JP3662423B2 - Particle analyzer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a particle analyzer that electrically captures and optically captures and analyzes particles dispersed in an electrolytic solution.
[0002]
[Prior art]
Several methods are used as methods for measuring the shape and quantity of particles such as metal powder and toner particles. The Coulter method is well known as a method for electrically measuring such particles, and FIG. 4 shows a particle measuring apparatus using the Coulter method. In the Coulter method, as shown in FIG. 4, an electrolytic solution 4 in which particles are dispersed is placed in a container 1, a tube 2 having an opening 3 through which particles 5 can pass is disposed, and electrodes 6 and 7 are disposed on the inside and outside of the tube 2, respectively. The tube 2 is also filled with the electrolytic solution 4, and the electrolytic solution 4 is sucked from above. Through the opening 3, the particles 5 together with the electrolyte 4 pass through the opening 3 and enter the tube 2. At this time, the electrolytic solution 4 in the opening 3 is reduced by an amount corresponding to the volume of the particles 5, and the electrical resistance of the opening 3 becomes larger in proportion to the excluded electrolytic solution. Accordingly, a change in electric resistance proportional to the volume of the particles 5 occurs in the opening. When a constant current is passed between the electrodes 6 and 7, the amount of voltage change between the electrodes 6 and 7 increases in proportion to the amount of change in the electrical resistance of the opening 3. The volume of the particles can be measured from this voltage change amount, and the number of particles passing through the opening 3 can be counted from the number of voltage changes. This is called the Coulter principle, and a device for measuring particles using this method is called a Coulter counter.
[0003]
In FIG. 4, reference numeral 9 denotes a first monitor, and shows voltage fluctuations when one particle 5 passes. The integral value of this waveform represents a value proportional to the volume of the particle 5. Reference numeral 10 denotes a second monitor, which shows a histogram (particle size distribution) of the volume distribution of particles that have passed in a certain time from the voltage change count and the integrated value of the voltage waveform. The horizontal axis indicates the volume of the particles, and the vertical axis indicates the number of particles.
[0004]
FIG. 5 is a diagram showing a sample and an imaging device of an apparatus for measuring the size and number of particles by imaging the particles dispersed in the liquid with a camera and analyzing the images. A sample made of a liquid containing particles is flowed in the center of a transparent flow channel called a sheath flow cell, and a transparent liquid called sheath liquid is flowed on both sides of the sample so that the sample flows in the center. A strobe and a CCD camera are placed across the sheath flow cell, and an objective lens is placed in front of the CCD camera to obtain an enlarged image of the particles. The strobe emits light at regular time intervals, and the sample at this time is photographed with a CCD camera. The obtained image is analyzed by an image processing apparatus (not shown), and the two-dimensional shape and number of particles are measured.
[0005]
[Problems to be solved by the invention]
However, in the case of the Coulter counter shown in FIG. 4, when two particles overlap and enter the opening, the volume and the number of particles may be measured as one particle. Further, in the case of the apparatus shown in FIG. 5, since a flash is emitted at a certain time interval, for example, every 1/30 seconds, a screen without particles or an image that is excessively overlapped is obtained. However, there are cases where the size and number of particles cannot be analyzed by the image processing apparatus.
[0006]
The present invention has been made in view of the above-described problems, and provides a particle analysis apparatus that can reliably measure the volume and number of particles and can perform a three-dimensional analysis from the volume and projected area of the particles. Objective.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a tube having an opening is disposed in the electrolytic solution, electrodes are provided on the inside and outside of the tube, and the electric resistance between the electrodes when the particles pass through the opening is reduced. A particle detector that measures the volume and number of particles by measuring changes, a strobe that illuminates the aperture at a timing when the electrical resistance changes, a camera that images the particles illuminated by the strobe, and a camera An image processing apparatus that performs image analysis of particles from the captured image and particle data detected by the particle detection apparatus.
[0008]
When the electric resistance between the electrodes changes, a strobe is emitted to take an image, so that an image of particles passing through the opening can be obtained. In addition, when a plurality of particles pass through the opening, a plurality of particles can be confirmed from the image. By eliminating such data, the total volume of the plurality of particles can be set to the volume of one particle, It is also possible to prevent erroneous measurement of one particle. In addition, a three-dimensional analysis of particles is possible by combining the volume of particles and a two-dimensional image. Further, since the field of view of the camera is aligned with the aperture and the particles passing through the aperture are photographed, a clear image of the particles can be obtained.
[0009]
According to a second aspect of the present invention, the camera has a half mirror in the optical system, reflects light from the strobe by the half mirror, irradiates the particles, and images the reflected light passing through the half mirror.
[0010]
By capturing the reflected light of the particles with a camera using a half mirror, not only the shape of the particles but also the color can be captured, which is useful for particle analysis. For example, the particles can be reliably identified from the difference in color.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing the configuration of the particle analyzer of the first embodiment. Reference numeral 1 denotes a transparent container into which an electrolytic solution 4 in which particles 5 are dispersed is placed. A transparent tube 2 is arranged in the container 1, an opening 3 through which the particles 5 pass is provided at the lower part, and the upper part is connected to a hose connected to a pump that sucks the electrolyte 4 inside. Note that suction may be performed according to the principle of siphon. The size of the diameter of the opening 3 corresponds to the particle 5 to be measured. For example, the diameter of the opening 3 can correspond to a wide range of particles of 15 μm and a large one of 2000 μm. Particles having a diameter of about 2% to 60% of the diameter of the opening 3 can be measured.
[0012]
A positive electrode 6 is provided in the tube 2, and a negative electrode 7 is provided in the container 1 outside the tube 2, and a constant current flows. Current flows between the electrodes 6 and 7 through the opening 3. The opening 3 has a thickness and only has an electrical resistance. When the electrolytic solution 4 is sucked from the upper part of the tube 2, the particles 5 pass through the opening 3 together with the electrolytic solution 4. At this time, the amount of the electrolytic solution 4 corresponding to the volume of the particles 5 is reduced, and the electric resistance of the opening 3 becomes a large value in proportion to the amount of the reduced electrolytic solution 4. Since a constant current flows between the electrodes 6 and 7 and this resistance change appears as a voltage change, the volume of the particle 5 can be measured from the voltage change amount, and the particle 5 Measure the number. The inside of the tube 2 may be a negative electrode and the outside may be a positive electrode.
[0013]
The Coulter counter 8 has a computer, inputs voltage change signals of both electrodes 6 and 7, integrates the voltage change waveform to determine the volume of the particles, counts the number of voltage changes, and opens the opening 3 at a fixed time. The number of passing particles 5 and the particle size distribution of the particles 5 can be output. The first monitor 9 shows a voltage change waveform of the particles 5, and the second monitor 10 shows a histogram showing the distribution of the particles 5 by size. This device is commercially available.
[0014]
A camera 12 equipped with a strobe 11 and a microscope 13 is arranged so that the center line of the container 1 passes through the opening 3 of the tube 2. The trigger signal generator 14 inputs voltage change signals from both electrodes 6 and 7 and outputs them as voltage pulses. This voltage pulse becomes a light emission signal of the strobe 11. The camera controller 15 controls the camera 12 and outputs an image captured by the camera 12 to the image processing analysis device 16.
[0015]
The image processing analysis device 16 receives the voltage pulse from the trigger signal generator 14 and outputs it as a strobe light emission signal to the strobe 11. At this time, by setting the strobe light emission signal so that light is emitted at the rise, fall, or middle of the voltage pulse, the state before the particle 5 enters the opening 3, the state through the opening 3, and the state during the passage And so on.
[0016]
The image processing analysis device 16 inputs the particle analysis signal from the coulter counter 8 and the imaging data from the camera 12 and analyzes the image. The imaging data is the projection shape of the particle 5 and the shape and area are analyzed. By using the volume data of the particle 5 from the coulter counter 8, three-dimensional analysis of the particle is also possible. For example, if the particle 5 is known to be a spheroidal shape or a cylindrical shape, the major axis and minor axis of the ellipse, the diameter and length of the cylinder, etc. can be analyzed with high accuracy.
[0017]
The monitor 17 displays an image captured by the camera 12 and an analysis result in real time. FIG. 2 shows a situation in which the particles 5 pass through the opening 3, (A) shows a state before passing through the opening 3, (B) shows a state passing through the opening 3, and (C) shows a situation after passing through the opening 3. Show.
[0018]
FIG. 3 shows a second embodiment. The same reference numerals as those in FIG. The second embodiment is the same as the first embodiment in that the first embodiment images the transmitted light of the particles, but the reflected light is imaged. When the half mirror 19 is provided in the optical system of the microscope 18 at an angle of 45 ° with respect to the optical axis 20, and the irradiation light of the strobe 11 is irradiated from the direction perpendicular to the optical axis 20, the irradiation light reflected by the half mirror 19 is reflected by the particles 5. Then, it passes through the half mirror 19 and is imaged by the CCD color camera 21. When the transmitted light shown in FIG. 1 is imaged, the color of the particle 5 cannot be obtained because it becomes projection light, but by using reflected light as shown in FIG. 3, a clear color of the particle 5 can be obtained. Thereby, an accurate analysis of the particles 5 becomes possible.
[0019]
【The invention's effect】
As is clear from the above description, the present invention integrates the Coulter method (electric resistance method) and the image processing analysis method, which are characteristic in conventional particle measurement, using signals specific to the electric resistance method. In addition to realizing an excellent analysis method, a new three-dimensional analysis of particles has been made possible using data obtained by both methods. In addition, a state where particles pass through the opening of the tube, which could not be obtained by the electric resistance method, can be clearly imaged, and the analysis of the particles can be performed with high accuracy. A clear color image can be obtained by irradiating the illumination coaxially with the camera. Furthermore, since the particle status is displayed in real time on the monitor screen, erroneous measurement such as judging a plurality of particles as one is eliminated.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a first exemplary embodiment of the present invention.
FIG. 2 is a diagram illustrating a process in which particles pass through a tube opening.
FIG. 3 is a diagram showing a configuration of a second exemplary embodiment of the present invention.
FIG. 4 is a diagram for explaining a conventional particle measuring apparatus using the Coulter method.
FIG. 5 is a diagram for explaining a conventional particle measuring apparatus based on an image processing analysis method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Main body 2 Tube 3 Opening 4 Electrolyte solution 5 Particles 6, 7 Electrode 8 Coulter counter 9 1st monitor 10 2nd monitor 11 Strobe 12 Camera 13 Microscope 14 Trigger signal generator 15 Camera controller 16 Image processing analyzer 17 Monitor 18 Microscope 19 Half mirror 20 Optical axis 21 CCD color camera

Claims (2)

A tube with an opening is placed in the electrolyte, electrodes are provided inside and outside the tube, and the volume and number of particles are measured by measuring the change in electrical resistance between the two electrodes when the particles pass through the opening. A particle detector, a strobe that illuminates the opening at a timing when the electrical resistance changes, a camera that captures particles illuminated by the strobe, an image captured by the camera, and particle data detected by the particle detector And an image processing device for performing image analysis of particles. 2. The camera according to claim 1, wherein the camera has a half mirror in the optical system, the light from the strobe is reflected by the half mirror and irradiated with particles, and the reflected light is transmitted through the half mirror. Particle analysis equipment.

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