Localized Dynamic Light Scattering System for Doppler Velocity Measurement
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Solution Overview
Problem
Conventional dynamic light scattering systems face challenges in accurately measuring particle size and fluid flow velocity due to multiple scattering events, especially in tissues, and require complex setups with multiple lasers and beam splitters, leading to reduced sensitivity and difficulty in interpreting slow motion signals.
Innovation Solution
A localized dynamic light scattering measurement system utilizing a two-frequency laser source, beam splitter, iris, beam displacer, focusing lens unit, polarizer, and signal processing unit, which generates a heterodyne interference signal to enhance sensitivity and reduce Doppler broadening by filtering unwanted scattering beams, allowing for more accurate Doppler velocity and particle size measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple scattering events occur in the sample, then the light scattering signal becomes more complex, but the accuracy of dynamic information extraction deteriorates
Solution Approach 1:
The patent segments the measurement process by using a confocal microscope to selectively measure light scattering at specific focal planes, thereby isolating scattering events from a limited depth range and reducing the impact of multiple scattering events from out-of-focus regions
Solution Approach 2:
The patent introduces a confocal microscope as an intermediary device between the light source and detector, which acts as a spatial filter to select only light scattered at specific locations and angles, thereby filtering out the complex effects of multiple scattering
2Device complexity
If a single laser source is used for self-mixing, then the device complexity is reduced, but the measurement capability for in-plane motions is insufficient
Solution Approach 1:
The patent makes the single laser source universal by using a rotating polarizer to alternately direct the laser beam at different angles (0度和45度), enabling the system to measure both longitudinal and lateral Doppler shifts with one laser source, thereby achieving multi-functionality without increasing device complexity
3Speed
If the motion speed is very slow, then the Doppler shift becomes very small, but the detection sensitivity remains insufficient
Solution Approach 1:
The patent measures Doppler shift in both longitudinal and lateral dimensions by using two different laser beam angles (0度和45度), thereby obtaining two independent Doppler shift measurements that can be combined to calculate particle velocity, enhancing detection sensitivity for slow motions
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 system achieves higher sensitivity and accuracy in Doppler velocity and particle size measurements, with improved detection of lateral Doppler signals and reduced Doppler broadening, enabling effective measurement of slow motion and fluid flow velocities, and providing enhanced sectioning image capability.
Implementation Method 1
a two-frequency laser source, a beam splitter, an iris, a beam displacer, a focusing lens unit, a polarizer, a photo detecting unit, and a signal processing unit. The two-frequency laser source produces an input laser beam propagating along an optical axis and composed of orthogonal linearly polarized first and second beam components with slightly different frequencies
Implementation Method 2
The beam displacer splits the incident beam into orthogonal linearly polarized first and second output beams corresponding respectively to the first and second beam components
Implementation Method 3
The beam displacer splits the incident beam into orthogonal linearly polarized first and second output beams
Implementation Method 4
The focusing lens unit focuses the orthogonal linearly polarized first and second output beams onto an object to be measured, and collects light backscattered from the object
Implementation Method 5
The photo detecting unit receives the first and second common polarization components from the polarizer to detect and generate a heterodyne interference signal associated with the first and second polarization components, and converts the heterodyne interference signal into an electrical signal
Implementation Method 6
The polarizer polarizes the signal beam from the iris to produce, along a polarization axis of the polarizer, first and second polarization components with common polarization
Implementation Method 7
Since Doppler shift is directly proportional to a component of the motion velocity of the object 84 in the direction of incident light
Data Source
AI summary
A localized dynamic light scattering measurement system includes a beam displacer for splitting an incident beam having two orthogonal linearly polarized beam components with slightly different frequencies into two orthogonal linearly polarized output beams focused onto an object to be measured. The beam displacer cooperates with an iris to collect and recombine scattering beams each reversely backscattered at 180 degrees from the object so as to form a signal beam, which is polarized by a polarizer to produce two polarization components, thereby generating a heterodyne interference signal associated with the polarization components. A signal processing unit obtains measurement data on the object based on power spectrum or autocorrelation data corresponding to the heterodyne interference signal.