System for measuring the concentration of a dispersion and method for measuring the concentration of a dispersion

Abstract

Accurate concentration measurements can be performed even with low-concentration dispersions. [Solution] The dispersion concentration measurement system according to the present invention comprises a container 20 for containing the dispersion, a laser light source 10, an imaging device 30 that captures an image of the region where laser light 11 from the laser light source 10 is incident on the liquid in the container 20 and generates an image, and a processing device 40. The processing device 40 counts the number of bright spots based on a first image obtained by irradiating the container 20 with only the solvent and laser light 11, and counts the number of bright spots based on a second image obtained by irradiating the container 20 with the dispersion and laser light 11. The concentration of the dispersion is determined by subtracting the number of bright spots in the first image from the number of bright spots in the second image and dividing the result by the volume of the dispersion obtained by multiplying the imaging range of the imaging device 30 by the depth of field.

Description

[Technical Field]

[0001] This invention relates to a system for measuring the concentration of a dispersion. [Background technology]

[0002] Conventionally, it is known that the concentration of a dispersion containing minute substances such as nanoparticles or ultrafine bubbles can be measured by irradiating the dispersion with light, imaging the scattered light, and analyzing it. For example, Patent Document 1 describes measuring the concentration based on the number of bright spots in an image captured by a camera of the scattered light after irradiating a dispersion containing standard particles with laser light. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-061147 [Overview of the project] [Problems that the invention aims to solve]

[0004] When measuring concentration based on images, it is conceivable to use an objective lens to detect scattered light from minute particles. However, this narrows the imaging range of imaging devices such as cameras, and especially when the concentration of the dispersion is low, the number of minute particles that can be observed decreases, leading to problems such as being unable to accurately measure the concentration of the dispersion. [Means for solving the problem]

[0005] To solve the above problems, the dispersion concentration measurement system according to the present invention is a dispersion concentration measurement system for measuring the concentration of a dispersion consisting of particles and a solvent, comprising: a container for containing the dispersion; a laser light source; an imaging device for imaging the region where laser light from the laser light source is incident on the liquid in the container and generating an image; and a processing device, wherein the processing device counts the number of bright spots based on a first image obtained by irradiating the container with the laser light while only the solvent is contained in the container; counts the number of bright spots based on a second image obtained by irradiating the container with the laser light while the dispersion is contained in the container; and calculates the concentration of the dispersion by subtracting the number of bright spots in the first image from the number of bright spots in the second image and dividing the result by the volume of the dispersion obtained by multiplying the imaging range of the imaging device by the depth of field. [Effects of the Invention]

[0006] This invention solves the above problems by expanding the imaging range of the imaging device, enabling more accurate concentration measurement even for low-concentration dispersions. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows a dispersion concentration measurement system according to the first embodiment. [Figure 2] This is a flowchart showing the calibration procedure for the dispersion concentration measurement system according to the first embodiment. [Figure 3] This is an example of an image captured according to the first embodiment. [Figure 4] This is an example of an image captured to illustrate the process of counting the number of standard particles according to the first embodiment. [Figure 5] This figure schematically represents the captured image according to the second embodiment. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to the drawings. However, the components described are illustrative and are not intended to limit the technical scope of the present invention to them alone.

[0009] <First Embodiment> Figure 1 shows a dispersion concentration measurement system 100 according to the present invention. The dispersion concentration measurement system 100 comprises a laser light source 10, a container 20, an imaging device 30, a processing device 40, and a display device 50.

[0010] The laser light source 10 can be a semiconductor laser. The laser light source 10 emits laser light 11 into a container 20 containing a dispersion liquid, and outputs light of a wavelength that can cause Rayleigh scattering light to be emitted from the particles contained in the dispersion liquid. 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 form a sheet of laser light 11. This expands the irradiation area, thereby increasing the imaging range. For example, a sheet can be formed by using a GRIN lens or a cylindrical lens.

[0011] The container 20 is made of glass, transparent plastic, or the like, and can hold a dispersion. For example, the container 20 can hold a maximum of 500 mL of dispersion, but is not limited to this. The dispersion contains standard particles, for example, polystyrene standard particles (manufactured by Thermo Fisher). In embodiments of the present invention, for example, particles with a particle size of 100 nm are used, but any particles with the same particle size and in which Rayleigh scattered light can be observed are acceptable and are not limited to this. Pure water is used as the dispersion medium, but tap water may also be used.

[0012] The imaging device 30 is an imaging device such as a camera equipped with a lens like a telecentric lens, and images a predetermined area where the laser light 11 is irradiated on the container 20. The imaging device 30 is connected to the processing device 40 and can transmit the captured imaging image to the processing device 40. As shown in FIG. 1, the imaging device 30 is arranged to capture scattered light from a direction (Y direction) perpendicular to the X 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 thereto.

[0013] The processing device 40 is, for example, a personal computer, and performs various image processes on the imaging image sent from the imaging device 30. It also has various computing functions such as obtaining the density based on the processed image.

[0014] 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 the imaging image captured by the imaging device 30, the image processed by the processing device 40, etc.

[0015] Next, the calibration procedure of the dispersion concentration measurement system 100 will be described according to the flow of FIG. 2. The dispersion concentration measurement system 100 is calibrated by the calibration procedure of FIG. 2 using standard particles, and even if the imaging range of the imaging image 30 is expanded, the concentration of the dispersion can be accurately measured.

[0016] First, a plurality of dispersions with different concentrations are prepared (S210). The dispersion is a sample containing standard particles with a particle diameter of 100 nm diluted with pure water and the standard particles are uniformly dispersed. The concentration is, for example, 10 4 、10 5 、10 6 、10 7 、10 8 、10 9 [pieces / mL], but at least two types are prepared. Then, each dispersion is individually put into the container 20.

[0017] Next, the user selects one of the dispersion liquids prepared in S210 and sets it at a predetermined position. When the laser light source 10 irradiates the laser beam 11 onto the container 20, the processing device 40 acquires the captured image generated by the imaging device 30 capturing the irradiation area (S220). At this time, the imaging device 30 captures it as a moving image, and the processing device 40 acquires the captured images that are temporally continuous. An example of the captured image is shown in FIG. 3. As shown in FIG. 3, in the pixels that receive scattered light due to the presence of the standard particles, a high luminance value is shown.

[0018] Next, the processing device 40 performs image processing on the acquired captured image to identify the standard particles in the captured image (S230). For example, a pixel group having a luminance value equal to or greater than a predetermined value is treated as one standard particle so that it can be identified in association with its position information. Further, by also associating the distribution of the luminance values of the pixel group, the size, the feature amounts of the bright and dark regions in a circular shape, etc., the standard particles can be identified more accurately.

[0019] Next, the number of standard particles included in the captured image is counted (S240). Specifically, in the consecutive captured images, the number of standard particles at a certain time t is counted. However, for example, if the standard particles overlap on the captured image, they are counted as one, so the exact number cannot be counted. Therefore, in this counting, at least three captured images, namely the captured image at time t, the captured image at t + Δt, and the captured image at t - Δt, are used to more accurately count the number of standard particles in the captured image at time t. Note that Δt is preferably 200 [ms], but a numerical value within the range of about 200 ± 50 [ms] may also be used.

[0020] Figure 4(A) is the captured image 450 at time t, and Figure 4(B) is the captured image 460 at time t+Δt. First, it is determined whether each of the standard particles identified in S230 for captured image 450 has a one-to-one correspondence with any of the standard particles identified in S230 for captured image 460. For example, considering the movement of the standard particles due to Brownian motion during time Δt, a one-to-one correspondence is determined to exist between standard particles that are within a predetermined range from the position of the standard particle at time t and whose feature quantities also match.

[0021] For example, the standard particle 411 in the captured image 450 at time t is located within a predetermined range relative to the standard particle 412 in the captured image 460 at time t+Δt, and their features also match. Therefore, it is determined that there is a one-to-one correspondence between standard particle 411 and standard particle 412. On the other hand, the standard particle 410 in the captured image 450 is determined to have a correspondence with standard particles 420 and 421 in the captured image 460 based on its displacement and features, and therefore, a one-to-one correspondence is not determined. In this way, for all standard particles identified in the captured image at time t, it is determined whether there is a one-to-one correspondence with the standard particles identified in the captured image at time t+Δt, based on their displacement and features.

[0022] Similarly, for all standard particles identified in the image captured at time t, it is determined whether there is a one-to-one correspondence between them and the standard particles identified in the image captured at time t-Δt, based on the distance traveled and the features. For example, standard particle 411 in image 450 at time t is within a predetermined range and its features match those of standard particle 413 in image 470 (Figure 4(C)) at time t-Δt, so it is determined that there is a one-to-one correspondence between standard particle 411 and standard particle 413. On the other hand, standard particle 410 in image 450 is determined to have a correspondence with standard particles 430 and 431 in image 470 based on the distance traveled and the features, so it is not determined that there is a one-to-one correspondence.

[0023] Taking Figure 4 as an example, the standard particle 410 in the captured image 450 does not have a one-to-one correspondence with the standard particle present in either the captured image 460 at time t+Δt or the captured image 470 at time t-Δt. In other words, although the standard particle 410 in the captured image 450 appears to be a single particle, by referring to the preceding and succeeding captured images, it can be considered that the standard particles are overlapping. Therefore, in such cases, the number of standard particles is counted as two.

[0024] In this way, standard particles are identified in the image captured at a certain time t, the image captured at t+Δt, and the image captured at t-Δt. It is then determined whether the standard particles identified in the image captured at time t have a one-to-one relationship with the standard particles identified in the images captured at t+Δt and t-Δt, such that they are within a predetermined range and their features match. If there is no one-to-one relationship with the images captured at t+Δt and t-Δt, it is assumed that there is overlap of standard particles, and the number of standard particles in the image captured at time t is calculated by adding the number of particles that do not have a one-to-one relationship to the number of standard particles identified.

[0025] In this embodiment of the present invention, ±Δt at equal intervals before and after the time is processed, but it is also possible to use the image captured at a certain time t as the starting point and use the images captured before and after that time.

[0026] Furthermore, if the entire imaging area is treated as the target of processing, standard particles at its edges may be affected by Brownian motion, causing them to move in and out of the imaging area. Therefore, it is also possible to count only the bright spots located within a range shifted a few pixels inward in the left, right, top, and bottom directions, rather than the entire imaging area.

[0027] Next, in S250, the concentration of the dispersion is calculated. The concentration of the dispersion is obtained by dividing the number of standard particles contained in the image captured at time t, counted in S240, by the volume of the dispersion, which is obtained by multiplying the area of ​​the imaging range of the imaging device 30 by the depth of field of the imaging device 30. The area of ​​the imaging range is determined from the measured distance from the imaging device 30 to the imaging target (the area in the container 20 irradiated by the laser light 11) and the field of view. For example, if the depth of field of the imaging device 30 is 44 [μm], and the imaging range is set to 5 [mm] × 1.4 [mm], the calculated volume of the dispersion is 0.308 mm³. 3 This is the result.

[0028] Next, in S260, it is determined whether the concentration of the dispersion calculated in S250 is within a predetermined range (appropriate concentration) relative to the actual concentration of the dispersion prepared in S210. For example, the predetermined range can be set to ±10%. If the concentration is appropriate (S260; YES), the process proceeds to S280; otherwise, it proceeds to S270.

[0029] In S270, the device settings are changed. These settings include at least one of the following: the gain of the imaging device 30, the exposure time, and the output value of the laser light source 10, but other settings may also be used. Next, the process returns to S220, an image is acquired based on the changed device settings, and after similar processing in S230 to S250, it is determined whether the density is appropriate (S260). In other words, the device settings are changed repeatedly until the density is appropriate. Even if the density is appropriate (S260; YES), the process may proceed to S270 to change the device settings again in order to define the range of the device settings.

[0030] Next, in S280, the device settings are determined. That is, the device settings that allow the captured image to appropriately represent the concentration of the dispersion are designated as the device settings for dispersions of that concentration. If the device settings have been changed several times in S270 and there is a range of settings that can correspond to those concentrations, that range may be designated as the device settings.

[0031] Next, in S290, it is determined whether the device settings have been determined for all of the dispersions of different concentrations prepared in S210, as performed in S280 after carrying out S220 to S270. If there are any dispersions that have not been processed (S290; NO), the process returns to S220 and each process is performed on the dispersions that have not been processed. If there are no dispersions that have not been processed (S290; YES), the process proceeds to S295.

[0032] In S295, the device settings determined in S280 are referenced for each dispersion of different concentrations, and the device settings that satisfy all of these conditions are determined. For example, suppose the device settings determined for dispersion of concentration A are (imaging device 30: exposure time 10-20 [ms], gain 10-15 [dB], laser light source 10: output 1.0 [W]), and the device settings determined for dispersion of concentration B are (imaging device 30: exposure time 10-25 [ms], gain 15 [dB], laser light source 10: output 1.0 [W]). In that case, in S295, the device settings that can be used for all concentrations, satisfying the device settings for concentrations A and B, can be determined as (imaging device 30: exposure time 15 [ms], gain 15 [dB], laser light source 10: output 1.0 [W]).

[0033] As described above, the dispersion concentration measurement system 100 is properly calibrated, allowing for accurate concentration measurement even when the imaging range is expanded. In this way, there is a need for a device setting that can accommodate dispersions of different concentrations. For example, in images with high concentrations, if the device settings are not appropriate, the bright spots may become large, making accurate counting impossible. Therefore, a device setting that minimizes the overlap of bright spots is preferable. However, if this setting is applied, the dispersed light may not be captured in images with low concentrations, potentially leading to large errors in concentration determination. Therefore, calibration according to the embodiment of the present invention is performed to configure the device so that it can appropriately measure the concentration of dispersions of different concentrations.

[0034] <Second Embodiment> In the second embodiment, when the captured image includes bright spots caused by particles other than standard particles, the bright spots are excluded so that the standard particles can be identified.

[0035] The concentration measurement system 300 for the dispersion liquid according to the second embodiment includes, in addition to the configuration of the concentration measurement system 100 for the dispersion liquid shown in FIG. 1, a polarizer 310 and a half-wave plate 330 attached to a rotation mechanism 320 between the laser device 10 and the container 20 (not shown). Further, lenses or the like may be added to make the light sheet-shaped and irradiate the container 20. The polarizer 310 is used to obtain linearly polarized light with a higher extinction ratio. The half-wave plate 330 is for rotating the vibration axis of the linearly polarized light. The rotation mechanism 320 rotates the half-wave plate 330 by 45 degrees.

[0036] Next, the calibration procedure of the dispersion liquid concentration measurement system 300 will be described. This calibration procedure follows the calibration procedure shown in FIG.

[0037] First, in S210, a plurality of dispersion liquids containing standard particles and having different concentrations are prepared, which is the same as in the first embodiment. That is, for example, the particle size is 100 [nm] and the concentrations are 10 4 、10 5 、10 6 、10 7 、10 8 、10 9 [pieces / mL]. The dispersion medium contains impurities, and for example, tap water is used.

[0038] Next, in S220, captured images are obtained, and a plurality of captured images when horizontally polarized incident light and a plurality of captured images when vertically polarized incident light are obtained. Specifically, a captured image when irradiating the container 20 with vertically polarized laser light is obtained, and then the rotation mechanism 320 is used to switch so that vertically polarized light is incident, and a captured image when irradiating with horizontally polarized laser light is obtained. Note that this order may be reversed.

[0039] Figure 5 shows an example of an image captured according to the second embodiment. In Figure 5, circles indicate areas of high brightness. Figure 5(A) shows the image captured when the incident light is vertically polarized, and Figure 5(B) shows the image captured when the incident light is horizontally polarized, 520.

[0040] Here, Equation 1 represents the scattered light intensity I1 due to Rayleigh scattering in vertically polarized incident light, and Equation 2 represents the scattered light intensity I2 due to Rayleigh scattering in horizontally polarized incident light. In Equations 1 and 2, I0 is an instrument constant such as gain, exposure time, and laser power value, a is the particle diameter, k is the wavenumber, r is the observed distance from the particle to the imaging device, m is the relative refractive index of the particle and the solvent, and θ is the scattering angle.

[0041]

number

[0042]

number

[0043] As can be seen from Equation 2, when θ = 90 degrees and the incident polarization state is horizontal, the scattered light intensity due to Rayleigh scattering is 0. Therefore, the bright spots present in the image when the incident light is horizontally polarized are due to scattered light from Mie scattering, etc., and since the particle size of these particles is considerably larger than that of standard particles, it is assumed that foreign matter is present.

[0044] In the following S230, this feature is used to identify standard particles by removing foreign matter from the bright spots. First, bright spots in the captured image 510 when horizontally polarized incident light is identified. Using Figure 5(B) as an example, bright spots 502 and 503 are identified based on their brightness values ​​and feature quantities. Their positional information and feature quantities are stored in association with each other. The bright spots in the captured image 510 are due to Mie scattering, and are therefore assumed to be caused by foreign matter rather than standard particles.

[0045] Next, the captured image 500 for vertically polarized incident light is referenced. Then, based on positional information and feature quantities, bright spots 502 and 503 in the captured image 500 are identified and removed from the image. The "new" captured image 520 shown in Figure 5(C) is obtained by performing this process. In this way, even if the captured image contains bright spots due to foreign matter, if they are due to Mie scattering, they can be removed from the captured image 500 for vertically polarized incident light by using the captured image 510 for horizontally polarized incident light. Then, using the "new" captured image 520, standard particles 501 showing scattered light due to Rayleigh scattering can be identified. Note that the generation of the "new" captured image 520 is performed on the captured images of vertically polarized incident light at time t, time t-Δt, and time t+Δt. Note that, as in the first embodiment, it is sufficient to use captured images before and after time t, and they do not need to be at equal intervals.

[0046] The subsequent processing is the same as in the first embodiment, and the number of standard particles is counted using the "new" image. Similarly, the instrument settings are determined for each different concentration, and the final instrument settings that can correspond to each concentration within the range of those instrument settings are determined.

[0047] <Variation> The calibrated dispersion concentration measurement system 100 or 300 can also accurately measure the concentration of an ultrafine bubble dispersion. For example, an ultrafine bubble dispersion generated by passing pure water through a Venturi-structured nozzle can be placed in a container 20, an image can be acquired, and the number of scattered light (bright spots on the image) due to the ultrafine bubbles can be counted to calculate the concentration in the same way as in S250. Here, the count can be accurately performed by correcting the count using consecutive images, as in S240.

[0048] The procedure for measuring the concentration of an ultrafine bubble dispersion is described below. The dispersion concentration measurement system is the same as that of the first embodiment, and calibration with standard particles is performed according to the procedure shown in Figure 2. Here, an ultrafine bubble dispersion using tap water as the medium is used.

[0049] When using tap water as the medium, it contains impurities, so first, only tap water is placed in container 20, and the scattered light from impurities is counted using the image captured from the area irradiated with laser light 11. The counting can be done in the same way as in the first embodiment. Next, the ultrafine bubble dispersion is placed in container 20, laser light 11 is incident on it, an image is acquired, and the number of scattered lights is counted. The counting can be done in the same way as in the first embodiment.

[0050] The bright spots in this case include those caused by impurities in the dispersion and those caused by ultrafine bubbles. Therefore, the number of ultrafine bubbles can be considered to be the number obtained by subtracting the count obtained earlier when using tap water from this count. By dividing this number by the volume of the ultrafine bubble dispersion obtained by multiplying the imaging range by the depth of field, the concentration of the ultrafine bubble dispersion excluding impurities can be determined even when using tap water. [Explanation of symbols]

[0051] 10 Laser light source 20 containers 30 Imaging device 40 Processing Unit 50 Display device 100 Dispersion Concentration Measurement System 300 Dispersion Concentration Measurement System

Claims

1. A dispersion concentration measurement system for measuring the concentration of a dispersion consisting of particles and a solvent, A container for the dispersion, A laser light source, An imaging device that captures an image of the region where laser light from the laser light source is incident on the liquid in the container and generates an image; Processing device and Equipped with, The aforementioned processing apparatus is Based on the first image obtained by irradiating the container with the laser light while only the solvent is contained in the container, the number of bright spots is counted. Based on the second image obtained by irradiating the dispersion liquid in the container with the laser light, the number of bright spots is counted. The concentration of the dispersion is determined by subtracting the number of bright spots in the first image from the number of bright spots in the second image, and then dividing this result by the volume of the dispersion, which is obtained by multiplying the imaging range of the imaging device by the depth of field. A system for measuring the concentration of dispersions.

2. The dispersion concentration measurement system according to claim 1, wherein the processing apparatus determines whether or not there is overlap of the bright spots in the captured image at a certain time by comparing it with the bright spots in the captured image before and after that time, and if it is determined that there is overlap, it increases the number of bright spots in the captured image at the certain time to determine the concentration of the dispersion.

3. The dispersion concentration measurement system according to claim 1 or 2, wherein the settings of the imaging device and / or the laser light source are set such that the concentration obtained for the dispersion containing standard particles is within a predetermined range with respect to the actual concentration of the dispersion containing the standard particles.

4. The dispersion concentration measurement system according to claim 3, wherein the setting is the gain of the imaging device, the exposure time, or the output value of the laser light source.

5. The dispersion concentration measurement system according to claim 1, wherein the laser light from the laser light source is in the form of a sheet.

6. The dispersion concentration measurement system according to claim 1, wherein the particles are ultrafine bubbles.

7. A method for measuring the concentration of a dispersion consisting of particles and a solvent, The steps include counting the number of bright spots based on a first image obtained by irradiating a container with only the aforementioned solvent onto it using laser light, The steps include counting the number of bright spots based on a second image obtained by irradiating the dispersion liquid in the container with the laser light, The steps include: calculating the concentration of the dispersion by subtracting the number of bright spots in the first image from the number of bright spots in the second image, and then dividing the result by the volume of the dispersion obtained by multiplying the imaging range of the imaging device by the depth of field; A method for measuring the concentration of a dispersion, including [the specified substance].

8. The method for measuring the concentration of a dispersion according to claim 7, wherein in the counting step, the presence or absence of overlap of the bright spots in the captured image at a certain time is determined by comparing it with the bright spots in the captured image before and after the time, and if it is determined that there is an overlap, the number of bright spots in the captured image at the time is increased and counted.

9. The method for measuring the concentration of a dispersion according to claim 7 or 8, wherein the settings of the imaging device and / or laser light source for capturing the first and second imaging images are preset so that the concentration obtained for the dispersion containing standard particles is within a predetermined range with respect to the actual concentration of the dispersion containing the standard particles.

10. The method for measuring the concentration of a dispersion according to claim 7, wherein the particles are ultrafine bubbles.

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