Waveguide With Gradient Dielectric Coatings For Homogeneous Emission
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Solution Overview
Problem
Conventional waveguide pupil expanders fail to provide spatially homogenous emission, leading to variability in brightness and reduced hologram quality due to intensity and spectral inconsistencies across replicas, especially when waveguiding light with multiple wavelengths.
Innovation Solution
A waveguide with a pair of parallel surfaces featuring alternating layers of dielectric materials with discrete percentage changes in thickness, optimized for specific wavelengths like red, green, and blue, to maintain constant intensity and spectrum across replicas, reducing manufacturing complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional waveguide pupil expanders are used, then the device structure is simple, but the emission is not spatially homogenous leading to brightness variability and reduced hologram quality
Solution Approach 1:
The waveguide surface is segmented into multiple discrete zones along the propagation direction, with each zone having a specific transmissivity value. This segmentation allows independent optimization of each zone's optical properties to achieve spatially homogenous emission across all replicas, resolving the contradiction between manufacturing precision and device complexity by breaking down the continuous optimization problem into discrete, manufacturable zones.
Solution Approach 2:
Different zones of the waveguide surface are assigned different local optical properties (transmissivity values) tailored to their specific position and function. This local quality approach ensures that each zone contributes optimally to the overall spatial homogeneity of emission, allowing the system to achieve high manufacturing precision without requiring complex global restructuring of the entire waveguide.
2Manufacturing precision
If conventional uniform coating is used, then the manufacturing process is simple, but intensity and spectral inconsistencies occur across replicas
Solution Approach 1:
The coating process is segmented into discrete zones corresponding to different transmissivity requirements. Each zone can be manufactured using standard techniques with controlled deposition, avoiding the need for complex continuous gradient coatings while achieving uniform intensity across replicas through the coordinated transmissivity values of individual zones.
Solution Approach 2:
The patent uses discrete, manufacturable coating zones that can be produced using conventional techniques rather than requiring expensive, complex gradient coating equipment. This approach prioritizes ease of manufacture while achieving the desired intensity uniformity through the strategic arrangement of zones with different transmissivity values.
3Adaptability or versatility
If multi-wavelength light is waveguided, then the application versatility is improved, but spectral inconsistencies and absorption losses increase
Solution Approach 1:
The waveguide zones are designed with wavelength-specific transmissivity characteristics optimized for particular wavelength ranges. This local optimization allows different zones to handle different wavelengths efficiently, reducing absorption losses while maintaining multi-wavelength versatility. Each zone's optical properties are tailored to minimize losses for the wavelengths it processes.
Solution Approach 2:
The transmissivity parameter of each zone is specifically adjusted to optimize performance for different wavelengths. By varying the transmissivity values across zones and optimizing them for specific wavelength ranges, the system achieves low absorption losses across multiple wavelengths, resolving the contradiction between versatility and energy loss.
4Manufacturing precision
If conventional waveguiding is used, then the device complexity is low, but hologram quality and consistency are reduced
Solution Approach 1:
The waveguide is divided into multiple zones with specific transmissivity values that can be independently optimized for hologram quality. This segmentation allows precise control over the optical path and replica formation process, ensuring consistent hologram quality across all replicas while maintaining a structure that can be manufactured using conventional techniques.
Solution Approach 2:
Each zone of the waveguide is designed with local optical properties optimized for its specific position in the optical path. This local quality approach ensures that each zone contributes to consistent hologram quality without requiring complex global structural changes, resolving the contradiction between hologram quality consistency and device complexity.
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 achieves spatially homogenous emission at specific wavelengths, enhancing the quality and consistency of the hologram reproduction while simplifying the manufacturing process and reducing absorption losses, making it suitable for applications like head-up displays.
Implementation Method 1
A first surface of the pair of parallel surfaces comprises a plurality of alternating layers of a first and a second dielectric arranged in an alternating configuration... a difference in refractive index between the first dielectric and the second dielectric is greater than 0.4
Implementation Method 2
The plurality of alternating layers... act as a distributed feedback reflector for providing spatially homogenous emission of a light field at a first wavelength, a second wavelength and a third wavelength
Data Source
AI summary
A waveguide comprising a pair of parallel surfaces arranged to provide waveguiding therebetween. A first surface of the pair of parallel surfaces comprises a plurality of layers of a first dielectric and a plurality of layers of second dielectric arranged in an alternating configuration. Each layer of the first and second dielectric has a first end and a second end. A percentage change in the thickness of each layer from the first end to the second end of that layer has one of a plurality of discrete allowable values. The total number of layers of the first and second dielectric is greater than the total number of discrete allowable values. A difference in refractive index between the first dielectric and second dielectric is greater than 0.4.