Apparatus for condensing light from multiple sources using Bragg gratings
A color sequential illumination device including in series: first and second light sources; a condenser lens; and a grating device. The grating device includes at least one Bragg grating. The condenser lens directs light from the first and second sources into the grating device at first and second incidence angles respectively. The grating device diffracts light from the first and second sources into a common direction. Desirably, the Bragg gratings are Electrically Switchable Bragg Gratings. In one embodiment the light sources are Light Emitting Diodes. Alternatively lasers may be used.
1. An illumination device comprising;
a first and a second light source wherein the light from the first light source and the second light source are pulsed out of phase;
a condenser lens in series with the first and the second light sources wherein the condenser lens directs light from the first light source and the second light source into a light input port at a first and a second incidence angle respectively; and
a grating device in series with the condenser lens, wherein the grating device comprises at least one Bragg grating, the light input port and a light output port and the grating device is operative to diffract light from the first light source and the second light source out of the light output port in a common direction.
2. The illumination device of claim 1 wherein the first light source has a first wavelength and the second light source has a second wavelength.
3. The illumination device of claim 1 wherein the first light source and the second light source have substantially identical wavelengths.
4. The illumination device of claim 1 wherein said grating device comprises first and second Bragg gratings operative to diffract light from said first and second sources respectively.
5. The illumination device of claim 1 wherein said grating device comprises a Bragg grating operative to diffract light from said first source and light from said second source.
6. The illumination device of claim 1 further comprising a third light source, wherein said condenser lens directs light from said third source into said input port at a third incidence angle, wherein light from said third source is not diffracted by said grating device.
7. The illumination device of claim 1 wherein said Bragg grating is an Electrically Switchable Bragg Grating.
8. The illumination device of claim 1 wherein the first light source and the second light sources are Light Emitting Diodes.
9. The illumination device of claim 1 wherein the first light source and the second light sources are lasers.
10. The illumination device of claim 1 wherein the first light source and the second light sources are disposed on a curved surface.
11. The illumination device of claim 1 wherein beam shaping optical elements are disposed between each said sources and said condenser lens.
12. The illumination device of claim 1 wherein said condenser lens is a multi element lens system.
13. The illumination device of claim 1 further comprising a beam shaping diffractive optical element.
14. The illumination device of claim 1 further comprising a relay lens disposed after said grating device.
15. The illumination device of claim 1 wherein said condenser lens functions as a collimator.
16. The illumination device of claim 1 wherein light emerging from said output port forms an illumination patch.
17. The illumination device of claim 1 further comprising a dichroie Beamsplitter disposed in the optical path between said first light source and said grating device.
18. The illumination device of claim 17 wherein said illumination patch is used to illuminate a microdisplay.
19. The illumination device of claim 1 further comprising a third light source, wherein said condenser lens directs light from said third source into said input port at a third incidence angle, wherein said grating device comprises first, second and third Bragg gratings operative to diffract light from said first, second and third light sources respectively into said common direction.
20. The illumination device of claim 19 wherein said first, second and third light sources provide red, green and blue light respectively.
21. The illumination device of claim 19 further comprising a fourth light source, wherein said condenser lens directs light from said fourth source into said input port at a fourth incidence angle, wherein said grating device comprises first, second, third and fourth Bragg gratings operative to diffract light from said first, second, third and fourth light sources respectively into said common direction.
22. The illumination device of claim 19 wherein said first and second sources have substantially identical wavelengths.
23. The illumination device of claim 19 wherein said Bragg grating is an Electrically Switchable Bragg Grating.
24. The illumination device of claim 19 wherein said sources are Light Emitting Diodes.
25. The illumination device of claim 19 wherein said sources are lasers.