JPH04323540A - Particle size distribution measuring device - Google Patents

Abstract

PURPOSE:To provide a particle size distribution measuring device in which a scattered light measuring cell is so disposed to prevent lowering of scattered light due to particles of micro particle size. CONSTITUTION:A particle size distribution measuring device includes a laser light emission means 2, a scattered light measuring cell 4 disposed on the ongoing optical axis of laser light emitted from the laser light emission means 2, and a scattered light measuring means comprising a light collecting lens 5 for collecting scattered light and a detection light-receiving element 6 for measuring the intensity of the scattered light. The light emission face of the scattered light measuring cell 4 is so disposed to have an angle of inclination with respect to the ongoing optical axis of the laser light.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particle size distribution measuring device. More specifically, the present invention relates to a particle size distribution measuring device in which a scattered light measuring cell is arranged so as to efficiently transmit scattered light caused by particles having a minute particle size.

0002

[Prior Art and Problems to be Solved by the Invention] In recent years, ultrafine particles have attracted attention in the manufacturing process of ceramic raw materials, superconducting materials, magnetic materials, etc., or in the manufacturing process of semiconductors. There is an increasing need to measure the particle size of micron particles.

[0003] Generally, an optical particle size distribution measuring device is used to measure the diameter or particle size distribution of these microparticles. The optical particle size distribution measuring device collects scattered light generated by irradiating a group of particles to be measured housed in a scattered light measurement cell with a laser beam using an optical lens, and focuses the scattered light on the focal plane of the lens. The distribution of the scattered light intensity with respect to the scattering angle is determined from the intensity distribution of the scattered light measured by the detection light receiving element, and the particle size distribution is determined from the analysis. This particle size distribution is calculated based on Mie's scattering theory by measuring the intensity distribution of scattered light.

When measuring the intensity of scattered light from particles to be measured using a particle size distribution measuring device, if the particle size of the particles to be measured is sufficiently larger than the wavelength of the laser beam used for measurement, the intensity of the scattered light from the incident particle of the laser beam is measured. Scattered light concentrated in a small angular range occurs. However, when the particle size of the particles to be measured is small with respect to the laser beam, the range of scattering angles at which the laser beam is scattered is large, and accordingly, the scattered light is The angle of incidence also becomes large. Therefore, the light reflectance on the inner wall surface of the emission surface of the cell for measuring scattered light increases, and the transmittance of the scattered light to be measured decreases. Furthermore, generally when the particle size of the particles to be measured is less than the wavelength of the laser beam, the amount of scattered light decreases rapidly. Therefore, when particles having a minute particle size are present as particles to be measured, there is little scattered light due to the particles having the minute particle size measured by the detection light receiving element, so the detection light receiving element and the particle size distribution are The S/N ratio is poor compared to the noise generated in the circuit of the analysis system, making it impossible to accurately measure the scattered light intensity, and inevitably making it impossible to measure the particle size distribution with high precision.

On the other hand, in technical fields that handle various particles, it is necessary to measure with high precision the particle size distribution of particles whose diameter is minute compared to the wavelength of the laser light used for measurement. .

The present invention has been made based on the above circumstances. That is, an object of the present invention is to provide a particle size distribution measuring device in which a scattered light measuring cell is arranged so as to prevent a reduction in scattered light due to particles having a micro particle size.

[0007]

[Means for Solving the Problems] The present invention as set forth in claim 1 to achieve the above object provides a laser beam irradiation means for irradiating parallel laser beams, and a suspension in which particles to be measured are dispersed. A scattered light measurement cell that stores a liquid, a detection light receiving element disposed in front of the scattered light measurement cell to measure the intensity of the scattered light by the particles to be measured, and a detection light receiving element that receives the scattered light. a scattered light measuring means consisting of a condensing lens for condensing the light onto the element surface, and the output surface of the scattered light measuring cell is inclined with respect to the traveling optical axis of the laser beam irradiated from the laser beam irradiating means. A particle size distribution measuring device characterized in that the particle size distribution measuring device is arranged so as to

[0008]

[Operation] When measuring particle size distribution using a particle size distribution measuring device, if the particle size of the particles to be measured is sufficiently large compared to the wavelength of the laser used for measurement, scattered light will be concentrated in a small angular range. However, when the particle size is minute compared to the wavelength, the range of scattering angles scattered by the laser beam becomes large. Generally, the transmittance (π) of light at an interface is determined by the angle of incidence (θw), the angle of exit (θg),
It is expressed as follows using the refractive index (n1) of the light propagation medium up to the interface and the refractive index (n2) of the light propagation medium after passing through the interface.

π=4 (n1/cosθw) (n2/co
sθg)/{(n1/cosθw)+(n2/cos
θg)}2 The transmittance (πA) at which the scattered light passes through the emission surface of the scattered light measurement cell is determined by the difference between the sample liquid containing the particles to be measured and the scattered light measurement cell stored inside the scattered light measurement cell. Based on the transmittance (πB) at the interface with the emission surface of the cell for measuring scattered light and the transmittance (πC) at the interface between the emission surface of the cell for scattered light measurement and the air outside the cell for scattered light measurement, πA = π
It is expressed as B・πC. The intensity (I) of the scattered light is corrected by this transmittance (πA), but as the scattering angle increases and approaches the critical angle, the amount of reflected light increases and the amount of transmitted light decreases.

In the present invention, the exit surface of the cell for measuring scattered light is
By arranging it at an angle with respect to the traveling optical axis of the irradiated laser beam, even if the scattered light has a large scattering angle, the incident angle at the emission surface of the scattered light measurement cell can be made small, reducing the amount of scattered light. It is possible to prevent this.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. 1 and 2 are schematic plan views of an embodiment of the particle size distribution measuring device of the present invention viewed from above, respectively.
The particle size distribution measuring device of the present invention is not limited to the embodiments shown in FIGS. 1 and 2. The particle size distribution measuring device 1 of the present invention shown in FIG.
, a scattered light measuring cell 4 disposed on the traveling optical axis of the laser beam irradiated from the laser beam irradiation means 2, a condensing lens 5 for condensing the scattered light, and measuring the intensity of the scattered light. The scattered light measurement cell 4 is arranged such that its output surface has an inclination angle with respect to the traveling optical axis.

Furthermore, the particle size distribution measuring device 1 of the present invention shown in FIG. In addition, a scattered light measurement system including a condenser lens 5 and a detection light receiving element 6 is provided on the normal line of the exit surface.

(1) Laser beam irradiation means The laser beam irradiation means 2 comprises a laser light source (not shown), a laser beam oscillation device (not shown), and a collimator 3 for collimating the output laser beam. The laser light source and the laser light oscillation device may be conventionally known ones, and the laser light that can be output by the laser light oscillation device includes:
For example, 632.8 nm laser light from a He-Ne gas laser, 680-780 nm laser light from a semiconductor laser, etc. can be used. The collimator 3 is composed of a plurality of lens groups (not shown), and adjusts the beam diameter of the laser beam output from the laser beam transmitting device, and converts the laser beam into a parallel beam.

(2) Scattered light measurement cell The scattered light measurement cell 4 is disposed in the optical path of the laser beam made into a parallel beam by the collimator 3, and is a suspension formed by dispersing particles to be measured in a medium. However, from a storage tank (not shown),
It is configured as a flow cell that can flow in through piping (not shown). The material forming the scattered light measurement cell is not particularly limited, and conventionally known glasses such as Pyrex glass and quartz glass can be used.

[0015] Usually, the shape of the scattered light measurement cell is a hexahedron formed by three sets of opposing faces that are parallel to each other. In the scattered light measuring cell of the present invention, the incident surface of the laser beam outputted from the laser beam irradiation means, which is one of the three opposing pairs, and the exit surface of the scattered light scattered by the sample particles are arranged such that the laser beam It has a predetermined inclination angle with respect to the traveling optical axis of the laser beam irradiated from the irradiation means 2. The predetermined angle of inclination is in the range of 0° to 60°.

(3) Scattered light measurement system The scattered light measurement system includes a detection light-receiving element 6 disposed to measure the intensity of scattered light by the particles to be measured, and a detection light-receiving element 6 that directs the scattered light onto the detection light-receiving element 6. Condensing lens 5 to condense light
Consisted of. In the scattered light measurement system, the central optical axis of the scattered light focused by the condensing lens 5 and the traveling optical axis of the laser light irradiated from the laser light irradiation means 2 are aligned with the inclination of the emission surface of the scattered light measurement cell. It is arranged in a range forming an angle of 0° to 90° with respect to the direction, preferably in a range formed by the traveling optical axis and the normal line of the emission surface of the scattered light measurement cell.

The detection light receiving element 6 is placed on the opposite side of the condensing lens 5 from the scattered light measurement cell 4. The detection light-receiving element 6 is a group of photoelectric conversion elements (for example, photodiodes, etc.) having a plurality of light-receiving surfaces arranged in a direction perpendicular to the optical axis of the scattered light collected by the condenser lens 5.
It is formed from. The intensity of the scattered light generated by the particles to be measured in the scattered light measurement cell 4 is symmetrical with respect to the optical axis center of the scattered light collected by the condenser lens 5. Therefore, the detection light receiving element 6 includes a central photoelectric conversion element that receives the central optical axis of the scattered light collected by the condensing lens 5, and other photoelectric conversion elements arranged in a line in one direction from the central photoelectric conversion element. It is composed of a group of photoelectric conversion elements. Normally, after light-receiving elements for detection are formed in sections on a semiconductor wafer using semiconductor technology, the semiconductor wafer is cut and used as a detector for measuring the intensity of scattered light in a particle size distribution measuring device.

(4) Particle Size Distribution Analysis System The particle size distribution analysis system in the particle size distribution measuring apparatus is composed of a multiplexer, an amplifier, an A/D converter, an arithmetic control device, an output device, etc., all of which are not shown. The multiplexer is a switch that switches electrical signals output from each photoelectric conversion element group that constitutes the detection light receiving element. The detection signal output from the multiplexer is amplified by an amplifier, converted into a digital signal by an A/D converter, and then output to an arithmetic and control unit. The arithmetic and control device calculates a particle size distribution based on data indicating the measured scattered light intensity and scattering angle based on the well-known Fraunhofer diffraction theory and Mie's scattering theory. The particle size distribution data calculated by the arithmetic and control device is transferred to, for example, a CRT, XY
Output to an output device such as a plotter.

(5) Method for Measuring Particle Size Distribution Next, the measurement of particle size distribution using the particle size distribution measuring device 1 of the present invention will be explained. First, the scattered light measurement cell 4 is filled with a sample solution in which particles to be measured are suspended in water. Next, the laser beam irradiation means 2
A collimator 3 converts the laser beam oscillated into a parallel beam of light, and irradiates the scattered light measurement cell 4 with the collimated beam.

The laser light irradiated onto the scattered light measurement cell 4 is scattered by the particles to be measured suspended in the scattered light measurement cell 4. The emission surface of the scattered light measurement cell 4 is
Since it is inclined with respect to the traveling optical axis of the laser beam irradiated from the laser irradiation means 2, even if the particle size of the particle to be measured is minute compared to the wavelength of the laser beam, it will not be scattered by the particle to be measured. The generated scattered light is converged by the condenser lens 5 and irradiated onto the detection light receiving element 6 without being attenuated. In the detection light-receiving element 6, a plurality of photoelectric conversion elements are arranged in a line in a direction perpendicular to the traveling optical axis of the converged scattered light, so that the electrical signal output from each photoelectric conversion element is the same as the scattered light. In addition, the scattering angle is determined based on the position of the photoelectric conversion element.

The electrical signals output from each photoelectric conversion element in the detection light receiving element 6 are amplified by an amplifier via a multiplexer, and then converted into a digital signal by an A/D converter. Further, the calculation control section calculates the particle size distribution of the particles from the intensity and scattering angle of the scattered light, and the calculated particle size distribution is output from the output device.

[0022]

According to the particle size distribution measuring device of the present invention, the scattered light measuring cell is arranged such that the emission surface is inclined with respect to the traveling optical axis of the laser beam irradiated from the laser beam irradiation means. , it is possible to efficiently transmit scattered light generated by particles having a particle size smaller than the wavelength of the laser beam.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a particle size distribution measuring device of the present invention.

FIG. 2 is a schematic diagram showing an embodiment of the particle size distribution measuring device of the present invention.

[Explanation of symbols]

1 Particle size distribution measuring device 2 Laser light irradiation means 3 Collimator 4 Scattered light measurement cell 5 Condensing lens 6 Detection light receiving element

Claims (1)

[Claims] Claim 1: A laser beam irradiation means for irradiating parallel laser beams, a scattered light measurement cell containing a suspension obtained by dispersing particles to be measured, and a cell for measuring scattered light by the particles to be measured. Scattered light measuring means comprising a detection light receiving element disposed in front of the scattered light measuring cell and a condensing lens for condensing the scattered light onto the surface of the detection light receiving element, A particle size distribution measuring device characterized in that the emission surface of the scattered light measuring cell is arranged so as to be inclined with respect to the traveling optical axis of the laser beam irradiated from the light irradiating means.