阅读说明：本技术 粒子尺寸测定装置及测定方法 (Particle size measuring apparatus and measuring method ) 是由 三泽智也 于 2020-04-02 设计创作，主要内容包括：提供一种粒子尺寸测定装置及测定方法,能够测定更小的粒子尺寸。用于测定粒子的尺寸的粒子尺寸测定装置(1)具备：第一光源(2),其向包含粒子的试料(9)照射平行光(10)；第一摄像装置(4),其配置为隔着试料而与第一光源大致对置,用于拍摄试料；以及图像解析部(7),其对由第一摄像装置拍摄到的图像进行解析,第一摄像装置与第一光源大致对置地进行配置,使得能够通过第一摄像装置来拍摄入射到粒子的平行光以规定角度(θth)以下散射的散射光,图像解析部基于由第一摄像装置拍摄到的散射光图像,算出粒子的尺寸。(Provided are a particle size measuring device and a measuring method, which can measure smaller particle sizes. A particle size measurement device (1) for measuring the size of particles is provided with: a first light source (2) that irradiates a sample (9) containing particles with collimated light (10); a first imaging device (4) which is arranged to substantially face the first light source with the sample interposed therebetween and which images the sample; and an image analysis unit (7) that analyzes the image captured by the first imaging device, the first imaging device being disposed substantially opposite to the first light source so that scattered light, which is scattered at a predetermined angle (θ th) or less by parallel light incident on the particle, can be captured by the first imaging device, and the image analysis unit calculating the size of the particle based on the scattered light image captured by the first imaging device.)

1. A particle size measuring apparatus for measuring the size of particles,

the particle size measuring apparatus includes:

a first light source that irradiates a sample containing particles with collimated light;

a first imaging device arranged to substantially face the first light source with the sample interposed therebetween, and configured to image the sample; and

an image analysis unit that analyzes the image captured by the first imaging device,

the first imaging device is disposed substantially opposite to the first light source in a predetermined manner so that scattered light scattered at a predetermined angle or less of parallel light incident on the particles can be imaged by the first imaging device,

the image analysis unit calculates the size of the particle based on the scattered light image captured by the first imaging device.

2. The particle sizing device according to claim 1,

the predetermined arrangement indicates that the optical axis of the first imaging device and the direction of the parallel light are arranged so as to intersect at the predetermined angle or less.

3. The particle sizing device according to claim 2,

the predetermined angle is determined as a threshold value of a scattering angle that can determine the size of a particle according to a difference in intensity of scattered light in the particle.

4. The particle sizing device according to claim 3,

the image analysis unit further acquires a particle shape image indicating the shape of the particle, calculates the particle size from the acquired particle shape image, and selects and outputs any one of the particle sizes based on the calculated particle size and the particle size calculated from the scattered light image.

5. The particle sizing device according to claim 4,

the image analysis unit selects the particle size calculated from the particle shape image when the particle size calculated from the particle shape image is equal to or larger than a predetermined size set in advance, and otherwise selects the particle size calculated from the scattered light image.

6. The particle sizing device according to claim 4 or 5,

the particle size measuring apparatus further includes a second light source that irradiates the sample with light from a direction substantially coincident with an optical axis of the first imaging device in order to image the particle shape image by the first imaging device.

7. The particle sizing device according to claim 4 or 5,

the particle size measuring apparatus further includes a second imaging device having a focus in the vicinity of the sample in the same manner as the first imaging device,

the second imaging device images the particle shape image by using parallel light irradiated from the first light source toward a sample.

8. A particle size measuring method for measuring the size of particles,

the particle size measuring method includes:

an irradiation step of irradiating a sample containing particles with collimated light from a first light source;

an imaging step of imaging the sample by a first imaging device disposed so as to substantially face the first light source with the sample interposed therebetween; and

an analysis step of analyzing the image captured by the first imaging device by an image analysis unit,

the first imaging device is disposed substantially opposite to the first light source so that scattered light scattered at a predetermined angle or less of parallel light incident on the particles can be imaged by the first imaging device,

in the analyzing step, the size of the particle is calculated based on the scattered light image captured by the first imaging device.

9. A particle size measuring apparatus includes:

a plurality of light sources for irradiating a sample with parallel light;

a color imaging device that divides scattered light of the parallel light scattered by the sample into a plurality of wavelength bands and images the divided light; and

an image analysis unit for analyzing the captured image,

the light sources have different wavelengths, scattered light intensities corresponding to the light sources are extracted from the captured image, and the size of the particle is calculated based on the extracted scattered light intensities.

10. The particle sizing device according to claim 9,

the color imaging device images small-angle scattered light as the scattered light.

11. The particle sizing device according to claim 9,

when the scattered light intensity corresponding to each light source is extracted from the captured image, correction is performed based on the spectral characteristics of the color imaging device.

12. The particle sizing device according to claim 11,

the parameters used for the correction are determined in advance by measurement.

13. The particle sizing device according to claim 9,

the output of each light source is adjusted in accordance with the characteristics of the sample.

Technical Field

The present invention relates to a particle size measuring apparatus and a particle size measuring method.

Background

As a technique for measuring the particle size distribution of a sample, japanese patent laid-open No. 2009-156595 (patent document 1) is known. In this publication, a light source for irradiating a sample with light of a single wavelength and an image sensor for capturing a projection image of the sample are provided, and the particle size is calculated by analyzing an image captured by the image sensor.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open No. 2009.156595

Disclosure of Invention

Problems to be solved by the invention

In the technique of patent document 1, one particle is recognized from a captured image, and the particle size is calculated from the shape of the recognized particle. However, there is a limit to the particle size that can be optically recognized, and it is generally difficult to recognize particles of 1 μm or less.

The present invention has been made in view of the above problems, and an object thereof is to provide a particle size measuring apparatus and a particle size measuring method capable of measuring a smaller particle size.

Means for solving the problems

In order to solve the above problem, a particle size measuring apparatus according to an aspect of the present invention is a particle size measuring apparatus for measuring a size of a particle, including: a first light source that irradiates a sample containing particles with collimated light; a first imaging device arranged to substantially face the first light source with the sample interposed therebetween, for imaging the sample; and an image analysis unit configured to analyze an image captured by the first imaging device, the first imaging device being disposed substantially opposite to the first light source so as to capture scattered light in which parallel light incident on the particle is scattered at a predetermined angle or less by the first imaging device, the image analysis unit calculating a size of the particle based on the scattered light image captured by the first imaging device.

Effects of the invention

According to the present invention, since the first imaging device images scattered light in which parallel light incident on the particle is scattered at a predetermined angle or less, a smaller size can be measured as compared with a case where an image of the particle is captured.

Drawings

FIG. 1 is a schematic diagram of a particle size distribution measuring apparatus.

Fig. 2 is an explanatory view schematically showing a relationship between particles and parallel light and scattered light.

Fig. 3 is an explanatory diagram showing an example of the light shielding plate.

Fig. 4 is an explanatory diagram showing an example of the beam shape of the parallel light.

Fig. 5 is a configuration diagram of the measurement unit.

Fig. 6 is an explanatory diagram showing an example of an image of scattered light.

Fig. 7 is a characteristic diagram showing characteristics of scattered light intensity with respect to a scattering angle and a particle size.

FIG. 8 is a schematic diagram of a particle size distribution measuring apparatus according to a second embodiment.

FIG. 9 is a flowchart of the particle size distribution measurement process.

Fig. 10 is a characteristic diagram showing a relationship between particle size and intensity of scattered light.

FIG. 11 is a schematic diagram of a particle size distribution measuring apparatus according to a third embodiment.

FIG. 12 is a diagram showing the structure of a particle size distribution measuring apparatus according to a fourth embodiment.

FIG. 13 is a flowchart of the particle size distribution measurement process.

Fig. 14 is a characteristic diagram showing a relationship between particle size and scattered light intensity in the case where the wavelength of parallel light is changed.

Fig. 15 shows an example of arrangement of light sources according to a modification.

Description of reference numerals:

1. 1A, 1B, 1C: a particle size distribution measuring device; 2. 12, 15, 18: a light source; 3: a measurement section; 4. 4(1), 4 (2): a microscope; 5. 5(1), 5(2), 5C: an image pickup unit; 6. 6(1), 6 (2): a visor; 7. 7A, 7B, 7C: an image processing unit; 8: a control unit; 9: a test material; 10. 14, 16, 21: parallel light; 11. 17: an optical axis of the camera system; 19. 20: a mirror; 91: particles.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The particle size measuring apparatus according to the present embodiment can be used as a particle size distribution measuring apparatus, for example. The particle size measuring apparatus according to the present embodiment can be used in a static environment such as a laboratory, and can also be used in a dynamic environment such as a factory or a workshop. Further, the particle size measuring apparatus according to the present embodiment can measure the particle size by stopping the sample, and can also measure the particle size while continuously transporting the sample.

As will be described later, the particle size distribution measuring apparatus 1 as a particle size measuring apparatus according to the present embodiment causes parallel light to enter particles to generate small-angle scattered light of a predetermined angle or less, and calculates the particle size from an image of the scattered light. Therefore, a smaller size can be measured than in the case of measuring an image of the shadow of the particle.

[ example 1]

A first embodiment will be described with reference to fig. 1 to 7. Fig. 1 shows a schematic configuration of a particle size distribution measuring apparatus 1 in the present embodiment. The particle size distribution measuring apparatus 1 can include, for example, a light source 2, a measuring section 3, a microscope 4, an imaging section 5, a light shielding plate 6, an image processing section 7, and a control section 8.

The light source 2, which is an example of the "first light source", irradiates the parallel light 10 toward the sample 9 disposed in the measurement unit 3. For the light emitting element used for the light source 2, for example, an LED, a laser, or the like can be used. When a laser is used, a spot may be generated by light interference of a particle group included in the sample 9. On the other hand, when a laser is used, the coherence may be reduced by providing a diffuser, a speckle eliminator, or the like, for example.

Here, the optical axis of the parallel light 10 is shifted by an angle θ th shown in the drawing with respect to the optical axis 11 of the microscope 4. The parallel light 10 is set such that the distribution width of the parallelism with respect to the optical axis thereof is sufficiently small compared to the angle θ th.

The beam size and shape of the parallel light 10 are designed so that components that travel straight without being scattered by the particles 91 (see fig. 2) in the sample 9 do not enter the imaging unit 5, and so that only light scattered by the particles 91 is imaged by the microscope 4 and the entire field of view of the microscope 4 in the sample 9 can be irradiated.

The structure of the measuring unit 3 will be described later with reference to fig. 5. The microscope 4, which is an example of the "first imaging device", is disposed substantially opposite to the light source 2 with the measurement unit 3 interposed therebetween. The microscope 4 converts incident light (here, scattered light generated by particles) into an electric signal by the imaging unit 5, generates image data, and sends the image data to the image processing unit 7.

Here, the light source 2 and the microscope 4 are substantially opposed to each other with the measurement unit 3 having the sample 9 interposed therebetween means that the parallel light 10 of the light source 2 does not coincide with the optical axis 11 of the microscope 4, that is, the parallel light 10 of the light source 2 does not parallel to and intersect with the optical axis 11 of the microscope 4. More specifically, the light source 2 and the microscope 4 are disposed so as to substantially face each other with the measurement unit 3 interposed therebetween, that is, so that the parallel light 10 of the light source 2 and the optical axis 11 of the microscope 4 intersect each other at a predetermined angle θ th smaller than 90 °.

The light shielding plate 6 for preventing unnecessary light (here, light directly incident from the light source 2) from entering the microscope 4 can be provided at the incident portion of the microscope 4. An example of the light shielding plate 6 is described later in fig. 3.

The image processing unit 7, which is an example of the "image analyzing unit", calculates the particle size based on the intensity of the scattered light. The function as the image processing unit 7 is realized by reading and executing a computer program 71 stored in a memory (not shown) by a microprocessor (not shown). The image processing unit 7 calculates the size of particles included in the scattered light image based on the scattered light image acquired from the imaging unit 5 of the microscope 4. The calculation result of the image processing unit 7 is sent to the control unit 8. The image processing unit 7 may output a signal for monitoring the measurement state to an external display (not shown) or the like.

The control unit 8 controls the operation of the particle size distribution measuring apparatus 1. The control unit 8 controls, for example, the lighting of the light source 2 or adjusts the measurement unit 3. The control unit 8 may also generate an alarm signal based on the measurement result of the image processing unit 7, or may transmit information such as the particle size or the particle size distribution to another system outside the figure.

The control unit 8 can be configured as a computer including a microprocessor, a memory, an interface circuit, and the like, for example. In this case, the microprocessor reads and executes a predetermined computer program stored in the memory, thereby causing the computer to function as the control unit 8.

Instead of the example of being realized by a computer or a computer program, the image processing unit 7 or the control unit 8 may be realized mainly by a hardware circuit. In this case, hardware that can change the connection configuration of the circuit elements according to data for controlling the circuit configuration can be used.

When the image processing unit 7 or the control unit 8 is implemented by a computer or a computer program, a part or all of the computer program or a part or all of the data used may be stored in the recording medium MM or may be transmitted using the communication network CN.

Fig. 2 is a diagram schematically showing a relationship between the particles 91, the parallel light 10, and the optical axis 11 of the microscope 4.

When the parallel light 10 from the light source 2 enters the sample 9, the parallel light 10 often passes through and transmits between the particles 91 as shown as parallel light 10(1) in fig. 2. The remaining collimated light 10 is incident on the particle 91 and scattered as illustrated as collimated light 10(2) and (3).

Some of the collimated light 10(2) and (3) scattered by the particles 91 are scattered at an angle θ 1 of a predetermined angle θ th or less with respect to the optical axis 11 of the microscope 4(θ 1 ≦ θ), and enter the microscope 4 and reach the imaging unit 5. The other part of the parallel light 10(3) is scattered at an angle θ 2 exceeding a prescribed angle θ th (θ 2 > θ). The light 10(3) scattered at an angle larger than the predetermined angle θ th is blocked by the light blocking plate 6 and does not enter the microscope 4.

The light shielding plate 6 will be described with reference to fig. 3. The light shielding plate 6 is disposed between the sample 9 and the microscope 4. The light shielding plate 6 causes only scattered light (scattered light having a predetermined angle θ th or less) within a predetermined angle range among scattered light generated by the particles 91 to enter the microscope 4.

Fig. 3 shows an example of the light shielding plate 6 as viewed from the optical axis 11 of the diaphragm. The light shielding plate 6(1) of fig. 3 (1) has an opening 61(1) centered on the optical axis 11 and is formed in an annular shape as a whole. By using the light shielding plate 6(1), it is possible to reduce the incidence of unnecessary light to the incidence part (aperture) of the microscope 4. Here, the unnecessary light is light other than light that can be used for measuring the size of the particle, that is, light other than scattered light that is scattered at a predetermined angle θ th or less.

The light shielding plate 6(2) of fig. 3 (2) is formed in a substantially U shape with one side (upper side in fig. 3) opening near the collimated light 10. Of the scattered light, scattered light close to the optical axis of the parallel light 10 is incident on the microscope 4 through the opening 61 (2). Otherwise, the scattered light is not originally incident on the microscope 4, or is blocked by the light blocking plate 6 (2). Even when the light shielding plate 6(2) is used, it is possible to reduce the incidence of unnecessary light into the microscope 4.

An example of the beam shape (beam profile) of the collimated light 10 will be described with reference to fig. 4. Fig. 4 shows a field of view 41 of the microscope 4 and a linear travel component incident range 51, which is a region where a linear travel component of the parallel light 10 enters the imaging unit 5 in the beam cross section.

Fig. 4(1) shows an example of a circular beam. In the case of a circular beam, the cross-sectional size of the parallel light 10 is large, and therefore, when the center 101 of the parallel light 10 is aligned with the visual field range 41, the parallel light overlaps with the linear travel component incident range 51. In contrast, the optical system is set such that the visual field range 41 is located at a position shifted from the cross-sectional center 101 of the parallel light 10. In this case, the optical system of the light source 2 may be designed in combination with a diffuser, a lens, or the like so that the optical density of the parallel light 10 is uniform in the visual field range 41.

Fig. 4(2) shows an example of a substantially semicircular beam. In this example, by cutting a part of the cross section of the collimated light 10 using a shielding plate or the like, not shown, the beam cross section of the collimated light 10 does not overlap the linear travel component incident range 51. In the example shown in fig. 4(2), the visual field range 41 can be made closer to the cross-sectional center 101 of the parallel light 10 than in the case of fig. 4 (1). Therefore, even when the optical density of the collimated light 10 has a centrosymmetric distribution such as a gaussian distribution, the vicinity of the center where the optical density is relatively uniform can be made to coincide with the visual field range 41.

Fig. 4 (3) shows an example of a substantially rectangular light flux. In this example, shaping is performed using a mask or the like, not shown, so that the cross section of the collimated light 10 is slightly wider than the visual field range 41. This can prevent the scattered light from the particles 91 outside the visual field range 41 from entering the microscope 4 by multiple scattering, and can capture the scattered light from the particles 91 within the visual field range 41 at a high S/N ratio.

The measurement unit 3 will be described with reference to the cross-sectional view of fig. 5. The measurement unit 3 holds a sample 9 therein, and irradiates the held sample 9 with parallel light 10. The measurement unit 3 includes, for example, a sample container 31, an observation window 33, an irradiation window 34, and an irradiation window driving unit 35.

The sample container 31 is a container for holding the sample 9. The sample container 31 may be installed at a place remote from a manufacturing line (not shown) and the sample 9 taken out from the manufacturing line may be injected into the space 32 of the sample container 31, or the sample container 31 may be installed in the middle of the manufacturing line and the sample 9 may be directly sent from the manufacturing line into the space 32 of the container 31.

The observation window 33 is a window for observing the sample 9 through the microscope 4. The viewing window 33 is transparent at least with respect to the wavelength of the parallel light 10. The optical system is set so that the focal point of the microscope 4 is located near the surface of the observation window 33 on the sample side.

The irradiation window 34 is a window for irradiating the sample container 31 with the parallel light 10. The irradiation window 34 is provided in the sample container 31 so as to face the observation window 12. The illumination window 34 is transparent at least with respect to the wavelength of the parallel light 10. A minute gap 321 is formed between the observation window 33 and the irradiation window 34, and a part of the sample 9 is held in the gap 321.

The irradiation window driving unit 35 controls the position of the irradiation window 34. The irradiation window 34 is moved closer to the observation window 33 or farther from the observation window 33 by the irradiation window driving unit 35. The irradiation window driving unit 35 may be operated in accordance with a control signal from the control unit 8, or may be manually operated by the user.

If necessary, the sample 9 is diluted and dispersed so that the particles do not overlap each other when the sample 9 in the sample container 31 is imaged by the microscope 4.

The parallel light 10 enters from the irradiation window 34 and is irradiated to the sample 9. The component of the parallel light 10 that travels straight without being scattered by the particles in the sample 9 passes through the observation window 33 and reaches the outside of the measurement unit 3. The microscope 4 images, through the observation window 33, components of the parallel light 10 scattered in the direction of the optical axis 11 of the microscope by the particles of the sample 9.

Here, it is desirable to set the observation window 33 to a sufficient size so that all of the straight-line traveling components of the parallel light 10 can be transmitted. When a part of the linear component of the parallel light 10 comes into contact with the sample container 31, it is reflected and scattered inside the sample container 31, and a part of it enters the microscope 4 to deteriorate the S/N ratio during imaging.

In the present embodiment, an example in which the straight-line component of the parallel light 10 is transmitted through the observation window 33 and reaches the outside of the measurement unit 3 is described. Instead, the inner wall of the sample container 31 may be coated with a light absorbing agent, or a light absorbing member may be provided inside the sample container 31. This can suppress the irregular reflection of light in the sample container 31.

As described above, the irradiation window driving unit 35 moves the irradiation window 34 in the direction of the optical axis 11 of the microscope 4. In the measurement, by bringing the irradiation window 34 closer to the observation window 33, the thickness of the sample 9 in the direction of the optical axis 11 can be reduced, and the region (volume) of the sample 9 to which the parallel light 10 is irradiated can be minimized. This can suppress the overlapping of the particles when the sample 9 is imaged by the microscope 4, and can suppress the influence of scattered light generated by the particles outside the focal position of the microscope 4. Further, since the movement of the particles is suppressed by bringing the irradiation window 34 and the observation window 33 as close as possible, the blur at the time of imaging can be suppressed.

After the imaging by the microscope 4 is completed, the irradiation window 34 is separated from the observation window 33 by the irradiation window driving unit 35. After the irradiation window 34 and the observation window 33 are separated, the sample 9 in the sample container 31 can be replaced.

The optical system of the microscope 4 shown in fig. 1 is designed such that the focal point on the object side is aligned with the sample 9, and the scattered light from one particle can be imaged by the imaging unit 5 of the microscope 4. In the microscope 4 of the present embodiment, the focal length and the lens diameter are set so as to suppress the incidence of the rectilinear propagation component of the parallel light 10 on the imaging unit 5.

Fig. 6 shows an example of an image obtained by imaging alumina particles. Fig. 6(1) shows a scattered light image, and fig. 6(2) is an explanatory view schematically showing the scattered light image. The schematic diagram of fig. 6(2) is for explaining a scattered light image, and does not directly correspond to the image of fig. 6 (1).

The points in fig. 6 show the scattered light from one particle. In the present embodiment, in order to capture a component of the scattered light that is substantially parallel to the optical axis 11 (a component whose angle with respect to the optical axis 11 is equal to or smaller than the predetermined angle θ th), the microscope 4 is set so that the focal length with respect to the lens diameter is as long as possible.

The image processing unit 7 shown in fig. 1 recognizes one particle 91 from the image captured by the imaging unit 5, acquires the intensity of scattered light in each particle, and calculates the particle size based on the high intensity of the scattered light.

The image processing unit 7 acquires, as the scattered light intensity of each particle, the value of the pixel having the highest luminance value in the pixel group corresponding to the particle. Alternatively, the image processing unit 7 may be adapted to fit the curve by gaussian distribution or the like, and thereby set the peak intensity of the obtained curve as the scattered light intensity.

The image processing unit 7 prepares a correspondence between the scattered light intensity of the material of the sample 9 and the particle size in advance in the form of a relational expression or a database, and calculates the particle size by using the relational expression or the database.

When the scattered light intensity deviates from the luminance range of the captured image, the output of the light source 2 may be adjusted, the exposure time of the imaging unit 5 may be adjusted, or the gain of the imaging unit 5 may be adjusted. Thereby, the scattered light intensity is brought within the range of the luminance range. In a fourth embodiment described later, the output of the second light source 18 can be adjusted in accordance with the characteristics of the sample 9.

When the scattered light intensity is greatly different for each particle and the scattered light intensity of all the particles cannot fall within the luminance range of the captured image, for example, the output of the light source 2 and the exposure time or gain of the imaging unit 5 are changed to perform multiple times of imaging.

The reason why the particle size can be calculated by identifying small particles of 1 μm or less in this example will be described. The scattered light intensity of the light scattered by the particles can be calculated according to Mie scattering theory. Fig. 7 shows the results obtained by calculating the intensity of scattered light for the alumina particles.

In the characteristic diagram of fig. 7, the horizontal axis shows the scattering angle. The vertical axis of FIG. 7 shows calculated values of scattered light intensity in several particle sizes (e.g., 10 μm, 0.8 μm, 0, 6 μm, 0.4 μm, 0.3 μm, 0.2 μm, 0.1 μm).

The scattered light intensity shows a complicated behavior with respect to the scattering angle by light interference within the particle or the like. However, when the eye is focused on a range in which the scattering angle is equal to or smaller than the predetermined angle θ th, the scattered light intensity is known to increase monotonously with respect to the increase in particle size. In contrast, in the present example, the particle size is uniquely calculated from the scattered light intensity in a small-angle scattering range (range of the predetermined angle θ th or less) that changes monotonously with respect to the particle size, using the relationship shown in fig. 7.

According to the present embodiment configured as described above, in the particle 91, the size and the position of the particle 91 can be measured based on the intensity of scattered light scattered at a predetermined angle θ th or less from the optical axis of the parallel light 10. Therefore, it is possible to measure small-sized particles, compared to the conventional technique in which shadow images of the particles 91 are measured by an optical system of a transmission system.

In this embodiment, an example of an optical system in which the linear traveling component of the parallel light 10 is not incident on the imaging unit 5 is described, but instead, a polarization filter may be provided between the sample 9 and the imaging unit 5, and a polarization light source may be used as the light source 2. As the polarized light source, for example, there are a laser light source having polarization, a combination of a polarization filter and the light source 2, and the like. By combining the polarized light source and the polarized filter, the linear traveling component of the parallel light 10 can be prevented from entering the imaging unit 5.

[ example 2]

A second embodiment will be described with reference to fig. 8 to 10. In the following embodiments, differences from the first embodiment will be mainly described. In this embodiment, the range of the particle size that can be measured is expanded by measuring the particle size based on the particle shape image in addition to the measurement of the particle size based on the scattered light intensity.

Fig. 8 shows a structure of a particle size distribution measuring apparatus 1A in the present embodiment. The particle size distribution measuring apparatus 1A is added with a particle shape imaging light source 12 and a light source switching unit 13, compared with the particle size distribution measuring apparatus 1 shown in fig. 1. The image processing unit 7A of the particle size distribution measuring apparatus 1A measures the particle size based on the plurality of measurement algorithms 71 and 72.

The particle shape imaging light source 12 as an example of the "second light source" irradiates the specimen 9 held by the measurement unit 3 with the parallel light 14. The optical axis of the parallel light 14 is set to substantially coincide with the optical axis 11 of the microscope 4.

The light source switching unit 13 switches the light source 2 and the light source 12 in accordance with a control signal (switching signal) from the control unit 8. The light source switching unit 13 irradiates the sample 9 with the parallel light 10 or the parallel light 14 by alternately using the light source 2 and the particle shape imaging light source 12.

When the sample 9 is irradiated with the collimated light 10 from the light source 2, a scattered light image scattered at a predetermined angle θ th or less in the particles is captured by the imaging unit 5, as in the first embodiment. Then, the particle size measurement processing unit 71 of the image processing unit 7 based on the scattered light high intensity recognizes one particle from the scattered light image captured by the imaging unit 5, and calculates the particle size from the scattered light intensity.

On the other hand, when the specimen is irradiated with the collimated light 14 from the particle shape imaging light source 12, the shadow image of the particle is captured by the imaging unit 5. The particle size measurement processing unit 72 of the image processing unit 7 based on the particle shape image recognizes one particle from the shadow image of the particles 91 generated by the parallel light 14, and calculates the particle size from the size of the shadow image.

The particle size distribution measurement process will be described with reference to the flowchart of fig. 9. The particle size distribution measuring apparatus 1A (hereinafter, sometimes abbreviated as the measuring apparatus 1A) irradiates the sample 9 with the collimated light 10 from the light source 2 (S11), and acquires a scattered light image scattered at a predetermined angle θ th or less from the imaging unit 5 (S12).

The measurement device 1A recognizes each particle from the scattered light image, and calculates a position for each recognized particle i (step (c)) (x_1i，y_1i) And dimension D_1i(S13)。

Next, the measurement device 1A switches from the light source 2 to the particle shape imaging light source 12, and irradiates the sample 9 with the collimated light 14 from the particle shape imaging light source 12 (S14), thereby acquiring a shadow image of the particle from the imaging unit 5 (S15). The measurement device 1A recognizes each particle from the particle shape image, and calculates a position (x) for each recognized particle j_2j，y_2j) And dimension D_2j(S16)。

The measurement device 1A compares the positions of the particles i obtained from the scattered light image with the positions of the particles j obtained from the shadow image, and determines whether or not the particles are the same (S17). That is, the particle size distribution measuring apparatus 1A determines whether or not there are particles i and particles j whose positions coincide with each other.

When the measuring apparatus 1A detects the same particle (S17: YES), it determines that the size D of the particle j determined to be the same_2jWhether or not it is larger than a predetermined threshold Dth (S18).

As a result of the comparison, the particle size D of the shadow image of the apparatus 1A was measured_2jIf it is larger than the threshold Dth (S18: YES), the size of the particle detected in step S17 is judged to be "D_2j"(S19). Otherwise (S18: NO), the measurement device 1A determines that the size of the particle detected in step S17 is "D_1i”(S20)。

The measurement device 1A repeats steps S17 to S20 for all the particles i recognized from the scattered light image (S21). When the particle sizes are determined for all the particles i (S21: YES), the process is ended.

The reason why the range of the measurable particle size can be expanded in the present embodiment will be described. As shown in fig. 7, the scattered light intensity monotonically increases with an increase in particle size at or below a predetermined scattering angle θ th. However, when the particle size is further increased, the scattered light intensity shows a maximum and starts to decrease.

Fig. 10 shows the particle size versus the scattered light intensity in a scattering angle of 10 ° for alumina particles. The scattered light intensity increases until the particle size becomes "1.2 μm", but when the particle size becomes larger, the scattered light intensity decreases. In this case, a plurality of particle sizes correspond to one scattered light intensity, and therefore, the particle sizes cannot be uniquely determined. In the example of fig. 10, the scattered light intensity when the particle size is "1.0 μm" is substantially equal to the scattered light intensity when the particle size is "1.4 μm", and therefore the particle size cannot be determined only by the scattered light intensity.

On the other hand, when the particle size exceeds "1.0 μm", the particles can be recognized by the shadow image generated by the light source 12 for particle shape imaging. In contrast, in the present embodiment, as described with reference to fig. 10, the range of the measurable particle size is expanded by setting the threshold Dth of the particle size and using the particle size obtained from the scattered light image and the particle size obtained from the shadow image separately.

The threshold Dth is set in a plurality of ways. One of them is a method of setting a limit value that allows the size of particles to be recognized from a shadow image as a reference. Another method is to set the particle size, which cannot uniquely determine the scattered light intensity, as a reference when the scattered light intensity characteristics of the measurement target can be predicted in advance.

The present embodiment thus configured provides the same operational advantages as the first embodiment. In the present embodiment, the light source 2 and the particle shape imaging light source 12 are alternately used, and the sample 9 is irradiated with parallel light to obtain a scattered light image and a particle shape image, and the particle size is determined by comparing these images, so that the measurable particle size can be further expanded as compared with the first embodiment, and the usability can be improved.

The imaging unit 5 may be configured to detect light in a wavelength range by making the wavelength of the light source 2 different from the wavelength of the particle shape imaging light source 12. The imaging unit 5 may be configured to acquire images corresponding to the wavelength of the parallel light from the light source 2 and the wavelength of the parallel light from the particle shape imaging light source 12, for example, by a color CCD or a structure for detecting light in a wavelength range. In this case, the scattered light image and the shadow image generated by the particles can be acquired continuously or simultaneously without switching the light source, and the measurement can be performed at high speed.

[ example 3]

A third embodiment will be described with reference to fig. 11. In this example, an example in which the measurement time is shortened as compared with the particle size distribution measuring apparatus 1A described in the second example will be described.

Fig. 11 shows a structure of a particle size distribution measuring apparatus 1B of the present example. The particle size distribution measuring apparatus 1B includes a plurality of microscopes 4(1) and 4(2) as compared with the measuring apparatus 1 shown in fig. 1. The relationship of the light source 2 to the microscope 4 shown in fig. 1 corresponds to the relationship of the light source 15 to the first microscope 4(1) shown in fig. 11.

That is, the first microscope 4(1) images scattered light scattered at a predetermined angle θ th or less in the particles, and obtains a scattered light image, as in the microscope 4 described in the first embodiment. The second microscope 4(2) takes a shadow image of the particles.

Here, the optical axis 11 of the first microscope 4(1) is shifted by a predetermined angle θ th with respect to the optical axis of the parallel light 16 from the light source 15. The optical axis 17 of the second microscope 4(2) substantially coincides with the optical axis of the parallel light 16 from the light source 15. In addition, the focal position of the first microscope 4(1) substantially coincides with the focal position of the second microscope 4 (2).

In the first microscope 4(1), the optical system is designed so that scattered light from one particle can be imaged by the imaging unit 5 (1). In the first microscope 4(1), the focal length and the lens diameter are set so that the straight-line component of the parallel light 16 does not enter the imaging unit 5 (1). In order to capture the component parallel to the optical axis 11 in the scattered light, it is desirable to design the focal length as long as possible with respect to the lens diameter in the first microscope 4 (1).

As described above, the second microscope 4(2) and the light source 15 are arranged facing each other with the measurement unit 3 interposed therebetween, and the optical axis of the light source 15 substantially coincides with the optical axis 17 of the second microscope 4 (2). In this way, in the second microscope 4(2), the imaging unit 5(2) captures a shadow image of the particles.

The image processing unit 7B calculates the size of the particles based on the scattered light image acquired from the first microscope 4(1) and the particle shape image acquired from the second microscope 4 (2). The method of calculating the particle size is as described in fig. 9, and therefore, the description thereof is omitted here.

In this way, in the present embodiment, the parallel light 16 is irradiated from the light source 15, the scattered light image is captured by the first microscope 4(1), and the shadow image is captured by the second microscope 4 (2). The imaging by the first microscope 4(1) and the imaging by the second microscope 4(2) may be performed continuously or simultaneously.

The present embodiment has the same operational effects as the first and second embodiments. In addition, in the present embodiment, as in the second embodiment, since the light source 15 can be continuously used without switching the light sources 2 and 12, the scattered light image and the particle shape image can be acquired at a higher speed, and the measurement time can be shortened. As a result, the performance and usability of the measurement device 1B are improved.

[ example 4]

A fourth embodiment will be described with reference to fig. 12 to 15. In the present example, the range of application to the material is expanded as compared with the particle size distribution measuring apparatus 1 described in the first example.

Fig. 12 shows a structure of a particle size distribution measuring apparatus 1C in the present embodiment. The particle size distribution measuring apparatus 1C includes a third light source 18, a wavelength selective mirror 19, and a mirror 20, as compared with the particle size distribution measuring apparatus 1 shown in fig. 1. The image processing unit 7C of the particle size distribution measuring apparatus 1C measures the particle size based on the plurality of measurement algorithms 71 and 72.

The output wavelength of the third light source 18 is different from the output wavelength of the light source 2, and the parallel light 21 is irradiated toward the sample 9 held by the measurement unit 3 via the wavelength selective mirror 19 and the mirror 20. The optical axis of the parallel light 21 is set to substantially coincide with the optical axis 10 of the light source 2.

The wavelength selective mirror 19 is designed to transmit light from the light source 2 and reflect light from the third light source 18.

The imaging unit 5C splits the incident light into a plurality of wavelength bands, and captures images corresponding to the respective wavelength bands. As the imaging unit 5C, for example, a color CCD (Charge Coupled Device) that splits RGB can be used.

In the present embodiment, the wavelength of the light source 2 and the wavelength of the third light source 18 are made to correspond to the respective spectral wavelength bands of the imaging unit 5C, and the imaging unit 5C captures scattered light images in which parallel light from the respective light sources is scattered by the sample 9. For example, when the imaging unit 5C is a color CCD that is RGB in spectral, the output wavelength of the light source 2 is red, the scattered light based on the red light is captured in the R pixel of the imaging unit 5C, the output wavelength of the third light source 18 is blue, and the scattered light based on the blue light is captured in the B pixel of the imaging unit 5C.

The particle size distribution measurement process will be described with reference to the flowchart of fig. 13. First, the particle size distribution measuring apparatus 1C sets the output values of the light source 2 and the third light source 18 to the same levels of the respective scattered light intensities (S21). The output value setting method includes setting by manual input and automatically calculating based on a predicted value of the scattered light intensity prepared in advance in the form of a relational expression or a database.

Next, parallel light beams 10 and 21 are irradiated from the light source 2 and the third light source 18 to the sample 9 (S22), and a scattered light image (color image) scattered at a predetermined angle θ th or less is acquired from the imaging unit 5C (S23).

The particle size distribution measuring apparatus 1C extracts a monochrome image captured by the R pixel and a monochrome image captured by the B pixel from the captured color image. The image processing unit 7C recognizes each particle from each extracted monochrome image, and acquires, as the scattered light intensity I of the particle, the value of the pixel having the highest luminance value in the pixel group corresponding to each particle, for each recognized particle I_R，i、I_B，i(S24, S25). Alternatively, the image processing unit 7C may fit the curve by gaussian distribution or the like, and thereby may use the peak intensity of the obtained curve as the scattered light intensity.

Next, the image processing unit 7C obtains the scattered light intensity I from each monochrome image_R，i、I_B，iThe spectral characteristics of the CCD are corrected,calculating true scattered light intensity I_0R，i、I_0B，i(S26). For example, in a typical color CCD, light is split using a color filter, but light outside a predetermined wavelength band is slightly transmitted instead of being cut off at a rate of 100%. Therefore, for example, when the intensity of scattered light corresponding to light from the light source 2 is high, light is detected also in the B pixel of the imaging unit 5C. Thus, the intensity of the scattered light I obtained_B，iThe sum of the scattered light corresponding to the light from the third light source 18 and the component of the scattered light corresponding to the light from the light source 2 that is not cut by the filter is obtained. In this case, the true scattered light intensity corresponding to each light source is represented by I_0R，i、I_0B，iThe intensity of scattered light I acquired from the image_R，i、I_B，iThe following formulas 1 and 2.

I_R，i＝I_0R，i+a×I_0B，iA 1. formula

I_B，i＝I_0B，i+b×I_0R，iA. formula 2

Here, "a" is a value obtained by dividing the light intensity acquired in the R pixel when only the third light source 18 is irradiated by the light intensity acquired in the B pixel. "B" is a value obtained by dividing the light intensity acquired in the B pixel by the light intensity acquired in the R pixel when only the light source 2 is irradiated. These a-and b-values are obtained by measurement using a standard sample or the like in advance. The true scattered light intensity corresponding to each light source is obtained by solving the above equations 1 and 2.

Next, the particle size distribution measuring apparatus 1C prepares in advance a correspondence relationship between the scattered light intensity of the material of the sample 9 and the particle size at the wavelength of each light source in the form of a relational expression or a database, and calculates the particle size from the true scattered light intensity corresponding to each light source calculated as described above (S27). For example, when the scattered light intensity in each particle size (d) prepared in advance is I_R(d)、I_B(d)Then, d is calculated so that the value of the following equation 3 becomes the minimum, and it is determined that the calculated value of d is the particle size.

(I_0R，I-I_R(d))²+(I_0B，I-I_B(d))²A formula 3

The reason why the range of application to the material can be expanded in the present embodiment is explained. In the case of the alumina shown in fig. 10, the scattered light intensity monotonically increases with an increase in particle size until the particle size becomes 1.2 μm. However, when a material having a higher refractive index is used, the upper limit of the particle size at which the scattered light intensity monotonically increases becomes lower.

Fig. 14 (1) shows the relationship between the particle size and the scattered light intensity at a scattering angle of 10 ° when 635nm (red) light is irradiated to the barium titanate particles. The scattered light intensity increases until the particle size becomes "0.5 μm", but when the particle size becomes larger, the scattered light intensity decreases. In this case, a plurality of particle sizes correspond to one scattered light intensity, and therefore, the particle sizes cannot be uniquely determined. In the example of (1) in fig. 14, the particle size cannot be determined in the range of 0.5 μm to 0.8 μm.

On the other hand, fig. 14 (2) shows the relationship between the particle size when the barium titanate particles are irradiated with 455nm (blue) light and the intensity of scattered light at a scattering angle of 10 °. When compared with (1) of fig. 14, the curve shape of the scattered light intensity with respect to the particle size is different in (2) of fig. 14. In (1) of fig. 14, in the range of 0.5 μm to 0.8 μm showing the decreasing tendency of the scattered light intensity, in (2) of fig. 14, the scattered light intensity monotonically increases. Therefore, the particle size can be determined by using the scattered light intensity corresponding to the light source of 455 nm.

In the present embodiment, the example in which the optical axis of the parallel light 10 from the light source 2 and the optical axis of the parallel light 21 from the third light source 18 are aligned and irradiated to the sample 9 has been described, but as in the modification shown in fig. 15, the optical axes 10 and 21 of the respective light sources may be arranged side by side on a plane forming an angle θ th with the optical axis 11. The angle formed by the optical axis 10 and the optical axis 11 and the angle formed by the optical axis 21 and the optical axis 11 may be different from each other as long as the scattered light intensity and the particle size can be associated with each other.

In the present embodiment, the example in which the light source 2 and the third light source 18 are irradiated simultaneously has been described, but the irradiation may be performed alternately in time, and the corresponding scattered light images may be acquired to calculate the particle size.

The present invention is not limited to the above embodiments. Those skilled in the art can make various additions, modifications, and the like within the scope of the present invention. The above embodiments are not limited to the configuration examples illustrated in the drawings. The configuration and the processing method of the embodiment can be appropriately modified within the scope of achieving the object of the present invention.

In addition, each component of the present invention can be arbitrarily selected, and an invention having a configuration in which the selection is made is also included in the present invention. The configurations described in the claims may be combined with each other in addition to the combinations explicitly described in the claims.