JPH0718788B2 - Optical particle measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to fine particle measurement for measuring the number and particle size distribution of fine particles by detecting an optical phenomenon that occurs when light is projected onto a fluid containing fine particles. The present invention relates to an apparatus, in particular, an apparatus having a small minimum particle size that can be measured and capable of performing measurement with high particle size resolution over a wide particle size range of particles.

[Conventional technology]

In the measurement of the number and particle size distribution of fine particles in a flowing fluid (hereinafter, this measurement may be simply referred to as measurement of fine particles), conventionally, a fine particle measuring device that uses a light blocking method and an optical A fine particle measuring device employing a scattering method is often used.

Then, the former device projects the measurement light onto the flowing fluid to be measured containing fine particles, receives the transmitted light emitted from the fluid to be measured, and appears in this received light amount. . The particle size and the number of the fine particles are measured based on the degree of the pulse-like light amount decrease due to the fine particles blocking the measurement light and the number of times of the light amount decrease.The latter device includes the fine particles. The scattered light of the measuring light generated by the fine particles generated when the measuring light is projected onto the flowing fluid to be measured is received, and the particle size of the fine particles is determined based on the degree of the pulse-like increase in the amount of the received light and the number of times of increasing the light amount. And the number of pieces are measured.

[Problems to be Solved by the Invention]

When measuring fine particles in a fluid to be measured, conventionally, the above-mentioned two types of measuring devices are often used, but the measuring device adopting the light blocking method has a large particle size, The resolution with respect to the particle diameter of the fine particles (hereinafter, this resolution may be simply referred to as the particle size resolution) is high because the magnitude of the decrease in the amount of pulsed light is approximately proportional to the projected area of the fine particles on the measurement light. In other words, in spite of the advantage that the measurement result with less variation can be obtained, when the particle size of the fine particles is about 1 μm or less, the influence of light diffraction and the like becomes large, so that the measurement sensitivity, that is, the predetermined particle size resolution is measured. There is a drawback in that the smallest particle size that can be achieved does not become too small. And then again
The measuring device adopting the light scattering method uses a He / Ne laser, a semiconducting laser, a light emitting diode or the like that emits light with a wavelength of about 600 to 800 nm as a measuring light. Although it has an advantage of being capable of measuring fine particles having a smaller particle diameter than that of a measuring device adopting a light-blocking method even though it has a measurement sensitivity even for fine particles having a small particle diameter, the particle diameter of the fine particles is about 1 μm or more. In that case, there is a drawback that the resolution with respect to the particle size of the fine particles is lowered due to the Mie scattering phenomenon of light.

An object of the present invention is to make up the above-mentioned drawbacks in the fine particle measuring device using the light blocking method and the fine particle measuring device using the light scattering method, by compensating each other with the advantages of other measuring devices. The object is to obtain a fine particle measuring device which has a sensitivity up to the lower limit particle size of and has a high particle size resolution over a wide particle size range having the lower limit particle size as the lower limit value.

[Means for Solving the Problems]

In order to achieve the above object, the device according to the present invention is a fine particle measuring device for optically and individually detecting fine particles in a fluid to be measured, in which a flow cell made of a transparent material through which the fluid to be measured flows, and the flow cell A light projecting unit that projects light, a first light receiving unit that receives the transmitted light of the measurement light that has passed through the flow cell and outputs a first light reception signal according to the light reception result, and the fluid to be measured in the flow cell. When the fine particles therein are irradiated with the measurement light, the fine scattered light is scattered by the fine particles in the substantially forward direction of the traveling direction of the measurement light, and the second scattered light signal corresponding to the light reception result is received. A second light receiving section for outputting, and first and second converting the first and second light receiving signals into a pulse waveform representing a pulse number corresponding to the number of particles and a peak value corresponding to the particle size of each particle. 2's No. converting portion and the first, the first for a predetermined time based on the pulse waveform signal outputted from the second signal converter,
The first and second counting units which respectively output a number signal corresponding to the number of fine particles detected by the second light receiving unit and a particle size distribution signal corresponding to the particle size distribution, and particles having a peak value within a predetermined range. If it corresponds to a diameter, a condition signal for validating the output from the first counting section is given, and if the peak value corresponds to a particle size exceeding a predetermined range, the second counting section is given. And a signal processing unit comprising a measurement condition setting unit that selectively outputs a condition signal to validate the output from the measurement result based on the transmitted light for fine particles having a large particle size, For fine particles having a small particle diameter, the number of fine particles and the particle diameter distribution in the fluid to be measured are measured by outputting the measurement result based on the scattered light.

[Action]

With the above configuration, the first received light signal is a signal based on the above-mentioned light blocking method, and therefore, a signal capable of obtaining a high particle size resolution measurement result for fine particles having a particle size of 1 μm or more. The second received light signal is a signal based on the above-mentioned light scattering method, and therefore, a high particle size resolution measurement result is obtained in the range of the particle size from the lower limit particle size of about 0.3 to 0.5 μm to the particle size of about 1 μm. Since it is a signal that can be generated, the data signal is set to 1 with the particle size of 0.3 to 0.5 μm as the lower limit value.
It can be used as a signal representing the measurement result of fine particles having a high particle size resolution in a wide particle size range far exceeding μm, and as a result, it has sensitivity up to the lower limit particle size of 0.3 to 0.5 μm and this lower limit. It is possible to obtain a fine particle measuring device capable of measuring fine particles over a wide range of particle diameters having the particle diameter as the lower limit value without deteriorating the particle diameter resolution.

〔Example〕

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is an enlarged view of a main part in FIG. In FIGS. 1 and 2, reference numeral 1 denotes a flow cell made of a transparent material, which is provided with a sample channel 4 having a square cross section through which a fluid to be measured 3 containing fine particles 2 flows perpendicularly to the paper surface of FIG. Reference numeral 1 is formed in a quadrangular prism shape so that a cross section perpendicular to the axis of the flow path 4 forms the illustrated square whose axis is coaxial with the axis of the flow path 4. Reference numeral 5 is a measuring light beam 6 which is a parallel light beam perpendicular to one side surface 1a of the flow cell
I tried to project it. Projection of a light source 7 such as a light emitting diode that emits light 7a, a focusing lens 8 that focuses the light 7a into the measurement light 6, and a light source drive circuit 9 that controls the intensity of the light 7a to a predetermined value. Reference numeral 10 denotes a first light receiving portion for receiving the transmitted light 11 of the measurement light 6 transmitted through the flow cell 1, and this light receiving portion 10 allows only the transmitted light 11 transmitted through the sample flow path 4 to pass therethrough. Aperture 12 designed to block light 11
And a first light receiving element 13 such as a photodiode which receives the transmitted light 11 that has passed through the aperture 12 and outputs a first light receiving signal 13a as a current signal according to the amount of received light. There is. In this case, in order to irradiate the fluid 3 to be measured with the portion of the measurement light 6 having a uniform light intensity distribution, light is projected so that the optical axis of the light projecting section 5 passes through the axis of the sample flow path 4 or its vicinity. Since the portion 5 and the flow cell 1 are arranged and the aperture 12 is configured as described above, it is effective for improving the SN ratio in the light reception signal 13a.

The reference numeral 14 converts the first received light signal 13a into a voltage signal and further amplifies this voltage signal. Thereafter, the first signal 14a corresponding to the direct current component in the amplified voltage signal and the direct current signal The second signal 14 having a signal excluding the component, that is, a time-dependent waveform corresponding to a time-dependent signal including a pulse waveform generated by the particles 2 blocking the measurement light 6.
In the first signal converter that outputs b and b, the light source drive circuit 9 described above gives the light source 7 an appropriate manipulated variable 9a when the first signal 14a is input, and the light 7a represented by the signal 14a is output. Is configured to control the strength of the constant value. It is clear from the above that one pulse waveform presented by the signal 14b corresponds to one particle 2 and the peak value of the pulse waveform corresponds to the particle diameter of the particle 2. . The second signal 14b and the first measurement condition signal 25a are input to 15 and the measurement time T designated by the condition signal 25a
While counting the number of pulse waveforms in the signal 14b input during, the first number signal 15a corresponding to the number of the fine particles 2 detected by the first light receiving unit 10 during the time T is output,
It is determined that the peak value of the pulse waveform appearing in the signal 14b during the time T belongs to the same level band among the plurality of level bands set by the condition signal 25a. By counting the number of pulses, the particle size distribution of the fine particles 2 detected by the first light receiving unit 10 is measured during the time T, and the first particle size distribution according to the measurement result is measured.
In the first counting unit that outputs the particle size distribution signal 15b, in this case,
The counting unit 15 is configured to perform the operation of outputting the above-mentioned signals 15a and 15b only when the crest value of the pulse appearing in the signal 14b corresponds to the particle size of the particles 2 within the range of 1 to 30 μm. ing.

16 is the fine particles 2 in the fluid 3 to be measured in the flow cell 1.
The fine particles 2 are irradiated by the measuring light 6
In the second light receiving section that receives the forward scattered light 17 scattered in the substantially forward direction in which the measurement light 6 travels at, and outputs the second light receiving signal 19a that is a current signal according to the light receiving result,
The light receiving unit 16 has a through hole 18a at the center thereof so that only the scattered light 17 is collected and the transmitted light 11 is not collected.
8, a converging lens 20 for condensing the scattered light 17 condensed by the lens 18 to be incident on a second light receiving element 19 such as a photodiode, and the above second light receiving signal according to the amount of incident light.
It is composed of a second light receiving element 19 for outputting 19a and an aperture 21. Then, the first light receiving portion 10 is disposed in the through hole 18a of the lens 18, and the aperture 21 has a region where the second light receiving portion 16 can receive light (hereinafter, this region is referred to as a light receiving region). It is provided for the purpose of limiting.

Since the second light receiving portion 16 is configured as described above, the light receiving area is formed by the lenses 18, 20, the aperture 21, and the light receiving surface 19b of the light receiving element 19 in a spindle shape, and the area shown in FIG. 2
It looks like 2. In FIG. 2, 30 is a light receiving area 22.
Is the optical path of the light rays that form the boundary of. Then, in this case, since each part is configured such that all of the sample flow path 4 irradiated with the measurement light 6 is included in the light receiving region 22, when the measurement light 6 irradiates the fine particles 2, Of the scattered light emitted from the fine particles 2, all of the forward scattered light 17 toward the lens 18 shown in FIG. 1 is incident on the light receiving element 19. That is, in FIG. 1, the emission region of the scattered light 17 formed by the second light receiving unit 16 coincides with the portion of the sample flow path 4 irradiated with the measurement light 6. Then, in addition, in FIG. 1, the first light receiving unit 10 is configured as described above. Therefore, in this case, the emission region of the transmitted light 11 detected by the first light receiving unit 10 and the scattered light detected by the second light receiving unit 16 are detected.
This means that the exit areas of 17 coincide with each other.

The second light reception signal 19a is input to the signal 23, which is converted into a voltage signal and then amplified, and then the time-dependent signal 23 corresponding to the signal obtained by removing the DC component from the amplified voltage signal.
The second signal conversion unit 24 that outputs a receives the time-dependent signal 23a and the second measurement condition signal 25b, and in the signal 23a that is input during the measurement time T designated by the condition signal 25b,
The number of pulse waveforms based on the forward scattered light 17 by the fine particles 2 is counted, and a second number signal 24a corresponding to the number of the fine particles 2 detected by the second light receiving unit 16 is output during the time T and at the same time T The peak value of the pulse waveform appearing in the signal 23a during is determined to which one of the plurality of level bands set by the condition signal 25b belongs, and the pulse of the pulse belonging to the same level band is determined. By counting the number of particles, the particle size distribution of the fine particles 2 detected by the second light receiving unit 16 is measured during the time T, and the second count that outputs the second particle size distribution signal 24b according to the measurement result. In the counting section 24, the crest value of the pulse appearing in the signal 23a is 0.3 to 1 μm.
Signal above only if it corresponds to a particle size in the range of m
It is configured to perform an operation of outputting 24a and 24b.

25 is the above-mentioned first measurement condition signal in response to the setting operation by the appropriate setting operation such as key operation.
25a and a second measurement condition signal 25b are output as a measurement condition setting unit, and the setting unit 25 outputs the signals 25a and 25b to the first and second counting units 15 and 24 at the same time. It is configured to start each of the above counting operations and simultaneously stop these counting operations. 26 is a first and second signal converter 14, 23 and a first and second counter 15,
A signal processing unit consisting of 24 and a measurement condition setting unit 25, 27 is the first
And the second number signals 15a, 24a and the first and second particle size distribution signals 1
5b and 24b are data signals. Since each part of the signal processing unit 26 is configured as described above, the processing unit 26 receives the first and second light receiving unit signals 13a and 19a and inputs these signals. Can be said to be one which performs a predetermined signal processing and outputs a data signal 27 according to the result. Then, in this case, it is apparent from the above that the number and the particle size distribution of the fine particles 2 in the fluid to be measured 3 can be measured based on the data signal 27. Reference numeral 28 is an optical fine particle measuring device comprising the respective parts shown in FIG.

In FIG. 1, it is apparent that the particle measuring device 28 is constructed as described above, and that the first light receiving signal 13a is a signal by the light blocking method and the second light receiving signal 19a is a signal by the light scattering method. 1 to 30μ depending on the signals 15a and 15b
The number and the particle size distribution can be measured with high particle size resolution for the fine particles 2 having a particle size of m, and the high particle size resolution can be obtained for the fine particles 2 having a particle size of 0.3 to 1 μm by the signals 24a and 24b. The number and particle size distribution can be measured with. Then, as described above, the emission area of the transmitted light 11 detected by the light receiving section 10 and the emission area of the scattered light 17 detected by the light receiving section 16 are the same. Therefore, the measuring device 28 has sensitivity to the fluid 3 to be measured in the sample flow path 4 up to a fine lower limit particle size of 0.3 μm, and the lower limit particle size of 0.3 μm to the upper limit particle size of 30 μm. The optical particle measuring device is capable of measuring the particles 2 over a very wide particle size range up to the diameter without degrading the particle size resolution.

Then, in the measuring device 28, the second received light signal 19a by the light scattering method is a signal obtained by the forward scattered light 17, and if the forward scattered light is used, the second scattered light signal 19a is generated with respect to the optical axis of the measuring light 6. It is customary to obtain fine particle measurement results with a better particle size resolution than using side scattered light emitted in a substantially vertical direction. Therefore, also in terms of the kind of scattered light, the measuring device 28 has an advantage that the particle size resolution in the particle measurement based on the second received light signal 19a is improved.

〔The invention's effect〕

According to the present invention, the first received light signal is a signal based on the above-mentioned light blocking method, and is therefore a signal capable of obtaining a measurement result with high particle size resolution for fine particles having a particle size of 1 μm or more. The second received light signal is a signal based on the above-mentioned light scattering method, in particular, a method using forward scattered light.
Since it is a signal that can obtain a high particle size resolution measurement result in the range of the particle size from the lower limit particle size of about 0.5 μm to the particle size of about 1 μm, the data signal is 0.3 to 0.5 μm.
Can be used as a signal representing the measurement result of fine particles having a high particle size resolution in a wide particle size range far exceeding 1 μm with the particle size of 0.1 μm as the lower limit value.
A fine particle measuring device is obtained which has a sensitivity up to a lower limit particle size of up to 0.5 μm and is capable of measuring fine particles over a wide particle size range having the lower limit particle size as the lower limit value without degrading the particle size resolution. effective.

Further, in the present invention, since the first light receiving signal is a signal based on the light blocking method and the second light receiving signal is a signal based on the light scattering method, it is possible to simultaneously measure the same fine particles by using both light receiving signals. When the signal processing unit is configured, the particle measurement result based on two types of measurement principles can be obtained at the same time.Therefore, in the present invention, when the signal processing unit is configured in this way, it is difficult to adjust the fluid to be measured or This is effective in obtaining highly reliable measurement results when the concentration of fine particles in the measurement fluid is low.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is an enlarged view of a main part in FIG. 1 ... Flow cell, 2 ... Fine particles, 3 ... Fluid to be measured,
5 ... Projector, 6 ... Measuring light, 10 ... First light receiver, 11 ...
… Transmitted light, 13a …… First light receiving signal, 16 …… Second light receiving section, 1
7: Forward scattered light, 19a: Second received light signal, 26: Signal processing unit, 27: Data signal, 28: Optical particle measuring device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Hoshikawa 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. No. 1 within Fuji Electric Co., Ltd. (56) Reference JP-A 63-49207 (JP, A) JP-A 60-161548 (JP, A) JP-A 53-86298 (JP, A) JP-A 51- 1187 (JP, A)

Claims (1)

[Claims] 1. A fine particle measuring apparatus for optically individually detecting fine particles in a fluid to be measured, comprising: a flow cell made of a transparent material through which the fluid to be measured flows, and a light projecting section for projecting measurement light to the flow cell. A first light receiving portion that receives the transmitted light of the measurement light that has passed through the flow cell and outputs a first light reception signal according to the light reception result; and fine particles in the fluid to be measured in the flow cell that are generated by the measurement light. A second light receiving unit that receives the forward scattered light that is scattered by the fine particles toward the front in the direction in which the measurement light travels by being irradiated, and outputs a second light receiving signal according to the light receiving result; First and second signal converters for respectively converting the first and second received light signals into pulse waveforms representing a pulse number corresponding to the number of fine particles and a peak value corresponding to the particle size of each fine particle, First and second signals Based on the pulse waveform signal output from the conversion unit, a number signal corresponding to the number of fine particles detected by the first and second light receiving units and a particle size distribution signal corresponding to the particle size distribution are generated during a predetermined time. Outputting first and second counting units, and a condition signal for validating the output from the first counting unit when the crest value corresponds to a particle size within a predetermined range. A signal processing unit including a measurement condition setting unit that selectively outputs a condition signal that validates the output from the second counting unit when the high value corresponds to a particle size exceeding a predetermined range, The number of fine particles in the fluid to be measured is set to output the measurement result based on the transmitted light for fine particles having a large particle size, and output the measurement result based on the scattered light for fine particles having a small particle size. And an optical characteristic characterized by measuring the particle size distribution Particle measuring apparatus.