Edge-Coupled Waveguide Layers for Compact Near-Eye Displays
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Solution Overview
Problem
Designing electronic devices with near-eye displays, such as virtual and augmented reality headsets, is challenging due to the unsightly and bulky components that often fail to achieve desired optical performance levels.
Innovation Solution
The use of edge-coupled media layers in optical waveguides, comprising first and second media layers with different refractive indices and optically clear adhesive layers, to confine and redirect image light efficiently, combined with louvered mirrors and holographic couplers, minimizes space usage while maintaining bright and uniform image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional optical components are used in near-eye displays, then optical performance can be achieved, but the device becomes bulky and unsightly
Solution Approach 1:
The optical waveguide is divided into multiple functional layers (input coupler layer, media layers with cross-couplers, output coupler layer) that can be independently optimized. Each layer performs a specific optical function, allowing the overall system to achieve high optical performance while maintaining a compact form factor through specialized miniaturized components in each segment
Solution Approach 2:
Multiple optical components (input coupler, cross-couplers, output coupler) are nested within the thin profile of the waveguide structure. The media layers are edge-coupled together, with one media layer nested within the structural envelope of another, maximizing optical functionality within minimal volume
2Volume of moving object
If compact waveguide design is used, then device size is reduced, but optical performance may deteriorate
Solution Approach 1:
The design optimizes specific parameters including the thickness of media layers, refractive indices of materials, and spacing between coupling elements. By precisely controlling these parameters, the waveguide achieves efficient light propagation and coupling in a compact geometry, maintaining high optical performance despite reduced overall dimensions
Solution Approach 2:
The optical path is folded within the waveguide using total internal reflection at angled interfaces. Light propagates through the media layers in a zigzag pattern, effectively increasing the optical path length within a short physical distance. This dimensional folding allows compact waveguide design while preserving optical performance
3Reliability
If multiple media layers are stacked to improve optical performance, then image quality improves, but device complexity increases
Solution Approach 1:
Multiple media layers are edge-coupled together to form an integrated waveguide structure. The layers are bonded using optically clear adhesives with matched refractive indices, creating a unified optical system where light propagates seamlessly across layer boundaries. This merging approach improves image quality through enhanced light control while managing complexity through standardized fabrication processes
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
This configuration allows for a compact optical waveguide that provides bright and uniform images to the user, reducing bulkiness and enhancing optical performance.
Implementation Method 1
The first media layer may propagate the image light via total internal reflection
Implementation Method 2
An input coupler such as an input coupling prism may couple the image light into the first media layer through the first waveguide substrate
Implementation Method 3
A cross-coupler in the first media layer may redirect the image light towards the second media layer as the image light propagates through the first media layer
Implementation Method 4
The first and second layers may have an index of refraction that is different than that of the first media layer... The first and second layers may serve to confine the image light within the first media layer
Implementation Method 5
The output coupler may include volume holograms recorded in the second media layer
Data Source
AI summary
The display may include a waveguide that directs light towards an eye box. The waveguide may include first and second media layers that are edge-coupled at an interface. The first media layer may include a louvered mirror cross-coupler that redirects the light towards the second media layer. The second media layer may include a volume hologram output coupler that couples the light out of the waveguide. Additional layers may be interposed between the first media layer and waveguide substrates. The additional layers may help confine the light within the first media layer as the light propagates such that all of the light enters the second media layer through the interface. This may configure the waveguide to occupy a minimal amount of space within the display while also providing the eye box with as bright and uniform an image as possible.