Back-to-back spectrometer thermal isolation design
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Solution Overview
Problem
Fourier transform infrared spectrometers face performance deterioration due to minor misalignments and thermal expansion issues, especially in uncontrolled field conditions, leading to inaccurate sample analysis.
Innovation Solution
A robust spectrometer design with a support structure that fixes the beam splitter and plane mirrors directly onto a massive, homogeneous material, eliminating unwanted movements and integrating cube corner mirrors for precise path length adjustment, ensuring stable infrared light modulation and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the spectrometer is used in field conditions with temperature variations and vibrations, then the spectrometer can operate in uncontrolled environments, but misalignments and thermal expansion cause performance deterioration
Solution Approach 1:
The patent applies local quality by creating a thermally isolated environment for the interferometer using vacuum insulation and thermal barriers. This allows different parts of the spectrometer to have different thermal characteristics - the interferometer section maintains stable temperature while the sample cell can operate at elevated temperatures, thus resolving the contradiction between field operational flexibility and measurement accuracy
Solution Approach 2:
The patent implements beforehand cushioning by pre-isolating the interferometer from thermal effects through vacuum insulation and thermal barriers before temperature variations occur. This protective measure cushiones the sensitive interferometer components against thermal expansion and contraction, maintaining alignment stability despite external temperature changes in field conditions
2Stability of the object's composition
If the beam splitter and mirrors are mounted on a support structure, then the components are fixed in position, but thermal expansion of the support structure causes misalignments
Solution Approach 1:
The patent applies parameter changes by transitioning the support structure from a thermally conductive material to a thermally insulating vacuum environment. This changes the thermal parameters of the support system, eliminating thermal expansion effects on the optical component positions while maintaining mechanical stability, thus resolving the contradiction between positioning stability and alignment precision
Solution Approach 2:
The patent replaces the mechanical support structure with a vacuum-based suspension system. Instead of relying on mechanical mounting that is subject to thermal expansion, the optical components are suspended in vacuum, eliminating the thermal-mechanical coupling that causes misalignment, thus maintaining both positional stability and alignment accuracy
3Object-affected harmful factors
If the spectrometer body is massive to reduce vibrations, then vibration resistance improves, but thermal expansion effects increase
Solution Approach 1:
The patent applies segmentation by dividing the spectrometer into thermally isolated sections - the interferometer is separated from the sample cell and detector sections through vacuum insulation. This allows the massive spectrometer body to provide vibration resistance while the segmented thermal isolation prevents thermal expansion from affecting optical alignment, as each segment can expand independently without transmitting stress to sensitive components
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 design enhances the spectrometer's stability and accuracy by minimizing the effects of temperature variations and vibrations, allowing for reliable sample analysis in varying conditions without the need for frequent recalibration.
Implementation Method 1
a beam splitter and two plane mirrors are fixedly integrated directly onto the support structure
Implementation Method 2
inducing phase shifts between two infrared signals having wavelengths below one millimeter in a controlled manner
Implementation Method 3
integrating cube corner mirrors for precise path length adjustment
Implementation Method 4
A moving mirror inside the interferometer is used to alter the frequency distribution of infrared light that passes through the interferometer
Implementation Method 5
each molecule has a set number (infrared) resonant frequencies at which a particular resonant vibration mode of the molecule is excited and consequently a maximum in the absorption of infrared radiation occurs
Implementation Method 6
the sample gasses may be measured at a high temperature which may result in considerable thermal expansion of the body of the spectrometer causing further inaccuracies in the measurement results
Data Source
Figure 1A~1B
Figure 2
Figure 3A
AI summary
According to an aspect, there is provided a spectrometer comprising a first and second enclosed volumes (111, 112). The second enclosed volume is formed by an absorption cell (112, 312) for containing a sample gas. The first enclosed volume of the spectrometer comprises an interferometer with a source of electromagnetic radiation (101, 301), a first focusing mirror (108, 308) adapted to focus electromagnetic radiation received from the interferometer to the absorption cell (112, 312), a second focusing mirror (109, 309) adapted to focus electromagnetic radiation received from the absorption cell (112, 312) and a detector (110, 310) adapted to detect electromagnetic radiation focused by the second focusing mirror (109, 309). Moreover, the spectrometer comprises a main frame plate (321) on which elements in the first enclosed volume (111) are mounted and which is fixed to the absorption cell (112, 312) arranged on an opposing side of the main frame plate (321).