Light coupling system and method

• US 20070052929A1
• Filed: 09/06/2005
• Published: 03/08/2007
• Est. Priority Date: 09/06/2005
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Gupta, Anurag, Lerner, Scott, Allman, Stuart
• Granted Patent: US 7,434,940 B2
• Time in Patent Office: Days
• US Class Current: 353/31
• CPC Class Codes: G02B 6/0026 Wavelength selective element, sheet or layer, e.g. filter or grating
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/29329 Diffractive elements operating in transmission
• CPC Class Codes: G02B 6/29388 for lighting or use with non-coherent light
• CPC Class Codes: H04N 9/3111 for displaying the colours sequentially, e.g. by using sequentially activated light sources sequential projection in colour photography G03B33/08
• 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 coupling system includes a waveguide, configured to receive light from at least two light sources and to internally reflect light therein; a diffraction grating, disposed upon the waveguide; and a switchable Bragg grating, disposed upon the waveguide. The diffraction grating is configured to couple light from at least one of the light sources into the waveguide, and the switchable Bragg grating is configured to selectively couple light out of the waveguide, such that the light from the at least two light sources is selectively directed along a common projection axis.

Claims

1. A light coupling system, comprising:

a substantially planar array of light sources of different colors;

a waveguide, disposed substantially parallel to the planar array, a first of the light sources being configured to project light directly through the waveguide along a projection axis;

first means for coupling light from a second of the light sources into the waveguide; and

first switchable means for selectively coupling the light of the second light source out of the waveguide and directing said light along the projection axis.

2. A light coupling system in accordance with claim 1, wherein the light sources are selected from the group consisting of lasers and light emitting diodes.

3. A light coupling system in accordance with claim 1, wherein the light sources comprise groups of light emitting diodes, each group having a common color.

4. A light coupling system in accordance with claim 1, wherein the different colors of the light sources are selected from the group consisting of red, green and blue.

5. A light coupling system in accordance with claim 1, wherein the waveguide comprises a plate of substantially constant thickness, configured to substantially totally internally reflect light therein, the plate being of a material selected from the group consisting of glass and plastic.

6. A light coupling system in accordance with claim 1, wherein the first means for coupling light from the second light source comprises a first diffraction grating, disposed upon the waveguide, and aligned with the second light source.

7. A light coupling system in accordance with claim 1, further comprising second means for coupling light from a third of the light sources into the waveguide.

8. A light coupling system in accordance with claim 7, wherein the second means for coupling light from the third light source comprises a second diffraction grating, disposed upon the waveguide, and aligned with the third light source.

9. A light coupling system in accordance with claim 1, wherein the first switchable means for selectively coupling the light of the second light source out of the waveguide comprises a first switchable Bragg grating, configured to freely allow passage of the light from the first light source, and to selectively couple the light of the second light source out of the waveguide.

10. A light coupling system in accordance with claim 1, further comprising second switchable means for selectively coupling light of a third light source out of the waveguide, and directing said light along the projection axis.

11. A light coupling system in accordance with claim 10, wherein the second switchable means for selectively coupling light of a third light source comprises a second switchable Bragg grating, configured to freely allow passage of the light from the first light source, and to selectively couple the light of the third light source out of the waveguide.

12. A light coupling system, comprising:

a substantially planar array of light sources of different colors;

a waveguide, disposed substantially parallel to the planar array, a first of the light sources being configured to project light directly through the waveguide along a projection axis;

a first diffraction grating, disposed upon the waveguide, configured to couple light from a second of the light sources into the waveguide; and

a first switchable Bragg grating, disposed upon the waveguide, configured to freely allow passage of the light from the first light source, and to selectively couple the light of the second light source out of the waveguide and direct said light along the projection axis.

13. A light coupling system in accordance with claim 12, wherein the array of light sources comprise light emitting diodes disposed upon a common substrate.

14. A light coupling system in accordance with claim 12, wherein the light sources comprise groups of light emitting diodes, each group having a common color.

15. A light coupling system in accordance with claim 12, wherein the different colors of the light sources are selected from the group consisting of red, green and blue.

16. A light coupling system in accordance with claim 12, wherein at least one of the light sources includes a laser.

17. A light coupling system in accordance with claim 12, further comprising a second diffraction grating, disposed upon the waveguide, configured to couple light from a third of the light sources into the waveguide;

and a second switchable Bragg grating, disposed upon the waveguide, configured to freely allow passage of the light from the first light source, and to selectively couple the light of the third light source out of the waveguide and direct said light along the projection axis.

18. A light coupling system, comprising:

a substantially planar array comprising three light sources of different colors;

a waveguide, disposed substantially parallel to the planar array, and positioned to allow light from a first of the light sources to project directly through the waveguide along a projection axis;

a first diffraction grating, disposed upon the waveguide, configured to couple light from a second of the light sources into the waveguide;

a second diffraction grating, disposed upon the waveguide, configured to couple light from a third of the light sources into the waveguide;

a first switchable Bragg grating, disposed upon the waveguide, configured to freely allow passage of the light from the first light source, and to selectively couple the light of the second light source out of the waveguide, and direct said light along the projection axis; and

a second switchable Bragg grating, disposed upon the waveguide, configured to freely allow passage of the light from the first light source, and to selectively couple the light of the third light source out of the waveguide, and direct said light along the projection axis.

19. A light coupling system in accordance with claim 18, wherein the three light sources comprise red, green, and blue LEDs.

20. A light coupling system in accordance with claim 18, wherein the waveguide comprises a plate of substantially constant thickness, configured to substantially totally internally reflect light therein, the plate being of a material selected from the group consisting of glass and plastic.

21. A projection system, comprising:

a light processor, configured for modulating light into an image;

projection optics, configured for projecting the image onto a viewing surface;

a light source, configured to sequentially provide light of multiple primary colors to the light processor, the light source including

a substantially planar array of lighting devices of different colors;

a waveguide, disposed substantially parallel to the planar array, and configured for internally transmitting the light from the lighting devices;

means for coupling light from the light sources into the waveguide; and

switchable means for selectively coupling the light from the light sources out of the waveguide and directing said light along a projection axis.

22. A projection system in accordance with claim 21, wherein the means for coupling light into the waveguide comprises a diffraction grating, disposed upon the waveguide.

23. A projection system in accordance with claim 21, wherein the switchable means for selectively coupling light out of the waveguide comprises a switchable Bragg grating.

24. A projection system in accordance with claim 21, wherein the lighting devices comprise red, green, and blue LEDs.

25. A method for coupling colored light from a plurality of light sources into a single light path, comprising the steps of:

projecting light of a first color from a first light source through a target location of a waveguide and along the light path;

coupling light of a second color from a second light source into the waveguide, such that the light of the second color internally reflects within the waveguide toward the target location;

coupling the light of the second color out of the waveguide at the target location so as to project along the light path.

26. A method in accordance with claim 25, wherein the step of coupling the light of the second color into the waveguide comprises diffracting said light with a diffraction grating disposed upon a surface of the waveguide

27. A method in accordance with claim 26, wherein the step of diffracting said light with a diffraction grating comprises diffracting said light by an angle greater than a critical angle of the waveguide.

28. A method in accordance with claim 25, wherein the step of coupling the light of the second color out of the waveguide comprises diffracting the internally-reflected light with a switchable Bragg grating disposed upon a surface of the waveguide at the target location.

29. A method in accordance with claim 28, further comprising the step of switching the switchable Bragg grating to an “

on”

condition only when the second light source is illuminated.

30. A method in accordance with claim 28, wherein the step of diffracting the internally-reflected light comprises diffracting the light by a diffraction angle selected to cause the light of the second color to leave the waveguide in a direction substantially parallel to the light path.

31. A light coupling system, comprising:

a waveguide, configured to receive light from at least two light sources, and to internally reflect light therein;

a diffraction grating, disposed upon the waveguide, configured to couple light from at least one of the light sources into the waveguide; and

a switchable Bragg grating, disposed upon the waveguide, configured to selectively couple light out of the waveguide, such that the light from the at least two light sources is selectively directed along a common projection axis.

32. A light coupling system in accordance with claim 31, wherein the at least two light sources include at least one of a laser and a light emitting diode.

33. A light coupling system in accordance with claim 31, wherein the at least two light sources comprise a substantially planar array disposed substantially parallel to the waveguide.