Waveguide Display Grating Layout for Wavelength Cross-Coupling
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Solution Overview
Problem
Cross-coupling of different wavelength bands of light occurs in waveguide display assemblies, leading to image clarity and color uniformity issues due to overlap between in-coupling gratings, which negatively affect the quality of virtual images displayed to the user.
Innovation Solution
Incorporation of diffractive grating elements along the waveguide to selectively diffract unintended wavelength bands out of the waveguide, while allowing intended wavelength bands to mitigate the negative effects of cross-coupling, and the use of color-specific filters to further manage light propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple waveguides are used for different wavelength bands, then wavelength-specific light transmission is improved, but cross-coupling between wavelength bands occurs causing image clarity and color uniformity issues
Solution Approach 1:
The patent extracts and removes cross-coupled light from the waveguide system by introducing diffractive gratings that selectively diffract unintended wavelength bands out of the waveguide, separating the harmful cross-coupled light from the intended light path
Solution Approach 2:
The patent introduces diffractive gratings as intermediary elements between the in-coupling and out-coupling gratings. These gratings act as mediators that selectively interact with specific wavelength bands, diffracting unintended wavelengths while allowing intended wavelengths to pass through to maintain image clarity
2Measurement precision
If diffractive gratings are added to mitigate cross-coupling, then image clarity is improved, but device complexity increases
Solution Approach 1:
The patent merges the diffractive grating elements directly into the waveguide structure, integrating multiple functions (light steering, wavelength separation, and cross-coupling mitigation) into a single integrated component rather than adding separate external elements
Solution Approach 2:
The diffractive gratings perform multiple functions simultaneously: they diffract unintended wavelength bands out of the waveguide, guide intended wavelength bands to the out-coupling grating, and maintain overall light transmission efficiency, reducing the need for additional separate components
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
Enhances image clarity and accuracy by minimizing the impact of cross-coupled light, without significantly increasing device weight, size, or complexity, and allows for a larger field-of-view and compatibility with diverse user eye shapes and sizes.
Implementation Method 1
an in-coupling grating configured to in-couple light of a first wavelength band emitted by a light source into the waveguide
Implementation Method 2
cause propagation of the light of the first wavelength band through the waveguide via total internal reflection
Implementation Method 3
one or more diffractive gratings disposed along an optical path between the in-coupling grating and the out-coupling grating, the one or more diffractive gratings configured to diffract light outside the first wavelength band out of the waveguide
Implementation Method 4
an out-coupling grating configured to out-couple the light of the first wavelength band from the waveguide and toward a user eye
Data Source
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AI summary
A waveguide display assembly comprises a waveguide, including an in-coupling grating configured to in-couple light of a first wavelength band emitted by a light source into the waveguide, and cause propagation of the light of the first wavelength band through the waveguide via total internal reflection. An out-coupling grating is configured to out-couple the light of the first wavelength band from the waveguide and toward a user eye. One or more diffractive gratings are disposed along an optical path between the in-coupling grating and the out-coupling grating, the one or more diffractive gratings configured to diffract light outside the first wavelength band out of the waveguide and away from the user eye.