AR Waveguide Outcoupling with Dual-Efficiency Diffractive Elements
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Solution Overview
Problem
Existing augmented reality displays suffer from inefficiencies in optical power transfer due to light paths that expand within the waveguide without being coupled out towards the viewer, leading to reduced optical efficiency and battery life in wearable devices.
Innovation Solution
An optical structure with overlaid diffractive optical elements having different diffraction efficiencies is used, where the first diffractive optical element has a high diffraction efficiency and the second has a low diffraction efficiency, allowing light to be preferentially expanded in two dimensions and coupled out of the waveguide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If two diffractive optical elements with the same diffraction efficiency are overlaid to expand light in two dimensions, then space utilization is improved, but optical efficiency deteriorates due to light paths that expand without outcoupling
Solution Approach 1:
The patent applies local quality by assigning different diffraction efficiencies to different regions of the output element. The first diffractive optical element has a first diffraction efficiency while the second diffractive optical element has a second diffraction efficiency that is lower than the first. This spatial variation in diffraction efficiency ensures that light is preferentially coupled out in certain directions while maintaining two-dimensional expansion, thereby resolving the contradiction between space utilization and optical efficiency.
2Ease of manufacture
If conventional output element design is used, then manufacturing is simpler, but optical efficiency is reduced due to wasted light paths
Solution Approach 1:
The patent implements parameter changes by modifying the diffraction efficiency parameter of the diffractive optical elements. Specifically, it uses a first diffractive optical element with a first diffraction efficiency and a second diffractive optical element with a second diffraction efficiency that is lower than the first. This parameter differentiation optimizes light outcoupling while maintaining manufacturability through standard photonic crystal 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 arrangement increases optical efficiency by promoting outcoupling of light towards the viewer, reducing wasted light paths and extending battery life in augmented reality systems.
Implementation Method 1
an output element having two diffractive optical elements overlaid on one another in the waveguide so that each of the two diffractive optical elements can receive light from the input diffractive optical element and couple it towards the other diffractive optical element in the pair
Implementation Method 2
The projected light is totally internally reflected within the waveguide
Data Source
AI summary
An optical structure for an augmented reality display includes a waveguide and an input diffractive optical structure to receive light from a projector and couple the received light into the waveguide. An output diffractive optical structure, comprising first and second diffractive optical elements overlaid on one another in or on the waveguide, receives light from the input diffractive optical element in an input direction. The first diffractive optical element has a high diffraction efficiency relative to the second diffractive optical element. A first portion of the first diffractive optical element couples light from the input direction towards a second portion, and the second diffractive optical element couples light from the input direction away from the second portion. The second portion couples light from the input direction towards the first portion, and the second diffractive optical element couples light from the input direction away from the first portion.