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 waveguide display substrate comprising:
a cylindrical portion having a planar surface;
a curved portion opposite the planar surface, defining a nonlinear change in thickness across the substrate; and
a wedge portion between the cylindrical portion and the curved portion, defining a linear change in thickness across the substrate, wherein a range of a dome height of the curved portion is between 700 nm and 1300 nm, and a maximum height of the wedge portion is less than 300 nm.
2. The waveguide display substrate of claim 1 , wherein D is a maximum height of the curved portion with respect to the cylindrical portion, and wherein D is between 70% and 130% of a target maximum height Dt of the curved portion.
3. The waveguide display substrate of claim 1 , wherein W is a maximum height of the wedge portion with respect to the cylindrical portion, and wherein W is less than 30% of a target maximum height Dt of the curved portion.
4. The waveguide display substrate of claim 1 , wherein the nonlinear change in thickness is a quadratic change in thickness.
5. The waveguide display substrate of claim 1 , wherein the curved portion in is the form of a dome.
6. The waveguide display substrate of claim 5 , wherein the dome is spherical.
7. The waveguide display substrate of claim 1 , wherein an average thickness of the waveguide display substrate is between about 200 microns and about 2000 microns.
8. The waveguide display substrate of claim 1 , wherein an average diameter of the waveguide display substrate is between about 2 centimeters and about 50 centimeters.
9. The waveguide display substrate of claim 1 , wherein the waveguide display substrate comprises a molded polymer.
10. The waveguide display substrate of claim 1 , wherein the waveguide display substrate comprises at least one of a polished glass, silicon, or a metal substrate.
11. A method comprising:
fabricating a waveguide display substrate such that the substrate comprises:
a cylindrical portion having a planar surface;
a curved portion opposite the planar surface and defining a nonlinear change in thickness across the substrate; and
a wedge portion between the cylindrical portion and the curved portion, defining a linear change in thickness across the substrate, wherein a range of a dome height of the curved portion is between 700 nm and 1300 nm, and a maximum height of the wedge portion is less than 300 nm.
12. The method of claim 11 , wherein D is a maximum height of the curved portion with respect to the cylindrical portion, and wherein the waveguide display substrate is fabricated such that D is between 70% and 130% of a target maximum height Dt of the curved portion.
13. The method of claim 11 , wherein W is a maximum height of the wedge portion with respect to the cylindrical portion, and wherein the waveguide display substrate is fabricated such that W is less than 30% of a target maximum height Dt of the curved portion.
14. The method of claim 11 , wherein the waveguide display substrate is fabricated such that the nonlinear change in thickness is a quadratic change in thickness.
15. The method of claim 11 , wherein the waveguide display substrate is fabricated such that the curved portion in is the form of a dome.
16. The method of claim 15 , wherein the waveguide display substrate is fabricated such that the dome is spherical.
17. The method of claim 11 , wherein the waveguide display substrate is fabricated such that an average thickness of the waveguide display substrate is between about 200 microns and about 2000 microns.
18. The method of claim 11 , wherein the waveguide display substrate is fabricated such that an average diameter of the waveguide display substrate is between about 2 centimeters and about 50 centimeters.
19. The method of claim 11 , wherein the waveguide display substrate is fabricated using a molded polymer.
20. The method of claim 11 , wherein the waveguide display substrate is fabricated using at least one of a polished glass, silicon, or a metal substrate.