Interferometer Metrology System for Remote Gas Analysis
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Solution Overview
Problem
Current interferometry systems face challenges in achieving nanometer-level metrology precision due to mechanical stress and constraints, particularly in remote analysis of gaseous compounds, leading to increased complexity and costs, and existing solutions like single laser metrology or complex digital processing are either impractical or insufficient for real-time precision.
Innovation Solution
A metrology system using a small number (k ≥ 3) of laser beams distributed in the field of view to measure and integrate relative displacements between retro-reflectors, with processing to correct amplitude, phase, and offset differences, enabling estimation and integration of imperfect trajectories and maintaining a stable apparent wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If nanometer-level metrology precision is achieved, then measurement accuracy is improved, but mechanical stress on the moving element increases
Solution Approach 1:
The patent replaces mechanical metrology systems with an optical metrology system using a laser beam. The laser wavelength serves as the measurement reference, eliminating the need for mechanical scales and reducing mechanical stress on moving elements. The optical path difference is measured through interference patterns rather than mechanical position sensing.
Solution Approach 2:
The patent changes the measurement parameter from mechanical position to optical path difference. By using laser interference, the system measures displacement through wavelength-based optical paths rather than mechanical encoders, achieving nanometer precision without proportional mechanical stress increases.
2Manufacturing precision
If spectral resolution is reduced, then the travel of the moving retroreflector increases, but mechanism implementation difficulty increases
Solution Approach 1:
The patent introduces dynamic adjustment capability through the optical metrology system. The laser-based measurement allows real-time monitoring and adjustment of the moving retroreflector position, enabling the mechanism to adapt to varying travel requirements without increasing structural complexity.
3Area of stationary object
If field of view is increased, then sensitivity to trajectory control increases, but metrological sensitivity to moving element trajectory increases
Solution Approach 1:
The patent replaces mechanical trajectory control systems with optical metrology. The laser beam tracks the moving retroreflector across the field of view, providing trajectory measurement without mechanical linkages. This substitution maintains measurement precision while accommodating larger fields of view.
4Length of moving object
If one-sided acquisition is used, then travel of the moving element is reduced, but mechanical stress on the mechanism increases
Solution Approach 1:
The patent replaces mechanical stress-bearing structures with an optical measurement system. The laser metrology system can measure both positive and negative optical path differences without requiring symmetric mechanical travel, allowing reduced physical travel distance while maintaining measurement capability through optical interference patterns.
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 high precision measurements with real-time processing, robustness against laser injection errors, and stable wavelength, effectively compensating for mechanical defects and maintaining precision across the field of view, thus overcoming previous limitations in interferometer design and operation.
Implementation Method 1
Measuring the interference of the laser signal at the interferometer's output allows the measurement time to be linked to an optical path difference
Implementation Method 2
one beam 6 can be reflected by a second retroreflector 2, while a second beam 7 can be reflected by the first movable retroreflector 3
Implementation Method 3
Instruments for the remote chemical and physical analysis of a gaseous compound enable the probing of atmospheric layers. Such an instrument can find applications in meteorology and the analysis of air pollutants. The present invention can be applied to a Michelson interferometer and, more generally, to two-arm interferometers using retroreflectors, such as cube corners.
Data Source
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AI summary
The system has a laser beam acquisition subsystem with a convergent lens (48) and a detection subsystem (49) to provide laser signals (400) representing measurement of interference of a metrology laser beam (41) after passing via an interferometer (40). A metrology unit generates synthetic metrology signals for different points of a field of view of the interferometer from the laser signals, where the metrology signals take into account a trajectory of mobile retroreflectors (3) in a space. The unit has a metrology calculation component to estimate differences of absolute optical path lengths. An independent claim is also included for a metrology method for remote analysis of a gaseous compound.