Waveguide Grating Gradient Encapsulation for Diffraction Directionality
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Solution Overview
Problem
Existing augmented reality waveguide combiners face challenges in controlling the diffraction efficiency and directionality of out-coupled light, which affects the overlay of virtual images on the ambient environment.
Innovation Solution
A waveguide combiner design featuring gratings with asymmetric structures and a decreasing fill ratio of encapsulant, allowing for controlled diffraction efficiency and directionality through gradient encapsulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If surface relief gratings are used for light coupling in augmented waveguide combiners, then light can be coupled into and out of the waveguide, but the diffraction efficiency and directionality of the out-coupled light cannot be adequately controlled
Solution Approach 1:
The patent applies local quality by varying the encapsulant fill ratio across different regions of the grating structure. The encapsulant material is present in different quantities in different areas, creating spatially varying optical properties that enable precise control of diffraction efficiency and directionality without changing the fundamental grating design
Solution Approach 2:
The patent employs asymmetry by creating non-uniform encapsulant distribution within the grating gaps. The encapsulant fill ratio intentionally varies from one side of the grating to the other, breaking symmetry to achieve directional control and optimized diffraction efficiency for specific viewing angles
2Ease of manufacture
If the grating depth is reduced to simplify fabrication, then manufacturing becomes easier, but the diffraction efficiency and optical performance deteriorate
Solution Approach 1:
The patent changes the encapsulant fill ratio parameter across the grating structure to achieve full-range tuning of diffraction efficiency. By varying this parameter, the system can optimize optical performance without requiring changes to grating depth or other difficult-to-manufacture parameters
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 design enables full-range tuning of diffraction efficiency while maintaining directionality, enhancing the overlay of virtual images on the ambient environment without reducing grating depth.
Implementation Method 1
Light is coupled into and out of augmented waveguide combiners using surface relief gratings. The diffraction efficiency and directionality of the out-coupled light may not be adequately controlled.
Implementation Method 2
A first encapsulant is disposed in one or more gaps formed between adjacent first structures, where a fill ratio of the first encapsulant decreases along the first grating.
Data Source
AI summary
Gradient encapsulation of waveguide outcoupler gratings for control of diffraction efficiency and directionality includes a first grating formed over a substrate, the first grating having a plurality of first structures extending away from the substrate, the first grating corresponding to an outcoupler. The device includes a first encapsulant disposed in one or more gaps formed between adjacent first structures, where a fill ratio of the first encapsulant decreases along the first grating. Also described herein are methods for fabricating the device.