Inelastic Light Scattering Doppler Wind Lidar
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Solution Overview
Problem
Conventional Doppler effect measurement systems for fluid flows, especially those without particles, face challenges with low signal-to-noise ratio (SNR) and insufficient velocity precision, making them unsuitable for high-speed and accurate applications.
Innovation Solution
The system enhances SNR by incorporating Doppler-resolved inelastic light scattering from atomic/molecular electronic states and molecular rotations/vibrations, using a narrow spectral linewidth local oscillator and heterodyne or interferometric direct detection to measure Doppler shifts, allowing for temporally and spatially resolved density, velocity, and temperature maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional quasi-elastic light scattering measurements are used for fluid flows without particles, then the measurement can be performed, but the signal to noise ratio is low
Solution Approach 1:
The patent changes the scattering mechanism from quasi-elastic to inelastic by exploiting molecular rotational and vibrational transitions. This parameter change in the physical measurement principle enables Doppler-resolved inelastic light scattering, which provides a much stronger signal for particle-free fluid flows while maintaining velocity measurement capability through the Doppler effect on the inelastically scattered photons
Solution Approach 2:
The patent replaces the conventional elastic scattering mechanism with inelastic scattering that involves molecular energy level transitions. This substitution of the fundamental measurement mechanism allows exploitation of molecular rotational and vibrational states to generate a stronger scattered signal that can be Doppler-resolved for velocity measurement in particle-free flows
2Speed
If conventional edge detection and spectral binning wind lidar systems are used, then wind velocity can be measured, but the velocity precision and speed are insufficient for high accuracy applications
Solution Approach 1:
The patent replaces conventional elastic scattering-based lidars with inelastic scattering lidars that exploit molecular rotational and vibrational transitions. This substitution enables Doppler-resolved measurements with much higher velocity precision and measurement speed, as the inelastic scattering process provides a stronger, more resolvable signal for rapid and accurate wind velocity characterization
Solution Approach 2:
The patent changes the fundamental scattering parameter from elastic to inelastic, utilizing molecular energy level transitions. This parameter change enables the system to achieve both high measurement speed and high velocity precision simultaneously, as the inelastic scattering process provides a stronger signal that can be rapidly detected and precisely analyzed through Doppler resolution
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 improved accuracy and precision in measuring wind velocity and flow dynamics, enabling the characterization of non-equilibrium energy transfer and multi-species combustion dynamics with enhanced signal quality and resolution.
Implementation Method 1
Doppler effect of a wave is defined as the change in frequency of the wave from an observer side that is moving relative to the source of the wave
Implementation Method 2
An inelastic scattering of light (photons) is when photons are scattered from an atom or molecule, causing most photons to elastically scatter (Rayleigh scattering)
Implementation Method 3
When light hits small particles, the light scatters in all directions (Rayleigh scattering) as long as the particles are small compared to the wavelength of the light
Implementation Method 4
heterodyne or interferometric direct detection to measure Doppler shifts
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Method and apparatus for measuring a Doppler effect of a scattered light include: projecting an ultra violet (UV) light towards a target by a light emitter; receiving the UV light scatter from the target from the emitted UV light reflected from the target by a light receiver; measuring the frequency shift of the UV light scatter with respect to the emitted UV light to obtain distribution of line of sight velocity of macroscopic matters of the target corresponds to a Doppler shift; processing the distribution of the line of sight velocity to determine the Doppler effect of the UV light scatter; and separating the wind line of sight velocity as the centroid shift of the microscopic Doppler shift probability distribution.