Input coupling gratings for waveguide-based displays
An input coupling grating (ICG) for a waveguide-based display comprises an input region that receives light and a plurality of unit cells. Each unit cell includes photonic structures arranged at a pitch. The photonic structures of at least one first unit cell have at least one different structural characteristic than the photonic structures of at least one second unit cell.
1 . An input coupling grating (ICG) for a waveguide-based display, the ICG comprising:
a surface that receives light;
a plurality of unit cells at the surface, each unit cell including photonic structures arranged at a pitch, wherein the photonic structures of at least one first unit cell have at least one different structural characteristic than the photonic structures of at least one second unit cell, wherein a width of each unit cell gradually decreases along a propagation direction of the light, wherein the width of each unit cell is measured in the propagation direction;
a reflective coating on the photonic structures of the plurality of unit cells; and
a diffractive coating between the reflective coating and the photonic structures,
wherein the at least one different structural characteristic corresponds to the photonic structures in the at least one first unit cell having a different shape than the photonic structures in the at least one second unit cell, wherein the photonic structures in the at least one first unit cell have a reference shape, and wherein the photonic structures in the at least one second unit cell have an addition to the reference shape, a subtraction from the reference shape, or both.
2 . The ICG of claim 1 , wherein the pitch is substantially the same for the photonic structures of at least two unit cells.
3 . The ICG of claim 1 , wherein the pitch is substantially the same for the photonic structures of all of the plurality of unit cells.
4 . The ICG of claim 1 , wherein the light is transmitted via internal reflection along the propagation direction to an output coupling grating.
5 . The ICG of claim 1 , wherein the addition to the reference shape includes an extrusion added to the reference shape.
6 . The ICG of claim 1 , wherein the subtraction to the reference shape includes a crop of the reference shape or a split of the reference shape.
7 . The ICG of claim 1 , wherein the different shape corresponds to a rotation of the reference shape.
8 . The ICG of claim 1 , wherein the at least one different structural characteristic corresponds to the photonic structures in the at least one first unit cell having a different scale than the photonic structures in the at least one second unit cell.
9 . The ICG of claim 1 , wherein the diffractive coating comprises separate diffractive coating segments.
10 . A waveguide-based display, comprising:
a waveguide comprising a surface that receives light, wherein the waveguide transmits the light via internal reflection along a propagation direction;
at least one input coupling grating (ICG) coupled to the waveguide and including:
a plurality of unit cells at the surface, each unit cell including photonic structures arranged at a pitch, wherein the photonic structures of at least one first unit cell have at least one different structural characteristic than the photonic structures of at least one second unit cell, wherein the at least one different structural characteristic corresponds to the photonic structures in the at least one first unit cell having a different shape than the photonic structures in the at least one second unit cell, wherein the photonic structures in the at least one first unit cell have a reference shape, and wherein the photonic structures in the at least one second unit cell have an addition to the reference shape, a subtraction from the reference shape, or both, wherein a width of each unit cell gradually decreases along the propagation direction, and wherein the width of each unit cell is measured in the propagation direction;
a reflective coating on the photonic structures of the plurality of unit cells; and
a diffractive coating between the reflective coating and the photonic structures; and
an output coupling grating (OCG) that outputs the light that has traveled from the ICG along the propagation direction to an eyebox.
11 . The waveguide-based display of claim 10 , wherein the pitch is substantially the same for the photonic structures of all of the plurality of unit cells.
12 . The waveguide-based display of claim 10 , wherein the different shape corresponds to a rotation of the reference shape.
13 . The waveguide-based display of claim 10 , wherein the at least one different structural characteristic corresponds to the photonic structures in the at least one first unit cell having a different scale than the photonic structures in the at least one second unit cell.
14 . An input coupling grating (ICG) for a waveguide-based display, the ICG comprising:
a waveguide comprising surface that receives light, wherein the waveguide transmits the light via internal reflection along a propagation direction from the ICG to an output coupling grating;
a plurality of photonic structures arranged at the surface at a substantially same pitch and divided into unit cells, wherein a shape of photonic structures in a first unit cell of the unit cells differs compared to a shape of photonic structures in a second unit cell of the unit cells, wherein the photonic structures in the first unit cell have a reference shape, and wherein the photonic structures in the second unit cell have an addition to the reference shape, a subtraction from the reference shape, or both, wherein a width of each unit cell gradually decreases along the propagation direction of the light, and wherein the width of each unit cell is measured in the propagation direction;
a reflective coating on the photonic structures of the unit cells; and
a diffractive coating between the reflective coating and the photonic structures.