JPH02203246A - Grain size distribution measuring instrument - Google Patents

Abstract

PURPOSE:To measure a wide range of grain size distributions with high accuracy by condensing laser light by a Fourier transform lens onto a sectorial detector consisting of plural photosensors and detecting the diffracted light intensity, etc., of collimated beams of the laser light by the sectorial detector. CONSTITUTION:A sample particle group 40 in a flow cell 20 consisting of a transparent body is irradiated via a circularly deflecting plate 12 with the collimated beams (a) of the laser light formed by a semiconductor laser 11 and a collimator lens 13. The beams (a) are diffracted or scattered by the angle according to the grain diameter. The laser light (b) transmitted through the flow cell 20 is condensed by the Fourier transform lens 31 onto the sectorial detector 32 and the diffracted light intensity or scattered light intensity of the laser light (b) is detected by the detector 32. The electric signal outputted from the detector 32 is introduced to a microcomputer and the diffracted light intensity distribution or scattered light intensity distribution of the laser light (b) is determined in accordance with the resulted data. The grain size distribution of the particle group 40 is calculated in accordance with Fraunhofer diffraction theory and Mie scattering theory.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a particle size distribution measuring device for measuring particle size distribution, which is one of the most basic physical properties of powder, by laser diffraction or the like.

! One of the most fundamental physical properties of powder is particle size distribution. Particle size distribution is an important physical property that affects the physical and chemical properties of powder itself, and is also deeply related to the performance and quality of products produced using powder as a raw material. In recent years, fine powder as a raw material for fine ceramics has attracted attention, and a particle size distribution measuring device using a laser diffraction method is available as a device that can quickly measure particle size distribution with high accuracy. To explain the measurement principle of this device, when a group of test particles is irradiated with a laser beam, the irradiated laser light is diffracted by the group of test particles,
If this diffracted light is focused with a lens, a ring-shaped diffraction image will be obtained behind the sample particle group.

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 Fraunhofer
(ofer) A conventional particle size distribution measuring device that is based on theory, etc., and is designed to measure the particle size distribution of a sample particle group with high precision by determining the diffracted light intensity distribution of laser diffracted light. The general configuration of this will be explained.

As shown in FIG. 4, the parallel laser beam a generated by the semiconductor laser 11 and the collimator lens 13 is irradiated onto a flow cell 20 made of a transparent body in which a sample turbid liquid is flowing. There is.

Furthermore, when the collimated laser beam a is irradiated onto the sample particle group 40 contained in the sample turbid liquid, it is diffracted, and this laser beam is focused onto the ring detector 34 using the Fourier transform lens 31. There is. Then, the intensity of the diffracted light of the laser beam is detected by a plurality of light receiving elements in the ring detector 34, and the detection results are led to a microcomputer, etc. (not shown), where the sample particle group 40
The basic configuration is such that a zero particle size distribution is calculated.

Note that the ring detector 34 is made by forming a plurality of photodiodes or the like arranged concentrically on a semiconductor wafer using semiconductor technology, and the intensity of the diffracted light of the laser beam becomes weaker as the diffraction angle increases. Therefore, the light-receiving area of each photodiode is set to increase from the ring center to the radial direction.

By the way, when each particle of the sample particle group 40 is large,
The intensity of the diffracted light of the laser beam is strong in the small diffraction angle range,
Moreover, the changes are drastic. On the other hand, when each particle of the sample particle group 40 is small, the intensity of the diffracted light of the laser beam is strong in a range where the diffraction angle is large, but the intensity changes slowly.

Therefore, in the particle size distribution measuring device, Fourier transform lenses 31 (for example, three lenses) having different focal lengths are prepared, and a mechanism (not shown) for exchanging the Fourier transform lenses 31 according to the setting of the measurement range is provided. ), which is designed to have high measurement accuracy 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 1 with a long focal length
The diffraction image in a small range of diffraction angles is magnified using the lens 31, and the magnified diffraction image is detected by the ring detector 34. In the measurement range when the particle diameter of the sample particle group 40 is small, Fourier transform lens with short focal length 3
1 is used to compress the diffraction image in a large range of diffraction angles, and the compressed diffraction image is detected by the ring detector 34.

However, in the conventional example described above, there is a limit to the size due to the manufacturing method of the ring detector 34, and the following drawbacks have been pointed out. The first drawback is that although the particle size distribution over a wide range can be measured with high precision, it requires multiple Fourier transform lenses 31 and a mechanism to replace them, so the entire optical mechanism is The system is extremely complicated and its adjustment is troublesome, which is a huge obstacle in reducing the overall cost of the device. The second drawback is that the sample particle group 4
In order to further expand the measurement range in the range of large particle diameters without reducing measurement accuracy, it would be necessary to use a Fourier interchangeable lens with a longer focal length than the current one, and this would require the entire device to be becomes larger. In other words, if there are restrictions on the dimensions of the device, it is not possible to expand the measurement range within the above range.

The present invention was devised in view of the above circumstances, and is a particle size distribution measuring device that can measure particle size distribution over a wide range with high precision using only a single Fourier interchangeable lens, and can also expand the measurement range. The purpose is to provide

! The particle size distribution measuring device according to the present invention for measuring the particle size distribution includes a laser beam irradiation unit that irradiates a parallel laser beam to a group of test particles in a dispersed layer state through a circular deflection plate, and a particle size distribution measurement device that The diffracted or scattered parallel laser beam is condensed by a Fourier transform lens onto a fan-shaped detector consisting of a plurality of photosensors each having a large light-receiving area and a plurality of light-receiving elements in the radial direction from the center of the beam. The laser beam receiving section detects the diffracted light intensity or scattered light intensity of the light beam using the fan-shaped detector.

Parallel laser beams are linearly polarized, and when photometrically measured in a specific direction, they are affected by the polarization, but the circular deflection plate eliminates the effects of the polarization. In addition, when the parallel laser beam that has passed through the circularly polarized plate is irradiated onto the sample particles in the dispersed layer state,
The particles are diffracted or scattered depending on the particle diameter of the sample particle group. This diffracted light or scattered light is focused onto a fan-shaped detector by a Fourier transform lens, and the intensity of the diffracted light or scattered light is detected by a plurality of light-receiving elements formed in the fan-shaped detector. The diffracted light intensity distribution or scattered light intensity distribution is obtained from this detection result, and through this the particle size distribution of the sample particle group is calculated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the particle size distribution measuring device according to the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a particle size distribution measuring apparatus, 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 method of manufacturing the fan-shaped detector.

The particle size distribution measuring device listed here measures the particle size distribution of the sample particles contained in the diluted solution (the sample particles in a dispersed layer state) using the laser diffraction method and the laser scattering method. y (Fraunho
fer) diffraction theory, for particles smaller than 2 am, Mie (
Mie) This is a highly accurate measurement device based on scattering theory. The configuration of the particle size distribution measuring device will be explained below with reference to FIG.

A parallel laser beam a generated by a semiconductor laser 11 (GaAIAS semiconductor here, wavelength 780n-1 output 3IIW) and a collimator lens 13 is irradiated onto a transparent flow cell 20 via a circular deflection plate 12. ing. These constitute the laser beam irradiation section 10. The flow cell 20 is made of a glass tube or the like, and a suspension 41 containing a sample particle group 40 in a diluent is circulated in the direction shown in the figure.

Note that the concentration of the suspension in the flow cell 20 is always maintained at an appropriate value by a dilution device, circulation device, etc. (not shown) connected to the flow cell 20, and the suspended state of the sample particle group 40 is always maintained at an appropriate value. It looks like this.

The parallel laser beam a that has been circularly polarized by the circularly polarizing plate 12 is irradiated onto the sample particle group 40 within the flow cell 20, and is diffracted or scattered at an angle corresponding to the particle diameter.

The laser beam that has been diffracted or scattered and transmitted through the flow cell 20 is focused by a Fourier transform lens 31 onto a fan-shaped detector 32, which will be described later.
The diffracted light intensity or scattered light intensity of the laser beam is detected. These are the laser light receiving section 30
Configure.

By the way, the fan-shaped detector 32 is here divided into three parts 321, 322, and 323 as shown in FIG.
It has a structure in which the two are glued together on the same plane. On the detectors 321, 322, 323 are light receiving elements 321a, 322a, 323a such as photodiodes.
are formed in a predetermined number, and these are fan-shaped as a whole. Moreover, the light-receiving Niremen) 321a,
322a and 323a are arranged concentrically from A to B in the figure, and have a large light receiving area. The fan-shaped detector 32 having such a structure is arranged perpendicularly to the optical axis of the Fourier transform lens 31 as shown in FIG. There is no particular restriction regarding the arrangement; in other words, the fan-shaped detector 32 may be oriented in any direction at portion B in the figure. To explain the reason for this, the parallel laser beam a is originally linearly polarized, and will be affected by the polarization unless it is 90'' or 180'' with respect to the deflection direction, but in the Kimoto example, the circular deflection plate 12 Since the influence of circular deflection is eliminated, the intensity of the diffracted light or scattered light of the laser beam is the same regardless of the angle at the same radial position from the beam center, and the fan-shaped detector 32 is arranged as described above. It is okay to do so. Note that a method for manufacturing the fan-shaped detector 32 will be described later.

Moreover, the light receiving element 321 in the fan-shaped detector 32
The electrical signals outputted from a, 322a, and 323a are signals that give the intensity of the diffracted light or the intensity of the scattered light of the laser beam, and are introduced into a microcomputer (not shown). This microcomputer calculates the diffracted light intensity distribution or scattered light intensity distribution of the laser beam based on the obtained data, and calculates the particle size distribution of the sample particle group 40 based on the well-known Fraunhofer diffraction theory and Mie scattering theory. It is designed to calculate and output the calculation results externally.

Next, a method for manufacturing the fan-shaped detector 32 will be explained with reference to FIG. That is, on a semiconductor wafer 33, light receiving elements 321a, 322a are separated by detectors 321, 322, and 323 using semiconductor technology.

After that, the semiconductor wafer 33 is cut to take out the detectors 321, 322, and 323. and the detectors 321, 322, 323 disconnected from each other
If they are glued together as shown in FIG. 2, a fan-shaped detector 32 will be made. In the case of this manufacturing method, for example, the semiconductor wafer 33 is 4 inches long and the detector 321 is
, 322, 323 is 12.5°, a large fan-shaped detector 32 of about 180 mm can be made. Further, when the fan-shaped detector 32 is made from a plurality of semiconductor wafers using the same method, it can be made much larger than conventional ones. However, when the fan-shaped detector 32 is made from one semiconductor wafer 33 as in this embodiment, the light receiving element 321a,
Since the electrical characteristics of 322a and 323a are likely to be uniform, there is an advantage from the viewpoint of temperature drift compensation, etc. Note that the light receiving element 321a in the fan-shaped detector 32
, 322a, and 323a are fan-shaped as shown in FIG. 2, which has the advantage of simplifying design correction calculations based on the difference in area.

Therefore, the actual particle size distribution measuring device can detect the diffracted light intensity or scattered light intensity of the laser beam using the fan-shaped detector 32, which is much larger than the conventional one, and the ripple effects of this are as follows. can be obtained. In other words, in conventional methods, in order to measure particle size distribution with high precision over a wide range, a mechanism was required to replace multiple Fourier transform lenses with different focal lengths depending on the measurement range setting. However, in this embodiment, since the light-receiving area of the detector can be made larger than that of the conventional one, it is possible to cover the same range with high accuracy using just one Fourier transform lens 31 having a predetermined focal length. can be measured. Therefore, in addition to being able to reduce the number of Fourier transform lenses, it is also possible to greatly simplify the optical mechanism and eliminate the trouble of adjusting it, which is extremely effective in reducing equipment costs. has great significance.

Furthermore, in connection with the fact that there is no need to replace the Fourier transform lens 31 with one having a different focal length, a very large measurement dynamic range can be achieved. In other words, in the conventional example, a wide measurement range was covered by switching to the measurement range that matched the object to be measured, but in this example, there is no need to switch the measurement range, and one measurement range can be used. This allows them to cover the same measurement range. In addition, as mentioned above, since the light-receiving area of the detector can be larger than that of conventional detectors, the measurement range, such as the range where the particle size of the sample particle group 40 is large, can be further expanded without making the device unnecessarily large. Is possible. Therefore, it is of great significance in improving the performance of the device.

Note that although the particle size distribution measuring device according to the present invention has been shown as an example of measurement when the sample particle group is dispersed in a diluted liquid, it can also be applied to a case where the sample particle group is dispersed in a gas. Of course.

Since summer has arrived, this real particle size distribution measuring device can detect the diffracted light intensity or scattered light intensity using a very large fan-shaped detector, so it can be used over a wide range with only a single Fourier interchangeable lens. Particle size distribution can be measured with high accuracy.

Therefore, the entire optical mechanism becomes very simple and its troublesome adjustment can be omitted. Moreover, it is possible to easily expand the measurement range in a range where the particle size of the sample particle group is large, which is of great significance in promoting both cost reduction and performance improvement of the apparatus.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 to 3 are diagrams for explaining an embodiment of the particle size distribution measuring device according to the present invention, and FIG. 1 is a configuration diagram of the particle size distribution measuring device; FIG. 2 is a plan view of the fan-shaped detector, and FIG. 3 is a front view of a semiconductor wafer for explaining a method of manufacturing the fan-shaped detector. FIG. 4 and FIG. 5 are diagrams for explaining a conventional particle size distribution measuring device,
FIG. 4 is a diagram corresponding to FIG. 1, and FIG. 5 is a front view of the ring detector. lO・ ・ 11・ ・ 12・ ・ 13・ ・ 20・ ・ 30・ ・ 31・ ・ 32・ ・ 321a. 40... l l - Laser light irradiation section, semiconductor laser, circular polarizing plate, collimator lens, flow cell, laser light receiving section, Fourier transform lens, fan-shaped detectors 322a, 323a... - Sample particle group, parallel laser light, light reception element

Claims (1)

[Claims] (1) A laser beam irradiation unit that irradiates a parallel laser beam to a group of test particles in a dispersed flying state via a circular deflection plate, and a beam center that irradiates the parallel laser beam diffracted or scattered by the test particle group. The light is focused by a Fourier transform lens onto a fan-shaped detector consisting of a plurality of photosensors each having a large light-receiving area and a plurality of light-receiving elements in the radial direction, and the diffracted light intensity or scattered light intensity of the parallel laser beam is converted into the fan-shaped A particle size distribution measuring device comprising: a laser beam receiving section that detects the particle size using a detector.