Waveguides

• US 9,465,213 B2
• Filed: 12/10/2009
• Issued: 10/11/2016
• Est. Priority Date: 12/12/2008
• Status: Active Grant

• Current Assignee: BAE Systems Plc
• Original Assignee: BAE Systems Plc
• Inventors: Simmonds, Michael David
• Primary Examiner(s): Whitesell Gordon, Steven H
• Assistant Examiner(s): BROOKS, JERRY L.
• Application Number:
  US13/133,117
• Publication Number:
  US 20110235179A1
• Time in Patent Office: 2,497 Days
• Field of Search: 353/33, 359/567, 359/630, 385/27
• US Class Current: 1/1
• CPC Class Codes: G02B 2027/0125 Field-of-view increase by wavefront division
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/0103 comprising holographic elements
• 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 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/34 utilising prism or grating G02B6/293 takes precedence
• CPC Class Codes: G02B 6/4298 coupling with non-coherent light sources and/or radiation detectors, e.g. lamps, incandescent bulbs, scintillation chambers

Abstract

An image-providing light source device 58 is arranged to inject a non-coherent and collimated image into waveguide element 60. Light forming the image is dispersed by an optical element 76 so as to occupy a continuum of angles within the waveguide 60. The optical element 76 and a grating 70 are arranged such that the light exiting the waveguide occupies a single angle. Thereby, pupil banding of light exiting the waveguide 60 is mitigated.

Claims

1. A projection display, for displaying an image to an observer, including:

a first waveguide element arranged to be light transmissive;

an image-providing light source device arranged to generate an image and to inject image bearing light into the first waveguide element;

a first grating associated with the first waveguide element arranged to direct the image bearing light internally along the first waveguide element under total internal reflection and via which the image bearing light is outputted from the first waveguide element;

a second waveguide element arranged to be light transmissive and transparent that includes a second grating arranged to receive the image bearing light from the first waveguide element and to direct the image bearing light along the second waveguide element under total internal reflection;

the second waveguide element further includes a third grating arranged to diffract received image bearing light out of the second waveguide element towards an observer; and

wherein an optical element associated with each waveguide element is arranged to receive and disperse a discrete point of image bearing light incident upon the optical element at a single first angle over a continuum of second angles within the respective first and second waveguide elements.

2. A projection display, as claimed in claim 1, wherein the image-providing light source-device is arranged to generate collimated and incoherent image bearing light.

3. A projection display, as claimed in claim 1, wherein each optical element and its associated grating within each waveguide element are arranged such that a portion of the dispersed discrete point of image bearing light exits the respective waveguide element at the single first angle.

4. A projection display, as claimed in claim 1, wherein the continuum of second angles is bounded by a range of angles between a critical angle for total internal reflection of image bearing light within the first and/or second waveguide element and a suitable number of interactions between the image bearing light and the first and/or third grating.

5. A projection display, as claimed claim 1, wherein the first and third gratings are arranged to diffract a portion of image bearing light incident thereon out of the associated waveguide and to allow a remainder of the image bearing light to be transmitted within the associated waveguide under total internal reflection.

6. A projection display, as claimed in claim 1, wherein one or more of the gratings are holographic optical elements.

7. A projection display, as claimed claim 1, wherein the first waveguide element is plate-like, the second waveguide element is plate-like and the first and second waveguide elements are arranged substantially parallel to one another.

8. A projection display, as claimed in claim 1, wherein the first waveguide element and the second waveguide element are arranged substantially in the same plane.

9. A projection display, as claimed in claim 8, wherein the first waveguide element and the second waveguide element are formed within a single piece of material.

10. A projection display, as claimed in claim 1, wherein the first waveguide element is rod-like, the second waveguide element is plate-like and the first and second waveguide elements are arranged such the image bearing light exits the first waveguide element along a longitudinal axis of the first waveguide element and enters the second waveguide element to propagate along a propagation axis of the second waveguide element.

11. A Head Up Display, or Helmet Mounted Display, or Head Mounted Display including a projection display as claimed in claim 1.