UV Optical Filter with Extended Out-of-Band Blocking
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Solution Overview
Problem
Current optical transmission filters, particularly those for the 230-320 nanometer UV range, suffer from low transmission, incomplete out-of-band blocking, and reliability issues, failing to provide the necessary high performance for applications like UV fluorescence spectroscopy and absorption spectroscopy.
Innovation Solution
A modified process for fabricating optical filters using alternating high and low index of refraction hard-coating thin-film layers, optimized with ion beam sputtering deposition and optical monitoring, to achieve higher transmission, sharper edge slopes, and extended out-of-band blocking, specifically designed to address the challenges of UV filters where transparent materials are not available.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical transmission filters are used for UV range (230-320 nm), then the filter structure is simple and manufacturing is easier, but transmission is low and out-of-band blocking is incomplete
Solution Approach 1:
The filter is divided into multiple alternating layers of high-index and low-index materials, with each layer contributing to the overall blocking and transmission characteristics. This segmentation allows the filter to achieve superior out-of-band blocking by distributing the filtering function across many thin layers rather than relying on a single thick filter element.
Solution Approach 2:
The patent uses composite material structures combining multiple dielectric layers with different refractive indices (e.g., TiO2, SiO2, Ta2O5, Nb2O5, HfO2) to create a filter that achieves both high transmission in the UV passband and extended blocking in the visible range. The composite structure leverages the optical properties of each material to achieve performance unattainable with single materials.
2Manufacturing precision
If conventional filter materials are used, then manufacturing process is simpler, but transmission in UV range is low and edge slopes are gradual
Solution Approach 1:
The patent implements in-situ optical monitoring during the deposition process to provide real-time feedback on layer thickness and optical properties. This feedback mechanism allows precise control of each layer's thickness to achieve the desired sharp edge slopes and transmission characteristics, while automatically adjusting the deposition process to maintain precision.
Solution Approach 2:
The patent replaces conventional mechanical deposition control methods with ion beam sputtering deposition, which uses physical vapor deposition enhanced by ion bombardment to achieve superior control over layer thickness and density. This substitution enables sharper edge slopes and more precise manufacturing control compared to traditional mechanical coating methods.
3Reliability
If standard deposition methods are used, then manufacturing is easier, but transmission is lower and blocking is incomplete
Solution Approach 1:
The patent replaces standard thermal evaporation or chemical vapor deposition methods with ion beam sputtering deposition. This substitution provides superior control over film density, thickness uniformity, and optical properties, resulting in enhanced transmission in the UV passband and extended blocking into the visible range, while maintaining manufacturing feasibility through automated process control.
Solution Approach 2:
The patent systematically varies deposition parameters including ion beam energy, deposition rate, substrate temperature, and layer thickness to optimize the optical performance of each layer. By carefully controlling these parameters, the filter achieves high transmission in the 230-320 nm UV range while maintaining deep blocking in the visible spectrum, overcoming the limitations of standard deposition methods.
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 resulting filters offer up to three times greater transmission, four times sharper edge slopes, and deep out-of-band blocking extending into the visible range, significantly improving the performance of UV filters for biomedical applications.
Implementation Method 1
A modified process for fabricating optical filters using alternating high and low index of refraction hard-coating thin-film layers, optimized with ion beam sputtering deposition
Implementation Method 2
measuring during the deposition of the layer for a period of time less then ti a measured transmission Tm of light through the layer
Implementation Method 3
a plurality of alternating layers of at least two hard-coating materials of higher refractive index and lower refractive index
Data Source
AI summary
In accordance with the invention, a filter is fabricated to take into account the effect of absorption by filter material. The method is exemplified by the fabricating of an ultraviolet light transmission filter for transmitting a band within the range 230-320 nanometers. The resulting filter comprises plurality of hard-coating, thin-film layers of alternating high and low index of refraction. The improved filter provides high transmission, sharp edge slopes, and deep and extended out-of-band blocking. As compared with currently available filters, the filter provides transmission up to three or more times greater, edge slopes up to four times sharper, and deep extended out-of-band blocking extending further, even through the visible range.