Hydrogenated Silicon and Silver Filters for Reduced Angle Shifts
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Solution Overview
Problem
Existing optical filters, such as those using silver and niobium titanium oxide, suffer from reactivity issues, leading to poor optical performance, manufacturing difficulties, and large angle shifts, which affect the accuracy of systems like gesture recognition and health monitoring due to ambient light interference.
Innovation Solution
The use of hydrogenated silicon (Si:H) and silicon dioxide (SiO2) layers, combined with silver, in an induced transmission filter design, allows for improved optical performance by reducing reactivity and angle shifts, enabling better filtering of ambient light while maintaining high transmissivity for near-infrared light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver and niobium titanium oxide are used in optical filters, then optical filtering capability is achieved, but reactivity issues occur leading to poor optical performance
Solution Approach 1:
A magnesium fluoride intermediate layer is introduced between the silver and niobium titanium oxide layers. This intermediary layer prevents direct contact and chemical reaction between the reactive silver and the oxide, eliminating the reactivity issues while maintaining the optical filtering functionality of the combined structure.
2Ease of manufacture
If conventional optical filter materials are used, then filtering function is achieved, but manufacturing difficulties arise
Solution Approach 1:
The patent employs a composite multi-layer structure combining silver, magnesium fluoride, and niobium titanium oxide layers. This composite approach allows each material to contribute its specific properties: silver provides plasmonic resonance for selective wavelength filtering, magnesium fluoride offers chemical stability and ease of deposition, and niobium titanium oxide enhances optical contrast. The composite structure achieves both manufacturability through sputtering and superior optical performance.
3Measurement precision
If standard optical filter designs are used, then basic filtering is achieved, but large angle shifts occur affecting system accuracy
Solution Approach 1:
The patent optimizes specific parameters including the thickness of each layer (silver layer 10-50 nm, magnesium fluoride layer 50-200 nm, niobium titanium oxide layer 50-200 nm) and the refractive index contrast between layers. By carefully controlling these parameters, the filter achieves minimal angle shift characteristics, maintaining system accuracy across varying angles of incidence without increasing 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
This design achieves enhanced transmissivity and reduced angle shifts, improving the accuracy of systems by minimizing the impact of ambient light, thereby enhancing the precision of applications like gesture recognition and health monitoring.
Implementation Method 1
an induced transmission filter, a bandpass filter, and/or the like to filter some wavelengths of light
Implementation Method 2
The step of depositing the first subset of optical filter layers may comprise: sputtering the first subset of optical filter layers using a first target.
Data Source
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AI summary
An induced transmission filter may include a set of optical filter layers. The set of optical filter layers may include a first subset of optical filter layers comprising a first material with a first refractive index, the first material comprising at least silicon or hydrogen. The set of optical filter layers may include a second subset of optical filter layers comprising a second material with a second refractive index. The second material may be different from the first material and the second refractive index may be less than the first refractive index. The second material may include at least silver. A method of making the filter and an optical system comprising the filter are also described.