Waveguide display

• US 20020008854A1
• Filed: 03/20/2001
• Published: 01/24/2002
• Est. Priority Date: 03/20/2000
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Cambridge Flat Projection Displays Limited (Microsoft Corporation)
• Inventors: Leigh Travis, Adrian Robert
• Granted Patent: US 6,608,961 B2
• Time in Patent Office: Days
• US Class Current: 353/69
• CPC Class Codes: C03B 18/04 Changing or regulating the dimensions of the molten glass ribbon
• CPC Class Codes: G02B 6/0001 specially adapted for lighting devices or systems lighting or signalling on vehicles using light guides B60Q1/00; lighting devices for vehicle dashboards B60Q3/10; lighting devices for vehicle interior using light guides B60Q3/62; lighting devices mounted on the vehicle rear part using light guides F21S43/235; measuring arrangements having light conducting pointers G01D13/265; illumination of liquid crystal displays G02F1/1336; illuminated signs G09F13/00
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/003 Lens or lenticular sheet or layer
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: H04N 5/7408 Direct viewing projectors, e.g. an image displayed on a video CRT or LCD display being projected on a screen
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells
• CPC Class Codes: H04N 9/12 Picture reproducers H04N9/11 takes precedence
• CPC Class Codes: H04N 9/31 Projection devices for colour picture display , e.g. using electronic spatial light modulators [ESLM]
• CPC Class Codes: H04N 9/3141 Constructional details thereof details not peculiar to the presence of an electronic spatial light modulator G03B21/14

Abstract

An optical waveguide system includes a generally planar waveguide 1 arranged so that light can be injected by a projector 2 into one edge at a range of out-of-plane angles. The waveguide 1 is tapered so that different out-of-plane angles, after being totally internally reflected for a certain distance, leave the waveguide at different respective points along the waveguide. This expands the image in the direction of propagation along the waveguide. Meanwhile the image is expanded transversely by a parallel-sided input waveguide 3. A large-area flat-panel display is thus created, or the planar waveguide can be used as a planar collimating light source or, using layers of controllable optical index, an optical switch.

Claims

1. An optical system including a generally planar waveguide having an input edge and a planar extent along which light can propagate by total internal reflection away from the edge, and a source of modulated light arranged to inject light rays into the input edge at a range of out-of-plane angles, the waveguide being constituted as a light-ejecting waveguide such that rays entering at different out-of-plane angles leave the ejecting waveguide, instead of being totally internally reflected, at different respective points along the direction of propagation in the waveguide.

2. An optical system according to claim 1, in which the waveguide is tapered so as to narrow along its direction of propagation.

3. An optical system according to claim 1 and further including an anti-reflection coating on one face of the waveguide.

4. An optical system according to claim 3 and further including means for re-directing the light leaving the waveguide towards the normal to the plane of the waveguide.

5. An optical system according to claim 1 and further including an input waveguide arranged to direct light input from the source so that it is injected substantially over the whole of the said input edge of the ejecting waveguide.

6. An optical system according to claim 5, in which the input waveguide is itself a planar or slab waveguide with an input edge, arranged to spread light originating from a point on the input edge within the plane, while preserving its out-of-plane angle, so as to inject the light into the said edge of the ejecting waveguide.

7. An optical system according to claim 6, and further including means for coupling the light from the input waveguide into the said input edge of the ejecting waveguide.

8. An optical system according to claim 6, in which the light source is a projector arranged to inject modulated light at various out-of-plane angles into the input waveguide.

9. A system according to claim 8 and having a plurality of projectors arranged along the input edge of the input waveguide.

10. A system according to claim 9 and being a display.

11. A system according to claim 10, in which each of the projectors inputs a different image in such a way that a 3-D display is formed.

12. An optical system according to claim 6 and further including an optical diverter conserving in-plane and out-of-plane angle and allowing the two planar waveguides to be folded over each other.

13. An optical system according to claim 5, in which the input waveguide is essentially one-dimensional and is arranged along the said input edge of the ejecting waveguide, the input waveguide being constituted in such a way that rays of different out-of-line angles injected into its one end will leave it at different points along its length, thereupon to be injected into the planar waveguide.

14. An optical system according to claim 13, in which the light source is a projector arranged to inject modulated light into the linear waveguide.

15. An optical system according to claim 14, in which the projector is arranged to inject light at various out-of-line angles into the linear waveguide.

16. An optical modulating device including:

a generally planar waveguide having an input edge and a planar extent along which light can propagate by total internal reflection way from the edge, the waveguide being constituted as a light-ejecting waveguide such that rays entering at different out-of-plane angles leave the waveguide, instead of being totally internally reflected, at different respective points along the waveguide,

an input waveguide that is essentially one-dimensional and is arranged along the said input edge of the ejecting waveguide, in order to direct light input from a source substantially over the whole of the said input edge of the ejecting waveguide, and

a source of modulated light arranged to inject light rays into the input waveguide;

each waveguide further including an addressable part arranged to alter the position at which light leaves the respective waveguide, the source being adapted to input light into the input waveguide at a single angle and ray collection devices such as optical fibers being arranged to collect the ray emitted from the planar ejecting waveguide as the points of emission are varied.

17. A planar light source comprising a light source narrower than the width of the planar source, an input slab waveguide arranged to receive the light in one edge and to expand it to the width of the source as it travels across the slab, and an ejecting waveguide arranged in its turn to receive at an edge the expanded light emitted from the input waveguide and to redirect it out of the plane of the ejecting waveguide.

18. A generally planar sheet-like optical waveguide having an input end and an output end and being formed with a selectively varying thickness so as to divert the course of a wave front propagating in the plane of the waveguide.

19. A waveguide according to claim 18, in which the thickness varies across the width of the waveguide.

20. A waveguide according to claim 19, in which the thickness varies in such a way as to convert a circular wavefront into a straight-line wavefront.

21. A method of making a tapered glass sheet by a float-glass process, in which a tapered surface is created on the metal bath by electromagnetic attraction from one side of the bath.

22. A projection display comprising an image projector, a generally planar waveguide having an input edge, and a screen, the display being arranged so that an image is projected from the projector into the input edge, travels through the plane of the waveguide and is then transferred from the waveguide to the screen.

23. A projection display according to claim 22, in which the waveguide is a slab of uniform thickness much wider than that part of the projector from which the image emerges, and is arranged to allow transverse expansion of the projected image before its transfer to the screen.