Dispersion liquid concentration measurement system

Abstract

In order to accurately measure the concentration of even a low-concentration dispersion liquid, a dispersion liquid concentration measurement system according to the present invention comprises a container 20 for storing a dispersion liquid, a laser light source 10, an image-capture device 30 for capturing an image of a region where a laser beam 11 is incident on the dispersion liquid to generate a captured image, and a processing device 40, wherein the processing device 40 determines the concentration of the dispersion liquid containing standard particles by dividing the number of bright spots contained in the captured image of the dispersion liquid containing the standard particles by the volume of the dispersion liquid determined by multiplying the image-capturing range by the depth of field, and settings of the image-capture device 30 and / or the laser light source 10 are set so that the determined concentration of the dispersion liquid containing the standard particles is within a prescribed range with respect to the actual concentration.

Description

Dispersion concentration measurement system

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

[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.

[0003] Japanese Patent Publication No. 2024-061147

[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.

[0005] To solve the above problems, the dispersion concentration measurement system according to the present invention comprises a container for containing the dispersion, a laser light source, an imaging device that captures the region where the laser light is incident on the dispersion and generates an image, and a processing device. The processing device determines the concentration of the dispersion containing standard particles by dividing the number of bright spots in the image captured from the dispersion containing standard particles by the volume of the dispersion obtained by multiplying the imaging range by the depth of field. The settings of the imaging device and / or the laser light source are configured such that the determined concentration of the dispersion containing standard particles is within a predetermined range relative to the actual concentration.

[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.

[0007] This is a diagram showing a dispersion concentration measurement system according to the first embodiment. This is a flowchart showing the calibration procedure for the dispersion concentration measurement system according to the first embodiment. This is an example of an image captured according to the first embodiment. This is an example of an image captured to explain the process of counting the number of standard particles according to the first embodiment. This is a schematic diagram showing an image captured according to the second embodiment.

[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 scattered 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 the 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 that allow Rayleigh scattering light to 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 such as a telecentric lens, and it images a predetermined area of ​​the container 20 that is irradiated with laser light 11. 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, which is the irradiation direction of the laser light 11 (Y direction). The imaging range can be set to, for example, 5 [mm] × 1.4 [mm], but is not limited to this.

[0013] 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. It also has various calculation functions, such as determining density based on the processed images.

[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 captured images taken by the imaging device 30, images processed by the processing device 40, and the like.

[0015] Next, the calibration procedure for the dispersion concentration measurement system 100 will be explained according to the flowchart in Figure 2. The dispersion concentration measurement system 100 is calibrated using the calibration procedure in Figure 2 with standard particles, and can accurately measure the concentration of the dispersion even when the imaging range of the captured image 30 is widened.

[0016] First, several dispersions with different concentrations are prepared (S210). The dispersion is made by diluting a sample containing standard particles with a particle size of 100 nm with pure water, thereby uniformly dispersing the standard particles. The concentration is, for example, 10 ４ , 10 ５ , 10 ６ , 10 ７ , 10 ８ , 10 ９ The concentration is set to [units / mL], but at least two types should be prepared. Then, each dispersion is placed into container 20 individually.

[0017] Next, the user selects one of the dispersions prepared in S210 and sets it in a predetermined position. While the laser light source 10 is irradiating the container 20 with laser light 11, the imaging device 30 captures the irradiated area, and the processing device 40 acquires the resulting image (S220). At this time, the imaging device 30 is recording as a video, and the processing device 40 acquires a series of images in time. An example of an image is shown in Figure 3. As shown in Figure 3, pixels that receive scattered light due to the presence of standard particles show high brightness values.

[0018] Next, the processing unit 40 performs image processing on the acquired image to identify standard particles in the image (S230). For example, a group of pixels having a brightness value greater than or equal to a predetermined value is treated as a single standard particle, and its position information is associated with it for identification. Furthermore, by associating the distribution of brightness values ​​of the pixel group, its size, and the characteristic quantities of the circular light and dark regions, the standard particle can be identified with greater accuracy.

[0019] Next, the number of standard particles contained in the captured image is counted (S240). Specifically, this involves counting the number of standard particles at a certain time t in a series of captured images. However, if, for example, standard particles overlap in the captured image, they will be counted as one, making it impossible to count the exact number. Therefore, in this count, at least three captured images are used: the image at a certain time t, the image at t+Δt, and the image at t-Δt, to more accurately determine the number of standard particles in the image at time t. Δt is preferably 200 [ms], but may be a value within the range of approximately 200 ± 50 [ms].

[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 the captured image 450 has a one-to-one correspondence with any of the standard particles identified in S230 for the 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, it is not determined that there is a one-to-one correspondence. 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 the image captured at time t 450 is within a predetermined range and its features match those of standard particle 413 in the image captured at time t-Δt 470 (Figure 4(C)), 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 the image captured at time 450 is determined to have a correspondence with standard particles 430 and 431 in the image captured at time 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 feature quantities 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 obtained 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 volume of the dispersion obtained 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. The device settings are at least one of 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 performing the same 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 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 set 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 used 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 a device setting that satisfies all of these conditions is 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, a device setting corresponding to all concentrations can be determined as (imaging device 30: exposure time 15 [ms], gain 15 [dB], laser light source 10: output 1.0 [W]), which satisfies the device settings for concentrations A and B.

[0033] As described above, since the concentration measurement system 100 of the dispersion liquid is appropriately calibrated, accurate concentration measurement can be performed even when the imaging range is expanded. Thus, by using a plurality of dispersion liquids with different concentrations, device settings that can handle dispersion liquids with different concentrations are sought. For example, in an imaging image at a high concentration, if the value of the device setting is not appropriate, the bright spots become large and the counting may not be properly performed. Therefore, a device setting that reduces the overlap of bright spots is preferable. However, if adjusted according to this setting, there is a risk that the error will increase when determining the concentration without the scattered light being captured in the imaging image at a low concentration. Therefore, calibration according to an embodiment of the present invention is performed to set the device so that concentration measurement can be appropriately performed even for dispersion liquids with different concentrations.

[0034] <Second Embodiment> In the second embodiment, when the imaging image includes bright spots due to particles other than the standard particles, it is possible to exclude them and identify the standard particles.

[0035] [[ID=**7**]] The concentration measurement system 300 of the dispersion liquid according to the second embodiment includes, in addition to the configuration of the concentration measurement system 100 of 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, a lens or the like may be added to form the light into a sheet shape 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 concentration measurement system 300 of the dispersion liquid will be described. This calibration procedure follows the calibration procedure shown in FIG. 2.

[0037] First, in S210, it is to prepare a plurality of dispersion liquids with different concentrations containing standard particles, which is the same as in the first embodiment. That is, for example, the particle size is 100 [nm] and the concentration is 10 ４ 、10 ５ 、10 ６ 、10 ７ 、10８ and 10 ９ is [number / mL]. The dispersion medium contains impurities, and for example, tap water is used.

[0038] Next, an imaging image is acquired in S220. Specifically, an imaging image when laser light with vertical polarization is irradiated on the container 20 is acquired. Next, the rotation mechanism 320 is used to switch so that vertical polarization is incident, and an imaging image when laser light with horizontal polarization is irradiated is acquired. Note that this order may be reversed.

[0039] FIG. 5 shows an example of an imaging image according to the second embodiment. In FIG. 5, circles indicate regions with high luminance. FIG. 5(A) shows an imaging image 510 when incident light with vertical polarization, and FIG. 5(B) shows an imaging image 520 when incident light with horizontal polarization.

[0040] Here, Equation 1 represents the scattered light intensity I due to Rayleigh scattering in incident light with vertical polarization １ and Equation 2 represents the scattered light intensity I due to Rayleigh scattering in incident light with horizontal polarization ２ In Equation 1 and Equation 2, I ０ is a device constant such as gain, exposure time, and laser output value, a is the particle diameter, k is the wave number, r is the observation 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]

[0042]

[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 becomes 0. Therefore, the bright spots present in the imaging image when incident light with horizontal polarization are due to scattered light by Mie scattering or the like, and it is assumed that foreign matter is mixed in because the particle diameter of those particles is considerably larger than that of the standard particles.

[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. Then, 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] <Modification> In the calibrated dispersion concentration measurement system 100 or 300, the concentration of an ultrafine bubble dispersion can also be accurately measured. 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.

[0051] 10 Laser light source 20 Container 30 Imaging device 40 Processing device 50 Display device 100 Dispersion concentration measurement system 300 Dispersion concentration measurement system

Claims

1. A dispersion concentration measurement system comprising: a container for containing a dispersion; a laser light source; an imaging device for imaging the region in which laser light from the laser light source is incident on the dispersion and generating an image; and a processing device, wherein the processing device determines the concentration of the dispersion containing standard particles by dividing the number of bright spots in the image obtained from imaging the dispersion containing standard particles by the volume of the dispersion containing standard particles, which is obtained by multiplying the imaging range of the imaging device by the depth of field; and the settings of the imaging device and / or the laser light source are set so that the determined concentration of the dispersion containing standard particles is within a predetermined range relative to the actual concentration of the dispersion containing standard particles.

2. The dispersion concentration measurement system according to claim 1, wherein the processing device 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 that time to determine the concentration of the dispersion.

3. The dispersion concentration measurement system according to claim 1 or 2, wherein the settings are the gain of the imaging device, the exposure time, and the output value of the laser light source.

4. The dispersion concentration measurement system according to claim 2, wherein the processing apparatus targets only the bright spots within a predetermined range of the captured image for comparison.

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

6. A dispersion concentration measurement system comprising: a container for containing a dispersion containing particles; a laser light source that emits horizontally polarized incident light and vertically polarized incident light; an imaging device installed perpendicular to the direction of incidence that images the regions where the horizontally polarized incident light and the vertically polarized incident light are incident on the dispersion and generates an image; and a processing device, wherein the processing device identifies bright spots in the image of the horizontally polarized incident light, generates a new image by removing the bright spots corresponding to the identified bright spots from the image of the vertically polarized incident light, and determines the concentration of the dispersion by dividing the number of bright spots in the new image by the volume of the dispersion obtained by multiplying the imaging range of the imaging device by the depth of field.

7. The dispersion concentration measurement system according to claim 6, wherein the processing device 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 that time to determine the concentration of the dispersion.

8. The dispersion concentration measurement system according to claim 6 or 7, wherein the settings of the imaging device and / or the laser light source are set so that the determined concentration is within a predetermined range with respect to the actual concentration of the dispersion.

9. The dispersion concentration measurement system according to claim 8, wherein the settings are the gain of the imaging device, the exposure time, and the output value of the laser light source.

10. The dispersion concentration measurement system according to claim 6, wherein the laser light is in the form of a sheet.

11. A dispersion concentration measurement system comprising: a container for containing a dispersion containing ultrafine bubbles; a laser light source; an imaging device for imaging the region in which laser light from the laser light source is incident on the dispersion and generating an image; and a processing device, wherein the processing device determines the concentration of the dispersion by dividing the number of bright spots included in the image by the volume of the dispersion, which is obtained by multiplying the imaging range of the imaging device by the depth of field.

12. The dispersion concentration measurement system according to claim 11, wherein 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.

13. The dispersion concentration measurement system according to claim 11, wherein the processing device 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 that time to determine the concentration of the dispersion.

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