FLAT-PANEL OPTICAL PROJECTION APPARATUS

• US 20120207434A1
• Filed: 04/16/2012
• Published: 08/16/2012
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Large, Timothy
• Granted Patent: US 8,422,840 B2
• Time in Patent Office: Days
• US Class Current: 385/36
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066
• CPC Class Codes: G03B 21/62 Translucent screens
• CPC Class Codes: H04N 9/3141 Constructional details thereof details not peculiar to the presence of an electronic spatial light modulator G03B21/14
• CPC Class Codes: H04W 72/30 Resource management for broadcast services

Abstract

A light guide of the tapered-waveguide type includes an input slab for expanding a projected image between an input end and an output end, and an output slab arranged to receive rays from the said output end, and to emit them at a point on its face that corresponds to the angle at which the ray is received. The input slab and output waveguide are matched so that all rays injected into the input end undergo the same number of reflections before leaving the output surface. With the invention, the input slab is itself tapered slightly towards the output waveguide. This means that input and output waveguides can be made the same length, in the direction of ray travel, and can therefore be folded over each other with no wasted space.

Claims

1. A light guide comprising:

an input slab; and

an output waveguide to receive rays from the input slab, and to emit the rays through an output face, wherein a thickness of the input slab tapers at a constant first angle in a direction of ray travel and a thickness of the output waveguide tapers at a second angle that is different from the first angle.

2. A light guide according to claim 1, in which the first angle and the second angle are controlled so that rays of different angles travelling between an input end of the input slab and a location where the rays leave the output face undergo a same number of reflections.

3. A light guide according to claim 1, further including a prism arrangement for folding the light guide by 180°

so that the input slab and the output waveguide are arranged one on top of another.

4. A light guide according to claim 1, in which:

the input slab and the output waveguide are of substantially a same length; and

the output face tapers at the second angle to coincide with a bottom face of the output waveguide at a distal end of the output waveguide.

5. A light guide according to claim 1, further comprising a projector to inject an image into an input end of the input slab.

6. A light guide according to claim 1, further comprising a camera to receive an image from an input end of the input slab.

7. A light guide according to claim 1, in which the input slab allows a projected image to expand laterally within the input slab as light of the image travels between an input end and an output end.

8. A light guide according to claim 1, in which the constant first angle at which the input slab tapers is less than the second angle at which the output waveguide tapers.

9. A light guide according to claim 8, in which the second angle at which the output waveguide tapers increases in the direction of ray travel.

10. A light guide comprising:

an input slab having a first end and a second end, the input slab having a constant angle of taper from the first end to the second end; and

an output waveguide to receive light rays from the input slab, and emit the light rays through an output face, the output waveguide having an angle of taper in a direction of ray travel, the constant angle of taper of the input slab being different than the angle of taper of the output waveguide.

11. A light guide according to claim 10, in which the constant angle of taper of the input slab and the angle of taper of the output waveguide are controlled so that light rays of different angles travelling between the first end of the input slab and a location where the light rays leave the output face undergo a same number of reflections.

12. A light guide according to claim 10, further including a prism arrangement for folding the light guide by 180°

so that the input slab and the output waveguide are arranged one on top of another.

13. A light guide according to claim 10, in which:

the input slab and the output waveguide are of substantially a same length; and

the output face tapers to coincide with a bottom face of the output waveguide at a distal end of the output waveguide.

14. A light guide according to claim 10, further comprising a projector to inject an image into the first end of the input slab.

15. A light guide according to claim 10, in which the constant angle of taper of the input slab is less than the angle of taper of the output waveguide.

16. A light guide according to claim 15, in which the angle of taper of the output waveguide increases in the direction of ray travel.

17. An apparatus comprising:

an input slab to receive light rays at an input end, the input slab decreasing in thickness from the input end to an output end at a first angle of taper;

an output slab having an entrance end to receive the light rays from the output end of the input slab, the output slab having an output face to emit the light rays, the output slab decreasing in thickness from the entrance end at a second angle of taper different from the first angle of taper.

18. An apparatus according to claim 17, in which the first angle of taper of the input slab and the second angle of taper of the output slab are selected so that light rays entering the input end of the input slab at different angles reflect a same number of times before exiting the output face.

19. An apparatus according to claim 17, in which a length of the input slab in a direction of light travel is substantially equivalent to a length of the output slab in the direction of light travel.

20. An apparatus according to claim 17, in which the first angle of taper of the input slab is a constant first angle of taper that is less than the second angle of taper of the output slab.