Display illumination light guide

• US 8,913,324 B2
• Filed: 08/07/2012
• Issued: 12/16/2014
• Est. Priority Date: 08/07/2012
• Status: Active Grant

• Current Assignee: Magic Leap, Inc.
• Original Assignee: Nokia Corporation
• Inventors: Schrader, Martin
• Primary Examiner(s): Jones, James
• Application Number:
  US13/568,599
• Publication Number:
  US 20140043688A1
• Time in Patent Office: 861 Days
• Field of Search: 359/630
• US Class Current: 359/630
• CPC Class Codes: G02B 2027/0112 comprising device for genereting colour display
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer

Abstract

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.

Claims

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.