Achromatic flat-panel display

• US 6,883,919 B2
• Filed: 11/26/2001
• Issued: 04/26/2005
• Est. Priority Date: 11/25/2000
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Cambridge Flat Projection Displays Limited
• Inventors: Travis, Adrian Robert Leigh
• Primary Examiner(s): Dowling, William C.
• Application Number:
  US10/432,130
• Publication Number:
  US 20040070737A1
• Time in Patent Office: 1,247 Days
• Field of Search: 353/22, 353/38, 353/69, 353/79, 353/81, 353/122, 385/901, 359/443, 359/453
• US Class Current: 353/81
• CPC Class Codes: G02B 6/08 with fibre bundle in form of plate
• CPC Class Codes: G03B 21/10 Projectors with built-in or built-on screen
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor
• 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: Y10S 385/901 Illuminating or display apparatus

Abstract

An achromatic flat-panel projection display comprises a video projector 2a, a condensing lens (26) and a tapered transparent slab spreading the image input from the projector over the area of th slab. To compensate for dispersion in the slab a dispersive prism is used at the input edge of the slab, whose dispersion cancels out the dispersion of the slab. The prism can be a separate part of simply a bevel in the input edge, i.e. the thick end of the slab.

Claims

1. An achromatic flat-panel projection display comprising an image projector for projecting an image to be displayed, and a tapered transparent slab into the thick end of which the image is projected so that the rays emerge over one face of the slab, the slab being made of a dispersive material;

further comprising a dispersive prism between the projector and the slab, compensating for the dispersion occurring in the slab.

2. A display according to claim 1, in which the prism is a separate component.

3. A display according to claim 2, in which the prism is made of the same material as the slab.

4. A display according to claim 1, in which the prism is integral with the slab so that the input edge is bevelled.

5. A display according to claim 1, in which the angle β

of the prism satisfies $\frac{\sin <br><br>\left({\mathrm{\theta <br><br>}}_1+\mathrm{\beta <br><br>}\right)}{\tan <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\beta <br><br>}}=\sqrt{n_0^2-{\sin }^2<br><br>\left({\mathrm{\theta <br><br>}}_1+\mathrm{\beta <br><br>}\right)}-\frac{\left(n_0^2-1\right)}{\sqrt{n_0^2-{\sin }^2<br><br>\left({\mathrm{\theta <br><br>}}_1+\mathrm{\beta <br><br>}\right)}}$

where θ

₁ is the angle of input in air relative to the plane of the slab, and n₀ is the average refractive index of the material of the slab over the range of wavelengths input from the projector.