Particle measurement device, method, and program

Abstract

Provided is a particle measuring device that can be realized at a low cost and that can measure particles with easy operation. According to an embodiment, this particle measurement device comprises: a light source that supplies illumination light for illuminating particles in a liquid; an imaging unit that images the illumination light that has passed through the particles; and a measurement unit that measures the distance between the particles and the imaging unit on the basis of the transmitted light intensity of the illumination light captured by the imaging unit and the known particle size and refractive index of the particles.

Description

Particle measuring device, method, and program

[0001] An embodiment of the present invention relates to a particle measuring device, a method, and a program for measuring particles contained in treated water in organic wastewater treatment.

[0002] The activated sludge process is generally used to treat organic wastewater such as municipal sewage. In the activated sludge process, air is supplied to the treated water, and the organic matter in the water is decomposed by the action of the organic matter.

[0003] Bacillus bacteria (hereafter simply referred to as "Bacillus") are a typical useful microorganism found in activated sludge. The enzymes and antibiotics produced by Bacillus have a bacteriolytic effect, so treatment facilities where Bacillus dominates produce less excess sludge. Bacillus also plays a role in stopping the activity of sulfate-reducing bacteria, resulting in less odor generation.

[0004] Therefore, it is important to know the number of bacilli in order to determine whether or not there are sufficient bacilli in the treated water.

[0005] Japanese Patent Application Publication No. 2021-135129

[0006] “Bacteria detection with thin wetting film lensless imaging”, BIOMEDICAL OPTICS EXPRESS 1(3) 762-770 (2010)

[0007] The problem to be solved by the present invention is to provide a particle measuring device, method, and program that can be implemented at low cost and that can measure particles with simple operations.

[0008] The particle measuring device of the embodiment includes a light source that supplies illumination light to illuminate particles in a liquid, an imaging unit that images the illumination light that has passed through the particles, and a measuring unit that measures the distance between the particle and the imaging unit based on the transmitted light intensity of the illumination light imaged by the imaging unit and the known particle size and refractive index of the particle.

[0009] FIG. 1 is a block diagram showing an example of the configuration of a particle measuring device to which a particle measuring method according to an embodiment of the present invention is applied. FIG. 2 is a flowchart showing a measurement flow using a particle measuring device to which a particle measuring method according to an embodiment of the present invention is applied. FIG. 3 is a diagram showing the tracing of light rays from illumination light incident on particles in a sample aqueous solution, passing through the particles, and reaching a light-receiving section of an image sensor. FIG. 4 is an image captured when a pure aqueous solution containing acrylic standard particles is dropped onto an image sensor as a sample aqueous solution. FIG. 5 is an enlarged image containing three types of acrylic standard particles (hereinafter referred to as "Particle A," "Particle B," and "Particle C") that appear differently in the image shown in FIG. 4. FIG. 6 is a diagram showing the transmitted light intensity distributions measured for the three types of acrylic standard particles. FIG. 7 is an image captured when a sample aqueous solution containing a Bacillus spore strain is dropped onto an image sensor. FIG. 8 is a diagram showing the transmitted light intensity distribution of Bacillus spores extracted from the images shown in FIGS. 7(a) and 7(b).

[0010] Hereinafter, embodiments and examples of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc., are not necessarily the same as those in reality. Furthermore, even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals, and detailed and redundant explanations will be omitted as appropriate.

[0011] FIG. 1 is a block diagram showing an example of the configuration of a particle measuring device to which a particle measuring method according to an embodiment of the present invention is applied.

[0012] FIG. 2 is a flowchart showing a measurement flow by a particle measuring device to which a particle measuring method according to an embodiment of the present invention is applied.

[0013] That is, the particle measuring device 10 of this embodiment includes a light source 12, an imaging unit 16, a particle determination unit 18, a measurement unit 20, a contact determination unit 22, a counting unit 24, a database 26, and a machine learning unit 26.

[0014] The particle measuring device 10 is used to measure target particles, such as Bacillus bacteria, contained in treated water, such as organic wastewater, including municipal sewage. To this end, a predetermined amount (e.g., about 1 cc) of sample aqueous solution S is measured from the treated water and supplied to the particle measuring device 10 (S1).

[0015] As shown in FIG. 3, which will be described later, the imaging unit 16 includes a surface 16a of an image sensor such as a CCD or CMOS, and an internal light receiving unit 16b.

[0016] The sample aqueous solution S measured in step S1 is dripped onto the surface 16a of the image sensor (S2). After dripping the sample aqueous solution S, a certain time (e.g., about 10 minutes) is waited until the particles contained in the sample aqueous solution S float or settle and the effects of convection and the like stabilize (S3).

[0017] The light source 12 is provided above the image capturing unit 16, and after the aforementioned certain time (e.g., about 10 minutes) has elapsed, it emits illumination light H in a vertical direction toward the image capturing unit 16. The illumination light H illuminates the sample aqueous solution S. As a result, the particles to be measured contained in the sample aqueous solution S are illuminated by the illumination light H.

[0018] The imaging unit 16 receives the illumination light H that has passed through the particles via the surface 16a of the image sensor with the light receiving unit 16b, and captures an image (S4).

[0019] The particle determination unit 18 determines that a portion of the image G captured by the imaging unit 16 where the transmitted light intensity is equal to or greater than a preset threshold corresponds to a particle. The threshold can be determined, for example, from the background light intensity of the image G, but is not limited to this.

[0020] The counting unit 24 counts the portions determined by the particle determination unit 18 to correspond to particles W (S5). To perform this counting, the counting unit 24 can count the portions determined to correspond to particles by, for example, displaying the portions of the image G determined by the particle determination unit 18 to correspond to particles in a color different from the background, and counting the portions displayed in the different color.

[0021] The database 26 stores light intensity distribution information of portions of the image G that are determined by the particle determination unit 18 to correspond to particles.

[0022] The machine learning unit 28 performs image analysis using machine learning on the light intensity distribution information stored in the database 26 .

[0023] As a result, when a new image G is captured by the imaging unit 16, the particle determination unit 18 can determine the parts corresponding to particles in the new image G based on the analysis results by the machine learning unit 28 without using the aforementioned threshold value.

[0024] The measuring unit 20 measures the distance between the particle determined by the particle determining unit 18 and the surface 16a of the image sensor. This measurement is performed based on the transmitted light intensity of the illumination light H captured by the image capturing unit 16 and the known particle size and refractive index n of the particle W. ２ For example, since Bacillus particles have a spherical shape, when the particles are Bacillus, the known particle size of the particles can be the diameter of the spherical Bacillus.

[0025] The contact determination unit 22 determines whether or not the particle is in contact with the surface 16 a of the image sensor based on the distance measured by the measurement unit 20 .

[0026] Next, in the following examples, the results of verifying the validity of measurements made by the particle measuring device of this embodiment will be described.

[0027] Example 1 In Example 1, the results of calculation-based verification of the measurement validity of the particle measuring device of this embodiment will be described.

[0028] FIG. 3 is a diagram showing the tracing of light rays from illumination light, which is parallel light incident on particles in a sample aqueous solution, through the particles to the light receiving section of the image sensor.

[0029] The illumination light H from the light source 12 is parallel light directed in the vertical direction and illuminates the aqueous sample solution S.

[0030] The illumination light H is bent like a lens by spherical particles W to be measured, such as Bacillus bacteria, in the sample aqueous solution S, and is then focused onto the light receiving section 16b via the surface 16a of the image sensor.

[0031] The following equation is a ray tracing determinant of parallel light passing through a spherical particle W.

[0032]

[0033] The known ray tracing determinant shown above is given by adding the radius r of the spherical particle W and the refractive index n of the particle W. １ and the refractive index n of the aqueous solution S ２ The relative refractive index n = n ２ / n １ Substituting the above, the position x on the x-axis coordinate for particle W is ０ (-r≦x ０ The illumination light H, which is parallel light (u=0) incident on the light receiving unit 16b at a distance r, passes through the particle W and reaches a position x on the x-axis coordinate system, which is a distance l between the center of the particle W and the light receiving unit 16b. １ and its angle u １ For simplicity, the distance traveled inside the particle W is not taken into consideration and the light emitted from the particle is assumed to travel the same distance 1.

[0034] At this time, x ０ >x １ If so, it indicates that the illumination light H that has passed through the particle W is condensed. From the experimentally acquired image, the position x １ If we know the distance l, we can calculate it.

[0035] Therefore, by subtracting the distance L between the surface 16a of the image sensor onto which the sample aqueous solution S is dropped and the light receiving unit 16b from the distance l, it is possible to determine whether the particle W is in contact with the surface of the image sensor 16a or floating at a distance (l-L) away.

[0036] Furthermore, by utilizing this principle, it is possible to distinguish between particles that have settled and particles that have not settled, even though they have the same particle size.

[0037] Thus, according to Example 1, the validity of the measurement by the particle measuring device of this embodiment was verified using the calculation shown in the ray tracing determinant described above.

[0038] Example 2 In Example 2, experimental verification results of the measurement validity of the particle measuring device of this embodiment will be described.

[0039] FIG. 4 shows the radius r=15 μm and the refractive index n １ A pure aqueous solution containing spherical acrylic standard particles (refractive index n ２ = 1.33) was dropped onto the image sensor as a sample aqueous solution.

[0040] FIG. 5 is an enlarged image containing three types of acrylic standard particles (hereinafter referred to as "particle A," "particle B," and "particle C") that appear in three different ways in the image shown in FIG.

[0041] 5(a) shows enlarged images of particle A and particle B, and FIG. 5(b) shows an enlarged image of particle C.

[0042] FIG. 6 shows the distribution of transmitted light intensities measured for three types of acrylic standard particles.

[0043] The image shown in Fig. 4 indicates that particle A accounts for the largest proportion of the three types of particles A, B, and C. Particle A, enlarged and displayed in Fig. 5(a), settles in the sample aqueous solution S due to the specific gravity of the acrylic particle, and comes into contact with the surface 16a of the image sensor.

[0044] Particle A is shown as a region having a significantly higher transmitted light intensity than the background, as shown in Figure 6(a). The experimental value for the length of this region was 17.1 µm, as shown in Figure 6(a).

[0045] Furthermore, if we assume that the distance l when particle A settles and contacts the surface 16a of the image sensor is distance l = r = 15 μm, then from the ray tracing determinant described above, the position x １ = 11.4 μm, and the length of the region where the transmitted light intensity is significantly greater than the background is x １ The calculation is ×2=22.8 μm.

[0046] In reality, there is a distance L between the surface 16a of the image sensor and the light receiving portion 16b, and this distance L causes a discrepancy between the calculated value and the experimental value.

[0047] Therefore, it can be inferred from the closeness of the calculated value (22.8 μm) and the experimental value (17.1 μm) that particle A, whose experimental value for the length having a significantly greater transmitted light intensity than the background is 17.1 μm, has settled and contacted the surface 16 a of the image sensor.

[0048] As shown in FIG. 6(b), particle B had an experimental length of 9.1 μm, at which the transmitted light intensity was significantly greater than that of the background.

[0049] This value is different from the experimental value (17.1 μm) of particle A, so it can be seen that particle B is not in contact with the surface 16 a of the image sensor. When particle B is not in contact with the surface 16 a of the image sensor, there are two types of images formed on the light receiving section 16 b: one in which the image is not inverted, and one in which the image is inverted. Therefore, by adding x １ = 9.1 / 2 = 4.55 μm, and x １ = -9.1 / 2 = -4.55 μm １ When the distance l was calculated by substituting the above, the distances l=43.43 μm and l=81.25 μm were obtained.

[0050] Therefore, the B particle is determined to be at a distance 1=43.43 μm or a distance 1=81.25 μm from the light receiving section 16b.

[0051] As shown in FIG. 6B, particle C has a lower transmitted light intensity than the background. Therefore, particle C is far from the light receiving unit 16b, and x ０ <x １ When a particle like particle C is far from the light receiving unit 16b and the transmitted light intensity is smaller than that of the background, as shown in FIG. 6C, distance measurement is not possible.

[0052] Thus, according to Example 2, the validity of the measurement by the particle measuring device of this embodiment was verified based on the experimental results.

[0053] Example 3 In Example 3, an example of application of the particle measuring device of this embodiment to detection of Bacillus spores will be described.

[0054] FIG. 7 shows an image captured when a sample aqueous solution containing a spore strain of Bacillus is dropped onto an image sensor.

[0055] FIG. 7(a) is an image obtained from a certain field of view, and FIG. 7(b) is an enlarged image of a part of FIG. 7(a).

[0056] Bacillus spores have the property of settling. Therefore, in this example, the experiment was conducted under the assumption that the Bacillus spores would settle and contact the surface 16a of the image sensor. However, due to the influence of thermal convection caused by the heat of the surface 16a of the image sensor, settling was prevented, and many convecting Bacillus spores were observed. For this reason, the sample aqueous solution S was dropped onto the surface 16a of the image sensor, and a cover glass was placed over it, and the images shown in Figures 7(a) and 7(b) were acquired.

[0057] FIG. 8 is a diagram showing the transmitted light intensity distribution of Bacillus spores extracted from the images shown in FIGS. 7( a ) and 7 ( b ).

[0058] As shown in FIG. 8, the experimental value of the length at which the transmitted light intensity of Bacillus spores becomes significantly greater than the background light was 2.9 μm.

[0059] Next, l = r = 0.5 μm, refractive index n １ = 1.52, and from the ray tracing determinant described above, the position x when the Bacillus spore settles and contacts the surface 16a of the image sensor is １ Calculating x １ = 0.4 μm, and the calculated length of the part where the transmitted light intensity is significantly greater than the background is x １ ×2=0.8 μm.

[0060] As described above, there is a discrepancy between the experimental value (2.9 μm) and the calculated value (0.8 μm), but in reality, there is a distance L between the surface 16 a of the image sensor and the light receiving section 16 b, and the discrepancy between the experimental value and the calculated value occurs due to this distance L. In addition, since the particle size of Bacillus spores is small, the influence of light diffraction also contributes to the discrepancy.

[0061] Thus, according to Example 3, the settled Bacillus spores act like a lens to focus the illumination light H, and the intensity of the light transmitted through the Bacillus spores is significantly greater than the intensity of the background light. This demonstrates that Bacillus spores can be specifically detected from the intensity of the transmitted light.

[0062] As described above, according to the particle measuring device of this embodiment, the sample aqueous solution S can be dropped directly onto the surface 16 a of the image sensor, and the positions of particles such as Bacillus bacteria settling in the sample aqueous solution S can be measured based on the particle size and refractive index of the particles W.

[0063] In particular, the particle measuring device of this embodiment does not require an optical system such as a microscope, and can perform measurements using only an image sensor. Therefore, not only can it be realized at low cost, but the configuration can also be simplified because a complex mechanism for adjusting the distance of the objective lens is not required. Moreover, since there is no need for complex preparation operations such as covering the image sensor with a thin painted film to detect fungi, particle measurement can be performed easily and in a short time.

[0064] Furthermore, with the particle measuring device of this embodiment, for particles with known particle diameters, the position from the image sensor surface 16 a can also be measured, making it possible to determine whether the particle is floating or adhered to the image sensor surface 16 a. This makes it possible to specifically identify particles that have the characteristic of settling, such as Bacillus spores, from the pigment information, morphological information, and transmitted light intensity distribution of the acquired image.

[0065] Furthermore, with the particle measuring device of this embodiment, it is possible to determine the position on the image sensor where a particle with a known particle size is floating or adhered, based on the transmitted light intensity distribution of the particle. This makes it possible to obtain imaging depth information, which could not be obtained with the conventional imaging method in which the sample aqueous solution S is dropped onto the surface 16 a of the image sensor.

[0066] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

Claims

1. A particle measurement device comprising: a light source that supplies illumination light for illuminating particles in a liquid; an imaging unit that images the illumination light transmitted through the particles; and a measurement unit that measures the distance between the particles and the imaging unit based on the transmitted light intensity of the illumination light imaged by the imaging unit, the known particle size, and the refractive index of the particles.

2. The particle measurement device according to claim 1, further comprising a contact determination unit that determines whether the particles are in contact with the imaging unit based on the distance measured by the measurement unit.

3. The particle measurement device according to claim 1, further comprising a particle determination unit that determines that a portion where the transmitted light intensity is equal to or greater than a preset threshold value in the image imaged by the imaging unit corresponds to the particles.

4. The particle measurement device according to claim 3, wherein the threshold value is determined from the background light intensity of the image.

5. The particle measurement device according to claim 3, further comprising a counting unit that counts the portions determined to correspond to the particles by the particle determination unit.

6. The particle measurement device according to claim 5, wherein the counting unit counts the portions determined to correspond to the particles by causing the particle determination unit to display, in the image, the portions determined to correspond to the particles in a color different from the background and counting the portions displayed in the different color.

7. The particle measurement device according to claim 3, further comprising: a database that stores the light intensity distribution information of the portions determined to correspond to the particles by the particle determination unit; and a machine learning unit that performs image analysis by machine learning on the light intensity distribution information stored in the database. When a new image is imaged by the imaging unit, the particle determination unit determines the portions corresponding to the particles in the new image based on the analysis result by the machine learning unit without using the threshold value.

8. A particle measurement method performed by a particle measurement device, the particle measurement device: illuminating particles in a liquid with illumination light from a light source; imaging the illumination light transmitted through the particles by an imaging unit; and measuring the distance between the particles and the imaging unit based on the transmitted light intensity of the imaged illumination light, the known particle size, and the refractive index of the particles.

9. A program for causing a processor to realize a function of illuminating particles in a liquid with illumination light with respect to a light source, a function of imaging the illumination light transmitted through the particles by an imaging unit, and a function of measuring a distance between the particles and the imaging unit based on the intensity of the transmitted light of the imaged illumination light, the known particle size, and the refractive index of the particles.

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