Si:H SiO2 Polarizing Filter for Gesture Recognition
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Solution Overview
Problem
Existing optical filters for gesture recognition systems and similar applications face challenges in effectively blocking ambient light while transmitting near-infrared (NIR) light, often resulting in reduced accuracy due to the thickness and cost of dielectric thin film coatings, and the high absorption coefficient of silicon layers for light below 1100 nm.
Innovation Solution
A polarizing optical filter using alternating layers of hydrogenated silicon (Si:H) as high refractive index layers and silicon dioxide (SiO2) as low refractive index layers, which reflects ambient light and passes NIR light, reducing the thickness and cost of the filter while improving durability and optical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional dielectric thin film coatings are used to block ambient light, then the filtering effectiveness is improved, but the thickness and cost of the filter increase
Solution Approach 1:
The patent changes the material parameters by using hydrogenated silicon (Si:H) with refractive index >3.0 instead of traditional dielectric materials, allowing achieving the same optical filtering effect with reduced layer thickness. This parameter change enables thinner filter structures while maintaining effective ambient light blocking performance.
Solution Approach 2:
The patent employs composite material structure by combining hydrogenated silicon (Si:H) layers with silicon dioxide (SiO2) layers to form an alternating multilayer coating. This composite approach leverages the high refractive index of Si:H for compact thickness and the low refractive index of SiO2 for optical contrast, achieving superior filtering performance with reduced overall thickness compared to single-material coatings.
2Object-affected harmful factors
If traditional dielectric thin film coatings are used to block ambient light, then the filtering effectiveness is improved, but the manufacturing cost increases
Solution Approach 1:
The patent changes the material parameters by selecting hydrogenated silicon (Si:H) which can be deposited using plasma-enhanced chemical vapor deposition (PECVD) at lower temperatures and with simpler processes compared to traditional dielectric materials. This parameter change reduces manufacturing complexity and cost while achieving the required optical performance.
Solution Approach 2:
The patent adopts materials that are more cost-effective and easier to manufacture, such as hydrogenated silicon and silicon dioxide, which are commonly available and can be deposited using standard semiconductor fabrication processes. This approach reduces the overall manufacturing cost compared to using expensive specialized dielectric materials.
3Object-affected harmful factors
If silicon layers are used to filter light, then the ambient light blocking is improved, but the absorption of NIR light increases
Solution Approach 1:
The patent applies local quality by using hydrogenated silicon (Si:H) with controlled properties in specific layers where ambient light blocking is needed, while maintaining thin overall structure to minimize NIR absorption. The alternating structure with SiO2 layers creates regions of high optical contrast for blocking while keeping the total path length for NIR transmission short, thus reducing energy loss.
Solution Approach 2:
The patent uses composite material structure combining Si:H and SiO2 layers, where Si:H provides high refractive index for compact thickness and SiO2 provides low absorption for NIR transmission. This composite approach balances the conflicting requirements of blocking ambient light while minimizing NIR light absorption, overcoming the limitation of pure silicon layers.
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 greater than 99% transmission for NIR light and greater than 99% reflectance for ambient light, enhancing the accuracy of gesture recognition systems by effectively filtering out ambient light without excessively blocking NIR light, with a reduced thickness and cost compared to traditional materials.
Implementation Method 1
The set of alternating high refractive index layers and low refractive index layers may be disposed onto the substrate to polarization beam split incident light
Implementation Method 2
a first polarization of the incident light with a spectral range of less than approximately 800 nanometers (nm) is reflected by the optical filter and a second polarization of the incident light with a spectral range of greater than approximately 800 nm is passed through by the optical filter
Data Source
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AI summary
An optical filter may include a substrate. The optical filter may include a set of alternating high refractive index layers and low refractive index layers disposed onto the substrate to polarization beam split incident light. The set of alternating high refractive index layers and low refractive index may layers may be disposed such that a first polarization of the incident light with a spectral range of less than approximately 800 nanometers (nm) is reflected by the optical filter and a second polarization of the incident light with a spectral range of greater than approximately 800 nm is passed through by the optical filter. The high refractive index layers may be hydrogenated silicon (Si:H). The low refractive index layers may be silicon dioxide (SiO2).