Particle Sizing via Far-Field Light Scattering Imaging
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Solution Overview
Problem
Conventional particle sizing systems using light scattering are sensitive to particle composition and require frequent maintenance due to vacuum-based pumping systems, leading to measurement errors and increased operating costs, while also being limited in determining individual particle sizes accurately.
Innovation Solution
A particle sizing system that employs a light beam illuminating particles within a monitored volume, utilizing multiple light deflectors to collect scattered light at various angles, and an image capture device to generate sub-images of each particle, allowing for the identification and sizing of individual particles based on spot parameters without the need for prior composition knowledge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sideway scattering detection at 90° is used to make the system compact and reduce stray light, then the system size is reduced and stray light is minimized, but the system becomes highly sensitive to particle composition requiring frequent calibration
Solution Approach 1:
The patent transitions from detecting scattered light intensity at a fixed 90° angle to imaging the spatial distribution of scattered light in the far field. By capturing the two-dimensional intensity distribution pattern (diffraction pattern) on an imaging detector, the system obtains size information from the spatial frequency content of the pattern rather than from absolute intensity measurements, thereby eliminating composition sensitivity while maintaining compactness.
2Ease of operation
If vacuum-based pumping systems are used to supply particles to the chamber, then particles can be sampled from ambient medium, but the systems require frequent maintenance and calibration due to mechanical wear
Solution Approach 1:
The patent eliminates the mechanical vacuum pumping system by performing measurements in the far field where particles can be observed directly in the ambient medium. The optical system captures scattered light patterns without requiring particle transport through vacuum channels, thereby removing moving mechanical parts that require maintenance and calibration.
3Measurement precision
If inversion methods are used with forward scattering detection to reduce composition sensitivity, then particle composition influence is minimized, but only particle size distributions can be obtained rather than individual particle sizes
Solution Approach 1:
The patent captures the complete spatial intensity distribution pattern (optical copy of the particle's scattering characteristics) in the far field using an imaging detector. Each particle produces a unique diffraction pattern that contains encoded size information in its spatial frequency content. By analyzing the pattern geometry rather than relying on inversion algorithms, the system directly determines individual particle sizes without losing information, while the far-field condition inherently reduces composition sensitivity.
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 reduces the system's sensitivity to particle composition and mechanical maintenance requirements, enabling accurate determination of individual particle sizes with improved reliability and reduced operational costs.
Implementation Method 1
measuring light scattered by the particles
Implementation Method 2
a plurality of light deflectors, each light deflector being positioned to receive and deflect light scattered by the illuminated particles
Data Source
AI summary
A particle sizing system is provided that includes an optical source generating a light beam for illuminating particles in a monitored volume, a plurality of light deflectors, each positioned to receive and deflect light scattered by the particles, and an image capture device collecting scattered light deflected by each light deflector. The image capture device outputs an image including a plurality of sub-images, each generated from the collected light deflected from a respective one of the light deflectors. Each particle is imaged as a spot in each sub-image, the plurality of spots associated with each particle corresponding to a plurality of scattering angles. The system also includes a processing unit configured to identify the spots associated with each particle in the sub-images, compute a spot parameter associated with each spot, and determine the size of each particle from its related spot parameters. A particle sizing method is also provided.