JPS6123943A - Particle measuring device - Google Patents

Abstract

PURPOSE:To detect a particle diameter, speed, and mixing rate with high precision by allowing light beams to cross each other in a measurement area, separating reflected signals and detecting signals coincident on a time base as to the separated signals, and detecting the time when a measured particle passes through the crossing area. CONSTITUTION:Laser light from an He-Ne laser 1 is split by a beam splitter 2 into laser beams A and B. The output of an oscillator 3 is applied to a black cell 4 on the passing path of the beam A; the signal A becomes a signal intermitted at the oscillation frequency of the oscillator 3 and the beam B, on the other hand, is a continuous signal. The beams A and B are passed through a condenser lens 5 to cross each other and the crossing area of the beams A and B is positioned in a water tank for measuring an object of measurement, e.g. diameters and a distribution of air bubbles. Reflected light obtained from the crossing area is converged through a reflecting mirror 6 and a condenser lens 7 and signals coincident on the time base are detected by a coincidence detecting circuit 11 from a signal obtained from a photoelectric converter 8, thereby detecting the diameter, speed, and mixing ratio of particles from the output of a pulse width detecting circuit 15 with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention is directed to the treatment of small air particles mixed into fluids such as liquids. The present invention relates to a particle measuring device that measures the distribution of particle mixing ratio per particle diameter such as fa.

Background of the Invention Gas-liquid two-phase flows occur in various devices, but in flowing water such as closed cavity test tanks and recirculation tanks used in model experiments of hydraulic machines and ships, minute air bubbles with a diameter of about L mm are generated. This can occur in large numbers and change the experimental conditions in the aquarium. Therefore, it is necessary to measure the inclusion rate, bubble diameter, etc. of such minute bubbles, but a measurement method suitable for detecting such bubbles has not been sufficiently established. As a conventional device for measuring gas-liquid two-phase flow, there is a device (Japanese Patent Application No. 56-200589) that places an optical fiber in a fluid and detects the presence or absence of bubbles based on the state of light reflection. However, when measuring minute bubbles, there is a problem in that sufficient data cannot be obtained because the bubbles do not penetrate the tip of the optical fiber.

In addition, as is established with a laser velocity needle, interference fringes are formed by intersecting two parallel laser beams at one point, and the bubble velocity is determined based on the Doppler burst signal of the scattered light obtained from the interference fringe region. It is possible to obtain. However, since the bubbles generated in a water tank or the like are too large to generate a Doppler burst signal, it has not been possible to directly detect the velocity or diameter of the bubbles. It is also possible to obtain the time of the bubble passing through the laser beam by the time width of the reflected light, but since the signal width obtained varies greatly depending on the position where the bubble passes, it is difficult to accurately measure the bubble passing time. The problem was that it was not possible.

Purpose of the Invention The present invention provides a particle measuring device for use in such aquariums, etc., in order to eliminate harmful air pollution in aquarium experiments, etc.
The purpose is to provide a particle measuring device that can measure the particle size, speed, and mixing rate of particles with high precision and in a short time.

Structure and effects of the invention This application deals with the rate of minute particles mixed into fluid.

A particle measuring device for measuring particle size distribution, and a first invention of the present application includes a light source that generates first and second beams that are separable and parallel to each other; an optical lower stage for causing the second light beam to intersect in the measurement area; a photoelectric converter that receives the reflected light of the second light beam and converts it into an electric signal; a reflected signal separating means for separating reflected wave signals of the second light beam based on the properties of the light beam; and a reflected signal separating means ζ. The second reflected wave signal passes through the intersection region of the beam of the measurement particle based on the output of the coincidence detection means J, which detects a coincidence signal at the axis of 45 n:; 'aj14 hour detection means for detecting time, and the second invention of the present application uses the first as this optical means. It is characterized by using an optical means having an arcuate lens formed in an arcuate column shape that focuses the second light beams only in the same direction and intersects at one point as a light diameter of a thin ellipse in cross section. It is something.

According to the first invention of the present application having such features, it is possible to set a predetermined range of the intersection area of two light beams as a linear measurement area, and to accurately measure the passing speed of particles passing through the measurement area. It is possible.

Therefore, it is possible to obtain a large amount of particle data compared to measurement at one point, and since the measurement area is limited, particle diameters can be accurately determined without obtaining incorrect particle data when passing before and after the measurement area. can be measured. Furthermore, since the reflected light of the light beam is used, the signal strength is strong and it is possible to measure the transit time of particles without contact. If the particle velocity is known, it becomes possible to know the particle diameter and its distribution state based on the measurement data.

Furthermore, according to the second invention of the present application, in addition to the above-mentioned effects, two light beams are focused in only one direction by an arcuate lens to form an elliptical cross section, and the light beams are made to have the thinnest luminous flux. Since they intersect at one point, it is possible to expand the measurement area planarly. This will greatly increase the number of particles passing through the measurement area, making it possible to collect a large number of particle data in a short period of time, making it possible to accurately measure data for each particle passing through the measurement area. Become.

This has the effect that the diameter of the granulated particles 7 and its mixing rate can be measured extremely quickly.

DESCRIPTION OF EMBODIMENTS [Principle of the Invention] FIG. 2 fat to TCI are shown in FIG. FIG. 3 is a principle diagram showing the measurement principle of the bubble measuring device according to the second invention;
a+~(C1 is a waveform diagram obtained corresponding to the position of each passing bubble. As shown in this figure, in the invention of the present application, two distinguishable light beams A and B are used and the light beams are detected by a predetermined optical system. The light beams intersect in the area to be measured.Then, a light receiving element PD is provided at the center line 4 of these two light beams to receive the light reflected from the bubble.
As shown in the figure (al), when a bubble rises from below, if the radius of the bubble is a, the end face of the bubble becomes two light beams A,
When touching the intersection of light beams B, the light receiving element PD first receives the reflected light from the light beam A as shown in FIG. It will be done. Also, as shown in Figure 2 (bl), if the intersection point of the two light beams A and B is at a position a/2 inward from the end face of the bubble, the two light beams Reflected light is obtained from the light beams A and B at the light receiving element PD at the same time.Furthermore, if the intersection point of the two light beams A and B coincides with the center of the bubble as shown in FIG. As shown in FIG. 3(C), the PD first obtains the reflected light of the light beam B, and then obtains the reflected light of the light beam A.

As is clear from these figures, by extracting only the signals when reflected wave signals are obtained from the two light beams A and B at the same time, we can extract the reflected light signals only when the bubble passes through a predetermined position of the light beams. You will be able to obtain

[Embodiment of the first invention] FIG. 1 is a block diagram showing an embodiment of a bubble measuring device according to the first invention of the present application. In this figure, for example, an I-re-Ne laser 1 is used as a light source, and its 1.--di light is separated into two Radhe beams Δ and B by a beam splitter 2. The oscillator 3 is an oscillator that oscillates a square wave signal with a frequency of, for example, about 200 K Ilz, and its output is sent to a Bragg cell 4, which is an acousto-optic element located at one-third of the pass edge of the laser beam A. If this Bragg cell 4 is driven and shifted by the oscillator 3, the L laser beam A will shift in the direction shown by the broken line in the figure when voltage is applied to the Shirasoge cell 4, and the laser beam J1Δ will be shown by the solid line when no voltage is applied. Go straight. Therefore, the laser beam A becomes an intermittent signal depending on the oscillation frequency of the oscillator 3, while the laser beam B becomes a continuous signal. These laser beams Δ, 13 are made to intersect at one point by a 55-bundle lens 5.

In this embodiment, a convex lens is used as the focusing lens 5, and the optical system is configured such that the intersection area of the laser beams A and B is located in the measurement target, for example, a water tank for measuring the diameter and distribution of bubbles. I'll keep it.

Then, the reflected light along the axis of the optical system obtained from this intersection region is passed through a condenser lens 5 to become a parallel beam, reflected by a reflecting mirror 6, and condensed at a single point by a condenser lens 7. A photoelectric converter 8, such as a photomultiplier tube, for converting the reflected light output into an electrical signal is provided at the focal point of the condensing lens 7. Then, the electrical signal obtained by the photoelectric converter 8 is amplified by the amplifier 9 and applied to the bandpass filter IO and the low-pass filter 11. Bandpass filter 1
0 is a filter that passes only signals with a frequency equal to the oscillation frequency of the oscillator 3, that is, 200 K Ilz,
The low-pass filter 11 is a filter that passes signals having frequencies below a predetermined frequency that is sufficiently lower than 200 KHz. The outputs of these filters 10.11 are provided to waveform shaping circuits 12.13, respectively.

The waveform shaping circuits 12.13 output square wave signals having a time width equal to the signal applied through the filter 10.11, and their outputs are sent to the coincidence detection circuit 14.
is given to. The coincidence detection circuit 14 is a circuit for detecting the temporal coincidence of the square wave outputs given from the two waveform shaping circuits 12 and 13, and is formed using, for example, an AND circuit and an IQ circuit that holds its output. be done. In the first match detection cycle, a match is determined based on whether there is a moment when two input signals match. The output of the waveform shaping circuit 13 is also sent to the pulse width detection circuit 15! 4 has been given. The pulse width detection circuit 15 is the waveform shaping circuit 13
It detects the pulse width of a square wave signal given by the coincidence detector 14, and when an output is given from the coincidence detector 14, the signal is transmitted to the microcomputer 17 via the input interface 16. 5 Microcomputer 17 u Calculate the bubble diameter from the already given bubble velocity according to the predetermined calculation processing procedure.
Anatomy ■ Signal processing such as JI and integration for each bubble diameter is performed, and the results are displayed on the display 18.

[Operation of First Embodiment] Next, the operation of this embodiment will be described with reference to the waveform diagram in FIG. 4. When the H,e-Ne laser 1 emits a laser beam and applies it to the beam brick 2, the laser beam is separated into two laser beams A and B. Then, by giving the output of the oscillator 3 to the Bragg cell 4, the laser beam A
These laser beams A and B are focused at one point in the measurement area by a focusing lens 5.

If a bubble arrives in the two laser beams A and B and reflected light is obtained along the center line of this optical system, then,
The reflected light is applied to a photoelectric converter 8 via a focusing lens 51, a reflecting mirror 6, and a focusing lens 7, and is converted into an electrical signal.

The reflected light signal is separated by a filter 10.11 into two signals corresponding to the respective laser beams A and B. Then, as described above, different signals on the time axis can be obtained from the band pass filter 10 and the low pass filter 11 depending on the passage position of the bubble.゛No. 41ff
l(al, (bl) is a waveform diagram showing the respective outputs of the band pass filter 1o and the low pass filter 11, and these outputs are converted into square wave signals by the waveform shaping circuits 12 and 13. Now, FIG. Since the outputs of the waveform shaping circuits 12 and 13 are almost the same from time ti to C2 as shown in C1, +d), the coincidence detection circuit 14 outputs a coincidence output as shown in FIG. 4 tQ). In this case, it is considered that the bubble passed through the position shown in FIG. The detected pulse width data of the output of the waveform shaping circuit 13 becomes valid and is taken into the microcomputer 17 via the input interface 16.
4, each of the waveform shaping circuits 12 and 13 outputs 1q, but since the signal is obtained from the waveform shaping circuit 12 first and the output from the waveform shaping circuit 13 is obtained thereafter, as shown in FIG.
It is considered that the bubbles passed outside the measurement area as shown in al. In this case, since the two outputs do not match, the match detection circuit 14 does not output any output, and the pulse width data at that time is not taken into the microcomputer 17. Similarly, outputs are obtained from the waveform shaping circuits 12 and 13 between time t5 and C6, but in this case as well, the two do not match, and as shown in FIG. is thought to have passed.

Therefore, in this case as well, the pulse width data is not taken into the microcomputer 17 and no signal processing is performed.

In this way, it is possible to limit the measurement area within a predetermined range of the intersection area of the two laser beams. This measurement area is considered to be a linear area in this embodiment. Since a signal is obtained only when the bubble passes through this region, the obtained pulse width has a length that exactly corresponds to the time that the bubble passes through the measurement region. Therefore, if the speed of the bubbles passing through the water tank is known in advance, the bubble diameter can be calculated from the bubble speed and passage time. In addition, this bubble diameter data is transferred to the microcomputer 1.
7 and performs statistical processing, it becomes possible to obtain statistical data on the number of bubbles passing through the water tank and the bubble diameter. This data is displayed on display 18.

[Embodiment of the second invention] In the present invention, the signal processing part is the same as the first invention, but the optical system part is improved to make the measurement area planar and obtain a large amount of particle data. It is.

That is, the bubble measuring device of this embodiment has an H value as shown in FIG.
The e-N e laser 1 is separated into two parallel laser beams A and B by the beam splitter 2.
Intermittent one of them by Bragg cell 4 is the first
This is similar to the example. Collimating pieces 20 and 21 are placed in the optical paths of these laser beams A and B, respectively, and the light i\ is expanded as shown in the figure to form a laser beam C2D. Then, as shown in FIG. 5, these two laser beams C and D are made to intersect at one point using a cylindrical lens 22. The cylindrical lens 22 is a rectangular lens with a flat back surface and an arcuate front surface, and does not focus the laser beam in the Y-axis direction in the figure, but focuses two laser beams only in the X-axis direction. It focuses C and D. Therefore, the two laser beams C and D that have passed through this cylindrical lens 22 are focused in the X-axis direction and returned to the original state in the Y-axis direction, as shown in FIGS. Since the light diameter remains the same, it becomes an elliptical light diameter with a flat cross section and intersects at the beam waist point at the focal position.The measurement area 24 where the laser beams C and D intersect is shown in Fig. 6). It can be thought of as being almost flat.

On the back surface of this cylindrical lens 22 is a small diameter cylindrical lens 23 having a long axis in the X-axis direction as shown in FIG. 6(a).

The reflected light reflected from the intersection area along the optical axis of the optical system is focused by these cylindrical lenses 22 and 23.

In this case, the same effect as when the reflected light obtained by the action of the two cylindrical lenses 22 and 23 is condensed by one convex lens can be obtained. The parallel reflected light thus obtained is reflected by a reflecting mirror 6 in the same way as in the embodiment shown in FIG. The configuration and operation of each block thereafter are the same as in the embodiment of the first invention, and depending on the presence or absence of interruption, the bandpass filter 10. The waves are separated by a low-pass filter 11 and shaped by a waveform shaping circuit 1"2.43. When the outputs from these waveform shaping circuits 12.13 match, a coincidence detection circuit 14 outputs an output and changes the waveform at that time. The pulse width detected by the pulse width detection circuit 15 and transmitted to the microphone 1:1 computer I7 via the human interface 16 is similar to the embodiment described above.

In this way, when the bubble passes through the flat measurement area 24, data on the time taken for the bubble to pass can be obtained, making it possible to obtain a large amount of data in a short period of time. Here, Figure 6 fb
As shown in FIG. 1, the width W of the measurement area 24 is
Determined by the light diameter of D, the depth β is determined by the coincidence detection circuit 14
It is possible to adjust the range by giving a matching output of . In other words, match detection time 1? If &14 is made to give an output when the outputs of the two waveform shaping circuits 12.13 match even momentarily, it is possible to make the depth l the widest, and also when the outputs of both match, for example, by 50% or more. If the coincidence detection circuit 14 outputs an output from time to time, the depth β of the measurement area 24 can be narrowed accordingly.

[Modified example of the embodiment]

In each of the embodiments described above, one laser beam is interrupted using a Bragg cell, and the two laser beams are thereby separated by a signal processor, but two laser beams having different wavelengths are used. The two reflected lights may be separated based on the difference in wavelength, or the polarization directions of the laser beams may be different and the reflected lights of the two laser beams may be separated based on the difference in the polarization directions. good.

Furthermore, in each of the embodiments of the two inventions described above, the reflected light is reflected by a mirror, and the reflected light is condensed by a condensing lens and guided to a photoelectric converter. Needless to say, the optical system section and the electrical signal processing section can be separated by using the optical system.

In the embodiment of the second invention, a small-diameter cylindrical lens was used in combination with the cylindrical lens to condense the reflected light. By arranging a convex lens in a portion, it is possible to convert the reflected light along the optical axis into parallel rays or to condense the reflected light at a single point.

Furthermore, in each of the two consecutive embodiments, a bubble measuring device for measuring the diameter of bubbles in an aquarium has been described, but the present invention can also be applied to particles such as liquid particles floating in the air.

[Brief explanation of the drawing]

A waveform diagram showing the waveforms of each part of the first embodiment, FIG. 5 is a perspective view showing the bubble measuring device of the second invention of the present application, and FIG.
and FIG. 6 (bl is a side view and a top view showing the convergence state of the laser beam by the cylindrical lens 22. 1. He-Ne laser 2. Beam splinter 3. ------Oscillator 5--Focusing lens 6--------Reflector 8-----
-One photoelectric converter 10---Band pass filter 11---One low pass filter 12, 1
3-------Coincidence detection circuit 14-------Coincidence detection circuit 15-------Pulse width detection circuit
17---Microcomputer 20,
21---Collimating lens 22, 23
---------One cylindrical lens 24--Measurement area agent Patent attorney Kanki Okamoto ((lt! 1 person) Fig. 1

Claims (7)

[Claims] (1) A light source that generates first and second beams that are separable and parallel to each other; an optical means that causes the first and second light beams to intersect in a measurement area; and the first and second light beams. a photoelectric converter that receives the reflected light of the first and second light beams and converts it into an electrical signal; a reflected signal separation means that separates the reflected wave signals of the first and second light beams based on the properties of the light beam; and the reflected signal separation means. Coincidence detection means for detecting a signal that coincides on the time axis among the separated first and second reflected wave signals; and a time taken for the measurement particle to pass through the intersection region of the beam based on the output of the coincidence detection means. A particle measuring device comprising: transit time detection means for detecting. (2) At least one of the first and second light beams is a light beam interrupted at a predetermined frequency, and the reflected signal separation means separates the reflected wave signal according to the frequency of the signal interruption of the light beam. A particle measuring device according to claim 1, characterized in that: (3) The first and second light beams are light beams having different polarization directions, and the reflected signal separation means is composed of a polarizing filter. particle measuring device. (4) a light source that generates first and second beams that are separable and parallel to each other; and a light source that focuses the first and second light beams only in the same direction and has an elliptical light diameter with a thin cross section. an optical means having an arc-shaped lens formed in an arc column shape that intersects at one point; a photoelectric converter that receives reflected light of the first and second light beams and converts it into an electrical signal; reflected signal separation means for separating reflected wave signals of the light beam based on the properties of the light beam; and signals that coincide on a time axis among the first and second reflected wave signals separated by the reflected signal separation means. A particle measuring device comprising: a coincidence detecting means for detecting; and a transit time detecting means for detecting a time for a measurement particle to pass through an intersection region of the beam based on an output of the coincidence detecting means. (5) At least one of the first and second light beams is a light beam interrupted at a predetermined frequency, and the reflected signal separation means separates the reflected wave signal according to the frequency of the signal interruption of the light beam. The particle measuring device according to claim 4, characterized in that: (6) The first and second light beams are light beams having different polarization directions, and the reflected signal separation means is composed of a polarizing filter. particle measuring device. (7) The optical means is provided adjacent to the cylindrical lens at an intermediate position between the first and second light beams and faces in a direction different from the long axis direction of the cylindrical lens, and 5. The bubble measuring device according to claim 4, further comprising a second cylindrical lens for condensing the reflected light.