Jacquinot Stop Reference Detector for FTIR Spectroscopy
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Solution Overview
Problem
Existing Fourier Transform Infrared (FTIR) spectroscopy systems face challenges in accurately measuring background spectra without a separate reference detector, leading to errors due to changes in the optical path and environmental factors like water vapor and CO2, which require frequent background measurements and the use of expensive purge gases.
Innovation Solution
Incorporating a Jacquinot stop with a reflective surface non-orthogonal to the optical axis, allowing previously unused light to be used for a strong reference signal, enabling real-time monitoring and correction of sample data for system and environmental changes, and reducing the need for frequent background measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate background measurement is performed for each sample, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs a background measurement once at the beginning of a sample run to establish a reference spectrum. This preliminary background measurement is then reused for multiple subsequent sample measurements, eliminating the need to perform background measurements before each sample while maintaining spectral accuracy through the use of the stored reference.
2Measurement precision
If purge gas is used to reduce water vapor error, then measurement precision is improved, but loss of substance increases
Solution Approach 1:
The patent uses a reference detector to continuously monitor the background spectrum throughout the sample run. By comparing current measurements against the reference background, the system can identify and correct for water vapor fluctuations without requiring continuous purge gas flow, thereby reducing purge gas consumption while maintaining spectral accuracy.
3Reliability
If a reference detector is used to monitor background spectrum, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent employs an existing detector in the FTIR system to serve dual functions: detecting the sample spectrum and monitoring the background spectrum by capturing light that passes through the sample compartment without interacting with the sample. This multi-functional use of the detector improves system reliability without adding separate reference detection hardware, thereby avoiding increased 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 approach provides a high-quality reference signal that allows for real-time validation and correction of sample data, reducing errors and the need for purge gases, while enabling automatic system validation and improved data collection without separate background measurements, enhancing system stability and reducing user workload.
Implementation Method 1
The J stop includes a reflective surface substantially non-orthogonal to the longitudinal axis of the path and facing the source of the IR signal
Data Source
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AI summary
A spectroscopy system and method in which the optical path following the interferometer includes a Jacquinot stop (70) having an aperture disposed substantially at its focal point. The Jacquinot stop includes a reflective surface (74) substantially non-orthogonal to the longitudinal axis of the path and facing the source of the IR signal containing an interferogram. The aperture (72) passes an inner portion of the incident IR signal, while the reflective surface reflects an outer portion. The reflected outer portion of the incident IR signal, which contains erroneous spectral information due to inherent flaws in the interferometer optics, is thereby effectively removed from the original incident IR signal ultimately used to irradiate the sample, and yet still be made available for use in monitoring background spectra of the sampling optics.