Metasurface Stack for AR See-Through Display
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Solution Overview
Problem
Near-eye visors for augmented reality systems face challenges with chromatic aberrations due to diffractive optical elements and limited angular field-of-view, which affect the immersive experience and form factor.
Innovation Solution
A see-through display utilizing a stack of metasurface layers configured to couple broadband light into a single waveguide, reducing chromatic aberrations and providing a spectrally-uniform field of view, with each layer designed to resonate at specific spectral bands, allowing for full color imaging and efficient light coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If diffractive optical elements (DOEs) or holographic optical elements (HOEs) are used to couple light in and out of a waveguide, then the form factor is reduced, but large chromatic aberrations occur
Solution Approach 1:
The patent divides the optical element into multiple discrete layers, each layer being optimized for a specific wavelength range. This segmentation allows each layer to handle specific colors (red, green, blue) separately, eliminating the chromatic aberrations that occur when a single diffractive element tries to handle the entire visible spectrum simultaneously.
Solution Approach 2:
The patent uses a composite structure consisting of multiple layers with different optical properties. Each layer is designed with specific refractive indices and thicknesses to optimize coupling for its designated wavelength range. This composite approach combines the advantages of different materials and designs to achieve broadband operation without chromatic aberrations.
2Ease of manufacture
If conventional diffractive gratings are used for light coupling, then the device is easier to manufacture, but the field of view becomes wavelength-dependent and disperse
Solution Approach 1:
By segmenting the optical element into multiple wavelength-specific layers, each layer can be designed to provide a uniform field of view for its specific wavelength range. When combined, these layers provide uniform FOV across the entire visible spectrum, eliminating the wavelength-dependent dispersion of conventional single-layer diffractive gratings.
3Volume of moving object
If a single waveguide is used with multiple metasurface layers, then the display width is reduced, but the chromatic behavior must be precisely controlled
Solution Approach 1:
Segmenting the broadband coupling task into multiple wavelength-specific layers simplifies the chromatic control requirement for each individual layer. Each layer only needs to be precision-controlled for its specific wavelength range, making the overall manufacturing more feasible despite the multiple layers required.
Solution Approach 2:
The patent systematically varies key parameters (refractive index, layer thickness, nanostructure geometry) across different layers to optimize each for its target wavelength range. This parameter optimization approach enables precise chromatic control while maintaining manufacturability.
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 enhances the form factor and chromatic behavior of near-eye visors, providing a more immersive experience with reduced width and improved coupling efficiency, while maintaining transparency and enabling gaze tracking through infrared or near-infrared radiation.
Implementation Method 1
Each layer in the MS stack may act as provide a resonant response at a defined spectral band and may be designed to couple a relatively narrow band surrounding a center wavelength of choice
Implementation Method 2
a waveguide (WG) configured to direct the coupled light to a user's eye
Data Source
AI summary
An optical system for a see-through display includes a stack of metasurface layers configured to receive light constituting an image; and a waveguide coupled to the stack. Each layer in the stack of metasurface layers is configured to provide a resonant response to an optical field at a different spectral band and to couple the resonant response with a waveguide. The waveguide is configured to propagate the different spectral bands in a direction of a user's eye.