Array Waveguide Stacking for AR Color Uniformity
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Solution Overview
Problem
Existing two-dimensional array waveguides in augmented reality displays suffer from significant color non-uniformity due to varying splitting ratios of light at different wavelengths and angles, which is challenging to address with current optical coatings.
Innovation Solution
An array waveguide system comprising N two-dimensional array waveguide layers with in-coupling and pupil expansion portions, utilizing dichroic mirrors and beam splitting films with a 50% splitting ratio, and adhesive layers to enhance color uniformity and simplify the coating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional optical coatings are used in two-dimensional array waveguides, then the waveguide can guide light, but the splitting ratio varies with wavelength and angle causing color non-uniformity
Solution Approach 1:
The waveguide is divided into multiple waveguide layers, each handling specific color channels. By segmenting the wavelength handling across different layers, each layer can be optimized for specific wavelengths, improving overall color uniformity while simplifying the coating requirements for each individual layer.
Solution Approach 2:
Different waveguide layers are assigned different optical coating characteristics tailored to their specific wavelength ranges. Each layer has locally optimized coating properties rather than a single universal coating, which improves color uniformity for each color channel while managing overall system complexity.
2Adaptability or versatility
If multiple beam splitting surfaces are added to increase field of view, then the field of view expands, but the color non-uniformity becomes more serious due to accumulated splitting ratio variations
Solution Approach 1:
The field of view expansion is achieved through multiple waveguide layers stacked together, each contributing to the overall FOV. By segmenting the FOV expansion function across layers rather than using multiple beam splitters in a single layer, the color uniformity problem is mitigated as each layer handles a specific color channel with optimized coatings.
Solution Approach 2:
Instead of expanding FOV by adding more beam splitting surfaces in the same waveguide layer (which worsens color uniformity), the patent transitions to the dimensional approach of stacking multiple waveguide layers vertically. This dimensional change allows FOV expansion while maintaining color uniformity through specialized coating design in each layer.
3Manufacturing precision
If conventional coating methods are used to control light splitting, then the splitting ratio can be controlled at specific wavelengths, but the coating process becomes extremely complex for full-color display
Solution Approach 1:
The coating process is segmented by wavelength ranges, with different waveguide layers optimized for specific color channels (e.g., red, green, blue). This segmentation allows each layer to use simpler, more targeted coating processes rather than attempting to coat all wavelengths uniformly, improving both manufacturing precision and ease of manufacture.
Solution Approach 2:
The patent changes the coating parameters (thickness, material composition, layer structure) for each waveguide layer based on its specific wavelength range. By adjusting coating parameters to match the operational wavelength of each layer, the system achieves precise splitting ratio control while simplifying the overall coating process through parameter optimization rather than universal complexity.
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 system effectively balances overall colors, improving color uniformity and user experience while reducing the complexity of the coating process, thereby enhancing mass productivity.
Implementation Method 1
The reflection surface is provided with a dichroic mirror
Implementation Method 2
array optical waveguides utilize simple light reflection and refraction to implement the expansion of the exit pupil
Implementation Method 3
array optical waveguides utilize simple light reflection and refraction to implement the expansion of the exit pupil
Implementation Method 4
the optical coating utilizes the principle of light interference, the splitting ratio of the light at an optical interface is controlled by stacking dielectric layers with different thicknesses
Implementation Method 5
the image light is transmitted to a light splitting surface after a certain length of transmission through total reflection
Data Source
AI summary
Disclosed are an array waveguide system and an augmented reality display device. The system includes an optical engine, N two-dimensional array waveguide layers, and an adhesive layer. The optical engine is configured to emit image beams of N colors. The N two-dimensional array waveguide layers are sequentially stacked in order from near to far from the optical engine. An in-coupling portion is disposed in a light incident region of each two-dimensional array waveguide layer and adjacent to the optical engine. Each two-dimensional array waveguide layer includes a pupil expansion portion adjacent to the in-coupling portion. N≥2. The in-coupling portion at least includes a light incident surface, a reflection surface, and a light emission surface. The reflection surface is provided with a dichroic mirror.