at least one of a protective layer, a diffractive optical element, a hologram element, a dichroic filter, and a reflective polarizer.

10. The apparatus of claim 1, wherein the optical concentrator comprises one or more refractive lenses.

11. The apparatus of claim 1, wherein the optical concentrator comprises reflective surfaces that define the exit surface through which light exits the optical concentrator, wherein the optical concentrator is shaped such that light received through the entrance surface of the optical concentrator is directed toward the exit surface.

12. The apparatus of claim 11, wherein the reflective surfaces of the optical concentrator are formed from a reflective material overlying a portion of the optical concentrator.

13. The apparatus of claim 11, wherein at least a portion of the optical concentrator is one of BK7 glass, B270 glass, SF10 glass, SF57 glass, F2 glass, Zeonex plastic, Ultem plastic, and sapphire.

14. The apparatus of claim 1, wherein the optical concentrator is a compound parabolic concentrator.

15. The apparatus of claim 1, wherein the optical concentrator comprises:

a first element formed from a cavity within a solid body, the walls of the solid body are reflective, a first end of the first element defining the entrance surface of the optical concentrator and a second end of the cavity defining an exit surface of the first element; and

a second element formed from a solid transparent body with reflective sidewalls, the first end of the second element defining an entrance surface of the second element that is coupled to the exit surface of the first element, and a second end of the second element defining the exit surface of the optical concentrator.

16. The apparatus of claim 15, wherein the second element further comprises at least one additional layer of material on the solid transparent body, the at least one additional layer having a higher index of refraction than the solid transparent body.

17. The apparatus of claim 1, further comprising a collection optic between the light emitting element and the optical concentrator, the collection optic reduces a cone angle of the light emitted from the light emitting element before the light reaches the optical concentrator.

18. The apparatus of claim 17, wherein the collection optic is at least one of a rectangular angle transformer, a condenser lens, a Fresnel lens, and a total internal reflection surfaces (TIR) lens.

19. The apparatus of claim 17, further comprising:

a second optical concentrator having an entrance surface and an exit surface, the entrance surface optically coupled to receive light generated by the wavelength converting material, the second optical concentrator concentrating the light from the wavelength converting material to the exit surface, which is smaller than the entrance surface;

a second dichroic filter disposed between the wavelength converting material and the optical concentrator so that light generated from the light emitting element passes through the second dichroic filter before reaching the entrance surface of the second optical concentrator;

a second wavelength converting material coupled to the exit surface of the second optical concentrator, the wavelength converting material converting at least a portion of the light generated by the wavelength converting material to one or more wavelengths of light which are reflected by the second dichroic filter; and

a second collection optic between the wavelength converting material and the second optical concentrator, the second collection optic reduces a cone angle of the light generated by the wavelength converting material before the light reaches the second optical concentrator.

20. The apparatus of claim 19, further comprising:

a third collection optic that is located after the second wavelength converting material, the second collection optic approximately reduces a cone angle of the light generated by the second wavelength converting material.

21. The apparatus of claim 1, wherein the light emitting element is a first light emitting element, the apparatus further comprising:

a second light emitting element that emits light having different wavelengths from the light emitted by the first light emitting element; and

a dichroic beam splitter disposed to transmit the light emitted by the first light emitting element toward the optical concentrator and disposed to reflect the light emitted by the second light emitting element toward the optical concentrator.

22. The apparatus of claim 21, further comprising:

a first lens between the first light emitting element and the dichroic beam splitter;

a second lens between the second light emitting element and the dichroic beam splitter; and

a third lens between the dichroic beam splitter and the optical concentrator.

23. The apparatus of claim 1, wherein the wavelength converting material is disposed on the exit surface.

24. The apparatus of claim 1, wherein the wavelength converting material is a phosphor.

25. The apparatus of claim 1, wherein the etendue of an exit surface of the wavelength converting element is smaller than the etendue of the light emitting element.

26. A method comprising:

generating light having a first range of wavelengths;

transmitting the light through a dichroic filter;

concentrating the light; and

converting at least a portion of the concentrated light to converted light having a second range of wavelengths, wherein the dichroic filter transmits light having the first range of wavelengths and reflects light having the second range of wavelengths.

27. The method of claim 26, wherein generating light comprises emitting light from one or more light emitting diodes.

28. The method of claim 26, further comprising collimating the light either reflectively or refractively before transmitting the light through a dichroic filter.

29. The method of claim 26, wherein concentrating the light is performed by refracting the light.

30. The method of claim 26, wherein concentrating the light is performed by reflecting the light.

31. The method of claim 26, wherein concentrating the light is performed in a compound parabolic concentrator.

32. The method of claim 26, wherein concentrating the light is performed in a medium with an index of refraction of approximately 1.4 or higher and the converted light is emitted into an medium with an index of refraction of approximately 1.0.

33. The method of claim 26, wherein concentrating the light is performed in one of a BK7 glass, B270 glass, SF10 glass, SF57 glass, F2 glass, Zeonex plastic, Ultem plastic, and sapphire element.

34. The method of claim 26, further comprising:

transmitting the converted light through a second dichroic filter;

concentrating the converted light;

converting at least a portion of the concentrated light to twice converted light having a third range of wavelengths, wherein the second dichroic filter transmits light having the second range of wavelengths and reflects light having the third range of wavelengths.

35. The method of claim 34, further comprising collimating the twice converted light either reflectively or refractively.

36. The method of claim 26, further comprising:

generating light having a third range of wavelengths;

combining the light having the third range of wavelengths with the light having the first range of wavelengths;

wherein transmitting the light through a dichroic filter transmits the combined light, concentrating the light concentrates the combined light and converting at least a portion of the concentrated light concentrates at least a portion of the concentrated combined light.