Input Coupling Grating Unit Cells for Waveguide Displays
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Solution Overview
Problem
Waveguide-based displays for augmented and mixed reality applications face challenges in coupling efficiency due to larger input pupil sizes, leading to increased specular reflection and diffraction losses, which existing solutions fail to adequately address.
Innovation Solution
The implementation of an input coupling grating (ICG) with a plurality of unit cells, each having photonic structures arranged at a consistent pitch but with unique structural characteristics to optimize diffraction and specular reflection efficiencies, and the use of a high refractive index coating to control these efficiencies across different wavelengths for color multiplexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If larger input pupil sizes are used in waveguide-based displays, then the display can accommodate larger eye boxes and improve user comfort, but coupling efficiency decreases due to increased specular reflection and diffraction losses
Solution Approach 1:
The patent applies local quality by dividing the input coupling grating into multiple unit cells, where each unit cell has photonic structures with specific structural characteristics optimized for local light coupling. This allows different regions of the grating to be tailored for optimal performance at large pupil sizes, reducing specular reflection and diffraction losses while maintaining high coupling efficiency across the entire aperture.
Solution Approach 2:
The patent employs parameter changes by varying the structural characteristics of photonic structures across different unit cells, such as changing pitch, depth, or shape parameters. This enables optimization of diffraction and specular reflection efficiencies for each unit cell, thereby improving overall coupling efficiency while supporting large input pupil sizes.
2Device complexity
If existing ICG designs are used with large pupil sizes, then device simplicity is maintained, but color multiplexing performance deteriorates due to insufficient control over diffraction and specular reflection efficiencies at different wavelengths
Solution Approach 1:
The patent applies local quality by assigning different structural characteristics to photonic structures in different unit cells, enabling wavelength-selective optimization. Each unit cell can be designed with specific parameters that favor certain wavelengths, allowing effective color multiplexing while keeping the overall grating structure relatively simple and manufacturable.
Solution Approach 2:
The patent segments the input coupling grating into multiple unit cells, each capable of being independently optimized for specific wavelengths. This segmentation enables color multiplexing functionality without requiring a completely complex structure, as each unit cell can be designed with moderate complexity tailored to its wavelength requirements.
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 coupling efficiency of the ICG for large pupil sizes and color multiplexing, reducing losses and improving the overall image quality by tuning the diffraction and specular reflection efficiencies across the ICG area.
Implementation Method 1
The photonic structures of at least one first unit cell have at least one different structural characteristic than the photonic structures of at least one second unit cell
Implementation Method 2
optimize diffraction and specular reflection efficiencies
Implementation Method 3
The implementation of an input coupling grating (ICG) with a plurality of unit cells, each having photonic structures arranged at a consistent pitch but with unique structural characteristics to optimize diffraction and specular reflection efficiencies, and the use of a high refractive index coating to control these efficiencies across different wavelengths for color multiplexing
Data Source
AI summary
An input coupling grating (ICG) for a waveguide-based display comprises an input region that receives light and a plurality of unit cells. Each unit cell includes photonic structures arranged at a pitch. The photonic structures of at least one first unit cell have at least one different structural characteristic than the photonic structures of at least one second unit cell.