Particle measuring device, calibration method, and measuring device
Inventors
Kato, Haruhisa • Matsuura, Yusuke • Nakamura, Ayako • Kondo, Kaoru • TABUCHI, Takuya • Tomita, Hiroshi • Hayashi, Hidekazu
Assignees
National Institute of Advanced Industrial Science and Technology AIST • Rion Co Ltd • Kioxia Corp
Publication Number
US-11774340-B2
Publication Date
2023-10-03
Expiration Date
2039-09-30
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Abstract
For an easy calibration using calibration particles, provided is a measuring device to capture images of target objects. An image analyzer acquires multiple images obtained at a predetermined time interval, (a) specifies the mean-square displacement of a bright point of a calibration particle based on the displacement of the bright point of the calibration particle in the multiple images in a calibration mode, and (b) specifies the mean-square displacement of a bright point of the target particle based on the displacement of the bright point of the target particle in the multiple images in a measurement mode. A particle size analyzer (c) derives the particle size of the target particle from the mean-square displacement of the bright point of the target particle based on the mean-square displacement of the bright point of the calibration particle and the particle size of the calibration particle in an analysis mode.
Core Innovation
The invention provides a particle measuring device, a calibration method, and a measuring device that facilitate easy calibration using calibration particles of known size. The device captures multiple images of target particles and calibration particles at predetermined time intervals and specifies the mean-square displacement of bright points of these particles based on their displacement in pixel units across the multiple images. From this, the particle size of the target particle is derived using the calibration particle's known mean-square displacement and particle size.
The problem addressed is the difficulty of converting mean-square displacement measurements from pixel units of images into physical units needed for particle size calculation, especially when viscosity and temperature of the dispersion medium cannot be easily measured. Conventional methods require various equipment and precise environmental control, complicating accurate particle size measurement by particle tracking analysis (PTA), particularly when calibration of pixel length to physical length is involved.
The invention solves this by using the calibration particle's known size and mean-square displacement directly in pixel units to calibrate the device and derive the target particle's size without converting pixel displacement to physical length. The device includes an image analyzer to acquire multiple images, specify mean-square displacements in both calibration and measurement modes, and a particle size analyzer to derive the particle size in an analysis mode based on calibration data. The invention also allows correction for flow velocity distribution in the dispersion medium to exclude flow effects on particle displacement.
Claims Coverage
The patent includes three independent claims covering a particle measuring device, a calibration method, and a measuring device with scale calibration.
Particle measuring device with calibration using mean-square displacement in pixel units
An image analyzer acquires multiple images at predetermined intervals, specifies the mean-square displacement of a bright point of a calibration particle and a target particle in pixel units during calibration and measurement modes respectively, and a particle size analyzer derives the target particle size from these mean-square displacements and the known calibration particle size in an analysis mode.
Calibration method using mean-square displacement in pixel units
Specifying the mean-square displacement of a calibration particle bright point based on pixel displacement in multiple images, and enabling calculation of the target particle size from the mean-square displacement of the target particle bright point and the known calibration particle size.
Measuring device with scale calibrated by correspondence of mean-square displacement in physical and pixel units
Specifying the mean-square displacement of a calibration particle bright point in pixel units from multiple captured images and calibrating scale according to correspondence between a mean-square displacement derived in physical units according to the Stokes-Einstein expression and the measured pixel-unit displacement.
The claims cover a calibrated particle measuring device and method that derive particle size using pixel-based mean-square displacement measurements with calibration against standard particles, including correction for flow and scale calibration of imaging devices to physical units.
Stated Advantages
Easy calibration of particle measuring devices using calibration particles without needing to measure or convert viscosity, temperature, or pixel size to physical units.
Accurate particle size measurement in dispersion media even when the viscosity and temperature are unknown or difficult to measure.
Exclusion of flow field influences by correcting particle displacement based on known flow velocity distribution, improving measurement accuracy in flowing dispersion media.
Provision for two-dimensional distribution calibration to handle variations in optical magnification across image regions, enhancing local measurement accuracy.
Facilitates scale calibration of imaging devices like microscopes by relating mean-square displacement in pixel units to physical units, providing easy scale setting for size measurements.
Documented Applications
Measurement of particle size of target particles suspended in a dispersion medium, including use in flow cells with optical imaging capturing Brownian motion of particles.
Calibration of particle measuring devices and imaging devices such as optical microscopes using calibration particles of known size in dispersion media.
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