Image light guide with expanded light distribution overlapping gratings

An image light guide for conveying a virtual image, comprising:

• a waveguide configured to propagate image-bearing light beams along a length thereof;
• an in-coupling diffractive optic formed along the waveguide, wherein the in-coupling diffractive optic is configured to diffract the image-bearing light beams from an image source into the waveguide, whereby at least a portion of the image-bearing light beams propagate along the waveguide in an angularly encoded form;
• and
• an out-coupling diffractive optic spaced apart from the in-coupling diffractive optic along the length of the waveguide, wherein the out-coupling diffractive optic is configured to diffract the image-bearing light beams from the waveguide in an angularly decoded form toward an eyebox;
• wherein the out-coupling diffractive optic comprises a plurality of diffractive features in a plane defining a plurality of diffraction patterns having different orientations within the plane, wherein two or more diffraction patterns are configured to relatively displace portions of each of the image-bearing light beams in two dimensions for expanding the eyebox in two dimensions;
• wherein each of the diffractive features comprises a length and a width in the plane, and an aspect ratio of length to width;
• wherein the plurality of diffractive features includes a sub-plurality of diffractive features having an aspect ratio that departs from unity, wherein the aspect ratio is configured to alter diffraction efficiencies among the diffraction patterns;
• and
• wherein the aspect ratio of the diffractive features varies along a first direction.