IMPROVEMENTS IN AND RELATING TO WAVEGUIDES

• US 20160320536A1
• Filed: 12/12/2014
• Published: 11/03/2016
• Est. Priority Date: 12/19/2013
• Status: Active Grant

• Current Assignee: BAE Systems Plc
• Original Assignee: BAE Systems Plc
• Inventors: FERNS, ANTHONY ROBERT, SIMMONDS, MICHAEL DAVID
• Granted Patent: US 9,874,667 B2
• Time in Patent Office: Days
• 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 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 5/1823 in an overlapping or superposed manner
• CPC Class Codes: G02B 6/0016 Grooves, prisms, gratings, scattering particles or rough surfaces
• CPC Class Codes: G02B 6/0035 provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/34 utilising prism or grating G02B6/293 takes precedence

Abstract

A waveguide for a display apparatus comprising a planar optical waveguide part (20) for guiding light to be displayed, an input diffraction grating (21) to diffract received light (7) along the optical waveguide part for guiding thereby, an intermediate diffraction grating (22) to receive diffracted light from the input diffraction grating and to expand the received light in a first dimension by diffraction (8), and an output diffraction grating (23) to receive the expanded light and to output the received expanded light (10) from the optical waveguide part by diffraction for display. The input diffraction grating is positioned so as to be located wholly within the geographical area of the intermediate grating, and the grating vectors of the input diffraction grating and the intermediate diffraction grating are oriented in different respective directions.

Claims

1. A waveguide for a display apparatus comprising:

a planar optical waveguide part for guiding light to be displayed;

an input diffraction grating arranged to receive light and diffract the received light along the optical waveguide part for guiding thereby;

an intermediate diffraction grating optically coupled to the input diffraction grating via the optical waveguide part and arranged to receive diffracted light from the input diffraction grating and to expand the received light in a first dimension by diffraction; and

an output diffraction grating optically coupled to the intermediate diffraction grating via the optical waveguide part and arranged to receive the expanded light and to output the received expanded light from the optical waveguide part by diffraction for display,

wherein the input diffraction grating is positioned so as to be located wholly within the geographical area of the intermediate grating, and wherein the grating vectors of the input diffraction grating and the intermediate diffraction grating are oriented in different respective directions.

2. The waveguide according to claim 1, in which the input diffraction grating is positioned substantially in-plane with the intermediate diffraction grating such that the physical location of the input diffraction grating is wholly within the geographical area of the intermediate diffraction grating.

3. The waveguide according to claim 1, in which the input diffraction grating is positioned adjacent to the intermediate diffraction grating such that the apparent location of the input diffraction grating is wholly within the geographical area of the intermediate diffraction grating.

4. The waveguide according to claim 1, in which the material of the intermediate diffraction grating covers all of the surface of the optical waveguide part at one side thereof via which said received light is guided by total internal reflection from the input diffraction grating to the intermediate diffraction grating.

5. The waveguide according to claim 1, in which the material of the intermediate diffraction grating is continuous with the material of at least the input diffraction grating.

6. The waveguide according to claim 1, in which the material of the intermediate diffraction grating is continuous with the material of the output diffraction grating.

7. The waveguide according to claim 1, in which the intermediate diffraction grating is a surface relief grating formed in a surface of the waveguide.

8. The waveguide according to claim 1, in which the input diffraction grating and the output diffraction grating are each a relief grating formed in a surface of the waveguide.

9. The waveguide according to claim 4, in which and the intermediate diffraction grating comprises a square-wave grating structure.

10. The waveguide according to claim 5, in which at least one of the input grating and the output grating comprises a blazed grating structure.

11. The waveguide according to claim 1, including a coating upon the intermediate diffraction grating, the coating having a refractive index which differs from the refractive index of the material of the intermediate diffraction grating.

12. The waveguide according to claim 1, including a coating upon at least one of the input diffraction grating and the output diffraction grating, the coating having a refractive index which differs from the refractive index of the material of at least one of the input diffraction grating and the output diffraction grating.

13. The waveguide according to claim 1, in which the output diffraction grating is arranged to receive said expanded light from the intermediate diffraction grating and to expand the received light in a second dimension transverse to said first dimension.

14. A display device comprising the waveguide of claim 1.

16. A helmet-mountable head-up display device comprising the waveguide of claim 1.

17. A vehicle display device comprising the waveguide of claim 1.

15. (canceled)

18. A waveguide for a display apparatus comprising:

a planar optical waveguide part for guiding light to be displayed;

an input diffraction grating arranged to receive light and diffract the received light along the optical waveguide part for guiding thereby;

an intermediate diffraction grating optically coupled to the input diffraction grating via the optical waveguide part and arranged to receive diffracted light from the input diffraction grating and to expand the received light in a first dimension by diffraction; and

an output diffraction grating optically coupled to the intermediate diffraction grating via the optical waveguide part and arranged to receive and expand the received light in a second dimension transverse to said first dimension, and to output the received expanded light from the optical waveguide part by diffraction for display;

wherein the input diffraction grating is positioned relative to the intermediate diffraction grating such that at least one of the apparent location and the physical location of the input diffraction grating is wholly within the geographical area of the intermediate diffraction grating.

19. The waveguide according to claim 18, wherein the grating vectors of the input diffraction grating and the intermediate diffraction grating are oriented in different respective directions.

20. The waveguide according to claim 18, in which the material of the intermediate diffraction grating covers all of the surface of the optical waveguide part at one side thereof via which said received light is guided by total internal reflection from the input diffraction grating to the intermediate diffraction grating.

21. The waveguide according to claim 18, including a coating upon at least one of the input diffraction grating and the output diffraction grating, the coating having a refractive index which differs from the refractive index of the material of at least one of the input diffraction grating, the intermediate diffraction grating, and the output diffraction grating.