AR Waveguide Polygonal Optical Structures for Striping Reduction
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Solution Overview
Problem
Known waveguides in augmented reality displays exhibit a 'striping' effect where the central strip of the output image has higher relative brightness, which is undesirable and affects the user's experience.
Innovation Solution
The waveguide incorporates a plurality of optical structures arranged in an array with at least two diffractive optical elements overlaid on each other, where the optical structures have substantially straight sides at different angles, improving diffraction efficiency and reducing the striping effect by altering the shape from circular to polygonal with vertices and rounded edges, enhancing light coupling and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If circular cross-sectional optical structures are used in the waveguide, then light coupling efficiency is improved, but a striping effect occurs in the output image with non-uniform brightness distribution
Solution Approach 1:
The patent applies local quality by varying the shape of optical structures at different locations within the waveguide. Specifically, optical structures at different positions have different cross-sectional shapes (e.g., circular, rectangular, triangular, or polygonal) to locally control the diffraction of light. This local variation in shape prevents the formation of a central bright strip by distributing light more uniformly across the output image, while still maintaining effective light coupling throughout the waveguide.
2Illumination intensity
If optical structures with varied shapes are used to reduce striping effect, then brightness uniformity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent employs parameter changes by systematically varying the cross-sectional shape parameter of optical structures throughout the waveguide. Instead of using a single uniform shape, the shape parameter (circular, rectangular, triangular, polygonal) is changed across different locations to control light diffraction and eliminate the striping effect. This parameter variation can be implemented through manufacturing techniques such as photolithography or 3D printing, balancing the need for shape diversity with manufacturing feasibility.
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 increases the proportion of light coupled towards the viewer, mitigates the striping effect, and improves the overall efficiency of the waveguide by optimizing light distribution, resulting in a more uniform and effective augmented reality display.
Implementation Method 1
Light from the projector is coupled into the waveguide by a diffraction grating. The projected light is totally internally reflected within the waveguide. The light is then coupled out of the waveguide by another diffraction grating so that it can be viewed by a user.
Implementation Method 2
The projected light is totally internally reflected within the waveguide.
Data Source
AI summary
A waveguide is disclosed for use in an augmented reality or virtual reality display. The waveguide includes a plurality of optical structures exhibiting differences in refractive index from a surrounding waveguide medium. The optical structures are arranged in an array to provide at least 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 optical structures have a shape, when viewed in the plane of the waveguide, comprising a plurality of substantially straight sides having respective normal vectors at different angles and this can effectively reduce the amount of light that is coupled out of the waveguide on first interaction with the optical structures.