JP3554810B2 - Fine particle component analyzer and method for analyzing fine particles using fine particle component analyzer - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a fine particle analyzer for analyzing the components of fine particles and a method for analyzing fine particles using the fine particle analyzer, and more particularly to an analysis method for improving measurement accuracy.
[0002]
[Prior art]
For example, there is known a fine particle analyzer in which fine particles floating in the air are sucked together with air, the fine particles are collected on a filter, and the number and size of elements constituting the fine particles are measured using microwave induction plasma. .
[0003]
In this analyzer, an element whose type and particle size are known in advance is measured using a scanning microscope (SEM) or transmission electron microscopy (TEM), and then the element is analyzed by microwave. Light is emitted by an induction plasma analyzer, and the emission intensity is converted into an electric signal by a photoelectric converter and output.
[0004]
FIG. 6 shows the particle size and its distribution state. The vertical axis shows the number (expressed in%), and the horizontal axis shows the particle size. The hatched bar graph shows, for example, commercially available silicon particles having a nominal diameter of 5.0 μm. 3 shows the distribution of particle sizes measured by SEM.
Further, a bar graph indicated by multiple points shows a distribution of an output in which the silicon element measured by SEM is emitted by a plasma analyzer and the emission intensity is converted into an electric signal by a photoelectric converter.
[0005]
According to the figure, the result measured by SEM and converted into an electric signal is a graph showing almost the same distribution, and particles having a size of 5 μm have an output of about 2.522 V.
[0006]
In such a case, it can be estimated that the size is about 1.98 μm for an output of 1 V and about 3.97 μm for an output of 2 V.
Therefore, the size of the fine particles can be estimated by measuring an element having a known type and an unknown particle size under the same conditions.
[0007]
FIG. 7 shows the flow of signal processing in such an apparatus. Light emitted using microwave induction plasma enters a spectroscope 57, passes through a photomultiplier tube 58 and a preamble 59, and passes through a bandpass filter 70. Are converted into equivalent particle diameters by the cube root amplifier 66 and are converted into image signals by the calculation unit 71.
[0008]
In this case, a method is employed in which the DC component of the output signal of the photomultiplier tube 58 or the preamplifier 59 is cut using a high-pass filter having a cut-off frequency of 10 Hz and a low-pass filter having a cut-off frequency of 750 Hz. ing.
[0009]
FIG. 8 shows an output signal A (solid line) of the preamplifier 59 of such a conventional device and a result B (thin dotted line) of the arithmetic processing result when this signal passes through the band-pass filter 70, and the particle to be measured is approximately 30 ms. 3 shows a state in which three (A, B, C) continuously emit light.
[0010]
[Problems to be solved by the invention]
In this case, in the B and C particles that have been processed by passing through the band-pass filter 70, the output voltages at the rising portions I1 and A2 of the curve are lower than the 0 V level due to the undershoot of the high-pass filter 70. It has become.
As a result, there is a problem that the B and C particles are observed smaller than the actual particles, and the small particles following the large particles are not observed at all.
[0011]
FIG. 9 shows an example in which carbon particles having a nominal size of 0.75 μm are measured using such an apparatus. With such small particles, the measurement signal itself is small and close to the noise level, and there is a problem that it is difficult to distinguish the signal from the signal.
The present invention has been made in order to solve such a problem, and it is an object of the present invention to provide a fine particle measuring apparatus which has no measurement error due to undershoot and has improved measurement accuracy by providing a reference for discriminating between signal and noise. It is an object.
[0012]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a configuration for solving the above-mentioned problems.
Excitation / emission means for atomizing / ionizing the microparticles to excite / emit light, a plurality of spectroscopes for splitting a plurality of lights having different emitted wavelengths, and a predetermined wavelength provided for each of the plurality of spectrometers photoelectric conversion means for converting into electric signals, and a signal amplifying means for amplifying the electric signal converted by the photoelectric conversion means, a wavelength selection means for wavelength selection inputs an output signal from the signal amplifying means, wavelength In a fine particle component analyzer for measuring the size of the fine particles from the signal selected by the selection means,
[0013]
The wavelength selection unit is a low-pass filter, and includes a DC component calculation unit that receives an output from the signal amplification unit and outputs a DC component signal, and includes an output from the low-pass filter and an output from the DC component calculation unit. a difference calculating means for subtracting the DC component from the output of the low-pass filter to input, [0014] which is composed of a particle size calculating means for calculating the size of the fine particles based on an output signal from the differential operation means
In claim 2,
Excitation / emission means for atomizing / ionizing the microparticles to excite / emit light, a plurality of spectroscopes for splitting a plurality of lights having different emitted wavelengths, and a predetermined wavelength provided for each of the plurality of spectrometers photoelectric conversion means for converting into electric signals, and a signal amplifying means for amplifying the electric signal converted by the photoelectric conversion means, a wavelength selection means for wavelength selection inputs an output signal from the signal amplifying means, wavelength A fine particle component analysis method using a fine particle component analyzer that measures the size of the fine particles from the signal selected by the selection means ,
[0015]
Operate the particle component analyzer in the absence of particles in advance, measure the noise signal by the device itself, measure the time integral and the half width of the peak for the signal having a peak exceeding a predetermined range, and perform statistical processing. to previously obtain the value of the half-value width of the time integral and peak, at least one said previously obtained statistics of the half-value width of the time integral or peak value of the waveform for the signal having a peak in a predetermined range among the sorted signal The measurement signal or noise is determined based on the data.
[0016]
In claim 3,
A method for analyzing fine particle components using the fine particle component analyzer according to claim 1, wherein the component analysis is performed according to the following procedure .
Note 1) Prior to measuring the fine particle component , the measurement wavelength of the fine particle component analyzer is adjusted to the measurement wavelength of the fine particle to be measured.
2) The measurement is performed in the absence of fine particles , and the output of the fine particle component analyzer is measured.
3) Measure the average voltage of the output and use this as the baseline voltage.
4) The fine particle component is measured, the baseline voltage is subtracted from the measured output, and a higher voltage output is counted as the fine particle component signal.
[0017]
In claim 4,
A method for analyzing fine particle components using the fine particle component analyzer according to claim 1, wherein the component analysis is performed according to the following procedure .
Note 1) During the measurement of the fine particle component , the measurement is performed in a state where no fine particles exist, and the output of the fine particle component analyzer is measured.
2) Measure the average output voltage and use this as the baseline voltage.
3) The fine particle component is measured, the baseline voltage is subtracted from the measured output, and a higher voltage output is counted as a fine particle component signal.
[0018]
In claim 5,
A fine particle component analysis method using the fine particle component analyzer according to claim 1,
Two spectrometers set to the same measurement wavelength are used among the plurality of spectrometers, and a true output is determined from a correlation between outputs of the spectrometers .
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
First, a particle component analyzer using microwave induction plasma used in the present invention will be briefly described with reference to FIG.
In FIG. 10, reference numeral 51 denotes a filter unit, on which a filter 52 to which solid fine particles (not shown) to be measured are attached is disposed. Reference numeral 53 denotes an aspirator, which sucks solid fine particles attached to the filter 52 and supplies the fine particles to the discharge tube 54. Reference numeral 55 denotes a microwave source, and reference numeral 56 denotes a capacity into which the microwave from the microwave source 55 is introduced.
[0020]
Reference numeral 57 denotes a spectroscope which takes in the light emitted from the discharge tube 54 through the optical fiber 80 and splits the light. In this example, four spectroscopes are provided. Reference numeral 58 denotes a photoelectric conversion unit provided downstream of the spectroscope 57, for example, a photomultiplier tube. Reference numeral 71 denotes an operation means.
[0021]
FIG. 1 shows an example of a calculating means of the particle analyzer according to claim 1 of the present invention. An electric signal borrowed by a photomultiplier tube 58 is amplified by a preamplifier 59, and the signal is converted into a low-pass filter 60 and a DC signal. It is input to the component operation circuit 61. The electric signal input to the DC component calculation circuit 61 is output to the calculation unit 63 via the selector 62 connected to the contact A, and is stored in a memory (not shown) constituting the calculation unit 63. When the DC component is stored in the memory, the operation unit 63 issues a switching signal to the selector 62 and connects the connection to the contact B.
[0022]
The DC component signal stored in the memory is converted to an analog signal by the D / A converter 64 and input to one terminal of the difference calculation circuit 65.
The signal that has passed through the low-pass filter 60 is input to the other terminal of the difference operation circuit 65, and a difference operation is performed to remove a DC component from the signal that has passed through the low-pass filter 60. The output of the difference calculation circuit 65 is input to a cube root amplifier 66 to determine an equivalent particle size, and the signal is sent to a calculation unit 63 via a contact B of a selector 62 to perform a predetermined calculation and a monitor 67 Visualized by
[0023]
Returning to FIG. 8, the thick dotted line C indicates the result of the arithmetic processing according to the present invention, and it can be seen that the rising of the second and subsequent waveforms (ha1, ha2) is near zero V, and the undershoot is eliminated.
[0024]
By the way, as described above with reference to FIG. 9, the signal level of fine particles having a small size of sub-μm is low, so that it is difficult to distinguish them from noise signals.
Therefore, in claim 2 of the present invention, in addition to the peak detection, the time integration of the signal including the peak and the half width of the peak are measured.
[0025]
That is, the apparatus is operated with no particles in the filter, and a noise signal by the apparatus itself such as the photomultiplier tube 58 and the preamplifier 59 is measured. Then, with respect to a signal having a peak exceeding a predetermined range, the time integral and the half width of the peak are measured, and statistical processing is performed to determine the values of the time integral and the half width of the peak.
[0026]
Next, sub-μm particles having known element names are collected by a filter, and ordinary measurement is performed. FIG. 2 shows a measurement example of carbon particles having a particle size of 0.7511 m. Here, signals A and B having peaks of 4 mV or more are injected.
[0027]
When the time integral of the signal of interest and the value of the half width of the peak are obtained, the half width of the signal of A is relatively long, 4.2 ms, the half width of the signal of B is 2.0 ms, and the signal of A is The time integration of the A signal is about 24.9 V · ms, the time integration of the B signal is 9.3 V · ms, and the time integration of the A signal is 2.7 times that of the B signal. . Therefore, here, the signal of A is picked up as a signal from the fine particles.
[0028]
Figure 3 shows an example of measurement of the number of mixing carbon particles with a nominal 3.8μm and 5.4μm particles as a measurement sample, the line segment indicated by dotted line number of theory, the mark ◇ in the solid line line segment shown by biasing the line segments shown by urging of the present invention, the × mark the solid line is the number measured by the conventional apparatus.
[0029]
As is clear from the figure, the number of line segments x marks measured by the conventional apparatus shows a variation in the particle frequency, but the line segments marked with the を mark using the apparatus of the present invention agree well with the theoretical values. You can see that.
[0030]
FIG. 4 is a flowchart showing a process of performing the latter half value width calculation after the peak detection and performing the integral calculation to determine the signal. Note that the half-width calculation and the integration calculation are performed based on known software techniques, but these calculations may be performed on both or any of them depending on the type and size of the element.
[0031]
In the above description, carbon was used as the element to be measured, and the time integral and the half width of the peak were compared, and the larger one was used as the fine particle signal. However, some elements were smaller than the time integral of noise and the half width of the peak. In such a case, it is appropriately determined which one is used as the measurement signal. Some types of elements are almost equal to noise, but such elements cannot be determined.
[0032]
According to claim 2, the apparatus is operated in a state where there is no fine particle in the filter, a noise signal by the apparatus itself such as the photomultiplier tube 58 and the preamble 59 is measured, and a signal having a peak exceeding a predetermined range is subjected to time integration. The half width of the peak was measured, statistical processing was performed to determine the time integration and the half width of the peak, and the half width of the noise was compared with the half width of the signal emitted from the fine particles to determine the signal.
[0033]
In claims 3 and 4, the apparatus is operated with no particles in the filter (Claim 3 creates a state in which no particles are contained ... no light emission ... multiple times during the start of measurement; claim 4). The output voltage including noise and background is used as a baseline. Then, when measuring the fine particles, a signal exceeding the base line is determined as a signal due to the emission of the fine particles.
[0034]
That is, according to the third aspect, since a baseline is first determined by including an average of inherent instrumental errors and noises inherent in the analyzer, and whether the signal or noise is determined based on the baseline, highly accurate measurement can be performed.
In the fourth aspect, since the measurement is performed while always correcting the baseline, more accurate measurement can be performed than the method of the third aspect.
[0035]
According to the fifth aspect, two spectrometers set to the same measurement wavelength are used, and the light emission of the fine particles is simultaneously measured by these spectrometers . FIG. 5 shows the results obtained by simultaneously measuring the nominal 1 μm latex with two strings and superimposing the outputs of the two spectrometers. The solid line indicates the output of the spectrometer 1 and the dotted line indicates the output of the spectrometer 2. .
[0036]
Here, for example, when the output exceeding 220 mV is set as the output of the fine particles, the output shown in (a) shows both the outputs exceeding 220 mV, the output shown in (b) shows only the spectroscope 2 and the output shown in (c). The output of the portion is the output of only the spectroscope 1. In such a case, the output of the portion (a) is determined to be a fine particle signal, and the outputs of the portions (b) and (c) are determined to be noise signals.
[0037]
The signals from the two analyzers may be added, or one signal may be subtracted from the other signal. In short, any method may be used as long as it can discriminate between the signal and the noise.
[0038]
It should be noted that the foregoing description of the invention merely illustrates certain preferred embodiments for purposes of explanation and illustration. Thus, it will be apparent to one skilled in the art that the present invention may be modified or modified in many ways without departing from its essentials. For example, the element to be measured is not limited to carbon, but may be applied to any element having a half width and a time integral different from that of the noise signal.
[0039]
【The invention's effect】
According to the present invention as described in detail above, excitation / emission means for atomizing / ionizing fine particles to excite / emit light, a plurality of spectroscopes for dispersing a plurality of emitted lights having different wavelengths , input and photoelectric conversion means for converting a predetermined wavelength that is spectrally provided in each of the spectrometer into an electric signal, a signal amplifying means for amplifying the electric signal converted by the photoelectric conversion means, an output signal from the signal amplifying means A wavelength selection means for performing wavelength selection, and a fine particle component analyzer for measuring the size of the fine particles from the signal selected by the wavelength selection means,
[0040]
The wavelength selection unit is a low-pass filter, and includes a DC component calculation unit that receives an output from the signal amplification unit and outputs a DC component signal, and includes an output from the low-pass filter and an output from the DC component calculation unit. And a particle size calculation means for calculating the size of the fine particles based on an output signal from the difference calculation means. A fine particle component analyzer having no measurement error can be provided.
[0041]
In addition, the fine particle component analyzer is operated in the absence of fine particles in advance, a noise signal is measured by the device itself, and a signal having a peak exceeding a predetermined range is measured for time integration and a half width of the peak, and statistical processing is performed. The values of the time integral and the half-value width of the peak are determined in advance, and for the signal having a peak in a predetermined range among the selected signals, at least one of the time integral of the waveform or the half-value width of the peak value is obtained in advance. Since the determination of the measurement signal or the noise is performed based on the statistical data, it is possible to provide a fine particle component analyzer capable of accurately measuring even a small particle size.
In addition, since a baseline is first determined including an inherent instrumental difference and an average value of noise of the analyzer, and whether the signal or the noise is determined based on the baseline, highly accurate measurement can be performed.
In addition, more accurate measurement can be performed by performing measurement while always correcting the baseline.
Further, among the plurality of the spectrometer, the spectrometer was set to the same measurement wavelength using two, since the correlation between the outputs of the spectrometer to perform the determination of the true output, the noise or signal of determination accuracy Can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a calculating means of the fine particle component analyzer of the present invention.
FIG. 2 is a view showing a measurement example of carbon fine particles.
FIG. 3 is a diagram showing an example in which two types of carbon fine particles are mixed and the number of fine particles is measured.
FIG. 4 is a diagram showing a flow from detection of a peak to calculation of a half-value width and integration calculation to signal discrimination.
FIG. 5 is a diagram in which outputs measured simultaneously by two spectrometers are superimposed.
FIG. 6 is a diagram showing an example of a particle size and a distribution state thereof.
FIG. 7 is a diagram showing a flow of signal processing of the fine particle component analyzer.
FIG. 8 is a diagram showing a result of arithmetic processing by a conventional device.
FIG. 9 is a diagram showing an example of measuring sub-μm carbon fine particles.
FIG. 10 is a diagram showing a general configuration example of a fine particle component analyzer.
[0042]
[Explanation of symbols]
Reference Signs List 51 filter unit 52 filter 53 aspirator 54 reaction tube 55 microwave source 56 cavity 57 spectroscope 58 photoelectric converter (photomultiplier tube) 59 preamplifier 60 low-pass filter 61 DC component calculation circuit 62 selector 63 calculation unit 64 D / A converter 65 Difference calculator 66 Third root amplifier 67 Monitor

Claims (5)

Excitation / emission means for atomizing / ionizing the microparticles to excite / emit light, a plurality of spectroscopes for splitting a plurality of lights having different emitted wavelengths, and a predetermined wavelength provided for each of the plurality of spectrometers photoelectric conversion means for converting into electric signals, and a signal amplifying means for amplifying the electric signal converted by the photoelectric conversion means, a wavelength selection means for wavelength selection inputs an output signal from the signal amplifying means, wavelength In a fine particle component analyzer that measures the size of the fine particles from the signal selected by the selection means,
The wavelength selection unit is a low-pass filter, and includes a DC component calculation unit that receives an output from the signal amplification unit and outputs a DC component signal, and includes an output from the low-pass filter and an output from the DC component calculation unit. And a difference calculation means for subtracting a DC component from the output of the low-pass filter and a particle size calculation means for calculating the size of the fine particles based on an output signal from the difference calculation means. Fine particle component analyzer. Excitation / emission means for atomizing / ionizing the microparticles to excite / emit light, a plurality of spectroscopes for splitting a plurality of lights having different emitted wavelengths, and a predetermined wavelength provided for each of the plurality of spectrometers photoelectric conversion means for converting into electric signals, and a signal amplifying means for amplifying the electric signal converted by the photoelectric conversion means, a wavelength selection means for wavelength selection inputs an output signal from the signal amplifying means, wavelength a fine particles components partial析方method using a particle component analyzer for measuring the sizes of the particles from the sorted signal selecting means,
Operate the particle component analyzer in the absence of particles in advance, measure the noise signal by the device itself, measure the time integral and the half width of the peak for the signal having a peak exceeding a predetermined range, and perform statistical processing. to previously obtain the value of the half-value width of the time integral and peak, at least one said previously obtained statistics of the half-value width of the time integral or peak value of the waveform for the signal having a peak in a predetermined range among the sorted signal A method for analyzing a fine particle component using a fine particle component analyzer, wherein a determination of a measurement signal or noise is performed based on data. A method for analyzing a fine particle component using the fine particle component analyzer according to claim 1, wherein the component analysis is performed according to the following procedure .
Note 1) Prior to measuring the fine particle component , the measurement wavelength of the fine particle component analyzer is adjusted to the measurement wavelength of the fine particle to be measured.
2) The measurement is performed in the absence of fine particles, and the output of the fine particle component analyzer is measured.
3) Measure the average voltage of the output and use this as the baseline voltage.
4) The fine particle component is measured, the baseline voltage is subtracted from the measured output, and a higher voltage output is counted as the fine particle component signal. A method for analyzing a fine particle component using the fine particle component analyzer according to claim 1, wherein the component analysis is performed according to the following procedure .
Note 1) During the measurement of the fine particle component , the measurement is performed in a state where no fine particles exist, and the output of the fine particle component analyzer is measured.
2) Measure the average output voltage and use this as the baseline voltage.
3) The fine particle component is measured, the baseline voltage is subtracted from the measured output, and a higher voltage output is counted as a fine particle component signal. Among the plurality of spectrometer, the spectrometer was set to the same measurement wavelength using two, according to claim 1, in which the correlation between the outputs of the spectroscope, characterized in that to carry out the determination of the true output A fine particle component analysis method using a fine particle component analyzer.

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