JP-7855292-B1 - Calibration method and program for particle analysis system

JP7855292B1JP 7855292 B1JP7855292 B1JP 7855292B1JP-7855292-B1

Abstract

[Problem] To provide a calibration method for a particle analysis system that prevents halation and insufficient light immediately after the start of measurement, even when using an unknown sample with different optical properties from a standard sample, and enables the rapid setting of appropriate measurement conditions. [Solution] The calibration method of the present invention comprises: a reference setting step (S201) in which a reference laser output value and a reference brightness value are obtained using standard particles; an output adjustment step (S202) in which the ratio of scattered light intensity with that of a standard sample is estimated based on the refractive index information of the sample to be measured, and an initial laser output value for the sample to be measured is determined based on this ratio; a determination step (S203) in which the average brightness value of the particles measured with the initial laser output value is determined to be within a predetermined range of the reference brightness value; and an output control step (S202 to S203) in which, if outside the range, the laser output value is changed, and measurement and determination are repeated until it falls within the range. [Selection Diagram] Figure 2

Inventors

林美晴
神谷勁良

Assignees

株式会社シュヴァルベル

Dates

Publication Date: 20260508
Application Date: 20260129

Claims (11)

A calibration method for a particle analysis system that irradiates particles in a liquid with light from a laser light source and analyzes the particles based on an image of scattered light acquired by an imaging device, A reference setting step involves determining a reference laser output value that yields an appropriate particle size distribution using a standard sample containing standard particles, and obtaining the average value of the brightness of the standard particles obtained at that reference laser output value as the reference brightness value. An output adjustment step is performed to estimate the ratio of scattered light intensity between the standard sample and the sample to be measured based on the refractive index information of the solvent and particles of the sample to be measured, and to determine the initial laser output value for the sample to be measured based on the ratio. A determination step in which the sample to be measured is measured using the initial laser output value, and it is determined whether the average value of the brightness of the particles obtained by the measurement is within a predetermined range corresponding to the reference brightness value, If the average value of the particle brightness obtained by the measurement is not within the predetermined range, the output control step involves repeating the laser output value change, the measurement, and the determination until the value falls within the predetermined range. A calibration method for a particle analysis system, including the above.
In the output adjustment step, A calibration method for a particle analysis system according to claim 1, comprising the assumption that the particle size of the standard particles contained in the standard sample is the same as the particle size of the particles contained in the sample to be measured, and estimating the ratio of the scattered light intensity using a theoretical formula for Rayleigh scattering or Mie scattering, or a lookup table based on said theoretical formula.
In the output control step, A calibration method for a particle analysis system according to claim 1 or 2, wherein if no particles are detected when the sample to be measured is measured, control is performed to increase the output of the laser light source until particles are detected.
A calibration method for a particle analysis system according to claim 1 or 2, wherein the average value of the brightness of the standard particles or the average value of the brightness of the particles obtained by the measurement is based on particles present in a predetermined range in the captured image.
A calibration method for a particle analysis system that irradiates particles in a liquid with light from a laser light source and analyzes the particles based on an image of scattered light acquired by an imaging device, A reference setting step involves determining a reference laser output value that yields an appropriate particle size distribution using a standard sample containing standard particles, and obtaining the average value of the brightness of the standard particles obtained at the reference laser output value as the reference brightness value. An output adjustment step is performed to estimate the ratio of scattered light intensity between the standard sample and the sample to be measured based on the refractive index information of the solvent and particles of the sample to be measured, and to determine the initial laser output value for the sample to be measured based on the ratio. A background determination step in which the sample to be measured is measured using the initial laser output value, and it is determined whether the difference between the average brightness of the particle region in the captured image and the average brightness of the adjacent region adjacent to the particle region is greater than or equal to a predetermined threshold, If the difference is less than the predetermined threshold, a background control step is performed in which the laser output value is reduced and the measurement and determination are repeated until the difference is equal to or greater than the predetermined threshold. A determination step of measuring the sample to be measured and determining whether the average value of the brightness of the particles obtained by the measurement falls within a predetermined range corresponding to the reference brightness value, If the average value of the particle brightness obtained by the measurement is not within the predetermined range, the output control step involves repeating the laser output value change, the measurement, and the determination until the value falls within the predetermined range. A calibration method for a particle analysis system, including the above.
In the output adjustment step, A calibration method for a particle analysis system according to claim 5, comprising assuming that the particle size of the standard particles contained in the standard sample is the same as the particle size of the particles contained in the sample to be measured, and estimating the ratio of the scattered light intensity using a theoretical formula for Rayleigh scattering or Mie scattering, or a lookup table based on said theoretical formula.
In the output control step, Calibration method for a particle analysis system according to claim 5 or 6, wherein if no particles are detected when the sample to be measured is measured, control is performed to increase the output of the laser light source until particles are detected.
The calibration method for a particle analysis system according to claim 5 or 6, wherein the average value of the brightness of the standard particles or the average value of the brightness of the particles obtained by the measurement is based on particles present in a predetermined range in the captured image.
The calibration method for a particle analysis system according to claim 1 or 5, wherein the imaging device includes an optical filter that transmits the wavelength of light from the laser light source and blocks the wavelength band of fluorescence.
A reference number concentration acquisition step is performed, in which the standard sample is measured using the laser output value determined by the output control step, and the number concentration of the standard particles obtained by the measurement is acquired as the reference number concentration. After a predetermined period has elapsed, the standard sample is measured using the determined laser output value, and the laser output value is changed so that the number concentration obtained by the measurement falls within a predetermined range corresponding to the reference number concentration. A calibration method for a particle analysis system according to claim 1 or 5, further comprising:
A program for causing a computer to perform the calibration method for a particle analysis system according to claim 1 or 5.

Description

This invention relates to a calibration method for a particle analysis system that measures particle size and other properties by irradiating fine particles dispersed in a liquid with light and utilizing the scattered light. In particular, it relates to a technique that can improve measurement accuracy when the characteristics of the particles or solvent being measured differ from those of a standard sample. In recent years, ultrafine bubbles (UFBs) and other microparticles have been used in a wide range of fields, including cleaning, food processing, and medicine. As an evaluation method for these particles, the Particle Tracking Analysis (PTA) method, which tracks particles undergoing Brownian motion using laser light scattering, is known (for example, Patent Document 1). In the PTA method, to ensure measurement reproducibility, the laser output and the sensitivity (gain) of the imaging device are calibrated using standard particles with known particle size and concentration (for example, polystyrene latex (PSL) with a particle size of 100 nm). Japanese Patent Publication No. 2020-056743 This figure shows a particle analysis system according to an embodiment of the present invention.This is a flowchart of a calibration method for a particle analysis system according to the first embodiment of the present invention.This is a flowchart of a calibration method for a particle analysis system according to a second embodiment of the present invention. The embodiments of the present invention will be described below with reference to the drawings. However, the components described are illustrative and not intended to limit the technical scope of the present invention to them alone. <First Embodiment> The particle analysis system 100 according to the first embodiment of the present invention comprises a laser light source 10, a sample cell 20, an imaging device 30, a processing device 40, and a display device 50 (see Figure 1). The laser light source 10 can be a semiconductor laser. The laser light source 10 emits laser light 11 into the sample cell 20 containing the dispersion, outputting light of a wavelength that allows Rayleigh scattering light to be emitted from the particles in the dispersion. For example, a semiconductor laser with a wavelength of 405 nm can be used. As shown in Figure 1, the irradiation direction of the laser light 11 is the X direction when the XYZ directions are set as shown in Figure 1. Alternatively, lenses or the like can be added to the optical path to create a sheet-like laser beam 11. This expands the irradiation area, thereby increasing the imaging range. For example, a sheet-like beam can be created using a GRIN lens or a cylindrical lens. The sample cell 20 is made of glass, transparent plastic, or the like, and can hold a dispersion. For example, the sample cell 20 may have a capacity of up to 500 mL of dispersion, but is not limited to this. The imaging device 30 is an imaging device such as a camera equipped with a lens such as a telecentric lens, and it images a predetermined area of the sample cell 20 where the laser light 11 is irradiated. The imaging device 30 may also be equipped with an optical filter that selectively transmits the wavelength of the laser light 11 (scattered light) and blocks other wavelengths (fluorescence, ambient light, etc.). The imaging device 30 is connected to the processing device 40 and can transmit the captured image to the processing device 40. As shown in Figure 1, the imaging device 30 is positioned to capture scattered light from a direction perpendicular to the X direction (Y direction), which is the irradiation direction of the laser light 11. The imaging range can be set, for example, to 5 [mm] × 1.4 [mm], but is not limited to this. The processing unit 40 is, for example, a personal computer, and performs various image processing operations on the captured images sent from the imaging device 30, such as determining the number concentration of a dispersion. The processing unit 40 is also connected to the laser light source 10 and can control its output, etc. Furthermore, the processing unit 40 can control the gain of the imaging device 30. The display device 50 is, for example, a liquid crystal monitor. The display device 50 is connected to the processing device 40 and can display images captured by the imaging device 30, images processed by the processing device 40, and the like. Next, the calibration and measurement procedures will be explained according to the flowchart in Figure 2. In this embodiment, we use pure water containing standard particles (PSL: polystyrene) as the standard sample and rapeseed oil containing UFB (bubbles, particle size unknown) as the sample to be measured. However, the solvent for the sample to be measured is not limited to this and may be water, alcohol, etc. Furthermore, the particles may differ from those of the standard sample. First, the reference setting step is performed in S201. This step involves