SPACERS FOR WAVEGUIDE STACKS IN OPTICAL DEVICES
This disclosure describes techniques for manufacturing waveguides that include spacer(s) on at least one surface of the waveguide, such that the spacers maintain mechanical stability and separation between the waveguides when the waveguides as assembled into a waveguide stack that is usable as an optical device. The disclosure also describes the various implementations of waveguides and optical devices that include spacers. The spacers may be created using a drop dispenser, in which drops of a (e.g., polymer) fluid are dispensed onto at least one surface of a substrate to be used as a waveguide. After being dispensed, the fluid drops can be cured to create the final, solidified spacers. Curing may also be performed in-flight before the drops reach the surface of the substrate. Partially cured drops may be stacked to create spacers of a particular height.
1 . A waveguide stack for use in an optical device, the waveguide stack comprising:
a first waveguide configured to convey first light through total internal reflection (TIR); and
a second waveguide configured to convey second light through TIR, wherein the second waveguide includes, on at least one surface of the second waveguide, a plurality of spacers composed of a polymer material that has been dispensed onto the at least one surface and cured, wherein the plurality of spacers are arranged on the at least one surface such that the plurality of spacers are between the second waveguide and the first waveguide in the waveguide stack, and wherein the plurality of spacers each have a respective size to maintain a predetermined separation between the first waveguide and the second waveguide in the waveguide stack.
2 . The waveguide stack of claim 1 , wherein the second light has a range of wavelengths, and wherein the plurality of spacers are composed of a material that absorbs the second light having the range of wavelengths.
3 . The waveguide stack of claim 1 , wherein the plurality of spacers are composed of a material that is black.
4 . The waveguide stack of claim 1 , wherein the plurality of spacers each have a diameter in a range of 10 microns to 200 microns.
5 . The waveguide stack of claim 1 , wherein the predetermined separation is in a range of 30 microns to 50 microns or 35 microns to 45 microns.
6 . The waveguide stack of claim 1 , wherein the plurality of spacers inhibits direct contact between the first waveguide and the second waveguide.
7 . (canceled)
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9 . (canceled)
10 . The waveguide stack of claim 9 , wherein the plurality of spacers comprise a dye or pigment selected to absorb all or a portion of light in the visible region.
11 . The waveguide stack of claim 1 , wherein the plurality of spacers comprise inorganic nanoparticles.
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15 . The waveguide stack of claim 1 , wherein the second waveguide includes, on at least one surface of the second waveguide, one or more optically active regions, and wherein at least one of the plurality of spacers is located in the one or more optically active regions.
16 . The waveguide stack of claim 15 , wherein the one or more optically active regions include one or more of an exit pupil expander (EPE), an orthogonal pupil expander (OPE), a combined pupil expander (CPE), or an in-coupling grating (ICG).
17 . (canceled)
18 . The waveguide stack of claim 1 , wherein the second waveguide includes, on at least one surface of the second waveguide, at least one confinement region bounded by one or more confinement gratings, and wherein at least one of the plurality of spacers is located in the at least one confinement region.
19 . (canceled)
20 . The waveguide stack of claim 1 , wherein the first and second waveguides are curved.
21 . The waveguide stack of claim 1 , further comprising a third waveguide configured to convey third light through TIR, wherein the first light has a first range of wavelengths, wherein the second light has a second range of wavelengths different than the first range, and wherein the third light has a third range of wavelengths different than the first range and the second range.
22 . (canceled)
23 . The waveguide stack of claim 21 , wherein the third waveguide includes, on at least one second surface of the third waveguide, a second plurality of spacers composed of the polymer material that has been dispensed onto the at least one second surface and cured, wherein the second plurality of spacers are arranged on the at least one second surface such that the second plurality of spacers are between the third waveguide and the second waveguide in the waveguide stack, and wherein the second plurality of spacers each have a respective size to maintain a predetermined separation between the second waveguide and the third waveguide in the waveguide stack.
24 . (canceled)
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28 . The waveguide stack of claim 1 , wherein at least two of the plurality of spacers have different sizes.
29 . (canceled)
30 . A method of manufacturing a waveguide stack for use in an optical device, the method comprising:
dispensing a plurality of drops of a prepolymer material onto at least one surface of a first waveguide;
curing the drops to form a plurality of spacers from the plurality of drops; and
stacking the first waveguide with a second waveguide to assemble the waveguide stack,
wherein the plurality of spacers are arranged on the at least one surface such that the plurality of spacers are between the second waveguide and the first waveguide in the waveguide stack, and wherein the plurality of spacers each have a respective size to maintain a predetermined separation between the first waveguide and the second waveguide in the waveguide stack.
31 . The method of claim 30 , wherein the plurality of drops are dispensed from a drop dispenser, and wherein the drops are fully cured after they exit the drop dispenser and before the drops reach the at least one surface.
32 . The method of claim 30 , wherein the plurality of drops are dispensed from a drop dispenser, and wherein the drops are partially cured after they exit the drop dispenser and before the drops reach the at least one surface.
33 . The method of claim 30 , wherein the plurality of drops are dispensed from a drop dispenser, and wherein curing the drops comprises:
a first curing in which the drops are partially cured after they exit the drop dispenser and before they reach the at least one surface; and
a second curing in which the drops are fully cured after the drops reach the at least one surface.
34 . The method of claim 30 , wherein the prepolymer material comprises a dye or pigment selected to absorb all or a portion of light in the visible region, wherein the prepolymer material comprises inorganic nanoparticles.
35 . (canceled)
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