JP2009162712A - Suspended particulate matter measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To focus detecting object particles dielectric-polarized by electrostatic field application in an observation visual field. <P>SOLUTION: This suspended particulate matter measuring device includes a prism for dividing scattered light whose scattering angle is substantially 10°, among scattered lights by incoming of a polarized beam into the particles, into two light beams whose polarization directions are orthogonal to each other, a particle aligning means for turning the particles to the normal line direction of the scattering plane before the light beams come into the particles, a light receiving section for converting the two light beams into electric signals, and a particle identifying means for identifying the particle shapes. The particle aligning means is formed of electrode blocks 230a and 230b, and generates an electrostatic field directing in the normal line direction of the scattering plane between the electrode blocks 230a and 230b. The electrode blocks 230a and 230b are parallel flat plane shapes whose guide channel side surfaces are flat, or projecting shapes toward the facing electrode blocks whose guide channel side surfaces are curved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention optically detects minute particles floating in a fluid, and identifies whether the shape of the particles is spherical or fiber, especially by approximating the fiber particles by cylindrical particles. The present invention relates to a substance measuring device.

  A conventional suspended particulate matter measuring device is provided with a fluid inlet and a fluid outlet in a glass tube called a cylindrical flow tube, and a sample fluid in which particles to be detected such as fibrous particles are dispersed is placed in the flow tube. In addition to introducing a light beam from the length or side of the flow tube and measuring the scattered light generated in the flow tube with a detector placed on the wall side of the flow tube, The number of airborne microparticles or the number of fibrous particles was detected in real time.

  The apparatus for discriminating the shape of the microparticles by measuring the scattered light by the microparticles in the flow tube is roughly divided into two types of apparatuses, that is, a first that modulates scattered light in a rotating electric field by quadruple electrodes. And a second type of device that measures the degree of polarization of backscattered light in an electrostatic field by a counter electrode (for example, see Non-Patent Literature 2 and Patent Literature 1). Recently developed.

  In the first type of apparatus, as shown in FIG. 11, the laser beam 32 is irradiated from the light source 3 along the length direction of the flow tube 20A, and the detection target particles 1 sucked into the flow tube 20A It is introduced into a quadruple electrode provided in the detector 40a on the flow tube wall side. As shown in FIG. 12, the quadrupole electrode 23E (23Ea, 23Ea ′, 23Eb, 23Eb ′) is provided with a counter electrode in the direction of the rotational symmetry axis (cylindrical axis) of the flow tube along the tube wall. The counter electrodes are configured to be orthogonal to each other with respect to the cylindrical axis. A rotating electric field vector 41 is formed by applying an alternating high voltage of the same frequency with a phase difference of 90 degrees between the opposing electrodes. The fibrous particle 1 to be detected introduced into the rotating electric field vector 41 is attracted by a strong electric field formed between opposing electrodes, for example, 23Eb and 23Eb ', and dielectrically polarized to stretch the fiber. While deforming into a shape that can be approximated as a columnar particle, the main axis 1a of the columnar particle rotates following the rotating electric field vector 41 in synchronization with the AC frequency. The target particle 1 that has been transformed into a cylindrical particle is irradiated with a laser beam 32 from a direction perpendicular to the plane of rotation, and 90-degree side scattered light is detected.

  The intensity of the side scattered light changes in synchronization with the rotation of the high-voltage electric field (that is, the frequency of the applied AC voltage), and the longer fiber-like detection target particle 1 is stretched in the direction in which the electric field is applied. Since it is transformed into particles, the fluctuation range of the scattered light intensity becomes large. This phenomenon is equivalent to the prospective cross-sectional area becoming larger or smaller with the rotation of the cylinder when the rotating cylinder is viewed from the direction perpendicular to the rotation axis.

  On the other hand, when the detection target particle 1 is a spherical particle, the particle is dielectrically rotated in synchronization with the rotation of the high-voltage electric field, but the scattering cross section seen in the rotation plane remains spherical. Therefore, they are the same, and the scattered light intensity is not strongly modulated by the rotating electric field. This is because the spherical detection target particle 1 is symmetric with respect to rotation. From the above, it is possible to discriminate between fibrous particles and spherical particles approximated as columnar particles by measuring the presence or absence of fluctuations in 90 ° side scattered light intensity associated with the electric field rotation angle θ.

  FIG. 13A is a plan view of the second type apparatus, and FIG. 13B is a side view of the apparatus of FIG. In FIG. 13A, it is assumed that the inside of the flow pipe and the branch pipe is seen through. In the second type apparatus, as shown in FIGS. 13A and 13B, the sample fluid in which the detection target particles 1 are dispersed flows in the flow tube 20B. Two branch pipes 20C having a cross-sectional size smaller than the cross section of the inner wall thereof are connected to the flow pipe 20B so as to be orthogonal to the flow pipe 20B, and an arc-shaped particle orientation electrode 23F is connected to the flow pipe 20B. Attached along the axis. As a result, the fibrous particles 1 to be detected introduced into the flow tube 20B are dielectrically polarized by a high-voltage electrostatic field and stretched in the direction of electric field application so as to be deformed into a shape that can be approximated as cylindrical particles. Turn in the direction. After that, the laser beam 32 polarized in a specific direction from the external light source 3 is irradiated into the flow tube 20B from the end surface of the branch tube 20C and is incident on the detection target particle 1. By arranging the detector 40b adjacent to the light source 3 of the branch tube 20C, the backscattered light generated in the flow tube 20B can be measured.

  In the second method, instead of rotating the fibrous particle 1 to be detected within the observation field by the rotating electric field vector 41 as in the first method, the arc-shaped particle orientation electrode 23F attached to the flow tube 20B. Is passed through an electrostatic field formed by. Thus, the main axis of the detection target particle 1 approximated as a cylindrical particle is directed to the electrostatic field application direction, and then the linearly polarized beam 32 is incident on the detection target particle 1 deformed into a cylindrical shape. The polarization state of the backscattered light is measured by the detector 40b.

  By the way, as described in Non-Patent Document 2, the polarization state of backscattered light is greatly different between spherical particles and cylindrical particles. Specifically, in the case of the detection target particle 1 deformed into a cylindrical shape, the polarization component parallel to the major axis direction of the particle 1 oriented in the normal direction of the scattering plane (that is, the polarization component perpendicular to the scattering plane). Become stronger. On the other hand, in the case of the spherical particle 1 to be detected, the polarization component parallel to the scattering plane is strong. Using such polarization characteristics of backscattered light, it is possible to distinguish between fibrous particles and spherical particles.

Japanese Patent No. 2881731 Pedro Lilienfeld, “Light Scattering from Oscillating Fibers at Normal Incidence”, J. Aeroso1.Sci, Vo1.18, No.4, p.389-400, 1987 N.Hiromoto, K.Hashiguchi, S.Ito, and T.Itabe, “Asbestos Real-Time Monitor in an Atmospheric Environment”, Applied Optics, vol.36, No.36, p.9475-9480, 1997

  In the above suspended particulate matter measuring apparatus, in both the first and second methods, the counting of the fibrous detection target particles 1 is performed in a rotating electric field by a quadruple electrode or in a non-uniform electrostatic field by a counter electrode. Statistical fluctuations due to the non-uniformity of the particle distribution of the particles, especially when the oriented particles dissipate from within the very narrow observation field, one or two countdown results in a large statistic. There was a problem of giving the target fluctuation. Hereinafter, this statistical fluctuation will be described in detail.

In the suspended particulate matter measuring device, the count amount for the target particle 1 introduced into the flow tube is (1) the number of particles in the observation field, or (2) the number of particles in the observation field within the unit counting time. It is. In an ordinary light-scattering microparticle measurement apparatus that does not require application of an electric field for directing particles in a desired direction, it can be assumed that the uniformity and isotropy of the space in the observation field are established. In this case, the sample fluid introduced into the flow tube having a cross-sectional area A [cm ² ] at a flow velocity v [cm / s] during Δt [s] occupies a volume V = A · v · Δt [cm ³ ]. . If there are N minute target particles 1 to be detected in the volume V, if the space is uniform and isotropic, the target particle 1 has a concentration C = N / V [number / cm ^3. ] May be considered to be uniformly distributed.

If the laser beam 32 from the light source 3 illuminates the sample fluid with the irradiation area length ξ [cm] in the flow direction at the beam diameter D _R [cm], the volume ν of the observation field is π. As the circumference ratio, ν = π (D _R ) ² ξ / 4. The volume ν of the observation field is sufficiently larger than the volume of the particle 1 to be detected, and it may be approximated that the particle 1 to be detected moves independently in the field of observation. In this case, when an arbitrary one of N detection target particles 1 is focused, the probability that the particle exists in the observation field is given by p = ν / V. Considering the probability P (n) that n particles 1 to be detected are present, n particles are present in this observation field, and at the same time, the remaining N−n particles have a volume V−ν outside of the observation field. Since it exists in the area, its probability distribution is given by the Bernoulli distribution given by equation (1).
P (n) = N! / [N! (Nn)! ] ・ (Ν / V) ⁿ (1-ν / V) ^Nn
... (1)

Therefore, the average value <n> of the number of detection target particles 1 found in the observation field and the variance σ ² are given as follows.
<N> = (ν / V) · N = p · N = C · ν (2a)
σ ² = <(n− <n>) ² > = (1−ν / V) · (ν / V) · N
= (1-p) <n> (2b)

The ratio between the deviation σ from the average value and the average value <n> is obtained as follows.
σ / <n> = [(V−ν) / (ν · N)] ^1/2
= [(1-p) / <n>] ^1/2 (2c)

In the actual counting process of the suspended particles, the sample fluid sampled is introduced into the flow tube, passed through the observation field illuminated by the thin laser beam 32, and the scattered light at that time is photoelectrically converted by the light receiving unit. Count as an electrical pulse. In the case of using a laser as a light source 3, the beam diameter D _R will 0.1 [mm] or less have been considerably narrowed. On the other hand, the cross-sectional area A of the flow tube cannot be made very thin in relation to the flow rate in order to sample a certain amount of sample fluid. Therefore, the probability p = ν / V determined by the ratio between the volume ν of the observation field and the volume V of the sample fluid is extremely small (p << 1), and the average value <n> = N · p = C · ν is In the limit that maintains a constant value, the Bernoulli distribution of equation (1) can be approximated by the Poisson distribution given by the following equation (3).
P (n) = exp (−C · ν) (C · ν) ⁿ / n! ... (3)

In this case, both the average value <n> and the variance σ ² are given by the following equations.
<N> = σ ² = N · p = C · ν (4a)
The ratio between the deviation value σ from the average value and the average value <n> is as follows.
σ / <n> = <n> ^−1/2 = (C · ν) ^−1/2 (4b)

For example, if the total number N of particles in the flow tube is about 10 ⁴ and the volume ratio p = ν / V is 1/100, the average value <n> is 100, and the statistics of the count value given by equation (4b) Target fluctuation reaches 10%.

On the other hand, if two or more detection target particles 1 enter the observation field at the same time, a coincidence loss that is counted as one pulse occurs. Specifically, by calculating the sum of the probabilities that two or more detection target particles 1 are found within the volume ν of the observation field, the probability Q of occurrence of coincidence loss is given by the following equation (5).
Q = Σ _{n =} ^2∞ P (n) = 1−exp (−C · ν) (1 + C · ν) (5)

That is, the coincidence loss is determined by the volume ν of the observation field and the concentration C of the detection target particle 1 in the sample fluid. Therefore, from the viewpoint of keeping the coincidence loss rate Q low (for example, 10% or less) and designing the measurable concentration C _Max to be large, the volume ν of the observation field should be made as small as possible, or the particles introduced into the flow tube It is necessary to lower the coincidence loss rate Q by lowering the concentration C (dilution measurement). Reducing the volume ν of the observation field is structural, and it can be said that reducing the concentration C of particles introduced into the flow tube is a measurement technique.

However, as shown in equation (4b), when the volume ν of the observation field is small and the concentration C of the detection target particle 1 in the sample fluid is also low, one particle or two particles in the observation field are counted. If dropped, the effect on statistical fluctuation is extremely large.
As described above, the space is anisotropic in the rotating electric field and the non-uniform electric field formed by the quadruple electrodes, and the uniformity of the particle distribution within the space is not ensured. Since an electric field is applied to identify the shape of the particle 1 to be detected, it is unavoidable that the isotropic property is broken. However, in a rotating electric field or a non-uniform electric field where the detection target particle 1 is dissipated from a very narrow observation field, the counting of two by one gives a large statistical fluctuation to the count value. As mentioned above, it is a problem.

Next, a non-uniform electric field having a conventional configuration that causes counting down will be described.
In both of the first and second methods, the fibrous detection target particles 1 are introduced into the cylindrical flow tubes 20A and 20B to be transformed into columnar particles, and are further rotated or directed in a specific direction. For this purpose, arc-shaped electrodes 23E and 23F are attached to a glass tube wall having a circular cross section and a high voltage is applied. A counter electrode for particle orientation is provided along the sample fluid flow path to form a high-voltage electric field. However, in a flow tube with a circular cross section, the electrode shape is an arc shape, and the inside of the electrode forming part in the flow tube The electric field formed is not necessarily uniform. An inhomogeneous electric field is generated between adjacent electrode terminals and acts divergently on the cylindrical particle 1 to be detected that has become an electric dipole by dielectric polarization, that is, by irradiating a light beam. As a result, the electric dipole is attracted from the central region to the peripheral portion of the flow tube, so that the detection target particle 1 is dissipated from the observation field of view and the statistical fluctuation is remarkably increased.

  This will be described with reference to FIGS. 14A to 14E and FIG. FIG. 14 (A) is a diagram showing the extension action of particles by a uniform electric field, FIG. 14 (B) is a diagram showing the rotation of the electric dipole by the electric field torque, and FIG. 14 (C) is the electric dipole in the electric field direction. FIG. 14 (D) shows the orientation, FIG. 14 (D) shows the force acting on the electric dipole due to the non-uniform electric field, and FIG. 14 (E) shows how the particles deviate from the observation field area (light beam irradiation area). It is sectional drawing.

In general, an electric dipole placed in a uniform electric field E is rotated in the direction in which the electric field is applied by applying a torque τ given by the following equation (6), where p is the dipole moment. The direction is parallel to.
τ = p × E (6)

On the other hand, the vector force F determined by the dipole moment p and the gradient of the non-uniform electric field further acts on the electric dipole that has entered the non-uniform electric field, so that the electric dipole moves in the direction in which the electric field strength is large. That is, the force given by the following equation (7) acts on the electric dipole.
F = (p · ∇) E (7)
In Expressions (6) and (7),... Indicates a vector inner product, X indicates a vector outer product, and ∇ indicates a gradient operator.

  As shown in FIG. 14 (A), the curved fibrous detection target particle 1 guided in the external uniform electric field E from the positive electrode to the negative electrode instantaneously generates dielectric polarization. One end of the particle 1 near the positive electrode forming the electric field E is charged to the negative electrode, and at the same time, the other end of the particle 1 near the negative electrode of the electric field E is charged to the positive electrode. In such a uniform electric field, the polarized bent fiber-like particles 1 to be detected are stretched in the direction of the electric field and deformed into a linear shape, and also deformed into a cylindrical shape as shown in FIG. Rotational torque acts on 1, and the particles 1 face in a direction parallel to the electric field E as shown in FIG.

  Here, when cylindrical particles are introduced into a non-uniform electric field, the electric charge generated at both ends due to dielectric polarization is equal, but the force acting on both induced charges of the dipole depends on the density of the electric field lines of the electric field. Different. For this reason, as shown in FIG. 14D, a net force acts on the electric dipole in the non-uniform electric field in the direction in which the electric field becomes stronger.

FIG. 15A is a diagram showing the electric field vector distribution along the circular section of the circular arc quadrupole electrode 23E formed around the cylindrical flow tube 20A, and FIG. 15B is a dielectric-polarized electric bipolar. It is the figure which showed along the cross section of the cylinder the force vector distribution which acts on a child.
In the first system, the quadruple electrode 23E is provided in order to rotate the fibrous target particle 1 to be detected. However, the non-uniform electric field generated between the adjacent electrodes is a high voltage between the counter electrodes. An electric force that acts on the electric dipole that is dielectrically polarized by the electric field and dissipates the electric dipole from the center of the flow tube 20A (irradiation region of the light source 3 of the specific polarization) as shown in FIG. Act. For this reason, as shown in FIG. 14E, the detection target particle 1 deformed into a cylindrical shape is transported outside the irradiation region of the incident laser beam 32. For this reason, the count value of the detection target particles 1 in the observation visual field is smaller than that in the case of uniform distribution, and the statistical fluctuation thereof also increases.

  Furthermore, since the fibrous detection target particles 1 dispersed in the sample fluid are usually curved, they are stretched in a strong electric field to improve linearity, and try to approximate them accurately as cylindrical particles. Since an alternating voltage is applied between the quadruple electrodes 23E to rotate the particles, it is also estimated that the extension is not sufficient. That is, in comparison with rod-shaped particles such as amosite and crocidolite that form a asbestos, curved particles such as chrysotile (white asbestos) cannot be sufficiently stretched in a rotating electric field by the quadrupole electrode 23E. The approximation is not sufficient, and it will be counted off from the count as cylindrical particles.

FIG. 16A shows the electric field vector distribution along the cylindrical cross section of the circular particle orientation electrode 23F formed around the cylindrical flow tube 20B, and FIG. 16B shows dielectric-polarized electricity. It is the figure which showed force vector distribution which acts on a dipole along the cross section of a cylinder.
As shown in FIGS. 16 (A) and 16 (B), in the apparatus of the second method, a high voltage is applied between the counter electrodes 23F in order to direct the fibrous detection target particles 1 in the direction of applying a high voltage electric field. An electrostatic field is formed by applying a voltage. Accordingly, the fibrous detection target particles 1 introduced into the flow tube 20B are held in a polarized state for a long time, and the curved detection target particles 1 are also stretched in a straight line. There are few countdowns due to poor approximation.

  However, even if the device of the second system is a small amount as compared with the device of the first system, counting down has been reported (see Non-Patent Document 2). As the reason, concentration of electric lines of force on the end region of the counter electrode can be considered. That is, although a high voltage is applied between the opposing electrodes 23F in order to direct the fibrous particles 1 to be detected in the direction in which the high voltage electric field is applied, concentration of electric lines of force occurs at the ends of the opposing electrodes, The electric field strength in the region is significantly stronger than in the other parts. In such a non-uniform electric field, as in the case of the quadruple electrode 23E described above, as shown in FIG. It is considered that an electric force that dissipates the particles 1 acts from the center (irradiation region of the light source 3 having a specific polarization). For this reason, the count value of the detection target particles 1 in the observation field is slightly smaller than that in the case of uniform distribution, and is counted down to increase the statistical fluctuation.

  The present invention has been made to solve the above problems, and when introducing the particles to be detected into the observation field of the detector, the particles to be detected that are dielectrically polarized by applying an electrostatic field concentrate in the field of observation. An object of the present invention is to provide such a suspended particulate matter measuring apparatus.

  The suspended particulate matter measuring device according to the present invention includes a light source that emits a polarized beam, and an introduction unit that introduces a detection target particle suspended in a fluid into an observation field in a laminar flow state by a sample fluid channel. Of the scattered light resulting from the incidence of the polarized beam from the light source on the particle introduced into the observation field, the scattering angle centered on the particle with respect to the direction from the light source toward the particle is approximately 10 degrees. A polarization beam splitter prism that splits the scattered light into two light beams whose polarization directions are orthogonal to each other, and the light source, the particles, and the polarization beam splitter prism before the light beam is incident on the particles. And two light beams divided by the polarizing beam splitter prism and particle orientation means for directing the particles in the normal direction of the scattering plane. The first and second light receiving means for converting into an electrical signal; and the particle identifying means for identifying the particle shape based on the signals output from the first and second light receiving means; Consists of two electrode blocks arranged along the sample fluid conduit, and forms an electrostatic field between the electrode blocks in the normal direction of the scattering plane. The two electrode blocks The guide channel side surfaces are flat and parallel to each other, or the guide channel side surfaces are convex with respect to the opposing electrode blocks with curved surfaces.

Further, in one configuration example of the suspended particulate matter measuring device of the present invention, the two electrode blocks are parallel flat plates whose width in the direction orthogonal to the sample fluid guide channel is wider than the width of the sample fluid guide channel. A uniform electrostatic field is formed in the sample fluid guide channel covering the observation field by applying a voltage between the two electrode blocks.
Further, in one configuration example of the suspended particulate matter measuring device of the present invention, the two electrode blocks have a rectangular longitudinal section along the sample fluid guide channel, and are crossed perpendicular to the sample fluid guide channel. The end shape of the surface is a Rogowski type end shape, and an electrostatic field in which the electric field strength gradually increases toward the center in the sample fluid guide channel covering the observation field by applying a voltage between the two electrode blocks. To form.
Moreover, in one structural example of the suspended particulate matter measuring device of the present invention, the two electrode blocks have a rectangular longitudinal section along the sample fluid guide channel, and are a plane orthogonal to the sample fluid guide channel. An electrostatic field in which the electric field strength gradually increases toward the center in the sample fluid channel that covers the observation field by applying a voltage between the two electrode blocks. Is formed.
Moreover, in one structural example of the suspended particulate matter measuring device of the present invention, the two electrode blocks have a rectangular longitudinal section along the sample fluid guide channel, and are a plane orthogonal to the sample fluid guide channel. The surface curve on the side of the guiding channel when cut at a V-shaped curve and an inverted V-shaped curve, and the electric field strength is applied in the sample fluid guiding channel covering the observation field by applying a voltage between the two electrode blocks. It forms an electrostatic field that gradually increases toward the center.

Further, in one configuration example of the suspended particulate matter measuring device of the present invention, the introduction means includes two guide blocks made of an insulating material and two insulating materials made of an insulating material sandwiching the two guide blocks from above and below. The two guide blocks are used for introducing the polarized beam at a position away from the end surface serving as a sample fluid introduction port by a distance necessary for the fluid to develop into a laminar flow state. An opening and an opening for observing the scattered light are provided, and an optical glass plate is fitted in each opening, and between the upper thick plate block and the two guide blocks and on the lower side The electrode block is disposed between the thick plate block and the two guide blocks, and a region sandwiched between the two electrode blocks and the two guide blocks is disposed in the sample flow. It is an diversion channel.
Moreover, in one structural example of the suspended particulate matter measuring device of the present invention, the electrode block is a metal material, plastic, machinable ceramics, or engineering containing at least one of copper, gold, platinum, silver, or aluminum. When the plastic is used, the electrode block is formed by metal plating or metal vapor deposition on the surface of the conducting channel.
Moreover, in one configuration example of the suspended particulate matter measuring device of the present invention, an insulating film is formed on the surface of the electrode block on the side of the conducting channel.
Further, in one configuration example of the suspended particulate matter measuring device of the present invention, the guide block and the thick plate block are made of plastic, machinable ceramics, or engineering ceramics, and the wall surface of the observation field and the opening The wall surface of the part is coated with a material that absorbs light of the wavelength of the light source.
Moreover, in one structural example of the suspended particulate matter measuring device of the present invention, the optical glass plate is made of a material that is non-reflective at the wavelength of the light of the polarized beam.

In one configuration example of the suspended particulate matter measuring device of the present invention, the light source emits a non-polarized light beam, or a linearly polarized light plane is 45 degrees with respect to the normal direction of the scattering plane. The light beam is emitted either by emitting it as a tilted linearly polarized beam or by passing linearly polarized light through a quarter wave plate and emitting it as a circularly polarized beam, and the minimum wavelength of this light beam is It is characterized by being longer than the radius of the spherical microparticles to be identified and shorter than the length of the cylindrical microparticles.
Further, in one configuration example of the suspended particulate matter measurement device according to the present invention, the particle identification unit includes a vertical polarization component detected by the first light receiving unit and a horizontal polarization component detected by the second light receiving unit. If the intensity difference is substantially equal, the particle is identified as a spherical particle, and if the intensity difference indicates a superior vertical polarization component, the particle is identified as a cylindrical particle. Is.
Further, in one configuration example of the suspended particulate matter measuring device according to the present invention, the particle identification unit calculates a pulse height of a voltage pulse given as a sum of each polarization component detected simultaneously by the first and second light receiving units. The voltage pulse is classified according to its peak value by comparing with a plurality of predetermined threshold voltages, and counted for each pulse, and the particle is a spherical particle based on the identification result of the particle Is identified, the particle radius is determined based on the pulse peak value, and when the particle is identified as a cylindrical particle, the particle length is determined based on the pulse peak value.

  In the present invention, instead of the arcuate quadruple electrode formed around the cylindrical flow tube, an electrostatic field generated by an electrode block wider than the width of the sample fluid guide channel is used, so that the electrode ends adjacent to each other can be switched when the electrode polarity is switched. The electric field non-uniformity generated between the parts can be avoided. Therefore, dissipation of suspended particles from the observation field due to the non-uniform electric field can be avoided. Alternatively, instead of the electrostatic field due to the arcuate counter electrode, a non-uniform electric field generated at the electrode end acts on the electric dipole by using a uniform electrostatic field due to the electrode block wider than the width of the sample fluid channel. Dissipation of particles from the observation field can be avoided. In any case, in the present invention, by avoiding the dissipation of the particles to be detected from within the observation region, one of the particles to be detected from the observation field, which was remarkable in the conventional suspended particulate matter measuring apparatus, 2 It is possible to suppress statistical fluctuation with respect to the count value due to counting off of the number. Furthermore, by using the electrode block having a cross-sectional shape according to the present invention, the particles to be detected that are polarized by the electrostatic field are directed in a specific direction (electrostatic field application direction), and the particles to be detected are steadily placed in the observation field of view. The statistical fluctuation with respect to the count value can be reduced by counting a little more than the case of being able to concentrate and converge, and even when the distribution is uniform. Here, the specific direction is preferably a vertical direction with respect to a scattering plane defined by the three of the light source, the detection target particle, and the light receiving means. In addition, the conventional non-uniform electric field due to the concentration of electric lines of force at the electrode ends can be avoided by devising the cross-sectional shape of the electrode block, and a high voltage close to the dielectric breakdown voltage of the sample fluid can be avoided between the counter electrode blocks. Can be applied. For this reason, compared to the linear particles that make up blue asbestos, such as amosite and crocidolite, even for chrysotile (white asbestos), which is a curved particle, a higher voltage is required to stretch the curved portion and transform it into cylindrical particles. Since it can apply, compared with the case where the conventional arc-shaped electrode is used, the approximate precision as a cylindrical particle of a fibrous particle to be detected improves. As a result, it is possible to improve the detection rate of the particles to be detected in the observation field as cylindrical particles, and to reduce the statistical fluctuation caused by counting off one or two count values. The present invention is based on the technical idea that priority is given to suppressing statistical fluctuations, and systematic errors in overcounting the particles to be detected are corrected by obtaining a calibration curve.

[First Embodiment]
FIG. 1 is a perspective view of a flow channel unit 20 serving as an introduction unit and a particle orientation unit of the suspended particulate matter measurement device according to the first embodiment of the present invention, and FIG. 2 is an exploded perspective view of the flow channel unit 20. .
As shown in FIG. 2, the flow channel section 20 includes two guide blocks 240 made of an insulating material, and two thick plate blocks 250 a and 250 b made of an insulating material sandwiching the two guide blocks 240 from above and below. Consists of A region sandwiched between the two guide blocks 240 and the electrode blocks 230a and 230b forms a sample fluid guiding channel 210e. Further, as shown in FIG. 1, an opening 220a for introducing a specific polarization beam and an opening 220b for scattered light observation are provided so as to be orthogonal to the guide channel 210e.

  More specifically, as shown in FIG. 2, one guide block 240 has a running length L (Starting Length) until the sample fluid introduced from the end surface on the fluid inlet 21a side develops into a laminar flow state. The specific polarized beam introducing opening 220a is provided at a position separated by a distance (details will be described later), and the other guide block 240 is provided for observing scattered light at a position facing the specific polarized beam introducing opening 220a. An opening 220b is provided. Each opening is formed with a counterbore for fitting the guide channel sealing glass window 220c. By inserting the glass passage 220c for guiding channel sealing into these openings, the guiding channel 210e having a high sealing property is formed.

  As the material for the glass window 220c for closing the guide channel, a material that is non-reflective at the wavelength of the light of the specific polarized beam is used. Specifically, a non-reflective film is used to prevent the sample fluid from leaking from the inside of the guide channel 210e and to allow the entrance and exit of the specific polarized beam and the detection of scattered light from the outside of the flow channel section 20. Attached optical glass or the like is used. The glass passage 220c for sealing the guiding channel is necessary for preventing the loss of the specific polarized beam and reducing the irregular reflection inside the flow channel unit 20.

  The upper and lower plank blocks 250a and 250b are formed with countersinks for embedding electrode blocks 230a and 230b having a specific cross-sectional shape as particle orientation means, and the upper plank block 250a and the two guide blocks 240 The electrode blocks 230a and 230b are disposed between the lower thick plate block 250b and the two guide blocks 240, respectively. The electrical connection with the upper electrode block 230a is made by the contact electrode terminal 260a that passes through the upper thick plate block 250a and reaches the electrode block 230a, and the electrical connection with the lower electrode block 230b is made with the lower thick plate. The contact electrode terminal 260b passes through the block 250b and reaches the electrode block 230b. Electrical connection between a bipolar DC high-voltage stabilized power source, which will be described later, and the electrode blocks 230a and 230b is performed by wiring using a crimp terminal or the like.

  Furthermore, in order to function as the fluid intake port 21a and the fluid exhaust port 21b of the flow channel unit 20 at both ends of the structure in which the two guide blocks 240 are sandwiched between the upper and lower thick plate blocks 250a and 250b, An intake joint 210c and an exhaust joint 210d for connecting the exhaust pipe are respectively fixed.

  The flow channel section 20 formed in this way forms a guiding channel 210e for introducing the sample fluid into the observation field in a state where the detection target particles 1 are dispersed in the sample fluid, and is also detected. The particle orientation means is configured to orient the rotational symmetry axis of the target particle 1 in the direction of the electrostatic field formed by the two electrode blocks 230a and 230b. In this flow channel section 20, in order to form an observation field irradiated with irradiation light in a specific polarization state in a state where the detection target particles 1 dispersed in the sample fluid are directed in the electrostatic field application direction. In addition, an opening 220a for introducing a specific polarized beam and an opening 220b for scattered light observation are formed.

Then, by irradiating the specific polarized light from the external light source through the introduction opening 220a from the direction orthogonal to the guide channel 210e, the forward scattered light by the particles 1 to be measured dispersed in the sample fluid is converted into scattered light. Observation is performed through the observation opening 220b.
The cross-sectional shape of the guide channel 210e in the flow channel portion 20 is generally rectangular, but is preferably square. By making the shape square, not only can the structure of the electrode blocks 230a and 230b for applying an electrostatic field be simplified, but also when calculating the approach distance L described later, the analysis model is simplified and the design is easy. become.

The thickness of the guide block 240 is determined by the strength of the electrostatic field necessary to align the directions of the fibrous detection target particles 1. For example, if the thickness of the guide block 240 is 1 cm, 500 V is applied to each of the electrode blocks 230a and 230b in order to form an electrostatic field with an electric field strength of 1 kV / cm in the observation field.
Further, the specific polarized beam introducing opening 220a is formed at a position away from the end face of the guide block 240 on the fluid inlet 21a side by a run-up distance L.

The sample fluid introduced into the flow channel part 20 from the fluid inlet 21 a is normally in a turbulent state due to mismatch between the intake pipe or the intake joint and the cross section of the flow channel part 20.
In general, for a viscous fluid flow having a Reynolds number below a certain critical value, a transition to a laminar flow state occurs even in a sample fluid introduced in a uniform turbulent state in the flow channel section 20, The laminar flow develops during the run-up distance L.

  Therefore, when observing the particle 1 to be detected directed in a specific direction by the electrode blocks 230a and 230b provided in the flow channel unit 20, the turbulent flow state at the inlet portion of the sample fluid disturbs the direction of the particle 1. It is necessary to observe the scattered light in a state where it is not. That is, if the scattered light is observed at a position separated by the run-up distance L, it can be expected that the influence of the disturbance called turbulence on the particle count can be reduced. The influence of the turbulent flow on the particle count is that the direction of the detection target particle 1 is staggered, or the detection target particle 1 flowing in the guide channel 210e is dissipated from the observation field due to the spatial non-uniformity of the electric field. Or to help. Therefore, by providing the specific polarized beam introducing opening 220a at a position away from the intake side end by the run-up distance L, the flow in the observation visual field region is not affected by the turbulent flow.

The Reynolds number Re is the run distance L, the flow velocity U of the sample fluid, and the kinematic viscosity count ν of the sample fluid (= μ / ρ, where μ is the static friction coefficient of the sample fluid and ρ is the density of the sample fluid). Is given by the following equation (8).
Re = U · L / ν (8)

For a cylindrical tube, it is known that the transition Reynolds number at which a transition from turbulent flow to laminar flow occurs is about 2300. If the transition Reynolds number is less than this, strong turbulence occurs at the cylindrical tube inlet. Even in the case of a flow, at a position after the run-up distance L, it can be expected that the flow develops and is in a laminar flow state. Note that the transition Reynolds number of 2300 is a value for the cylindrical tube, and for the square-shaped guide channel 210e having a square cross section of the present embodiment, the value of the transition Reynolds number is the roughness of the wall surface in the tube. Considering that it is affected by the magnitude of minute disturbance of the sample fluid to be introduced, it is about 1000. That is, as a transition condition for developing a turbulent flow into a laminar flow, various parameters were appropriately designed on the assumption that the transition Reynolds number (Re) _trans satisfies the following formula (9).
(Re) _trans <1000 (9)

  The cross-sectional shape of the guide channel 210e of the flow channel unit 20 of the present embodiment and the value of the run-up distance L provided with the specific polarized beam introducing opening 220a are a transition between the conditions of the applied electric field strength and the Reynolds number of the sample fluid. It was designed appropriately so as to satisfy the condition of Equation (9) that is kept below the Reynolds number. At the same time, the flow rate (= flow velocity × cross-sectional area of the guide channel 210e) was set so that the flow velocity U of the sample fluid also stayed within the value of the transition Reynolds number determined by Equation (9).

  As a material for the electrode blocks 230a and 230b having a specific cross-sectional shape, a highly plastic metal plate material such as copper can be used by cutting it into a specific cross-sectional shape as it is. A function as a metal electrode may be provided by plating a metal on the electrode side surface of the material or by directly depositing a metal. The material is not limited to metal or the like as long as the material can realize an electrode having a desired cross-sectional shape with required processing accuracy. This is because a high voltage in the vicinity of the pressure limit of the sample fluid is applied to the electrode blocks 230a and 230b in order to form an electrostatic field in order to align the direction of the particles 1 to be detected introduced into the conducting flow path 210e therebetween. This is because it is not necessary to apply a high voltage higher than the withstand pressure of the sample fluid to flow a large DC current or the like.

  Further, an insulating material is formed on the surface of the electrode blocks 230a and 230b on the side of the conducting channel (the lower surface in the case of the electrode block 230a, the upper surface in the case of the electrode block 230b) as a protective film for the metal layer. Has been. Alternatively, an insulating metal oxide may be formed on the surfaces of the electrode blocks 230a and 230b. In this way, by forming an insulating film on the surface of the electrode blocks 230a and 230b on the conducting flow path side, the fine particles adhering to the electrode surface are charged with the same polarity as the electrode, repelled by coulomb rebound, and moved to the counter electrode block side. It is possible to avoid rushing and adhering to the surface of the counter electrode block.

  Next, as materials for the upper and lower thick plate blocks 250a and 250b and the guide block 240, as long as the withstand voltage can withstand the breakdown electric field strength of 10 kV / cm of the sample fluid (for example, the atmosphere), a plastic that can be easily formed is used. It is also possible to use. In general, it is desirable to use machinable ceramics (grindable ceramic material). It is also possible to use engineering ceramics that sinter after processing such as punching and grinding.

  Whichever material is used, black is baked or painted on the inner wall of the guide block 240 that forms the guiding channel 210e, the inner wall of the specific polarized beam introduction opening 220a, and the scattered light observation opening 220b. It is necessary to reduce the diffusely reflected light in the observation field and in the part through which the polarized beam and scattered light pass by applying a paint having a high light absorption rate. Alternatively, originally black engineering ceramics may be used as the material of the guide block 240 and the thick plate blocks 250a and 250b. As a result, in this embodiment, irregular reflection in the observation field can be reduced, so that even weak scattered light can be detected, and detection and shape identification of small particles having low scattered light intensity, such as particles having a small particle size, can be performed. It becomes possible.

  FIG. 3 is a diagram for explaining the principle of the present embodiment that enables identification of particles having different shapes by detecting scattered light at a specific scattering angle, and shows spherical particles and an infinitely long cylindrical shape. It is a figure which shows the relationship between the polarization degree (polarization magnitude | size) of a scattered light and the particle radius at the scattering angle 10 degree | times close | similar to a forward scattering among the scattered lights by particle | grains. In FIG. 3, S is the characteristic of spherical particles, and C is the characteristic of cylindrical particles.

  FIG. 3 shows the degree of polarization of light scattered by spherical particles and an infinitely long cylindrical particle having a refractive index of 1.55, based on the scattering theory with a scattering angle of 10 degrees for various particle radii. The wavelength of light from which the degree of polarization is derived is 1.55 μm, which is longer than the radius of the identification target particle. In FIG. 3, as the value of the degree of polarization increases in the positive direction, the degree of vertical polarization increases with respect to the scattering plane, and +1 is completely vertical polarization only. On the other hand, as the value of the degree of polarization goes in the negative direction, the degree of horizontal polarization increases with respect to the scattering plane.

FIG. 4 is a diagram for explaining the light scattering phenomenon when a linearly polarized light having a single wavelength is irradiated from the x-axis direction onto a cylinder that is infinitely long in the z-axis direction, and is an arrangement used to derive FIG. FIG. Here, the angle of the polarization plane of linearly polarized light with respect to the normal of the scattering plane is φ. FIG. 4 shows a three-dimensional coordinate system including an incident electric field E ⁽ⁱ⁾ and a scattered electric field E ^(s) with respect to a cylinder when an infinitely long cylinder 100 irradiated with linearly polarized incident light is placed at the origin of the coordinate system. Is shown. FIG. 4 shows the vertical component E _ver ⁽ⁱ⁾ of the incident electric field with respect to the scattering plane 5 (xy plane) including incident light and scattered light, and the parallel (horizontal ⁾ of the vertical component E _ver ^{(s) of the} scattered electric field and the incident electric field. ) The component E _par ^(i), the parallel component E _par ^{(s) of} the scattered electric field, and the scattering angle θ are shown. The linearly polarized light of a single wavelength goes straight along the x axis in the direction of the cylinder 100 at the origin, and is scattered in the cylinder 100. On the scattering plane 5, the angle of the scattered light from the x axis is the scattering angle θ. Define. Scattered light is detected by a detector arranged on an extension line in the direction of the scattering angle θ.

When θ is the scattering angle and φ is the rotation angle of the polarization plane of the incident light with respect to the vertical direction of the scattering plane 5, the electric field component E _ver ^{(i )} , E _ver ^{(s), the} diagonal component of the amplitude scattering matrix T _ver (θ, φ) and the electric field components perpendicular to the axis of the cylinder 100, E _par ⁽ⁱ⁾ , diagonal of the amplitude scattering matrix, for E _par ^(s) Due to the component T _par (θ, φ), the degree of polarization P of the scattered light from the cylindrical particles is a physical quantity defined as follows.
P = (| T _ver | ² − | T _par | ² ) / (| T _ver | ² + | T _par | ² )
= (I _ver -I _par ) / (I _ver + I _par ) (10)

For scattering by spherical particles, T _ver (θ, φ) and T _par (θ, φ) in the calculation formula for the degree of polarization P in equation (10) are respectively the diagonal components S of the amplitude scattering matrix for the sphere. _What is necessary is just to replace with _ver (θ, φ) and S _par (θ, φ).
In the formula _{(10), I ver = |} E ver (s) | 2 is the intensity of the perpendicular scattered electric field the scattering plane 5 (intensity of the vertically polarized light scattered _{light), I par = | E par} (s) | 2 is the scattering The intensity of the scattered electric field parallel to the plane 5 (the intensity of the horizontally polarized scattered light). Since (I _ver + I _par ) is the sum of the vertical polarization component and the horizontal polarization component of the scattered light, it is the total scattered light intensity. (I _ver −I _par ) is an amount representing the difference between the vertical polarization component and the horizontal polarization component when the scattered light is separated into the vertical polarization component and the horizontal polarization component.

According to the light scattering theory, the scattered light intensities I _ver and I _par of the incident light are expressed by the diagonal components S _ver (θ, φ) and S _par (θ, φ) of the spherical scattering particle. If the intensity of the vertical polarization component is I _V0 = | E _ver ⁽ⁱ⁾ | ² , and the intensity of the horizontal polarization component of the incident light is I _P0 = | E _par ⁽ⁱ⁾ | ² , it can be expressed by the following equation.
I _ver = I _V0 [S _ver (θ, φ)] ² / (kr) ² (11a)
I _par = I _P0 [S _par (θ, φ)] ² / (kr) ² (11b)

  Here, when λ is the wavelength of incident light, k is a wave number defined by k = 2π / λ, and r is a distance between a sphere or cylinder as a scatterer and a detector. For concrete formulas of each component S and T of the amplitude scattering matrix, see the electromagnetic scattering document “M. Born and E. Wolf,“ Principles of Optics ”, 2nd edition, 1964, Pergamon, Oxford, Capter XIII, p. .635-664 "," Principle of optics 3 ", 2006, Tokai University Press, Chapter 14 Metal optics, §14.5 Diffraction by conducting sphere: Mie's theory," HCvan de Hulst, "Light Scattering by Small Particles ”, 1957, John Wiley & Sons, New York, Chapter 9, p. 114-130, or“ JD Jackson, Original 3rd Edition, “Electromagnetism (bottom)”, Kei Nishida, 2003, Yoshioka Bookstore, Chapter 10, Scattering and Diffraction, § 10.4 Scattering of electromagnetic waves by a sphere, p.700-707 ”.

By the way, for a cylindrical particle having a finite length d, when the scattered light is observed by a detector sufficiently far away, the distance r from the cylindrical particle to the detector is r >> d ² / λ. Since the condition is satisfied, the diagonal components of the amplitude scattering matrix can be linked to each other in the following relationship.
S _ver (θ, φ) = (kd / π) E (kdφ / 2) T _ver (θ, φ) (12)
Here, E (z) is a spherical Bessel function j ₀ (z) = sin (z) / z. Equation (12) corresponds to the intensity modulation of the scattered light from an infinitely long cylinder with a function representing the Fraunhofer diffraction pattern from a single slit of finite length.
A similar relationship holds between the horizontal polarization component S _par (θ, φ) of the scattered light from the sphere and the horizontal polarization component T _par (θ, φ) of the scattered light from the cylinder.

Therefore, for example, the vertical polarization component of the scattering intensity by the cylindrical particles having a finite length is given by the following equation by substituting equation (12) into equation (11).
I _ver = I _V0 (d / πr) ² · [E (kdφ / 2) · T _ver (θ, φ)] ²
(13)
The same applies to the horizontal polarization component. What is important here is that the length of the cylindrical particles is included in the final expression (13) of the scattering intensity by the cylindrical particles in the form of d ² , that is, a square. This means that the intensity of the scattered light increases with the square of the length of the cylindrical particles.

  By the way, since spherical particles having a large radius or cylindrical particles having a long axial length d cannot float in the air due to gravity sedimentation, the particle radius of the floating particles is often 10 μm or less. Among them, the particles having a radius of 1 μm or less are particularly distributed among the spherical particles, which are distributed in a large number concentration. On the other hand, in the case of fibrous particles such as asbestos, those that are particularly harmful to the human body are those having a diameter of 3 μm or less (length d is 5 μm or more).

  In FIG. 3, when looking at such particles having a radius of 1 μm or less, the polarization state of the scattered light at a scattering angle of 10 degrees is almost non-polarized in the case of spherical particles, while In this case, the vertical polarization component increases. That is, the scattered light from the columnar particles contains a large amount of vertically polarized components whose electric vectors vibrate in the cylinder axis direction. From the difference in the degree of polarization of the scattered light, it is possible to distinguish between spherical particles and cylindrical particles having different shapes. Further, from the intensity of scattered light, the length can be obtained for cylindrical particles, and the radius can be obtained for spherical particles.

  In FIG. 3, since the wavelength of incident light is 1.55 μm, the identifiable particle radius between spherical particles and cylindrical particles is limited to about 1 μm or less, but a light source having a longer wavelength is used. It goes without saying that the radius of the particles that can be identified can be made larger by using them. The characteristics shown in FIG. 3 are facts found by the inventors based on the light scattering theory.

  FIG. 5 is a diagram showing a schematic configuration of the detector 40 of the suspended particulate matter measuring device of the present embodiment. FIG. 5 shows a state in which the specific target particle 1 is irradiated with the specific polarized beam. The flow channel part that constitutes the introduction means for the particles to be detected 1 and the particle orientation means 2 is based on the structure shown in FIGS.

  The main axes of the detection target particles 1 are already aligned in the direction of the normal VER of the scattering plane 5 by the particle orientation unit 2. The particle orientation means 2 is a means for aligning the principal axis of the detection target particle 1 with the normal VER direction of the scattering plane 5 defined by the light source 3, the detection target particle 1, and the polarization beam splitter prism 6. In the embodiment, it is assumed that the flow channel unit 20 shown in FIGS. 1 and 2 includes electrode blocks 230a and 230b and a bipolar DC high-voltage stabilized power source described later.

In the present embodiment, the light emitted from the light source 3 is linearly polarized light whose polarization plane is inclined by 45 degrees with respect to the scattering plane 5. The reason is that when the linearly polarized light emitted from the light source 3 enters the detection target particle 1, the vertical polarization component and the horizontal polarization component have the same intensity.
In addition to linearly polarized light sources such as lasers, non-polarized light sources such as incandescent lamps and light-emitting diodes (Light Emitting Diodes) can be used as light sources with equal vertical and horizontal polarization components. It is. When a non-polarized light source is used, it is necessary to determine the minimum wavelength of incident light by passing light from the light source through a wavelength filter before irradiating the detection target particle 1 with a light beam.

  Moreover, the light source 3 which inject | emits circularly polarized light can also be used instead of a linearly polarized light or a non-polarized light source. In order to emit circularly polarized light, linearly polarized light emitting means such as a gas laser or semiconductor laser diode that emits linearly polarized light, a quarter-wave plate, and a collimating optical system are components of the light source 3. Circularly polarized light is detected by tilting the plane of polarization of linearly polarized light from the linearly polarized light emitting means at 45 degrees with respect to the scattering plane 5, passing this linearly polarized light through a quarter-wave plate, and further transmitting through a collimating optical system. The target particle 1 is irradiated.

  As illustrated in FIG. 3, the present embodiment is not limited to the laser having a wavelength of 1.55 μm, and the present embodiment is also applicable to a case where a laser having another wavelength or an incoherent light source is used. Needless to say, it is obvious that the same effect can be obtained.

  Light emitted from the light source 3 enters the detection target particle 1 from a direction perpendicular to the main axis of the detection target particle 1. When the detection target particle 1 is a cylindrical particle, the incident light includes a component parallel to the cylinder axis (vertical polarization component for the scattering plane 5) and a component perpendicular to the cylinder axis (for the scattering plane 5). The horizontal polarization component is different. Hereinafter, “vertical” and “horizontal” are specified based on the scattering plane 5. Here, attention is focused on scattered light at a certain angle, particularly at a scattering angle θ = approximately 10 degrees close to shallow-angle forward scattering.

As shown in FIG. 5, the scattered light is guided to the polarization beam splitter prism 6 and is divided into a vertical polarization component and a horizontal polarization component at a ratio of 1: 1. The light receiving unit 4a detects the intensity of the divided vertical polarization component, and the light receiving unit 4b detects the intensity of the horizontal polarization component.
The light receiving portions 4a and 4b are elements that convert incident scattered light into an electrical signal, and any one of a photomultiplier tube, an avalanche photodiode, a solid-state junction photodiode, and a semiconductor photodiode can be considered.

  As shown in FIG. 3, the light scattered by the cylindrical particles has many vertically polarized components, whereas the light scattered by the spherical particles is in an unpolarized state. Therefore, when non-polarized light or linearly polarized light or circularly polarized light whose polarization plane is inclined by 45 degrees with respect to the scattering plane 5 is incident on the detection target particle 1, when the detection target particle 1 is a cylindrical particle, the light receiving unit 4 a The detected intensity of the vertically polarized component is greater than the intensity of the horizontally polarized component detected by the light receiving unit 4b. On the other hand, when the detection target particle 1 is a spherical particle, the intensity of the vertical polarization component detected by the light receiving unit 4a and the intensity of the horizontal polarization component detected by the light receiving unit 4b are detected with substantially the same intensity.

  In this way, linearly polarized light, non-polarized light, or circularly polarized light whose polarization plane is inclined by 45 degrees with respect to the scattering plane 5 is irradiated to the particle 1 to be detected, and the intensity of the vertical polarization component and the horizontal polarization component of the scattered light. When the intensity is measured simultaneously, it is possible to identify whether the particle is a spherical particle or a cylindrical particle from the intensity ratio between the vertical polarization component and the horizontal polarization component. The above is the principle of particle shape identification by the suspended particulate matter measuring device of the present embodiment.

  The wavelength of the incident light beam may be longer than the radius of the spherical particle to be identified, but is shorter than the axial length of the cylindrical particle. If the wavelength of the incident light is longer than the axial length d of the cylindrical particles, the cylindrical particles also scatter the same Rayleigh scattering as the spherical particles. The shape identification principle cannot be applied.

That is, the restriction on the light source wavelength λ in shape identification will be described. The wavelength λ (or the minimum wavelength λ _min = λ ₀ −Δ when the wavelength has a finite width ± Δ / 2 from the central value λ _0). / 2) needs to be longer than the radius of the spherical particle or cylindrical particle to be identified. Furthermore, for a cylindrical particle of finite length d, in order to satisfy the condition of r >> d ² / λ assumed when the equation (12) is derived, the wavelength λ (or its maximum wavelength λ _max = Λ ₀ + Δ / 2) must be set shorter than the length d of the cylindrical particles at the same time.

[Second Embodiment]
FIGS. 6A and 6B show electric field vectors when the electrode blocks 230a and 230b are parallel plate shapes in the flow channel unit 20 of the suspended particulate matter measuring device according to the second embodiment of the present invention. It is a figure which shows distribution and force vector distribution. 6A shows an electric field vector distribution generated by two parallel electrode blocks 230a and 230b, and FIG. 6B shows a force vector acting on an electric dipole that is dielectrically polarized in the electric field vector. It is a figure which shows distribution. 6A and 6B show only the right half from the center of the guide channel 210e in the cross section perpendicular to the direction in which the sample fluid flows.

As shown in FIG. 6A, a uniform electrostatic field is formed between the upper and lower electrode blocks 230a and 230b, except for the electrode ends. It can be seen that the detection target particle 1 acts so as to be directed vertically in this uniform electric field. On the other hand, electric lines of force wrap around and concentrate at the ends of the electrode blocks 230a and 230b.
FIG. 6B shows force vectors acting on particles introduced into the electrostatic field between the electrode blocks 230a and 230b. However, even if electrically neutral particles are introduced into the electrostatic field, dielectric polarization immediately occurs due to the strong electrostatic field, and the particles in the electrostatic field become electric dipoles. Then, the particles receive the torque described in the formula (6), rotate in the electrostatic field, and face the electric field application direction.

  In general, an electric force acts on an electric dipole introduced into a non-uniform electric field so as to move the entire dipole. As can be seen from FIG. 6B, since a completely uniform electrostatic field is formed near the center between the electrode blocks 230a and 230b, the force on the electric dipole due to the non-uniform electric field is Absent. On the other hand, the electric field lines wrap around and concentrate at the ends of the electrode blocks 230a and 230b, and the electric field strength is non-uniform. In such a place, the electric dipole attracts the electrode ends. Works strongly.

  In order to avoid the electrode end portion where the electric field is concentrated and to form the conducting channel 210e for guiding the detection target particle 1 to the observation visual field in the uniform electrostatic field, the width of the electrode blocks 230a and 230b is used. Needs to be approximately three times wider than the width of the guide channel 210e. Then, the electrode blocks 230a and 230b are embedded in the countersinks provided in the upper and lower thick plate blocks 250a and 250b, respectively, and the guide block 240 is sandwiched between the thick plate blocks 250a and 250b, thereby forming the guide channel 210e.

  An insulating material is formed on the surface of the electrode blocks 230a and 230b on the conducting channel side (the lower surface in the case of the electrode block 230a, the upper surface in the case of the electrode block 230b), and an insulating film is formed. Alternatively, an insulating metal oxide may be formed on the surfaces of the electrode blocks 230a and 230b. In this way, by forming an insulating film on the surface of the electrode blocks 230a and 230b on the conducting flow path side, the fine particles adhering to the electrode surface are charged with the same polarity as the electrode, repelled by coulomb rebound, and entered the counter electrode side. And it can avoid adhering to a counter electrode surface.

  An electrostatic field with an electric field strength of about 1 kV / cm to 5 kV / cm is generated by applying positive and negative voltages to the two opposing electrode blocks 230a and 230b from a later-described bipolar type DC high-voltage power supply. When the detection target particle 1 is introduced into such an electric field, the detection target particle 1 that is electrically neutral is immediately dielectrically polarized by the high piezoelectric field. When the particle 1 to be detected is a spherical particle, the axis of the particle is not rotated even by dielectric polarization.

  On the other hand, when the particle 1 to be detected is fibrous, the positive and negative charges generated by dielectric polarization are attracted to the negative electrode and the positive electrode, respectively. As a result, the particle 1 to be detected becomes a cylindrical particle. A rotational moment force (see equation (6)) acts so that the axis of rotation is deformed and the axis of rotational symmetry is directed in the direction of the electric force line. As a result, the fibrous particles 1 to be detected are stretched and deformed into columnar particles, and their axes are aligned in the direction of the applied electrostatic field.

  If the parallel plate-shaped electrode blocks 230a and 230b are configured to separate the flow path 210e of the flow channel portion 20 from the electrode end, the influence of the non-uniform electric field due to the concentration of the electric lines of force at the electrode end portion becomes small. In this case, the particles that cause the introduced particles 1 to be detected to dissipate away from the center of the channel do not act. That is, in this configuration, it can be said that the detection target particles 1 in the observation region of the guide channel 210e are distributed almost uniformly in the sample fluid in a state of being directed in the electric field application direction. Therefore, the uniformity of the space, which is the premise of counting when deriving Equation (3), is ensured.

[Third Embodiment]
7 (A), 7 (B), and 7 (C) are cross-sectional views of the end portions of the electrode blocks 230a and 230b in the flow channel unit 20 of the suspended particulate matter measuring device according to the third embodiment of the present invention. It is a figure which shows an equipotential line, an electric force line, electric field vector distribution, and force vector distribution at the time of making a shape into a Rogowski end part shape. 7A shows equipotential lines and electric lines of force at the end of the parallel plate capacitor, FIG. 7B shows electric field vector distribution generated by the electrode blocks 230a and 230b, and FIG. B) is a diagram showing a force vector distribution acting on an electric dipole that is dielectrically polarized in the electric field vector. 7A to 7C show only the right half from the center of the guide channel 210e in the cross section perpendicular to the direction in which the sample fluid flows.

  As shown in the second embodiment, the parallel plate-shaped electrode blocks 230a and 230b have electrode shapes that are most suitable for forming a uniform electric field. However, since the parallel plate-shaped electrode blocks 230a and 230b have a finite size, concentration of electric lines of force (end effect) occurs at the ends. That is, the electrostatic field for grain orientation formed by the parallel flat plate-shaped electrode blocks 230a and 230b having a finite width causes the maximum electric field stress at the electrode end, so that a discharge is always generated at the electrode end when a high voltage is applied. There is a risk of occurrence.

  Therefore, there is a need for an electrode surface structure that can relax the electric field strength in the end region and form an equal strong electric field over the entire electrode surface having a finite width. That is, it is necessary to obtain an electrode surface shape in which the electric field stress is alleviated to a level equal to or less than the electric field stress in the central portion where the electric field stress is sufficiently far from the end portion and has a uniform electric field strength over all electrode end regions. In order to prevent this end effect, an electrode shape with rounded electrode ends has been developed, and the electrode having this shape is referred to as a Rogowski electrode.

  FIG. 7A is a diagram showing an equipotential line 231 (solid line) and an electric force line 232 (dotted line) in the case where the end portion of a parallel plate capacitor having a finite width is included. In FIG. 7A, a thick line 233 indicates an equipotential line having an interval of a / n where n is an integer when the interval of the parallel plate capacitors is a (in FIG. 7A). n = 3).

According to electromagnetism, equipotential lines and electric lines of force are orthogonal to each other, and no electric force acting in the tangential direction is generated along the equipotential lines. Therefore, if the curved surface of this equipotential surface is adopted as the electrode shape, in principle, the electric field stress generated at the end of the parallel plate electrode can be avoided, and the electric field stress is slightly stronger at the center than at the end. If designed so, a non-uniform electric field in which the electric field strength increases extremely gently from the end toward the center can be formed.
The Rogowski end-shaped electrode was designed based on this concept. Then, the Rogowski end-shaped electrode blocks 230a and 230b are derived from a two-dimensional electric field, and become hook-shaped electrode blocks extending in the depth direction.

  The detection target particles 1 dispersed in the sample fluid are introduced into the flow channel portion 20 from the fluid inlet 21a, flow through the guide channel 210e, and are crossed by the electrode blocks 230a and 230b having a Rogowski end shape. Guided to the electric field formed. As shown in FIG. 7 (B), the minute neutral fibrous target particle 1 guided into the electric field instantaneously undergoes dielectric polarization, and of both ends of the particle 1, the positive electrode of the external electrostatic field. One end close to is charged to the negative electrode, and the other end close to the negative electrode of the external electrostatic field is charged to the positive electrode. And the to-be-detected target particle | grains 1 face an electric field direction, deform | transforming into a cylindrical particle.

  Then, with respect to the electric dipole thus dielectrically polarized, between the Rogowski end-shaped electrode blocks 230a and 230b, as shown in FIG. 7 (C), it gradually concentrates from the electrode end toward the center. Electric force to act acts. In FIG. 7C, in order to show the direction of the force vector, an arrow is emphasized, but the strength is extremely weak. Nevertheless, a force vector field is formed that concentrates in the center.

  As described in the first embodiment, such a Rogowski end electrode block 230a, 230b may be formed by cutting out a metal block having high plasticity such as copper, It may be configured by molding into a shape, or it may be configured to give a function as a metal electrode by plating or directly depositing metal on the surface of the guide channel of a material such as plastic that is easy to mold Also good. The material is not limited to metal or the like as long as the material can realize an electrode having a desired cross-sectional shape with required processing accuracy. This is because it is only necessary to apply a high voltage to the electrode blocks 230a and 230b so that the direction of the particles 1 to be detected is aligned. It is because it does not flow.

  As in the first embodiment, an insulating film is formed as a protective film for the metal layer on the surface of the electrode blocks 230a and 230b on the side of the conducting flow path. Alternatively, an insulating metal oxide may be formed on the surfaces of the electrode blocks 230a and 230b. Thus, it goes without saying that it is possible to avoid the fine particles adhering to the electrode surface from being charged with the same polarity as the electrode, repelling the Coulomb and re-scattering, entering the counter electrode block and adhering to the surface of the counter electrode block.

By the way, for the Rogowski end shape, while calculating the coordinate value using a numerically controlled machine tool etc., if the material is plastic, mold it, and if the material is a metal lump, cut it out and mold it Become.
Specifically, by using the equiangular mapping method from the complex plane z = x + ii to the Gaussian plane ω = u + iv, where i is an imaginary unit, the plate interval a = π is set, and the end is v = π / 2 (in this case, the integer n is divided by an equipotential surface of n = 2), the Maxwell equation given by the following equation (14) is separated into a real part and an imaginary part, and u is If the values of x and y are obtained as parameters, the required equipotential lines (= Rogowski end shape) can be obtained.

z = (a / π) (ω + 1 + exp (ω)) (14)
x = u + 1 (15a)
y = π / 2 + exp (u) (15b)
Thus, the calculated values as shown in Table 1 are obtained. The value y in Table 1 is rounded to two decimal places.

  When the distance between the flat plates is a, if the calculation is terminated at the coordinates of u = 1, an end having a width of about 2a is required. For such an end electrode shape, when a high voltage is applied, the discharge is always expected to occur in the uniform electric field part (that is, the central part of the electrode), and the electric field gradually increases from the end part toward the central part. An electrostatic field with increasing intensity is realized. Therefore, it is possible to realize an electrostatic field that converges the dielectric-polarized electric dipole to the central portion.

[Fourth Embodiment]
8 (A) and 8 (B) are planes in which the electrode blocks 230a and 230b are orthogonal to the guide channel 210e in the flow channel unit 20 of the suspended particulate matter measuring device according to the fourth embodiment of the present invention. It is a figure which shows the electric field vector distribution and force vector distribution in case the conducting-channel side surface curve when cut is a hyperbola. 8A shows the electric field vector distribution generated by the electrode blocks 230a and 230b, and FIG. 8B shows the force vector distribution acting on the electric dipole that is dielectrically polarized in the electric field vector. is there. 8A and 8B show cross sections perpendicular to the direction in which the sample fluid flows.

  The particles 1 to be detected dispersed in the sample fluid are introduced into the flow channel portion 20 from the fluid inlet 21a, flow through the guide channel 210e, and electrode blocks 230a and 230b whose guide channel side surface curves are hyperbolic. To the electric field formed by As shown in FIG. 8 (A), the minute neutral fibrous target particle 1 guided in the non-uniform electric field instantaneously undergoes dielectric polarization, and an external electrostatic field is detected at both ends of the particle 1. One end close to the positive electrode is charged to the negative electrode, and the other end close to the negative electrode of the external electrostatic field is charged to the positive electrode.

  In addition, the electrostatic field formed between the electrode blocks 230a and 230b having a hyperbolic curve on the surface of the conducting channel side gradually decreases in electric field strength from the central part toward the left and right outer wall parts. As shown in FIG. 8B, the introduced electric dipole is subjected to a force that converges to a central position where the electric field strength is strong in the horizontal direction. As a result, the detection target particle 1 introduced into the electrostatic field formed by the electrode blocks 230a and 230b does not move to the left and right, and faces a specific direction, that is, the electrostatic field application direction at the center position where the electric field strength is strong. And stable. While the induced charge generated by dielectric polarization is equal at both ends, the electrostatic force acting on the particle end closer to the electrode is slightly larger, so the electric dipole moves in the direction of the electrode, that is, in the vertical direction. As for the movement to, an attractive force in the electrode direction is generated. However, the detection target particles 1 are transported in the direction of the observation field along the vicinity of the center position in the direction of the fluid exhaust port 21b while maintaining a relatively stable orientation.

By the way, if the electric dipole guided to the guiding channel 210e once deviates from the central portion of the observation field due to slight disturbance of the sample fluid in a laminar flow state (for example, the influence of turbulent flow), In a steady state, suction is performed to one of the upper and lower electrode blocks 230a and 230b.
In this case, by using a cylindrical concave / convex lens, the observation field area is expanded in the vertical direction by forming the polarized beam cross-sectional shape into a linearly expanded beam extending in the vertical direction, and the laser irradiation area is detected. It is relatively easy to make the target particles 1 exist. However, for lenses, it is necessary to examine the materials (impurities, distortion, homogeneity) so as not to affect the coherence of light.

  In the present embodiment, when the particles 1 to be detected polarized by the electrostatic field are directed in the direction of applying the electrostatic field, the particles 1 are steadily concentrated and converged in the observation field of view, and further, the particles 1 are uniformly distributed. By statistically counting a little more, statistical fluctuation with respect to the count value can be reduced.

[Fifth Embodiment]
9 (A) and 9 (B) are planes in which the electrode blocks 230a and 230b are orthogonal to the guide channel 210e in the flow channel unit 20 of the suspended particulate matter measuring device according to the fifth embodiment of the present invention. It is a figure which shows the electric field vector distribution and force vector distribution in case the conducting-channel side surface curve when cut is a V-shaped curve and a reverse V-shaped curve. 9A is a diagram showing an electric field vector distribution generated by the electrode blocks 230a and 230b, and FIG. 9B is a diagram showing a force vector distribution acting on an electric dipole that is dielectrically polarized in the electric field vector. is there. 9A and 9B show cross sections perpendicular to the direction in which the sample fluid flows.

  Similar to the first to fourth embodiments, the detection target particles 1 dispersed in the sample fluid are introduced into the flow channel unit 20 from the fluid inlet 21a, flow in the guide channel 210e, The guide channel side surface curve is led to an electric field formed by the electrode blocks 230a and 230b having a V-shaped curve and an inverted V-shaped curve. However, unlike the previous embodiments, in this embodiment, the electrode surface is not a smooth curved surface but has a ridge portion (V-shaped apex) bent at a certain angle. A strong electric field is generated along such a ridge line from the near side to the far side of the paper surface of FIGS. 9 (A) and 9 (B). Between the opposing ridges of the electrode blocks 230a and 230b, there is a problem that dielectric breakdown of the sample fluid is likely to occur even at a relatively low voltage. Therefore, it is necessary to round the V-shaped and inverted V-shaped vertices into a circle. In the present embodiment, the shapes obtained by rounding the vertices of the V shape and the inverted V shape are referred to as a V-shaped curve and an inverted V-shaped curve.

  As shown in FIG. 9 (A), an inhomogeneous electric field is formed around this ridge line, and the electric dipole introduced into the ridge line has a horizontal direction as shown in FIG. 9 (B). The force vector acts so as to converge to the center position that is the specific polarized beam irradiation region. That is, in the electrostatic field generated by the electrode blocks 230a and 230b having the V-shaped curve and the inverted V-shaped curve on the surface of the conducting channel, the electric field is concentrated and strengthened along the ridge line of the electrode. The electric dipole receives the power converged to the ridge line.

  When the electrode blocks 230a and 230b having the V-shaped cross section are used, the voltage to be applied must be lowered to avoid the dielectric breakdown of the sample fluid, but the detection target particle 1 is a laser irradiation region. This has the effect of concentrating on the center of the flow channel section 20. Conversely, it can be said that an electrode having an effect of concentrating the particles 1 to be detected that are dielectrically polarized on the central portion of the flow channel portion 20 can be realized by a voltage lower than the dielectric breakdown voltage of the sample fluid.

However, in the electrode direction, that is, the vertical direction, a stronger non-uniform electric field is formed as compared with the fourth embodiment, so that a strong attractive force acts on the electric dipole. For this reason, in the vertical direction, the particles 1 to be detected tend to split in the vertical direction due to disturbance.
Also in this case, similarly to the fourth embodiment, by using a cylindrical plano-concave lens, the observation visual field region is formed in the vertical direction by forming a cross-sectional shape of the polarized beam into a linearly expanded beam extending in the vertical direction. The detection target particle 1 can be configured to exist in the laser irradiation region.

[Sixth Embodiment]
FIG. 10 is a block diagram showing the configuration of the signal processing system of the suspended particulate matter measuring device according to the sixth embodiment of the present invention. FIG. 10 is a diagram for explaining a signal processing system applied to the first to fifth embodiments.
The signal processing system of the present embodiment that performs particle shape identification includes signal amplification units 7a and 7b, a differential amplification unit 8, a particle shape identification unit 9, a pulse height analysis unit 10, a calculation control unit 11, and communication. Part 13 and addition part 14. This signal processing system constitutes particle identification means.

  The differential amplification unit 8 and the particle shape identification unit 9 realize a particle shape identification function, and the calculation control unit 11 performs counting for each particle shape. Thereby, the number of particles in the observation field or the number of particles in the unit counting time can be obtained. At the same time, the wave height analysis unit 10 calculates the particle size or length of the detection target particle 1 based on the wave height analysis result of the detection pulse signal, and the arithmetic control unit 11 counts the signal pulses that are equal to or higher than the wave height threshold, thereby detecting Count the number of particles per particle size or length.

Based on FIG. 10, the flow of particle detection, shape identification, particle size calculation and counting will be described. First, the arithmetic control unit 11 drives the bipolar DC high-voltage stabilization power supply 12 to generate an electrostatic field for particle orientation in the particle orientation means 2 of the detector 40 described in the first to fifth embodiments. Thus, the direction of the detection target particles 1 is aligned in the vertical direction with respect to the scattering plane 5.
As shown in FIG. 5, the direction of the particle 1 to be detected is aligned with the direction of the normal VER of the scattering plane 5 by the particle orientation means 2 of the flow channel unit 20, and the linearly polarized beam from the light source 3 is detected. Irradiate.

  When the detection target particle 1 crosses the observation field, shallow angle forward scattered light having a scattering angle θ = approximately 10 degrees enters the polarization beam splitter prism 6, and the polarization plane is perpendicular to the scattering plane 5. The light is divided into a vertical polarization component and a horizontal polarization component horizontal to the scattering plane 5. The light receiving units 4a and 4b detect the vertically polarized component and the horizontally polarized component of the scattered light with the scattering angle θ = approximately 10 degrees, and convert them into weak current pulses. The signal amplifying units 7a and 7b connected to the light receiving units 4a and 4b convert the weak current pulses output from the light receiving units 4a and 4b into voltage pulses and amplify them.

The differential amplifying unit 8 amplifies the difference between the weakly polarized current pulses of the vertical polarization component and the horizontal polarization component detected by the two light receiving units 4a and 4b, and simultaneously converts them into voltage pulses, which are output to the particle shape identification unit 9. To do.
When the voltage pulse intensities of the vertical polarization component and the horizontal polarization component are approximately equal (when the output of the differential amplification unit 8 is approximately 0), the particle shape identification unit 9 determines that the detection target particle 1 is a spherical particle. When the voltage pulse intensity of the vertical polarization component is larger than the horizontal polarization component, it is identified that the detection target particle 1 is a cylindrical particle.

Further, the adding unit 14 obtains a voltage pulse of scattered light by taking the sum of the vertical polarization component and the horizontal polarization component detected simultaneously by the two light receiving units 4a and 4b.
The pulse height analysis unit 10 sorts the voltage pulse according to the peak value by comparing the peak value of the voltage pulse of the scattered light with several predetermined threshold voltages. And the calculation control part 11 counts a pulse for every kind of classified pulse. Thus, it is possible to obtain the spherical particle equivalent diameter or the columnar particle equivalent length of the detection target particle 1 from the peak value of the separated pulse, and the number of detection target particles 1 is determined for each pulse peak value range. (That is, it can be counted for each particle diameter or for the length of each columnar particle).

In this way, by combining the discrimination result by the particle shape identification unit 9 and the count result for each wave height by the wave height analysis unit 10, the particle diameter is calculated for spherical equivalent particles, and the columnar equivalent is also obtained. For particles, the length is calculated and the count value of each particle is calculated.
The discrimination result by the particle shape identification unit 9, the classification result by the particle size or length by the wave height analysis unit 10, and the count result of each pulse by the calculation control unit 11 are not shown in the built-in memory (not shown) of the calculation control unit 11. ). The information stored in the built-in memory is transmitted to the outside of the device via the communication unit 13, and is also transmitted to and displayed on a display unit (not shown) mounted on the device.

  The particle shape identification unit 9, the wave height analysis unit 10, and the calculation control unit 11 of the present embodiment manage, for example, a central processing unit (CPU), a computer including a memory and an interface, and hardware resources thereof. It can be realized by a program to be controlled. The CPU executes the processing described in this embodiment in accordance with the signal processing program stored in the storage device.

  The present invention can be applied to a technique for identifying the shape of fine particles floating in a fluid such as air.

It is a perspective view which shows the structure of the flow channel part of the suspended particulate matter measuring device which concerns on the 1st Embodiment of this invention. It is a disassembled perspective view which shows the structure of the flow channel part of the suspended particulate matter measuring device which concerns on the 1st Embodiment of this invention. It is a figure which shows the relationship between the polarization degree of the scattered light at a scattering angle of 10 degree | times, and a particle radius among the scattered light by the spherical particle | grains and cylindrical particle | grains with respect to incident light with a wavelength of 1.55 micrometers. It is a figure which shows the definition of the perpendicular | vertical component and parallel component with respect to the scattering plane of an incident electric field and a scattered electric field, and the definition of the scattering angle with respect to the infinite cylinder irradiated from a normal direction, and the rotation angle of a polarization plane. It is a figure which shows schematic structure of the detector of the suspended particulate matter measuring device which concerns on the 1st Embodiment of this invention. It is a figure which shows the force vector distribution which acts on the electric field vector distribution by two parallel electrode blocks, and the dielectrically polarized electric dipole in the suspended particulate matter measuring device which concerns on the 2nd Embodiment of this invention. The figure which shows the equipotential lines and electric lines of force of a parallel plate capacitor end part, and made the cross-sectional shape of an electrode block into the Rogowski end part shape in the suspended particulate matter measuring device which concerns on the 3rd Embodiment of this invention. It is a figure which shows the electric field vector distribution and force vector distribution in a case. It is a figure which shows the force vector distribution which acts on the electric field vector distribution by the electrode block of the conducting-path side surface curve with a hyperbola, and the dielectrically polarized electric dipole in the suspended particulate matter measuring device which concerns on the 4th Embodiment of this invention. . In the suspended particulate matter measuring apparatus according to the fifth embodiment of the present invention, the surface curve on the conduction channel side acts on the electric field vector distribution and the dielectrically polarized electric dipole by the electrode block having the V-shaped curve and the inverted V-shaped curve. It is a figure which shows force vector distribution to do. It is a block diagram which shows the structure of the signal processing system of the suspended particulate matter measuring device which concerns on the 6th Embodiment of this invention. It is a schematic diagram of a conventional rotating electric field type suspended particulate matter measuring device. It is an optical measurement system layout diagram of a rotating electric field and scattered light in a conventional rotating electric field type suspended particulate matter measuring device. It is the top view and side view of the conventional electrostatic field type suspended particulate matter measuring device. Particle extension by uniform electric field, rotation of electric dipole by electric field torque, orientation of electric dipole in electric field direction, force acting on electric dipole by inhomogeneous electric field, and deviation of particle from observation field region It is a figure which shows a mode. It is a figure showing the electric field vector distribution by the quadruple electrode formed around the cylindrical flow tube, and the force vector distribution acting on the dielectrically polarized electric dipole. It is a figure showing the electric field vector distribution by the counter electrode formed around the cylindrical flow tube, and the force vector distribution acting on the dielectrically polarized electric dipole.

Explanation of symbols

 DESCRIPTION OF SYMBOLS 1 ... Particle to be detected, 2 ... Particle orientation means, 3 ... Light source, 4a, 4b ... Light receiving part, 5 ... Scattering plane, 6 ... Polarizing beam splitter prism, 7a, 7b ... Signal amplification part, 8 ... Differential amplification , 9 ... Particle shape identification unit, 10 ... Pulse height analysis unit, 11 ... Calculation control unit, 12 ... High voltage stabilized power supply, 13 ... Communication unit, 14 ... Addition unit, 20 ... Flow channel unit, 21a ... Fluid intake port, 21b ... Fluid exhaust port, 210c ... Intake joint, 210d ... Exhaust joint, 210e ... Guide channel, 220a ... Specific polarized beam introduction opening, 220b ... Scattered light observation aperture, 220c ... Guide channel sealing Glass window, 230a, 230b ... electrode block, 240 ... guide block, 250a ... upper thick plate block, 250b ... lower thick plate block, 260a, 260b ... contact electrode terminal, 270 ... fixing screw hole, 280 Fixing block, 40 ... detector.

Claims (13)

A light source that emits a polarized beam;
Introducing means for introducing the particles to be detected suspended in the fluid into the observation field in a laminar flow state by the sample fluid channel;
Of the scattered light resulting from the incidence of the polarized beam from the light source on the particle introduced into the observation field, the scattering angle centered on the particle with respect to the direction from the light source toward the particle is approximately 10 degrees. A polarization beam splitter prism that divides the scattered light into two light beams whose polarization directions are orthogonal to each other;
A particle orientation means for directing the particles in a normal direction of the scattering plane with respect to a scattering plane including the light source, the particles, and the polarization beam splitter prism before the light beam is incident on the particles;
First and second light receiving means for converting the two light beams split by the polarizing beam splitter prism into electrical signals, respectively;
Particle identifying means for identifying the particle shape based on signals output from the first and second light receiving means,
The particle orientation means is composed of two electrode blocks arranged along the sample fluid channel, and forms an electrostatic field between the electrode blocks in the normal direction of the scattering plane,
The two electrode blocks are in the form of floating particles characterized in that the guide channel side surfaces are flat and parallel to each other, or the guide channel side surfaces are curved and face each other toward the opposing electrode blocks. Substance measuring device. In the suspended particulate matter measuring device according to claim 1,
The two electrode blocks have a parallel plate shape whose width in the direction perpendicular to the sample fluid guide channel is wider than the width of the sample fluid guide channel, and the observation is performed by applying a voltage between the two electrode blocks. An apparatus for measuring suspended particulate matter, characterized in that a uniform electrostatic field is formed in a sample fluid guide channel covering a visual field. In the suspended particulate matter measuring device according to claim 1,
The two electrode blocks have a rectangular longitudinal cross-section along the sample fluid guide channel, and an end shape of a cross section perpendicular to the sample fluid guide channel is a Rogowski type end shape. An apparatus for measuring suspended particulate matter, wherein an electrostatic field in which an electric field strength gradually increases toward a central portion is formed in a sample fluid guide channel covering the observation field by applying a voltage between electrode blocks. In the suspended particulate matter measuring device according to claim 1,
The two electrode blocks have a rectangular longitudinal cross-section along the sample fluid guide channel, and the guide channel side surface curve when cut along a plane orthogonal to the sample fluid guide channel is a hyperbola. An apparatus for measuring suspended particulate matter, wherein an electrostatic field in which an electric field strength gradually increases toward a central portion is formed in a sample fluid guide channel covering the observation field by applying a voltage between two electrode blocks. In the suspended particulate matter measuring device according to claim 1,
The two electrode blocks have a rectangular longitudinal cross-section along the sample fluid channel, and the surface curve on the channel side when cut along a plane orthogonal to the sample fluid channel is opposite to the V-shaped curve. It is a V-shaped curve, and an electrostatic field in which the electric field strength gradually increases toward the center is formed in the sample fluid guide channel covering the observation visual field by applying a voltage between the two electrode blocks. Airborne particulate matter measurement device. In the suspended particulate matter measuring device according to any one of claims 1 to 5,
The introducing means includes
It consists of two guide blocks made of an insulating material and two thick plate blocks made of an insulating material sandwiching the two guide blocks from above and below,
The two guide blocks have an opening for introducing the polarized beam and the scattered light at a position away from an end surface serving as a sample fluid inlet by a distance necessary for the fluid to develop into a laminar flow state. And an opening for observation, and an optical glass plate is fitted in each opening,
The electrode blocks are arranged between the upper thick plate block and the two guide blocks and between the lower thick plate block and the two guide blocks, respectively. And a region between the two guide blocks as the sample fluid guide channel. In the suspended particulate matter measuring device according to claim 1,
The electrode block is made of any one of a metal material containing at least one of copper, gold, platinum, silver, or aluminum, plastic, machinable ceramics, or engineering ceramics,
When the plastic is used, the suspended particulate matter measuring device is characterized in that the electrode block is formed by metal plating or metal vapor deposition on the surface of the guide channel. In the suspended particulate matter measuring device according to claim 7,
An apparatus for measuring suspended particulate matter, wherein an insulating film is formed on a surface of the electrode block on the side of the conducting channel. The suspended particulate matter measuring device according to claim 6,
The guide block and the thick plate block are made of plastic, machinable ceramics, or engineering ceramics,
The suspended particulate matter measuring device, wherein a wall surface of the observation field of view and a wall surface of the opening are coated with a material that absorbs light having a wavelength of the light source. The suspended particulate matter measuring device according to claim 6,
The apparatus for measuring suspended particulate matter, wherein the optical glass plate is made of a material that is non-reflective at the wavelength of light of the polarized beam. In the suspended particulate matter measuring device according to claim 1,
The light source emits a non-polarized light beam, or emits a linearly polarized light plane as a linearly polarized beam inclined by 45 degrees with respect to the normal direction of the scattering plane, or linearly polarized light by 1/4. The light beam is emitted by either passing through the wave plate and being emitted as a circularly polarized beam, and the minimum value of the wavelength of this light beam is longer than the radius of the spherical microparticle to be identified and is cylindrical. A suspended particulate matter measuring apparatus characterized by being shorter than the length of a minute particle. In the suspended particulate matter measuring device according to claim 1,
The particle discriminating means determines that if the intensity difference is substantially equal from the difference in intensity between the vertically polarized light component detected by the first light receiving means and the horizontally polarized light component detected by the second light receiving means, An apparatus for measuring suspended particulate matter, characterized in that it is identified as a spherical particle, and the particle is identified as a columnar particle when the difference in intensity shows the predominance of a vertically polarized component. In the suspended particulate matter measuring device according to claim 12,
The particle identification means compares the voltage pulse height given by the sum of the respective polarization components simultaneously detected by the first and second light receiving means with a plurality of predetermined threshold voltages to thereby obtain the voltage The pulse is classified according to its peak value, and counted for each of the sorted pulses, and based on the identification result of the particle, when the particle is identified as a spherical particle, the particle radius is determined based on the pulse peak value, When the particle is identified as a cylindrical particle, the suspended particulate matter measuring device is characterized in that the particle length is obtained based on the pulse peak value.

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