Compact mixing cavity for multiple colors of LEDs

• US 7,494,228 B2
• Filed: 05/21/2007
• Issued: 02/24/2009
• Est. Priority Date: 04/11/2005
• Status: Expired due to Fees

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Inventors: Holman, Robert H., Scheffel, Laurie, Keuper, Matthijs H., Harbers, Gerard
• Primary Examiner(s): Lee; Diane I
• Assistant Examiner(s): Cruz; Magda
• Application Number:
  US11/751,594
• Publication Number:
  US 20080030984A1
• Time in Patent Office: 645 Days
• Field of Search: 353/94, 353/97, 353/98, 353/99, 385/146, 385/129, 385/132, 362/231, 362/19, 362/26, 362/293, 362/555, 359/490, 359/634, 313/372, 313/475, 348/338, 348/339
• US Class Current: 353/94
• CPC Class Codes: G02B 19/0023 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 19/0095 for use with ultraviolet radiation
• CPC Class Codes: G02B 27/0983 being curved
• CPC Class Codes: G02B 27/1053 having a single light modulator for all colour channels
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 27/149 using crossed beamsplitting surfaces, e.g. cross-dichroic cubes or X-cubes
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G03B 21/204 using secondary light emission, e.g. luminescence or fluorescence using different colours G03B33/00; if related to video signals H04N9/3197
• 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

For mixing different light colors from different LEDs or energized phosphors, an elongated mixing tunnel is used having a reflective inner surface. LEDs of different colors are optically coupled along the length of the mixing tunnel and at a first end of the tunnel. Light coupled along the length of the tunnel is reflected by an angled dichroic mirror that selectively reflects the incoming color light towards a single output port of the mixing tunnel. The dichroic mirror passes all other colors of light being transmitted towards the output port of the tunnel. Two, three, or more colors of LEDs can be used. Efficient and compact ways to energize phosphors are also described. Other optical techniques are also described.

Claims

1. A light generating system comprising:

an elongated light mixing tunnel having a reflective inner surface for mixing light, the mixing tunnel having a light output opening at a first end of the mixing tunnel;

the mixing tunnel having a first opening at a first position along a length of the mixing tunnel for receiving light from at least a first light emitting diode (LED) emitting light of a first color;

an angled first dichroic mirror positioned in the mixing tunnel over the first opening that reflects light of the first color in a direction of the first end of the mixing tunnel and passes light from colors other than the first color; and

the mixing tunnel having at least a second opening for receiving light from at least a second LED emitting light of a second color different from the first color such that light of the first color and light of the second color are mixed in the mixing tunnel and output at the light output opening.

2. The system of claim 1 wherein the mixing tunnel has the second opening at a second position along the length of the mixing tunnel for receiving light from the second LED;

the system further comprising;

an angled second dichroic mirror positioned in the mixing tunnel over the second opening that reflects light of the second color in a direction of the first end of the mixing tunnel and passes light from colors other than the second color.

3. The system of claim 2 wherein the mixing tunnel has a third opening at a second end of the mixing tunnel for receiving light from a third LED emitting light of a third color different from the first color and second color.

4. The system of claim 1 wherein the mixing tunnel has the second opening at a second end of the mixing tunnel for receiving light from at least the second LED.

5. The system of claim 1 wherein the mixing tunnel has the second opening at a second position along the length of the mixing tunnel for receiving light from the second LED;

the system further comprising;

an angled second dichroic mirror positioned in the mixing tunnel over the second opening that reflects light of the second color in a direction of the first end of the mixing tunnel and passes light from colors other than the second color;

the mixing tunnel having a third opening at a second end of the mixing tunnel for receiving light from a third LED emitting light of a third color,

the first dichroic mirror at least passing light of the third color, the second dichroic mirror at least passing light of the third color and the first color, such that the light from the first LED, second LED, and third LED is all directed towards the light output opening at the first end of the mixing tunnel and mixes in the mixing tunnel to produce a mixed light output.

6. The system of claim 1 wherein the first opening and the second opening have approximately a same cross-section.

7. The system of claim 1 further comprising at least one lens at the light output opening at the first end of the mixing tunnel.

8. The system of claim 1 further comprising at least one collimation optic attached to the light output opening of the mixing tunnel.

9. The system of claim 1 further comprising at least one lens at the first opening of the mixing tunnel.

10. The system of claim 1 further comprising at least one collection optic attached to the first opening of the mixing tunnel.

11. The system of claim 1 further comprising at least one lens at the second opening of the mixing tunnel.

12. The system of claim 1 further comprising at least one collection optic attached to the second opening of the mixing tunnel.

13. The system of claim 1 further comprising the mixing tunnel having at least a third opening for receiving light from at least a third LED emitting light of a third color different from the first color and second color, and at least one lens at the third opening of the mixing tunnel.

14. The system of claim 1 further comprising the mixing tunnel having at least a third opening for receiving light from at least a third LED emitting light of a third color different from the first color and second color, and at least one collection optic attached to the third opening of the mixing tunnel.

15. The system of claim 1 wherein a combination of colors mixed in the mixing tunnel is white light.

16. The system of claim 1 further comprising the mixing tunnel having at least a third opening for receiving light from at least a third LED emitting light of a third color different from the first color and second color.

17. The system of claim 16 wherein the first color, second color, and third color are selected from the group consisting of red, green, and blue.

18. The system of claim 16 wherein the first color is red, the second color is green, and the third color is blue.

19. The system of claim 16 wherein the first color is blue, the second color is green, and the third color is red.

20. The system of claim 16 wherein the first color is green, the second color is red, and the third color is blue.

21. The system of claim 1 wherein the mixing tunnel has flat side walls.

22. The system of claim 1 wherein the mixing tunnel has a cylindrical cross section.

23. The system of claim 1 further comprising a projection display system with the mixing tunnel supplying a light source for the projection display system.

24. A light generating system comprising:

an elongated light mixing tunnel having a reflective inner surface for mixing light, the mixing tunnel having a light output opening at a first end of the mixing tunnel;

the mixing tunnel having a first opening at a first position along a length of the mixing tunnel for receiving light from at least a first light emitting diode (LED) emitting light of a first color;

an angled first dichroic mirror positioned in the mixing tunnel over the first opening that reflects light of the first color in a direction of the first end of the mixing tunnel;

the mixing tunnel having a second opening at a second position along the length of the mixing tunnel for receiving light from a second LED emitting light of a second color;

an angled second dichroic mirror positioned in the mixing tunnel over the second opening that reflects light of the second color in a direction of the first end of the mixing tunnel; and

the mixing tunnel having a third opening at a second end of the mixing tunnel for receiving light from a third LED emitting light of a third color;

the first dichroic mirror at least passing light of the third color, the second dichroic mirror at least passing light of the third color and the second color, such that the light from the first LED, second LED, and third LED is all directed towards the light output opening at the first end of the mixing tunnel and mixes in the mixing tunnel to produce a mixed light output.

25. A method performed by a light generating system comprising:

optically coupling light from a first light emitting diode (LED) emitting light of a first color through a first opening in an elongated light mixing tunnel, the light mixing tunnel having a reflective inner surface for mixing light, the mixing tunnel having a light output opening at a first end of the mixing tunnel, the first opening being at a first position along a length of the mixing tunnel;

reflecting light from the first LED by an angled first dichroic mirror positioned in the mixing tunnel over the first opening, the light being reflected by the first dichroic mirror in a direction of the first end of the mixing tunnel, the first dichroic mirror passing light from colors other than the first color; and

optically coupling light from a second LED emitting light of a second color through a second opening in the mixing tunnel such that light of the first color and light of the second color are mixed in the mixing tunnel and output at the light output opening.