Photonic Crystal Waveguide for AR Brightness Uniformity
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Solution Overview
Problem
Existing waveguides in augmented reality displays suffer from brightness gradients in the output image which are undesirable for users, and existing solutions have not effectively mitigated this issue.
Innovation Solution
The waveguide for use in augmented reality or virtual reality displays a plurality of optical structures in a photonic crystal, which are arranged in an array to provide two diffractive optical elements on one another, where each optical element is configured to receive light from an input direction and couple it towards an output direction, where the optical structures have different cross-sectional shapes at different positions in the array to control diffraction efficiencies, thereby improving luminosity uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform optical structures are used in the photonic crystal array, then manufacturing is simpler, but brightness gradients appear in the output image
Solution Approach 1:
The patent applies local quality by varying the cross-sectional dimensions of optical structures at different positions within the photonic crystal array. Specifically, optical structures closer to the input diffractive optical element have different transverse dimensions than those farther away, creating position-dependent diffraction efficiencies that compensate for brightness gradients and achieve uniform luminosity across the output image.
2Illumination intensity
If the cross-sectional area of optical structures is varied to control diffraction efficiency, then luminosity uniformity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements parameter changes by systematically varying the transverse dimensions (cross-sectional area) of optical structures throughout the photonic crystal array. This controlled parameter variation allows precise adjustment of diffraction efficiency at different positions, enabling uniform luminosity output while maintaining manufacturability through defined geometric progressions.
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 solution effectively mitigates brightness gradients in the output image by controlling diffraction efficiencies of the optical structures, resulting in improved luminosity uniformity across the display.
Implementation Method 1
a plurality of optical structures in a photonic crystal... arranged in an array to provide two diffractive optical elements... each diffractive optical element is configured to receive light from an input direction and couple it towards the other diffractive optical element
Implementation Method 2
The projected light is totally internally reflected within the waveguide
Data Source
AI summary
A waveguide for use in an augmented reality or virtual reality display comprises a plurality of optical structures in or on a photonic crystal. The plurality of optical structures are arranged in an array to provide two diffractive optical elements overlaid on one another in the waveguide. Each of the two diffractive optical elements is configured to receive light from an input direction and couple it towards the other diffractive optical element which can then act as an output diffractive optical element, providing outcoupled orders towards a viewer. The plurality of optical structures have different respective cross sectional shapes, for a cross section parallel to the plane of the waveguide, at different positions in the array in order to provide different diffraction efficiencies at different positions in the array.