Optical Waveguide Anti-Contaminant Layer for See-Through Displays
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Solution Overview
Problem
Optical waveguides in applications like HUD and HMD suffer from reduced bandwidth and image degradation due to contaminants on the air-waveguide interface, leading to light scattering and efficiency loss.
Innovation Solution
Incorporating an anti-contaminant layer with a refractive index close to that of air, which moves the total internal reflection interface away from the surface, minimizing the impact of contaminants and maintaining image quality, along with a protective layer to enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an air-waveguide interface is used for light guidance, then the waveguide structure is simple, but contaminants on the interface cause light scattering and image degradation
Solution Approach 1:
A coating layer is introduced as an intermediary between the waveguide surface and the air. This coating layer has a refractive index that is closer to air than the waveguide material, creating a gradual transition that reduces the impact of contaminants on light guidance while maintaining the simplicity of the overall waveguide structure.
2Loss of energy
If the refractive index difference between waveguide and air is large, then light guidance is efficient, but bandwidth is limited
Solution Approach 1:
The refractive index of the coating layer is specifically selected to be closer to air than the waveguide material. This parameter change creates a more gradual refractive index transition, which allows for broader angular bandwidth while maintaining efficient light guidance through the waveguide.
3Ease of manufacture
If contaminants are present on the waveguide surface, then manufacturing is easier, but image quality degrades
Solution Approach 1:
The coating layer acts as a protective intermediary that shields the waveguide surface from contaminants during handling and manufacturing. This allows for easier manufacturing processes while maintaining high image quality, as contaminants on the coating layer have minimal impact on light guidance compared to direct contact with the waveguide surface.
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 anti-contaminant layer effectively protects the waveguide from contaminants, maintaining image quality and increasing bandwidth, while the protective layer ensures durability, ensuring high visible light transmission and improved performance in see-through displays.
Implementation Method 1
The bandwidth of light trapped in the waveguide by total internal reflection (TIR) is limited by the refractive index of the waveguide material (nsubstrate) and air (nair)
Implementation Method 2
The properties of the anti-contaminant layer 240 are chosen such that they have little or no impact on the TIR characteristics of the light guiding layer 110 compared to the situation where there is merely an air-waveguide interface
Data Source
AI summary
In various embodiments, the disclosed subject-matter includes an optical waveguide for a look-through display is disclosed. The optical waveguide includes a light guiding layer and an anti-contaminant layer. The anti-contaminant layer has substantially no impact on the total internal reflection of light at an interface of the light guiding layer. Other devices and apparatuses are also disclosed.