Tunable Diode Lidar for Methane Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical devices, such as differential absorption lidar systems, face challenges with complex and expensive components, high peak power that damages optical components, and low wall-plug efficiencies, particularly in implementing 'on' and 'off' wavelength locking, and lack continuous scanning capabilities.
Innovation Solution
An optical device that outputs continuous wave radiation, continuously tunes its emission wavelength within a specific spectrum associated with a substance's characteristic, applies modulation to the radiation, and processes scattered radiation to detect substances, capable of scanning at high frequencies up to 200 MHz, enabling efficient detection of gases over long distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulsed radiation is used in differential absorption lidar systems, then detection capability is improved, but optical components are damaged due to high peak power
Solution Approach 1:
The patent uses periodic pulsed radiation to scan through the absorption spectrum of the target gas. The laser emits short pulses at different wavelengths in sequence, allowing detection capability to be maintained while the duty cycle is kept low enough to prevent optical component damage from excessive peak power exposure.
Solution Approach 2:
The patent dynamically changes the wavelength parameter of the laser radiation to scan through the absorption spectrum. By tuning the laser wavelength across multiple values in a scanning sequence, the system achieves spectral detection capability while controlling the temporal distribution of peak power to protect optical components.
2Measurement precision
If pulsed laser systems are used for differential absorption lidar, then detection performance is improved, but wall-plug efficiency decreases
Solution Approach 1:
The system employs periodic pulsed operation where the laser emits radiation in short bursts separated by intervals. This allows the laser to operate at high peak power during pulses for detection while remaining off during intervals, improving overall wall-plug efficiency compared to continuous operation at the same peak power level.
Solution Approach 2:
The patent implements continuous wavelength scanning through periodic pulses, ensuring that the detection process continues uninterrupted across the spectral range. The scanning mechanism maintains continuous useful action by systematically progressing through wavelengths while using efficient pulsed operation at each step.
3Measurement precision
If complex wavelength locking components are implemented, then spectral accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The laser system incorporates self-service wavelength stabilization through feedback from detected spectral features. The system uses the absorption spectrum itself as a reference, automatically locking to known spectral lines without requiring external wavelength reference standards or complex stabilization components.
Solution Approach 2:
The patent implements feedback control where the detected signal from the absorption spectrum is used to adjust and stabilize the laser wavelength. The system monitors spectral features in real-time and provides feedback to maintain accurate wavelength positioning, achieving spectral accuracy through active feedback rather than passive complex components.
4Productivity
If high scanning frequency is achieved, then detection speed is improved, but signal processing complexity increases
Solution Approach 1:
The system uses periodic pulsed radiation with well-defined timing to enable high-speed wavelength scanning. The regular periodic structure of the pulses creates predictable signal patterns that can be efficiently processed using correlation techniques, achieving high detection speed while managing signal processing complexity through the regularity of the periodic waveform.
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 device effectively detects and measures the presence or concentration of gases over distances up to 200 km with high scanning frequencies, reducing component damage and operational costs while maintaining efficient energy use.
Implementation Method 1
a laser device operable to output first output radiation, wherein the first output radiation comprises a continuous wave output; wherein the optical device is operable to tune a first emission wavelength of the first output radiation continuously within a first wavelength spectrum
Implementation Method 2
wherein the optical device is operable to transmit the first output radiation towards a first target location and to collect or receive scattered radiation, the scattered radiation having been at least partially modified by the first substance in the first target location
Implementation Method 3
a processing element operable to process the received scattered radiation
Data Source
AI summary
A method of operating an optical device, comprising: tuning a diode laser wavelength spectrum corresponding to at least a first spectral feature associated with an absorption spectrum of a gas; modulating output radiation of the diode laser; transmitting the modulated output radiation of the diode laser through optical guide elements in a scan towards a first target area; receiving scattered diode laser radiation from the first target area and directing it to a detector; correlating the received scattered diode laser radiation with the transmitted first output radiation to create one or more correlated data sets; and forming an area scan of locations in the first target area to determine concentration of the gas between the optical device and the locations, wherein multiple correlated data sets corresponding to fixed spatial points are used for determining concentration of the gas for each of the locations.