Eyepieces for augmented reality display system

1. An eyepiece waveguide for an augmented reality display system, the eyepiece waveguide comprising:

an input coupling grating (ICG) region configured to receive an input beam of light and to couple the input beam into the substrate as a guided beam;

a multidirectional pupil expander (MPE) region positioned to receive the guided beam from the ICG region and configured to out-couple a first plurality of output beams, the MPE region comprising diffractive features exhibiting periodicity in multiple directions; and

an exit pupil expander (EPE) region positioned to receive the first plurality of output beams from the MPE region and configured to out-couple a second plurality of output beams, wherein the MPE region comprises diffractive features comprising a 2D array of scattering features arranged in a 2D lattice.

2. The eyepiece waveguide of claim 1 , further comprising an optically transmissive substrate having a first surface and a second surface, wherein the ICG region is formed on or in one of the surfaces of the optically transmissive substrate and the MPE region is formed on or in one of the surfaces of the optically transmissive substrate.

3. The eyepiece waveguide of claim 1 , wherein the ICG region comprises diffractive features that redirect the input beams such that the input beams propagate inside the eyepiece waveguide via total internal reflection.

4. The eyepiece waveguide of claim 3 , wherein the diffractive features of the ICG region form a one-dimensionally periodic (1D) diffraction grating comprising a plurality of lines extending in a first direction and periodically repeating in a second direction orthogonal to the first direction.

5. The eyepiece waveguide of claim 4 , wherein the plurality of lines of the diffractive features of the ICG region is etched into or formed of material deposited onto a first surface or a second surface of the eyepiece waveguide.

6. The eyepiece waveguide of claim 1 , wherein the 2D array of scattering features has associated grating vectors derived from a reciprocal lattice of the 2D lattice.

7. The eyepiece waveguide of claim 6 , wherein the 2D array of scattering features comprises individual scattering features that comprise indentations, protrusions, or both.

8. An eyepiece waveguide for an augmented reality display system, the eyepiece waveguide comprising:

an input coupling grating (ICG) region configured to receive an input beam of light and to couple the input beam into the substrate as a guided beam;

a multidirectional pupil expander (MPE) region positioned to receive the guided beam from the ICG region and configured to out-couple a first plurality of output beams, the MPE region comprising diffractive features exhibiting periodicity in multiple directions; and

an exit pupil expander (EPE) region positioned to receive the first plurality of output beams from the MPE region and configured to out-couple a second plurality of output beams, wherein the MPE region comprises a 2D periodic diffraction grating comprising a crossed grating with a plurality of grating lines, the grating lines repeating along two or more distinct directions of periodicity.

9. The eyepiece waveguide of claim 8 , wherein the crossed grating comprises a superposition of a first and a second 1D grating, wherein a first direction of periodicity of the first 1D grating is different from a second direction of periodicity of the second 1D grating.

10. An eyepiece waveguide for an augmented reality display system, the eyepiece waveguide comprising:

an input coupling grating (ICG) region configured to receive an input beam of light and to couple the input beam into the substrate as a guided beam;

a multidirectional pupil expander (MPE) region positioned to receive the guided beam from the ICG region and configured to out-couple a first plurality of output beams, the MPE region comprising diffractive features exhibiting periodicity in multiple directions; and

an exit pupil expander (EPE) region positioned to receive the first plurality of output beams from the MPE region and configured to out-couple a second plurality of output beams, wherein the MPE region comprises a 2D periodic diffraction grating comprising a crossed grating with a plurality of grating lines, the grating lines repeating along two or more distinct directions of periodicity.

11. The eyepiece waveguide of claim 10 , wherein the 2D periodic diffraction grating is defined by:

u

=

⌊

u

x

,

u

y

⌋

⁢

v

=

⌊

v

x

,

v

y

⌋

⁢

G

=

2

⁢

π

u

x

⁢

v

y

-

u

y

⁢

v

x

[

v

y

,

-

v

x

]

⁢

H

=

2

⁢

π

u

x

⁢

v

y

-

u

y

⁢

v

x

[

-

u

y

,

u

x

]

,

 wherein

G and H are grating vectors corresponding to the fundamental dual or reciprocal lattice vectors, and

vectors u and v define the spatial lattice.

12. The eyepiece waveguide of claim 11 , wherein G is orthogonal to u and H is orthogonal to v.

13. The eyepiece waveguide of claim 11 , wherein u is not parallel to H and v is not parallel to G.

14. The eyepiece waveguide of claim 11 , wherein grating vector G has a magnitude of 2π/a, where a is the period of a first set of grating lines.

15. The eyepiece waveguide of claim 14 , wherein the 2D periodic diffraction grating is associated with harmonics, higher-order harmonics, or both of the grating vector G.

16. The eyepiece waveguide of claim 11 , wherein the grating vector H has a magnitude of 2π/b, where b is the period of a second set of grating lines.

17. The eyepiece waveguide of claim 16 , wherein the 2D periodic diffraction grating is associated with harmonics, higher-order harmonics, or both of the grating vector H.

18. The eyepiece waveguide of claim 11 , wherein the 2D periodic diffraction grating has associated grating vectors corresponding to an entire reciprocal lattice and pointing in directions determined by integer linear combinations of the grating vectors G and H.