See-through reflective metasurface for head-worn displays
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Solution Overview
Problem
Existing reflective metasurface devices with optically thick metal backplates are not suitable for head-worn displays as they obscure the user's view of the real world, and previous solutions like perforated metasurfaces generate undesirable diffraction artifacts.
Innovation Solution
A see-through reflective optical device with a sub-wavelength periodic arrangement of meta-atoms, featuring a patterned optically thin metal layer, an optically thick metal layer, and an insulator layer, along with an array of apertures of random positions and diameters, allowing for controlled light transmission while maintaining reflection functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optically thick metal backplate is used in reflective metasurface, then the phase control capability is improved, but the transparency of the device deteriorates
Solution Approach 1:
The device is segmented into two distinct metal layers: an optically thick metal backplate for phase control and an optically thin metal patterned layer for wavelength selection. This segmentation allows each layer to perform its specific function without compromising the other, resolving the contradiction between phase control capability and transparency.
Solution Approach 2:
The patent applies local quality by creating a patterned arrangement of meta-atoms with varying local optical properties. The optically thin metal layer is strategically positioned and patterned to provide wavelength-specific reflection while maintaining overall device transparency, allowing different regions to serve different optical functions.
2Illumination intensity
If perforations are introduced to improve transparency, then the see-through ratio is improved, but diffraction artifacts are generated
Solution Approach 1:
Instead of introducing perforations that create diffraction artifacts, the patent extracts the wavelength selection function into a separate optically thin metal patterned layer. This layer selectively reflects unwanted wavelengths while allowing visible light to pass through, achieving transparency without the harmful diffraction effects associated with perforated structures.
Solution Approach 2:
The optically thin metal patterned layer acts as a disposable filtering element that absorbs or reflects specific wavelengths. This layer can be optimized for wavelength selection without concern for long-term structural integrity, as it serves primarily as a spectral filter rather than a structural component.
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 enables a high see-through ratio without introducing undesirable diffraction artifacts, allowing for effective wavefront control and optical aberration correction, making it suitable for head-worn displays and other optical systems.
Implementation Method 1
patterned isolated gap surface plasmon (GSP) resonators
Implementation Method 2
successful implementation of reflective diffraction gratings using metal-dielectric-metal metasurfaces
Implementation Method 3
an array of apertures of random positions and diameters greater than the targeted design wavelength formed through the reflective metasurface providing a designed percentage of light transparency
Implementation Method 4
the ability to produce spatially varying phase change (i.e. wavefront reshaping), amplitude modulation and polarization conversion of incident light over subwavelength dimensions
Data Source
AI summary
A see-through reflective optical device includes: a reflective metasurface configured for a targeted design optical wavelength, wherein the reflective metasurface comprises a sub-wavelength periodic arrangement of meta-atoms formed by patterned isolated gap surface plasmon (GSP) resonators, where the patterned isolated GSP resonators comprise a patterned optically thin metal layer for the design wavelength, an optically thick metal layer for the design wavelength, and an insulator layer between the patterned optically thin metal layer and the optically thick metal layer; and an array of apertures of random positions and diameters greater than the targeted design wavelength formed through the reflective metasurface providing a designed percentage of light transparency through the reflective metasurface. The reflective metasurface of the see-through reflective optical device may comprise, e.g., a reflective diffraction grating metasurface, and may be used as a combiner element surface in a near eye display assembly.