Waveguide Air Pocket Structure for Total Internal Reflection
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Solution Overview
Problem
Existing augmented reality viewing devices face challenges in achieving total internal reflection (TIR) without light loss, as projected light often escapes the waveguide, reducing the clarity and brightness of the image seen by the user.
Innovation Solution
A method of manufacturing an optical system involving a waveguide with a cap layer and a cavity filled with optical gas, enhancing the refractive index difference to promote total internal reflection and minimize light reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a waveguide is used to transmit projected light, then light transmission is achieved, but light loss occurs due to escape from the waveguide
Solution Approach 1:
The patent applies parameter changes by introducing air pockets with specific dimensions (e.g., 1-10 micrometers in size) at strategic locations within the waveguide structure. These air pockets modify the refractive index distribution, creating conditions for total internal reflection. The spacing and positioning of these air pockets are optimized parameters that prevent light escape while maintaining transmission efficiency, directly resolving the contradiction between light loss and image quality.
2Productivity
If total internal reflection is achieved, then light transmission efficiency is improved, but structural complexity increases due to air pocket structures
Solution Approach 1:
The waveguide structure is segmented by introducing discrete air pockets at specific locations rather than using a continuous complex structure. These segmented air pockets are positioned at critical points where light tends to escape, creating multiple small reflection zones. This segmentation approach achieves total internal reflection through distributed simple elements rather than a single complex structure, resolving the contradiction between transmission efficiency and structural complexity.
3Loss of energy
If air pockets are introduced to promote total internal reflection, then light reflection is minimized, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies optimized parameter ranges for air pockets (e.g., 1-10 micrometer size range, specific spacing intervals) that balance reflection minimization with manufacturing feasibility. By defining these parameter ranges, the invention makes precision requirements manageable while still achieving effective total internal reflection. The parameters are chosen to be sufficiently precise to work optically but not so precise as to be manufacturally prohibitive.
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
Improves optical image quality by increasing transmissivity of ambient light, maintaining high diffraction efficiency, reducing ghost artifacts, and minimizing rainbow defects, resulting in clearer and brighter real-world object visibility.
Implementation Method 1
Total internal reflection (TIR) is an ideal situation where there are no losses of the projected light out of the waveguide and 100 percent of the projected light reaches the eye of the user
Implementation Method 2
a beam of the ambient light transmits in the select transparent material of the cap layer, in the cavity holding the optical gas and in the high-index transparent material of the waveguide
Data Source
AI summary
Recesses are formed on a front side and a rear side of a waveguide. A solid porogen material is spun onto the front side and the rear side and fills the recesses. First front and rear cap layers are then formed on raised formations of the waveguide and on the solid porogen material. The entire structure is then heated and the solid porogen material decomposes to a porogen gas. The first front and rear cap layers are porous to allow the porogen gas to escape and air to enter into the recesses. The air maximizes a difference in refractive indices between the high-index transparent material of the waveguide and the air to promote reflection in the waveguide from interfaces between the waveguide and the air.