OPTICAL WAVEGUIDES

• US 20120120493A1
• Filed: 04/19/2010
• Published: 05/17/2012
• Est. Priority Date: 04/20/2009
• Status: Active Grant

• Current Assignee: BAE Systems Plc
• Original Assignee: BAE Systems Plc
• Inventors: Simmonds, Michael David, Valera, Mohmed Salim
• Granted Patent: US 10,642,039 B2
• Time in Patent Office: Days
• US Class Current: 359/566
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 5/18 Diffraction gratings holographic optical elements G02B5/32, G03H; integrally combined with optical fibres G02B6/02057; for coupling light guides G02B6/34; integrally combined with optical integrated light guides G02B6/12; grating systems G02B27/44
• CPC Class Codes: G02B 6/00 Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• CPC Class Codes: G02B 6/0026 Wavelength selective element, sheet or layer, e.g. filter or grating
• CPC Class Codes: G02B 6/0035 provided on the surface of the light guide or in the bulk of it

Abstract

The invention relates to a display device for displaying an image over a field of view. The device comprises: an optical arrangement for directing image bearing light from an image source so that the light has rays at a range of angles relative to an injection axis; and an optical waveguide having an input grating for diffracting into the waveguide said light over said range of angles such that all of the diffracted light is totally internally reflected within the waveguide and so that image bearing light output from the waveguide has a field of view corresponding to said range of angles, wherein the input grating is a surface relief grating having a profiled reflective surface and at least one layer of dielectric material conforming to the surface for diffracting light over said range of angles into the waveguide.

Claims

1. A display device for displaying an image over a field of view, comprising:

an optical arrangement for directing image bearing light from an image source so that the light has rays at a range of angles relative to an injection axis; and

an optical waveguide having an input grating for diffracting into the waveguide said light over said range of angles such that all of the diffracted light is totally internally reflected within the waveguide and so that image bearing light output from the waveguide has a field of view corresponding to said range of angles,

wherein the input grating is a surface relief grating having a profiled reflective surface and at least one layer of dielectric material conforming to the surface for diffracting light over said range of angles into the waveguide.

2. A display device as claimed in claim 1, wherein said at least one layer of dielectric material conforms to the reflecting surface, the waveguide being operable such that light passes through the dielectric material to the reflecting surface.

3. A display device as claimed in claim 1, wherein the at least one layer of dielectric material comprises one or more of titanium dioxide, silicon dioxide or magnesium oxide.

4. A display device as claimed in claim 1 wherein the thickness of the at least one dielectric layer is selected to control the angular bandwidth of the grating so that the diffraction grating can input into the waveguide image bearing light over said range of angles.

5. A display device as claimed in claim 1, comprising a profiled waveguide surface, the at least one dielectric layer being disposed on the profiled waveguide surface so as to reproduce the profile thereof, the profiled reflective surface of the grating being a surface of a layer of material disposed on the at least one dielectric layer and conforming thereto.

6. A display device as claimed in claim 1, wherein the profiled reflecting surface is a reflective surface of a substrate which is conformably coated with the at least one dielectric layer and is optically contacted to a surface of the waveguide.

7. A display device as claimed in claim 5, wherein the reflective surface is a surface of a metallic or other material having a complex refractive index.

13. A head-mounted display, a head-up display, a helmet-mounted display or other projection display apparatus according to claim 1.

8. A display device for displaying an image over a field of view, comprising:

an optical arrangement for directing image bearing light from an image source so that the light has rays at a range of angles relative to an injection axis; and

an optical waveguide comprising;

an input grating having a profiled surface and at least one layer of dielectric material conforming to the profiled surface for diffracting said light into the waveguide over said range of angles such that all of the diffracted light is totally internally reflected within the waveguide; and

an output grating having a profiled surface and at least one layer of dielectric material conforming to the profiled surface for diffracting light passing along the waveguide over said range of angles out of the waveguide for displaying an image with a field of view corresponding to said range of angles.

9. The use, for the purpose of controlling the angular bandwidth of a reflecting surface relief grating of an optical waveguide in a display device, of at least one layer of dielectric material conforming to a reflecting profiled surface of the grating, the waveguide being operable such that light over a selected angular bandwidth passes through the dielectric material to the reflecting profiled surface for diffraction by the grating.

12. A head-mounted display, a head-up display, a helmet-mounted display or other projection display apparatus comprising an optical waveguide having a grating and in which a dielectric layer is used as in claim 9.

10. The use, for the purpose of controlling the angular bandwidth of input and output gratings of an optical waveguide in a display device, of at least one layer of dielectric material conforming to each of the profiled surfaces of the gratings so that the angular bandwidth of the gratings is generally matched, the waveguide being operable such that light can be input to the waveguide over a range of angles within the angular bandwidth of the input grating and the angular bandwidth of the output grating is sufficient to output from the waveguide light over said range of angles propagating by total internal reflection within the waveguide.

11. (canceled)