JP7363028B2 - Component measuring device and component measuring method - Google Patents

Description

The present disclosure relates to a sample component measuring device and component measuring method using laser light.

Laser induced breakdown spectroscopy (hereinafter referred to as LIBS) is known as a means of analyzing the composition of a substance. In LIBS, a sample to be measured is irradiated with pulsed laser light. The laser beam has sufficient energy to turn the material into plasma, and plasma of the sample is generated in the irradiated area. The plasma is heated and the ions (and sometimes neutral particles) within it are excited. During the deexcitation process, the excited ions emit light at a wavelength unique to the substance. That is, by measuring the wavelength and intensity of light emitted from plasma, the composition, concentration, etc. of a sample can be analyzed (see Patent Documents 1 and 2).

Japanese Patent Application Publication No. 2000-121558 Japanese Patent Application Publication No. 2004-226252

In LIBS, it is necessary to turn a sample into plasma in a short time. In other words, it is necessary to irradiate the laser beam irradiation area with a laser beam having an energy density necessary for plasma formation. Therefore, laser light is typically focused onto the sample.

However, if the sample is constantly moving or the shape of the sample is constantly changing, it becomes difficult to appropriately focus the laser beam on the sample. In other words, there are many cases where the sample is not appropriately positioned at the laser beam focusing position. On the other hand, in LIBS, a sample is repeatedly irradiated with laser light at a frequency of about 10 Hz. Therefore, when the sample moves or deforms, fluctuations in signal intensity per unit time tend to increase, and fluctuations in the number of effective signals that can be used for component identification etc. also increase. As a result, for example, the time it takes to obtain sufficient statistical accuracy for measurement results also varies widely, impairing the quantitative nature of measurement.

The present disclosure has been made in view of the above circumstances. That is, the present disclosure aims to improve statistical accuracy in a component measuring device and a component measuring method using LIBS.

A first aspect of the present disclosure is an apparatus for measuring the components of a sample of powder, granules, or lumps, which includes a light source that repeatedly generates laser light, and a sample that is continuously and irregularly temporally and spatially. an irradiation optical system for the laser beam having a plurality of optical axes that pass through each of a plurality of irradiation points in the measurement space, an observation optical system having one optical axis that looks at the measurement space; The gist of the present invention is to include an analyzer that measures the wavelength and intensity of light emitted from the sample by irradiation with laser light and guided by the observation optical system.

A second aspect of the present disclosure is a method for measuring components of a sample of powder, granules, or lumps, in which a plurality of components are measured in a measurement space through which the sample continuously passes temporally and spatially irregularly. an observation optical system that repeatedly irradiates each irradiation point with laser light from different directions, and that has one optical axis that is emitted from the sample in the measurement space by the irradiation of the laser light and that looks at the measurement space; The gist is to measure the wavelength and intensity of light incident on the object .

A third aspect of the present disclosure is a waste treatment plant that includes the component measuring device according to the first aspect.

According to the present disclosure, statistical accuracy can be improved in a component measuring device and a component measuring method using LIBS.

FIG. 1 is a configuration diagram of a component measuring device according to the present embodiment. It is an enlarged view of the measurement space and its surroundings according to the present embodiment, and is a diagram for explaining measurement by the component measuring device. It is a flowchart of the ingredient measurement method concerning this embodiment.

Embodiments of the present disclosure will be described below based on the accompanying drawings. Note that common parts in each figure are given the same reference numerals, and redundant explanation will be omitted.

FIG. 1 is a configuration diagram of a component measuring device 10 according to this embodiment. FIG. 2 is an enlarged view of the measurement space 30 and its surroundings according to the present embodiment, and is a diagram for explaining measurement by the component measuring device. The component measuring device 10 according to the present embodiment uses the above-mentioned LIBS to identify a component contained in the sample 31 as a measurement target (observation target) and measure the concentration (component amount) of the component. The sample 31 is, for example, a powder (granules, lumps) that passes (for example, falls) through the measurement space 30, and is continuously supplied to the measurement space 30 from the sample supply source 32 during a predetermined period.

The sample 31 passes through the measurement space 30 temporally and spatially irregularly. That is, the frequency per unit time at which the sample 31 passes through the measurement space 30 changes (that is, it is not constant), and the position at which the sample 31 passes within the measurement space 30 also changes (that is, it is not constant).

The component measuring device 10 is installed, for example, in a waste treatment plant (not shown). In this case, the sample source 32 is a waste treatment plant and the powder as sample 31 is fly ash. The component measuring device 10 measures, for example, trace amounts of heavy metal components contained in this fly ash and their concentrations.

As shown in FIG. 1, the component measuring device 10 includes a light source 11, an irradiation optical system 12, an observation optical system 13, and an analysis device 14.

The light source 11 repeatedly generates laser light 15 at a predetermined period. The light source 11 is, for example, a Nd:YAG laser that is a pulsed laser light source. The Nd:YAG laser of this embodiment outputs a pulsed laser beam of 532 nm, which is a double wave, with a pulse width of several tens of fahrenheit to several hundred ns and a frequency of about 10 Hz.

Note that the wavelength of the laser beam 31 is set depending on the composition of the measurement target. For example, the fundamental wave (1064 nm), 3rd harmonic (355 nm), or 4th harmonic (266 nm) of an Nd:YAG laser may be used. Furthermore, the light source 11 is not limited to the Nd:YAG laser, but may be any other light source that generates a laser beam with a wavelength and energy that promotes light emission specific to the object to be measured. The wavelength is, for example, 193 nm to 10.6 μm, and the energy (pulse energy) is, for example, 0.1 mJ or more.

The irradiation optical system 12 is constituted by well-known optical elements such as lenses, (flat or concave) mirrors, and optical fibers, and guides the laser beam 15 output from the light source 11 to the measurement space 30 through which the sample 31 passes. However, the number of laser beams 15 guided into the measurement space 30 is plural. That is, the irradiation optical system 12 branches the laser beam 15 and focuses the beam into the measurement space 30 from different directions. For example, the irradiation optical system 12 focuses the branched laser beam 15 on each of a plurality of irradiation points within the measurement space 30 . In other words, the irradiation optical system 12 has a plurality of optical axes passing through the measurement space 31 from different directions. For example, the irradiation optical system 12 has a plurality of optical axes passing through each of the plurality of irradiation points. Note that this light convergence occurs at the same time. "Simultaneous" here includes a time difference due to an optical path difference.

In measurements using LIBS, the time from irradiation of a sample with laser light to the occurrence of light emission (delay time) is also used to obtain information regarding a desired component (for example, presence or absence of the component, concentration, various reaction processes, etc.) measurement conditions (for example, shutter (gate) time settings). In this case, the smaller the difference in the irradiation timing of the plurality of laser beams, the better. For example, as shown in FIG. 1, the optical path lengths of the plurality of laser beams (first laser beam 15a and second laser beam 15b) are made equal to each other. The optical system may be installed as shown in FIG. Note that a well-known beam splitter, half mirror, demultiplexer, or the like is used to split the laser beam. Furthermore, well-known lenses, concave mirrors, and the like are used to condense the laser beam.

Hereinafter, for convenience of explanation, the number of laser beams output from the irradiation optical system 12 will be described as two. That is, the irradiation optical system 12 branches the laser beam 15 output from the light source 11 into the first laser beam 15a and the second laser beam 15b. Furthermore, the irradiation optical system 12 focuses the first laser beam 15a on the irradiation point 30a of the measurement space 30, and focuses the second laser beam 15b on the irradiation point 30b of the measurement space 30 (see FIG. 2). . That is, the irradiation point 30a is located on the optical axis 12a of the irradiation optical system 12, in other words, on the optical axis 12a of the final stage (most downstream) lens 17 that focuses the first laser beam 15a. Similarly, the irradiation point 30b is located on the optical axis 12b of the irradiation optical system 12, in other words, on the optical axis 12b of the final stage (most downstream) lens 18 that focuses the second laser beam 15b.

Note that the optical axis 12a and the optical axis 12b may be aligned on the same line or may intersect with each other. Further, the irradiation point 30a and the irradiation point 30b may be separated from each other or may coincide with each other. In either case, the first laser beam 15a and the second laser beam 15b enter the measurement space 30 from different directions.

Similar to the irradiation optical system 12, the observation optical system 13 is composed of well-known optical elements such as lenses, (flat or concave) mirrors, and optical fibers. The optical axis 13a of the observation optical system 13 passes through the measurement space 30. For example, the optical axis 13a of the observation optical system 13 passes through at least one of the irradiation point 30a and the irradiation point 30b. Note that in the measurement space 30, the optical axis 13a of the observation optical system 13 may coincide with either the optical axis 12a or the optical axis 12b of the irradiation optical system 12. They may be parallel and spaced apart.

The measurement space 30 is a space where the observation optical system 13 looks at the sample 31, and its size (width, depth, etc.) depends on the optical specifications (focal length, effective aperture, refractive index, material, etc.) of the observation optical system 13. Dependent. In other words, it is defined by optical specifications. Light 33 emitted from the sample 31 within the measurement space 30 and incident on the observation optical system 13 is appropriately guided to an analysis device 14, which will be described later. That is, the light enters the analyzer 14 at an angle within the maximum acceptance solid angle defined by the analyzer 14.

When the sample 31 is a powder that passes through the measurement space 30, the powder may not pass through the irradiation points 30a and 30b. However, the first laser beam 15a and the second laser beam 15b are sufficiently focused in the measurement space 30 by the irradiation optical system 12. Therefore, as shown in FIG. 2, plasma (luminescence) of the sample 31 is generated by irradiation with the first laser beam 15a or the second laser beam 15b even at locations other than the irradiation points 30a and 30b. The observation optical system 13 receives light 33 generated at a location other than the irradiation points 30 a and 30 b in the measurement space 30 and guides it to the analysis device 14 .

The analyzer 14 is a so-called spectrometer. The wavelength and intensity of light 33 emitted from the sample 31 by laser light 15 (first laser light 15a and second laser light 15b) and guided by observation optical system 13 are measured. The analyzer 14 of this embodiment is a polychromator or a multichannel spectrometer that measures light of wavelengths within a predetermined range at once. However, the analyzer 14 may be a monochromator.

The control unit 16 controls the light source 11 and the analyzer 14. The control unit 16 is, for example, a computer, and controls the generation and repetition period of the laser beam 15. Further, the control unit 16 analyzes the wavelength and intensity output from the analyzer 14, and specifies (detects) the composition of the sample 31.

A component measuring method according to this embodiment will be explained. FIG. 3 is a flowchart of the component measurement method according to this embodiment. As shown in this figure, in this embodiment, first, the sample supply source 32 causes the sample 31 to continuously pass through the measurement space 30 (step S1). Note that this passing may also be done by falling.

The sample 31 in step S1 passes through the measurement space 30 temporally and spatially irregularly. That is, the frequency per unit time at which the sample 31 passes through the measurement space 30 changes (that is, it is not constant), and the position at which the sample 31 passes within the measurement space 30 also changes (that is, it is not the same).

Next, the light source 11 and the irradiation optical system 12 repeatedly irradiate the measurement space 30 with laser light (first laser light 15a and second laser light 15b) from different directions (step S2). For example, each of the plurality of irradiation points 30a and 30b in the measurement space 30 is repeatedly irradiated with the laser beam 15 (the first laser beam 15a and the second laser beam 15b). Note that the steps S1 and S2 may be performed in any order, and may be performed simultaneously.

Next, the wavelength and intensity of the light 33 emitted from the sample 31 by the laser beam 15 (the first laser beam 15a and the second laser beam 15b) are measured by the analyzer 14 (step S3).

As shown in FIG. 2 , a sample 31 is supplied to the measurement space 30 from a sample supply source 32 . When the sample 31 is powder, the powder passes (falls) through the measurement space 30 randomly both spatially and temporally. On the other hand, the measurement space 30 is irradiated with the first laser beam 15a and the second laser beam 15b from different directions. That is, compared to the case where one laser beam is used, the space in which the sample 31 is turned into plasma by the laser beam is expanded. That is, in one irradiation, the area where the sample 31 is turned into plasma becomes larger.

The observation optical system 13 captures the light 33 emitted from the sample 31 by the laser beam 15 (the first laser beam 15a and the second laser beam 15b), that is, the light emission of the sample 31. Furthermore, the observation optical system 13 can simultaneously capture a plurality of light emissions from different positions. Therefore, in one irradiation, light from a wider area is incident on the analyzer 14.

As described above, in LIBS, irradiation with the laser beam 15 is repeated. Therefore, according to the present embodiment, the number of signals (effective signals) indicating a specific component in the sample 31 per unit time increases, so that the statistical accuracy of the measurement results can be improved.

Note that the present disclosure is not limited to the embodiments described above, but is indicated by the claims, and further includes all changes within the meaning and scope equivalent to the claims.

DESCRIPTION OF SYMBOLS 10...Component measurement device, 11...Light source, 12...Irradiation optical system, 12a, 12b...Optical axis, 13...Observation optical system, 13a...Optical axis, 14...Analysis device, 15...Laser light, 15a...First laser beam , 15b...Second laser beam, 16...Control unit, 17, 18...Lens, 30...Measurement space, 30a, 30b...Irradiation point, 31...Sample, 32...Sample supply source, 33...Light

Claims (3)

A component measuring device for powder, granule or lump samples, comprising:
A light source that repeatedly emits laser light,
an irradiation optical system for the laser beam having a plurality of optical axes passing from different directions through each of a plurality of irradiation points in a measurement space through which the sample continuously passes temporally and spatially irregularly;
an observation optical system having one optical axis that looks at the measurement space;
A component measuring device comprising: an analyzer that measures the wavelength and intensity of light emitted from the sample in the measurement space by the laser beam and guided by the observation optical system. A method for measuring the components of a powder, granule or lump sample, the method comprising:
Repeatedly irradiating laser light from different directions to each of a plurality of irradiation points in a measurement space through which the sample continuously passes temporally and spatially irregularly,
A component measurement method for measuring the wavelength and intensity of light emitted from the sample in the measurement space by the laser beam and incident on an observation optical system having one optical axis looking into the measurement space . A waste treatment plant equipped with the component measuring device according to claim 1.

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