Anisotropic Metasurface Image Combiner for Wide Viewing Angle AR
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Solution Overview
Problem
Existing augmented reality (AR) devices face challenges in achieving a wide viewing angle and high-quality images while maintaining a lightweight and compact design, particularly in the optical imaging system of AR glasses.
Innovation Solution
The implementation of an image combiner that includes a waveguide, an input-coupling element, and a folding/output-coupling element, where the folding/output-coupling element is an anisotropic metasurface with sub-metasurfaces configured to diffract light rays at different incidence angles, ensuring efficient light propagation and output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional waveguide-type image combiner uses free-form reflection or multi-mirror reflection or diffractive optical element (DOE) or holographic optical element (HOE), then light input and expansion/output is achieved, but viewing angle and image quality are limited and device weight and size increase
Solution Approach 1:
The folding/output-coupling element is divided into multiple sub-areas (first sub-area, second sub-area, etc.), each with dedicated sub-metasurfaces optimized for specific incidence angle ranges. This segmentation allows different portions of the optical system to handle different angular ranges efficiently, expanding the overall viewing angle while maintaining image quality.
Solution Approach 2:
Different sub-metasurfaces are designed with locally optimized properties: first sub-metasurface for rays with first incidence angle, second sub-metasurface for rays with second incidence angle. Each sub-metasurface has tailored diffraction efficiency and optical propagation characteristics for its specific angular range, achieving high image quality across the entire viewing angle spectrum.
2Adaptability or versatility
If anisotropic metasurface with multiple sub-metasurfaces is used in folding/output-coupling area, then wide viewing angle and uniform brightness are achieved, but manufacturing complexity increases
Solution Approach 1:
The metasurface structure utilizes parameter variations (rotation angles, sizes, shapes of nanostructures) across different sub-areas to achieve different diffraction efficiencies for different incidence angles. By systematically varying these parameters, the patent achieves wide viewing angle coverage and uniform brightness distribution while maintaining a consistent metasurface fabrication approach across the entire device.
3Loss of energy
If diffraction efficiency is optimized for specific incidence angles, then light loss is reduced, but optical propagation length varies causing brightness non-uniformity
Solution Approach 1:
Different sub-metasurfaces are designed with locally optimized diffraction efficiency for their specific incidence angle ranges. The first sub-metasurface optimizes for first incidence angle rays, the second sub-metasurface for second incidence angle rays, ensuring minimal light loss for each angular range while compensating for varying optical propagation lengths to achieve uniform overall brightness.
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 solution enhances the AR device's ability to provide a wide viewing angle and uniform brightness, reducing light loss and power consumption while maintaining a compact form factor.
Implementation Method 1
a first ray having a first incidence angle is diffracted by the first sub-metasurface to be directed to the eye box and a second ray having a second incidence angle, which is different from the first incidence angle, is diffracted by the second sub-metasurface to be directed to the eye box
Implementation Method 2
an image combiner including a waveguide, an input-coupling element, in an input-coupling area of the waveguide, configured to input light of a virtual image incident on the input-coupling area into the waveguide
Data Source
AI summary
Provided is an image combiner including a waveguide, an input-coupling element, in an input-coupling area of the waveguide, configured to input light of a virtual image incident on the input-coupling area into the waveguide, and a folding/output-coupling element, in a folding/output-coupling area of the waveguide, configured to form an eye box by outputting the light input into the waveguide out of the waveguide, wherein the folding/output-coupling element is an anisotropic metasurface including a first sub-metasurface and a second sub-metasurface in a first sub-area and a second sub-area, and wherein the anisotropic metasurface is configured such that among rays input through different areas of the input-coupling area, a first ray having a first incidence angle is diffracted by the first sub-metasurface to be directed to the eye box and a second ray having a second incidence angle is diffracted by the second sub-metasurface to be directed to the eye box.