Spectrometer Interference Suppression via Oscillatory Path Length Modulation
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Solution Overview
Problem
The sensitivity of TDL-WMS spectroscopy is limited by interference strips created by optical elements, which can be improved by suppressing these interference signals.
Innovation Solution
A spectrometer design where the laser light source and/or the first optical element are mounted on a movable carrier, which undergoes vibration movements to change the path length of radiation, thereby suppressing interference signals caused by overlapping rays of different optical path lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical elements are used in the spectrometer, then the device can function properly, but interference fringes are generated that limit detection sensitivity
Solution Approach 1:
The patent applies mechanical vibration to the optical elements (laser light source and/or first optical element) mounted on a movable carrier. The drive unit generates oscillatory movements that modulate the optical path length, causing the interference fringes to shift and average out over time. This vibration-based approach actively suppresses the harmful interference signals while maintaining the necessary optical functionality of the elements.
Solution Approach 2:
The patent transitions from a static optical system to a dynamic one by mounting optical elements on a movable carrier that can oscillate. This dynamic configuration allows the optical path length to vary periodically, transforming the stationary interference pattern into a time-varying signal that can be filtered and suppressed through synchronous detection techniques.
2Reliability
If the laser light source is mounted on a movable carrier, then interference signals are suppressed, but the electrical connection to the laser becomes complex
Solution Approach 1:
The patent replaces the problematic electrical connection approach with a purely mechanical oscillation system. By using a mechanical drive unit to vibrate the optical elements, the system avoids the need for complex sliding electrical contacts or flexible cables that would be required to supply power to a moving laser source. The mechanical vibration is generated through direct coupling to the movable carrier, eliminating electrical connection issues entirely.
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 enhances the robustness and accuracy of gas concentration measurements by effectively filtering out interference signals, leading to improved measurement accuracy and long-term stability.
Implementation Method 1
interference signals, which arise at the at least one optical element as optical interference due to the superposition of rays with different optical path lengths
Implementation Method 2
the movement of the carrier is an oscillatory movement with an amplitude and/or frequency and changes the path length of the radiation in such a way that interfering signals are suppressed
Implementation Method 3
a photodetector arranged to receive the coherent radiation from the laser output after passing a path length
Data Source
Figure 1
AI summary
The invention relates to a spectrometer comprising: (i) a laser light source with coherent radiation, which includes a tunable diode laser with a coherent laser output, wherein the coherent laser light source is configured to modulate the frequency of the coherent laser output; (ii) a photodetector, which is arranged to receive the coherent radiation from the laser output after it has traveled a path length; (iii) at least one optically effective surface, preferably a first optical element, which is arranged along the path length between the laser output and the photodetector; and (iv) an evaluation unit, which is electrically connected to the photodetector, characterized in that the laser light source and/or the first optical element is mounted on a movable support, wherein the movement of the support is an oscillatory movement with an amplitude and/or frequency and changes the path length of the radiation in such a way thatthat interference signals, which arise at the at least one optical element as optical interference due to the superposition of rays of different optical path lengths through at least partial reflection at at least one optical surface, are suppressed, wherein the suppression is achieved through interference between the radiation emitted from the light source and changes in the path length of the ray due to movement on the movable support.