Matched Optical Filter for IR Spectra in Highly Absorbing Liquids
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Solution Overview
Problem
The strong absorption of infrared energy by liquid water in the wavelength range of 1580-1720 cm−1 complicates IR absorption spectroscopy, leading to significant challenges in signal-to-noise ratio, requiring brighter light sources, multiple tests with ND filters, and optical interference, which prolongs test time and complicates data combination.
Innovation Solution
A method using a matched optical filter that spectroscopically matches to the reference solution to filter IR light inversely, combined with a tunable optical laser and rapid fluid switching, to flatten absorbance and automate measurements, reducing the need for ND filters and minimizing optical interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple flat response Neutral Density (ND) filters are used to utilize the full detector dynamic range, then the measurement precision is improved, but the test time increases by at least 3× and more test sample volume is required
Solution Approach 1:
The patent segments the reference solution measurement into multiple wavelength ranges, each covered by a dedicated optical filter (first optical filter for first wavelength range, second optical filter for second wavelength range). This allows simultaneous or sequential measurement across the full dynamic range without requiring multiple separate tests with different ND filters, thereby reducing test time while maintaining precision.
Solution Approach 2:
The patent creates a universal measurement system where the combination of multiple optical filters covers the entire dynamic range of the detector. Each filter is optimized for a specific wavelength range, and together they provide comprehensive coverage, eliminating the need to repeat tests with different ND filters and reducing both time and sample volume requirements.
2Measurement precision
If a brighter light source is used to overcome the strong absorption of infrared energy in liquid water, then the signal-to-noise ratio is improved, but the system complexity and cost increase
Solution Approach 1:
The patent applies local quality by using different optical filters for different wavelength ranges rather than requiring a uniformly bright light source across all wavelengths. Each filter is tailored to its specific wavelength range, allowing the system to optimize signal-to-noise ratio locally in each range without requiring excessive overall light intensity, thereby reducing system complexity.
3Measurement precision
If multiple tests with fixed attenuation ND filters are performed to cover the full detector dynamic range, then the measurement precision is improved, but the productivity decreases due to repeated testing
Solution Approach 1:
The patent segments the measurement into multiple wavelength ranges with dedicated optical filters, allowing the system to capture the full detector dynamic range in a single test or fewer tests. This eliminates the need to perform multiple sequential tests with different ND filters, thereby improving productivity while maintaining the precision benefits of full dynamic range utilization.
4Illumination intensity
If strong optical interference between optical surfaces is present in high coherence light sources like lasers, then the brightness is improved, but the data quality deteriorates and optical interference varies when passing different components
Solution Approach 1:
The patent addresses optical interference by applying local quality corrections through wavelength-specific optical filters. Each filter is designed to minimize interference effects in its designated wavelength range, allowing the system to maintain high brightness from laser sources while correcting for localized interference issues in each spectral region, thereby preserving data quality.
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
Enables accurate, rapid, and efficient measurement of liquid analytes with weak absorbance in highly absorbing reference solutions, improving signal-to-noise ratio and reducing test time and sample volume, while maintaining data quality.
Implementation Method 1
The matched optical filter is configured to filter at least a portion of the IR light from the IR light source in a substantially inverse manner to the absorbance of the prescribed reference solution
Implementation Method 2
Infra-red (IR) absorption spectroscopy is a powerful tool to analyze protein's secondary structures in aqueous solutions
Data Source
AI summary
In illustrative embodiments, matched optical filters, and methods and systems for using matched optical filters for acquiring infra-red transmission spectra of liquid analytes in very highly absorbing reference solutions are disclosed herein. The matched optical filters compensate for the very high absorbance of the reference solution by filtering out at least a portion of coherent light from a tunable infra-red optical laser to a substantially inverse manner to the absorbance of the reference solution. The matched optical filter may be adjusted to compensate for differences in laser gain across a spectral region of interest where the differential transmission at each wavelength may vary by more than 150 times across the operating range. Thus, the matched optical filters make it possible to obtain spectra of the liquid analyte that may have several orders of magnitude lower absorbance than the reference solution.