JP3123009U - Laser diffraction / scattering particle size distribution analyzer - Google Patents

Abstract

Laser diffraction / scattering particle size distribution measurement that does not cause under-ghosting or upper-ghosting in the measurement results of a group of particles to be measured with a monodisperse steep distribution, and can clearly evaluate the presence of aggregates Providing the device.
When a first bottom B1 is present in the spatial intensity distribution of diffracted / scattered light by a group of particles to be measured measured by a measuring optical system (3,4,5,6), a small angle side To the first bottom B1 is used to calculate the particle size distribution using the spatial intensity distribution data of the diffracted / scattered light.
[Selection] Figure 1

Description

  The present invention relates to a laser diffraction / scattering type particle size distribution measuring apparatus, and more particularly to a laser diffraction / scattering type particle size distribution measuring apparatus capable of accurately measuring the particle size distribution of monodisperse particles.

  Laser diffraction / scattering particle size distribution analyzers generally measure the spatial intensity distribution of diffracted / scattered light generated by irradiating a group of particles in a dispersed state with laser light. Based on the theory or the diffraction theory of Fraunhofer, the particle size distribution of the particle group to be measured is calculated from the measurement result of the spatial intensity distribution of the diffracted / scattered light by the calculation based on the Mie scattering theory or the Fraunhofer diffraction theory.

  In this type of measuring apparatus, the one schematically shown in FIG. 3 is frequently used as an optical system for measuring the spatial intensity of diffracted / scattered light by the group of particles to be measured (see, for example, Patent Document 1). .

  That is, the particle group P to be measured is caused to flow in, for example, a flow cell in the form of a suspension dispersed in a liquid medium, and the laser light source 32a and the collimator lens 32b are measured with respect to the particle group P in the dispersed state. A parallel laser beam is emitted from an irradiation optical system 32 composed of the same. This laser light is diffracted and scattered by the measurement target particle group P in a dispersed state, and a spatial light intensity distribution pattern is generated. Among the diffracted / scattered light, light having a diffracted / scattered angle within a predetermined forward angle is collected by the condensing lens 33 and a diffracted / scattered image is formed on the ring detector 34 placed at the focal position. The ring detector 34 is formed by arranging dozens of light receiving elements having ring-shaped, semi-ring shaped or quarter-ring shaped light receiving surfaces having different radii from each other in a concentric manner with the optical axis of the irradiated laser light as the center. In addition, the intensity of the diffracted / scattered light collected by the condenser lens 33 can be continuously measured for each minute angle. Further, the side scattered light and the back scattered light that are not collected by the condenser lens 33 are detected by the side scattered light sensor 35 and the back scattered light sensor 36 each composed of a single sensor.

  The spatial intensity distribution pattern of the diffracted / scattered light measured in this way is digitized by an A / D converter and taken into a computer as scattered light intensity distribution data, and the measured particle group P is measured according to the principle described below. It is converted into a particle size distribution.

  The intensity distribution data of scattered light from the particle group P to be measured varies depending on the size of the particles. Since particles having different sizes are mixed in the actual particle group P to be measured, the intensity distribution data of the scattered light generated from the particle group P is an overlay of the scattered light from the respective particles. If this is expressed in a matrix,

となる。ただし、

It becomes. However,

である。

It is.

In the above equations, s (vector) is intensity distribution data (vector) of scattered light. The element s _i (i = 1, 2,... M) is the amount of incident light detected by each element and side of the ring detector 34 and the backscattered light sensors 35 and 36.

q (vector) is particle size distribution data (vector) expressed as a frequency distribution%. A particle diameter range (maximum particle diameter; x ₁ , minimum particle diameter; x _{n + 1} ) to be measured is divided into n, and each particle diameter section is [x _j , x _{j + 1} ] (j = 1, 2). ,... N). The element q _j (j = 1, 2,... n) of q (vector) is a particle corresponding to the particle diameter section [x _j , x _{j + 1} ] (j = 1, 2,... n). It is a quantity.
Usually a volume basis is used,

となるように、つまり合計が１００％となるように正規化（ノルマライズ）を行っている。

In other words, normalization (normalization) is performed so that the total becomes 100%.

A (matrix) is a coefficient matrix for converting the particle size distribution data (vector) q into light intensity distribution data (vector) s. The physical meaning of the element a _{i, j} (i = 1, 2,... M, j = 1, 2,... N) of A (matrix) is the particle interval [x _j , x _{j + 1} ]. Is the amount of light incident on the i-th element of light scattered by a particle group having a unit particle amount belonging to.

The numerical value of a _{i, j} can be theoretically calculated in advance. For this, the Fraunhofer diffraction theory is used when the particle diameter is sufficiently larger than the wavelength of the laser beam serving as the light source (10 times or more). However, it is necessary to use the Mie scattering theory in a region where the particle diameter is the same as or smaller than the wavelength of the laser beam. The Fraunhofer diffraction theory can be considered to be an excellent approximation of the Mie scattering theory that is effective when the particle diameter is sufficiently larger than the wavelength in forward small angle scattering.

  In order to calculate the elements of the coefficient matrix A (matrix) using the Mie scattering theory, it is necessary to set the absolute refractive index (complex number) of the particles and the medium (liquid medium) in which the particles are dispersed.

  Now, when deriving an equation for obtaining a least square solution of the particle size distribution data (vector) q based on the equation (1),

が得られる。

Is obtained.

  The angular element of the light intensity distribution (vector) s on the right side of the equation (5) is a numerical value detected by the ring detector and the side and backscattered light sensors as described above. The coefficient matrix (matrix) A can be calculated in advance using Fraunhofer diffraction theory or Mie scattering theory. Therefore, if the calculation of equation (5) is executed using these known data, the particle size distribution data (vector) q is obtained.

This equation (5) is a basic method for calculating the particle size distribution from the light intensity distribution data in the laser diffraction / scattering method. However, if this expression is executed as it is, a considerably large error is generated. Therefore, the calculation actually executed on the computer is complicated considering various conditions. For example, the calculation is performed with a constraint that the amount of particles does not become a negative value or the particle size distribution is continuous to some extent. In addition, selecting the refractive index when measuring or recalculating the particle size distribution actually selects the coefficient matrix A (matrix) calculated using the refractive index.
JP 7-260669 A

  In the laser diffraction / scattering type particle size distribution measuring apparatus as described above, conventionally, a graph showing the measurement result of the light intensity distribution is shown in FIG. 4, and the sensor element number (in other words, the diffraction / scattering angle) is shown on the horizontal axis. As shown by taking the intensity of diffracted / scattered light on the vertical axis, the particle size distribution is calculated using all the light intensity distribution data at an angle larger than the scattering angle at which the light intensity exceeds a preset threshold value. Calculated. In this graph, the detection result by each element of the ring detector is shown in the large rectangle on the left side, and the side scattered light sensor and the back scattered light are shown in the small rectangle on the right side. It is a detection result by a sensor.

  By the way, in a monodisperse measured particle group having a steep distribution, an under ghost or an upper ghost appears as shown in FIG. There is a case.

  Conversely, as illustrated in FIG. 6, when a part of a monodisperse sample having a steep distribution is agglomerated although it is a minute amount, when it is desired to evaluate the agglomerate, a conventional method is used. Could not be confirmed, or could not be distinguished from the upper ghost.

  The present invention has been made in view of such circumstances, and under-ghosts and upper ghosts do not occur in the measurement results of the measured particle groups having a monodisperse steep distribution. It is an object of the present invention to provide a laser diffraction / scattering particle size distribution measuring apparatus that can clearly evaluate the presence of aggregates.

  In order to solve the above problems, a laser diffraction / scattering type particle size distribution measuring device according to claim 1 is directed to an irradiation optical system for irradiating a group of particles to be measured in a dispersed state with parallel laser light, and irradiation with the laser light. Laser diffraction / scattering type equipped with a measurement optical system that measures the spatial intensity distribution of diffracted / scattered light generated by the laser and an arithmetic means for calculating the particle size distribution of the particles to be measured using the spatial intensity distribution of the diffracted / scattered light The particle size distribution measuring apparatus has a bottom detecting means for detecting the first bottom from the smaller diffraction / scattering angle in the spatial intensity distribution of the diffracted / scattered light measured by the measurement optical system toward the larger one. If there is a bottom, the calculation means calculates the particle size distribution of the particle group to be measured using the spatial intensity distribution data of the diffracted / scattered light from the small angle side to the first bottom. Thus characterized.

  In order to solve the same problem, the laser diffraction / scattering type particle size distribution measuring device of the invention according to claim 2, as described above, an irradiation optical system that irradiates parallel laser light onto a group of particles to be measured in a dispersed state, A measurement optical system for measuring the spatial intensity distribution of the diffracted / scattered light generated by the laser light irradiation and an arithmetic means for calculating the particle size distribution of the particle group to be measured using the spatial intensity distribution of the diffracted / scattered light. In the laser diffraction / scattering type particle size distribution measuring apparatus, from the peak / bottom detection means for detecting the peak and bottom in the spatial intensity distribution of the diffracted / scattered light measured by the measurement optical system, and the detection result of the peak and bottom, Using the values of the first peak, the first bottom, and the second peak from the smallest diffraction / scattering angle to the largest, the first peak value and the first bottom A determination means for determining whether or not the ratio of the second peak value to the difference between the two is larger than a preset value, and based on the determination result, the calculation means is a small angle only when the ratio is large. It is characterized by calculating the particle size distribution of the particle group to be measured using the spatial intensity distribution of the diffracted / scattered light from the side to the first bottom.

  The present invention was made as a result of earnest research on monodisperse particles with a steep distribution, and the measurement result of the spatial distribution of diffracted / scattered light of such particles shows the diffraction / scattering angle. It was confirmed that the light intensity in the subsequent peaks including the second peak appearing from the smaller to the larger one appears larger than the actual light intensity. It has been found that when the particle size distribution is calculated using the spatial intensity distribution of all diffracted and scattered light, it appears as the above-described under ghost, upper ghost, and the like.

  For example, FIG. 7, FIG. 8, and FIG. 9 show the measurement results of the spatial intensity distribution of diffracted / scattered light of particle groups having average particle diameters of 1 μm, 2 μm, and 3 μm, respectively, and having steep particle size distributions. In these light intensity distribution measurement results, the first bottom (hereinafter referred to as the first peak) appears after the first peak (hereinafter referred to as the first peak) that appears from the smaller diffraction / scattering angle toward the larger one. Appears, followed by the second peak (referred to as the second peak). On the other hand, FIG. 10 shows a particle group having an average particle diameter of 3 μm, which is equivalent to the particle group of FIG. 9, but has a wide particle size distribution. Such a particle group has a fast spatial intensity distribution of diffracted / scattered light. The bottom does not appear. Then, when the particle size distribution is calculated using the measurement results of FIGS. 7, 8, and 9, the under ghost, the upper ghost, or the like as described above may appear depending on the selection of the refractive index and the concentration condition. On the other hand, even if the particle size distribution is calculated in the same manner using the measurement result of FIG. 10, no underghost or upper ghost appears.

  In the measurement results of FIGS. 7, 8, and 9, when the particle size distribution was calculated using only data at a smaller angle than the first bottom, the under ghost and the upper ghost disappeared, and the particle size distribution could be obtained correctly. .

  Therefore, in the device according to claim 1, the first bottom is detected from the measurement result of the spatial intensity distribution of the diffracted / scattered light from the smaller diffraction / scattering angle toward the larger one, The particle size distribution is calculated using only the spatial intensity distribution data of the diffracted / scattered light. As a result, it is possible to suppress the occurrence of under ghosts and upper ghosts in the measurement of monodisperse particles to be measured, particularly those having a steep distribution. It becomes possible to evaluate accurately.

  In the invention according to claim 2, since the first bottom does not appear and the ghost does not appear in the particle group having a wide particle size distribution although it is monodispersed, the first bottom with a slight drop is detected and a larger angle than that is detected. It is possible to avoid calculating the particle size distribution without using the spatial intensity distribution data of diffracted / scattered light. Specifically, the first bottom falls from the first peak. Only when the increase amount of the second peak from the bottom exceeds a preset ratio, processing equivalent to that of the device according to claim 1 is performed.

  According to the present invention, under ghost and upper ghost do not occur in the particle size distribution measurement result of a particle group having a monodisperse and steep distribution, and aggregation can be evaluated correctly.

  Further, according to the second aspect of the present invention, whether the distribution is abrupt even in monodispersion, the magnitude of the second peak with respect to the difference between the first peak and the first bottom of the spatial intensity distribution of the diffracted / scattered light. It is possible to calculate an accurate particle size distribution that does not cause under ghost, upper ghost, etc. by calculating the particle size distribution using the light intensity distribution up to the first bottom only when it is automatically determined from it can.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an embodiment of the invention, and is a diagram illustrating a schematic diagram showing an optical configuration and a block diagram showing an electrical configuration.

  In the flow cell 1, a suspension S in which the particle group P to be measured is dispersed in a liquid medium flows. The flow cell 1 is irradiated with parallel laser light from an irradiation optical system 2 including a laser light source 2a such as a semiconductor laser, a condenser lens 2b, a spatial filter 2c, and a collimator lens 2d.

  Diffracted / scattered light from each particle generated by irradiating the particle group P to be measured with parallel laser light is collected by the condenser lens 3 in an angle region up to a predetermined angle in front and placed at the focal position. The spatial intensity distribution is measured by the ring detector 4. Further, the side scattered light is measured by the side scattered light sensor 5, and the backward scattered light is measured by the back scattered light sensor 6. Outputs from each of these sensor groups are amplified and digitized by a data sampling circuit 7 having an amplifier and an A-D converter, and then taken into a computer 8 as diffracted / scattered light intensity distribution data.

  In the computer 8, in addition to a program for executing the calculation based on the above equation (5) in accordance with Mie's scattering theory or Fraunhofer's diffraction theory, the intensity distribution data of the diffracted / scattered light taken in as described above is used. First peak, first bottom, and second peak are detected, and the ratio between the difference between the first peak value and the first bottom value and the second peak value is calculated, and whether or not the ratio exceeds the preset value Installed.

  For example, as shown in FIG. 2, the ratio between the difference between the first peak P1 and the first bottom B1 of the measured spatial intensity distribution of the diffracted / scattered light and the value of the second peak P2 exceeds the set value. In this case, as shown in the figure, the particle size distribution is calculated using only the light intensity distribution data from the angle exceeding the threshold to the angle of the first bottom B1.

  If the ratio does not reach the set value, the first bottom is substantially not present and the particle size distribution is calculated using all the light intensity distribution data as in the conventional case. The calculation result of the particle size distribution or the measurement result of the spatial intensity distribution of the diffracted / scattered light is displayed on the display 9 or printed on the printer 10.

  According to the above embodiment, for a monodisperse measured particle group, whether the distribution is steep or not is determined by the presence or absence of a relatively large first bottom, and when there is a relatively large first bottom, Since the particle size distribution is calculated using only the light intensity distribution at an angle smaller than the first bottom, there is no occurrence of under ghost or upper ghost when measuring particles having a steep distribution, and such particles In the case where aggregates are present, the evaluation can be performed accurately.

  In the above embodiment, the presence of a relatively large first bottom is determined by the ratio of the second peak value to the difference between the first peak value and the first bottom value, but from the spatial intensity distribution data of diffracted / scattered light, The presence or absence of the first bottom may be determined immediately.

In the block diagram of embodiment of this invention, it is the figure which writes together and shows the schematic diagram showing an optical structure, and the block diagram showing an electric structure. It is a graph which shows the example of a measurement of the spatial intensity distribution of the diffraction / scattered light measured in embodiment of this invention, and explanatory drawing of the range of the data with which it uses for calculation of a particle size distribution among them. It is a schematic diagram which shows the example of the measurement optical system of the spatial intensity | strength of the diffraction / scattering light used for a laser diffraction / scattering type particle size distribution measuring apparatus. It is a graph which shows the example of a measurement of the spatial intensity distribution of the diffracted / scattered light by the laser diffraction / scattering type particle size distribution measuring device, and an explanatory diagram of the range of data used for calculation of the particle size distribution by the conventional device. It is explanatory drawing of the ghost produced when the particle group which has a monodisperse and steep distribution is measured with the conventional laser diffraction and scattering type particle size distribution measuring apparatus. It is explanatory drawing of the problem at the time of evaluating the aggregate of the particle group which has the same monodispersed and steep distribution with the conventional laser diffraction and scattering type particle size distribution measuring apparatus. It is an explanatory diagram of an example of a measurement result of a spatial intensity distribution of diffracted / scattered light of a monodispersed particle group having a steep distribution with an average particle diameter of 1 μm, and a peak and a bottom. It is an explanatory view of an example of a measurement result of a spatial intensity distribution of diffracted / scattered light of a monodisperse particle group having a steep distribution with an average particle diameter of 2 μm, and a peak and a bottom. It is an explanatory diagram of an example of a measurement result of a spatial intensity distribution of diffracted / scattered light of a monodisperse particle group having a steep distribution with an average particle diameter of 3 μm, and a peak and a bottom. It is an example of the measurement result of the spatial intensity distribution of the diffracted / scattered light of a monodisperse particle group with a wide distribution width having an average particle diameter of 3 μm.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flow cell 2 Irradiation optical system 3 Condensing lens 4 Ring detector 5 Side scattered light sensor 6 Back scattered light sensor 7 Data sampling circuit 8 Computer 9 Display 10 Printer P Particle group to be measured P1 First peak P2 Second peak B1 First bottom

Claims (2)

Irradiation optical system that irradiates a group of particles in a dispersed state with parallel laser light, measurement optical system that measures the spatial intensity distribution of diffracted / scattered light generated by the laser light irradiation, and spatial intensity of the diffracted / scattered light In the laser diffraction / scattering type particle size distribution measuring apparatus equipped with a calculation means for calculating the particle size distribution of the particles to be measured using the distribution,
When there is a bottom detection means that detects the first bottom from the smaller diffraction / scattering angle in the spatial intensity distribution of the diffracted / scattered light measured by the measurement optical system, and the first bottom exists Wherein the calculation means calculates the particle size distribution of the particle group to be measured using the spatial intensity distribution data of the diffracted / scattered light from the small angle side to the first bottom. Distribution measuring device. Irradiation optical system that irradiates a group of particles in a dispersed state with parallel laser light, measurement optical system that measures the spatial intensity distribution of diffracted / scattered light generated by the laser light irradiation, and spatial intensity of the diffracted / scattered light In the laser diffraction / scattering type particle size distribution measuring apparatus equipped with a calculation means for calculating the particle size distribution of the particles to be measured using the distribution,
From the peak / bottom detection means for detecting the peak and bottom in the spatial intensity distribution of the diffracted / scattered light measured by the measurement optical system, and the detection result of the peak / bottom, from the smaller diffraction / scattering angle to the larger Using the values of the first peak, the first bottom, and the second peak, the ratio of the second peak value to the difference between the first peak value and the first bottom value is greater than the preset value. Only when the ratio is large based on the determination result, the calculation means uses the spatial intensity distribution of the diffracted / scattered light from the small angle side to the first bottom. A laser diffraction / scattering type particle size distribution measuring apparatus characterized by calculating a particle size distribution of a group of particles to be measured.

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