JPH0264435A - Measuring apparatus for particle size - Google Patents

Abstract

PURPOSE:To obtain a particle size measuring apparatus which can be manufactured inexpensively and can select freely the resolution of a diffracted light or a scattered light, by providing a light-sensing device with a flexible light transmission cable and a photoelectric conversion device. CONSTITUTION:A laser light emitted diffusedly from a light-emitting device 22 is applied to a transparent vessel 21 through a convex lens 26 and the light passed therethrough is focused on a focal point 29 on a light-sensing surface 23 through a condenser lens 27. A diffracted light caused by particulates in the vessel 21 is not condensed but forms a diffraction ring on the surface 23. This diffracted light enters a light-sensing end part 28 of a light-sensing device 25 disposed on the surface 23, passes through a light transmission cable 34 and is transmitted to a photoelectric conversion device 36, where the intensity of the light is converted into an electric signal. An output of the device 36 is subjected to numerical conversion in an arithmetic circuit 30 and displayed in a display device 31. Since a light-sensing cross section on the end part 28 of each cable 34 is fixed, the intensity of the light on each radius forming the diffraction ring and the size of the diffraction ring can be measured by disposing the end part 28 on the radius containing the focal point 29. Besides, the resolution of the diffracted light can be selected arbitrarily by selecting this end part 28 appropriately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a particle size meter, and particularly to a particle size measuring device for measuring the particle size of fine particles such as powder.

For example, as shown in Japanese Unexamined Patent Publication No. 49-27285, the particle size of the powder material is reduced by suspending the powder material in a gaseous fluid and irradiating the powder material with a laser beam. Techniques for measuring are known.

When a powder material is irradiated with a convergent monochromatic parallel laser beam emitted from a light emitting device, a Franhofer diffraction image is formed by the powder material on the focal plane of the optical system.

The light intensity of this diffraction image is detected by a photocell placed at the focal plane of the optical system.

At this time, the light that does not undergo diffraction is condensed at a focal point, and the light that has been diffracted into one cone forms an image around the optical axis. Light having the same diffraction angle is always focused on the same radius on the focal plane.

A powder material suspended in a gaseous fluid is a collection of particles having different diameters, and the diffraction images obtained from those particles are focused at different radial positions. That is, a diffracted light intensity distribution corresponding to the particle size distribution is observed on the focal plane. Therefore, the particle diameter can be measured by detecting the light intensity of the diffraction image formed on the focal plane of the optical system using a photocell.

To explain a particle size measuring device that uses Franhofer's diffraction image, a is the radius of the particle, and c=1/λ E /
x a7, E is the incident energy on the particle, λ is the wavelength of parallel light, p is the position on the focal plane, k = 2π/λ, ω = s/f
, s is the radius on the focal plane, and ρ is the distance from the center of the disk, then the amplitude U(p) is.

U(p)=2πc/a'Jo(kρω)ρdρ (
If we integrate Equation 6 (1) given by 1).

U(p)=xa”c(2Jo(ka ω)/ka ω
) (2) Therefore, the luminous intensity distribution I (p) is.

I (p) = (U (p))' = (za"c)" (2Ja(ka ω)/ka ω)"
(3) If the intensity on the focal point is 10, it is sufficient to set ω=0 in equation (1), so (2). =(πa2c)” (4)
is given by Therefore, if the specific intensity is Y, then Y = I
(p)/I. =4(J, (kρω)8ρω)”
(5), the right side of equation (3) (J, (ka ω)/k
The maximum value of ``a ω)'' is d(Jt(kaω)/kaω)/d(kaω)=O(6
) is given by kaω that satisfies According to the Bessel function reduction equation, for equation (6) to hold, Jz(kaω)=0 is sufficient, and the minimum value only needs to be Jl(kaω)=0.

If the radius S on the focal plane is a dimensionless radius Xa=kaω, then 5=Xaλf/2xa (7) Thus, the diameter of the diffraction image is inversely proportional to the diameter of the particle size. Furthermore, as is clear from equation (5),
The specific intensity is determined independently of the position of the particle, and the position of the diffraction image does not change no matter where the particle is in the light beam. l
However, if the particle size is large, the diameter of the diffraction ring will be small, and if the particle size is small, the diameter of the diffraction ring will be large. However, the relationship between the particle size and the diameter of the diffraction ring changes depending on the type of light or lens used. Therefore, once the contents of the apparatus are determined, the relationship between the particle size and the diameter of the diffraction ring is uniquely determined. Even when a plurality of particles are present, the diffraction rings formed by each particle become concentric circles due to the use of a lens.

On the other hand, US Pat. No. 4,274,741 discloses a particle size measuring device that uses a plurality of sector-shaped photovoltaic cells. This particle size measuring device will be explained with reference to FIGS. 3 and 4. A monochromatic beam 1 of a helium-neon laser is irradiated from a light emitting device (not shown) to a transparent container 2 containing a sample. The light passing through the container 2 passes through the lens 3 to the focal plane 4.
The image is formed on the upper focal point 5. As shown in FIG. 4, a plurality of sector-shaped photovoltaic cells 8 having various sizes are provided on the focal plane 7 of the light receiving device W6. The output of the photocell 8 is connected to the conductor 9
The light is supplied to the arithmetic circuit 12 through the amplifiers 10 and 11, and the light intensity corresponding to the radius from the focal point 5 is measured at the focal plane 7. In this way, the particle size of the sample can be determined by the size of the single diffraction ring.

Also, Japanese Patent Publication No. 57-21042 or 56-667
As shown in Japanese Patent No. 37, a particle size measuring device using light scattering is known. With this particle size measuring device, when a particle is irradiated with single wavelength light such as an unpolarized laser beam, the scattering angle distribution of the scattered light intensity is measured for the vertical and horizontal components. A specific light intensity distribution is obtained. This theory was proposed by Mis and is referred to as "Mie scattering." Mie analyzes that the intensity of scattered light from a single particle obtained based on the vertical and horizontal polarization intensity distribution is expressed as a function of the scattering angle, the particle diameter parameter α, and the complex refractive index of the substance to be measured. For the particle diameter parameter α, let Dρ be the particle diameter and λ be the wavelength of the light source.

It is defined as α=πDp/λ. Here, (1) when α<0.3, it is expressed as a Rayleigh scattering region; (2) when 0,3<α2, it is a Mie scattering region; (3) when 2<α, it is expressed as a vibration region. By measuring the scattered light intensity in this way, the volume or particle size of the particles can be determined.

However, in the particle size measuring device disclosed in the above-mentioned US patent, a plurality of silicon single crystals formed in a predetermined fan shape must be used as photovoltaic cells. For this reason, the process of manufacturing photovoltaic cells by molding silicon single crystal into a predetermined door shape and connecting conductor wires to the photovoltaic cells must be carefully performed by skilled workers, making it time consuming to manufacture photovoltaic cells. Ta. Therefore, the price of light receiving devices has increased.

Furthermore, in conventional particle size measuring devices, the shape of the photovoltaic cell placed in the focal plane is predetermined and cannot be changed. For this reason, in order to change the resolution of diffracted light or scattered light, it is necessary to prepare a large number of light receiving devices equipped with photocells of various shapes and replace the light receiving devices as necessary, resulting in huge equipment costs. and man-hours.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a particle size measuring device which can solve the above-mentioned drawbacks, can be manufactured at low cost, and can freely select the resolution of diffracted light or scattered light.

The particle size measuring device according to the present invention includes a transparent container containing a substance whose particle size is to be measured, a light emitting device that irradiates a light beam onto the container, and a light beam irradiated from the light emitting device that detects the substance in the container. and a light-receiving device that measures the light intensity distribution or scattered light intensity distribution of a diffraction image on the light-receiving surface formed by diffraction or scattering. The light receiving device includes a flexible optical transmission cable having a light receiving end disposed on the light receiving surface, and a photoelectric conversion device disposed adjacent to the light emitting end of the optical transmission cable.

Shoji J1 By using a flexible optical transmission cable, a light receiving device can be manufactured at low cost without using expensive silicon single crystal photovoltaic cells. In addition, the light-receiving end and the light-emitting end of the optical transmission cable can be formed into a desired shape, and the light-emitting and light-emitting ends of the light receiving device, which is optically connected to the light-emitting end, can be installed at a desired location through the optical transmission cable. It becomes possible to do so.

By appropriately selecting the light receiving end of the optical transmission cable disposed on the light receiving surface, the resolution of the diffracted light or scattered light can be arbitrarily selected. Furthermore, since optical transmission cables are not easily affected by temperature, shock, and vibration, and are not affected by electromagnetic noise, the light-emitting end of the optical transmission cable should be placed sufficiently away from heat-generating parts such as light-emitting devices. Accurate measurements can be taken.

Furthermore, when changing the particle size measurement conditions to form diffraction rings or scattered lights of different diameters, the overall size of the diffracted or scattered lights can be determined by measuring the light intensity on the light receiving surface and processing the measured values by computer. Particle size can be measured partially or partially with various resolutions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2, which was implemented with respect to a particle size measuring device that measures particle size using an optical diffraction method.

First, as shown in FIG. 1, a particle size measuring device 20 according to the present invention includes a transparent container (cell) 21 that accommodates a substance whose particle size is to be measured, a light emitting device 22 that irradiates the container 21 with light, and The light beam irradiated from the light emitting device 22
A light receiving device 24 that measures the light intensity distribution of a diffraction image on a light receiving surface 23, which is a focal plane formed by diffraction by a substance inside the light receiving device 24.
and has. The light emitting device 22 is a helium-neon laser and is provided with a diffusion lens 22a. In fact, it is also possible to use a semiconductor laser instead of a helium-neon laser. Furthermore, a beam expander can be used instead of the diffusing lens 22a and the convex lens 26, which will be described later.

The monochromatic light emitted from the light emitting device 22 in a diffused state is emitted from the container 2.
1 is introduced into an optical system 25 arranged before and after the optical system 1. The optical system 25 includes a convex lens 26 that converts the light diffused from the light emitting device 22 into parallel light beams, and a condensing lens 27 that condenses the light that has passed through the container 21. The condenser lens 27 actually has two lenses 27a and 27b. A light-receiving end 28 (FIG. 2) of the light-receiving device 24 is arranged on the light-receiving surface 23 of the condenser lens 27 . The container 21 contains a suspension in which fine particles are mixed in a light-transmitting solution such as water or alcohol. The output of the light receiving device 24 is supplied to an arithmetic circuit 30 consisting of a computer, and the output of the arithmetic circuit 30 is supplied to a display device 31 and a printer 32. Also,
The light emitting state of the light emitting device 22 is controlled by the keyboard 33 through the calculation circuit 30.

As shown in FIG. 2, the light receiving device 24 is arranged adjacent to a flexible optical transmission cable 34 having a light receiving end 28 disposed on the light receiving surface 23 and a light emitting end 35 of the optical transmission cable 34. and a photoelectric conversion device W36. The photoelectric conversion device i36 uses a photovoltaic cell such as a light receiving transistor or a light receiving diode.

Although not shown in detail, each optical transmission cable 34 has a core that transmits incident light, a cladding formed around the core, and an exterior covering the outer surface of the cladding. Second
For example, the optical transmission cable 34 is connected to the case 3 as shown in the figure.
7 in three rows, the number of optical transmission cables 34 in each row giving the length to match the size of the diffraction ring.

In the above configuration, the laser light diffused and emitted from one light emitting device 22 is converted into a parallel light beam by the convex lens 26, and then irradiated onto the transparent container 21. The light passing through the container 21 is focused by a condensing lens 27 onto a focal point 29 on the light receiving surface 23 .

The diffracted light diffracted by the fine particles in the container 21 is focused at a focal point 29.
A diffraction ring of light is formed on the light receiving surface 23 without being focused upward. In this state, the first diffracted light enters the light receiving end 28 of the light receiving device 24 disposed on the light receiving surface 23 and enters the optical transmission cable 3.
4 to the photoelectric conversion device 36, and the photoelectric conversion device 3
6 converts the light intensity into an electrical signal. The output of the photoelectric conversion device 36 is converted into a numerical value by the arithmetic circuit 30 and displayed by the display device 31. In the illustrated example, the optical transmission cables 34 are arranged in three rows, but since the light receiving cross-sectional area on the light receiving end 28 of each optical transmission cable 34 is constant, the light receiving end 28 is arranged on the radius including the focal point 29. , it is possible to measure the light intensity on each radius forming the diffraction ring and the size of the diffraction ring.

In this case, by using the flexible optical transmission cable 34, the light receiving device 24 can be manufactured without using an expensive silicon single crystal photovoltaic cell. Further, since the light receiving end 28 and the light emitting end 35 of the optical transmission cable 34 can be formed into a desired shape, the light receiving device 24 can be installed at a desired location. Further, by appropriately selecting the light receiving end portion 28 of the optical transmission cable 34 disposed on the light receiving surface 23, the resolution of the diffracted light can be arbitrarily selected. That is, when improving the resolution of diffracted light.

The amount of light received from the light receiving ends 28 of the multiple optical transmission cables 34 can be measured partially or entirely. Conversely, when measuring particle size with low resolution, unnecessary light reception at the light receiving end 28 need not be measured. The operation of selecting only the necessary light-receiving end 28 from a large number of light-receiving ends 28 is as follows.

This can be done very easily by operating the arithmetic circuit 30 through the keyboard 33.

Furthermore, since the optical transmission cable 34 is not easily affected by temperature, shock and vibration, and is not affected by electromagnetic noise, the light emitting end 35 of the optical transmission cable 34 should be positioned sufficiently away from the heat generating part of the light emitting device 22 etc. It can be installed in any location to perform accurate measurements. In addition, when changing the particle size measurement conditions to form diffraction rings of different diameters, the light intensity on each radius of the diffraction ring can be measured through the optical transmission cable 34 and the measured values can be processed by a computer, so that the changed conditions can be changed. Particle size can be measured at various resolutions below.

The above embodiments of the invention can be modified. For example, in the above embodiment, a particle size measuring device that measures particle size using optical diffraction method was described, but it is clear that the present invention can also be implemented in measuring particle size using light scattering method. In this case, it is necessary to measure the scattered light intensity of the light scattered in a direction perpendicular to the optical axis of the light beam emitted from the light source.
The light receiving device 24 may be arranged so that each light receiving end 28 of the light receiving device 24 forms a plane perpendicular to the scattered light, and the case 37 may be formed in a ring shape or an arc shape instead of a straight shape.

As described above, it is not necessary to use a plurality of silicon single crystals formed in a predetermined fan shape as a photovoltaic cell, and the photovoltaic cell can be manufactured in a short time and at a low cost. In addition, since the amount of light at a desired position on the light receiving surface can be measured via the optical transmission cable and photoelectric conversion device, it is possible to change the overall or partial resolution of the diffracted light or scattered light as appropriate. Become. In this case, the light receiving device can be applied to diffraction rings or scattered light of various sizes through a computer arithmetic circuit. Further, by changing the arrangement of the light-receiving surface, the particle size measuring device of the present invention used in the optical diffraction method can be used as it is as a particle size determination device in the light scattering method. Furthermore, since the light emitting end of the optical transmission cable can be installed at a desired position, the installation space can be used effectively.

[Brief explanation of the drawing]

Fig. 1 is a block diagram schematically showing a particle size measuring device according to the present invention, Fig. 2 is a perspective view schematically showing a light receiving device, Fig. 3 is a block diagram of a conventional particle size measuring device, and Fig. 4 is a conventional particle size measuring device. FIG. 2 is a block diagram showing a light receiving device of the measuring device. 2000 particle size measuring device, 215. container, 2260 light emitting device, 239. Light receiving surface, 24. . Light receiving device, 280. Light receiving end, cable, 3501 light emitting end, conversion device. 340. Sakihiro 368. Photoelectric patent applicant Y.D.K. Co., Ltd. Agent
Kei Shimizu - (1 person from the number) r',,',,,,,,)/ Figure 1 Figure 3 Figure 4 Figure 2

Claims (1)

[Claims] A transparent container that contains a substance whose particle size is to be measured, a light emitting device that irradiates the container with light, and a light receiving surface formed by diffracting or scattering the light rays emitted from the light emitting device by the substance in the container. In a particle size measuring device having a light receiving device for measuring a light intensity distribution of a diffraction image or a scattered light intensity distribution,
The light receiving device has a flexible optical transmission cable having a light receiving end disposed on the light receiving surface, and a photoelectric conversion device disposed adjacent to the light emitting end of the optical transmission cable. measuring device.