JPH0675029B2 - Particle size distribution measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a particle size distribution measuring device for measuring by a particle size distribution laser diffraction method, which is one of the most basic physical properties of powder.

Conventional technology One of the most basic physical properties of powder is particle size distribution. The particle size distribution is an important physical property that influences the physical and chemical properties of the powder itself, and is deeply related to the performance and quality of the product produced from the powder. in recent years,
Fine powder as a raw material for fine ceramics has been attracting attention, and there is a particle size distribution measuring device using a laser diffraction method as a device that can measure the particle size distribution quickly with high accuracy. Explaining the measurement principle of this device, when the test particle group is irradiated with laser light, the irradiated laser light is diffracted by the test particle group. A ring-shaped diffraction image is obtained. On the other hand, the radial light intensity distribution in this diffraction image has a predetermined correlation with the particle size distribution of the sample particle group. That is, the particle size distribution measuring device is a device based on the Fraunhofer theory, etc., and the diffracted light intensity distribution of the laser diffracted light is obtained, whereby the particle size distribution of the sample particle group can be measured with high accuracy. ing. A schematic configuration of a conventional particle size distribution measuring device will be described.

As shown in FIG. 4, the parallel laser light a generated by the semiconductor laser 11 and the collimator lens 13 is applied to the flow cell 20 made of a transparent body in which the sample turbid liquid is in a circulating state. There is. Moreover, when the sample laser beam 40 contained in the sample turbid liquid is irradiated with the parallel laser light a, it is diffracted and the laser light b is focused by the Fourier transform lens 31 on the ring detector 34. ing. Then, the intensity of the diffracted light of the laser beam b is set to the ring detector.
The basic configuration is such that a plurality of light receiving elements in 34 are used for detection, and the detection result is led to a microcomputer or the like (not shown) to calculate the particle size distribution of the sample particle group 40. The ring detector 34 is made by forming a plurality of concentric circles of photodiodes or the like on a semiconductor wafer by a semiconductor technique. The intensity of the diffracted light of the laser beam b becomes weaker as the diffraction angle increases. Therefore, the light receiving area of each photodiode is set to increase from the center of the ring in the radial direction.

By the way, when each particle of the test particle group 40 is large, the intensity of the diffracted light of the laser beam b is strong in the range where the diffraction angle is small, and its change is severe. On the other hand, when each particle in the sample particle group 40 is small, the diffracted light intensity of the laser beam b is strong in the range where the diffraction angle is large, but the change is gentle.

Therefore, the particle size distribution measuring apparatus is provided with a Fourier transform lens 31 (for example, three) having different focal lengths, and a mechanism for converting the Fourier transform lens 31 according to the setting of the measurement range (not shown). ), This is devised to have a high measurement system over a wide measurement range. That is, in the measurement range when the particle size of the sample particle group 40 is large, the Fourier transform lens 31 with a long focal length is used.
Enlarge the diffraction image in the range of small diffraction angle using, and detect the enlarged diffraction image with the ring detector 34, while in the measurement range when the particle diameter of the sample particle group 40 is small, the focal length The short Fourier transform lens 31 is used to compress a diffraction image in a large diffraction angle range, and the compressed diffraction image is detected by the ring detector 34.

However, in the case of the above-described conventional example, the size is limited in the manufacturing method of the ring detector 34, and therefore the following drawbacks are pointed out. The first drawback is that the particle size distribution in a wide range can be measured with high accuracy, and in addition to the need for a plurality of Fourier transform lenses 31, a mechanism for exchanging them is required. Is very complicated, and its adjustment is troublesome, which is a great obstacle in promoting the cost reduction of the entire apparatus. The second drawback is that the sample particle group
In order to further expand the measurement range in the range where the particle size of 40 is large without degrading the measurement accuracy, it is necessary to use a Fourier transform lens with a longer focal length than the current one, and accordingly the entire device Will become larger. In other words, if the size of the device is restricted, the measurement range cannot be expanded within the above range.

The present invention was devised in view of the above circumstances, and a particle size distribution measuring device capable of measuring the particle size distribution in a wide range with high accuracy with only a single Fourier-exchange lens and also capable of expanding the measurement range. The purpose is to provide.

Means for Solving the Problems A particle size distribution measuring apparatus according to the present invention is a laser light irradiation unit for irradiating a parallel laser beam to a test particle group in a dispersed flight state through a circular deflection plate, and the test particle group. The parallel laser beam diffracted or scattered at is condensed by a Fourier transform lens on a fan-shaped detector composed of a plurality of photosensors each having a large light-receiving area from the beam center to the radial direction, And a laser light receiving section for detecting the diffracted light intensity or scattered light intensity of the parallel laser beam by the fan-shaped detector.

Action The parallel laser beam is linearly deflected, and when measured in a specific direction, it is affected by the deflection, but the circular deflection plate eliminates the influence of the deflection. Also, when the parallel laser beam that has passed through the circular deflector irradiates the sample particles in the dispersed flight state,
Diffracted or scattered depending on the particle size of the sample particle group. This diffracted or scattered light is condensed on the fan-shaped detector by the Fourier transform lens, and the diffracted light intensity or scattered light intensity is detected by the plurality of light receiving elements formed on the fan-shaped detector. A diffracted light intensity distribution or scattered light intensity distribution is obtained from this detection result, and the particle size distribution of the sample particle group is calculated through this.

Example Hereinafter, one example of a particle size distribution measuring apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a particle size distribution measuring device, FIG. 2 is a plan view of a fan-shaped detector, and FIG. 3 is a front view of a semiconductor wafer for explaining a manufacturing method of the fan-shaped detector.

The particle size distribution measuring device listed here shows the particle size distribution of the test particle group (test particle group in the dispersed flying state) contained in the diluting liquid by the laser diffraction method and the laser scattering method, and the Fraunhofer for particles of 2 μm or more. (Fraunhofer) Diffraction theory. This is a device for measuring particles of 2 μm or less with high accuracy based on the Mie scattering theory. The configuration of the particle size distribution measuring device will be described below with reference to FIG.

Semiconductor laser 11 (here, GaAlAS semiconductor, wavelength 780 nm,
Output 3 mW), and the parallel laser light a generated by the collimator lens 13 is transmitted through the circular deflection plate 12 to the transparent flow cell 20.
It is designed to be illuminated. These constitute the laser light irradiation unit 10. The flow cell 20 is made of a glass tube or the like,
In this tube, a suspension 41 containing the test particle group 40 in the diluent
Are circulated in the direction shown.

In addition, the suspension concentration in the flow cell 20 is always kept at an appropriate value by a dilution device (not shown) connected to the flow cell 20, a circulation device, and the floating state of the sample particle group 40 is always kept properly. It is like this.

The parallel laser light a circularly deflected by the circular deflection plate 12 is applied to the sample particle group 40 in the flow cell 20, and is diffracted or scattered at an angle according to the particle diameter.

The laser beam b that has been diffracted or scattered and has passed through the flow cell 20 is condensed by a Fourier transform lens 31 on a fan-shaped detector 32, which will be described later, and the fan-shaped detector 32 detects the diffracted light intensity or scattered light intensity of the laser beam b. It has become so. These constitute the laser light receiving section 30.

As shown in FIG. 2, the fan-shaped detector 32 has a structure in which the detectors 321, 322, and 323 divided into three parts are adhered on the same plane. Detector 321, 32
Photoreceptive element such as photodiode on 2,323
A predetermined number of 321a, 322a, and 323a are formed, respectively, and these are fan-shaped as a whole. Moreover, the light receiving elements 321a, 322a, 323a are arranged concentrically from A to B in the figure, and the light receiving area thereof is increased. The fan-shaped detector 32 having such a structure is first
As shown in the figure, there is no particular restriction on the arrangement except that the portion A is arranged perpendicularly to the optical axis of the Fourier transform lens 31 and in the direction of the optical axis of the Fourier transform lens 31. That is, the portion B in the figure of the fan-shaped detector 32 may be oriented in any direction. Explaining the reason for this, the parallel laser beam a is originally linearly deflected, and if it is not 90 ° and 180 ° with respect to the deflection direction, it is affected by the deflection. Since the influence of the deflection is eliminated, the diffracted light intensity or scattered light intensity of the laser light b is equal at any angle at the same radial position from the beam center, and the fan-shaped detector 32
The arrangement may be as described above. The manufacturing method of the fan-shaped detector 32 will be described later.

In addition, the light receiving elements 321a, 32a in the fan-shaped detector 32.
The electric signals output from 2a and 323a are signals that give the intensity of the diffracted light or scattered light of the laser light b, and are introduced into a microcomputer (not shown).
In this microcomputer, the diffracted light intensity distribution or scattered light intensity distribution of the laser light b is obtained based on the obtained data, and the particle size distribution of the sample grain group 40 is calculated based on the well-known Fraunhofer diffraction theory and Mie scattering theory. The calculation is performed and the calculation result is output to the outside.

Next, a method for manufacturing the fan-shaped detector 32 will be described with reference to FIG. That is, on the semiconductor wafer 33, the light receiving elements 321a, 322a, 323a divided by the detectors 321, 322, 323 by semiconductor technology are formed, respectively, and then the semiconductor wafer 33 is cut to take out the detectors 321, 322, 323. . And the detectors 321, 322, 323 that are cut from each other
2 is bonded as shown in FIG. 2, the fan-shaped detector 32 is manufactured. In the case of this manufacturing method, for example, the semiconductor wafer 33 is 4 inches, and the detectors 321, 322, 32 are
When the fan angle of 3 is 12.5 °, a large fan detector 32 of about 180 mm can be built. Further, when the fan-shaped detector 32 is made from a plurality of semiconductor wafers by the same method, a very large fan-shaped detector 32 can be made as compared with the conventional one. However, when the fan-shaped detector 32 is made from one semiconductor wafer 33 as in the present embodiment, the electric characteristics of the light receiving elements 321a, 322a, 323a are likely to be uniform, so from the viewpoint of temperature drift compensation and the like. There are merits.
Incidentally, the light receiving elements 321a, 32a in the fan-shaped detector 32.
Since 2a and 323a are fan-shaped as shown in FIG. 2, there is also an advantage that the design correction calculation due to the difference in area can be simplified.

Therefore, the particle size distribution measuring apparatus of the present invention can detect the diffracted light intensity or the scattered light intensity of the laser light b by using the fan-shaped detector 32 which is much larger than the conventional one, and has the following merits as the ripple effect. Obtainable. That is, in the conventional example, in order to measure the particle size distribution with high accuracy over a wide range, it is necessary to replace a plurality of Fourier transform lenses having different focal lengths according to the setting of the measurement range. However, in this embodiment, since the light-receiving area of the detector can be made larger than that of the conventional one, a single Fourier transform lens 31 having a predetermined focal length can provide a highly accurate particle size distribution in a similar range. Can be measured. Therefore, the number of Fourier transform lenses can be reduced, the optical mechanism can be greatly simplified, and the troublesomeness of adjusting it can be omitted. Has great significance.

Furthermore, the measuring dynamic lens can be made very large, in connection with the fact that the Fourier transform lens 31 does not have to be replaced with a different focal length. That is,
In the conventional example, a wide measurement range was covered by the method of switching to the measurement lens suitable for the object to be measured, but in the present example, the switching of the measurement range is not required,
One measurement range can cover the same measurement range. In addition, as described above, since it is possible to take the large light area of the detector as compared with the conventional one, it is possible to further increase the measurement range such as a range in which the particle size of the sample particle group 40 is large without changing the size of the device more than necessary. It can be expanded.
Therefore, it is of great significance in improving the performance of the device.

In addition, the particle size distribution measuring apparatus according to the present invention has shown the measurement example when the sample particle group is dispersed in the diluent, but it is also applicable when the sample particle group is dispersed in the gas. Is natural.

As described above, in the case of the particle size distribution measuring device of the present invention, the detection of the diffracted light intensity or the scattered light intensity can be performed with a very large fan-shaped detector, so that a single Fourier-exchange lens alone can be used in a wide range of particle sizes. The distribution can be measured with high accuracy.
Therefore, the entire optical mechanism becomes very simple, and the troublesome adjustment can be omitted. Moreover, it is possible to easily expand the measurement range in the range where the particle size of the test particle group is large, which is of great significance in promoting both cost reduction and high performance of the device.

[Brief description of drawings]

1 to 3 are views for explaining one embodiment of the particle size distribution measuring apparatus according to the present invention, wherein FIG. 1 is a block diagram of the particle size distribution measuring apparatus, and FIG. 2 is a fan-shaped detector. A plan view and FIG. 3 are front views of a semiconductor wafer for explaining a method for manufacturing a fan-shaped detector. FIG. 4 and FIG. 5 are views for explaining a conventional particle size distribution measuring device,
FIG. 4 is a view corresponding to FIG. 1, and FIG. 5 is a front view of the ring detector. 10 …… Laser light irradiation part 11 …… Semiconductor laser 12 …… Circular deflection plate 13 …… Collimator lens 20 …… Flow cell 30 …… Laser light receiving part 31 …… Fourier transform lens 32 …… Fan detector 321a, 322a, 323a …… Light receiving element 40 …… Sample particle group a …… Parallel laser light

Claims (1)

[Claims] 1. A laser beam irradiator for irradiating a sample particle group in a dispersed flying state with a parallel laser beam through a circular deflection plate,
The parallel laser beam diffracted or scattered by the sample particle group has a large light receiving area from the beam center to the radial direction, and a Fourier transform lens is provided on a fan-shaped detector composed of a plurality of photosensors each having a plurality of light receiving elements. A particle size distribution measuring device, comprising: a laser light receiving section that collects light and detects the diffracted light intensity or scattered light intensity of the parallel laser beam by the fan-shaped detector.