Rapidly Tuned Diode Lidar Gas Absorption Calibration
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Solution Overview
Problem
Rapidly tunable diode lidar systems face challenges in accurately measuring gas concentrations due to the complex and non-linear variation of laser wavelength over time, making it difficult to perform spectroscopic gas concentration measurements.
Innovation Solution
The system uses algorithms to match observed laser wavelength variations with known absorption line shapes, allowing for calibration and conversion of intensity data into gas concentration measurements, even when the laser wavelength is unknown, by determining the tuning function and using pre-existing knowledge of gas absorption lines to infer the exact wavelength at each time bin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the laser wavelength is tuned rapidly to enable high-speed gas detection, then the measurement speed and productivity are improved, but the wavelength variation becomes non-linear and complex, making measurement precision deteriorate
Solution Approach 1:
The system uses feedback from known gas absorption line shapes to correct and calibrate the wavelength axis in real-time. By comparing observed absorption features with reference data, the system determines the actual wavelength at each time bin, compensating for non-linear tuning effects and maintaining measurement precision despite rapid wavelength variation.
Solution Approach 2:
The system changes the parameter representation from raw time-based wavelength values to corrected wavelength values derived from absorption line shape matching. This parameter transformation allows the system to work with the complex non-linear wavelength-time relationship while maintaining accurate spectroscopic measurements through the use of reference absorption line shapes.
2Adaptability or versatility
If the laser wavelength is tuned rapidly over a wide range, then the adaptability and versatility of the system are improved, but the complexity of the wavelength-time relationship increases, making device complexity worsen
Solution Approach 1:
The system introduces an intermediary calibration layer that mediates between the rapid wavelength tuning mechanism and the spectroscopic measurement requirements. By using known gas absorption line shapes as a reference framework, the system translates complex non-linear wavelength variations into accurate spectral data without requiring direct control or monitoring of the wavelength-time relationship.
Solution Approach 2:
The system creates a virtual copy of the wavelength axis through mathematical modeling and absorption line shape matching. Instead of directly tracking the complex wavelength variations, the system reconstructs the wavelength information from the observed absorption features and reference data, simplifying the overall system complexity while maintaining full spectral accuracy.
3Measurement precision
If algorithms are used to match observed wavelength variations with known absorption line shapes, then measurement precision is improved, but the computational requirements and device complexity increase
Solution Approach 1:
The system performs preliminary action by pre-storing reference gas absorption line shapes and using them to guide the wavelength calibration process. This preliminary preparation of reference data allows the complex matching algorithms to operate more efficiently, reducing real-time computational requirements while maintaining high measurement precision through systematic comparison with known spectral features.
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 method enables highly accurate gas concentration measurements by calibrating the wavelength axis 'on the fly' and determining the gas concentration path length, even with unknown laser wavelength tuning, improving the precision of spectroscopic analysis in rapidly tunable diode lidar systems.
Implementation Method 1
a laser beam may be directed towards an environment containing the gas and the laser wavelength tuned over a wavelength range including the absorption line of the gas
Implementation Method 2
the range is chosen to include the gas absorption line, i.e. a wavelength at which the gas absorbs the incident radiation
Implementation Method 3
A lidar system transmits and then receives scattered laser light from the environment to determine range
Data Source
AI summary
A method of measuring the concentration of a gas in a target environment using a laser lidar system, comprises directing a laser beam towards an environment containing the gas, tuning the laser wavelength over a wavelength range including the absorption line of the gas, and measuring intensity of laser light returned from the environment containing the gas, as a result of scattering as a function of time. The intensity vs time is then converted into gas absorption vs wavelength, and the gas absorption vs wavelength is used to determine the concentration of the gas in the target environment.