Angle-Independent Optical Filter Using High Refractive Index Dielectric Resonator
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Solution Overview
Problem
Conventional optical filters, including Fabry-Perot based filters, suffer from undesirable angle dependence, leading to wavelength and color shifts when viewed from different angles, which is problematic in imaging and display applications, and they also have complex manufacturing processes and high costs due to the use of pigment dispersions.
Innovation Solution
An optical spectrum filtering device with a metal-dielectric-metal resonator structure that uses high refractive index dielectric materials between parallel reflective surfaces to minimize angle dependence, allowing for both transmission and reflection filtering with minimal wavelength shift across various angles, and employs a method involving polymeric resist materials and etching techniques to create varied dielectric layer thicknesses for different color pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Fabry-Perot based filters are used, then spectrum filtering function is achieved, but angle dependence causes wavelength and color shifts
Solution Approach 1:
The patent changes the refractive index parameter of the dielectric material by selecting materials with high refractive indices (greater than 1.5, preferably greater than 2.0) to reduce angle dependence. This parameter change fundamentally alters the optical interference characteristics, making the filtered wavelength less sensitive to viewing angle while maintaining the spectrum filtering function.
2Reliability
If pigment dispersion methods are used, then color filtering is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent replaces the chemical pigment dispersion method with a physical optical interference method using dielectric layers. This substitution eliminates the need for complex multi-step manufacturing processes involving pigment dispersion, achieving color filtering through controlled optical interference rather than chemical composition.
Solution Approach 2:
The patent employs composite dielectric layer structures with specific refractive indices and thicknesses to achieve the desired spectral filtering. The use of high refractive index dielectric materials creates effective optical interference patterns that replicate color filtering functionality without requiring pigment dispersions.
3Reliability
If conventional Fabry-Perot filters are used, then spectral filtering is achieved, but chemical materials are wasted during manufacturing
Solution Approach 1:
The patent replaces chemical pigment-based filtering with a physical optical interference system using dielectric layers. This eliminates the chemical material waste associated with pigment dispersion manufacturing processes, as the filtering function is achieved through optical path differences and interference patterns rather than chemical absorption.
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 provides optical filters with minimal angle dependence, reduced manufacturing complexity, and increased efficiency, allowing for stable color representation across different viewing angles and improved energy efficiency compared to traditional pigment-based filters.
Implementation Method 1
The interference filter assembly comprises a dielectric material having a refractive index of greater than about 1.5 disposed between a pair of parallel reflective surfaces
Implementation Method 2
Fabry-Perot based optical spectrum filters, having minimal angle dependence from a viewing direction
Data Source
AI summary
An optical spectrum filtering device, e.g., color filter, having reduced angle dependence is provided that comprises an interference filter assembly comprising a high refractive index dielectric material, such as a Fabry-Perot based resonator structure. The filter assembly is capable of transmitting a portion of an electromagnetic spectrum into the dielectric material to generate a filtered output with a predetermined range of wavelengths that displays minimal angle dependence, when viewed from a range of incidence angles ranging from normal (0°) to 90°. Methods of making minimal angle dependent optical spectrum filters and reducing angle dependence for such devices are also provided.