Display illumination light guide
View Patent ↗A near-eye display device has a multi-color light source, a micro display, an optical system and a light guide. The optical system collimates and redirects light from the micro display to an optical axis of the device. The light guide comprises multiple color-specific layers, an in-coupling diffraction grating through which light from the source enters the light guide, and an out-coupling diffraction grating through which light from the light guide exits towards the micro display. Two distinct embodiments are detailed: each different color-specific layer of the light guide is defined by a different refractive index; or by a different color-specific filter. In one example there is one in-coupling diffraction grating through which all light from the source enters the light guide; in another there are at least first and second in-coupling diffraction gratings on opposed light guide surfaces through which different colors enter the light guide.
1. An apparatus comprising:
a multi-color light source;
a micro display;
an optical system for collimating and redirecting light reflected from the micro display to an optical axis defined by a near-eye display device; and
a light guide, said light guide conducting light from said multi-color light source to said micro display, said light guide having a plurality of stacked color-specific layers, an in-coupling diffraction grating through which light from the multi-color light source enters the light guide, and an out-coupling diffraction grating through which light from the light guide exits towards the micro display.
2. The apparatus according to claim 1 , wherein each different color-specific layer of the light guide is defined by a different refractive index.
3. The apparatus according to claim 1 , wherein each different color-specific layer of the light guide is defined by a different color-specific filter.
4. The apparatus according to claim 1 , wherein the light guide has only one in-coupling diffraction grating through which all multi-color light from the light source enters the light guide.
5. The apparatus according to claim 4 , wherein the one in-coupling diffraction grating is disposed along a same surface of the light guide as the out-coupling diffraction grating.
6. The apparatus according to claim 1 , wherein the multi-color light source comprises red, green and blue light emitting diodes, and is disposed adjacent to the micro display opposite the optical system.
7. The apparatus according to claim 1 , wherein the multi-color light source outputs N distinct colors and the light guide has N stacked color-specific layers, where N is an integer greater than two.
8. The apparatus according to claim 1 , wherein the light guide has at least a first in-coupling diffraction grating disposed along a first surface of the light guide and at least a second in-coupling diffraction grating disposed along an opposed second surface of the light guide, in which different colors from the multi-color light source enter the light guide at different ones of the at least one first and second in-coupling diffraction gratings.
9. The apparatus according to claim 8 , wherein the multi-color light source outputs N distinct colors, and the light guide has N-x stacked color-specific layers and x color-specific layers adjacent to the N-x stacked color-specific layers, where N is an integer greater than 2 and x is an integer less than N.
10. The apparatus according to claim 1 , wherein:
the near-eye display device comprises a head-mountable eyeglass device;
the optical axis lies along a line of sight of a user of the head-mountable eyeglass device;
the optical system comprises lenses and at least one beam splitter; and
the multi-color light source and the micro display are disposed above the optical axis when the head-mountable eyeglass device is in a position as worn by the user.
11. A method comprising:
providing a multi-color light source, a micro display, and an optical system for collimating and redirecting light reflected from the micro display to an optical axis defined by a near-eye display device; and
illuminating the micro display with the multi-color light source via a light guide, said light guide conducting light from said multi-color light source to said micro display, said light guide having a plurality of stacked color-specific layers, an in-coupling diffraction grating through which light from the multi-color light source enters the light guide, and an out-coupling diffraction grating through which light from the light guide exits towards the micro display.
12. The method according to claim 11 , wherein each different color-specific layer of the light guide is defined by a different refractive index.
13. The method according to claim 11 , wherein each different color-specific layer of the light guide is defined by a different color-specific filter.
14. The method according to claim 11 , wherein the light guide has only one in-coupling diffraction grating through which all multi-color light from the light source enters the light guide.
15. The method according to claim 14 , wherein the one in-coupling diffraction grating is disposed along a same surface of the light guide as the out-coupling diffraction grating.
16. The method according to claim 11 , wherein the multi-color light source comprises red, green and blue light emitting diodes, and is disposed adjacent to the micro display opposite the optical system.
17. The method according to claim 11 , wherein the multi-color light source outputs N distinct colors and the light guide has N stacked color-specific layers, where N is an integer greater than two.
18. The method according to claim 11 , wherein the light guide has at least a first in-coupling diffraction grating disposed along a first surface of the light guide and at least a second in-coupling diffraction grating disposed along an opposed second surface of the light guide, and
wherein illuminating the micro display with the multi-color light source via the light guide comprises directing different colors from the multi-color light source into the light guide at different ones of the at least one first and second in-coupling diffraction gratings.
19. The method according to claim 18 , wherein the multi-color light source outputs N distinct colors, and the light guide has N-x stacked color-specific layers and x color-specific layers adjacent to the N-x stacked color-specific layers, where N is an integer greater than 2 and x is an integer less than N.
20. The method according to claim 11 , wherein:
the near-eye display device comprises a head-mountable eyeglass device;
the optical axis lies along a line of sight of a user of the head-mountable eyeglass device;
the optical system comprises lenses and at least one beam splitter; and
the multi-color light source and the micro display are disposed above the optical axis when the head-mountable eyeglass device is in a position as worn by the user.