Edge sealant confinement and halo reduction for optical devices
Techniques are described for using confinement structures and/or pattern gratings to reduce or prevent the wicking of sealant polymer (e.g., glue) into the optically active areas of a multi-layered optical assembly. A multi-layered optical structure may include multiple layers of substrate imprinted with waveguide grating patterns. The multiple layers may be secured using an edge adhesive, such as a resin, epoxy, glue, and so forth. A confinement structure such as an edge pattern may be imprinted along the edge of each layer to control and confine the capillary flow of the edge adhesive and prevent the edge adhesive from wicking into the functional waveguide grating patterns of the layers. Moreover, the edge adhesive may be carbon doped or otherwise blackened to reduce the reflection of light off the edge back into the interior of the layer, thus improving the optical function of the assembly.
1. An optical structure comprising:
a substrate including:
a first edge grating pattern that is on a first surface of the substrate and that is proximal to an edge of the substrate, the first edge grating pattern arranged to control capillary flow of a material from the edge of the substrate into the first edge grating pattern; and
a second edge grating pattern that is on a second surface of the substrate, the second grating pattern including one or more of an orthogonal pupil expander (OPE) region and an exit pupil expander (EPE) region.
2. The optical structure of claim 1 , wherein the first edge grating pattern includes one or more features that are arranged to be substantially perpendicular to the edge of the substrate.
3. The optical structure of claim 1 , wherein the first edge grating pattern includes one or more of a V-shaped grating pattern, an S-shaped grating pattern, and a rectangular grating pattern.
4. The optical structure of claim 1 , wherein the first edge grating pattern is further arranged to inhibit the capillary flow of the material beyond the first edge grating pattern.
5. The optical structure of claim 4 , wherein the first edge grating pattern includes one or more features that are arranged to be substantially parallel to the edge of the substrate.
6. The optical structure of claim 1 , wherein:
the first edge grating pattern includes one or more first features that are arranged to be substantially perpendicular to the edge of the substrate;
the first edge grating pattern includes one or more second features that are arranged to be substantially parallel to the edge of the substrate and to inhibit the capillary flow of the material beyond the first edge grating pattern; and
the one or more second features differ, at least in part, from the one or more first features in at least one of depth, height, and width.
7. The optical structure of claim 1 , wherein the material has a refractive index that is lower than that of the substrate.
8. The optical structure of claim 1 , wherein the material, as applied, has a gradient of refractive index that varies according to a distance from the edge of the substrate.
9. The optical structure of claim 1 , wherein the first edge grating pattern includes one or more features that have a cross-sectional shape of at least one polygon.
10. The optical structure of claim 9 , wherein the at least one polygon includes one or more of a triangle, a square, and a rectangle.
11. The optical structure of claim 1 , wherein:
the substrate is a waveguide configured to receive and propagate light; and
the material is a light variable absorptive edge material configured to receive and absorb light from the waveguide.
12. The optical structure of claim 1 , wherein the material and the substrate have a substantially same index of refraction.
13. The optical structure of claim 1 , wherein the material comprises a doping agent and an adhesive.
14. The optical structure of claim 13 , wherein the doping agent is distributed at a gradient that varies with distance from an edge of the waveguide.
15. The optical structure of claim 13 , wherein the doping agent comprises carbon black nanoparticles.
16. The optical structure of claim 15 , wherein the carbon black nanoparticles have a diameter in a range of 50-70 nm.
17. The optical structure of claim 1 , wherein the material comprises at least one of a doping agent and an adhesive that is included in at least one layer of adhesive tape.
18. The optical structure of claim 17 , wherein the adhesive tape and the substrate have a substantially same index of refraction.
19. The optical structure of claim 1 , wherein:
the substrate is one of a plurality of layers of substrate included in the optical structure;
each of the plurality of layers includes the first edge grating pattern proximal to a respective edge of the layer; and
the material is an edge adhesive that is applied along at least a portion of a perimeter of the optical structure to secure the plurality of layers of substrate.
20. The optical structure of claim 19 , wherein each of the plurality of layers of substrate further includes the second grating pattern.
21. The optical structure of claim 20 , wherein the first edge grating pattern is arranged to provide for a capillary flow of the edge adhesive into the first edge grating pattern, and is further arranged to inhibit the capillary flow of the edge adhesive into the second grating pattern.
22. The optical structure of claim 20 , wherein:
the second grating pattern is of a nano-scale and operates as a waveguide for light propagation; and
the first edge grating pattern is one or more of a micro-scale and a nano-scale.