JPH0260975B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a particle size measuring device for measuring the diameter of minute particles.

(Conventional technology) One of the conventional particle size measuring devices that utilizes light scattering.
There is a device as shown in FIG. This is done by irradiating a sample with laser light, measuring the distribution I(θ) of the light scattered by the sample in the θ direction, and using diffraction theory or Mie scattering theory to calculate the particle size distribution n( D) (D: particle size). Scattering distribution i(D,
θ) can be determined by diffraction theory or Mie scattering theory, so if the particle size distribution of the sample is n(D), the scattered light distribution I(θ) is I(θ) = ∫i(D, θ)・n(D)dD...It can be expressed as equation (1). (1) can be solved for n(D), and the particle size distribution n(D) can be calculated using a lognormal distribution.
Assuming Rosin-Rammler distribution, the particle size distribution of the sample is determined by calculating its distribution parameters using equation (1).

This conventional method requires that the laser beam 1 be a coherent beam, and as shown in FIG. 2, the scattered light from the sample is focused on the focal plane of the lens using a light receiving lens 4. This does not depend on the position of the sample, and all light whose scattering angle is θ is γ at the focal plane.
This is to focus the light on the position of ≒θ _f . In such an optical system, since there is a limit to the aperture of the lens, the range in which the scattered light distribution can be measured is limited to within 0 to 15 degrees. When the range of the scattered light distribution is limited to 0 to 15 degrees, it is difficult to relatively distinguish the scattered light distribution of relatively small particles of 1.0 μm or less, as shown in FIG. Furthermore, it has various drawbacks, such as the fact that the light source must be coherent light.

(Problem to be solved by the invention) As mentioned above, in the conventional particle size measuring device,
Since the range of scattered light distribution is limited, it is difficult to obtain the scattered light distribution of relatively small particles.
Furthermore, the light source is also limited.

Therefore, an object of the present invention is to create a particle that can measure the scattered light distribution in any scattering angle range, so that the particle size can be determined even in a relatively small particle size region without being limited by the light source. An object of the present invention is to provide a diameter measuring device.

[Structure of the Invention] (Means for Solving the Problems) FIG. 4 shows the scattered light distribution in the range of scattering angles from 0 to 180 degrees. As shown in the figure, if the scattering angle is set wide or larger than 40°, the scattered light distribution due to particles of 1.0 μm or less can be relatively distinguished, and 1.0 μm
It is possible to measure particle sizes of m or less.

The present invention has been made from the above viewpoint,
The particle size measuring device of the present invention that solves the above problems includes a light source that emits monochromatic light, and a sample that is composed of a plurality of particles whose particle size is to be measured. A light receiving system that measures only the light that is parallel to the optical axis of the lens and is arranged in multiple directions in the direction of the scattering angle of the scattered light of the sample, and a scattered light intensity distribution of the sample measured by this light receiving system and a a signal processing system that determines the particle size distribution of the sample by comparing the scattered light intensity distribution for each different particle size of a plurality of particles being sought; a light source that emits monochromatic light; and a light source that emits monochromatic light; A light receiving system that irradiates a sample consisting of a plurality of particles to be measured with monochromatic light from the light source and measures only the light parallel to the optical axis of the lens among the scattered light scattered from the sample; a driving device that scans the scattered light of the sample in the direction of the scattering angle; a scattered light intensity distribution of the sample measured by the light receiving system; and a predetermined scattered light intensity distribution for each different particle size of a plurality of particles; and a signal processing system that collates the data to determine the particle size distribution of the sample.

(Function) In the particle measuring device of the present invention, monochromatic incoherent light (coherent light may be used) such as a laser is used as a light source, and the intensity distribution of scattered light by a large number of particles in the scattering angle direction (scattered light intensity distribution) The particle size distribution is determined by measuring and comparing it with the scattered light intensity distribution (for example, Figure 4) from particles of various particle sizes stored in the signal processing system (computing device such as a personal computer) in advance. It is something.

Thereby, the scattered light distribution can be determined over a wide range without restrictions on the light source.

(Example) A first example of the present invention will be described based on FIG. 5. Beam 1 shaped by incoherent and monochromatic laser 1 and beam shaping system 2
2 is irradiated onto a sample 3, and the light scattered by the sample is detected by a light receiving system comprising a light receiving lens 9, a pinhole 40, and a photodetector 6. After the signal is amplified by the amplifier 7, the intensity distribution of this scattered light is collated by the signal processing system 8, which stores the scattered light intensity distribution by particles of various particle sizes as data, as shown in Fig. 4. This allows the particle size distribution to be determined.

The present invention is based on the Mie scattering theory, and the particle size distribution is determined from the intensity of scattered light when particles are located at random positions. It was decided that the measurement could be performed using a photodetector placed at an angle θ. When determining the particle size distribution, it is necessary to calculate the scattered light intensity i (D, θ) by one particle when irradiated with incoherent light based on the Mie scattering theory.

Figure 6 shows the light receiving system. In the light receiving system, a pinhole 10 is placed at the focal point of the light receiving lens 9, and a photodetector 6 is placed after that, so that only the scattered light parallel to the optical axis of the light receiving lens 9, that is, only the light scattered at the scattering angle θ, is transmitted to the photodetector 6. Set to input. If this light receiving system is scanned in the direction of the scattering angle by the driving device 11, the scattering distribution for any range of scattered light can be measured since it is not affected by the position of the sample.

In the embodiment shown in FIG. 7, a large number of light receiving systems are arranged in the direction of the scattering angle, and even with this configuration, a similar scattered light distribution can be obtained and the driving device 11 is not required.

FIG. 8 shows an example in which an optical fiber is used for the light receiving system, and by configuring it in this way, flexibility can be provided in the arrangement of the light receiving system. Therefore, the particle size can be measured in various environments such as water droplets in a turbine.

[Effects of the Invention] As is clear from the above explanation, if the present invention is used, incoherent light can be used and the scattered light distribution can be determined over a wide range, so small particle diameters of 1.0 μm or less can be obtained. It is possible to achieve excellent effects such as making it possible to measure even

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the conventional method, Fig. 2 is a schematic diagram for explaining the conventional light receiving system, Figs. 3 and 4 are characteristic diagrams showing the scattered light distribution, and Fig. 5 is the invention of the present invention. FIG. 6 is a schematic diagram for explaining the optical system of the first embodiment. FIG. 7 is a schematic diagram showing the second embodiment of the present invention.
It is a schematic diagram showing a third example of the present invention. 1... Laser, 2... Beam shaping system, 3...
Sample, 4, 9, 9', 9''... Light receiving lens, 5, 1
1... Drive device, 6, 6', 6"... Photo detector, 7, 7', 7"... Amplifier, 8... Signal processing system, 10... Pinhole, 12... Beam (laser beam), 13, 13', 13'', ... optical fiber.

Claims (1)

[Scope of Claims] 1. A light source that emits monochromatic light and a sample consisting of a plurality of particles whose particle size is to be measured is irradiated with monochromatic light from the light source, and among the scattered light scattered from the sample, the optical axis of the lens A light-receiving system that measures only light parallel to the sample and is arranged in multiple directions in the direction of the scattering angle of the scattered light of the sample, and a plurality of light-receiving systems that are determined in advance based on the scattered light intensity distribution of the material measured by this light-receiving system and Mie scattering theory. A particle size measuring device comprising: a signal processing system that determines the particle size distribution of the sample by comparing the intensity distribution of scattered light for different particle sizes of the particles. 2. A sample consisting of a light source that emits monochromatic light and a plurality of particles whose particle size is to be measured is irradiated with monochromatic light from the light source, and of the scattered light scattered from this sample, only the light that is parallel to the optical axis of the lens is detected. A light receiving system to be measured, a driving device that scans this light receiving system in the scattering angle direction of the scattered light of the sample, and a plurality of light receiving systems that are determined in advance based on the scattered light intensity distribution of the sample measured by the light receiving system and Mie scattering theory. 1. A particle size measuring device comprising: a signal processing system that determines the particle size distribution of the sample by comparing scattered light intensity distributions for different particle sizes of particles.