TIR Waveguide Grating Diffraction for Expanded Angular Bandwidth
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Solution Overview
Problem
Waveguide gratings are limited by narrow angular bandwidths, which restrict the range of ray angles that can be efficiently guided, particularly in applications like near-eye displays and sensors, and current methods of stacking or multiplexing gratings are limited by holographic scatter and material modulation uniformity.
Innovation Solution
An optical waveguide with at least two TIR surfaces containing a grating that allows input TIR light to undergo at least two diffractions, with each ray and its corresponding diffracted ray offset by an angle less than half the diffraction efficiency bandwidth, enabling unique TIR angular ranges and expanded angular bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmission holographic gratings are used for in-coupling and out-coupling light in waveguides, then these functions are performed efficiently, but the narrow angular bandwidth imposes tighter angular limits on the image content that can be transmitted
Solution Approach 1:
The patent combines multiple gratings with different angular bandwidths into a single waveguide structure. Specifically, it merges a first grating with a first angular bandwidth and a second grating with a second angular bandwidth (where the second bandwidth is broader than the first) to create a composite grating system that achieves both high coupling efficiency and extended angular bandwidth for displaying broadband image content
Solution Approach 2:
The patent employs composite grating structures with different material properties and modulation characteristics. By integrating gratings with different pitch values, modulation depths, and material compositions into a single waveguide, the system achieves superior performance that neither individual grating could provide alone, resolving the contradiction between efficiency and angular bandwidth
2Adaptability or versatility
If multiple gratings are stacked or multiplexed to overcome angular limitations, then the angular bandwidth is expanded, but stacking is limited by holographic scatter and the number of gratings is limited by material modulation uniformity
Solution Approach 1:
The patent transitions from stacking multiple discrete grating layers to implementing a multiplexed grating structure where multiple gratings with different spatial frequencies are encoded within a single waveguide layer. This dimensional transformation allows the system to achieve expanded angular bandwidth without the cumulative scatter issues that arise from stacking multiple physical layers
Solution Approach 2:
The patent varies key grating parameters including pitch, modulation depth, and orientation angle across different grating elements within the multiplexed structure. By carefully controlling these parameter variations, the system expands angular bandwidth while maintaining material modulation uniformity and avoiding the limitations of stacking multiple gratings
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 significantly expands the angular bandwidth of waveguide gratings, allowing for improved performance in display and sensor applications by ensuring high diffraction efficiency and minimizing overlap in diffraction efficiency versus angle characteristics, thereby enhancing the range of ray angles that can be guided.
Implementation Method 1
input TIR light with a first angular range along a first propagation direction undergoes at least two diffractions, wherein each ray from the first angular range and its corresponding diffracted ray lie on the diffraction cone of the grating
Implementation Method 2
an optical waveguide with least two TIR surfaces containing a grating. Input TIR light with a first angular range along a first propagation direction
Data Source
AI summary
An optical waveguide comprises at least two TIR surface and contains a grating. Input TIR light with a first angular range along a first propagation direction undergoes at least two diffractions at the grating. Each diffraction directs light into a unique TIR angular range along a second propagation direction.