Lens Stack Coatings for Waveguide Moisture Control
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Solution Overview
Problem
Moisture accumulation on the surfaces of waveguides and lens stacks interferes with light propagation, particularly in augmented reality devices, leading to interruptions in the display of virtual images.
Innovation Solution
Application of hydrophilic and hydrophobic coatings on the surfaces of waveguides and lenses within a lens stack to manage moisture, where hydrophobic coatings repel moisture and create barriers, while hydrophilic coatings direct moisture away from critical areas, preventing accumulation and ensuring uninterrupted light propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If moisture is present on waveguide surfaces, then light propagation is blocked and virtual image display is interrupted, but adding hydrophobic and hydrophilic coatings increases device complexity
Solution Approach 1:
The waveguide surface is divided into regions with different coating properties: hydrophobic coating applied to specific areas (e.g., edges, grating regions) to repel moisture, and hydrophilic coating applied to other areas to draw moisture away. This localized differentiation protects critical optical regions while managing moisture distribution across the surface.
Solution Approach 2:
The waveguide incorporates a composite coating system combining two distinct materials with complementary properties: hydrophobic material (e.g., fluorinated compounds, silicon oxide) and hydrophilic material (e.g., silicon nitride, aluminum oxide). This composite approach leverages the strengths of each material to achieve comprehensive moisture protection.
2Object-affected harmful factors
If hydrophobic coating is applied to repel moisture, then moisture barrier effectiveness improves, but manufacturing precision requirements increase
Solution Approach 1:
The coating application process is segmented into distinct zones corresponding to different functional regions of the waveguide. Hydrophobic coating is applied to specific segments (e.g., peripheral regions, grating areas) while hydrophilic coating is applied to other segments. This segmentation allows each region to be optimized independently and simplifies the manufacturing process by using standardized coating techniques for each zone.
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 coatings effectively prevent moisture from interfering with light propagation, maintaining the clarity and integrity of virtual image display by directing moisture away from critical surfaces and structures within the lens stack.
Implementation Method 1
a hydrophobic coating at least disposed adjacent to a top edge of the at least one grating relative to a user's eye
Implementation Method 2
a hydrophilic coating disposed over the first surface between the hydrophobic coating and an edge of the substrate
Data Source
AI summary
Embodiments of the present disclosure relate to optical devices. More specifically, embodiments described herein have a lens stack including a waveguide, the lens stack having at least one surface partially coated with a hydrophobic and/or hydrophobic coating. In some embodiments, the hydrophobic and/or hydrophilic coatings are disposed over portions of the waveguide surface. In some embodiments, the hydrophobic and/or hydrophilic coatings are disposed over portions of the lens surfaces. In some embodiments, hydrophobic coatings prevent moisture from interacting with certain surfaces on the waveguide and hydrophilic coatings direct moisture away from those certain surfaces.