Multimaterial Metasurfaces for Broadband Waveguide Light Redirection
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Solution Overview
Problem
Conventional augmented and virtual reality display systems struggle to provide a comfortable and realistic presentation of virtual image elements amidst real-world imagery due to mismatches between accommodative and vergence states, leading to user discomfort.
Innovation Solution
The use of a waveguide with an optical element featuring a metasurface composed of multiple materials with different refractive indices, configured to redirect light with precise control over scattering response, allowing for customized redirection and scattering of light across various wavelengths, thereby providing accurate vergence and accommodation cues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional display systems are used, then virtual image elements can be presented, but accommodative and vergence states mismatch occurs causing user discomfort
Solution Approach 1:
The patent employs metasurfaces composed of multiple materials with different refractive indices (e.g., high-index materials like silicon nitride or titanium dioxide combined with low-index materials like polymer or air) to create protrusions that precisely control light scattering. This composite structure enables accurate vergence and accommodation cues by manipulating the optical path of light rays, thereby resolving the mismatch between accommodative and vergence states while maintaining system manageability through a planar integration approach
2Manufacturing precision
If single-material metasurfaces are used, then manufacturing is simpler, but control over scattering response across wavelengths is insufficient
Solution Approach 1:
The patent applies different materials with distinct refractive indices to specific regions within the metasurface protrusions (e.g., high-index material for the core, low-index material for the surrounding layer or vice versa). This local differentiation of material properties enables precise control over the scattering response for different wavelengths, allowing the metasurface to simultaneously optimize performance across the visible spectrum while maintaining a manufacturable planar structure
3Measurement precision
If sub-wavelength spacing between protrusions is used, then light redirection precision is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent utilizes sub-wavelength spacing between metasurface protrusions (smaller than the wavelength of light, e.g., < 200 nm for visible light) to achieve precise light redirection and scattering control. By operating in the sub-wavelength regime, the metasurface can manipulate light at the nanoscale to create accurate vergence and accommodation cues. The planar integration approach and use of standard deposition techniques enable this high-precision structure to be manufactured despite the challenging dimensional requirements
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 enhances the realism and comfort of virtual reality experiences by aligning accommodative and vergence states, enabling a more believable simulation of depth perception.
Implementation Method 1
configured to redirect light with precise control over scattering response
Implementation Method 2
comprises a plurality of spaced-apart protrusions disposed on the waveguide. Each protrusion comprises a first vertical layer comprising a first material, and a second vertical layer comprising a second material different from the first material. The first material and the second material may have different refractive indices.
Data Source
AI summary
Display devices include waveguides with metasurfaces as in-coupling and/or out-coupling optical elements. The metasurfaces may be formed on a surface of the waveguide and may include a plurality or an array of sub-wavelength-scale (e.g., nanometer-scale) protrusions. Individual protrusions may include horizontal and/or vertical layers of different materials which may have different refractive indices, allowing for enhanced manipulation of light redirecting properties of the metasurface. Some configurations and combinations of materials may advantageously allow for broadband metasurfaces. Manufacturing methods described herein provide for vertical and/or horizontal layers of different materials in a desired configuration or profile.