Cool light source

• US 20070097691A1
• Filed: 10/28/2005
• Published: 05/03/2007
• Est. Priority Date: 10/28/2005
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Wu, Kuohua
• Granted Patent: US 7,830,075 B2
• Time in Patent Office: Days
• US Class Current: 362/293
• CPC Class Codes: F21V 7/24 characterised by the material
• CPC Class Codes: F21V 7/28 characterised by coatings
• CPC Class Codes: G02B 5/22 Absorbing filters G02B5/201 - G02B5/208 take precedence
• CPC Class Codes: G02B 5/281 designed for the infrared light
• CPC Class Codes: G02B 5/285 comprising deposited thin solid films G02B5/281 - G02B5/289 take precedence; multilayered film filters for fibre optic multiplexing G02B6/29361

Abstract

A cool light source includes a reflector having a band-reject reflective coating and an underlying absorptive coating. The cool light source also includes a window with a band-pass transmission function that is substantially complimentary to the band-reject reflective coating.

Claims

1. A cool light source, comprising:

a reflector having a band-reject reflective coating and an underlying absorptive coating; and

a window with a band-pass transmission function that is complimentary to the band-reject reflective coating.

2. The cool light source of claim 1, wherein the window includes a short-wave pass filter in optical series with a long-wave pass filter.

3. The cool light source of claim 2 wherein the window includes a substrate and the short-wave pass filter is on an opposite side of the substrate than the long-wave pass filter.

4. The cool light source of claim 2 wherein the window includes a substrate and the short-wave pass filter is on the same side as the long-wave pass filter.

5. The cool light source of claim 2 wherein the short-wave pass filter allows transmission of light in substantially the visible region.

6. The cool light source of claim 2 wherein the long-wave pass filter allows transmission of light in substantially the visible region and IR regions.

7. The cool light source of claim 1 wherein the band-reject reflective coating substantially reflects light in the visible region and at least partially passes light in the UV region and IR regions to the absorptive layer.

8. The cool light source of claim 7 wherein the degree of partially passing light in the UV and IR regions is greater than 50%.

9. The cool light source of claim 1 wherein the window includes a far IR filter.

10. The cool light source of claim 1 wherein the reflector includes a light source from the group consisting of mercury-arc, xenon-arc, halogen, and metal halide.

11. A reflector having a concave cavity, comprising:

an absorptive layer disposed on the concave cavity;

a reflective filter coating disposed on the absorptive layer adapted to reflect a band of wavelengths and to transmit wavelengths outside of the band of wavelengths;

a window including an optical coating with a transmission function complementary to the band of wavelengths and a reflection function complimentary to the wavelengths outside of the band of wavelengths.

12. The reflector of claim 11, wherein the optical coating on the window includes at least two separate optical coatings on opposite sides of the window.

13. The reflector of claim 11, wherein the optical coating includes a short-wave pass filter in optical series with a long-wave pass filter.

14. The reflector of claim 11, the reflection of wavelengths at the window outside the band of wavelengths is greater than 80% on average.

15. The reflector of claim 11, wherein the transmission of wavelengths outside the band of wavelengths by the reflective filter coating is greater than 50% on average.

16. The reflector of claim 11, wherein the band of wavelengths is within the visible region and wherein the wavelengths outside of the band of wavelengths include the UV and IR regions.

17. The reflector of claim 11, wherein the reflector is formed of a heat conductive substrate.

18. The reflector of claim 11 wherein the window includes a far IR filter.

19. The reflector of claim 11 further comprising a light source from the group consisting of mercury-arc, xenon-arc, metal halide, and halogen.

20. The reflector of claim 11 wherein the optical coating on the window is formed of a stack of thin film dielectric layers.

21. A reflector, comprising:

a means for forming an optical cavity and including a means for convectively removing heat;

means for reflecting a set of desired wavelengths while absorbing at least partially a set of undesired wavelengths and converting the undesired wavelengths to heat; and

means for transmitting the set of desired wavelengths from the means for reflecting and including means for reflecting substantially the set of undesired wavelengths back to the means for reflecting.

22. The reflector of claim 21 wherein the means for transmitting includes a means for transmitting as set of short-wavelengths in optical series with a means for transmitting s set of long-wavelengths.

23. The reflector of claim 21 further including means for generating the set of desired wavelengths and the set of undesired wavelengths disposed in the optical cavity.

24. A projection system, comprising:

a cool light source having,

an electromagnetic radiator capable of creating a set of desired wavelengths and a set of undesired wavelengths,

a reflector having a reflective coating configured to reflect substantially the set of desired wavelengths and at least partially absorb the set of undesired wavelengths, and

a window having a set of dielectric coatings configured to transmit substantially the set of desired wavelengths and reflect substantially the set of undesired wavelengths back to the reflective coating; and

a light modulator assembly optically coupled to the cool light source.

25. The projection system of claim 24 wherein the electromagnetic radiator is an arc light source.

26. The projection system of claim 24 wherein the reflective coating on the reflector includes a reflective layer of dielectric coating disposed over an absorptive layer.

27. The projection system of claim 24 wherein the set of dielectric coatings on the window are configured to include a short-wave pass filter in optical series with a long-wave pass filter.

28. The projection system of claim 27 wherein the short-wave pass filter and the long-wave pass filter are on opposing sides of the window.

29. The projection system of claim 27 wherein the short-wave pass filter and the long-wave pass filter on are on the same side of the window.

30. The projection system of claim 27 wherein the short-wave pass filter and the long-wave pass filter are optically decoupled from each other.

31. A method of making a cool light source, comprising:

creating a set of desired wavelengths and a set of undesired wavelengths of electromagnetic radiation;

reflecting substantially the set of desired wavelengths, absorbing at least partially the set of undesired wavelengths, and reflecting any remaining set of the undesired wavelengths off of a first reflective surface; and

reflecting substantially the set of undesired wavelengths with a second reflective surface back to the first reflective surface and transmitting the set of desired wavelengths through the second reflective surface.

32. The method of claim 31 wherein reflecting substantially the set of undesired wavelengths with a second reflective surface includes reflecting a first subset of the set of undesired wavelengths with a short-wave pass filter and reflecting a second subset of the set of undesired wavelengths with a long-wave pass filter.

33. The method of claim 31 further comprising converting the absorbed undesired set of wavelengths to heat and convectively radiating the heat from the cool light source.

34. The method of making a cool light source, comprising:

creating a reflector cavity within a heat conducting substrate;

applying an absorptive coating on the reflector cavity;

applying a first reflective coating on the absorptive coating that reflects a first set of wavelengths and transmits a second set of wavelengths;

applying a second reflective coating on a window that transmits the first set of wavelengths and reflects the second set of wavelengths to create a reflector window; and

applying the reflector window to at least partially enclose the reflector cavity.

35. The method of claim 34 wherein applying the second reflective coating on a window includes applying a first set of dielectric coatings that transmit the first set of wavelengths and reflects a first subset of the second set of wavelengths and applying a second set of dielectric coatings that transmit the first set of wavelengths and reflects a second subset of the second set of wavelengths.

36. The method of claim 35 wherein applying the second reflective coating on a window includes applying a third set of dielectric coatings that transmit the first set of wavelengths and reflects a third subset of the second set of wavelengths.