JP4105888B2 - Particle size distribution measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention detects a diffraction / scattered light generated by irradiating a dispersed particle group with laser light, and measures a particle size distribution of the particle group based on a scattered light intensity signal obtained by the detection. The present invention relates to a distribution measuring apparatus.
[0002]
[Prior art]
The particle size distribution measuring device using the diffraction and / or scattering phenomenon of light by sample particles measures the intensity distribution of diffracted light and / or scattered light, that is, the relationship between diffraction angle and / or scattering angle and light intensity. Then, the particle size distribution of the sample particles is calculated by performing arithmetic processing based on the Fraunhofer diffraction theory and / or the Mie scattering theory.
[0003]
FIG. 3 schematically shows an essential part of an optical system in a conventional particle size distribution measuring apparatus. In this figure, for example, 41 is a liquid in which particles are dispersed in a dispersion medium (hereinafter referred to as a sample liquid). It is a sample cell to be accommodated. Reference numerals 42 and 43 denote a light source and a condenser lens provided on one side of the sample cell 41 in the thickness direction, that is, on the rear side of the sample cell 41, and 44 denotes the other side in the thickness direction of the sample cell 41, that is, In the photodiode array detector (multi-channel detector) provided at the focal position of the condenser lens 43 on the front side of the sample cell 41, the transmitted light and the scattered light having a relatively small scattering angle (for example, 0 to 30 °) are generated. This is to be detected, and is formed in a so-called inverse Fourier optical system in which the condenser lens is located on the light source side. The scattered light having a relatively large scattering angle (30 ° or more) is detected by a plurality of photodiodes (single-channel detectors) (not shown) provided also on the side and rear of the sample cell 41. .
[0004]
By the way, in the particle size distribution measuring apparatus having the above configuration, scattered light from a large particle having a diameter of 1 mm or more is strongly detected near the focal point of the condenser lens 43. For this reason, in order to reliably measure the large particles, the vicinity of the transmitted light channel 44a at the center of the photodiode array detector 44 is finely processed, and scattered light having a small scattering angle (for example, 0 to 5 °). In this case, there is a problem that the manufacturing cost of the photodiode array detector 44 increases and the cost of the entire apparatus increases.
[0005]
Therefore, if it is attempted to detect the scattered light having a small scattering angle without finely processing the vicinity of the center portion of the photodiode array detector 44, it is necessary to increase the focal length of the condenser lens 43. When the distance is increased, the distance L in the figure increases, and in order to receive scattered light in the same scattering angle range (for example, 0 to 30 °), the dimension H of the photodiode array detector 44 increases accordingly. Also in this case, there is a problem that the manufacturing cost of the photodiode array detector 44 is increased and the cost of the entire apparatus is increased.
[0006]
[0007]
The present invention has been made in consideration of the above-mentioned matters, and the object thereof is to reduce the particle diameter while constituting a photodiode array detector for detecting scattered light having a relatively small scattering angle with an inexpensive one. An object of the present invention is to provide a particle size distribution measuring apparatus capable of measuring the distribution with high accuracy.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a particle size distribution measuring device according to the present invention is arranged between a light source, a sample cell irradiated with light from the light source, and the light source and the sample cell on the optical axis of the light. Particle size distribution configured in an inverse Fourier optical system by a condensing lens to be transmitted and a first array detector disposed in the vicinity of the focal position of the condensing lens that focuses the transmitted light transmitted through the sample cell a measuring apparatus, in front and rear of the first array detector of the sample cell, the scattered light detected by said first array detector in the scattered light can not be detected by the first array detector the arrangement is a second array detector for detecting up to scattered light of a predetermined angle from the angle continuous with the scattering angle, dispersion of the predetermined angular range of transmitted light as well as continuous by the these first array detector and a second array detector It is characterized by being configured to detect by sharing the light.
[0009]
[0010]
In the invention having the above-described configuration, in addition to the first array detector, a second array detector is provided. By these two array detectors, for example, transmitted light of 0 to 30 ° and scattered light having a relatively small scattering angle are provided. So that the scattered light in the predetermined angle range can be received continuously without being scattered. In the first array detector, the focal length is relatively long, but only the transmitted light and scattered light having a small scattering angle (for example, about 0 to 10 °) are received, and the size (see FIG. The dimension L1 in 2 is as small as possible. And in this 1st array detector, even if it does not give fine processing to a center part, the scattered light with the said small scattering angle can be light-received reliably, and the measurement of a large particle of 1 mm or more can be performed. . On the other hand, the second array detector can receive scattered light with a slightly small scattering angle (for example, about 5 to 30 °) that cannot be detected by the first array detector, and can measure small particles of less than 1 mm. it can. The second array detector does not need to be further finely processed in the center than the first array detector. In this case, a commercially available mass-produced linear photodiode array can be used.
[0011]
That is, by using two array detectors, the same scattering angle range (for example, 0 to 30 °) can be obtained even when the array detector is arranged with an extended focal length compared to the case of using one array detector. ) Can be reduced in size (H1 in FIG. 2), and as a result, an inexpensive photodiode array can be used, so that the manufacturing cost of the entire device can be reduced. Can be reduced. Of course, the measurement accuracy does not decrease.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the details of the present invention will be described with reference to the drawings. 1 and 2 show one embodiment of the present invention. FIG. 1 schematically shows an example of the configuration of a particle size distribution measuring apparatus according to the present invention, and FIG. 2 shows the configuration of the main part thereof. Is shown together with an enlarged view. In the particle size distribution measuring apparatus shown in FIG. 1, the optical system is an inverse Fourier optical system. That is, in FIG. 1, reference numeral 1 denotes a sample cell made of a transparent container containing a liquid (hereinafter referred to as a sample liquid) 2 in which a particle group to be measured is dispersed in a dispersion medium, and its length (thickness) in the optical path direction. Is smaller than in conventional devices of this type. The sample cell 1 may be a flow-through sample cell to which the sample liquid 2 is flowed.
[0013]
Reference numeral 3 denotes a laser light source as an irradiation light source provided on the rear side of the sample cell 1 and emits laser light. A condensing lens 4 is provided between the laser light source 3 and the sample cell 1 and has a relatively long focal length, for example, 300 mm. The laser light emitted from the laser light source 3 is appropriately converged by the condensing lens 4 and becomes the condensed laser light (irradiation light) 3 a to irradiate the sample liquid 2 in the sample cell 1.
[0014]
Reference numeral 6 denotes a first array detector provided on the front side of the sample cell 1, which is arranged at a position where the transmitted light 5 transmitted through the sample cell 1 is focused, that is, at the focal position of the condenser lens 4. The first array detector 6 is composed of a plurality of photodiodes. For example, as shown in an enlarged illustration portion A of FIG. 2, the transmitted light detection portion is provided so as to correspond to the optical axis 4a of the condenser lens 4. 6a and a plurality of scattered light detectors 6b in which a plurality of ring-shaped or semi-ring-shaped light-receiving surfaces having different radii are arranged concentrically around the transmitted light detector 6a. The scattered light 7 that is provided in a state orthogonal to the optical axis 4 a and is scattered / diffracted at a small angle (for example, about 0 to 5 °) among the irradiation light L that is diffracted or scattered by the particles in the sample cell 1 for each scattering angle. Are respectively received and measured for their light intensity. The first array detector 6, the overall length (indicated by reference numeral L1 in Fig. 2) is intended a small example of about 25 mm, even without applying fine processing to the central unit, for receiving the small angle scattered light 7 It is possible to measure large particles of 1 mm or more. Reference numeral 8 denotes a preamplifier for amplifying the outputs of the photodiodes 6a and 6b constituting the first array detector 6.
[0015]
Reference numeral 9 denotes a second array detector provided between the first array detector 6 and the sample cell 1. The second array detector 9 is a light 10 that cannot be detected by the first array detector 6, that is, The scattered light 10 scattered / diffracted at a slightly smaller angle (for example, about 5 to 30 °) out of the irradiation light 3a diffracted or scattered by the particles in the sample cell 1 is received for each scattering angle, and these lights are received. Strength is measured. Since the second array detector 9 does not require further microfabrication than the first array detector 6, a plurality of rectangular light receiving portions 9a, for example, upper and lower parts are arranged as shown in an enlarged portion B of FIG. It is composed of a commercially available mass production type linear photodiode arranged in the direction, and is provided with its light receiving surface orthogonal to the optical axis 4a. Reference numeral 11 denotes a preamplifier for amplifying the output of the photodiode 9a constituting the second array detector 6.
[0016]
Further, in the vicinity of the sample cell 1, wide-angle scattered light scattered / diffracted at a relatively large angle (for example, 30 to 180 °) among the irradiation light 3a diffracted or scattered by the particles in the sample cell 1 is scattered at each scattering angle. A wide-angle scattered light detector group 12 is provided for each detection. The wide-angle scattered light detector group 12 includes a plurality of photodiodes 13 to 15 provided at different angles from the first array detector 6 and the second array detector 9, and according to the respective arrangement angles, Scattered light having a predetermined angle exceeding a predetermined angle due to particles in the sample cell 1 can be detected, the photodiode 13 is forward scattered light 16a, the photodiode 14 is side scattered light 16b, and the photodiode 15 is back scattered. Each of the lights 16c is detected. Reference numeral 17 denotes an electric circuit board that holds the photodiodes 13 to 15 at a predetermined angle, and includes a preamplifier.
[0017]
Reference numeral 18 denotes a multiplexer that sequentially takes outputs from the preamplifiers 11 and the electric circuit board 17 and sequentially sends them to the AD converter 19, and 20 denotes a computer as an arithmetic processing unit to which the output of the AD converter 19 is input. The computer 20 uses the outputs of the first array detector 6, the second array detector 9, and the photodiodes 13 to 15 (digital data relating to light intensity) converted into digital signals based on Fraunhofer diffraction theory and Mie scattering theory. A program for obtaining the particle size distribution in the particle group is stored. Reference numeral 21 denotes a color display for displaying calculation results and the like.
[0018]
In the particle size distribution measuring apparatus configured as described above, when laser light is emitted from the laser light source 3 while the sample liquid 2 is housed in the sample cell 1, the laser light is converged by the condenser lens 4. The sample liquid 2 in the sample cell 1 is irradiated with the irradiation light 3a. The irradiation light 3 a is diffracted or scattered by particles in the sample cell 1. Of the diffracted light or scattered light, scattered light 7 having a small scattering angle of 0 to 5 ° (scattered light caused by large particles of 1 mm or more) is received on the first array detector 6 and is 5 to 30 °. Scattered light 10 having a slightly smaller scattering angle (scattered light caused by small particles of less than 1 mm) is received on the second array detector 9. The light intensities detected by the array detectors 6 and 9 are converted into analog electric signals, and further input to the multiplexer 18 via the preamplifiers 8 and 11.
[0019]
On the other hand, among the irradiation light 3a diffracted or scattered by the particles, those having a relatively large scattering angle are detected by the wide-angle scattered light detector group 12, and the light intensity distribution is measured. In this case, the forward scattered light photodiode 13, the side scattered light photodiode 14, and the back scattered light photodiode 15 detect scattered light 16a to 16c from particles that become smaller in this order. The light intensity detected by each of the photodiodes 13 to 15 is converted into an analog electric signal, and further input to the multiplexer 18 through a preamplifier provided on the electric circuit board 17.
[0020]
In the multiplexer 18, measurement data from the first array detector 6, the second array detector 9, and the photodiodes 13 to 15, that is, analog electric signals are sequentially taken in a predetermined order. Then, the analog electric signal taken in by the multiplexer 18 is converted into a serial signal, sequentially converted into a digital signal by the AD converter 19, and further input to the computer 20.
[0021]
In the computer 20, the light intensity data for each scattering angle respectively obtained by the first array detector 6, the second array detector 9, and the plurality of photodiodes 13 to 14 is converted into Fraunhofer diffraction theory and Mie scattering theory. Process based on.
[0022]
As described above, in the particle size distribution measuring apparatus, the first array detector 6 and the light intensity distribution of the transmitted light and the scattered light having a relatively small scattering angle caused by the particle size range having a large particle size are used. The light intensity distribution of the scattered light having a wide angle caused by the particle diameter range having a small particle diameter is measured by the second array detector 9 so that the light receiving angle range is continuous, and the photodiodes 13 to 15 are used. Since the measurement and the outputs of the first array detector 6, the second array detector 9, and the photodiodes 13 to 15 are processed by the computer 20, the particle size distribution in the particle group is relatively large. To a small particle diameter can be obtained all at once.
[0023]
In the particle size distribution measuring apparatus, the two array detectors 6 and 9 share the detection of scattered light in a range where the scattering angle is relatively small, such as 0 to 30 °. In particular, the center portion of the first array detector 6 that detects the scattered light 7 having a small scattering angle (0 to 5 °) may be hardly subjected to fine processing, and the dimension L1 can be reduced. The manufacturing cost can be greatly reduced. In addition, the center portion of the second array detector 9 that detects the scattered light 10 having a slightly small scattering angle (5 to 30 °) does not need to be finely processed, and a commercially available mass-produced linear photodiode array is used. Therefore, the manufacturing cost can be significantly reduced.
[0024]
[0025]
[0026]
In the above embodiment, the light source 3 emits laser light, but a white light source may be used instead. The first array detector 6 is not limited to one in which a plurality of scattered light detectors 6b are arranged concentrically around the transmitted light detector 6a. For example, a simple configuration in which a photodiode is simply divided into a plurality of parts. May be used. The angle range of the scattered light received by the first array detector 6 and the second array detector 9 is, for example, the scattered light having the first array detector 6 ranging from 0 to 10 °. 9 may be somewhat overlapped, such as scattered light from 7 to 30 °. Furthermore, although the first array detector 6 and the second array detector 9 are provided so that their light receiving surfaces are perpendicular to the optical axes of the condenser lenses 4 and 24, it is not necessary to do so. The light receiving surface may be provided so as to form an angle other than 90 ° with the optical axis.
[0027]
【The invention's effect】
In this invention, transmitted light and light scattered at a relatively small scattering angle are detected by the two array detectors so as to share the angular range of the scattering angle, so one array detector was used. Compared to the case, it is not necessary to finely process the center portions of the two array detectors, and the size of all photodiode arrays required to receive scattered light in the same scattering angle range is reduced. Therefore, an inexpensive photodiode array can be used, and as a result, the entire apparatus can be configured at low cost without any decrease in measurement accuracy.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an example of the configuration of a particle size distribution measuring apparatus according to the present invention.
FIG. 2 is a diagram showing an example of an optical system of the particle size distribution measuring apparatus together with an enlarged view.
FIG. 3 is a diagram for explaining a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sample cell, 2 ... Sample, 3 ... Light source, 3a ... Irradiation light, 4 ... Condensing lens, 5 ... Transmitted light, 6 ... 1st array detector, 6a ... Transmitted light detection part, 6b ... Scattered light detection part , 7 ... scattered light, 9 ... second array detector, 10 ... scattered light, 23 ... irradiation light 24 ... condenser lens, 25, 26 ... scattered light.

Claims (1)

A light source, a sample cell irradiated with light from the light source, a condenser lens disposed between the light source and the sample cell on the optical axis of the light, and a transmitted light transmitted through the sample cell are in focus A particle size distribution measuring apparatus configured in an inverse Fourier optical system with a first array detector disposed in the vicinity of the focal position of the condenser lens connecting the condensing lens, and in front of the sample cell and the first array detection Behind the detector, the scattered light that cannot be detected by the first array detector is detected from an angle continuous with the scattering angle of the scattered light detected by the first array detector to a scattered light having a predetermined angle. particles in which the second array detector is arranged, characterized by being configured to detect by sharing the scattered light in a predetermined angular range of transmitted light as well as continuous by the these first array detector and a second array detector Diameter distribution Constant apparatus.

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