AR Optical Assembly Diffractive Structures for Uniform Illumination
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Solution Overview
Problem
Existing augmented reality and virtual reality display technologies face challenges in achieving uniform brightness and efficient optical performance, leading to issues like dark banding and reduced optical efficiency.
Innovation Solution
The optical assembly incorporates a waveguide with an input diffractive optical structure and an output diffractive optical structure comprising overlaid first and second diffractive optical elements with different diffraction efficiencies. This configuration ensures even illumination by positioning input pupils off-center and using elliptical or rectangular pupils to balance light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If output elements expand light strongly in two dimensions, then light distribution is improved, but dark banding appears in the central portion
Solution Approach 1:
The patent applies local quality by using overlaid diffractive optical elements with spatially varying diffraction efficiencies. The first diffractive optical element has regions with different diffraction efficiencies (e.g., higher efficiency at edges, lower efficiency at center), and the second element complements this pattern. This creates locally optimized light coupling that compensates for the dark banding effect while maintaining overall uniform illumination.
Solution Approach 2:
The patent employs asymmetry through the use of two diffractive optical elements with unequal diffraction efficiencies. The first element has higher diffraction efficiency than the second element, creating an asymmetric light distribution pattern that balances the strong expansion effect with compensation for central dark regions. This asymmetric design is deliberately chosen to achieve uniform overall illumination.
2Illumination intensity
If output elements produce strong straight-to-eye order, then central brightness is improved, but overall optical efficiency is reduced
Solution Approach 1:
The patent applies parameter changes by varying the diffraction efficiency parameter across different regions and between different elements. The first diffractive optical element has a higher diffraction efficiency parameter than the second element, and both elements have spatially varying efficiency parameters. This controlled parameter variation allows optimization of both central brightness and overall optical efficiency by directing light to appropriate regions and angles.
Solution Approach 2:
The patent employs dynamics through the interaction of two diffractive optical elements that work together to dynamically distribute light. The overlaid elements create a dynamic light coupling system where light paths are continuously redirected and distributed across different angles and regions, optimizing both central brightness and overall energy utilization.
3Ease of manufacture
If conventional output elements are used, then manufacturing is simpler, but uniformity of brightness is poor
Solution Approach 1:
The patent applies the nested doll principle by overlaying two diffractive optical elements on top of each other within the same waveguide structure. The first diffractive optical element is positioned beneath the second diffractive optical element, creating a nested configuration where both elements work together to achieve uniform brightness distribution. This nested arrangement maintains compatibility with existing waveguide manufacturing processes while significantly improving optical performance.
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 provides more even illumination, reduces dark banding, and improves optical efficiency, leading to extended battery life in consumer devices and enhanced brightness in augmented reality images, especially in bright external lighting conditions.
Implementation Method 1
an input diffractive optical structure configured to receive light from the at least one projector and couple the received light into the waveguide
Implementation Method 2
The projected light is totally internally reflected within the waveguide
Implementation Method 3
an output diffractive optical structure configured to receive light from the input diffractive optical element in an input direction... providing outcoupled orders towards a viewer
Data Source
AI summary
An optical assembly is disclosed in which two input pupils of light are projected onto an input grating. The input pupils can be overlapping or non-overlapping. The input grating is configured to receive the input pupils and to diffract them so that they are coupled towards an output element in parallel directions that are laterally separated from one another. The input pupils can be received respectively at a first portion and a second portion of an output element, on either side of a dividing line. The input pupils are received at positions that are symmetrically displaced from the dividing line. The first portion and the second portion are mirror-images of one another, and each can expand light from respective input pupils in an equal and opposite way.