Metasurface Diffraction Gratings for AR Waveguide Focus Cues
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Solution Overview
Problem
Existing AR and VR technologies face challenges in providing a comfortable and natural-feeling presentation of virtual image elements amidst real-world imagery, often leading to discomfort due to misalignment between accommodation and vergence cues.
Innovation Solution
The use of metasurfaces configured to diffract visible light, incorporating nanobeams arranged in specific orientations to manipulate light propagation and enhance diffraction efficiency, allowing for compact optical elements that integrate virtual content with real-world views.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical systems are used for AR/VR displays, then the system can present virtual image elements, but the accommodation-vergence mismatch causes user discomfort
Solution Approach 1:
The patent changes the optical parameters by using metasurfaces with specifically designed nanobeams that create accurate focus cues, thereby resolving the accommodation-vergence mismatch and improving user comfort without significantly increasing system complexity
Solution Approach 2:
The patent employs composite metasurface structures combining different nanobeam orientations and materials to achieve both high diffraction efficiency and accurate focus control, simultaneously addressing multiple performance requirements
2Productivity
If metasurfaces with nanobeams are used to diffract light, then high diffraction angles and efficiencies are achieved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent segments the metasurface into multiple nanobeam elements with different orientations, where each segment contributes to specific diffraction orders. This segmentation allows independent optimization of each nanobeam while maintaining overall manufacturing feasibility through modular fabrication processes
Solution Approach 2:
The patent applies local quality by assigning different orientations and properties to different nanobeam segments within the metasurface, enabling localized control of diffraction characteristics while maintaining compatibility with standard manufacturing techniques
3Measurement precision
If multiple nanobeam orientations are incorporated in the metasurface, then wavelength selectivity is enhanced, but the device complexity increases
Solution Approach 1:
The patent designs the metasurface so that nanobeams with different orientations serve multiple functions: they simultaneously control diffraction angles, enhance wavelength selectivity, and maintain compatibility with existing fabrication processes, thereby achieving multi-functionality without proportional increases in 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
This approach enables a more realistic and comfortable AR experience by aligning accommodation and vergence cues, providing high diffraction angles and efficiencies, and allowing for high wavelength selectivity and compact optical designs.
Implementation Method 1
a metasurface configured to diffract visible light having a wavelength
Implementation Method 2
Polarization dependent focusing lens by use of quantized Pancharatnam-Berry phase diffractive optics
Implementation Method 3
one or more first nanobeams and a plurality of second nanobeams arranged to diffract light at a different angle
Implementation Method 4
cause the diffracted light to propagate in the substrate under total internal reflection
Implementation Method 5
a spatial light modulator configured to modulate the light from the light source
Data Source
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AI summary
Metasurfaces provide compact optical elements in head-mounted display systems to, e.g., incouple light into or outcouple light out of a waveguide. The metasurfaces may be formed by a plurality of repeating unit cells, each unit cell comprising two sets or more of nanobeams elongated in crossing directions: one or more first nanobeams elongated in a first direction and a plurality of second nanobeams elongated in a second direction.