Biased total thickness variations in waveguide display substrates
A plurality of waveguide display substrates, each waveguide display substrate having a cylindrical portion having a diameter and a planar surface, a curved portion opposite the planar surface defining a nonlinear change in thickness across the substrate and having a maximum height D with respect to the cylindrical portion, and a wedge portion between the cylindrical portion and the curved portion defining a linear change in thickness across the substrate and having a maximum height W with respect to the cylindrical portion. A target maximum height D t of the curved portion is 10 −7 to 10 −6 times the diameter, D is between about 70% and about 130% of D t , and W is less than about 30% of D t .
1. A plurality of waveguide display substrates, each waveguide display substrate having:
a cylindrical portion having a diameter and a planar surface;
a curved portion opposite the planar surface, defining a nonlinear change in thickness across the substrate and having a maximum height D with respect to the cylindrical portion; and
a wedge portion between the cylindrical portion and the curved portion, defining a linear change in thickness across the substrate and having a maximum height W with respect to the cylindrical portion,
wherein a target maximum height D t of the curved portion is 10 −7 to 10 −6 times the diameter, D is between 70% and 130% of D t , and W is less than 30% of D t , and
wherein, for the plurality of waveguide display substrates, an average of D is D mean , a maximum D for the plurality of waveguide display substrates is D max , a minimum D for the plurality of waveguide display substrates is D min , and a maximum W for the plurality of waveguide display substrates is W max .
2. The plurality of waveguide display substrates of claim 1 , wherein the nonlinear change in thickness is a quadratic change in thickness.
3. The plurality of waveguide display substrates of claim 1 , wherein the curved portion in is the form of a dome.
4. The plurality of waveguide display substrates of claim 3 , wherein the dome is spherical.
5. The plurality of waveguide display substrates of claim 1 , wherein an average thickness of the plurality of waveguide display substrates is between about 200 microns and about 2000 microns.
6. The plurality of waveguide display substrates of claim 1 , wherein an average diameter of the plurality of waveguide display substrates is between about 2 centimeters and about 50 centimeters.
7. The plurality of waveguide display substrates of claim 1 , wherein W max D mean is less than about 0.3.
8. The plurality of waveguide display substrates of claim 1 , wherein (D mean −D min )/D mean is less than about 0.3.
9. The plurality of waveguide display substrates of claim 1 , wherein (D max −D min )/D mean is less than about 0.3.
10. The plurality of waveguide display substrates of claim 1 , wherein D is in a range of about 0.1 microns to about 5 microns.
11. The plurality of waveguide display substrates of claim 1 , wherein W is in a range of 0 to about 1.5 microns.
12. The plurality of waveguide display substrates of claim 1 , wherein an average total thickness variation of the plurality of substrates is between about 0.1 microns and about 6.5 microns.
13. The plurality of waveguide display substrates of claim 1 , wherein the waveguide display substrates comprise a molded polymer.
14. The plurality of waveguide display substrates of claim 1 , wherein the waveguide display substrates comprise a polished glass, silicon, or metal substrate.
15. A method of fabricating a plurality of waveguide display substrates, each waveguide display substrate having:
a cylindrical portion having a diameter and a planar surface;
a curved portion opposite the planar surface and defining a nonlinear change in thickness across the substrate and having a maximum height D with respect to the cylindrical portion; and
a wedge portion between the cylindrical portion and the curved portion and defining a linear change in thickness across the substrate and having a maximum height W with respect to the cylindrical portion,
wherein a target maximum height D t of the curved portion is 10 −7 to 10 −6 times the diameter, D is between 70% and 130% of D t , and W is less than 30% of D t , and
wherein, for the plurality of polished waveguide display substrates, an average of D is D mean , a maximum D for the plurality of polished waveguide display substrates is D max , a minimum D for the plurality of polished waveguide display substrates is D min , and a maximum W for the plurality of polished waveguide display substrates is W max .
16. The method of claim 15 , wherein fabricating the plurality of waveguide display substrates comprises polishing the waveguide display substrates, wherein the waveguide display substrates are formed of glass, metal, or silicon.
17. The method of claim 15 , wherein fabricating the plurality of waveguide display substrates comprises molding polymeric waveguide display substrates.
18. The method of claim 15 , further comprising forming one or more waveguides on each of the waveguide display substrates.
19. The method of claim 18 , wherein the one or more waveguides comprise at least two waveguides, and the waveguides are positioned in a radial pattern on each waveguide display substrate.