Flat-panel display using tapered waveguide

• US 7,410,286 B2
• Filed: 08/01/2002
• Issued: 08/12/2008
• Est. Priority Date: 08/02/2001
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Travis, Adrian Robert Leigh
• Primary Examiner(s): CHOI, JACOB Y
• Application Number:
  US10/485,888
• Publication Number:
  US 20040196665A1
• Time in Patent Office: 2,203 Days
• Field of Search: 362/625, 362/626, 362/612, 362/616, 362/623, 362/561, 385/146, 385/116, 385/901
• US Class Current: 362/616
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• 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: Y10S 385/901 Illuminating or display apparatus

Abstract

A video display for two or three dimensions has a flat liquid-crystal screen which ejects light from the plane at a selectable line. One or, in the case of a 3-D display, several video projectors project a linear image into the plane from an edge. A complete image is written on the screen by addressing the line with appropriate images as it is scanned down the screen. To screen a three-dimensional image, the video projectors, each projecting an image as seen at a slightly different angle, combine to constitute a three-dimensional display which produces a three-dimensional image that is one line high.

Claims

1. A tapered-waveguide optical apparatus including:

an input waveguide in the form of a slab, the input waveguide comprising a first input end for injection of light such that it bounces along the input waveguide and travels to a first output end; and

an output waveguide having two opposed main faces and a second input end for receiving light at various angles of incidence from the input waveguide,

wherein the output waveguide is arranged to allow light to propagate a certain distance by reflection within the output waveguide at successively steeper angles of incidence on said opposed main faces and then to emit the light over one of the faces of the output waveguide when the angle of incidence at that one face exceeds the critical angle for total internal reflection;

in which the output waveguide'"'"'s thickness profile is such that the light of different angles of incidence at said second input end bounces the same number of times in total, on passing through the two waveguides, before leaving the output waveguide.

2. An optical apparatus according to claim 1, in which the input waveguide is a flat rectangular cuboid.

3. An optical apparatus according to claim 1, in which the two waveguides are made of the same material.

4. An optical apparatus according to claim 1, further including a collimating element directing the light between the input waveguide and the output waveguide so that, resolved in the plane of the output waveguide, the light travels substantially parallel.

5. An optical apparatus according to claim 1, further including a screen over the output waveguide for spreading the emerging light to increase the viewing angle.

6. An optical apparatus according to claim 5, in which the screen comprises louvers inclined at an angle suitable for passing the emerging rays, and diffusing elements between the louvers.

7. An optical apparatus according to claim 1 and including a video projector arranged to inject an image into the input waveguide, so as to form a display.

8. An optical apparatus according to claim 1 and including an effective point source of light, the apparatus thus acting as a planar light source.

9. An optical apparatus according to claim 1, in which the input and output waveguides are folded so that one lies over the other.

10. A method of manufacturing a tapered-waveguide optical apparatus, the optical apparatus comprising an input waveguide in the form of a slab, the input waveguide comprising an input end for injection of light such that the light bounces along the input waveguide and travels to a first output end;

and an output waveguide having two opposed main faces and a second input end for receiving light at various angles of incidence from the input waveguide, wherein the output waveguide is arranged to allow light to propagate a certain distance by reflection within the output waveguide at successively steeper angles of incidence on said opposed main faces and then to emit the light over a face when the angle of incidence at that face exceeds the critical angle for total internal reflection;

in which the method comprises the follow steps;

starting with the maximum number of bounces within the input waveguide, calculating the thickness of the output waveguide for each decrement of one double bounce in the input waveguide;

calculating the corresponding distance from the thick end of the taper to ensure that the light undergoes one extra double bounce in the output waveguide, thus ensuring that the total number of bounces is kept constant;

repeating the calculations of the thickness and distance from the thick end of the output waveguide for each decrement of one double bounce in the input waveguide until the thickness reaches a lower limit and the output waveguide, or a mould for it, is shaped accordingly.

11. A tapered-waveguide optical apparatus including:

an input waveguide in the form of a slab, into a first input end of which light is injectable so that light bounces along the waveguide and exits at a first output end; and

an output waveguide having two opposed main faces and a second input end for receiving light at various angles of incidence from the input waveguide and arranged to allow light to propagate a certain distance by reflection within the output waveguide at successively steeper angles of incidence on said opposed main faces and then to emit the light over one of the faces of the output waveguide when the angle of incidence at that face exceeds the critical angle;

in which the output waveguide'"'"'s thickness profile is such that light bounces the same number of times in total on passing through the two waveguides, before leaving the output waveguide, further including;

a collimating element directing the light between the input waveguide and the output waveguide so that, resolved in the plane of the output waveguide, the light travels substantially parallel; and

a screen over the output waveguide for spreading the emerging light to increase the viewing angle, in which the input and output waveguides are folded so that one lies over the other.