Curved Diffraction Grating Microstructures for Uniform Out-Coupling
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Solution Overview
Problem
Existing two-dimensional diffraction gratings in optical waveguides have limited design flexibility, difficulty in achieving uniform energy out-coupling, and high scattering due to straight edges and sharp vertices, which affect image contrast.
Innovation Solution
A diffraction grating with microstructure units featuring smooth closed curves and no sharp vertices, including valleys and protrusions, allows for adjustable parameters and uniform energy distribution, reducing scattering and improving image contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If microstructure units with straight edges and sharp corners (triangle or parallelogram) are used, then energy can be distributed across multiple diffraction orders for uniform energy distribution, but scattering increases and image contrast decreases
Solution Approach 1:
The patent applies curvature by replacing straight edges and sharp corners with smooth curved boundaries. The microstructure units feature boundaries formed by curved lines with controlled radius of curvature, eliminating sharp vertices while maintaining the ability to distribute energy across diffraction orders. This curved geometry reduces scattering effects while preserving uniform energy distribution properties.
Solution Approach 2:
The patent changes geometric parameters by introducing radius of curvature as a controllable parameter for the microstructure boundaries. By adjusting the radius of curvature and other geometric parameters, the design optimizes the balance between energy distribution uniformity and scattering reduction, achieving both goals simultaneously through parameter optimization.
2Ease of manufacture
If microstructure units with simple regular shapes (circle, ellipse) are used, then production is easier, but energy out-coupling is difficult to achieve
Solution Approach 1:
The patent changes the geometric parameters of microstructure units by introducing curved boundaries with specific radius of curvature values and asymmetric configurations. This modifies the simple circular or elliptical shapes into optimized curved geometries that maintain manufacturing simplicity while significantly improving energy out-coupling efficiency through controlled light diffraction patterns.
3Device complexity
If microstructure units with few adjustable parameters are used, then design is simpler, but design flexibility is limited
Solution Approach 1:
The patent introduces multiple adjustable geometric parameters including radius of curvature, boundary curve characteristics, and asymmetric shape parameters. These additional parameters provide extensive design flexibility for optimizing optical performance while maintaining relatively simple curved geometric forms that do not significantly increase manufacturing complexity.
Solution Approach 2:
The patent employs asymmetric curved boundary designs for microstructure units, breaking the symmetry of simple geometric shapes. This asymmetry provides additional design degrees of freedom for controlling light diffraction and energy distribution, enhancing design flexibility while the overall curved geometry remains manufacturable.
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 enhances design freedom, ensures uniform energy distribution, and reduces scattering, resulting in improved image contrast and viewing uniformity.
Implementation Method 1
two-dimensional diffraction grating
Data Source
Figure 1~2B
Figure 2C~3
Figure 4~5C
AI summary
Provided are a diffraction grating (10) and an optical waveguide apparatus and a display device including the diffraction grating (10). The diffraction grating (10) includes a substrate (1) and microstructure units (2). The microstructure units (2) are formed on the substrate (1) and arranged at intervals in two dimensional directions. A pattern formed by the orthographic projection of a microstructure unit (2) on the substrate (1) includes a first closed pattern (21). The boundary of the first closed pattern (21) is formed by a smooth closed curve such that the boundary has no sharp vertices. At least a first curve segment having a negative radius of curvature (211) is present on the boundary such that at least one valley is formed on the boundary. In this solution, the freedom of the microstructure design is increased, and the out-coupled energy can be more uniform, which helps to reduce scattering and thus improves the image contrast.