Geometric Waveguide With Multilayer Optical Film for Stray Light Control
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Solution Overview
Problem
Existing virtual and augmented reality eyewear devices face challenges in achieving high fidelity and large field of view imagery due to inefficiencies in waveguide displays, particularly in terms of operational efficiency and stray light performance.
Innovation Solution
A geometric waveguide with a multilayer optical film (MOF) is configured to improve efficiency by incorporating a plurality of bonded substrates with facet structures and a multilayer optical film that functions as a partial reflector, partial notch reflector, partial reflective polarizer, or angularly selective reflector, enhancing light control and reducing stray light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional waveguide displays are used, then device structure is simple, but field of view and illuminance uniformity are limited
Solution Approach 1:
The waveguide is divided into multiple substrates bonded together, each substrate containing specific optical layers (high-reflectivity layers, low-reflectivity layers, retardation layers) that segment the optical path control functions. This segmentation enables precise control of light propagation to achieve wide field of view and uniform illuminance while managing structural complexity through modular design.
Solution Approach 2:
The patent employs composite optical structures combining multiple materials with different optical properties (high-reflectivity coating materials, low-reflectivity coating materials, retardation layer materials) within the multilayer optical film. This composite approach enables simultaneous optimization of reflectivity, polarization control, and field of view, resolving the contradiction between performance improvement and structural simplicity.
2Object-affected harmful factors
If conventional waveguide displays are used, then manufacturing process is simple, but stray light and ghost reflections are present
Solution Approach 1:
Different regions of the optical film are assigned different local properties: high-reflectivity layers are positioned at specific locations to reflect intended light paths, while low-reflectivity layers are placed to minimize stray light. Retardation layers are strategically positioned to control polarization locally. This local quality differentiation effectively eliminates stray light and ghost reflections without requiring complete redesign of the entire optical system.
Solution Approach 2:
The multilayer optical film acts as an intermediary component between the light source and the display output. By incorporating retardation layers and varying reflectivity characteristics within this intermediary film structure, the patent filters and purifies the light path, eliminating harmful stray light and ghost reflections while maintaining the overall simplicity of the waveguide display architecture.
3Productivity
If conventional waveguide displays are used, then operational efficiency is low, but device complexity remains manageable
Solution Approach 1:
The optical film structure is designed to maintain continuous useful light propagation through the waveguide. The high-reflectivity layers ensure continuous reflection of intended light paths, while the retardation layers continuously manage polarization states. This continuous action maximizes operational efficiency by minimizing light loss and maximizing the useful display output, justifying the added complexity of the multilayer structure.
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 solution significantly improves field of view and illuminance uniformity, reducing stray light and ghost reflections, resulting in high-performance augmented and virtual reality eyewear.
Implementation Method 1
a multilayer optical film disposed over at least one of the facet structures. The facet structures constitute a reflective element... the multilayer optical film that functions as a partial reflector, partial notch reflector, partial reflective polarizer, or angularly selective reflector
Implementation Method 2
partial reflective polarizer... configured to transmit light having a specific polarization characteristic
Implementation Method 3
light is in-coupled into the waveguide, transported therethrough by total internal reflection (TIR)
Data Source
AI summary
A geometric waveguide includes a first substrate bonded to at least one other substrate, the first substrate including a reflective element having at least one facet, and a multilayer optical film disposed over a surface of the at least one facet, where the multilayer optical film includes two or more birefringent polymer layers.