Particle Measurement Defocus Correction for Brownian Sizing
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Solution Overview
Problem
The FPT method for particle size measurement is affected by optical errors in the condensing optical system, leading to inaccuracies in particle size determination due to magnification errors from defocusing, which are not adequately addressed by telecentric optical systems.
Innovation Solution
A particle measuring device and method that corrects movement amounts of particles using pre-determined correction values to account for magnification errors caused by defocusing, allowing for accurate particle size determination by extending the flow passage and capturing scattered light at specific positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a condensing optical system is disposed at such a position as to be opposed to a sample flow direction, then a movement of a particle caused by the sample flow is not observed and only Brownian motion is observed, but magnification errors occur due to defocusing at different positions in the sample flow direction
Solution Approach 1:
The patent applies preliminary action by pre-calculating magnification correction values for each defocus position before actual particle measurement. The system stores these correction values and applies them during measurement to compensate for magnification errors, thereby resolving the contradiction between observing Brownian motion and maintaining optical accuracy.
Solution Approach 2:
The patent changes the parameter of magnification by introducing correction values that adjust for defocus-induced magnification errors. By varying the correction applied based on the defocus position, the system maintains accurate particle size measurement despite the optical system's inherent magnification variations.
2Reliability
If frame images are captured at different defocus positions, then particles are captured with different magnification values, but this leads to errors in calculating movement amount and particle size
Solution Approach 1:
The patent implements feedback by using the known defocus position information to select appropriate magnification correction values. This feedback mechanism ensures that the correct correction is applied based on the actual defocus condition, thereby maintaining measurement reliability and precision.
Solution Approach 2:
The patent adjusts the magnification parameter dynamically by applying different correction values corresponding to different defocus positions. This parameter change approach allows the system to maintain accurate particle size measurement across varying defocus conditions.
3Measurement precision
If correction values are applied for each defocus position, then magnification errors are corrected, but this requires additional computational processing
Solution Approach 1:
The patent reduces computational complexity during measurement by pre-calculating and storing magnification correction values for various defocus positions. This preliminary action transfers the computational burden to the calibration phase, making the actual measurement process simpler and more efficient.
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 method enables precise measurement of particle size by correcting for magnification errors, improving accuracy and reducing the need for telecentric lenses, thus enhancing the freedom of optical system design.
Implementation Method 1
light scattered from a particle contained in a sample passing through a detection region that is formed in a prescribed section of a flow passage is condensed at a position obtained by extending the prescribed section in a flow direction
Implementation Method 2
movement amount of the particle due to Brownian motion in two-dimensional directions
Data Source
AI summary
A flow passage is irradiated with irradiation light, and light scattered from a particle contained in a sample passing through a detection region that is formed in a prescribed section is condensed at a position obtained by extending the prescribed section in a flow direction of the sample and captured at a prescribed frame rate. Then movement amount of the particle due to Brownian motion in directions perpendicular to the flow direction on the basis of captured plural frame images. Furthermore, a particle size of the particle is determined by correcting the movement amount using correction values that were obtained in advance corresponding to each of defocus positions for correcting errors of movement amount in the images caused by magnification.