JPH01213547A - Grain size distribution measuring instrument - Google Patents

Abstract

PURPOSE:To inexpensively lower the lower limit particle size to be measured to <=1/3 the lower limit particle size of the prior art by providing a light source part where a deuterium or halogen lamp, interference filter and pinhole are used as well as a semiconductor sensor and image intensifier. CONSTITUTION:The lower limit particle size to be measured is smaller as the wavelength of light for measurement is shorter in the case of using a forward microangle scattering method. The need for a UV laser which is costly and has poor maintenance characteristic is, therefore, eliminated by using the deuterium lamp or halogen lamp as the light source lamp 1, using the interference filter 3 to obtain light of a single wavelength and imparting convergence to the light by the pinhole 4; in addition, the quantity of light is amplified by the image intensifier 7 provided on the photodetecting surface side of the semiconductor photosensor 8, by which the quantity of the light equiv. to the quantity of the light obtainable with the conventional gaseous He-Ne laser light source is obtd. and the lower limit particle size to be measured is lowered to <=1/3. Moreover, the measurement range is largely expanded by exchange of the filter 3.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is based on Frauhofer diffraction and Mie scattering theory.
This invention relates to a particle size distribution measuring device for powder and granular materials using forward small angle scattering method.

<Prior art> The particle size distribution of the powder to be measured can be determined by measuring the intensity distribution of scattered light based on Frauhofer diffraction or Mie scattering theory, which is obtained by irradiating light onto the powder to be measured in a dispersed state. In a particle size distribution measuring device using a so-called forward small angle scattering method, the measurement light is generally required to have coherence and monochromaticity in order to measure the intensity of diffracted light.

For this reason, a laser is used as a light source for measurement light, and a photomultiplier or a semiconductor photosensor is used as an optical sensor for measuring diffracted light or scattered light.

Although there are various types of laser light sources, a He-Ne gas laser has conventionally been mainly used due to its cost and maintainability.

<Problem to be solved by the invention> By the way, the wavelength of the output light of the He-Ne gas laser is 63
2.8 nm, such light is irradiated onto the particle to be measured in the sample cell as a parallel beam using a collimating lens, and the resulting diffracted light is transferred to the focal plane of the Fourier transform lens placed behind it. In an optical system that uses so-called Frauhofer diffraction, in which the intensity distribution of the diffracted light is measured by placing a detector such as a ring-shaped photomultiplier on the focal plane, the small diameter side where the measurement is possible is performed. The particle size limit for is at most 0.4 μm. Therefore, conventional measures have been taken to measure microparticles, such as using an optical system called an inverse Fourier optical system. In an inverse Fourier optical system, a beam from a light source is focused by a condenser lens, a detector is placed on the focal plane of the condenser lens, and a particle to be measured is placed between the detector and the condenser lens. Although the lower measurement limit is shifted to the smaller diameter side by using such an optical system, the scattering pattern becomes constant when the particle diameter/wavelength value becomes less than a certain value, so when a He-Ne gas laser is used as the light source, The limit is about 0.1 μm.

Using a laser in the ultraviolet range, for example, in order to shorten the wavelength of measurement light results in enormous costs and is not practical from the viewpoint of maintainability.

An object of the present invention is to further reduce the measurement minimum particle diameter in a particle size distribution measuring apparatus using such a forward small angle scattering method without using an expensive laser.

Means for Solving the Problems> In order to achieve the above object, the particle size distribution measuring device of the present invention includes a lamp 1 for a light source, an interference filter 3, as shown in FIG. 1 corresponding to an embodiment. a ring-shaped semiconductor photosensor 8 that receives diffracted light or scattered light obtained by irradiating the particle to be measured (inside the flow cell 6) with light from the lamp 1 that has passed through the pinhole 4, the interference filter 3, and the pinhole 4; , is characterized by having an image intensifier 7 disposed on the light-receiving surface side of the photosensor 8.

Measurement of both scattered light and diffracted light is to find the relationship between the scattering angle or diffraction angle and light intensity (hereinafter referred to as scattering pattern), and the particle size distribution is obtained by calculation using the photometric data. . In the case of a single particle, the scattering pattern is mainly determined by the wavelength and particle diameter values. As described above, this scattering pattern becomes constant when the value of particle diameter/wavelength becomes less than a certain value, and this determines the minimum particle diameter for measurement.

From the above, if short wavelength light is used as measurement light, the lower limit of measurement will shift toward the smaller diameter side. Therefore, the lamp 1 for the light source
The desired purpose is achieved by using a deuterium lamp, a halogen lamp, or the like, obtaining light of a desired single wavelength through an interference filter 3, and providing convergence to this light through a pinhole 4.

The image intensifier 7 provided on the light-receiving surface side of the semiconductor photosensor 8 is used to amplify the amount of light obtained with the above configuration, which is lower than when using a conventional He-Ne gas laser as a light source. is necessary.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of an optical system according to an embodiment of the present invention, and shows an example in which the present invention is applied to an inverse Fourier optical system.

The light source section S includes a lamp 1 such as a deuterium lamp or a halogen lamp, a condenser lens 2, an interference filter 3, and a pinhole 4.

The light from the lamp 1 that has passed through the condenser lens 2, the interference filter 3, and the pinhole 4 is condensed onto the detector D by the condenser lens 5. A flow cell 6 is disposed between the condenser lens 5 and the detector D, in which the powder to be measured flows in a dispersed flying state.

Detector D includes an image intensifier (optical amplifier) 7 attached to the light receiving surface of a ring-shaped semiconductor photosensor 8 similar to the conventional one. The ring-shaped semiconductor photosensor 8 is an array-shaped sensor in which a plurality of ring-shaped light-receiving surfaces are arranged concentrically, and the center thereof is placed on the optical axis of the measurement light. so that the light focusing point is on the light receiving surface of the image intensifier 7.
The position is 'TZ gJI clause. The output of the ring-shaped semiconductor photosensor 8 is input to a computer (none of which are shown) via an amplifier, an A-D converter, etc., and the particle size distribution of the powder to be measured can be determined using a known algorithm. can.

According to the embodiment of the present invention described above, the light from the lamp 1 is converted into a single wavelength light of a predetermined wavelength by the interference filter 3, and is given condensing property by passing through the pinhole 4 in the next stage.As a result, the inverse Fourier optical system The light is satisfactory as a measuring light.

The scattered light obtained by irradiating the powder to be measured in the flow cell while condensing such light with the condenser lens 5 draws a scattering pattern on the detector D. The amount of light emitted from the light source section S is extremely low compared to a conventional device using a He-Ne gas laser as a light source. Such light scattered by the powder and granular material of measurement light is amplified by the image intensifier 7, and becomes light having a light amount and wavelength that can be photometered by the semiconductor photosensor 8.

FIG. 2 is a block diagram of an optical system according to another embodiment of the present invention, showing an example in which the present invention is applied to a normal Fraunhofer diffraction light measurement system.

In this example, the structures of the light source section S and detector D are the same as those in the example shown in FIG. The light irradiated onto the body and diffracted here is focused onto a detector D by the Fourier transform lens 10 in the next stage, forming a diffraction image.

When measuring diffracted light, the measuring light is required to have coherence as well as monochromaticity, but the pinhole 4 serves to provide coherence in this system, and from the light source S. This measurement system also outputs effective light.

In each of the above embodiments, the wavelength of the measurement light can be changed by replacing the interference filter 3. As mentioned above, the wavelength of the measurement light is a factor that determines the minimum particle diameter for measurement. For example, by using a wavelength of about 200 nm, the optical system shown in Figure 1 can measure up to about 0.03 μm, and the optical system shown in Figure 2 can also measure up to 0.03 μm.
．． It is possible to measure up to about 1 to 0.15 μm.

<Effects of the Invention> As explained above, according to the present invention, a light source section using a deuterium lamp, a halogen lamp, etc., an interference filter and a pinhole, and a semiconductor photodiode can be used without using an expensive and difficult-to-maintain ultraviolet laser. By installing a sensor and an image intensifier, the lower limit particle diameter for particle size distribution measurement using forward small-angle scattering method is reduced to 1/3 or less compared to conventional equipment using a He-Ne gas laser as a light source. be able to. Furthermore, since the wavelength of the measurement light can be easily changed by replacing the interference filter, there is an advantage that the measurement range in the same optical system can be greatly expanded.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical system according to an embodiment of the present invention, and FIG. 2 is a block diagram of an optical system according to another embodiment of the present invention. 1...Lamp 3...Interference filter 4...Pinhole 5...Condensing lens 6...Flow self...Image intensifier 8...Ring-shaped semiconductor photosensor Patent applicant Stock Company representative Shimadzu Corporation Masato
Patent Attorney Nishi 1) Arata

Claims (1)

[Claims] This device measures the particle size distribution of particles to be measured from the intensity distribution of diffracted light or scattered light obtained by irradiating light onto particles to be measured in a dispersed state, and includes a lamp for a light source, an interference filter, and a pin. a ring-shaped semiconductor photosensor that receives diffracted light or scattered light obtained by irradiating the particle to be measured with light from the lamp that has passed through the hole, the interference filter and the pinhole; A particle size distribution measuring device, characterized in that it is equipped with an image intensifier.