Encapsulated Waveguide Structure for Pressure-Stable Near-Eye Displays
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Solution Overview
Problem
Optical waveguide systems in near-eye displays are susceptible to environmental contamination and distortion due to variations in ambient pressure and temperature, leading to image aberration and loss of sharpness.
Innovation Solution
An encapsulated waveguide system with first and second outer layers enclosing the waveguide substrate, sealed by a sealing element and spacers, creating identical pressure conditions in the cavities to protect against ambient pressure changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the waveguide system is left open to the environment, then the device complexity is reduced, but the optical performance deteriorates due to environmental contamination and pressure variations
Solution Approach 1:
The waveguide system is divided into separate functional layers (input area, output area, waveguide substrate) that are independently manufactured and then assembled. This segmentation allows each layer to be optimized separately while maintaining overall optical performance, and facilitates the creation of a sealed encapsulated structure without excessive complexity.
Solution Approach 2:
A sealing element in the form of a thin film or flexible seal is used to encapsulate the waveguide system, creating a protective barrier against environmental contamination and pressure variations. This thin film sealing approach maintains optical performance while avoiding the need for complex rigid encapsulation structures.
2Reliability
If the waveguide system is encapsulated with sealed outer layers, then the reliability against environmental contamination is improved, but the device complexity increases
Solution Approach 1:
The sealing function is merged with the existing outer layers of the waveguide system. The first and second outer layers serve both as protective encapsulation and as structural components of the optical system, eliminating the need for separate complex sealing mechanisms and reducing overall device complexity.
Solution Approach 2:
The outer layers are designed to serve multiple functions simultaneously: they provide structural support for the waveguide system, act as sealing barriers against environmental contamination, and maintain the optical path. This multi-functionality reduces the need for additional dedicated sealing components.
3Manufacturing precision
If spacers are used to maintain cavity pressure equality, then the optical distortion is prevented, but the manufacturing precision requirements increase
Solution Approach 1:
The spacers are pre-positioned and integrated into the encapsulation structure during the manufacturing process, establishing the correct cavity spacing before final assembly. This preliminary positioning ensures that the cavities maintain equal pressure and prevents optical distortion without requiring complex real-time adjustment mechanisms.
Solution Approach 2:
The spacers act as intermediary elements between the waveguide substrate and the outer layers, maintaining a precise and uniform distance that ensures equal cavity pressure. These spacers mediate the mechanical stresses and maintain the optical geometry without requiring direct contact or complex alignment between the substrate and outer layers.
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 system maintains optical performance by preventing distortion of input and output areas, ensuring clear and undistorted image projection despite environmental changes.
Implementation Method 1
The projector light is coupled in by the input area into the transparent waveguide substrate, then propagates along said substrate via total internal reflection until being coupled out from said substrate by the output area towards the user's eye
Implementation Method 2
The input area and the output area are typically made of a refractive index matched spin coated polymer layer on the transparent waveguide substrate surface that may be embossed by a master mold and cured by UV light (nano-imprinting), or exposed to UV through a mask and etched via a chemical process that discriminates between exposed and unexposed areas (nano-lithography), so as to form nanometer-sized patterns able to diffract light in a controlled manner
Data Source
Figure 1A~1B
Figure 1C
Figure 2A
AI summary
An encapsulated waveguide system for a near eye optical display includes a first outer layer (24), a second outer layer (31), at least one waveguide substrate (26) comprising an input area (27) and an output area (28), a first spacer and a sealing element (22). The at least one waveguide substrate (26) is disposed between the first and second outer layers (24, 31) and spaced therefrom by the first spacer. The sealing element (22) joins edges of the first and second outer layers (24, 31) so as to encapsulate the at least one waveguide substrate (26) within a cavity (25, 29) formed by the first and second outer layers (24, 31). The formed cavity includes a first cavity (25) between the at least one waveguide substrate (26) and the first outer layer (24) and a second cavity (29) between the at least one waveguide substrate (26) and the second outer layer (31).