JP6901145B2 - Component composition measurement system and component composition measurement method - Google Patents

Description

The present invention relates to an apparatus and a method for measuring a component composition to be measured by using laser-induced breakdown spectroscopy.

Laser Induced Breakdown Spectroscopy (LIBS) is a method for analyzing the component composition of a substance. In laser-induced breakdown spectroscopy, the surface of a measurement target is irradiated with a laser beam to generate plasma, and the emission spectrum of the plasma is analyzed to measure the elemental components constituting the inspection target.

n_(i)は元素iの濃度，K_(i),jはアインシュタイン係数を含む変数，g_(i),jは縮退度，E_(i),jは上位エネルギー、K_Bはボルツマン定数、Tはプラズマ温度を示す。定量分析を行う場合、プラズマ温度など，発光強度I_(i)に影響を与える要素の明確化が重要となる。More specifically, in laser-induced breakdown spectroscopy, a laser is focused and irradiated to a measurement target, and the surface of the measurement target is rapidly heated to generate a plasma containing excited ions on the surface of the measurement target. Generate. When the excited electrons fall to low energy levels, they emit light with a component-specific frequency. Since the emission intensity correlates with the atomic number density, it is possible to identify and measure the substance existing in the measurement target by obtaining the wavelength and the spectral line intensity of each spectrum. Here, the emission spectral intensity Ii of the atom i due to spontaneous emission is expressed by the following equation.

n _(i) is the concentration of element i, K _{(i), j} are variables including Einstein coefficients, g _{(i), j} are degeneracy degrees, E _{(i), j} are higher energies, K _B is Boltzmann constant, T Indicates the plasma temperature. When performing quantitative analysis, it is important to clarify the factors that affect _{the emission intensity I (i), such as plasma temperature.}

Laser-induced breakdown spectroscopy is applied for quantitative and elemental analysis on various samples. For example, Patent Document 1 discloses a system for detecting harmful substances in waste wood using laser-induced breakdown spectroscopy. The system of Patent Document 1 is a system for detecting harmful substances in waste wood, and is a transport device for transporting waste wood and a laser-induced breakdown (laser-induced breakdown) for detecting harmful substances in waste wood transported to the transport device. It consists of a LIBS) device and a sorting device that separates only harmful wood containing harmful substances from harmless wood by a signal from a laser-induced breakdown device. According to the system of Patent Document 1, harmful substances such as preservatives applied to waste wood from buildings and the like can be detected easily and quickly in real time.

Further, Patent Document 2 and Non-Patent Document 1 disclose a LIBS apparatus using a short laser pulse and a long laser pulse. Patent Document 2 discloses a LIBS apparatus in which a short laser pulse that causes breakdown and a long laser pulse that does not cause breakdown by itself are combined. Non-Patent Document 1 discloses a LIBS apparatus in which the optical axes of a short laser pulse and a long laser pulse are aligned.

Japanese Unexamined Patent Publication No. 2007-10371 U.S. Pat. No. 8,125,627

“Double-pulse LIBS combining short and long nanosecond pulses in the microjoule range”, Islam Y. Elnasharty et al., J. Anal. At. Spectrom., 2014, 29, 1660-1666.

Laser-induced breakdown spectroscopy has the advantage of being able to measure the elemental composition of the object to be measured in real time, but on the other hand, it is applicable where the accuracy decreases when the plasma generation process fluctuates and the position or shape of the object changes. There is a problem that it is difficult.

An object of the present invention is to provide an apparatus and method for analyzing the composition of a measurement target by using laser-induced breakdown spectroscopy, which enables accurate composition analysis.

The component composition measurement system according to the present invention includes a first laser light source that irradiates a measurement target with a first laser beam having an intensity sufficient to generate plasma, and a second laser having an intensity not to generate plasma. From the second laser light source that irradiates the measurement target with light and the emission of plasma generated by the irradiation of the first laser light from the first laser light source to the measurement target, the emission spectrum showing the intensity for each wavelength is measured. It includes a spectrum measuring device and a control device that analyzes the composition of the measurement target using the measured emission spectrum data. The second laser light source starts the irradiation of the second laser beam before the start of the irradiation of the first laser beam, and ends the irradiation of the second laser beam after the irradiation of the first laser beam is completed.

In the component composition measuring method according to the present invention, a step of irradiating a measurement target with a first laser beam having an intensity sufficient to generate plasma and a second laser beam having an intensity not to generate plasma are measured. Using the data of the measured emission spectrum and the step of irradiating the emission spectrum showing the intensity of each wavelength from the emission of plasma generated by irradiating the measurement target of the first laser beam. It includes a step of analyzing the composition of the measurement target. The irradiation of the second laser beam is started before the start of the irradiation of the first laser beam, and the irradiation of the second laser beam is terminated after the irradiation of the first laser beam is completed.

According to the component composition measurement system and the component composition measurement method of the present invention, the measurement target before plasma generation can be heated, the temperature (intensity) of the once generated plasma can be maintained, and the decrease (attenuation) thereof can be delayed. it can. As a result, a spectrum including a high-level signal that does not depend on the properties of the measurement target can be obtained, so that high measurement accuracy can be ensured.

The figure which showed the structure of the component composition measurement system in Embodiment 1 of this invention. The figure explaining the time-dependent change of the emission intensity and emission spectrum observed in laser-induced breakdown spectroscopy (LIBS). The figure explaining the timing of laser pulse irradiation and plasma measurement in a component composition measurement system. Flowchart showing the operation of the component composition measurement system A diagram illustrating an example of a spectrum observed in laser-induced breakdown spectroscopy. The figure which showed the structure of the component composition measurement system in Embodiment 2 of this invention. The figure explaining the double pulse irradiation in Embodiment 2. (A) A diagram showing a change in plasma emission intensity when single pulse irradiation is applied, and (B) a diagram showing a change in plasma emission intensity when double pulse irradiation is applied. The figure explaining the waveform of each pulse used for the 1st and 2nd measurement Figure showing the result of the first measurement (Measurement target = iron plate (stainless steel plate) installed in the air) Figure showing the result of the second measurement (Measurement target = aluminum plate installed in water) The figure explaining the irradiation timing in various irradiation methods of a laser pulse. The figure which showed the measurement result performed on the sample which the surface was polished The figure which showed the measurement result performed on the sample which the surface was rusted (A) A diagram showing an SEM image of the surface of the measurement target after single-pulse irradiation of the measurement target, and (B) a diagram showing an SEM image of the surface of the measurement target after double-pulse irradiation of the measurement target. The figure which showed the measurement result when single pulse irradiation or double pulse irradiation (after) was performed on solid steel and molten steel in order to confirm the pretreatment effect (heating effect). The figure which showed the measurement result when double pulse irradiation (pre) was performed on solid steel and molten steel in order to confirm the pretreatment effect (heating effect). The figure which shows the example of the structure of the light source device which can irradiate two kinds of laser light.

Hereinafter, embodiments of the component composition measurement system according to the present invention will be described with reference to the accompanying drawings. The component composition measurement system described below is a system that measures the composition of the measurement target using laser-induced breakdown spectroscopy (LIBS).

(Embodiment 1)
1. 1. System Configuration FIG. 1 shows the configuration of the first embodiment of the component composition measurement system of the present invention. The component composition measurement system 100 includes a laser light source 10, a beam splitter 12, a focus lens 14, a focus adjustment unit 16, an optical path changing optical member 18, an irradiation position changing unit 20, a condenser lens 22, and spectrum measurement. A device 30, a three-dimensional shape measuring device 40, and a control device 50 (analyzing device) are provided.

The laser light source 10 is a light source device having an intensity that does not generate plasma and capable of outputting laser light in a predetermined wavelength band, and is composed of, for example, a YAG laser.

The focus adjusting unit 16 is a means for adjusting the focus of the laser beam emitted from the laser light source 10, and includes a motor, an actuator, and the like for moving the focus lens 14 along the optical axis.

The optical path changing optical member 18 is an optical member for changing the optical path of the laser beam emitted from the laser light source 10, and is composed of a mirror, a prism, flat glass, or the like. The irradiation position changing unit 20 is a means for rotating or translating the optical path changing optical member 18 in order to change the optical path of the laser beam, and includes a motor, an actuator, and the like.

The beam splitter 12 has a function of transmitting the laser light emitted from the laser light source 10 and reflecting the light incident from the measurement target 200 side to the spectrum measuring device 30 side.

The spectrum measuring device 30 is a device that measures the intensity distribution (emission spectrum) for each wavelength with respect to the incident light. The spectrum measuring device 30 includes a spectroscope 32 and an ICCD (Intensified Charge Coupled Device) camera 35. The spectroscope 32 includes, for example, a diffraction grating or a bandpass filter. The ICCD camera 35 generates an emission spectrum by converting a light signal spatially modulated based on a wavelength by a spectroscope 32 into an electric signal (image signal). The spectrum measuring device 30 is not limited to the configuration shown in FIG. 1, and may have any configuration as long as it can measure the emission spectrum.

The three-dimensional shape measuring device 40 is a device that three-dimensionally measures the shape (that is, the distance) of the measurement target 200. As the three-dimensional measuring device, any configuration (technology) can be used as long as the configuration can measure the three-dimensional shape of the object. For example, the three-dimensional measuring device 40 may include a TOF (Time Of Flight) sensor. Alternatively, the three-dimensional measuring device 40 includes two cameras arranged at different positions, and three-dimensionally measures the shape of the measurement target by the stereo method using the images taken by the two cameras. You may. The three-dimensional shape measuring device 40 transmits information indicating the measurement result of the measurement target 200 to the control device 50.

The control device 50 (analyzer) acquires the emission spectrum data from the spectrum measurement device 30, analyzes the data, and analyzes the component composition of the measurement target 200. In addition to the analysis of the emission spectrum, the control device 50 determines the shape and distance of the measurement target 200 based on the measurement result by the three-dimensional shape measurement device 40, and changes the focus adjustment unit 16 and the irradiation position based on the determination result. It also controls the unit 20. The control device 50 is an information processing device (for example, a personal computer) including a CPU, and realizes a predetermined function when the CPU executes a predetermined program. The emission spectrum analysis function and the control functions of the focus adjusting unit 16 and the irradiation position changing unit 20 may be realized by separate computers (CPUs). Further, instead of realizing the function of the control device 50 by a combination of hardware (CPU) and software, it may be realized only by hardware (electronic circuit) specially designed to realize a predetermined function. .. That is, the control device 50 may include an MPU, DSP, FPGA, ASIC, or the like instead of the CPU.

2. Operation of the system The operation of the component composition measurement system 100 configured as described above will be described. The component composition measurement system 100 measures the composition of the measurement target 200 using laser-induced breakdown spectroscopy (LIBS).

The component composition measurement system 100 irradiates the surface of the measurement target 200 with laser light from the laser light source 10. The focus of the irradiated laser beam is adjusted by the focus adjusting unit 16. Further, the irradiation position of the laser beam (that is, the optical path of the laser beam) on the measurement target 200 is changed by the irradiation position changing unit 20. The three-dimensional shape measuring device 40 three-dimensionally measures the shape (distance) of the measurement target 200 and transmits it to the control device 50. The control device 50 controls the focus adjusting unit 16 and the irradiation position changing unit 20 based on the measurement results from the three-dimensional shape measuring device 40.

The laser light source 10 irradiates a pulsed laser beam (laser pulse). The laser beam (laser pulse) passes through the focus lens 14, the optical path changing optical member 18, and the beam splitter 12 and irradiates the surface of the measurement target 200. When the surface of the measurement target 200 is irradiated with the laser beam, high-temperature plasma is generated on the surface of the measurement target 200. The light emitted from the plasma is reflected by the beam splitter 12 and incident on the spectrum measuring device 30 via the lens 22.

The spectrum measuring device 30 measures the intensity of light from the plasma for each wavelength to obtain an emission spectrum. The data of this emission spectrum is transmitted to the control device 50. The control device 50 analyzes the emission spectrum data to analyze the composition of the measurement target 200.

FIG. 2 is a diagram illustrating laser-induced breakdown spectroscopy. FIG. 2A is a diagram showing changes over time in plasma emission observed in laser-induced breakdown spectroscopy. As shown in FIG. 2A, when a laser beam (laser pulse) is applied to the surface of the measurement target at time t0, plasma is generated on the surface of the measurement target. The emission intensity of the plasma reaches the maximum value immediately after the laser pulse irradiation, and then decreases as the plasma cools with the passage of time. Atomic emission is measured in the cooling process of this plasma. The composition of the measurement target is measured based on the atomic emission measured at this time.

2 (B), (C), and (D) are diagrams showing emission spectra observed with plasma emission shown in FIG. 2 (A), and emission observed at time t1, t2, and t3, respectively. The spectrum is shown. At time t1 immediately after the laser pulse irradiation, as shown in FIG. 2 (B), since the noise due to blackbody radiation is large, the spectrum of atomic emission is hidden by the noise and cannot be observed. Over time, as shown in FIGS. 2 (C) and 2 (D), when the noise is reduced and the level of atomic emission relative to the noise is high (that is, when the S / N ratio is high), the atomic emission is emitted. It becomes observable.

Therefore, in the component composition measurement system 100, as shown in FIG. 3, after a predetermined delay time (D) elapses from the irradiation of the laser pulse, plasma emission, that is, atomic emission is performed for an observation time (Tm) of a predetermined width. Make a measurement. The delay time (D) is set to a time during which noise is sufficiently reduced and atomic emission can be sufficiently observed (that is, a time at which a sufficient S / N ratio can be obtained).

Here, even if the delay time (D) and the observation time (Tm) are constant, if the state of the generated plasma fluctuates for each measurement, the observed atomic emission also fluctuates greatly, making accurate measurement difficult. Become. Therefore, the component composition measurement system 100 of the present embodiment controls the irradiation conditions of the laser pulse so that the state of the generated plasma does not fluctuate, and further analyzes the measurement results measured in the fluctuating plasma state. Avoid using it. This improves the accuracy of composition analysis.

Hereinafter, the operation of the component composition measurement system 100 will be described with reference to the flowchart of FIG.

In the component composition measurement system 100, the shape and distance of the measurement target 200 are measured by the three-dimensional shape measuring device 40 (S11). The measurement result is transmitted to the control device 50.

Based on the measurement results (distance, shape) of the three-dimensional shape measuring device 40, the control device 50 has a shape change in which the measurement target 200 is in the in-focus position and the shape at the laser pulse irradiation position on the measurement target is sharply reduced. It is determined whether or not the region is flat without any (S12).

The control device 50 determines the distance of the laser pulse irradiation position portion of the measurement target 200 based on the measurement result of the three-dimensional shape measurement device 40, and determines whether or not the measurement target 200 is in the in-focus position from the distance. to decide. Further, the control device 50 determines the shape of the region of the laser pulse irradiation position on the measurement target 200 based on the measurement result by the three-dimensional shape measuring device 40, and the region has a flat shape without a sudden decrease in shape change. Determine if it exists. Whether or not the shape is flat without a sudden decrease in shape is determined based on, for example, the angle between the laser irradiation direction and the measurement surface. Specifically, when the angle formed by the laser irradiation direction and the measurement surface is equal to or less than a predetermined angle (X °), it is determined that the shape is flat without a sudden decrease in shape change. The control device 50 stores information on a predetermined angle (X °), calculates the laser irradiation direction and the angle of the measurement surface from the shape measurement result, and compares the calculated angle with the predetermined angle (X °). Therefore, it is determined whether or not the shape is a flat shape without a sudden decrease in shape change. The angle X is set according to the measurement target (for example, iron material, slag, molten metal, etc.).

At least, when the measurement target 200 is not in the in-focus position or the shape at the irradiation position of the laser pulse on the measurement target 200 is not flat (when there is a sudden decrease in shape change) (NO in S12), the control device 50 uses the laser beam. The irradiation conditions of (S19) are adjusted.

That is, when the measurement target 200 is not in the in-focus position, the control device 50 controls the focus adjusting unit 16 so that the measurement target 200 is in the in-focus position, and adjusts the position of the focus lens 14. As a result, even if the position of the measurement target 200 fluctuates, the laser beam can be irradiated in a state where the measurement target 200 is always in focus.

Further, when the shape at the irradiation position of the laser pulse on the measurement target 200 is not flat (that is, when there is a sudden decrease in shape change), the control device 50 causes the laser pulse on the measurement target 200 to be flat on the measurement target 200. The irradiation position changing unit 20 is controlled to change the irradiation position of the laser pulse so that the region (that is, the region where there is no sudden decrease in shape) is irradiated (S19). After that, the process returns to step S11.

Here, the reason for controlling the laser beam to irradiate a flat region as described above will be described. The temperature of the generated plasma differs between the case where the flat region is irradiated with the laser beam and the case where the region where the shape changes suddenly is irradiated with the laser beam. In the region where there is a sudden shape change, the laser irradiation area mainly increases, and the amount of laser energy irradiated per unit area decreases. When the angle between the laser irradiation direction and the measurement surface is X °, the amount of laser energy emitted per unit area is sin (X) times. sin (X) is 1 or less, and when X = 90 ° (a laser beam perpendicular to the measurement surface is irradiated), sin (X) = 1 and X = 45 ° (angle of 45 ° with respect to the measurement surface). When the laser beam is irradiated), sin (X) = 1 / √2. That is, as the angle X deviates from 90 °, the amount of attenuation of the amount of energy irradiated per unit area increases. Therefore, the temperature of the plasma generated by irradiating the region having a sudden shape change (that is, the region having irregularities) with the laser beam is lower than the temperature of the plasma generated by irradiating the flat region with the laser beam. As described above, the state (temperature) of the generated plasma differs depending on the shape of the irradiation region of the laser beam, and the fluctuation of the plasma state affects the measurement accuracy. Therefore, in order to reduce such fluctuations in the plasma state, in the present embodiment, the shape of the measurement target 200 is determined and the laser beam is controlled to irradiate a flat region (S12, S19). ..

On the other hand, when the measurement target 200 is in the in-focus position and the shape at the laser pulse irradiation position on the measurement target is flat (that is, when there is no sudden decrease in shape change) (YES in S12), the control device 50 Irradiates a laser pulse from the laser light source 10 to generate plasma on the surface of the measurement target 200, and acquires an emission spectrum from the plasma (S13).

The control device 50 calculates the signal intensity and the plasma temperature from the acquired emission spectrum (S14). The signal intensity of the emission spectrum may be calculated using, for example, the signal intensity of a predetermined element, or may be calculated using the signal intensity indicating the maximum amplitude.

The plasma temperature can be calculated from the emission spectrum by the following method. FIG. 5 shows an emission spectrum obtained from plasma. In the emission spectrum of the plasma shown in FIG. 5, a plurality of spectra due to magnesium (Mg) are observed. _{The intensity ratio (I Mg1} / I _Mg2 ) of the spectra (Mg1 and Mg2) of the plurality of magnesiums varies depending on the temperature. Therefore, the temperature of the plasma can be detected by detecting _{the intensity ratio (I Mg1} / I _Mg2 ) of a plurality of magnesium spectra (Mg1 and Mg2). The spectrum used in temperature detection is not limited to the spectrum of magnesium, and the spectrum of other elements (iron, aluminum, etc.) may be used.

Returning to the flowchart of FIG. 4, the control device 50 determines whether or not the calculated signal strength and plasma temperature are within the predetermined ranges (S15). For example, the control device 50 determines whether or not the calculated signal strength is equal to or greater than a predetermined value, and determines whether or not the plasma temperature is equal to or greater than a predetermined value. If at least one of the signal strength and the plasma temperature is not within the predetermined range (NO in S15), the control device 50 returns to step S11. In this case, the measured data is not used for composition analysis. The laser beam irradiation position may be changed before returning to step S11.

On the other hand, when both the signal strength and the plasma temperature are within a predetermined range (YES in S15), the control device 50 integrates the signal strength data measured at that time with the signal strength data measured in the past. (S16).

As described above, in the present embodiment, when at least one of the signal intensity and the plasma temperature does not satisfy a predetermined condition, the measurement result is not used. That is, only the measurement results showing a good plasma state in which the plasma state satisfies certain conditions (signal intensity, temperature) are used. By using only the measurement results showing a good plasma state in this way, the deterioration of the measurement accuracy is prevented.

The control device 50 determines whether or not the number of times the signal intensities of the spectrum are integrated has reached a predetermined number of times of integration (S17). When the predetermined number of integrations has not been reached (NO in S17), the control device 50 returns to step S11 and repeats the above processes (S11 to S16) to acquire data for the predetermined number of integrations. The laser beam irradiation position may be changed before returning to step S11. In this way, by integrating and using the measurement data of a plurality of times, the influence of noise is eliminated and the measurement accuracy is improved. When the predetermined number of integrations is reached (YES in S17), the control device 50 calculates the concentration of each element constituting the measurement target 200 from the spectrum in which the signal strength is integrated (S18). The calculated density information may be recorded on a recording medium (SSD, HDD) in the control device 50, displayed on a display, or printed by a printer. Alternatively, it may be transmitted to another device (control device, server, etc.).

3. 3. Summary As described above, the component composition measurement system 100 of the present embodiment has a laser light source (10) that irradiates a measurement target 200 with a laser beam (laser pulse) and a laser light from the laser light source to the measurement target 200. A spectrum measuring device 30 for measuring an emission spectrum indicating the intensity of each wavelength from the emission of plasma generated by irradiation, and a control device 50 for analyzing the composition of a measurement target using the measured emission spectrum data are provided. .. The control device 50 determines the properties of the emission spectrum (S15 in FIG. 4), and analyzes the composition of the measurement target using only the data of the emission spectrum whose properties are in a predetermined state.

As described above, according to the component composition measurement system 100 of the present embodiment, when applying the laser-induced breakdown spectroscopy, the properties of the emission spectrum may be determined, and the accuracy may decrease based on the properties. Exclude the signal from the data used for analysis. As a result, fluctuations in the state of the generated plasma can be reduced, and high measurement accuracy can be ensured.

For example, the control device 50 may determine the temperature and / or signal intensity of the plasma from the emission spectrum (S15), and analyze the composition of the measurement target using the emission spectrum in which the plasma temperature is equal to or higher than a predetermined temperature.

Further, the component composition measurement system 100 may measure the emission spectrum a plurality of times and analyze the composition of the measurement target using the result of integrating the data of the plurality of emission spectra. The accuracy of the measured data can be improved by integrating and using the data measured a plurality of times.

Further, the component composition measurement system 100 includes a three-dimensional shape measuring device 40 that measures the three-dimensional shape of the measurement target 200, and a focus adjusting unit 16 that adjusts the focal length of the laser beam emitted from the laser light source 10 to the measurement target. You may also prepare for it.

The control device 50 may control the focus adjusting unit 16 based on the measurement result by the three-dimensional shape measuring device 40 to adjust the focal length of the laser beam. As a result, the measurement target 200 can be always focused and irradiated with the laser beam without depending on the shape (distance) of the measurement target 200, and the laser beam can be irradiated with a constant intensity. Therefore, the emission spectrum in a constant state can be obtained regardless of the shape of the measurement target 200, and the accuracy of the measurement data is improved.

Further, the component composition measurement system 100 may further include an irradiation position changing unit 20 for adjusting the irradiation position on the measurement target of the laser beam. The control device 50 may control the irradiation position changing unit 20 based on the measurement result by the three-dimensional shape measuring device 40 to adjust the irradiation position of the laser beam on the measurement target 200. As a result, the laser beam can be irradiated to a position (region) where a good plasma state can be obtained, an emission spectrum in a constant state can be obtained regardless of the shape of the measurement target, and the accuracy of the measurement data is improved.

(Embodiment 2)
In the first embodiment, as shown in FIG. 3, the measurement target 200 is irradiated with one type of laser pulse to generate plasma. On the other hand, in the present embodiment, in addition to the laser pulse for generating plasma, a second laser pulse having an intensity that does not generate plasma is further irradiated. By irradiating the second laser pulse in this way, the intensity of the generated plasma can be stabilized at a high level, and the intensity of the signal indicating atomic emission can be stabilized regardless of the fluctuation of the plasma.

In the following description, irradiating only the laser pulse for generating plasma as in the first embodiment is referred to as "single pulse irradiation", and is for generating plasma as in the present embodiment. Irradiation of another laser pulse in order to maintain the plasma temperature in addition to the irradiation of the laser pulse of the above is called "double pulse irradiation".

1. 1. Configuration diagram 6 of the system is a diagram showing the configuration of the component composition measurement system according to the second embodiment. The component composition measurement system 100b according to the second embodiment further includes a second laser light source 10b and a beam combiner 24 in addition to the configuration of the component composition measurement system 100 according to the first embodiment. Hereinafter, the laser light source 10 is referred to as a "first laser light source". The beam combiner 24 is an optical member for synthesizing the laser beam from the first laser light source 10 and the laser beam from the second laser light source 10b and guiding them to the beam splitter 12. The first and second laser light sources 10 so that the laser light from the first laser light source 10 and the laser light from the second laser light source 10b irradiate the measurement target 200 with their optical axes aligned. The optical axis of 10b is adjusted.

2. Double pulse irradiation FIG. 7 is a diagram illustrating laser pulses emitted from the first and second laser light sources 10 and 10b. As shown in FIG. 7, the laser pulse (hereinafter also referred to as “long pulse”) L2 output from the second laser light source 10b is a laser pulse (hereinafter also referred to as “short pulse”) output from the first laser light source 10. It has a pulse width sufficiently larger than the pulse width of L1. For example, the pulse width of the laser pulse L1 from the first laser light source 10 is 6 ns, while the pulse width of the laser pulse L2 from the second laser light source 10b is 10,000 ns. The intensity of the laser pulse L1 output from the first laser light source 10 is set to such an intensity that plasma can be generated by itself. On the other hand, the intensity of the laser pulse L2 output from the second laser light source 10b is set to such an intensity that plasma cannot be generated by itself. The ratio of the intensities of the laser pulse L1 (short pulse) and the laser pulse L2 (long pulse) is, for example, L1: L2 = 1: 10 to 15.

Further, the output of the laser pulse L2 is started before the laser pulse L1 is output, and the output of the laser pulse L2 is completed after the output of the laser pulse L1 is completed. By outputting the laser pulse L2 (long pulse) at such a timing, the measurement target can be heated in advance before the output of the laser pulse L1, and the effect of cleaning the surface of the measurement target (hereinafter referred to as "surface cleaning"). "Pretreatment effect") is obtained. This makes it easier to generate plasma. Further, after the plasma is generated, the effect that the plasma temperature can be lowered (hereinafter referred to as "surface heating effect") can be obtained.

FIG. 8 (A) is a diagram showing a temperature change of plasma (P1) generated when single pulse irradiation is performed, and FIG. 8 (B) is a diagram showing the temperature of plasma (P2) generated when double pulse irradiation is performed. It is a figure which showed the change. In the case of single pulse irradiation, as shown in FIG. 8A, the temperature (intensity) of the plasma emission P1 drops sharply with time after the laser pulse L1 is irradiated.

In the case of double pulse irradiation, as shown in FIG. 8B, the irradiation of the laser pulse L2 is started before the irradiation of the laser pulse L1 for plasma generation. As a result, the measurement target is heated in advance before the irradiation of the laser pulse L1 (pretreatment effect (heating effect)), the temperature rises, and the surface of the measurement target is cleaned (surface cleaning effect). After that, when plasma is generated by the laser pulse L1, the generated high-temperature plasma is maintained at a high temperature by the laser pulse L2 (heating effect). Therefore, as compared with the case shown in FIG. 8A, the intensity (temperature) of the light emitting P2 from the plasma becomes higher, and the rate of decrease thereof can be reduced. In this way, since the decrease in plasma emission intensity can be delayed, the timing of plasma measurement (that is, delay time D) can be set later than in the case of single pulse irradiation, and the accuracy does not depend on the fluctuation of plasma. Good measurement is possible.

3. 3. Measurement Results Below, an example of the measurement results of the emission spectrum of the plasma using the double pulse irradiation shown in the present embodiment is shown. FIG. 9 is a diagram illustrating a waveform of each pulse used for the measurement. A laser beam having a wavelength of 532 nm was used as the laser beam (laser pulse L1) for generating plasma. Further, as the laser beam (laser pulse L2) for maintaining the plasma temperature and the like, a laser beam having a wavelength of 1064 nm was used. Two targets were prepared as measurement targets. The first target is an iron plate (stainless steel plate) installed in the air, and the second target is an aluminum plate installed in the water.

(A) First Measurement Result As the first measurement, a plasma emission spectrum by double pulse irradiation was measured on an iron plate (stainless steel plate) installed in the air. The composition analysis of the target placed in the air can be applied to, for example, the measurement of the iron component in the blast furnace.

FIG. 10C is a diagram showing a spectrum observed by double pulse irradiation. 10 (A) and 10 (B) are measurement results by one pulse irradiation for comparison. Specifically, FIG. 10A shows the emission spectrum observed when single-pulse irradiation, that is, irradiation of only the laser beam L1 having a wavelength of 532 nm. In the measurement result shown in FIG. 10 (A), a signal indicating an iron (Fe) element can be observed, but its intensity is small. FIG. 10B shows an emission spectrum observed when only a laser beam having a wavelength of 1064 nm (that is, a laser beam L2 for maintaining the plasma temperature) is irradiated. In this case, no signal indicating the elemental component is observed. FIG. 10C shows an emission spectrum observed by double pulse irradiation (that is, irradiation of a laser beam L1 having a wavelength of 532 nm and a laser beam L2 having a wavelength of 1064 nm). As shown in FIG. 10 (C), a higher signal intensity (4.5 times) is obtained by double pulse irradiation as compared with the case of single pulse irradiation (see FIG. 10 (A)). I understand.

(B) Second measurement result As the second measurement, a plasma emission spectrum by double pulse irradiation was measured on an aluminum plate placed in water. The composition analysis of such a target placed in water can be applied to, for example, the measurement of the debris component in a meltdown reactor.

FIG. 11C is a diagram showing a spectrum observed by double pulse irradiation. 11 (A) and 11 (B) are measurement results by one pulse irradiation for comparison.

Specifically, FIG. 11A shows the emission spectrum observed when single-pulse irradiation, that is, irradiation with only the laser beam L1 having a wavelength of 532 nm. In the measurement result shown in FIG. 11 (A), the signal indicating the aluminum element (Al) could not be observed. This is because in water, the generated plasma disappears in a short time, which makes measurement more difficult. FIG. 11B shows an emission spectrum observed when only a laser beam having a wavelength of 1064 nm (that is, a laser beam L2 for maintaining the plasma temperature) is irradiated. In this case as well, no signal indicating the element of aluminum was observed. FIG. 11C shows an emission spectrum observed by double pulse irradiation (that is, irradiation of a laser beam L1 having a wavelength of 532 nm and a laser beam L2 having a wavelength of 1064 nm). Although it could not be observed by single pulse irradiation, a signal indicating aluminum element (Al) was observed by double pulse irradiation.

In this way, in addition to the laser beam L1 (short pulse) for generating plasma, another laser beam L2 (long pulse) is irradiated. As a result, the influence of the surface texture (temperature, uneven shape) is reduced by the surface cleaning effect and the pretreatment effect, and plasma is easily generated. Further, due to the heating effect, the temperature of the generated plasma can be maintained, and the rate of temperature decrease (intensity decrease) can be slowed down. As a result, signals indicating elements can be observed more clearly in the plasma emission spectrum.

(C) Third measurement result Furthermore, the present inventor performed a measurement for confirming the surface cleaning effect. For comparison, measurements were made using each of the three laser pulse irradiation methods shown in FIG. That is, when only the short pulse L1 is irradiated as shown in FIG. 12 (A) (hereinafter referred to as “single pulse irradiation”), as shown in FIG. 12 (B), the long pulse L2 is irradiated after the short pulse L1 is irradiated. When the irradiation of the short pulse L1 is started (hereinafter referred to as "double pulse irradiation (after)") and when the irradiation of the long pulse L2 is started before the irradiation of the short pulse L1 is started (hereinafter referred to as "double pulse irradiation (after)"). The plasma emission spectrum was measured with "double pulse irradiation (before)").

In order to verify the surface cleaning, measurements were made using a sample with a polished surface and a sample with a rusted surface. FIG. 13 shows the measurement results performed on the sample having a polished surface, and FIG. 14 shows the measurement results performed on the sample having a rusted surface. 13 (A) and 14 (A) are the measurement results of the spectrum in the case of single pulse irradiation. 13 (B) and 14 (B) are the measurement results of the spectrum in the case of double pulse irradiation (after). 13 (C) and 14 (C) are the measurement results of the spectrum in the case of double pulse irradiation (before).

With reference to FIGS. 13 (A) to 13 (C), for the sample whose surface was polished, a slightly better spectrum was obtained in the case of double pulse irradiation (before), but a remarkable difference was observed. Absent. It is considered that this was not affected by the cleaning effect because the surface of the sample was polished. On the other hand, for a sample with a rusted surface, as shown in FIGS. 14A and 14B, single-pulse irradiation and double-pulse irradiation (after) produce a noisy spectral waveform, and measurement results that can be used are obtained. I couldn't. However, as shown in FIG. 14C, in the case of double pulse irradiation (before), good measurement results are obtained due to the surface cleaning effect. It is considered that this is because the rust on the surface was removed by the surface cleaning effect.

FIG. 15A is an SEM image of the surface of the rusted measurement target after single-pulse irradiation with a scanning electron microscope (SEM). FIG. 15B is an SEM image of the surface of the rusted object after double pulse irradiation (before). In FIG. 15A, the laser pulse L1 having a short pulse width is irradiated twice. In the case of single pulse irradiation, a relatively large amount of rust 80 remains as shown in FIG. 15 (A). On the other hand, in the case of double pulse irradiation, as shown in FIG. 15 (B), it can be seen that a relatively large amount of rust is removed. From this, it can be seen that there is a cleaning effect on the target surface by double pulse irradiation (front).

(D) Fourth Measurement Result Further, the present inventor performed a measurement for confirming the pretreatment effect (heating effect). 16 and 17 are views showing the measurement results of solid steel (normal temperature) and molten steel (1600 ° C.) in order to confirm the pretreatment effect (heating effect). In this measurement as well, the spectrum was measured using each of the three types of laser pulse irradiation methods shown in FIG. In the following, attention will be paid to the measurement of the manganese (Mn) component contained in the steel. 16 (A) and 16 (B) show the measurement results when single pulse irradiation or double pulse irradiation (after) is performed on solid steel and molten steel, respectively. 17 (A) and 17 (B) show the measurement results when double pulse irradiation (before) is performed on solid steel and molten steel, respectively.

Referring to FIG. 16, in the case of single pulse irradiation or double pulse irradiation (after), the spectrum of manganese (Mn) cannot be confirmed from the measurement result for solid steel, but the measurement result for molten steel shows manganese (Mn). The spectrum of is confirmed. It is considered that this is because the temperature of molten steel is sufficient to measure the spectrum of manganese (Mn), but the temperature of solid steel is low and does not reach a temperature sufficient for measurement.

On the other hand, in the case of double pulse irradiation (before), as shown in FIG. 17, the spectrum of manganese (Mn) can be measured even for solid steel. It is considered that this is because the surface of the measurement target is heated to a sufficiently high temperature (heating effect) by irradiating the long pulse L2 before the short pulse L1 irradiation. As described above, by double pulse irradiation (before), good measurement results can be obtained regardless of whether the measurement target is a solid or a liquid. That is, it is possible to measure the spectrum of manganese without being affected by the properties of the surface to be measured.

As described above, by irradiating the long pulse L2 before irradiating the short pulse L1 for generating plasma (double pulse irradiation (before)), the temperature of the measurement target can be raised in advance (pretreatment effect). ). Further, when the target surface becomes flat due to the cleaning effect (that is, when the sudden shape change of the target surface disappears), the laser irradiation is performed more effectively, so that plasma can be generated efficiently. As a result, plasma can be generated regardless of the properties of the measurement target.

Further, by continuously irradiating the laser pulse L2 even after the irradiation of the laser pulse L1, the temperature of the plasma can be maintained and the decrease in the plasma temperature can be suppressed (heating effect).

4. Summary As described above, the component composition measurement system 100b of the present embodiment has a first laser light source 10 that irradiates the measurement target 200 with a laser beam L1 having an intensity sufficient to generate plasma, and a degree that does not generate plasma. From the second laser light source 10b that irradiates the measurement target 200 with the laser beam L2 having the intensity of the above, and the emission of plasma generated by the irradiation of the laser light from the first laser light source 10 to the measurement target 200, the intensity for each wavelength. The second laser light source 10b includes a spectrum measuring device (30) for measuring the emission spectrum showing the above, and a control device 50 for analyzing the composition of the measurement target using the measured emission spectrum data. The second laser light source 10b is the first. The measurement target 200 is irradiated with the laser light L2 for a period longer than the period during which the laser light L2 of the laser light source 10 is irradiated to the measurement target 200. In addition to the laser light L1 from the first laser light source, the second laser light source 200 is irradiated with the laser light L2. By irradiating the laser light L2 from the laser light source 10, it is possible to delay the decrease (attenuation) of the temperature (intensity) of the once generated plasma.

In particular, as shown in FIG. 7, the second laser light source 10b starts the irradiation of the laser beam L2 before the start of the irradiation of the laser beam L1, and ends the irradiation of the laser beam L2 after the irradiation of the laser beam L1 is completed. To do. As a result, the measurement target 200 is preheated to a high temperature before the irradiation of the laser beam L1. Further, if the surface to be measured has rust or the like, it is cleaned. As a result, plasma is likely to be generated, and measurement can be performed without being affected by the properties of the measurement target. Further, since the laser beam from the second laser light source 10b is irradiated when the plasma is generated by the irradiation of the laser beam L1 from the first laser light source 10, the plasma can be kept warm from the time when the plasma is generated, which is more effective. It is possible to reduce the decrease in plasma temperature. As a result, a spectrum including a high-level signal that does not depend on the strength of the plasma can be obtained, so that high measurement accuracy can be ensured.

Patent Document 1 and Non-Patent Document 1 also disclose LIBS devices that irradiate two types of laser pulses. However, in these documents, before the start of irradiation of one laser pulse having an intensity enough to generate plasma, the irradiation of the other laser pulse having an intensity not to generate plasma is started, and the irradiation of one laser pulse is started. The technical idea of ending the irradiation of the other laser pulse after the end of the irradiation is not disclosed. Therefore, the surface cleaning effect and the pretreatment effect shown in the present embodiment cannot be obtained from the techniques disclosed in Patent Document 1 and Non-Patent Document 1.

According to the component composition measurement systems 100 and 100b described in the above-described embodiment, the measurement accuracy in the laser-induced breakdown spectroscopy is improved, and the components in real time even when the position or shape of the measurement target changes during the process. Concentration measurement becomes possible. The concept of the component composition measurement system described in the above embodiment is a device for monitoring specific components contained in raw materials and products for quality control and control in a production process of a synthetic chemical plant, a steel plant, or the like. And system can be applied.

As described above, the first and second embodiments have been described as examples of the embodiments of the present invention. However, the idea of the present invention is not limited to these examples, and can be applied to embodiments in which changes, replacements, additions, omissions, etc. are made as appropriate. It is also possible to combine the components described in the above embodiment to form a new embodiment. That is, the above-described embodiment shows some specific examples of the technique in the present invention, and various changes, replacements, additions, omissions, etc. are made within the scope of claims or the equivalent thereof. Can be done.

(Other embodiments)
In the configuration of the component composition measurement system 100b of the second embodiment, the laser light from the second laser light source 10b may be transmitted by an optical fiber to the vicinity of the beam combiner 24. As a result, the second laser light source 10b can be arranged at an arbitrary position. Generally, the second laser light source 10b that outputs a long pulse laser beam is a large device, and there are restrictions on the installation position. Therefore, transmitting the laser light of the second laser light source 10b through an optical fiber is useful in that the degree of freedom in the layout of the second laser light source 10b is increased.

In the second embodiment, the functions of the first laser light source 10 that outputs a short pulse and the second laser light source 10b that outputs a long pulse may be realized by one light source device. FIG. 18 shows an example of the configuration of such a light source device. The laser light source 10c includes an excitation source 51, laser media 52 and 53, and mirrors 55 arranged at both ends of the laser media 52 and 53 on the optical path. Further, the laser light source 10c includes a pocket cell 57, a mirror 59, a wave plate 61, and a beam combiner 63.

The excitation source 51 is composed of, for example, a flash lamp, and outputs excitation light. The laser media 52 and 53 include Nd: YAG crystals that are excited by excitation light to generate laser light. The beam combiner 63 synthesizes a beam using the polarization characteristics of the laser beam. The pocket cell 57 is an element that oscillates a laser beam in a short pulse. The wave plate 61 is an element that changes the polarization characteristics of the laser beam.

The laser media 52 and 53 are excited by the excitation light from the excitation source 51 and output the light. The light generated by the laser media 52 and 53 is reflected between the mirrors 55 and output as laser light. The laser light from the laser medium 52 becomes a short pulse laser light via the pocket cell 57 and is output to the mirror 59. On the other hand, the laser medium 53 outputs a long pulse laser beam. The mirror 59 changes the optical path of the laser beam from the pocket cell 57 so that it is incident on the wave plate 61. The short pulse laser beam that has passed through the wave plate 61 is incident on the combiner 63. The combiner 63 synthesizes and outputs a short pulse laser beam from the laser medium 52 and a long pulse laser beam from the laser medium 553.

With the above configuration, it is possible to output two laser beams having different pulse widths from one laser light source 10c. By replacing the laser light source 10c having such a configuration with the laser light source 10 in the component composition measurement system 100 shown in FIG. 1, the same function as the component composition measurement system 100b shown in the second embodiment can be realized. ..

(Disclosure)
Needless to say, the ideas disclosed in each of the above-described first and second embodiments can be combined. That is, the present disclosure discloses the following component composition measurement system.

(1) A first laser light source that irradiates a measurement target with a first laser beam (L1) having an intensity sufficient to generate plasma, and
A second laser light source that irradiates the measurement target with a second laser beam (L2) having an intensity that does not generate plasma, and
A spectrum measuring device that measures an emission spectrum indicating the intensity of each wavelength from the emission of plasma generated by irradiating the measurement target with the laser beam from the first laser light source.
A control device for analyzing the composition of the measurement target using the measured emission spectrum data is provided.
The second laser light source is a component that starts the irradiation of the second laser beam before the start of the irradiation of the first laser beam and ends the irradiation of the second laser beam after the irradiation of the first laser beam is completed. Composition measurement system.

According to this component composition measurement system, the measurement target can be heated and the measurement target can be cleaned before the plasma is generated. Further, after the plasma is generated, the decrease in the temperature of the plasma can be delayed. As a result, a spectrum including a high level signal can be obtained, so that high measurement accuracy can be ensured.

(2) In the component composition measurement system of (1), the first and second lasers so that the first laser beam and the second laser beam irradiate the measurement target with their optical axes aligned. The optical axis of the light source may be adjusted. As a result, the portion to be measured heated by the second laser beam can be irradiated with the first laser beam. Further, the temperature of the plasma generated by the first laser beam can be kept warm by the second laser beam.

(3) In the component composition measurement system of (1), the control device may determine the properties of the emission spectrum and analyze the composition of the measurement target using only the data of the emission spectrum in which the properties are in a predetermined state. As a result, signals that may cause a decrease in accuracy can be excluded from the data used for analysis, and high measurement accuracy can be ensured.

(4) In the component composition measurement system of (3), the control device may determine the temperature of the plasma from the emission spectrum and analyze the composition of the measurement target using the emission spectrum in which the plasma temperature is equal to or higher than a predetermined temperature. .. As a result, signals that may cause a decrease in accuracy can be excluded from the data used for analysis.

(5) In the component composition measurement system of (3), even if the control device determines the signal intensity of the emission spectrum and analyzes the composition of the measurement target using the emission spectrum data in which the signal intensity is equal to or higher than a predetermined value. Good. As a result, signals that may cause a decrease in accuracy can be excluded from the data used for analysis.

(6) In the component composition measurement system of (3), the control device may measure the emission spectrum a plurality of times and analyze the composition of the measurement target using the result of integrating the data of the plurality of emission spectra. The accuracy of the measured data can be improved by integrating and using the data measured a plurality of times.

(7) The component composition measurement systems of (1) to (6) are a three-dimensional shape measuring device for measuring the three-dimensional shape and distance of the measurement target, and a laser beam emitted from the first laser light source to the measurement target. Further, a focus adjusting means for adjusting the focal length may be provided. The control device may adjust the focal length of the laser beam by controlling the focus adjusting means based on the measurement result by the three-dimensional shape measuring device. As a result, the measurement target can be irradiated with the laser beam always focused, regardless of the shape (distance) of the measurement target, and the laser beam can be irradiated with a constant intensity.

(8) The component composition measuring system of (1) to (6) may further include a three-dimensional shape measuring device and an irradiation position changing means for adjusting an irradiation position of the laser beam on the measurement target. The control device may control the irradiation position changing means based on the measurement result by the three-dimensional shape measuring device to adjust the irradiation position of the laser beam on the measurement target. As a result, the laser beam can be irradiated to a position (region) where a good plasma state can be obtained, and an emission spectrum in a constant state can be obtained regardless of the shape of the measurement target.

(9) Further, the present disclosure discloses the following component composition measuring method.
A step of irradiating the measurement target with a first laser beam having an intensity sufficient to generate plasma,
A step of irradiating the measurement target with a second laser beam having an intensity that does not generate plasma,
A step of measuring an emission spectrum showing the intensity of each wavelength from the emission of plasma generated by irradiating the measurement target with the first laser beam, and
Including the step of analyzing the composition of the object to be measured using the measured emission spectrum data.
The irradiation of the second laser beam is started before the start of the irradiation of the first laser beam, and the irradiation of the second laser beam is terminated after the irradiation of the first laser beam is completed.
Ingredient composition measurement method.

(10) In the component composition measurement method of (9), the properties of the emission spectrum may be determined in the analysis step, and the composition of the measurement target may be analyzed using only the data of the emission spectrum in which the properties are in a predetermined state. ..

Claims (10)

A first laser light source that irradiates the measurement target with a first laser beam having an intensity sufficient to generate plasma, and
A second laser light source that irradiates the measurement target with a second laser beam having an intensity that does not generate plasma, and a second laser light source.
A spectrum measuring device that measures an emission spectrum indicating the intensity of each wavelength from the emission of plasma generated by irradiation of the measurement target with the first laser light from the first laser light source.
A control device for analyzing the composition of the measurement target using the measured emission spectrum data is provided.
The second laser light source starts the irradiation of the second laser beam before the start of the irradiation of the first laser beam, and after the irradiation of the first laser beam is completed, the second laser beam of the second laser beam. End the irradiation,
Ingredient composition measurement system. The optical axes of the first and second laser light sources are adjusted so that the first laser beam and the second laser beam irradiate the measurement target with their optical axes aligned. , The component composition measuring system according to claim 1. The control device determines the properties of the emission spectrum and analyzes the composition of the measurement target using only the data of the emission spectrum in which the properties are in a predetermined state.
The component composition measurement system according to claim 1. The component composition measurement system according to claim 3, wherein the control device determines the temperature of plasma from the emission spectrum and analyzes the composition of the measurement target using an emission spectrum in which the plasma temperature is equal to or higher than a predetermined temperature. The component composition measurement system according to claim 3, wherein the control device determines the signal intensity of the emission spectrum and analyzes the composition of the measurement target using the data of the emission spectrum whose signal intensity is equal to or higher than a predetermined value. The component composition measurement system according to claim 3, wherein the control device measures the emission spectrum a plurality of times and analyzes the composition of the measurement target using the result of integrating the data of the plurality of emission spectra. A three-dimensional shape measuring device that measures the three-dimensional shape and distance of the measurement target,
Further provided with a focus adjusting means for adjusting the focal length of the laser beam emitted from the first laser light source to the measurement target.
The control device controls the focus adjusting means based on the measurement result by the three-dimensional shape measuring device to adjust the focal length of the laser beam.
The component composition measurement system according to any one of claims 1 to 6. A three-dimensional shape measuring device that measures the three-dimensional shape and distance of the measurement target,
Further, an irradiation position changing means for adjusting the irradiation position of the first laser beam on the measurement target is provided.
The control device controls the irradiation position changing means based on the measurement result by the three-dimensional shape measuring device to adjust the irradiation position of the laser beam on the measurement target.
The component composition measurement system according to any one of claims 1 to 6. A step of irradiating the measurement target with a first laser beam having an intensity sufficient to generate plasma,
A step of irradiating the measurement target with a second laser beam having an intensity that does not generate plasma, and
A step of measuring an emission spectrum showing the intensity of each wavelength from the emission of plasma generated by irradiating the measurement target with the first laser beam.
Including the step of analyzing the composition of the measurement target using the measured emission spectrum data.
Before the start of the irradiation of the first laser beam starts irradiation of the second laser beam, wherein the first after end of irradiation of the laser light, and ends the irradiation of the second laser beam,
Ingredient composition measurement method. In the step of analysis, the properties of the emission spectrum are determined, and the composition of the measurement target is analyzed using only the data of the emission spectrum in which the properties are in a predetermined state.
The component composition measuring method according to claim 9.

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