JP5681517B2 - Particle conductivity discrimination apparatus and particle conductivity discrimination method - Google Patents

Description

  The present invention relates to a particle conductivity determining apparatus and a particle conductivity determining method, and more particularly to an apparatus for determining whether a particle has conductivity using an optical method and a method for determining the same.

  In recent years, there have been accidents in which lithium-ion batteries for notebook computers ignite. This is because, in the battery manufacturing process, conductive particles such as metal particles are mixed inside the battery cell, and the mixed conductive particles penetrate the separator separating the positive electrode and the negative electrode to cause an internal short circuit. It is thought to lead to an accident.

  Therefore, in order to prevent the conductive particles from entering the battery cell, a technique for monitoring the conductive particles in the manufacturing process is desired.

  In general, a light scattering type particle counter is often used as a method for measuring floating particles. In this method, the aerosol to be measured is irradiated to the aerosol to be measured, the scattered light from the particles present in the aerosol is detected, and the number of particles and the particle size are obtained (see Patent Document 1 below).

JP-A-62-108386

  However, although the number of suspended particles and the particle diameter can be obtained by the above method, it has not been possible to determine whether or not the particles have conductivity.

  Accordingly, an object of the present invention is to provide a method and apparatus for determining whether particles floating in a space have electrical conductivity.

The present invention that has solved the above problems is as follows.
<Invention of Claim 1>
A method for determining whether particles suspended in space have electrical conductivity,
Irradiate the floating particles to be discriminated with laser light emitted from a laser light generator,
In the floating particles having a particle size parameter α (α = πd / λ, where d: particle size, λ: wavelength of laser light) is 20 or more,
Forward scattered light and back scattered light generated by the irradiation are detected by a forward scattered light detector and a back scattered light detector,
At least one of the forward scattered light intensities within a range of 30 ° to 60 ° and a range of 300 ° to 330 ° of a particle scattering angle with respect to an incident line of laser light;
Determining the presence or absence of conductivity of the suspended particles based on the ratio of at least one of the backscattered light intensity within a range of 120 to 150 degrees and within a range of 210 to 240 degrees;
A method for determining particle conductivity.

(Function and effect)
The present inventor irradiates floating particles to be discriminated with laser light, detects forward scattered light and back scattered light generated by the irradiation with a forward scattered light detector and a back scattered light detector, and detects the intensity of the forward scattered light. It was found that the presence or absence of conductivity of the suspended particles can be determined based on the ratio of the intensity of the backscattered light and the backscattered light. As a result, it is not necessary to prepare a special device, the device configuration is simple, and discrimination can be performed with high accuracy.
Within the above scattering angle range, the intensity ratio of scattered light can be clearly understood, and the presence or absence of conductivity of particles can be determined with high accuracy.

<Invention of Claim 2>
The laser beam generator is a device that generates a laser beam,
The forward scattered light detector is a photodiode or a photomultiplier;
The particle conductivity determination method according to claim 1, wherein the backscattered light detector is a photodiode or a photomultiplier tube.

(Function and effect)
This is effective when capturing individual particles.

<Invention of Claim 3>
The particle conductivity determination method according to claim 1, wherein the laser light generation device is a device that generates a laser light sheet, and the forward scattered light detector and the back scattered light detector are imaging elements.

(Function and effect)
This is effective for capturing particles as a group, and for grasping the dispersion distribution.

<Invention of Claim 4>
The particle conductivity determination method according to any one of claims 1 to 3, wherein a polarization filter is provided on a front surface of the forward scattered light detector and the back scattered light detector to detect polarized light parallel to the observation surface.

(Function and effect)
Compared with the case where polarized light perpendicular to the observation surface is detected, the intensity ratio of scattered light can be clearly understood, and the presence or absence of conductivity of particles can be determined with high accuracy.

<Invention of Claim 5>
The at least one selected from a polarizing filter or a polarizing prism and a λ / 2 wavelength plate is provided on the front surface of the laser light generator, and the polarized light parallel to the observation surface is irradiated. The particle | grain conductivity discrimination method of 1-4.

(Function and effect)
Compared with the case of irradiating polarized light perpendicular to the observation surface, the intensity ratio of scattered light can be clearly understood, and the presence or absence of conductivity of particles can be determined with high accuracy.

<Invention of Claim 6>
A light receiving angle adjusting device is provided in front of the forward scattered light detector and the back scattered light detector, and at least one of the forward scattered light having a particle scattering angle of 40 to 50 degrees and 310 to 320 degrees with respect to the incident line of the laser light. And at least one of the backscattered light of 130 to 140 degrees and 220 to 230 degrees is detected.

(Function and effect)
As compared with the case of the invention of claim 1, the intensity ratio of scattered light can be clearly understood, and the presence or absence of conductivity of particles can be determined with high accuracy.

<Invention of Claim 7>
The particle conductivity determination method according to any one of claims 1 to 6, wherein an interference filter is provided in front of the forward scattered light detector and the back scattered light detector.

(Function and effect)
Since inelastically scattered light such as fluorescence can be removed, it is easier to determine the presence or absence of electrical conductivity of the particles than when no interference filter is provided.

<Invention of Claim 8>
An apparatus for determining whether particles floating in space have electrical conductivity,
A laser beam generator for irradiating the floating particles to be discriminated with a laser beam;
In the floating particles having a particle size parameter α (α = πd / λ, where d: particle size, λ: wavelength of laser light) is 20 or more,
A forward scattered light detector and a back scattered light detector for detecting forward scattered light and backward scattered light generated by the irradiation;
The intensity of at least one of the forward scattered light within a range of a particle scattering angle of 30 to 60 degrees and a range of 300 to 330 degrees with respect to an incident line of laser light;
Means for determining the presence or absence of conductivity of the suspended particles based on the ratio of the intensity of the backscattered light in at least one of the range of 120 to 150 degrees and the range of 210 to 240 degrees;
A particle conductivity discriminating apparatus characterized by comprising:

(Function and effect)
The same effects as in the case of claim 1 are achieved.

  According to the particle conductivity determining apparatus and the particle conductivity determining method of the present invention, it is possible to determine whether or not floating particles have conductivity.

It is a top view of the particle conductivity discriminating device concerning the present invention. It is a modification of the particle | grain electrical conductivity determination apparatus which concerns on this invention. It is the figure which showed the scattered light at the time of irradiating light to the floating particle which does not have electroconductivity. It is the figure which showed the scattered light at the time of irradiating light to the floating particle | grains which have electroconductivity. It is the figure which showed the scattered light at the time of irradiating light to the floating particle | grains which have electroconductivity. It is a figure showing about intensity ratio of forward scattered light intensity and back scattered light intensity. It is a figure showing the experimental result in case airborne particles are glass beads. It is a figure showing the experimental result in case airborne particles are Ni. It is a figure at the time of using a laser light sheet as irradiation light, and using an image pick-up element as a scattered light detector. It is a figure showing about another example about intensity ratio of forward scattered light intensity and back scattered light intensity. It is a figure showing about another example about intensity ratio of forward scattered light intensity and back scattered light intensity.

  Hereinafter, a preferred embodiment of a particle conductivity determination device and a particle conductivity determination method of the present invention will be described with reference to FIGS.

  FIG. 1 is a plan view of a particle conductivity discriminating apparatus according to the present invention.

The particle conductivity discriminating apparatus includes a laser light generator 1, a forward scattered light detector 3, and a backscattered light detector 4.
When laser light is irradiated from the laser light generator 1 to the target floating particles 2, the laser light hits the floating particles 2 and the light is scattered.
The forward scattered light detector 3 and the back scattered light detector 4 detect how this light scattering occurs on the observation surface L. More specifically, the forward scattered light detector 3 detects the scattered light scattered forward. What is scattered backward is detected by the backscattered light detector 4.
Then, the presence or absence of conductivity of the suspended particles is determined based on the ratio of the intensity of the forward scattered light and the intensity of the back scattered light.

Here, the observation surface L is (1) a straight line connecting the emission port of the laser beam generator 1 and the suspended particles 2, (2) a straight line connecting the light receiving port of the forward scattered light detector 3 and the suspended particles 2, (3) A surface including all of the light receiving port of the backscattered light detector 4 and the straight line connecting the suspended particles 2.
A straight line connecting the laser beam exit of the laser beam generator 1 and the suspended particle 2 and its extension line are referred to as a longitudinal reference line Y. A line passing through the suspended particles 2 and intersecting the vertical reference line Y at a right angle is referred to as a horizontal reference line X. Further, with the horizontal reference line X as a boundary, the Y plus direction is referred to as the front, and the Y minus direction is referred to as the rear. The vertical reference line Y and the horizontal reference line X are on the observation plane L.
Further, the angle formed between the direction line connecting the suspended particle 2 and the forward scattered light detector 3 and the direction line connecting the back scattered light detector 4 with the longitudinal reference line Y is defined as the forward scattering angle θ1 and the back scattering angle. Let θ2.
The forward scattered light detector includes a photodiode or a photomultiplier tube, and the photodiode includes an avalanche photodiode. Similarly, the backscattered light detector includes a photodiode or a photomultiplier tube, and the photodiode includes an avalanche photodiode.
Although FIG. 1 shows an example in which the forward scattered light detector 3 and the back scattered light detector 4 are provided in the X plus direction, the present invention is not limited to this example. Specifically, the forward scattered light detector 3 and the back scattered light detector 4 may be provided in the X minus direction, or a plurality of the forward scattered light detector 3 and the back scattered light detector 4 may be provided.

  FIG. 2 is a modification of the particle conductivity determination device according to the present invention.

A polarizing filter 5 is provided in front of at least one of the forward scattered light detector 3 and the back scattered light detector 4. By providing the polarizing filter 5, only polarized light perpendicular to the observation plane L or only polarized light parallel to the observation plane L can be detected.
In the particle conductivity determination method according to the present invention, as described later, when polarized light parallel to the observation surface L is used, it becomes easy to determine whether the particles are conductive. It is preferable to use a polarizing filter 5 that detects only polarized light.
However, the present invention is not limited to this, and a polarizing filter 5 that detects only polarized light perpendicular to the observation plane L may be used.
Furthermore, in the particle conductivity determination method of the present invention, as described later, forward scattered light having a forward scattering angle θ1 within a specific range and backscattered light having a backscattering angle θ2 within a specific range are used. Since the presence / absence of conductivity of the particles can be determined with high accuracy, the light is received on the front surface of at least one of the forward scattered light detector 3 and the back scattered light detector 4 so as to detect scattered light in the range. An angle adjusting device 7 is provided. An example of the light receiving angle adjusting device 7 is an iris.
In addition, an interference filter 8 for removing inelastic scattered light such as fluorescence may be provided in front of at least one of the forward scattered light detector 3 and the back scattered light detector 4.
In the present invention, all of the polarizing filter 5, the light receiving angle adjusting device 7, and the interference filter 8 may be provided, or any one of them may be selected and provided.
Further, a collimating lens 9 may be provided in front of at least one of the forward scattered light detector 3 and the back scattered light detector 4.
Further, a condensing lens 10 may be provided in front of at least one of the forward scattered light detector 3 and the back scattered light detector 4 to collect light.
An example of the arrangement of the polarizing filter 5, the light reception angle adjusting device 7, the interference filter 8, the collimating lens 9, and the condensing lens 10 will be described in detail in the description of the experiment described later.

On the other hand, the laser beam emitted from the laser beam generator 1 is preferably in a polarized state.
However, there are laser beams emitted from some laser beam generators 1 including various polarization components and undesirable ones having a polarization ratio of about 50: 1. Therefore, in order to convert such laser light into laser light having a desired polarization ratio, it is preferable to use a polarizing filter 5 on the front surface of the laser light generator as shown in FIG. Although not shown in FIG. 2, a polarizing prism may be used instead of the polarizing filter 5. Here, the desirable polarization ratio means a state in which one of the polarization components of the polarization, such as 10000: 1, is strong and the other polarization component is very weak.
In order to make the polarization of the laser light parallel or perpendicular to the observation plane L, it is preferable to provide a λ / 2 wavelength plate 6 on the front surface of the laser light generator 1 as shown in FIG.
In the present invention, either the polarizing filter 5 or the polarizing prism and the λ / 2 wavelength plate 6 may be provided, or one of them may be selected and provided.

Here, the light scattered light intensity I _j , which is the intensity of the scattered light when the laser light hits the suspended particles, is detected from the suspended particle by the wavelength λ of the laser light, as shown in the following formulas (1) to (3). It is expressed as a function of the distance R to the vessel, the scattering angle θ, the particle size parameter α, and the particle refractive index m.

  Here, d represents the particle size of the suspended particles. Further, j = 1 indicates the case of irradiating polarized light perpendicular to the observation plane L, and j = 2 indicates the case of irradiating polarized light parallel to the observation plane L.

The particle refractive index m is one of light scattering parameters, and is represented by a complex number as in the above equation (2). When the particle is non-conductive, the imaginary part n ′ of the refractive index is n ′ = 0, and when it is conductive, the imaginary part n ′ of the refractive index is not n ′ = 0.
Using the above-mentioned characteristic of the imaginary part n ′ of the complex refractive index, the change in the scattered light intensity distribution when n ′ is changed is calculated, and the results are shown in FIGS. Therefore, on the contrary, according to the present invention, the presence or absence of conductivity of the suspended particles can be determined based on the ratio of the intensity of the forward scattered light and the intensity of the back scattered light.

FIG. 3 shows that when the refractive index of the particle m = 1.5-0i, that is, when the particle is not conductive, the particle size parameter α is 20, the wavelength λ is 532 nm, and the particle size d is 3.4 μm. The results of calculating the angular distribution of scattered light intensity are shown.
4 shows that when the refractive index m of the particles is 1.5-1i, that is, when the particles are conductive, the particle size parameter α is 20, the wavelength λ is 532 nm, and the particle size d is 3. The result of calculating the angular distribution of the scattered light intensity as 4 μm is shown.
FIG. 5 shows that when the refractive index of the particle m = 1.5−0.1i, that is, when the particle is conductive, the particle size parameter α is 20, the wavelength λ is 532 nm, and the particle size d is The result of calculating the angular distribution of scattered light intensity as 3.4 μm is shown.
As the scattered light intensity, a value obtained by calculating i _j (j = 1, 2) expressed by the above equation 1 is shown.
3 to 5, the vertical reference line Y shown in FIGS. 1 and 2 corresponds to the line connecting 0 degrees and 180 degrees in FIGS. 3 to 5, and is shown in FIGS. 1 and 2. The horizontal reference line X corresponds to a line connecting 90 degrees and 270 degrees in FIGS. Moreover, the laser beam generator 1 is located at a position of 180 degrees in FIGS. 3 to 5, and irradiates the suspended particles located at the center of the graphs in FIGS. The intensity distribution is shown. Furthermore, the intensity of scattered light at 0 to 90 degrees and 270 to 360 degrees is referred to as forward scattered light intensity, and the intensity of scattered light at 90 to 270 degrees is referred to as backscattered light intensity.
Note that the particle size parameter α indicates the relative size of the particles with respect to the wavelength of the irradiation light. For example, the particle size parameter α = 10 is about 1. when the wavelength λ of the irradiation light is λ = 532 nm. Represents a particle size of 7 μm. In addition, when the solid line in the figure irradiates the polarized light parallel to the observation plane L, and the broken line irradiates the polarized particle perpendicular to the observation plane L from the direction of 180 degrees to the central suspended particle 2, the irradiated light strikes the suspended particle. It shows the distribution of the intensity of the scattered light with respect to how much the generated scattered light is scattered in each direction.

In FIG. 3, it can be seen that the forward scattered light intensity of 30 to 60 degrees in the forward scattered light intensity is much stronger than the backward scattered light intensity of 120 to 150 degrees in the backward scattered light intensity. It can also be seen that the forward scattered light intensity of 300 to 330 degrees of the forward scattered light intensity is much stronger than the backward scattered light intensity of 210 to 240 degrees of the backward scattered light intensity.
In particular, it can be seen that the forward scattered light intensity of 40 to 50 degrees out of the forward scattered light intensity is significantly stronger than the back scattered light intensity of 130 to 140 degrees of the backward scattered light intensity. Further, it can be seen that the forward scattered light intensity of 310 to 320 degrees in the forward scattered light intensity is significantly stronger than the backward scattered light intensity of 220 to 230 degrees of the backward scattered light intensity.

Also, in FIG. 4, it can be seen that the forward scattered light intensity of 30 to 60 degrees out of the forward scattered light intensity is weaker than the backward scattered light intensity of 120 degrees to 150 degrees of the backward scattered light intensity. It can also be seen that the forward scattered light intensity of 300 to 330 degrees in the forward scattered light intensity is weaker than the backward scattered light intensity of 210 to 240 degrees of the backward scattered light intensity.
In particular, it can be seen that the forward scattered light intensity of 40 to 50 degrees out of the forward scattered light intensity is significantly weaker than the back scattered light intensity of 130 to 140 degrees of the backward scattered light intensity. Moreover, it turns out that the forward scattered light intensity of 310 degree | times -320 degree | times among the forward scattered light intensity | strength is remarkably weaker than the backward scattered light intensity | strength of 220 degree | times -230 degree | times among back scattered light intensity | strength.

Further, in FIG. 5, it can be seen that the forward scattered light intensity of 30 to 60 degrees in the forward scattered light intensity is comparable to the backward scattered light intensity of 120 degrees to 150 degrees of the backward scattered light intensity. It can also be seen that the forward scattered light intensity of 300 to 330 degrees of the forward scattered light intensity is comparable to the backward scattered light intensity of 210 to 240 degrees of the backward scattered light intensity.
Furthermore, it can be seen that the forward scattered light intensity of 40 to 50 degrees out of the forward scattered light intensity is comparable to the backward scattered light intensity of 130 degrees to 140 degrees of the backward scattered light intensity. It can also be seen that the forward scattered light intensity of 310 to 320 degrees of the forward scattered light intensity is comparable to the backward scattered light intensity of 220 to 230 degrees of the backward scattered light intensity.

  The forward scattered light intensity from 30 degrees to 60 degrees in m = 1.5-0i in FIG. 3 is 30 in m = 1.5-0.1i in FIG. 4 and m = 1.5-1i in FIG. It can also be seen that it is stronger than the forward scattered light intensity of 60 degrees to 60 degrees. Further, the forward scattered light intensity of 300 to 330 degrees at m = 1.5-0i in FIG. 3 is 300 at m = 1.5-0.1i in FIG. 4 and m = 1.5-1i in FIG. It can also be seen that it is stronger than the forward scattered light intensity of .degree.

  In the present invention, an example of a suitable detection angle range of forward scattered light or back scattered light has been described above. However, when a part of scattered light within the angular range is taken in as an intensity comparison reference, It should be added that both forms of capturing all scattered light within the range as an intensity comparison standard are included.

  Here, according to many other trials by the present inventors, when the particle size parameter α is 1, there is no significant difference between the scattered light intensity of the conductive particles and the scattered light intensity of the nonconductive particles. It was. However, when the particle size parameter α is 10 or more, the forward scattered light intensity of 0 to 90 degrees and 270 to 360 degrees is related to the intensity distribution when the non-conductive particles are irradiated with polarized light parallel to the observation surface. However, it tends to be stronger than the backscattered light intensity of 90 to 270 degrees. When the particle size parameter α is 10 or more, the forward scattered light intensity of 0 ° to 90 ° and 270 ° to 360 ° is related to the intensity distribution when the conductive particles are irradiated with polarized light parallel to the observation surface. , It tends to be the same or weak with respect to the backscattered light intensity of 90 to 270 degrees.

In FIG. 3 to FIG. 5, since there is a particular difference between the scattered light of 40 to 50 degrees and the scattered light of 130 to 140 degrees, the forward scattered light intensity _If shown in the following formula (4), FIG. 6 shows the ratio (I _f / I _b ) of the backscattered light intensity I _b shown in the following formula (5).

According to FIG. 6, when the particle size parameter α of the suspended particles 2 is larger than about 20, there is a difference in the ratio (I _f / I _b ). That is, when the particle refractive index m of the suspended particle 2 is 1.5-0i and the suspended particle 2 is a non-conductive particle, the ratio (I _f / I _b ) is larger when the particle size parameter α is 20 or more. Is about 7 or more. In addition, when the particle refractive index m of the floating particle 2 is 1.5-1i or 1.5-0.1i and the floating particle 2 is a conductive particle, when the particle size parameter α is 20 or more, The ratio (I _f / I _b ) is about 2 or less.
Therefore, for particles having a particle size parameter α greater than about 20 for the suspended particles 2, the value of the ratio (I _f / I _b ) between about 2 and 7 is used as a threshold value, and the conductivity of the suspended particles is measured. It was verified by experiment whether it was possible to determine the presence or absence.

In this experiment, a particle conductivity discriminating apparatus as shown in FIG. 2 was used.
Specifically, the laser beam is emitted from the laser beam generator 1 to the floating particles 2, and the forward scattered light and the back scattered light generated when the laser beam strikes the floating particles 2 are converted into the forward scattered light detector 3 and the back scattered light. A collimating lens 9 installed in front of the detector 4 generates parallel light, and the forward scattered light detector 3 and the condensing lens 10 installed between the backscattered light detector 4 and the collimating lens 9. After condensing, the light was detected by a photodiode which is the forward scattered light detector 3 and the backward scattered light detector 4.
3 to 5, when polarized light parallel to the observation surface L is used, a difference is observed between the forward scattered light intensity and the back scattered light intensity. / 2 wavelength plate 6 is provided to irradiate only polarized light parallel to the observation surface.
3 to 5, when polarized light parallel to the observation surface L is used, a difference is seen between the forward scattered light intensity and the back scattered light intensity. Therefore, the collimating lens 9 and the condensing lens are used. A polarizing filter 5 is provided between 10 so as to detect only polarized light parallel to the observation surface.
Further, according to FIGS. 3 to 5, among the forward scattered light and the back scattered light, a remarkable difference was observed in the range of 40 to 50 degrees and the range of 130 to 140 degrees. In order to detect, an iris was provided as a light reception angle adjusting device 7 in front of each collimating lens 9.
In addition, an interference filter 8 for removing inelastic scattered light such as fluorescence is provided between the collimating lens 9 and the condensing lens 10.

  Details of the experiment will be described below. The laser used was a second harmonic of an Nd: YAG laser having a wavelength of 532 nm and an output of 2 W. The laser beam was irradiated so as to be polarized parallel to the observation surface at the measurement point. As the suspended particles 2 for measuring the presence or absence of conductivity, dry powder was supplied to the measurement point by air conveyance. As measurement particles, about 30 μm glass beads GBL-30 (Japan Powder Industry Association) were used as non-conductive particles. Moreover, about 2-10 micrometers Ni (Duke Scientific) was used as electroconductive particle.

Experimental results are shown in FIGS. In each graph, the horizontal axis represents the forward scattered light intensity I _f , and the vertical axis represents the back scattered light intensity I _b . The solid line in the figure shows the case of a I _f / I _b = 2 as a threshold value I _f / I _b to determine the presence or absence of conductive particles. If it is on the right side of the solid line, the suspended particle 2 is non-conductive, and if it is on the left side, it indicates that the suspended particle 2 is electrically conductive. In the case of the glass beads in FIG. 7, the glass beads are generally distributed on the right side of the line of I _f / I _b = 2 and indicate non-conductivity. In the case of Ni in FIG. 8, it is distributed on the left side of the line of I _f / I _b = 2 in general, indicating that it is conductive.
As a result, the forward scattered light intensity I _f and the back scattered light intensity I _b of each particle are measured, and each floating particle 2 has conductivity by providing an appropriate threshold for the ratio I _f / I _b. It was shown that it can be determined whether or not.

  In the above-described example, an example is described in which measurement is performed at points using a laser beam as irradiation light generated from the laser light generator 1 and using photodiodes as the forward scattered light detector 3 and the back scattered light detector 4. In this example of measuring at a point, in addition to an optical sensor such as a photodiode, a condensing optical system using a lens, a polarizing filter that transmits only specific polarized light in front of a detector, and an inelastic scattering such as fluorescence An interference filter for removing light and an opening for adjusting the light receiving angle may be provided.

As another example, as shown in FIG. 9, a two-dimensional laser light sheet is used as irradiation light generated from the laser light generator 1, and a two-dimensional laser light detector 3 and a backscattered light detector 4 are two-dimensional. You may measure in two dimensions using an image sensor. Also in this example, in addition to a camera and a camera lens using an imaging device such as an imaging tube, a CCD, and a CMOS, a polarizing filter that transmits only specific polarized light, and interference for removing inelastically scattered light such as fluorescence. You may provide the filter and the opening for adjusting a light reception angle.
Further, either the polarizing filter 5 or the polarizing prism may be provided in front of the laser light generator 1 and the λ / 2 wavelength plate 6 may be provided.
Furthermore, the camera installation method is not perpendicular to the laser light sheet, and depending on the angle of the camera with respect to the laser light sheet and the F value of the camera lens, the entire photographing area may not be in focus. For this reason, a camera lens having a tilt mechanism may be used.

In the experiment, forward scattered light in the range of 40 degrees to 50 degrees and back scattered light in the range of 130 degrees to 140 degrees were detected, and the results were analyzed.
However, according to the present invention, the conductivity of the particles can be determined using scattered light outside the range.

For example, in FIGS. 3 to 5, there is a difference between forward scattered light of 30 to 40 degrees and backward scattered light of 140 to 150 degrees. Therefore, the forward scattered light intensity _{If if} θ _f1 = 30 [deg] and θ _f2 = 40 [deg] in the equation (4), and θ _b1 = 140 [deg] and θ _b2 = in the equation (5). FIG. 10 shows the ratio (I _f / I _b ) of the backscattered light intensity I _b at 150 [deg].

According to FIG. 10, when the particle size parameter α of the suspended particles 2 is larger than about 20, there is a difference in the ratio (I _f / I _b ). That is, when the particle refractive index m of the suspended particle 2 is 1.5-0i and the suspended particle 2 is a non-conductive particle, the ratio (I _f / I _b ) is larger when the particle size parameter α is 20 or more. Is about 7 or more. In addition, when the particle refractive index m of the floating particle 2 is 1.5-1i or 1.5-0.1i and the floating particle 2 is a conductive particle, when the particle size parameter α is 20 or more, The ratio (I _f / I _b ) is about 6 or less.

Further, in FIGS. 3 to 5, there is a significant difference between the forward scattered light of 50 to 60 degrees and the back scattered light of 120 to 130 degrees. Therefore, the forward scattered light intensity I _f with θ _f1 = 50 [deg] and θ _f2 = 60 [deg] in the equation (4), and θ _b1 = 120 [deg] and θ _b2 = in the equation (5). The ratio (I _f / I _b ) of the backscattered light intensity I _b at 130 [deg] is shown in FIG.

According to FIG. 11, when the particle size parameter α of the suspended particles 2 is larger than about 20, there is a difference in the ratio (I _f / I _b ). That is, when the particle refractive index m of the suspended particle 2 is 1.5-0i and the suspended particle 2 is a non-conductive particle, the ratio (I _f / I _b ) is larger when the particle size parameter α is 20 or more. Is about 4 or more. In addition, when the particle refractive index m of the floating particle 2 is 1.5-1i or 1.5-0.1i and the floating particle 2 is a conductive particle, when the particle size parameter α is 20 or more, The ratio (I _f / I _b ) is about 1 or less.

Therefore, even when the scattered light in the above range is used, a clear difference appears in the ratio (I _f / I _b ).
Accordingly, by measuring the forward scattered light intensity I _f and the back scattered light intensity I _b in the above range and setting an appropriate threshold for the ratio I _f / I _b , whether each suspended particle 2 has conductivity. It can be determined whether or not.
As the threshold value in this case, the value of the ratio (I _f / I _b ) in which a clear difference appears between the conductive particles and the non-conductive particles is used using graphs such as FIG. 6, FIG. 10, and FIG. Is preferred.

1: laser light generator, 2: suspended particles, 3: forward scattered light detector, 4: back scattered light detector, 5: polarizing filter, 6: λ / 2 wavelength plate, 7: acceptance angle adjusting device, 8: Interference filter, 9: collimating lens, 10: condenser lens.
L: Observation surface

Claims (8)

A method for determining whether particles suspended in space have electrical conductivity,
Irradiate the floating particles to be discriminated with laser light emitted from a laser light generator,
In the floating particles having a particle size parameter α (α = πd / λ, where d: particle size, λ: wavelength of laser light) is 20 or more,
Forward scattered light and back scattered light generated by the irradiation are detected by a forward scattered light detector and a back scattered light detector,
At least one of the forward scattered light intensities within a range of 30 ° to 60 ° and a range of 300 ° to 330 ° of a particle scattering angle with respect to an incident line of laser light;
Determining the presence or absence of conductivity of the suspended particles based on the ratio of at least one of the backscattered light intensity within a range of 120 to 150 degrees and within a range of 210 to 240 degrees;
A method for determining particle conductivity. The laser beam generator is a device that generates a laser beam,
The forward scattered light detector is a photodiode or a photomultiplier;
The particle conductivity determination method according to claim 1, wherein the backscattered light detector is a photodiode or a photomultiplier tube.   The particle conductivity determination method according to claim 1, wherein the laser light generation device is a device that generates a laser light sheet, and the forward scattered light detector and the back scattered light detector are imaging elements.   The particle conductivity determination method according to any one of claims 1 to 3, wherein a polarization filter is provided on a front surface of the forward scattered light detector and the back scattered light detector to detect polarized light parallel to the observation surface.   The at least one selected from a polarizing filter or a polarizing prism and a λ / 2 wavelength plate is provided on the front surface of the laser light generator, and the polarized light parallel to the observation surface is irradiated. The particle | grain conductivity discrimination method of 1-4.   A light receiving angle adjusting device is provided in front of the forward scattered light detector and the back scattered light detector, and at least one of the forward scattered light having a particle scattering angle of 40 to 50 degrees and 310 to 320 degrees with respect to the incident line of the laser light. And at least one of the backscattered light of 130 to 140 degrees and 220 to 230 degrees is detected.   The particle conductivity determination method according to any one of claims 1 to 6, wherein an interference filter is provided in front of the forward scattered light detector and the back scattered light detector. An apparatus for determining whether particles floating in space have electrical conductivity,
A laser beam generator for irradiating the floating particles to be discriminated with a laser beam;
In the floating particles having a particle size parameter α (α = πd / λ, where d: particle size, λ: wavelength of laser light) is 20 or more,
A forward scattered light detector and a back scattered light detector for detecting forward scattered light and backward scattered light generated by the irradiation;
The intensity of at least one of the forward scattered light within a range of a particle scattering angle of 30 to 60 degrees and a range of 300 to 330 degrees with respect to an incident line of laser light;
Means for determining the presence or absence of conductivity of the suspended particles based on the ratio of the intensity of the backscattered light in at least one of the range of 120 to 150 degrees and the range of 210 to 240 degrees;
A particle conductivity discriminating apparatus characterized by comprising:

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