Dynamic Light Scattering Particle Size Measurement Flow Compensation
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Solution Overview
Problem
Current methods for determining particle size in flowing samples are inefficient, particularly for high flow velocities and samples with high viscosity, as they require long measurement times and are sensitive to sample homogeneity and flow velocity variations, limiting the measurement of small particles and particles with rapid Brownian motion.
Innovation Solution
A method and device using dynamic light scattering that compensates for flow movement by determining the offset and rotation angle of consecutive images, allowing for shorter correlation times and enabling measurement of particles across a wider size range and flow velocities, utilizing a data processing approach that aligns images and calculates autocorrelation functions without requiring precise sensor alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time-averaged measurements are used for flowing samples, then measurement stability is improved, but measurement time is extended and sample homogeneity requirements increase
Solution Approach 1:
The patent implements dynamic image capture at multiple delay times to track particle motion in real-time, replacing static time-averaged measurements. This allows the system to adapt to flow conditions while maintaining measurement stability through computational correction of flow-induced image shifts.
Solution Approach 2:
The patent creates virtual detectors by mapping image pixel positions to detection angles, generating multiple virtual measurement points from a single physical camera. This copying approach enables simultaneous multi-point measurements without increasing physical sensor count, improving statistical reliability while maintaining short measurement times.
2Productivity
If high flow velocities are measured, then productivity is improved, but measurement precision deteriorates due to flow-induced image shifts
Solution Approach 1:
The patent calculates image shift amounts by comparing interference patterns at different delay times and uses this feedback information to correct particle position measurements. This closed-loop approach compensates for flow-induced distortions, maintaining measurement precision even at high flow velocities where particles move rapidly through the measurement volume.
Solution Approach 2:
The patent varies the delay time parameter between successive images to optimize measurement for different flow velocities and particle sizes. By adjusting this temporal parameter, the system adapts to different Brownian motion scales and flow conditions, maintaining precision across a wide range of productivity conditions.
3Adaptability or versatility
If small particles with rapid Brownian motion are measured, then measurement versatility is improved, but correlation time measurement requirements become more stringent
Solution Approach 1:
The patent uses periodic image capture at multiple predetermined delay times to sample the autocorrelation function across different time scales. This periodic sampling approach efficiently captures both rapid Brownian motion of small particles and slower motion of larger particles, extending measurement versatility while simplifying correlation time analysis through discrete temporal sampling.
4Measurement precision
If precise sensor alignment is required, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent enables the physical camera to self-correct for misalignment by computationally determining image shift amounts and compensating through virtual detector positioning. Instead of requiring precise mechanical alignment during manufacturing, the system performs self-calibration through image correlation analysis, significantly reducing device complexity and manufacturing cost while maintaining measurement precision.
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
Enables accurate and rapid determination of particle size in both liquid and flowing samples, independent of flow velocity, with reduced measurement time and cost, and improved data processing simplicity, allowing for the measurement of particles across a broader size range and flow velocities.
Implementation Method 1
When small particles are irradiated with light whose wavelength is on the order of the particle diameter, Rayleigh scattering occurs.
Implementation Method 2
If the particles are in a suspension, for example with water, they undergo Brownian motion. Therefore, dynamic interference patterns are generated when a particle suspension is irradiated.
Implementation Method 3
The scattered light from many particles overlaps and forms interference patterns.
Implementation Method 4
The temporal evolution of these patterns is measured in dynamic light scattering (DLS).
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
The invention relates to the size determination of particles in a flowing sample with the aid of light scattering measurements. The invention is based on the concept that initially, scattered light is detected on a detector in the form of images, a standardization of the measured images is done, and a determination of an offset and a rotational angle of at least one partial region of two temporally successive images relative to one another takes place. This information is used to bring the two images into congruence. The images brought into congruence are subdivided into many partial areas, each having a specific number of image pixels, and the brightness values of each individual partial area are averaged. Subsequently, the average brightness value of a partial area of the first image is correlated with the average brightness value of the partial area that was brought into congruence with the corresponding partial area in the second image (cross-correlation between the images). As a result, a correlation value is obtained for each pair of congruent partial areas of the images. Subsequently, all calculated correlation values are averaged. The result is an average correlation value for each pair of images. The delay time of the detector is then varied in order to determine an autocorrelation function of the scattered light signals and to calculate the average size of the particles therefrom.