JPH0498145A - Counting device for particulates in fluid - Google Patents

Abstract

PURPOSE:To miniaturize a device and accurately count particulates having from a fine particle diameter to a relatively large particle diameter by overlapping beams, outgoing from plural light sources, in a detection tube to irradiate fluid. CONSTITUTION:Lenses 17 and 18, a light receiving element 19, and a pre-amplifier on a printed board 20 are arranged, along a direction orthogonal to a beam irradiation direction from a light source 1, in the side of a detection cell 8, and side scattered light from particulates in fluid is detected with the lenses 17 and 18 and the light receiving element 19, etc. The whole counting device can be miniaturized because the passage of the fluid and the beam from the light source l are not on the same axis as samples. Irradiation light strength is increased because three beams from three light sources 1 are overlapped in a detection tube 11. This also increases the strength of the forwardly scattered light, and correctly makes the counting of the particulates having fine particle diameter and the measuring of particle diameters.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a particle counting device in a fluid, and more specifically, a particle counting device that counts the number of particles contained in a fluid such as a liquid or gas by light scattering. Regarding.

(Prior Art) The inventor previously filed Japanese Patent Application No. 62-288474 (Japanese Unexamined Patent Publication No.
131433) proposed this type of particle counting device in fluid. This particulate counting device includes a detection tube that is at least partially transparent, a light source that causes a beam whose cross section is substantially the same as the cross-sectional shape of a hollow portion of the detection tube to pass coaxially into the detection tube, and a transparent and a photodetector disposed on an imaginary straight line drawn at an angle to the axis of the detection tube from one point of the detection tube with the detection direction directed toward the - point.

According to this particulate counting device, by passing a fluid into a detection tube and making the beam enter from a light source along the axis of the detection tube, the beam that hits the particulates in the fluid conforms to the so-called Gustav Mie's light scattering theory. subject to the following scattering. Therefore, by detecting this scattered light with a photodetector, the particles can be counted, and the particle size of the particles can be measured from the intensity of the scattered light.

(Problem to be Solved by the Invention) In the particle counting device configured as described above, since the fluid flow path and the beam from the light source are coaxial, it is not necessary to arrange the light source at the end of the fluid flow path. However, there is a drawback that the entire counting device inevitably becomes larger in the direction of the fluid flow path.

In addition, since the light source is usually a single light source, the light intensity irradiated to the particles is generally weak, and the intensity of the light scattered from the particles is also weak, which may result in inaccurate counting of particles or accurate measurement of particularly small particle sizes. There were cases where measurements could not be taken. Furthermore, in the conventional technique, by narrowing down the beam, the cross section of the beam may be too small compared to the cross section of the detection section through which the particles pass within the detection cell, which may cause failure to count the particles.

In addition, it is ideal for this type of particle counting device to be able to count all particles, from minute particles to relatively large particles, but conventional counters with only a single light receiving optical system The device also has the problem that the output voltage of the preamplifier connected to the output side of the light receiving element saturates up to a certain particle size range, making it impossible to count particles with a particle size larger than that.

The present invention has been made to solve the above problems,
The object of the present invention is to provide a particle counting device in a fluid that can be miniaturized and can accurately count particles ranging from minute particles to relatively large particles.

(Means for Solving the Problems) In order to achieve the above object, the present invention superimposes a plurality of beams irradiated from a plurality of light sources in a detection cell, and a fluid such as liquid or gas is applied to the superimposed point. At the same time, at least one beam among the plurality of beams is made substantially perpendicular to the flow path of the fluid, and forward scattered light by particles in the fluid is collected in the forward direction of the beam through the detection cell. A first light-receiving optical system for converting light into an electric signal is disposed, and on the side of the detection cell, for collecting side scattered light from fine particles in the fluid and converting it into an electric signal. One or more light receiving optical systems are arranged.

In the case of a device for counting particles in liquid, if a microlens is placed on the front outer peripheral surface of the detection cell to focus the forward scattered light in the direction of the first light receiving optical system, the forward scattered light can be The light collection efficiency can be increased.

(Function) According to the present invention, a plurality of beams emitted from a plurality of light sources are superimposed within the detection tube and irradiated onto the fluid. As a result, forward scattered light with high light intensity is generated from the fine particles in the fluid, and this scattered light enters the light receiving element via the microlens and the condensing lens of the first light receiving optical system. Particle counts and particle size measurements are performed. In addition, side scattered light generated from fine particles in the fluid enters the light receiving element through one or more condensing lenses of the light receiving optical system installed on the side of the detection cell, and Particle counts and particle size measurements are performed.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

First, FIG. 1 is a sectional view of the main part of this embodiment, and FIG. 2 is a sectional view of the main part seen from above in FIG. In these figures, l is a light source attached to the light source holder 6, and three light sources l are arranged on the same plane so that the intersecting angle with the optical axis of the adjacent light source l is approximately 45 degrees. The beams emitted from the light source 1 overlap at one point inside a detection tube 11 in a detection cell 8, which will be described later. Here, the light source 1 is composed of a semiconductor laser 2, lenses 3 and 4, and a cylindrical lens 5 having a roughly semi-cylindrical shape. .8+
nm) and enters the detection tube 11 in a substantially band-like form.

The passage hole for the fluid (liquid in this embodiment) in the detection tube 11 has a substantially circular cross section, and its inner diameter is, for example, 0.6 mm.

Therefore, by irradiating the detection tube 11 with a beam that is wider than the inner diameter of the detection tube II, all the fluid passes through the cross section of the beam, making it possible to eliminate failure to count particles.

On the other hand, 7 is a frame that includes therein a detection cell 8, a liquid inflow/outflow system, and a scattered light receiving optical system. That is,
This frame 7 has a liquid inflow pipe 9 through which liquid as a sample flows in, and a liquid outflow pipe IO through which liquid flows out, which are arranged coaxially between the two 9 and 10, and are made of a substantially cylindrical transparent material. A detection cell 8 is provided. The inflow pipe 9 and the outflow pipe 10 are arranged in the detection cell 8.
The detection tube 11 that communicates with the light source 1 has a transparent central portion and allows three beams from each light source 1 to enter therein. Note that dry nitrogen gas is sealed in the detection cell 8 to prevent dew condensation from forming on the cell surface due to temperature differences inside and outside the cell.

A roughly hemispherical microlens 12 is attached to the front outer peripheral surface of the detection cell 8 on the side opposite to the light source 1 . As shown in FIG. 3, this microlens 12 also focuses forward scattered light (indicated by broken lines in FIG. 3) by fine particles over a wide range, which would not enter the lens 13 if the microlens 12 were not present. act.

In FIGS. 1 and 2, lenses 13 and 14 are arranged in front of the microlens 12, and light receiving elements 15 are arranged coaxially in front of the lens 14, respectively. Further, the light receiving element 15 is connected to a preamplifier (not shown) mounted on a printed circuit board 16.

Here, the microlens 12, lenses 13, 14, light receiving element 15, etc. constitute a first light receiving optical system.

Furthermore, as shown in detail in FIG. 2, the side force of the detection cell 8 includes the force on the lens +7. A preamplifier (not shown) is arranged and these lenses 17. +8, the light-receiving element 19, etc. constitute a second light-receiving optical system that detects side-scattered light from fine particles in the liquid.

According to the particle counting device according to this embodiment configured in this way, the flow path of the liquid as a sample and the beam from the light source l are not coaxial, so the entire counting device becomes larger in the direction of the liquid flow path. No worries.

Furthermore, since the three beams from the three light sources 1 overlap within the detection tube 11, the intensity of the irradiated light is increased compared to the conventional method.

This also increases the intensity of the forward scattered light, making it possible to accurately count and measure the particle size of microparticles. At the same time, if the liquid flow rate is large (e.g. 10 (
Since particles can be reliably detected without any detection failures even at low speeds (lul/min), it is possible to improve the efficiency of particle counting work.

Note that FIG. 4 shows forward scattered light by three beams, and in this embodiment, in addition to L1, which corresponds to the conventional forward scattered light, , L, are also condensed by the microlens 12. This makes it possible to improve detection sensitivity.

Furthermore, since this embodiment includes first and second light receiving optical systems, the first light receiving optical system, which receives a large amount of forward scattered light, detects fine particles with a small particle size, and The second light-receiving optical system, which receives a relatively small amount of light, can share responsibilities such as detecting relatively large-diameter particles, expanding the dynamic range of measurement without considering preamplifier output saturation, etc. be able to.

You can expand it.

In addition, although the case where three light sources 1 were provided was explained in the said Example, it is also possible to arrange|position even more light sources in this invention. Further, the fluid serving as a sample for counting particles may be not only a liquid but also a gas.

Furthermore, in the above embodiment, the lens +7.18 and the light receiving element 19
As shown in Fig. 2, the second light-receiving optical system consisting of the It may be placed in the front. As a result, more scattered light is received by the second light-receiving optical system, and detection sensitivity can be improved.

Further, the number of second light receiving optical systems does not need to be single;
A plurality of light receiving optical systems may be arranged around the detection cell 8, respectively. By doing so, side scattered light can be detected more efficiently and relatively large-diameter particles can be detected with high precision.

(Effects of the Invention) As described above, according to the present invention, since the beam irradiation direction and the fluid flow path are not coaxial, there is no risk of the counting device becoming larger in the flow path direction, and it is relatively compact. A counting device can be realized.

In addition, since the beams emitted from multiple light sources are superimposed at one point, and light scattering occurs on the particles at the superimposed point, the intensity of scattered light increases dramatically compared to conventional methods, making it difficult to count. There is no need to worry about leakage, and it becomes possible to count and measure the particle diameter of microparticles (for example, 0.1 μm or less) and to measure the microparticles in a fluid with a large flow rate in a short time.

Furthermore, by providing one or more light-receiving optical systems for detecting side scattered light, the light intensity received by the light-receiving optical system is relatively low.
It is possible to count fine particles having a large particle size of .mu.m, and on the other hand, the first light receiving optical system can be used exclusively for counting fine particles having a particle size of 0.7 .mu.m or less, for example. This significantly expands the measurable particle size range, unlike the conventional single light-receiving optical system, which limits the measurable particle size range due to factors such as saturation of the preamplifier output voltage. I can do it.

[Brief explanation of the drawing]

1 to 4 are for explaining one embodiment of the present invention, FIG. 1 is a sectional view of the main part, FIG. 2 is a sectional view of the main part seen from above in FIG. 1, FIG. 3 is an explanatory diagram of the action of the microlens, and FIG. 4 is an explanatory diagram of forward scattered light. 1... Light source 2... Semiconductor laser 5...
・Cylindrical lens 8...Detection cell 9...Liquid inflow tube 10...Liquid outflow tube 11・
・Detection tube 12...Micro lens 3.4.
+3.14.17.18... Lens 15, 19... Light receiving element

Claims (2)

[Claims] (1) Irradiate a fluid containing fine particles with a beam from a light source,
In a particle counting device in a fluid that counts the particles by detecting light scattered by the particles, a plurality of beams irradiated from a plurality of light sources are superimposed in a detection cell, and the beams pass through the fluid to the point of this superimposition. At the same time, at least one beam among the plurality of beams is made substantially perpendicular to the flow path of the fluid, and forward scattering by fine particles in the fluid in the detection cell is caused to occur forward in the traveling direction of the beam through the detection cell. A first light-receiving optical system for condensing light and converting it into an electrical signal is disposed, and on the side of the detection cell, condenses side scattered light due to particulates in the fluid in the detection cell. 1. A device for counting particles in a fluid, characterized in that one or more light-receiving optical systems are arranged for converting light into electrical signals. (2) The apparatus for counting particles in a fluid according to claim (1), further comprising a microlens disposed on the front outer peripheral surface of the detection cell for condensing the forward scattered light in the direction of the first light receiving optical system.