Waveguide Bonding Stack With Cap Layer for Stable Total Internal Reflection
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Solution Overview
Problem
Waveguide combiners used in augmented reality are susceptible to performance degradation due to porous low index films being altered by adhesive materials, affecting total internal reflection and overall device performance.
Innovation Solution
Incorporating a cap layer between the low index layer and adhesive layer to prevent adhesive penetration, preserving the porosity and refractive index of the low index film, ensuring consistent total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low index film is used to promote total internal reflection in the waveguide combiner, then the light propagation performance is improved, but the porous structure of the low index film makes it susceptible to alteration by adhesive materials, degrading its performance
Solution Approach 1:
A cap layer is introduced as an intermediary element between the low index film and the adhesive layer. This cap layer serves as a protective barrier that prevents adhesive materials from penetrating into and altering the porous low index film structure, while allowing the low index film to maintain its total internal reflection function. The cap layer mediates the interaction between the adhesive and low index film, eliminating the harmful effect of adhesive penetration.
Solution Approach 2:
The waveguide combiner structure is segmented into distinct functional layers: the low index film layer for total internal reflection, the cap layer for protection, and the adhesive layer for bonding. This segmentation separates the optical function from the structural bonding function, allowing each layer to optimize its specific role without interference from other materials.
2Use of energy by moving object
If the low index film is made porous to enhance total internal reflection, then the light guidance capability is improved, but the porosity makes the film vulnerable to material alteration from contacting layers
Solution Approach 1:
The cap layer acts as a mediator that protects the porous low index film from direct contact with adhesive materials. This allows the low index film to maintain its porous structure for optimal light propagation while the cap layer shields it from compositional alteration by external materials.
Solution Approach 2:
The cap layer functions as a thin protective film that covers the porous low index film. This thin film structure provides protection against material penetration while maintaining optical transparency, allowing the underlying porous structure to function effectively without exposure to harmful external materials.
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
Enhances the reliability and performance of waveguide combiners by maintaining the integrity of the low index film, promoting stable total internal reflection and improving the overall functionality of the device.
Implementation Method 1
a first optically clear adhesive layer between the first low index layer and the first lens
Implementation Method 2
Waveguide combiners may use a low index film to promote TIR within the waveguide combiner
Data Source
AI summary
Embodiments of the present invention relate to waveguide and methods of forming waveguides. The waveguide includes a waveguide stack including a waveguide substrate having a top surface and a bottom surface, a first low index layer disposed on the top surface, a first cap layer disposed on the first low index layer, a first lens disposed on the first cap layer, and a first optically clear adhesive layer between the first low index layer and the first lens. In another embodiment, a method of forming a waveguide is provided. The method includes dispensing a liquid optically clear adhesive layer on a lens, placing a waveguide stack including a first low index layer onto the liquid optically clear adhesive opposite the lens, and curing the liquid optically clear adhesive. The waveguide stack further includes a first cap layer disposed on the first low index layer.