Oriented Nanobeam Metasurface Gratings for Wide-FOV AR Waveguides
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Solution Overview
Problem
Challenges exist in creating augmented reality (AR) technology that seamlessly integrates virtual image elements with real-world imagery, providing a comfortable and natural-feeling experience.
Innovation Solution
The use of metasurfaces with nanobeams arranged in specific orientations and spacings to diffract visible light, integrated into head-mounted display devices, allowing for the projection of augmented reality image content while maintaining a view of the environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional optical elements are used in head-mounted displays, then the display can function, but the optical path is blocked and the field of view is limited
Solution Approach 1:
The patent replaces conventional mechanical optical elements (lenses, mirrors) with a metasurface that uses sub-wavelength nanobeams to control light propagation. This substitution eliminates the need for bulky optical components that block the optical path, enabling a wider field of view while maintaining compact form factor.
Solution Approach 2:
The metasurface operates in the sub-wavelength dimension, using nanobeams with dimensions smaller than the wavelength of light to achieve precise control over light propagation. This dimensional approach allows the optical element to be extremely thin while providing sophisticated light manipulation capabilities.
2Area of stationary object
If the metasurface uses sub-wavelength nanobeams, then the optical path is unblocked and field of view is expanded, but manufacturing precision requirements increase
Solution Approach 1:
The metasurface is divided into discrete nanobeams arranged in specific patterns, where each nanobeam can be independently fabricated and controlled. This segmentation allows for modular manufacturing and precise control over the optical properties of each element, facilitating accurate fabrication despite the sub-wavelength dimensions.
3Productivity
If nanobeams are spaced at sub-wavelength distances, then diffraction efficiency is improved, but fabrication complexity increases
Solution Approach 1:
The patent optimizes the spacing and dimensions of nanobeams to sub-wavelength values to achieve high diffraction efficiency. By carefully controlling these geometric parameters, the metasurface achieves superior optical performance while the fabrication complexity is managed through standardized nanofabrication processes.
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
Enhances the integration of virtual and real-world imagery by diffracting light to propagate under total internal reflection, providing a more immersive AR experience.
Implementation Method 1
a metasurface configured to diffract visible light having a wavelength
Implementation Method 2
cause the diffracted light to propagate in the substrate under total internal reflection
Data Source
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. As seen in a top-down view, the first direction may be along a y-axis, and the second direction may be along an x-axis. The unit cells may have a periodicity in the range of 10 nm to 1 μm, including 10 nm to 500 nm or 300 nm to 500 nm. Advantageously, the metasurfaces provide diffraction of light with high diffraction angles and high diffraction efficiencies over a broad range of incident angles and for incident light with circular polarization.