JPS6318244A - Method and apparatus for measuring fine particle in liquid - Google Patents

Abstract

PURPOSE:To achieve a high trapping rate of a particle image, by a method wherein a laser luminous flux employs an oval luminous flux and scattered light from fine particle passing through a particle detection area formed by this flux is received from the direction of the particle passes to measure characteristic of the particle. CONSTITUTION:A sample liquid 22 flowing from an inflow tube 12 flows along a cylinder section 10a of a measuring cell 10 and a part thereof flows out of an outflow tube 13. An oval laser luminous flux 21 is focused at the center of the cylinder section 10a and on an intermediate area of the wall surface of the cylinder. Then, the particle passes through a particle detection area vertical to optical axis of the luminous flux 21 on the flow of the sample liquid 22 within the cylinder. Scattered light 24 from the particle forms an image on a mask surface 26 through a light receiving lens 25 and reaches an photoelectric detector 27 as limited by a slit 26a to measure. Thus, a higher trapping rate of the particle image can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for determining fine particles in a liquid. The present invention relates to a method and apparatus for measuring fine particles in liquid, which detects scattered light of particles and measures particle characteristics such as particle size and number of particles.

[Prior Art] Conventionally, there is a known technique for measuring characteristics such as the particle size and a of particles in the measurement area by making light incident on the measurement area and determining the amount of transmitted light and scattering characteristics. There is.

For example, this technology is used to measure impurity particles in pure water, but since the particles in pure water are small in diameter and only sparsely present, measurement is difficult. Conventionally, in order to increase the intensity of scattering from particles, there has been a method of focusing the incident light beam from a laser light source, etc. on a small area, creating a high-brightness measurement area, and receiving the scattered light from particles passing through this area. It is used.

In particle measuring instruments that irradiate particles with laser light and analyze scattered light from the particles, it is important to determine how to set the measurement section through which the particles pass.

In particular, the shape of the incident laser beam constituting the particle detection area 1. The direction of particle passage and the setting method of the mask provided at the part that receives the scattered light from the particles is the flow diameter when determining the particle size from the scattered light of the particles to be detected. Since it depends directly on the resolution, various efforts have been made.

FIG. 6 shows an example of setting a particle detection area used for the purpose of increasing particle detection efficiency. A laser beam 21 is incident on a square prism transparent cell 20 through a cylindrical lens 30 to form a sheet-like beam over the entire cross section of the cell.

A sample liquid (for example, pure water) containing fine particles 23 is placed in this cell 20.
, scattered light 24 is obtained from particles passing through the condensing sphere (entire #11 part) 21a where the laser beam is condensed. This scattered light 24 passes through a light receiving lens 25 and is sent to a photoelectric detector 2.
7, the particle diameter is calculated from the intensity of the scattered light, and the particle characteristics are determined.

[Problems to be Solved by the Invention] When a sample liquid is caused to flow through this cell, particles in the liquid scatter laser light each time they pass through the cross section of the cell, regardless of their position.

However, as the particle diameter becomes smaller than submicrons, the scattered light from a single particle becomes weaker, so the sheet-shaped light beam described above has insufficient light intensity density and is not suitable for detecting fine particles.On the other hand, the method of focusing the laser beam in a circular manner Although it is possible to increase the light intensity density on the cross section at the focal point, it is not possible to increase the cross-sectional area through which particles pass.

The present invention increases the particle capture rate without reducing the laser beam intensity, and shortens the passing distance of the particle detection area, making it possible to sharply change the intensity of scattered light as the particles pass, thereby making it more conspicuous. It is an object of the present invention to provide a method and apparatus for determining fine particles in liquid.

[Means for Solving the Problem] In order to solve this problem, the present invention uses an elliptical beam as the laser beam and detects scattered light from fine particles passing through a particle detection area formed by the laser beam. We adopted a configuration that measures particle characteristics by receiving light from the direction in which the particles pass.

[Function] With such a configuration, the cross-sectional area perpendicular to the particle passing direction can be increased without reducing the light intensity density of the laser beam at the focal point, and effective particle detection becomes possible.

[Example] Hereinafter, the present invention will be described in detail according to an example shown in the drawings.

In order to achieve the object of the present invention, one condition is that an elliptical light beam is used as the incident light beam, and the second condition is that the scattered light of the particles passing through the formed particle detection area is received from the direction in which the particles pass. Make sure to satisfy the following.

Figure 1 shows an example of setting a particle detection area that satisfies the above conditions.Of the double circles indicating the elliptical luminous flux l, the outer circle indicates the position where the light intensity of the luminous flux becomes l/e2 of the central intensity. , the diameter of this outer circle is usually called the diameter of the luminous flux. On the other hand, the inner circle indicates the position where the intensity of the luminous flux becomes 172 of the center intensity, and this diameter is called the full width at half maximum of the luminous flux. Scattered light 3 from the passing particles is received by the light receiving lens 25 and formed into an image on the pickpocket 7) 26a, and is received by the photoelectric detector 27 and captured as an electrical signal. At this time, the area limited by the slit 26a and effective for detecting particles is the full width at half maximum area 2 shown by the shaded area in the figure, but the light flux 1 in the depth F direction is
Since the thickness is small, the light intensity distribution 4 becomes steep, and the actual detection area becomes shallow in the depth direction.

The shape and size of the detection area 2 can be determined by matching the passing direction A of the zero particles, which is determined by the F value of the light receiving lens 25, the focal length 1 magnification, the #A of the slit 26a, etc., with the direction of the depth F. The laser light intensity can be limited to the effective luminous flux range E, allowing for even more accurate detection.

The shape of the particle detection area is a as shown in Fig. 2.

It is characterized by three lengths, b and c. a and b indicate the diameter of the elliptical luminous flux 21 at its condensing point, and C indicates the length in the optical axis direction. When the light intensity of the luminous flux is expressed as Wb2 and the amount of scattered light from the sample liquid within the effective particle detection area is W, the amount of scattered light from the passing particles is W, then it is expressed as zone=-b WbDC×abC QC1.

Therefore, the ratio of the amount of scattered light from the particles to the amount of scattered light from the sample liquid is calculated.When the SIN of the signal from the particles is constant, increasing the particle capture rate requires increasing the bc value, that is, a.
You can set it small.

3 to 5 show an embodiment of the device of the present invention, and in the figures, the reference numeral 10 indicates a measuring cell, which has a cylindrical portion 10a, around which a laser beam is incident. Window 16. Exit window 17. A light receiving window 18 for scattered light and a wall antireflection window 19 are arranged. The I14 constant cell 10 is provided with an inflow pipe 12 through which a sample liquid 22 such as pure water containing fine particles 23 to be measured flows in, and an outflow pipe 13 through which the sample liquid 22 is discharged from the measurement cell lo.

An elliptical laser beam 21 is produced by the configuration shown in FIG. Laser light from a laser light source 31 is expanded through a beam expander 32, and a cylindrical lens 33 generates an elliptical light beam. The light passes through the condenser lens 34 and is condensed onto the condensing point 21a. The vicinity of this condensing point 21a is a particle detection area 35, and the laser beam is horizontally flat in the front and rear of the detection area bl and b5, but in the detection areas b2 and b3
.

At b4, the light beam is vertically flat.

The elliptical laser beam 21 thus formed passes through the entrance window 16 and is condensed onto a condensing point 21a.

The light is emitted through the exit window 17. As shown in FIG. 4, a flow shown by A is formed such that the particles pass perpendicularly to the laser optical axis. This --like flow is caused by the cylindrical portion 20a.
It can also be formed by creating a circulating flow using suitable stirring means.

With such a configuration, the sample liquid 22 flowing in from the inflow pipe 12
flows along the cylindrical portion 10a of the measurement cell 10, and a portion of it flows out from the outflow pipe 13. In this example, the elliptical laser beam 21 is transmitted between the center of the cylindrical portion 10a and the intermediate region 2 between the cylindrical wall surface.
The zero particles focused on 1a ride on the flow of the sample liquid in the cylinder and pass through the particle detection area perpendicular to the optical axis of the laser beam.The scattered light 24 from the six particles is focused on the mask surface 26 by the light receiving lens 25. The scattered light that is imaged and restricted by the pickpocket 7) 26a reaches the photoelectric detector 27 and is measured.

[Effects] As explained above, in the present invention, an elliptical beam is used as a laser beam, and scattered light from fine particles passing through a particle detection area formed by this laser beam is received from the direction of passage of the particles to detect particles. Since the characteristics of the particle are measured, the cross-sectional area of the particle detection area perpendicular to the direction in which the particles pass can be increased while maintaining the light intensity of the laser beam, increasing the capture rate of particle images. It becomes possible to set a detection area suitable for detection.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram illustrating an example of setting the particle detection area, FIG. 2 is an explanatory diagram showing the shape of the particle detection area, FIG. 3 is a perspective view showing the configuration of an embodiment of the device of the present invention, and FIG. Figure 3 is a sectional view of the device, Figure 5 is a configuration diagram of the elliptical beam forming device, and Figure 6 is a cross-sectional view of the device.
The figure is an explanatory diagram of a method using a sheet-like light beam.

Claims (1)

[Claims] 1) In a method for measuring particles in liquid, in which particle characteristics are measured by irradiating a laser beam into a fluid and detecting scattered light from particles floating in the liquid, an elliptical beam is added to the laser beam. A method for measuring fine particles in liquid, characterized in that the characteristics of the particles are measured by receiving scattered light from the fine particles passing through a particle detection area formed by the laser beam from the direction in which the particles pass. 2) The aspect ratio of the elliptical luminous flux is set so as to increase the cross-sectional area perpendicular to the direction in which the particles pass and to shallow the particle detection depth in the passing direction. Method for measuring fine particles in liquid. 3) In a liquid particle measurement device that measures particle characteristics by irradiating a laser beam into a fluid and detecting the scattered light from particles suspended in the liquid, measurement is performed in which a sample liquid containing the particles to be measured is placed. a cell, means for generating an elliptical laser beam, means for generating a flow that causes particles to pass in a direction perpendicular to the laser optical axis to a particle detection area in the measurement cell where the elliptical laser beam is focused, and in the direction of the flow. What is claimed is: 1. An in-liquid particulate measuring device, comprising: an optical system that receives scattered light from the particulates, and measures particle characteristics by receiving scattered light from the particulates from a direction in which the particles pass.