Particle Sizing via Multi-Angle Scattering and Refractive Index
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Solution Overview
Problem
Current particle sizing technologies face challenges in accurately determining the size and complex index of refraction of particles, particularly due to the dependence on light scattering, which can lead to uncertainties in particle size measurements and inability to distinguish between real and imaginary parts of the refractive index, especially for a wide range of refractive indices.
Innovation Solution
A device using a modified laser beam with a diamond-shaped profile and photodetectors positioned at specific scattering angles (37° ±5° and 115° ±5°) to measure the intensity of scattered light and time of flight of particles, allowing for simultaneous determination of particle size and both real and imaginary parts of the refractive index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light scattering is used to measure particle size, then particle size can be determined, but measurement precision deteriorates due to dependence on refractive index
Solution Approach 1:
The patent changes the measurement parameters by using multiple scattering angles (e.g., 30° and 150°) instead of a single angle, and combines light scattering measurements with particle number ratio analysis to determine both size and refractive index, thereby resolving the uncertainty caused by refractive index dependence
Solution Approach 2:
The patent implements a feedback mechanism where the measured scattering patterns and particle number ratios are used to iteratively determine the refractive index, which then feeds back to improve the accuracy of particle size measurements through refined scattering calculations
2Loss of information
If twin-angle or multi-angle detection is used to determine refractive index, then refractive index information can be obtained, but device complexity increases
Solution Approach 1:
The patent makes the particle counter multi-functional by enabling it to simultaneously perform particle size measurement, concentration measurement, and refractive index determination using the same optical detection system, eliminating the need for separate specialized instruments
Solution Approach 2:
The patent merges multiple measurement functions (scattering intensity measurement, particle counting, refractive index determination) into a single integrated optical detection system, reducing overall device complexity while maintaining comprehensive measurement capabilities
3Measurement precision
If sheath flow is introduced to control particle position, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent enables the particle stream to self-align with the laser beam through proper optical system design and particle introduction geometry, eliminating the need for external sheath flow systems to force particle positioning
Solution Approach 2:
The patent removes the sheath flow component from the system entirely, replacing it with an optimized optical arrangement that achieves particle positioning through the natural trajectory of particles passing through the detection zone
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 more accurate measurements of particle size and refractive index, reducing uncertainties and enabling real-time identification of particle composition, which is crucial for monitoring air and water quality and detecting environmental contaminants.
Implementation Method 1
Light from the laser beam that is scattered by the particle is measured by one or more photodetectors disposed at a particular scattering angle relative to the center of the laser beam
Data Source
AI summary
Apparatus and methods for determining particle size, and optionally, the complex index of refraction for particle suspended in a gas or liquid are provided. The particle to be analyzed is caused to travel through a laser beam having a modified Gaussian profile. The particle causes light from the laser beam to scatter. The scattered light is measured by one or more photodetectors disposed at a particular scattering angle relative to the center of the laser beam. The apparatus and methods can be used in sensors configured to monitor air quality in enclosed environments, such as on-board aircraft and within buildings, and/or detect environmental contaminants.