JPS6258138A - Method and apparatus for measuring particle - Google Patents

Abstract

PURPOSE:To accurately perform measurement even when the density of particles is low, in a method for measuring scattered beam from particles to be measured by irradiating the particles to be measured with coherent beam, by reciprocating luminous flux plural times to cover measuring region with coherent luminous flux. CONSTITUTION:Water containing fine particles 20 is made to flow into a flow cell 2 and laser beam 1a is brought to be incident on the side surface 3 of the flow cell 2 from a laser beam source 1. The incident beam refracts on the wall surface of the flow cell 2 to be scattered by the fine particles and the greater part of the remain der reaches the side wall 4 to be emitted to the outside while refracted. A first reflec tive mirror 5 is provided in close vicinity to the side wall 4 and the beam emitted from the flow cell 2 is reflected to be again transmitted through the water in the flow cell 2. A second reflective mirror 6 is provided outside the side wall 3 and the beam emitted from the side wall 3 is again reflected from the flow cell 2 to be recipro cated plural times. At this time, the scattered beam from the fine particles is detected by the photomultiplier tube 10. Because a measuring region is covered with beam, low density fine particles can be measured with high accuracy within a short time.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a particle measurement method and apparatus thereof, and more particularly, to a method for measuring particles by irradiating the particles to be measured with a beam of light from a coherent light source such as a laser light source. The present invention relates to a particle measurement method and apparatus for measuring particle characteristics such as particle size and number of particles by measuring scattered light of particles.

[Prior Art] Conventionally, the scattered light flux from a laser light source has been measured based on the principle of the photon correlation method, and particle characteristics such as the particle diameter and number of particles have been measured. For example, when measuring impurities in pure water, the particle size of the particles being measured is small;
Moreover, it is difficult because the particles exist only sparsely. Conventionally, in order to increase the intensity of scattering from fine particles, the incident light beam is focused on a small area, a high-intensity measurement area is created, and the method passes through this area. A method of receiving scattered light from particles is used. For example, such a method is used in ultrafine particle counters that detect impurities in pure water.

[Problems to be solved by the invention] As described above, in the conventional method, because the target was a group of particles with a high particle number density, it was not possible to perform particle measurement that could sufficiently measure the properties of a population of particles in a small measurement area. However, for example, when measuring impurity fine particles in pure water, the fine particle density is in a diluted state, and therefore it becomes necessary to increase the treated value of the pure water to be measured. For this reason, in the past, the cross-sectional area of pure water passing through was several hundred times larger than the cross-sectional area of the measurement area, and the particles being measured were only a small fraction of the particles that actually passed through, making them pure in a short time. The problem is that it is not possible to measure a sufficient number of particles to reflect the quality of the water itself. In particular, when measuring fine particles in pure water with a low particle number density and inspecting the quality of the pure water, it is desirable to be able to inspect all the fine particles in the pure water.

Therefore, the present invention was devised in view of these points, and provides a particle measuring method and device capable of accurately measuring the particle size and number of particles even if the particle number density is low. The purpose is to provide.

[Means for Solving the Problems] In order to solve these problems, the present invention performs measurement by reciprocating a light beam from a coherent light source such as a laser light source multiple times in a measurement region where particles to be measured are present. We adopted a configuration in which a region is covered with a coherent light beam and the scattered light from the coherent light beam is measured.

[Function] In such a configuration, the laser beam is a coherent light beam with high directivity and low diffusivity.
By reflecting the light multiple times in the measurement area, it becomes possible to cover the measurement area with a coherent light beam, and it becomes possible to effectively irradiate the particles over the entire measurement area, making it possible to perform accurate measurements.

Examples] The present invention will be described in detail below according to embodiments shown in the drawings.

FIG. 1 shows a schematic configuration of a measuring device for measuring the characteristics of fine particles such as impurity particles in pure water. In the figure, the reference numeral 1 indicates a coherent light source, for example a laser light source, and this laser light source 1 emits a coherent laser beam 1a from its front surface. A light beam 1a emitted from this laser light source 1 passes through the air and enters a first side surface 3 of a glassy flow cell 2. Pure water flows into this flow cell 2 from the upper part as shown by arrow A and flows out to the lower part. This pure water contains impurity particles 20 to be measured. The laser beam incident on the first side surface 3 of the flow cell 2 is refracted by the wall surface and transmitted into the pure water. If there are scattering particles, part of the laser beam transmitted through pure water is scattered, and most of the remainder reaches the second side 4 opposite the first side 3 of the flow cell and is refracted. and exit the flow cell. flow cell 2
A first reflecting mirror 5 is disposed close to the second side surface 4 of the flow cell 2, and a second reflecting mirror 6 is disposed on the first side surface 3 of the flow cell 2, that is, on the laser light source 1 side.

The laser beam that reaches the second side surface 4 and is refracted and exits the flow cell 2 is reflected by the first reflecting mirror 5 according to its reflectance, enters the second side surface 4 of the flow cell 2, and is refracted. The light passes through the pure water again, and if there are any fine particles, a portion of the light is reflected by the fine particles, and the light is reflected from the first side surface 3 of the flow cell.
reach.

The light flux transmitted through the first side surface 3 is incident on the second reflecting mirror 6, is reflected according to its reflectance, and is incident on the first side surface 3 of the flow cell 2 again. Thereafter, through the same process, several laser beams 1a are formed which go back and forth between the two reflecting mirrors 5.6 and pass through the flow cell 2, and finally the laser beam 1a
is captured by the optical trap 7 and absorbed so as not to be emitted again.

Preferably, a light receiving lens 9 is disposed facing the first and second side surfaces of the flow cell 2 and the face 8 facing east. flow cell 2
The laser beam scattered by the scattering particle group 20 floating in the pure water in the flow cell passes through the transparent third side surface 8 of the flow cell, and passes through the light receiving lens 9 installed in a direction substantially perpendicular to the beam.
An image is formed on the light-receiving surface 10a of the photomultiplier tube 10.

At this time, the laser beam 1 is reciprocating within the flow cell 2.
Since a maintains a coherent state, the scattered light from particles in different light fluxes also becomes coherent and can interfere with each other, so the fluctuation of the scattered light depending on the Brownian motion of each particle is reflected in the photomultiplier tube. is detected by the photocathode 10a. As is well known, this fluctuation in light intensity is photoelectrically converted by a photomultiplier tube 10, processed as an electrical signal by a processing circuit 11, and inputted to a correlator 12 connected at the subsequent stage. The correlator 12 determines a correlation function between the fluctuation of light intensity and the characteristics of the particles, and the microcomputer 13 calculates this into the diffusion coefficient and particle diameter of the particles.

In the above example, the measurement area is 1, for example, IOX 10 m, the depth is 10 m, the distance from the flow cell to the lens 9 is 100 m, the distance from the lens 9 to the light extraction surface 10a is 100 + * m, and the distance from the flow cell to the lens 9 is 100 m. The focal length of is 50 mm.

FIG. 2 shows the configuration of the measuring section in more detail. As shown in FIG. 1, reflecting mirrors 5 and 6 are disposed facing each other in the air on both sides of the flow cell 2 made of transparent glass, and the incident angle of the laser beam la and the flow cell wall surface and each reflecting mirror are arranged opposite to each other in the air. The interval of 5°6 is set so that the area B where the light flux incident on each reflecting mirror 5.6 and the reflected light flux intersect and interfere does not enter the pure water flow path in the 20-cell. shall be. In other words, in the example shown in the upper part of Figure 2, this condition is satisfied, and the refractive index of air is set to 1.
, the refractive index of the flow cell wall is 1.4. The refractive index inside the flow cell is 1.33, the thickness of the flow cell wall is 5 m, the distance inside the flow cell is 10 mm, and the distance between the reflector and the wall is 4.
011■, assuming the diameter of the laser beam is 14 amφ, an incident angle of 10 or more is required, and in the lower part of Fig. 2, the intersecting and interfering region B enters the pure water flow path, so the incident angle of the laser beam is This is an example of being too small.

In the device shown in FIG. 2, a large difference in refractive index occurs on the outer wall surface of the flow cell in contact with air, which reduces the transmittance of the light beam and increases the attenuation of the light beam.
This has the advantage that the flow cell can be replaced independently of the reflector.

On the other hand, a device for reducing the attenuation of the luminous flux is shown in FIG. In the example shown in Figure 3, a transparent flow cell 2
Reflective layers 21 and 22 are provided on outer walls 23 and 24, respectively. In the case of this embodiment, as shown in FIG. 2, there is no air layer between the reflective surface and the outer wall of the flow cell.
Prevents light flux from attenuating. Also in the case of the embodiment shown in FIG. 3, the incident angle of the laser beam is set so that the area B where the incident light and reflected light intersect and interfere does not enter the pure flow path.

In this case, each refractive index is the same as shown in Figure 2, the thickness of the glass wall of the flow cell is 61 mm, the space between the flow cells is ioam, the laser beam diameter is 1.4 mm, and the incident angle is 10 or more. Become.

As described above, in the present invention, a plurality of groups of light beams are formed in the measurement area from one laser light source using a reflection means so that the group of laser beams covers the entire cross section of the pure water flow path, which is the measurement area of fine particles. However, as mentioned above, the setting must be made so that the incident light weight and the reflected light flux do not intersect inside the flow cell, so the distance between each light flux la is as shown in Figure 4 (A).
As shown in the figure, there will be some gaps. However, as shown in FIG. 4(B), by tilting the laser beam group 1a by, for example, 45 degrees with respect to the flow direction A, it is possible to make this gap C appear to disappear. In other words, by tilting the laser beam group with respect to the flow direction A, the gap C shown in FIG. It is not possible to form a laser beam group in the measurement area, resulting in a hole. Such a method can be applied to either of the two devices illustrated in FIGS. 2 and 3.

[Effects of the Invention] As explained above, according to the present invention, the laser beam is reciprocated multiple times in the region where the particles to be measured are present, so that all fixed regions are covered with a coherent light beam, so that the photon correlation method is not possible. This makes it possible to measure particle groups with high precision at a dilute density, making it possible to measure ultra-dilute particles in a short time and to capture particle groups that reflect the statistics of the population of particle groups. You can get this excellent effect.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram illustrating the method of the present invention, FIG. 2 is a sectional view illustrating a more detailed configuration of the measuring section, and FIG. 3 is a sectional diagram showing another embodiment of the measuring section. Figure 4 (A), (
B) is an explanatory diagram illustrating an example in which the laser beam is tilted with respect to the direction of particle flow. l... Laser beam 2... Flow cell 5.6.
...Reflection tI2.7...Light trap 20...Particle patent applicant Kowa Co., Ltd. 4-11 Agent Patent attorney Taku Kato ゛ 1 Figure 3

Claims (1)

[Scope of Claims] 1) A particle measurement method in which a particle to be measured is irradiated with a light beam from a coherent light source and scattered light from the particle is measured to measure the characteristics of the particle. A particle measurement method characterized by covering the measurement area with a coherent light beam by reciprocating the measurement area multiple times and measuring scattered light from the coherent light beam. 2) The particle measuring method according to claim 1, characterized in that the light flux is reciprocated so as not to overlap at least in the measurement area. 3) In a particle measuring device that measures the characteristics of the particles by irradiating the particles to be measured with a light beam from a coherent light source and measuring the scattered light from the particles, the first and second reflecting means are placed across the measurement area. and multiple reflections of the light beam from the coherent light source between the first and second reflecting means to cause the coherent light beam to reciprocate a plurality of times in the measurement area and measure scattered light from the coherent light beam. A particle measuring device featuring: