OPTICAL WAVEGUIDE AND DISPLAY DEVICE

• US 20130044376A1
• Filed: 04/19/2011
• Published: 02/21/2013
• Est. Priority Date: 04/23/2010
• Status: Active Grant

• Current Assignee: Snap, Inc.
• Original Assignee: BAE Systems Plc
• Inventors: Valera, Mohmed Salim, Simmonds, Michael David
• Granted Patent: US 9,946,068 B2
• Time in Patent Office: Days
• US Class Current: 359/567
• CPC Class Codes: G02B 2027/0112 comprising device for genereting colour display
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• 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 6/0035 provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area

Abstract

An optical method of displaying an expanded colour image comprising extracting from input light bearing said coloured image a first spectral portion and a second spectral portion such that together the two portions contain sufficient information for the image to be displayed in substantially its original colours, separately expanding the two spectral portions each in two dimensions and recombining the expanded spectral portions to display the expanded colour image.

Claims

1. An optical structure comprising first and second waveguides for receiving light input thereto bearing a colour image and displaying said colour image, comprising a first diffraction region for diffracting a first spectral portion of the input light to propagate by total internal reflection along the first waveguide, the first spectral portion comprising at least a majority of a first primary colour component of the input light, part of a second primary colour component thereof and a minority of a third primary colour component thereof and a second diffraction region for diffracting a second spectral portion of the input light to propagate by total internal reflection along the second waveguide, the second spectral portion comprising a minority of the first primary colour component, part of the second primary colour component and at least the majority of the third primary colour component such that together the two spectral portions contain sufficient information for light outputted by the structure to display the image in substantially its original colours, the first and second diffracting regions having periodic diffracting patterns of different pitch and the first diffracting region comprising at least one coating layer on the diffracting pattern, the thickness and composition of the or each layer being such that interferences between reflections of at least the first primary colour component from some of the interfaces between the layers and/or between a said layer and another medium are constructive, a first expanding means for expanding the first spectral portion in two dimensions, a second expanding means for expanding the second spectral portion in two dimensions and means for combining the expanded first and second spectral portions to display the colour image.

2. The structure of claim 1 wherein the first diffraction region and the or each coating layer is adapted to reflect the first spectral portion and to be transmissive to the second spectral portion.

3. The structure of claim 1 wherein the said coating layers on the first diffraction region comprise a layer of silicon dioxide and a layer of titanium dioxide.

4. The structure of claim 1 wherein the second diffraction region comprises a reflective layer and at least one coating layer, the thickness and composition of the or each such layer being such that interferences between reflections of at least the third primary colour component from the reflective layer and from at least one interface between the layers or between a said layer and another medium are constructive.

5. The structure of claim 4 wherein the reflective coating on the second diffraction region comprises a layer of silver and the coating layer thereon is of titanium dioxide.

6. The structure of claim 1 wherein the two expanding means are disposed relative to each other so that in operation the expanded first spectral portion passes from the first expanding means through the second expanding means, and the expanded first and second spectral portions are thereby combined as said image.

8. A display system comprising the structure of claim 1.

9. The system of claim 8, being a helmet-mounted or head-mounted display system, or a head-up display system.

7. An optical method of displaying an expanded colour image comprising inputting light bearing a colour image into a first waveguide, diffracting with a first diffraction region a first spectral portion of the input light to propagate by total internal reflection along the first waveguide and to expand in two dimensions, the first spectral portion comprising at least a majority of a first primary colour component of the input light, part of a second primary colour component thereof and a minority of a third primary colour component thereof and diffracting with a second diffraction region a second spectral portion of the input light to propagate by total internal reflection along the second waveguide and to expand in two dimensions, the second spectral portion comprising a minority of the first primary colour component, part of the second primary colour component and at least the majority of the third primary colour component, combining the expanded first and second spectral portions such that together the two spectral portions contain sufficient information for light outputted by the structure to display the image in substantially its original colours, wherein the first and second diffracting regions have periodic diffracting patterns of different pitch and the first diffracting region comprising at least one coating layer on the diffracting pattern, the thickness and composition of the or each layer being such that interferences between reflections of at least the first primary colour component from some of the interfaces between the layers and/or between a said layer and another medium are constructive.