Augmented Reality Optical Waveguide Coating for Grating Edge Scattering
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Solution Overview
Problem
Augmented reality displays suffer from image dispersion due to components of diffracted light being incident on surface relief gratings, which reduces image sharpness.
Innovation Solution
An optical waveguide with a surface relief grating coated by a material having optical characteristics that converge with the substrate, reducing scattering by filling or narrowing the grooves where light coincides with the grating edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface relief grating is used to guide light in optical waveguide, then light guidance function is improved, but light dispersion occurs reducing image sharpness
Solution Approach 1:
The patent applies local quality by coating only the groove regions of the surface relief grating with a material having refractive index matching the substrate, while leaving the ridge regions uncoated. This localized coating approach specifically addresses the light dispersion issue at the groove edges where light coincidence occurs, without affecting the overall light guidance function of the grating structure.
Solution Approach 2:
The coating material acts as an intermediary substance between the groove region and the incident light. By selecting a coating material with refractive index matching the substrate, the optical impedance mismatch at the groove edge is eliminated, preventing light scattering and dispersion while maintaining the grating's light guidance capability.
2Manufacturing precision
If coating material is applied to fill grooves, then light scattering is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes parameter changes by selecting a coating material with a specific refractive index parameter that matches the substrate. This parameter matching transforms the optical properties of the groove region, eliminating scattering without requiring complex multi-layer coatings or additional optical elements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coating minimizes light dispersion, enhancing image sharpness and clarity in augmented reality devices by ensuring light travels unscattered through the optical waveguide.
Implementation Method 1
The surface relief grating at the inlet guides incoming light (or image) from the projector towards the outlet via diffraction
Implementation Method 2
an image is delivered from a projector to a user's eye (or eyes) via an optical waveguide
Implementation Method 3
a coating disposed on the surface relief grating and filling at least partially at least one groove disposed at an edge of the surface relief grating where the image is coincident with the at least one groove after a first reflection of the image inside the substrate, the coating having optical characteristics convergent with optical characteristics of the substrate
Data Source
AI summary
This document discloses a solution for an optical waveguide for an augmented reality display device. According to an aspect, the optical waveguide comprises: a substrate arranged to guide an optical image inside the substrate from an inlet to an outlet of the optical waveguide via a plurality of reflections; a surface relief grating at the inlet or the outlet of the optical waveguide, the surface relief grating guiding the image in the optical waveguide via diffraction and comprising a plurality of grooves; a coating disposed on the surface relief grating and filling at least partially at least one groove disposed at an edge of the surface relief grating where the image is coincident with the at least one groove after a first reflection of the image inside the substrate, the coating having optical characteristics convergent with optical characteristics of the substrate.