Waveguides

1. A method for manufacturing a waveguide for a display apparatus, the waveguide including an input diffraction grating region to receive light and diffract the received light along the waveguide, an intermediate diffraction grating region to receive diffracted light from the input diffraction grating region and to expand the received light in a first dimension by diffraction, and an output diffraction grating region to receive and output the expanded light from the waveguide by diffraction, the method comprising:

providing a planar waveguide part;

depositing upon at least one planar surface of the planar waveguide part a fluid material curable to form an optically transparent solid;

impressing upon the fluid material an impression defining the input diffraction grating region, the intermediate diffraction grating region, and the output diffraction grating region; and

curing the impressed fluid material to solidify said impression;

wherein the input diffraction grating region is positioned wholly within a geographical area bounded by an outer periphery of the intermediate diffraction grating region, and wherein a grating vector of the input diffraction grating region and a grating vector of the intermediate diffraction grating region are oriented in different respective directions.

2. The method according to claim 1 , wherein the depositing includes depositing the fluid material upon one planar surface of the planar waveguide part such that the impression defining the intermediate diffraction grating region is formed in fluid material that is continuous with the fluid material in which is formed the impression defining at least the input diffraction grating region and such that at least the input diffraction grating region and the intermediate diffraction grating region are substantially co-planar.

3. The method according to claim 2 , wherein the impressing includes impressing upon the fluid material deposited upon the one planar surface of the planar waveguide part each of the input diffraction grating region, the intermediate diffraction grating region and the output diffraction grating region.

4. The method according to claim 1 , wherein the impressing includes impressing simultaneously upon the fluid material deposited upon one planar surface of the planar waveguide part both the input diffraction grating region and the intermediate diffraction grating region.

5. The method according to claim 1 , wherein the depositing includes depositing the fluid material upon opposite planar surfaces of the planar waveguide part, wherein the impressing includes impressing the impression defining the input diffraction grating region into the fluid material deposited upon one surface of the planar waveguide part and impressing the impression defining the intermediate diffraction grating region into the fluid material deposited upon an opposite surface of the planar waveguide part, and wherein the intermediate diffraction grating region, when viewed along a direction through the input diffraction grating region perpendicular to the surface of the planar waveguide part upon which the input diffraction grating region has been formed, appears to entirely surround the input diffraction grating region.

6. The method according to claim 5 , wherein the curing includes curing simultaneously the fluid material in which is formed the intermediate diffraction grating region and the output diffraction grating region when formed upon one planar surface of the planar waveguide part, and wherein the fluid material is applied subsequently to the opposite planar surface of the planar waveguide part, the input diffraction grating region is formed therein by impressing and the fluid material in which the input diffraction grating region is formed is cured.

7. The method according to claim 1 , wherein the fluid material in which the intermediate diffraction grating region is formed is continuous with the fluid material in which the output diffraction grating region is formed.

8. The method according to claim 1 , wherein the curing includes curing the fluid material simultaneously for each of the input diffraction grating region and the intermediate diffraction grating region or additionally the output diffraction grating region.

9. The method according to claim 8 , including adjusting the orientation of the input diffraction grating region impressed into the fluid material relative to the solidified intermediate diffraction grating region and the solidified output diffraction grating region, and subsequently curing the impressed input diffraction grating region at a chosen orientation.

10. The method according to claim 1 , wherein the impressing includes impressing the intermediate diffraction grating region with a square-wave grating structure.

11. The method according to claim 1 , wherein the impressing includes impressing at least one of the input diffraction grating region and the output diffraction grating region with a blazed grating structure.

12. The method according to claim 1 , including applying a coating upon the intermediate diffraction grating region, the coating having a refractive index which differs from a refractive index of the fluid material in which the intermediate diffraction grating region is impressed.

13. The method according to claim 1 , including applying a coating upon at least one of the input diffraction grating region and the output diffraction grating region, the coating having a refractive index which differs from at least one of a refractive index of the fluid material in which the input diffraction grating region is impressed and a refractive index of the fluid material in which the output diffraction grating region is impressed.

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

15. A waveguide for a display apparatus, the waveguide comprising:

a planar waveguide part including at least one planar surface, the at least one planar surface having an optically transparent solid material formed thereon, the optically transparent solid material being distinct from the planar waveguide part; and

an input diffraction grating region, an intermediate diffraction grating region, and an output diffraction grating region, each impressed upon the optically transparent solid material, the input diffraction grating region to receive light and diffract the received light along the waveguide, the intermediate diffraction grating region to receive diffracted light from the input diffraction grating region and to expand the received light in a first dimension by diffraction, and the output diffraction grating region to receive and output the expanded light from the waveguide by diffraction;

wherein the input diffraction grating region is positioned wholly within a geographical area bounded by an outer periphery of the intermediate diffraction grating region, and wherein a grating vector of the input diffraction grating region and a grating vector of the intermediate diffraction grating region are oriented in different respective directions.

16. The waveguide according to claim 15 , wherein at least one of:

the optically transparent solid material in which the intermediate diffraction grating region is formed is continuous with the optically transparent solid material in which the input diffraction grating region is formed, such that the input diffraction grating region and the intermediate diffraction grating region are substantially coplanar; and

the optically transparent solid material in which the intermediate diffraction grating region is formed is continuous with the optically transparent solid material in which the output diffraction grating region is formed.

17. The waveguide according to claim 15 , wherein the optically transparent solid material is deposited upon opposite planar surfaces of the planar waveguide part, wherein the impression defining the input diffraction grating region is impressed into the optically transparent solid material deposited upon one surface of the planar waveguide part, wherein the impression defining the intermediate diffraction grating region is impressed into the optically transparent solid material deposited upon an opposite surface of the planar waveguide part, and wherein the intermediate diffraction grating region, when viewed along a direction through the input diffraction grating region perpendicular to the surface of the planar waveguide part upon which the input diffraction grating region has been formed, appears to entirely surround the input diffraction grating region.

18. The waveguide according to claim 15 , further comprising a coating upon the intermediate diffraction grating region, the coating having a refractive index which differs from a refractive index of the optically transparent solid material in which the intermediate diffraction grating region is impressed.

19. The waveguide according to claim 15 , further comprising a coating upon at least one of the input diffraction grating region and the output diffraction grating region, the coating having a refractive index which differs from at least one of a refractive index of the optically transparent solid material in which the input diffraction grating region is impressed and a refractive index of the optically transparent solid material in which the output diffraction grating region is impressed.