In-Coupler Grating Line Offset for AR Waveguide Aberration
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Solution Overview
Problem
Augmented reality waveguide displays face issues with blurry virtual images due to projector output imperfections, such as phase deviations from flat wavefronts, which degrade the modulation transfer function and sharpness, making small text or lines unreadable.
Innovation Solution
Implementing a grating line offset (GLO) in the in-coupler (IC) of the waveguide to apply phase shifts to the diffracted light, compensating for projector aberrations by calculating phase offsets based on measured wavefront deviations across multiple wavelengths and field of view points, and applying these offsets to specific grating lines to redirect light through the waveguide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional in-coupler is used without grating line offset, then the device complexity is low, but the image sharpness and modulation transfer function are degraded due to projector phase deviations
Solution Approach 1:
The patent applies different grating line offsets to different regions of the in-coupler grating structure. Specifically, the in-coupler includes a first grating line offset for a first region and a second grating line offset for a second region, allowing each region to be optimized for its specific field of view requirements. This local differentiation improves image sharpness and modulation transfer function without requiring complete redesign of the entire system.
Solution Approach 2:
The in-coupler is segmented into multiple regions (first region, second region, etc.), each with its own optimized grating line offset. This segmentation allows the system to address phase deviations at different field of view points independently, improving overall image quality while maintaining a manageable structural complexity through modular design.
2Reliability
If grating line offset is applied to compensate for phase deviations, then the modulation transfer function is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent calculates and determines the optimal grating line offsets before the actual manufacturing process. By pre-calculating the required offsets based on measured wavefront deviations and phase errors, the system establishes precise manufacturing targets in advance. This preliminary action allows manufacturers to fabricate gratings with specific offset values, improving modulation transfer function while providing clear manufacturing guidance.
Solution Approach 2:
The patent replaces complex mechanical adjustment mechanisms with a fixed grating line offset structure. Instead of using movable or adjustable components to compensate for phase deviations, the solution embeds the compensation directly into the grating geometry through predetermined offsets. This substitution simplifies the manufacturing process while maintaining reliable modulation transfer function performance.
3Adaptability or versatility
If multiple grating line offsets are used for different field of view points, then the adaptability is improved, but the device complexity increases
Solution Approach 1:
The patent implements region-specific grating line offsets where each region of the in-coupler is optimized for its corresponding field of view point. The in-coupler includes a first grating line offset for a first region and a second grating line offset for a second region, allowing the system to adapt to different field of view requirements while maintaining a unified grating structure. This approach improves adaptability without requiring multiple separate components.
Solution Approach 2:
The patent merges multiple field of view compensations into a single integrated in-coupler structure. By combining multiple grating line offsets within one grating element, the system achieves adaptability across different field of view points while avoiding the complexity of multiple separate optical components. The unified structure simplifies alignment and reduces the overall device complexity.
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 effectively reduces the effects of projector aberrations, resulting in a sharper virtual image by compensating for phase deviations, thereby improving the modulation transfer function and user experience in augmented reality displays.
Implementation Method 1
An in-coupler (IC) of a waveguide combiner diffracts light from a projector into total internal reflection (TIR)
Implementation Method 2
diffracts light from a projector into total internal reflection (TIR)
Data Source
AI summary
Certain aspects of the present disclosure include an optical device. The optical device generally includes an in-coupler (IC) configured to receive light from a projector, where the IC includes at least one grating line offset (GLO) associated with one or more phase deviations of the light from the projector. The device also includes a waveguide and an output coupler (OC), where the IC is configured to redirect the light from the projector to the OC through the waveguide.