WO2017199904A1

WO2017199904A1 - Component composition measuring system and component composition measuring method

Info

Publication number: WO2017199904A1
Application number: PCT/JP2017/018180
Authority: WO
Inventors: 出口　祥啓; シュウ・ファン－ジュン
Original assignee: 国立大学法人徳島大学
Priority date: 2016-05-17
Filing date: 2017-05-15
Publication date: 2017-11-23
Also published as: KR20190008231A; JPWO2017199904A1; CN109154567A; CN109154567B; KR102298835B1; JP6901145B2

Abstract

This component composition measuring system is provided with: a first laser light source which radiates first laser light (L1), having an intensity sufficient to generate plasma, onto an object to be measured; a second laser light source which radiates second laser light (L2), having an intensity not sufficient to generate plasma, onto the object to be measured; a spectrum measuring device which measures a light-emission spectrum indicating the intensity at each wavelength, from plasma emissions generated by radiating the first laser light onto the object to be measured; and a control device which uses data relating to the measured light-emission spectrum to analyze the composition of the object to be measured. The second laser light source starts radiating the second laser light (L2) before the start of radiation of the first laser light (L1), and stops radiating the second laser light (L2) after radiation of the first laser light (L1) has stopped.

Description

Component composition measuring system and component composition measuring method

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

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

More specifically, in laser-induced breakdown spectroscopy, a laser beam is focused and irradiated onto a measurement target, and the surface of the measurement target is rapidly heated to generate a plasma containing ions in an excited state on the measurement target surface. Generate. When the excited electrons fall to a low energy level, they emit light having a component-specific frequency. Since the emission intensity has a correlation with the atom number density, it is possible to identify and survey a substance existing in the measurement target by obtaining the wavelength and spectral line intensity of each spectrum. Here, emission spectrum intensity Ii of atom i by spontaneous emission is expressed by the following equation.

n _(i) is the concentration of element i, K _{(i), j} is a variable containing the Einstein coefficient, g _{(i), j} is the degree of degeneracy, E _{(i), j} is the upper energy, K _B is the Boltzmann constant, T Indicates the plasma temperature. When performing quantitative analysis, it is important to clarify factors that affect the emission intensity I _(i) , such as plasma temperature.

Laser induced breakdown spectroscopy is applied to 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 that detects harmful substances in waste wood, a transport device that transports waste wood, and a laser-induced breakdown that detects harmful substances in waste wood transported to the transport apparatus ( (LIBS) device and a sorting device for separating 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 simply and quickly in real time.

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 alone are combined. Non-Patent Document 1 discloses a LIBS device in which the optical axes of a short laser pulse and a long laser pulse are matched.

JP 2007-10371 US Patent 8,125,627

Laser-induced breakdown spectroscopy has the advantage of being able to measure the elemental composition of the measurement object in real time, but on the other hand, it can be applied when the position or shape of the object changes because the accuracy decreases when fluctuations occur in the plasma generation process. There is a problem that is difficult.

An object of the present invention is to provide an apparatus and a method for analyzing a composition to be measured using laser-induced breakdown spectroscopy, and an apparatus and a method capable of accurately analyzing the composition.

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 that generates plasma, and a second laser that has an intensity that does not generate plasma. A light emission spectrum indicating the intensity for each wavelength is measured from the second laser light source that irradiates light to the measurement target and the light emission of the plasma generated by the irradiation of the first laser light from the first laser light source to the measurement target. A spectrum measuring device; and a control device that analyzes a composition to be measured using data of the measured emission spectrum. The second laser light source starts irradiation of the second laser light before the start of irradiation of the first laser light, and ends irradiation of the second laser light after the end of irradiation of the first laser light.

The component composition measuring method according to the present invention includes 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 sufficient not to generate plasma. Irradiating the measurement target with the first laser light, measuring the emission spectrum indicating the intensity for each wavelength from the plasma emission generated by irradiating the measurement target of the first laser light, and using the measured emission spectrum data Analyzing the composition to be measured. The irradiation of the second laser light is started before the irradiation of the first laser light is started, and the irradiation of the second laser light is ended after the irradiation of the first laser light is completed.

According to the component composition measurement system and component composition measurement method of the present invention, the measurement object before plasma generation can be heated, the temperature (intensity) of the plasma once generated can be maintained, and the decrease (attenuation) 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 measuring system in Embodiment 1 of this invention. The figure explaining the change over time of emission intensity and emission spectrum observed in laser induced breakdown spectroscopy (LIBS) Diagram explaining the timing of laser pulse irradiation and plasma measurement in the component composition measurement system Flow chart showing operation of component composition measurement system Diagram explaining an example of a spectrum observed in laser-induced breakdown spectroscopy The figure which showed the structure of the component composition measuring system in Embodiment 2 of this invention. The figure explaining double pulse irradiation in Embodiment 2. (A) The figure which showed the intensity change of the plasma luminescence at the time of single pulse irradiation, (B) The figure which showed the intensity change of the plasma luminescence at the time of double pulse irradiation The figure explaining the waveform of each pulse used for the 1st and 2nd measurement The figure which shows the result of the 1st measurement (measuring object = iron plate (stainless steel plate) installed in the air) The figure which shows the result of the 2nd measurement (measurement object = aluminum plate installed in water) Diagram explaining the irradiation timing in various laser pulse irradiation methods The figure which showed the measurement result which was done to the sample where the surface was polished The figure which showed the measurement result done to the sample where the surface rusted (A) The figure which shows the SEM image of the measurement object surface after irradiating a measurement object with a single pulse, (B) The figure which shows the SEM image of the measurement object surface after irradiating a measurement object with a double pulse The figure which showed the measurement result when performing single pulse irradiation or double pulse irradiation (after) to solid steel and molten steel in order to confirm the pretreatment effect (heating effect) The figure which showed the measurement result at the time of performing double pulse irradiation (previous) to solid steel and molten steel in order to confirm the pretreatment effect (heating effect) The figure which shows the example of a structure of the light source device which can irradiate two types of laser beams

Hereinafter, an embodiment of a component composition measuring 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 a composition to be measured using laser-induced breakdown spectroscopy (LIBS).

(Embodiment 1)
1. System Configuration FIG. 1 shows the configuration of the first embodiment of the component composition measuring 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 condensing lens 22, and spectrum measurement. A device 30, a three-dimensional shape measurement device 40, and a control device 50 (analysis device) are provided.

The laser light source 10 is a light source device that has an intensity that does not generate plasma and is 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 light 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 light emitted from the laser light source 10, and is composed of a mirror, a prism, a 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 light, 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 measurement device 30 side.

The spectrum measuring device 30 is a device that measures an intensity distribution (emission spectrum) for each wavelength with respect to incident light. The spectrum measuring apparatus 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 by the spectroscope 32 based on a wavelength into an electric signal (image signal). Note that the spectrum measuring apparatus 30 is not limited to the configuration shown in FIG. 1, and may have any configuration as long as it can measure an emission spectrum.

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

The control device 50 (analysis device) acquires emission spectrum data from the spectrum measurement device 30, analyzes it, 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 of the three-dimensional shape measurement device 40, and changes the focus adjustment unit 16 and the irradiation position based on the determination result. The unit 20 is also controlled. The control device 50 is an information processing device (for example, a personal computer) including a CPU, and realizes a predetermined function by the CPU executing a predetermined program. Note that the analysis function of the emission spectrum 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, the function of the control device 50 may be realized only by hardware (electronic circuit) designed exclusively to realize a predetermined function, instead of being realized by a combination of hardware (CPU) and software. . That is, the control device 50 may include an MPU, DSP, FPGA, ASIC, or the like instead of the CPU.

2. The operation of the component composition measuring 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 adjustment unit 16. Further, the irradiation position of the laser beam on the measurement target 200 (that is, the optical path of the laser beam) is changed by the irradiation position changing unit 20. The three-dimensional shape measuring device 40 measures the shape (distance) of the measurement target 200 three-dimensionally and transmits it to the control device 50. The control device 50 controls the focus adjustment unit 16 and the irradiation position changing unit 20 based on the measurement result from the three-dimensional shape measurement device 40.

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

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

FIG. 2 is a diagram for explaining laser-induced breakdown spectroscopy. FIG. 2A is a diagram showing a change with time of plasma emission observed in laser-induced breakdown spectroscopy. As shown in FIG. 2A, when laser light (laser pulse) is irradiated onto the measurement target surface at time t0, plasma is generated on the measurement target surface. The emission intensity of plasma shows the maximum value immediately after laser pulse irradiation, and then decreases as the plasma cools with time. Atomic emission is measured during the plasma cooling process. The composition to be measured is measured based on the atomic emission measured at this time.

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

For this reason, in the component composition measurement system 100, as shown in FIG. 3, plasma emission, that is, atomic emission, is observed for an observation time (Tm) of a predetermined width after a predetermined delay time (D) has elapsed since the laser pulse irradiation. Measure. The delay time (D) is set to a time when noise is sufficiently reduced and atomic emission can be sufficiently observed (that is, a time when a sufficient S / N ratio is 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 atomic emission to be observed fluctuates greatly, making accurate measurement difficult. Become. Therefore, the component composition measurement system 100 of the present embodiment controls the laser pulse irradiation conditions so that the state of the generated plasma does not fluctuate, and further analyzes the measurement results measured in the fluctuating plasma state. Do not use. This improves the accuracy of composition analysis.

Hereinafter, the operation of the component composition measuring system 100 will be described using the flowchart of FIG.

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

Based on the measurement result (distance, shape) by the three-dimensional shape measurement device 40, the control device 50 has a shape change in which the measurement target 200 is at the in-focus position and the shape at the irradiation position of the laser pulse on the measurement target is sharply reduced. It is determined whether or not the region is a flat region (S12).

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

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

That is, when the measurement target 200 is not in the in-focus position, the control device 50 adjusts the position of the focus lens 14 by controlling the focus adjustment unit 16 so that the measurement target 200 is in the in-focus position. Thereby, even when the position of the measurement target 200 fluctuates, the laser light can be irradiated in a state where the measurement target 200 is always focused.

In addition, when the shape of the laser pulse irradiation position on the measurement target 200 is not flat (that is, when there is a sudden decrease in shape), 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 as to irradiate the area (that is, the area where there is no sudden change in shape) (S19). Thereafter, the process returns to step S11.

Here, the reason why the laser beam is controlled to irradiate a flat area as described above will be described. The temperature of the generated plasma differs between the case where the flat region is irradiated with laser light and the case where the region where there is a sudden shape change is irradiated with laser light. In a region where there is an abrupt change in shape, 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 irradiated per unit area is sin (X) times. sin (X) is 1 or less, and when X = 90 ° (laser beam perpendicular to the measurement surface is irradiated), sin (X) = 1, X = 45 ° (45 ° angle to the measurement surface) And sin (X) = 1 / √2 when the laser beam is irradiated. That is, as the angle X deviates from 90 °, the attenuation amount of the energy amount irradiated per unit area increases. Therefore, the temperature of the plasma generated by the laser beam irradiation on the region having an abrupt shape change (that is, the region having the unevenness) is lower than the temperature of the plasma generated by the laser beam irradiation on the flat region. As described above, the state (temperature) of the generated plasma differs depending on the shape of the irradiation region of the laser beam, and fluctuations in the state of the plasma affect 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 control is performed so that a flat region is irradiated with the laser light (S12, S19). .

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

Control device 50 calculates signal intensity and 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 the emission spectrum obtained from the 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 plurality of magnesium spectra (Mg1, Mg2) varies depending on the temperature. Therefore, it is possible to detect the temperature of the plasma by detecting a spectrum of a plurality of magnesium (Mg1, Mg2) intensity ratio _{_(I Mg1} / _I _Mg2). Note that 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.

Referring back to the flowchart of FIG. 4, the control device 50 determines whether or not the calculated signal intensity and plasma temperature are within predetermined ranges (S15). For example, the control device 50 determines whether or not the calculated signal intensity is a predetermined value or more, and determines whether or not the plasma temperature is a predetermined value or more. If at least one of the signal intensity 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. In addition, after changing the irradiation position of a laser beam, you may make it return to step S11.

On the other hand, when both the signal intensity and the plasma temperature are within the predetermined range (YES in S15), the control device 50 adds the signal intensity data measured at that time to the signal intensity 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 a measurement result indicating a good plasma state in which the plasma state satisfies certain conditions (signal intensity, temperature) is used. By using only the measurement result showing a good plasma state in this way, a decrease in measurement accuracy is prevented.

The control device 50 determines whether or not the number of times the spectrum signal intensity has been accumulated has reached a predetermined number of times (S17). If the predetermined number of integrations has not been reached (NO in S17), the control device 50 returns to step S11, repeats the above processing (S11 to S16), and acquires data for the predetermined number of integrations. In addition, after changing the irradiation position of a laser beam, you may make it return to step S11. Thus, by integrating and using a plurality of measurement data, the influence of noise is eliminated and the measurement accuracy is improved. When the predetermined number of integrations has been reached (YES in S17), the control device 50 calculates the concentration of each element constituting the measurement object 200 from the spectrum in which the signal intensity is integrated (S18). The calculated density information may be recorded on a recording medium (SSD, HDD) in the control device 50, may be displayed on a display, or may be printed by a printer. Alternatively, it may be transmitted to other devices (control device, server, etc.).

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

As described above, according to the component composition measurement system 100 of the present embodiment, when applying laser-induced breakdown spectroscopy, the characteristics of the emission spectrum may be judged and accuracy may be reduced based on the characteristics. Exclude signals from data used for analysis. Thereby, the fluctuation | variation of the state of the produced | 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 to be measured using the emission spectrum whose plasma temperature is equal to or higher than a predetermined temperature.

Furthermore, the component composition measuring system 100 may analyze the composition to be measured using the result of measuring the emission spectrum a plurality of times and integrating the data of the plurality of emission spectra. By accumulating and using data measured a plurality of times, the accuracy of the measurement data can be improved.

Furthermore, the component composition measurement system 100 includes a three-dimensional shape measurement device 40 that measures the three-dimensional shape of the measurement target 200 and a focus adjustment unit 16 that adjusts the focal length of the laser light emitted from the laser light source 10 to the measurement target. Further, it may be provided.

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

The component composition measurement system 100 may further include an irradiation position changing unit 20 that adjusts the irradiation position on the measurement target of the laser light. The control device 50 may adjust the irradiation position of the laser beam on the measurement target 200 by controlling the irradiation position changing unit 20 based on the measurement result by the three-dimensional shape measurement apparatus 40. Thereby, a laser beam can be irradiated to a position (region) where a good plasma state is obtained, and a constant emission spectrum can be obtained without depending on the shape of the measurement target, thereby improving the accuracy of measurement data.

(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. In contrast, 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 irradiated. By irradiating the second laser pulse in this manner, 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, irradiation of only a laser pulse for generating plasma as in the first embodiment is referred to as “single pulse irradiation”, and in order to generate plasma as in the present embodiment. In addition to the laser pulse irradiation, irradiation with another laser pulse to maintain the plasma temperature is referred to as “double pulse irradiation”.

1. System Configuration FIG. 6 is a diagram showing a configuration of a component composition measuring system in 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 that synthesizes the laser light from the first laser light source 10 and the laser light from the second laser light source 10 b and guides them to the beam splitter 12. The first and second laser light sources 10 are irradiated so that the laser light from the first laser light source 10 and the laser light from the second laser light source 10b are irradiated to the measurement object 200 in a state where their optical axes coincide. 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, a laser pulse (hereinafter also referred to as “long pulse”) L2 output from the second laser light source 10b is a laser pulse (hereinafter 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, whereas 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 an intensity that can generate plasma 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 intensity ratio between the laser pulse L1 (short pulse) and the laser pulse L2 (long pulse) is, for example, L1: L2 = 1: 10-15.

Further, the output of the laser pulse L2 is started before the laser pulse L1 is output, and the output 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 further, the effect of cleaning the measurement target surface (hereinafter referred to as “surface cleaning · A pre-treatment effect). Thereby, plasma can be easily generated. Furthermore, after plasma generation, an effect that a decrease in plasma temperature can be sent (hereinafter referred to as “surface heating effect”) is obtained.

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

In the case of double pulse irradiation, as shown in FIG. 8B, irradiation with the laser pulse L2 is started before irradiation with the laser pulse L1 for plasma generation. As a result, the measurement object is heated in advance (irradiation effect (heating effect)) before irradiation with the laser pulse L1, the temperature rises, and the measurement object surface is cleaned (surface cleaning effect). Thereafter, 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). For this reason, compared with the case shown to FIG. 8 (A), the intensity | strength (temperature) of light emission P2 from a plasma becomes higher, and the fall rate can be reduced. As described above, since the decrease in plasma emission intensity can be delayed, the timing of plasma measurement (that is, the 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. Measurement is possible.

3. Measurement result An example of the measurement result of the emission spectrum of plasma using the double pulse irradiation shown in this embodiment will be shown below. FIG. 9 is a diagram illustrating the waveform of each pulse used for measurement. Laser light having a wavelength of 532 nm was used as laser light (laser pulse L1) for generating plasma. Further, a laser beam having a wavelength of 1064 nm was used as the laser beam (laser pulse L2) for maintaining the plasma temperature. 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 water.

(A) 1st measurement result As a 1st measurement, the plasma emission spectrum by double pulse irradiation was measured with respect to the iron plate (stainless steel plate) installed in the air. Such composition analysis of a target installed in the air can be applied to, for example, measurement of iron components in a blast furnace.

FIG. 10C is a diagram showing a spectrum observed by double pulse irradiation. FIGS. 10A and 10B show measurement results obtained by one-time pulse irradiation for comparison. Specifically, FIG. 10A shows an emission spectrum observed when single pulse irradiation, that is, irradiation with only laser light L1 having a wavelength of 532 nm is performed. In the measurement result shown in FIG. 10A, a signal indicating an iron (Fe) element can be observed, but its intensity is small. FIG. 10B shows an emission spectrum observed when only laser light having a wavelength of 1064 nm (that is, laser light L2 for maintaining plasma temperature) is irradiated. In this case, a signal indicating an element component is not observed. FIG. 10C shows an emission spectrum observed by double pulse irradiation (that is, irradiation with laser light L1 having a wavelength of 532 nm and laser light L2 having a wavelength of 1064 nm). As shown in FIG. 10C, a higher signal intensity (4.5 times) is obtained by double pulse irradiation than in the case of single pulse irradiation (see FIG. 10A). I understand.

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

FIG. 11C shows a spectrum observed by double pulse irradiation. FIGS. 11A and 11B show measurement results obtained by one-time pulse irradiation for comparison.

Specifically, FIG. 11A shows an emission spectrum observed when single pulse irradiation, that is, irradiation with only laser light L1 having a wavelength of 532 nm is performed. In the measurement results shown in FIG. 11A, a signal indicating aluminum element (Al) was not observed. This is because the generated plasma disappears in a short time in water, making measurement more difficult. FIG. 11B shows an emission spectrum observed when only laser light having a wavelength of 1064 nm (that is, laser light L2 for maintaining plasma temperature) is irradiated. Also in this case, a signal indicating an aluminum element is not observed. FIG. 11C shows an emission spectrum observed by double pulse irradiation (that is, irradiation with laser light L1 having a wavelength of 532 nm and laser light L2 having a wavelength of 1064 nm). Although it could not be observed with single pulse irradiation, a signal indicating aluminum element (Al) was observed with double pulse irradiation.

Thus, in addition to the laser beam L1 (short pulse) for generating plasma, another laser beam L2 (long pulse) is irradiated. Thereby, the influence of surface properties (temperature, uneven shape) is reduced by the surface cleaning effect and the pretreatment effect, and plasma is easily generated. Furthermore, the temperature of the generated plasma can be maintained by the heating effect, and the rate of temperature decrease (strength decrease) can be reduced. As a result, a signal indicating an element in the plasma emission spectrum can be observed more clearly.

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

In order to verify surface cleaning, measurement was performed using a sample whose surface was polished and a sample whose surface was rusted. FIG. 13 shows the result of measurement performed on the sample whose surface was polished, and FIG. 14 shows the result of measurement performed on the sample whose surface was rusted. FIGS. 13A and 14A show spectrum measurement results in the case of single pulse irradiation. FIGS. 13B and 14B are spectrum measurement results in the case of double pulse irradiation (after). FIGS. 13C and 14C show spectrum measurement results in the case of double pulse irradiation (previous).

Referring to FIGS. 13A to 13C, for the sample whose surface was polished, a slightly good spectrum was obtained in the case of double pulse irradiation (before), but a significant difference was seen. Absent. This is considered to be because the sample surface was polished, and thus the cleaning effect was not affected. On the other hand, as shown in FIGS. 14 (A) and 14 (B), a single pulse irradiation and a double pulse irradiation (after) give a noisy spectrum waveform and a usable measurement result is obtained for a sample whose surface is rusted. I couldn't. However, as shown in FIG. 14C, in the case of double pulse irradiation (before), a good measurement result is obtained due to the surface cleaning effect. This is considered to be because the surface rust was removed by the surface cleaning effect.

FIG. 15 (A) is an SEM image obtained by photographing a state of the target surface after irradiating a measurement target with rust with a single pulse with a scanning electron microscope (SEM). FIG. 15B is an SEM image obtained by photographing the state of the target surface after the double pulse irradiation (front) is performed on the target with rust. 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. On the other hand, in the case of double pulse irradiation, it can be seen that a relatively large amount of rust is removed as shown in FIG. From this, it can be seen that there is a cleaning effect on the target surface by double pulse irradiation (before).

(D) Fourth Measurement Result Further, the present inventor performed measurement for confirming the pretreatment effect (heating effect). FIG. 16 and FIG. 17 are diagrams showing the results of measurements performed on solid steel (room temperature) and molten steel (1600 ° C.) in order to confirm the pretreatment effect (heating effect). Also in this measurement, the spectrum was measured using each of the three types of laser pulse irradiation methods shown in FIG. In the following, attention is paid to the measurement of the manganese (Mn) component contained in the steel. FIGS. 16A and 16B show measurement results when single pulse irradiation or double pulse irradiation (after) is performed on solid steel and molten steel, respectively. FIGS. 17A and 17B show the measurement results in the case of performing double pulse irradiation (previous) 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 results for solid steel, but in the measurement results for molten steel, manganese (Mn) The spectrum of can be confirmed. This is considered to be because in the case of molten steel, the temperature is sufficient to measure the manganese (Mn) spectrum, but the solid steel has a low temperature and does not reach a sufficient temperature 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. This is considered to be 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 the double pulse irradiation (before), a good measurement result can be obtained regardless of whether the measurement object is solid or liquid. In other words, the spectrum of manganese can be measured without being affected by the properties of the surface to be measured.

As described above, the temperature of the measurement target can be raised in advance by irradiating the long pulse L2 (double pulse irradiation (previous)) before the irradiation of the short pulse L1 for generating plasma (pretreatment effect). ). Furthermore, when the target surface is flattened by the cleaning effect (that is, when there is no sudden shape change of the target surface), 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.

Furthermore, by continuously irradiating the laser pulse L2 after the irradiation with the laser pulse L1, it is possible to maintain the plasma temperature and suppress a decrease in the plasma temperature (heating effect).

4). Summary As described above, the component composition measurement system 100b of the present embodiment has the first laser light source 10 that irradiates the measurement target 200 with the laser beam L1 having an intensity sufficient to generate plasma, and the extent that plasma is not generated. The intensity of each wavelength from the second laser light source 10b that irradiates the measurement target 200 with the laser light L2 having the intensity of, and the emission of the plasma generated by the irradiation of the laser light from the first laser light source 10 to the measurement target 200 And a control device 50 that analyzes the composition of the measurement target using data of the measured emission spectrum. The second laser light source 10b is a first laser light source 10b. The laser beam L2 is irradiated onto the measurement target 200 for a period longer than the period during which the laser beam L2 from the laser light source 10 is irradiated onto the measurement target 200. By irradiating the laser light L2 from the second laser light source 10 in addition to the laser light L1 from the first laser light source, the decrease (attenuation) of the temperature (intensity) of the plasma once generated can be delayed. it can.

In particular, as shown in FIG. 7, the second laser light source 10b starts irradiating the laser light L2 before starting the irradiation of the laser light L1, and ends the irradiation of the laser light L2 after the irradiation of the laser light L1 ends. To do. Thereby, the measuring object 200 is heated in advance and becomes high temperature before irradiation with the laser beam L1. Further, if there is rust on the surface to be measured, it is cleaned. As a result, plasma is easily generated, and measurement is possible without being affected by the properties of the measurement target. Further, since the laser light from the second laser light source 10b is irradiated when the plasma is generated by the irradiation of the laser light L1 from the first laser light source 10, the plasma can be kept warm from the time of the plasma generation, and thus more effective. In particular, a decrease in plasma temperature can be reduced. 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 apparatuses that irradiate two types of laser pulses. However, in these documents, before the start of irradiation of one laser pulse having an intensity sufficient to generate plasma, irradiation of the other laser pulse having an intensity not generating plasma is started, The technical idea of ending the irradiation of the other laser pulse after the irradiation is not disclosed. Therefore, from the techniques disclosed in Patent Document 1 and Non-Patent Document 1, it is not possible to obtain the surface cleaning effect and the pretreatment effect shown in the present embodiment.

According to the component

composition measurement systems

100 and 100b described in the above embodiments, the measurement accuracy in laser-induced breakdown spectroscopy is improved, and even in the case where the position or shape of the measurement target in the process changes, the real-time component Concentration measurement is possible. The idea of the component composition measurement system described in the above embodiment is an apparatus for monitoring specific components contained in raw materials and products for quality control and control in production processes such as synthetic chemical plants and steel plants. And can be applied to systems.

As described above, the first and second embodiments have been described as examples of the embodiment 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. Moreover, it is also possible to combine each component demonstrated in the said embodiment and it can also be set as a new embodiment. That is, the above-described embodiments show some specific examples of the technology in the present invention, and various modifications, replacements, additions, omissions, etc. are made within the scope of the claims or their equivalents. Can do.

(Other embodiments)
In the configuration of the component composition measuring system 100b according to the second embodiment, the laser light from the second laser light source 10b may be transmitted to the vicinity of the beam combiner 24 through an optical fiber. Thereby, the 2nd laser light source 10b can be arrange | positioned in arbitrary positions. Generally, the second laser light source 10b that outputs a long-pulse laser beam is a large-sized device, and the installation position is limited. Therefore, transmitting the laser beam of the second laser light source 10b with an optical fiber is useful in that the degree of freedom in layout of the second laser light source 10b is increased.

In Embodiment 2, 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 a single light source device. FIG. 18 shows an example of the configuration of such a light source device. The laser light source 10 c includes an excitation source 51,

laser media

52 and 53, and mirrors 55 disposed at both ends on the optical path of the

laser media

52 and 53. Further, the laser light source 10 c includes a Pockel cell 57, a mirror 59, a wave plate 61, and a beam combiner 63.

The excitation source 51 is composed of a flash lamp, for example, and outputs excitation light. The

laser media

52 and 53 include Nd: YAG crystals that are excited by excitation light and generate laser light. The beam combiner 63 combines the beams using the polarization characteristics of the laser light. The Pockel cell 57 is an element that causes laser light to oscillate in a short pulse. The wave plate 61 is an element that changes the polarization characteristics of the laser light.

The

laser media

52 and 53 are excited by excitation light from the excitation source 51 and output light. 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 is outputted as a short pulse laser light via the Pockel cell 57 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 light from the Pockel cell 57 so that it enters the wave plate 61. The short-pulse laser light that has passed through the wave plate 61 is incident on the combiner 63. The combiner 63 combines the short pulse laser light from the laser medium 52 and the long pulse laser light from the laser medium 553 and outputs the combined light.

With the configuration as described above, two laser beams having different pulse widths can be output 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 measuring system 100 shown in FIG. 1, functions equivalent to those of the component composition measuring system 100b shown in the second embodiment can be realized. .

(This disclosure)
Needless to say, the ideas disclosed in the first embodiment and the second embodiment can be combined. That is, this indication discloses the following component composition measuring systems.

(1) a first laser light source that irradiates a measurement target with a first laser beam (L1) having an intensity sufficient to generate plasma;
A second laser light source that irradiates the measurement target with a second laser beam (L2) having an intensity that does not generate plasma;
A spectrum measuring device for measuring an emission spectrum indicating an intensity for each wavelength from light emission of plasma generated by irradiation of laser light to the measurement object from a first laser light source;
A control device for analyzing the composition of the measurement object using data of the measured emission spectrum,
The second laser light source starts the irradiation of the second laser light before starting the irradiation of the first laser light, and finishes the irradiation of the second laser light after the end of the irradiation of the first laser light. 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 plasma temperature can be delayed. Thereby, since a spectrum including a high level signal is obtained, high measurement accuracy can be ensured.

(2) In the component composition measurement system according to (1), the first and second lasers are irradiated so that the first laser beam and the second laser beam are irradiated onto the measurement target in a state where their optical axes coincide with each other. The optical axis of the light source may be adjusted. Thereby, the first laser beam can be irradiated to the portion to be measured heated by the second laser beam. Furthermore, the temperature of the plasma generated by the first laser light can be kept warm by the second laser light.

(3) In the component composition measurement system of (1), the control device may determine the property of the emission spectrum and analyze the composition to be measured using only the data of the emission spectrum having the property in a predetermined state. As a result, a signal 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 to be measured using the emission spectrum whose plasma temperature is equal to or higher than a predetermined temperature. . As a result, a signal that may cause a decrease in accuracy can be excluded from data used for analysis.

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

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

(7) The component composition measurement system according to (1) to (6) includes a three-dimensional shape measurement device that measures a three-dimensional shape and distance of a measurement target, and a laser beam emitted from the first laser light source to the measurement target. You may further provide the focus adjustment means to adjust a focal distance. The control device may adjust the focal length of the laser light by controlling the focus adjusting means based on the measurement result by the three-dimensional shape measuring device. As a result, the laser beam can always be focused and irradiated to the measurement object without depending on the shape (distance) of the measurement object, and the laser beam can be irradiated with a constant intensity.

(8) The component composition measurement system according to (1) to (6) may further include a three-dimensional shape measurement device and irradiation position changing means for adjusting the irradiation position of the laser beam on the measurement target. The control device may adjust the irradiation position of the laser beam on the measurement target by controlling the irradiation position changing means based on the measurement result by the three-dimensional shape measurement apparatus. Thereby, a laser beam can be irradiated to a position (region) where a good plasma state is obtained, and a constant emission spectrum can be obtained without depending on the shape of the measurement target.

(9) Further, the present disclosure discloses the following component composition measuring method.
Irradiating a measurement target with a first laser beam having an intensity sufficient to generate plasma;
Irradiating a measurement target with a second laser beam having an intensity that does not generate plasma;
A step of measuring an emission spectrum indicating an intensity for each wavelength from light emission of plasma generated by irradiation of the measurement target of the first laser beam;
Analyzing the composition to be measured using the measured emission spectrum data, and
Before starting the irradiation of the first laser light, start the irradiation of the second laser light, and after finishing the irradiation of the first laser light, end the irradiation of the second laser light.
Component composition measurement method.

(10) In the component composition measurement method of (9), in the analyzing step, the property of the emission spectrum may be determined, and the composition to be measured may be analyzed using only the data of the emission spectrum having the property in a predetermined state. .

Claims

A first laser light source that irradiates a measurement target with a first laser beam having an intensity sufficient to generate plasma;
A second laser light source that irradiates the measurement target with a second laser beam having an intensity that does not generate plasma;
A spectrum measuring device for measuring an emission spectrum indicating an intensity for each wavelength from light emission of plasma generated by irradiation of the first laser light from the first laser light source to the measurement target;
A control device for analyzing the composition of the measurement object using data of the measured emission spectrum,
The second laser light source starts irradiation of the second laser light before the start of irradiation of the first laser light, and after the irradiation of the first laser light ends, End the irradiation,
Component composition measurement system.
The optical axes of the first and second laser light sources are adjusted so that the measurement target is irradiated with the first laser light and the second laser light in a state where their optical axes coincide with each other. The component composition measuring system according to claim 1.
The control device determines the property of the emission spectrum, and analyzes the composition of the measurement target using only the data of the emission spectrum in which the property is in a predetermined state.
The component composition measuring system according to claim 1.
4. The component composition measurement system according to claim 3, wherein the control device determines a plasma temperature from the emission spectrum, and analyzes the composition of the measurement target using an emission spectrum having a plasma temperature equal to or higher than a predetermined temperature.
4. 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 data of the emission spectrum in which the signal intensity is a predetermined value or more.
4. 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 a result obtained by integrating the data of the plurality of emission spectra.
A three-dimensional shape measuring apparatus for measuring a three-dimensional shape and distance of a measurement target;
A focus adjusting unit that adjusts a focal length of the laser light emitted from the first laser light source to the measurement target;
The control device adjusts a focal length of the laser beam by controlling a focus adjusting unit based on a measurement result by the three-dimensional shape measuring device;
The component composition measuring system according to any one of claims 1 to 6.
A three-dimensional shape measuring apparatus for measuring a three-dimensional shape and distance of a measurement target;
Irradiation position changing means for adjusting the irradiation position on the measurement target of the laser light, further comprising:
The control device controls the irradiation position changing unit based on a measurement result by the three-dimensional shape measurement apparatus, and adjusts the irradiation position of the laser light on the measurement target.
The component composition measuring system according to any one of claims 1 to 6.
Irradiating a measurement target with a first laser beam having an intensity sufficient to generate plasma;
Irradiating the measurement object with a second laser beam having an intensity that does not generate plasma;
Measuring an emission spectrum indicating an intensity for each wavelength from light emission of plasma generated by irradiating the measurement target with the first laser beam;
Analyzing the composition of the measurement object using data of the measured emission spectrum,
Starting the irradiation of the second laser before starting the irradiation of the first laser light, and ending the irradiation of the second laser light after the irradiation of the first laser light;
Component composition measurement method.
In the analyzing step, the property of the emission spectrum is determined, and the composition of the measurement target is analyzed using only the data of the emission spectrum in which the property is in a predetermined state.
The component composition measuring method according to claim 9.