Multi-Material Metasurfaces for Natural AR/VR Depth Cues
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Solution Overview
Problem
Conventional augmented and virtual reality display systems often cause discomfort due to a mismatch between accommodative and vergence states, leading to an unnatural perception of depth.
Innovation Solution
The use of metasurfaces with multiple materials and precise layering in waveguides to provide controlled redirection and scattering of light, allowing for accurate simulation of depth planes with matching accommodative and vergence cues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional display systems present digital image information without transparency to other actual real-world visual input (VR scenario), then virtual image information is clearly presented, but the perception of depth becomes unnatural due to mismatch between accommodative and vergence states
Solution Approach 1:
The patent segments the optical path into multiple layers including a waveguide layer with outcoupling optical elements and a metasurface layer with light-redirecting structures. This segmentation allows independent optimization of each layer to simultaneously achieve clear virtual image presentation and natural depth perception by controlling light redirection at different stages.
Solution Approach 2:
The metasurface incorporates multiple materials with different refractive indices at different locations within the light-redirecting structures. This local variation in material properties enables precise control of light redirection angles and paths, allowing the system to provide both clear virtual images and accurate accommodative-vergence matching for natural depth perception.
2Manufacturing precision
If metasurfaces with multiple materials and precise layering are used to provide controlled redirection and scattering of light, then accurate simulation of depth planes with matching accommodative and vergence cues is achieved, but device complexity increases
Solution Approach 1:
The patent implements a nested structure where the metasurface layer is integrated onto the waveguide substrate, with light-redirecting structures containing multiple material layers embedded within the waveguide optical system. This nesting approach achieves complex light manipulation functions while maintaining a compact overall device structure.
Solution Approach 2:
The metasurface utilizes composite materials consisting of multiple layers with different refractive indices (e.g., high-index material and low-index material) within each light-redirecting structure. This composite material approach enables precise control of light redirection and scattering properties to achieve accurate depth plane simulation while managing the inherent complexity through material science solutions.
3Manufacturing precision
If light-redirecting structures with multiple materials are fabricated using sequential deposition, then precise control of layer composition and thickness is achieved, but fabrication time and process complexity increase
Solution Approach 1:
The fabrication process uses preliminary patterning steps to define the footprint and geometry of light-redirecting structures before material deposition. This preliminary action enables subsequent selective deposition of multiple materials only in required locations, reducing overall fabrication time while maintaining precise layer composition control through pre-planned material placement sequences.
Solution Approach 2:
The sequential deposition process utilizes parameter changes in the deposition conditions (such as temperature, pressure, and deposition rate) to control the composition and thickness of each material layer. By dynamically adjusting these parameters during the deposition sequence, the process achieves precise layer composition control while optimizing fabrication time through efficient process parameter management.
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 three-dimensional imagery by aligning accommodative and vergence states, providing a more natural depth perception experience.
Implementation Method 1
forming a pattern of periodically repeating optical structures configured to diffract visible light. The optical structures have a second refractive index greater than the first refractive index
Implementation Method 2
exposing the substrate to a metal precursor followed by an oxidizing precursor. Exposing the substrate is performed under a pressure and at a temperature such that an inorganic material comprising the metal of the metal precursor is incorporated into the periodically repeating polymer structures
Implementation Method 3
exposing the substrate to a metal precursor followed by an oxidizing precursor
Data Source
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Figure 3A~3C
AI summary
Display devices include waveguides with metasurfaces as in-coupling and/or outcoupling 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.