Flat-panel display using tapered waveguide

• US 20040196665A1
• Filed: 02/02/2004
• Published: 10/07/2004
• Est. Priority Date: 08/02/2001
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Cambridge Flat Projection Displays Limited (Microsoft Corporation)
• Inventors: Travis, Adrian Roger Leigh
• Granted Patent: US 7,410,286 B2
• Time in Patent Office: Days
• US Class Current: 362/558
• 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 tapered-waveguide display apparatus includes an input waveguide (2) in the form of a slab, into one end of which light can be injected from a projector (6) so that it bounces along the waveguide and exits at the other end, and a tapered output waveguide (1) adapted to receive light from the input waveguide at its blunt end, that then bounces at ever steeper angles until it reaches the critical angle, at which point it is emitted from the face of the taper. In order to eliminate dark gaps in the display the tapered waveguide'"'"'s thickness profile is varied so that light bounces the same number of times in total before leaving the tapered waveguide.

Claims

1. A tapered-waveguide optical apparatus including an input waveguide in the form of a slab, into one end of which light can be injected so that it bounces along the waveguide and exits at the other end, and an output waveguide adapted to receive light from the input waveguide at an input end of the output waveguide to allow it to propagate a certain distance by reflection within the waveguide 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, 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 expansion 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.

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

9. A method of manufacturing a tapered-waveguide optical apparatus, including an input waveguide in the form of a slab, into one end of which light can be injected so that it bounces along the waveguide and exits at the other end, and an output waveguide adapted to receive light from the input waveguide at its thick end to allow it to propagate a certain distance and then to emit it over its face when the angle within the taper exceeds the critical angle, in which starting with the maximum number of bounces within the input waveguide the thickness of the output waveguide is calculated 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 one end of which light can be injected so that it bounces along the waveguide and exits at the other end, and an output waveguide adapted to receive light from the input waveguide at an input end of the output waveguide to allow it to propagate a certain distance by reflection within the waveguide 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, passing through the two waveguides, before leaving the output waveguide, further including;

a collimating element directing the light between the expansion 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.