Open Path Gas Detection Using Multi-Line Laser Absorption
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Solution Overview
Problem
Existing open path gas detection and quantification systems require expensive and complex laser sources for adequate signal-to-noise ratios, and face challenges with center wavelength and linewidth stability, especially during airborne measurements.
Innovation Solution
The method employs simpler, open loop laser sources with linewidths that encompass multiple absorption lines, allowing for gas detection and quantification in regions with dense spectral absorption lines, reducing sensitivity to laser center wavelength stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If expensive and complex laser sources are used to achieve adequate signal-to-noise ratio, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent changes the operating parameters by selecting spectral regions with dense absorption lines and using laser linewidths that encompass multiple lines, which fundamentally alters how the system achieves sufficient signal-to-noise ratio without requiring complex laser sources
Solution Approach 2:
The patent uses a simplified laser source that copies the essential function of complex stabilized lasers by illuminating multiple absorption lines simultaneously, achieving comparable measurement precision through a different physical approach that doesn't require wavelength stabilization
2Measurement precision
If active wavelength stabilization is implemented to maintain center wavelength stability, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the active wavelength stabilization system from the laser source, relying instead on the inherent insensitivity of multi-line absorption measurement to center wavelength drifts, thereby eliminating complex optical and electronics components
Solution Approach 2:
By changing from single-line to multi-line absorption measurement, the system's sensitivity to center wavelength stability is fundamentally reduced, allowing operation without active stabilization while maintaining measurement precision
3Measurement precision
If laser sources with narrow linewidth are used to target individual absorption lines, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple absorption line measurements into a single illumination event by using a laser with linewidth encompassing multiple lines, simplifying the laser source requirements while maintaining measurement precision through combined absorption signal analysis
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 results in more cost-effective, robust, and stable gas detection systems that can operate effectively in harsh environments, such as airborne deployments, with reduced maintenance needs.
Implementation Method 1
open path gas detection and quantification using laser illumination
Implementation Method 2
measuring the returned laser power at two different set wavelengths: an absorption line (the 'on' wavelength) and a nearby spectral region of no absorption (the 'off' wavelength)
Data Source
AI summary
A system for detecting a gas may include a first laser having a wavelength overlapping with two or more absorption features in a spectrum of the gas, a second laser having a wavelength centered away from absorbing features in the spectrum of the gas, and at least one sensor to determine a received power of the first laser and a received power of the second laser.