Waveguide Index-Matched Layers for Uniform Thickness Distribution
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Solution Overview
Problem
Existing augmented reality technologies face challenges in forming substrates with a thickness distribution at eyepiece areas, which affect the performance and design constraints of wearable display devices.
Innovation Solution
A waveguide substrate with an index-matched layer is formed, where the device slope of the second surface of the index-matched layer is substantially the same as the waveguide slope of the first surface, creating a uniform thickness distribution across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a waveguide substrate is used in augmented reality devices, then the device can display virtual images, but the substrate thickness varies across the eyepiece area causing performance issues
Solution Approach 1:
The patent applies local quality by creating a thickness distribution profile specifically in the eyepiece areas of the waveguide substrate. Different regions of the substrate have different thickness characteristics - the eyepiece areas have a controlled thickness variation while other areas maintain different properties. This is achieved through selective thinning or shaping processes that target specific regions, allowing the substrate to optimize optical performance in critical areas without compromising overall structural integrity.
Solution Approach 2:
The patent implements parameter changes by deliberately modifying the thickness parameter of the waveguide substrate across different regions. Rather than maintaining uniform thickness, the substrate thickness is varied as a controlled parameter to achieve desired optical characteristics. This includes creating gradient thickness profiles or specific thickness distributions in eyepiece areas to correct optical aberrations and improve image quality while managing the trade-off with manufacturing complexity.
2Reliability
If the substrate thickness is varied to improve optical performance, then image quality increases, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by establishing the thickness distribution profile during the substrate formation process itself, rather than attempting to correct thickness variations later. The waveguide substrate is manufactured with the desired non-uniform thickness profile built-in from the beginning, using techniques such as selective deposition, controlled etching, or molding processes that create the target geometry directly. This prevents the need for complex post-processing steps to achieve the required thickness distribution.
Solution Approach 2:
The patent utilizes parameter changes by treating substrate thickness as a controllable manufacturing parameter rather than a fixed specification. The manufacturing process is designed to intentionally vary thickness as a functional parameter, using techniques such as gradient deposition, selective removal, or variable pressure molding. This transforms the complexity from a defect to be corrected into a design feature to be controlled, improving optical performance while managing manufacturing complexity through deliberate parameter optimization.
Data Source
AI summary
Embodiments of the present disclosure generally relate to methods for forming a waveguide. Methods may include measuring a waveguide substrate, the waveguide having a substrate thickness distribution; and depositing an index-matched layer onto a surface of the waveguide, the index-matched layer having a first surface disposed on the waveguide substrate and a second surface opposing the first surface, wherein the index-matched layer is disposed only over a portion of the waveguide substrate, and a device slope of a second surface of the index-matched layer is substantially the same as the waveguide slope of the first surface of the waveguide.