Metasurface Optical Combiner for Wider AR Field of View
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Solution Overview
Problem
Conventional optical combiners in augmented reality (AR) display technology suffer from a small field of view, low ambient light transmittance, and low image uniformity due to reflection and transmission principles that lead to issues like small virtual image field of view and color crosstalk.
Innovation Solution
An optical combiner with a metasurface layer on a transparent substrate, featuring metasurface units with varying spacings and angles, designed to reflect narrow-linewidth optical signals for virtual images and transmit broad-linewidth ambient light, enhancing field of view and image uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a non-diffractive optical element (beam splitter) is used to reflect virtual image and transmit real scene, then the structure is simple, but the field of view is small and ambient light transmittance is low
Solution Approach 1:
The optical combiner is divided into multiple regions (first region and second region) with different optical characteristics. The first region has high reflectivity for virtual images while the second region has high transmittance for ambient light, allowing both functions to coexist without compromising either field of view or ambient light transmittance
Solution Approach 2:
Different regions of the optical combiner are assigned different local optical properties. The first region is optimized for reflecting virtual image light with high reflectivity, while the second region is optimized for transmitting ambient light with high transmittance, thereby resolving the contradiction between simplicity and performance
2Illumination intensity
If optical gratings or reliefs with diffraction function are used, then the field of view increases, but color crosstalk occurs and image uniformity deteriorates
Solution Approach 1:
The optical combiner is segmented into different functional regions that avoid the use of diffraction gratings altogether. By using reflection-based optical elements in the first region and transmission-based elements in the second region, the patent eliminates color crosstalk while maintaining an expanded field of view
Solution Approach 2:
The patent replaces diffraction-based optical gratings with reflection-based optical elements. This substitution eliminates the wavelength sensitivity inherent in diffraction gratings, thereby preventing color crosstalk and improving image uniformity while still achieving an expanded field of view
3Illumination intensity
If diffraction elements are used to couple light to waveguide, then the virtual image field of view increases, but ambient light transmittance decreases
Solution Approach 1:
The optical combiner is divided into a first region optimized for virtual image reflection and a second region optimized for ambient light transmission. This segmentation allows the virtual image field of view to be expanded in the first region without compromising ambient light transmittance in the second region
Solution Approach 2:
Different regions are assigned different local optical qualities: the first region has high reflectivity for virtual images while the second region has high transmittance for ambient light, resolving the energy loss contradiction
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 increases the field of view and ambient light transmittance while improving image uniformity, reducing power consumption, and enhancing privacy by reflecting virtual images effectively.
Implementation Method 1
the optical combiner is implemented through reflection and transmission of light. A non-diffractive optical element (for example, a beam splitter) is used to reflect a virtual image optical signal
Implementation Method 2
transmit visible light in a real scene at the same time
Implementation Method 3
the optical combiner is implemented through diffraction and transmission of light. Two optical elements (for example, optical gratings or reliefs) with a diffraction function are used
Implementation Method 4
the metasurface layer includes a plurality of regions, and optical signals corresponding to different regions have different emergent angles, so that optical signals emergent at different angles converge to one point
Data Source
Figure 1~2a
Figure 2b~2c
Figure 3a~3b
AI summary
This application provides an optical combiner (101, 301, or 400) and a related device for augmented reality. The optical combiner (101, 301, or 400) includes a transparent substrate (202 or 402) and a metasurface layer (201 or 401). The metasurface layer (201 or 401) is disposed on a surface of the transparent substrate (202 or 402). The metasurface layer (201 or 401) includes a plurality of metasurface units (403) arranged two-dimensionally. A spacing between two adjacent metasurface units (403) in the plurality of metasurface units (403) gradually changes along one or two dimensions, and a relative angle between any two adjacent metasurface units (403) is not zero. The optical combiner (101, 301, or 400) can increase an ambient light transmittance and increase uniformity and a field of view of an image.