JP6095901B2 - Substance identification device and substance identification method - Google Patents

Description

  The present invention relates to a substance specifying device and a substance specifying method for specifying an arbitrary substance.

  Laser-induced breakdown spectroscopy (LIBS) material identification apparatus irradiates a sample to be identified with a pulsed laser beam, which is converted into plasma by the laser beam and excited into a high energy state. The light emitted when an object returns to its original energy state is measured to identify what kind of material the sample is.

  For example, through laser-induced breakdown spectroscopy, a calibration curve between the emission intensity of carbon obtained from the wood surface and the air dry density of wood is prepared in advance, and the calibration curve is used to determine the carbon content regardless of the moisture content of the wood. A technique for nondestructively measuring the air-drying density of wood from the fluorescence intensity is disclosed (for example, Patent Document 1).

  However, the measurement result of laser-induced breakdown spectroscopy varies due to variations in laser oscillation intensity and temperature changes in the measurement field. In view of this, a technique has been disclosed in which light emission signals of the same component at different temperatures are measured in advance, and the material is identified by comparing the light emission signals with the actually measured light emission signals (for example, Patent Document 2). Also disclosed is a technique for obtaining an analysis result of laser-induced breakdown spectroscopy corresponding to multivariate environmental changes including temperature (for example, Patent Document 3).

JP 2009-288147 A JP 2001-349832 A JP 2012-47592 A

  However, the above-described techniques of Patent Documents 1 to 3 specify the other in a state where either one of the plasma temperature and the substance when the pulse laser is irradiated is specified, and both are unknown or fluctuate. It was not applicable when

  Here, if the temperature of the plasma can be specified, the substance can be specified based on the temperature. However, the temperature of the plasma depends on how the laser light is applied, the distance between the laser device and the sample, and the space between the laser device and the sample. Therefore, it is difficult to obtain objectively from the atmosphere in which the sample is placed.

  Therefore, in view of such problems, the present invention provides a substance specifying apparatus and a substance specifying method capable of appropriately specifying a substance by laser-induced breakdown spectroscopy regardless of the atmosphere in which the laser and the sample are placed. The purpose is to do.

In order to solve the above-mentioned problems, the substance identification device of the present invention is characterized in that an index spectrum obtained by laser-induced breakdown spectroscopy of a specific plasma decomposition product at a plurality of different plasma temperatures and a plasma conversion at a plurality of temperatures. the composition ratio of the peak ratio or two degradation products of the emission intensity of the two degradation products that, and a holding portion for holding the substance identification information associating the type of material, previously, any by laser-induced breakdown spectroscopy material spectrum deriving unit that derives the material spectrum into plasma, and the temperature specifying unit for specifying a temperature of the plasma optional materials by comparing the derived material spectrum and metrics spectrum, two in the substance spectrum The peak ratio or composition ratio of the emission intensity of the decomposition products is derived, the substance identification information is referenced, and the peak of the emission intensity of the two decomposition products is obtained. And a substance specifying unit for specifying any kind of substance based on the specified ratio or composition ratio and the specified plasma temperature.

The apparatus further includes a substance specifying information generating unit for generating substance specifying information by deriving a composition ratio of two decomposition products of the plasmaized substance based on a structural formula of the substance and an assumed plasma temperature by simulation. Good.

The index spectrum may be a C ₂ swan band spectrum.

  The spectrum deriving unit may derive the material spectrum after the thermal equilibrium of the plasma of an arbitrary material is established.

In order to solve the above-mentioned problems, the material identification method of the present invention is characterized in that an index spectrum obtained by laser-induced breakdown spectroscopy of a specific decomposition product that has been converted into plasma at a plurality of different temperatures of plasma and plasma conversion at a plurality of temperatures. the composition ratio of the peak ratio or two degradation products of the emission intensity of the two degradation products that, and may be held with substance identification information associating the type of material, previously, any by laser-induced breakdown spectroscopy The substance is converted into plasma and the substance spectrum is derived, the derived substance spectrum is compared with the index spectrum to determine the temperature of the plasma of any substance, and the peak ratio of the two decomposition products in the emission intensity of the substance spectrum or Deriving the composition ratio, referring to the substance identification information, the peak ratio or composition ratio of the emission intensity of the two decomposition products and the plasma identified Based on the temperature, the type of an arbitrary substance is specified.

  According to the present invention, a substance can be appropriately specified by laser-induced breakdown spectroscopy regardless of the atmosphere in which the laser and the sample are placed.

It is the block diagram which showed the schematic structure of the substance specific system. It is a functional block diagram describing a schematic configuration of a substance identification device. It is an explanatory diagram for explaining an index spectra in C ₂ Swan bands. It is explanatory drawing for demonstrating substance specific information. It is another explanatory drawing for demonstrating substance specific information. It is the flowchart which showed the flow of the process of the substance identification method. It is explanatory drawing which shows the spectrum in the case of calculating | requiring substance specific information by theoretical calculation. It is explanatory drawing which shows the substance spectrum which the spectrum derivation | leading-out part derived | led-out. It is explanatory drawing for demonstrating operation | movement of a temperature specific part.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

(Substance identification system 100)
FIG. 1 is a configuration diagram showing a schematic configuration of the substance identification system 100. The material identification system 100 includes a target holder 110, a laser device 112, a lens 114, a filter 116, a probe 118, an optical fiber 120, and a material identification device 122, and through laser-induced breakdown spectroscopy. Specify the substance (compound). The substance to be specified is, for example, an organic compound such as plastic, grain, biological agent, chemical agent, explosive, etc., and an element containing any of C, H, O, and N as an element is assumed. The shape and state of the substance are not particularly limited, and may be solid, bulk state (solid lump), powder, aerosol state, liquid, gas, or the like.

  A target holder 110 in the substance identification system 100 holds an arbitrary substance (hereinafter simply referred to as a sample) 102 to be identified in a fixed manner. The laser device 112 irradiates the sample 102 with, for example, pulse laser light from a femtosecond laser through the lens 114. Here, an example using a femtosecond laser will be described. However, the present invention is not limited to this, and a picosecond laser or a nanosecond laser may be used, and the wavelength of the laser light is not limited.

  However, it is desirable to avoid the wavelength close to the peak value of the spectrum of the sample 102 because the laser light itself becomes noise. Here, laser light having a wavelength of 780 nm, an output of 1 mJ, a pulse width of 120 fs, and a period of 1 kHz is used. The sample 102 receives a laser beam to be turned into plasma, and emits light having a wavelength specific to the substance. Here, it is desirable that the target holder 110 be provided with a rotation mechanism or the like so that the relative position between the target holder 110 and the laser device 112 can be changed so that the sample 102 is uniformly irradiated with the laser light.

  The filter 116 blocks laser light and background light with high emission intensity. The probe 118 receives light emitted from the sample 102. At this time, the light may be condensed using a lens or the like. The optical fiber 120 transmits the light received by the probe 118 to the substance specifying device 122.

  The substance specifying device 122 separates the radiated light of the sample 102 received through the optical fiber 120 for each of a plurality of wavelengths by a spectroscope 122a using, for example, an ICCD (Intensified Charge Coupled Device) as a detection unit. A spectrum is derived by obtaining a peak value, and it is specified which substance the sample 102 is. At this time, it is desirable that the substance specifying device 122 accepts the radiated light after a predetermined time (for example, 1 μsec in the case of a nanosecond laser) or more has passed after the laser light is irradiated from the laser device 112. The reason for waiting for the elapse of a predetermined time is that the plasma of the sample 102 is in a state of stably reaching thermal equilibrium. By doing so, the identification accuracy of the sample 102 can be increased. Hereinafter, the configuration of the substance identification device 122 will be described in detail.

(Substance identification device 122)
FIG. 2 is a functional block diagram illustrating a schematic configuration of the substance identification device 122. The substance identification device 122 includes a holding unit 130, an operation unit 132, a display unit 134, and a central control unit 136. The holding unit 130 includes a ROM, a non-volatile RAM, a flash memory, an HDD, and the like. The index spectrum obtained by laser-induced breakdown spectroscopy of a specific decomposition product converted into plasma at a plurality of different temperatures of plasma, and a plurality of temperatures. The substance specifying information in which the peak ratios of the emission intensities of the specific decomposed products converted into plasma and the substances are associated with each other is stored in advance. Below, an index spectrum and substance specific information are illustrated. Here, the decomposition product is a fragment released from a substance (compound).

(Indicator spectrum)
Figure 3 is an explanatory diagram for explaining an index spectra in C ₂ Swan bands. Here, for one or a plurality of decomposition products assumed to be included in the sample 102 to be specified, for example, the C ₂ swan band, a plurality of temperatures selected from the assumed plasma temperature range, for example, 3000K. With respect to 4000K, 5000K, and 6000K, a spectrum is derived through laser-induced breakdown spectroscopy, and the spectrum is held in the holding unit 130 as an index spectrum.

Referring to FIG. 3, in the same decomposition product (here, C ₂ swan band), the emitted light can be confirmed at a plurality of specific wavelengths regardless of the temperature. However, the emission intensity of the radiated light varies depending on the temperature so that it can be grasped by comparing FIGS. 3 (a) to 3 (d). Therefore, when the sample 102 contains C ₂ as a decomposition product (or when the sample 102 contains C as an element), by determining which temperature index spectrum the sample 102 approximates, The plasma temperature in the sample 102 can be estimated.

  Such an index spectrum has a peak ratio of emission intensity in a range where the temperature of the plasma is low, that is, in a range where the energy of the laser beam is small, as can be understood by comparing FIGS. 3 (a) to 3 (c). In the range where the rate of change is large and the temperature of the plasma is high, that is, the range where the energy of the laser beam is large, the change in the peak ratio of the emission intensity can be understood by comparing FIG. 3 (c) and FIG. You can see that the rate slows down. The number of such index spectra, that is, the resolution of the plasma temperature is four here, but the number is not limited, and the larger the better. However, it is desirable to match the resolution of the plasma temperature in the substance specifying information shown below.

(Substance specific information)
FIG. 4 is an explanatory diagram for explaining the substance specifying information. Here, for a plurality of temperatures selected from an assumed plasma temperature range, for example, 4000K, 5000K, 6000K, and 7000K, the emission intensity of a plurality of substances that can be specified, for example, nylon, polyethylene, polystyrene, and urethane. The C / H peak ratio, which is the ratio of the C peak to the H peak, is tabulated and held in the holding unit 130.

  Referring to FIG. 4, since the C / H peak ratios of the emission intensities of a plurality of substances are different even at the same plasma temperature, if the C / H peak ratio is specified, the specified C / H peak ratio is determined. The substance can be identified from However, since the emission intensity varies depending on the plasma temperature, the C / H peak ratio also varies. Therefore, in this embodiment, not only the C / H peak ratio is associated with each substance, but also the plasma temperature is associated. Therefore, in this embodiment, a substance is specified by two parameters, temperature and C / H peak ratio.

Thus, the reason why the C / H peak ratio varies depending on the plasma temperature even for the same substance is as follows. Decomposition products are not produced when the plasma is not formed (low energy state). These substances are converted into plasma by receiving laser light, and are excited and decomposed to a high energy state. However, not all substances are decomposed. If the temperature of the plasma changes according to the intensity of the laser beam and the time after irradiation, the ratio of the substance to be excited / decomposed changes, and the ratio (composition ratio) of the existing plasma components (decomposed products) changes. Become. When the composition ratios of the decomposed products are different as described above, the emission intensity at a predetermined wavelength also simply differs depending on the number of decomposed products, and the C / H peak ratio is also different as described above. Note that when the plasma temperature is high, substances such as H and C are decomposed into an atomic state, but when the plasma temperature is low, decomposition products such as CH and C ₂ are increased in molecular state.

  In this embodiment, in order to quickly identify the substance, the peak ratio of the emission intensity of the decomposition product that can be easily grasped from the spectrum of the sample 102 (substance spectrum) is used as the substance identification information. The composition ratio of the decomposition product may be used.

  FIG. 5 is another explanatory diagram for explaining the substance specifying information. FIG. 5 shows the composition ratio (C / H: ratio of C as a decomposed product to H as a decomposed product) in the form of a table instead of the peak ratio of the emission intensity in FIG. Has been. Therefore, when the composition ratio of the plasma-degraded decomposition product can be directly grasped, the substance can be specified by referring to such a table and using two parameters of temperature and composition ratio.

  Returning to FIG. 2, the operation unit 132 includes an operation key, a cross key, a joystick, a touch panel superimposed on the display surface of the display unit 134, a remote controller, and the like, and allows an operation input to the substance identification device 122 by the user. Accept. The display unit 134 includes a liquid crystal display, an organic EL (Electro Luminescence) display, and the like, and displays operation results input through the operation unit 132, intermediate results of specific processing (for example, derived substance spectrum), specified substances, and the like. indicate.

  The central control unit 136 is composed of a semiconductor integrated circuit including a central processing unit (CPU), a ROM in which programs are stored, a RAM as a work area, and the like, and manages and controls the entire substance specifying device 122. In addition, the central control unit 136 functions as an index spectrum generation unit 140, a substance identification information generation unit 142, a spectrum derivation unit 144, a temperature identification unit 146, and a substance identification unit 148.

  In preparation, the index spectrum generation unit 140 generates an index spectrum by laser-induced breakdown spectroscopy of a specific decomposition product that has been converted to plasma based on the temperature of the plasma. In advance preparation, the substance specifying information generating unit 142 generates substance specifying information in which a peak ratio or composition ratio of emission intensity with respect to a plurality of specific decomposed products formed into plasma is associated with the substance. The spectrum deriving unit 144 derives a substance spectrum by converting the sample 102 into plasma using laser-induced breakdown spectroscopy at the time of substance identification. The temperature specifying unit 146 compares the derived substance spectrum with the index spectrum when specifying the substance, and specifies the temperature of the plasma of the sample 102. The substance specifying unit 148 derives the peak ratio of the emission intensity of the decomposition product of the substance spectrum derived by the spectrum deriving unit 144 or the composition ratio of the decomposition product at the time of specifying the substance, and the substance specifying information held in the holding unit 130 is obtained. The substance is identified based on the derived peak ratio of the emission intensity of the decomposed product or the composition ratio of the decomposed product and the plasma temperature specified by the temperature specifying unit 146. The detailed operation of each functional unit will be specifically described below.

(Substance identification method)
FIG. 6 is a flowchart showing a process flow of the substance specifying method. Here, in advance preparation, an index spectrum and substance identification information are prepared, and at the time of substance identification, the plasma temperature, the peak ratio of emission intensity, and the substance are identified in order.

(Advance preparation)
As described with reference to FIG. 3, the index spectrum generation unit 140 is a C ₂ swan band at a plurality of temperatures selected from an assumed plasma temperature range, for example, 3000K, 4000K, 5000K, and 6000K. The index spectrum is generated (S1). As the index spectrum, a spectrum actually measured through laser-induced breakdown spectroscopy may be used, or a spectrum derived by theoretical calculation may be used. In the present embodiment, the C ₂ swan band index spectrum is used, but the index spectrum is not limited to the C ₂ swan band, and index spectra of various decomposition products serving as indexes can be used.

  As described with reference to FIG. 4, the substance specifying information generation unit 142 specifies a plurality of temperatures selected from the assumed plasma temperature range, for example, 3000K, 4000K, 5000K, and 6000K. A C / H peak ratio of emission intensity of a plurality of substances such as nylon, polyethylene, polystyrene, and urethane is derived, and is tabulated to generate substance specifying information (S2).

  As such substance specifying information, a spectrum actually measured through laser-induced breakdown spectroscopy may be used, or a spectrum derived by theoretical calculation may be used. For example, when the assumed substance is a substance that is difficult to measure in advance, such as a dangerous substance, a spectrum derived by theoretical calculation is used.

  When obtaining the substance identification information by theoretical calculation, the substance identification information generation unit 142 accepts the structural formula of the substance and the assumed temperature as input values, and based on the structural formula of the substance and the temperature, the substance is converted into plasma and is in thermal equilibrium. The composition ratio of the decomposition product when reaching the value is derived by simulation. Then, the spectrum as shown in FIG. 7 is derived by adding the emission intensity of each decomposition product to the derived composition ratio of the decomposition product. FIGS. 7A to 7D show spectra of nylon, polyethylene, polystyrene, and urethane, respectively, when the plasma temperature is 4000K. Since such a spectrum can be derived using various existing techniques, detailed procedures thereof are omitted.

  The substance specifying information generation unit 142 then analyzes the spectrum and derives the C / H peak ratio. Such C / H peak ratio is derived for all of a plurality of temperatures selected from the assumed material and the assumed temperature range of the plasma, and the material specifying information is generated.

  By generating substance identification information by theoretical calculation in this way, it is possible to generate substance identification information even if the assumed substance is a substance that is difficult to measure in advance, such as a dangerous substance. In the subsequent substance identification, such a substance can be identified with high accuracy.

(Substance identification)
The spectrum deriving unit 144 instructs the laser device 112 to irradiate the laser beam at the time of specifying the substance, and irradiates the sample 102 held by the target holder 110 with the laser beam. Then, the spectrum deriving unit 144 derives the substance spectrum by receiving the radiated light under a condition in which the thermal equilibrium of the plasma is established, that is, a predetermined time after the laser beam is irradiated from the laser device 112, in order to increase the accuracy of specifying the sample 102. (S3). For example, it is assumed that a material spectrum as shown in FIG. 8 is derived. At this point, neither the plasma temperature nor the material is known.

The temperature identification unit 146 identifies the plasma temperature of an arbitrary substance by comparing the derived substance spectrum and the index spectrum at the time of substance identification (S4). As described above, in the same decomposed product (here, C ₂ swan band), it is possible to confirm radiated light having different emission intensities depending on temperature at a plurality of specific wavelengths. Therefore, the temperature of the plasma in the sample 102 can be estimated depending on how the emission intensity is distributed in the substance spectrum.

FIG. 9 is an explanatory diagram for explaining the operation of the temperature specifying unit 146. Here, the substance spectrum shown in FIG. 8 (shown by a solid line in FIG. 9) derived from the spectrum deriving unit 144 and each index spectrum of 3000K, 4000K, and 5000K C ₂ swan bands (FIGS. 9A to 9C). ) And the degree of correlation are determined. For this determination, for example, the difference between the substance spectrum and the index spectrum is derived through the least square method or the like, and the temperature of the index spectrum that minimizes the difference is set as the temperature of the substance spectrum.

  In FIG. 9, since the index spectrum of 4000K and the substance spectrum shown in FIG. 9B are highly correlated with respect to the ratio of the emission intensity, the temperature specifying unit 146 specifies the temperature of the plasma of the substance spectrum as 4000K.

  In general, the temperature of plasma is affected by various parameters such as how to apply laser light, the distance between the laser device 112 and the sample 102, and the transmittance in the space between the laser device 112 and the sample 102. It is difficult to obtain objectively from the atmosphere. However, in this embodiment, since the temperature of the plasma can be specified through the spectrum, it is not affected by various parameters regardless of the test atmosphere. Therefore, the distance between the laser and the sample 102 can also be set freely. For example, it is possible to perform remote measurement by irradiating laser light from a distance.

  Further, as described with reference to FIG. 3, in the range where the energy of the laser beam is small, the change rate of the emission intensity is large so that it can be understood by comparing FIGS. 3 (a) to 3 (c). In the range where the temperature is high, that is, the range where the energy of the laser beam is large, the rate of change slows down so that it can be understood by comparing FIG. 3C and FIG. Therefore, in consideration of the influence of the test conditions on the substance spectrum, a range in which the laser beam energy with a small rate of change in emission intensity is small should be used. Therefore, the energy of the laser beam can be reduced, the power consumption of the laser beam can be reduced, and the sample 102 can be irradiated with the laser beam from a longer distance.

  The substance specifying unit 148 derives a peak ratio or a composition ratio of emission intensity for a plurality of specific decomposition products in the substance spectrum at the time of specifying the substance, and based on the substance specifying information at the plasma temperature specified by the temperature specifying unit 146. A substance is specified (S5).

  For example, the substance specifying unit 148 determines the ratio between the peak value of C and the peak value of H in FIG. Here, for example, it is assumed that a result of C / H = 99030330/784893 = 12.66 is obtained. Subsequently, the substance specifying unit 148 refers to the substance specifying information in FIG. 4 and determines whether or not there is a substance having a C / H peak ratio close to 12.66 in the 4000 K column specified by the temperature specifying unit 146. To do. Here, since the C / H peak ratio of “nylon” is 12.66, the substance specifying unit 148 specifies the substance showing the substance spectrum as shown in FIG. 8 as nylon. In this way, the substance specifying device 122 can specify one substance.

  As described above, according to the present embodiment, the laser-induced breakdown is achieved even when both the plasma temperature and the substance are unknown, regardless of variations in parameters such as the distance between the laser device 112 and the sample 102. It becomes possible to specify a substance appropriately by spectroscopy.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  For example, in the above-described embodiment, the substance is specified based on the peak ratio of the emission intensity, but when the composition ratio of the plasma decomposition product can be directly grasped, the composition ratio of the plasma decomposition product is tabulated. Using the specified substance specifying information, the substance can be specified based on the composition ratio of the decomposition product.

  In this embodiment, the substance is specified based on the temperature of the plasma on the assumption that the atmospheric pressure is 1 atm. However, if the atmospheric pressure is not 1 atm, the substance is specified by adding a parameter of atmospheric pressure to the temperature. It is also possible to generate information and identify substances based on temperature and pressure.

  The present invention can be used for a substance specifying device and a substance specifying method for specifying an arbitrary substance.

DESCRIPTION OF SYMBOLS 100 ... Substance identification system 122 ... Substance identification apparatus 130 ... Holding | maintenance part 140 ... Index spectrum generation part 142 ... Substance identification information generation part 144 ... Spectrum derivation | leading-out part 146 ... Temperature identification part 148 ... Substance identification part

Claims (5)

An index spectrum obtained by laser-induced breakdown spectroscopy of a specific decomposition product converted into plasma at a plurality of different temperatures of the plasma, and a peak ratio of the emission intensity of the two decomposition products converted into plasma at the plurality of temperatures or the 2 A holding unit that holds in advance the composition ratio of the two decomposition products and the substance specifying information in which the types of substances are associated;
A spectrum deriving unit for deriving a substance spectrum by converting any substance into plasma by laser-induced breakdown spectroscopy;
A temperature specifying unit that compares the derived substance spectrum with the index spectrum to specify the temperature of the plasma of the arbitrary substance;
Deriving a peak ratio or composition ratio of the emission intensity of the two degradation products in the substances spectrum, the reference to substance identification information, is the specific peak ratio or composition ratio of the emission intensity of the two degradation products A substance specifying unit for specifying the type of the arbitrary substance based on the temperature of the plasma;
A substance identification device comprising: A substance specifying information generating unit for generating the substance specifying information by deriving the composition ratio of the two decomposition products of the plasmaized substance by simulation based on the structural formula of the substance and the assumed plasma temperature. The substance specifying device according to claim 1. The substance specifying device according to claim 1, wherein the index spectrum is a C ₂ swan band spectrum.   4. The substance specifying device according to claim 1, wherein the spectrum deriving unit derives a substance spectrum after thermal equilibrium of the plasma of the arbitrary substance is established. 5. An index spectrum obtained by laser-induced breakdown spectroscopy of a specific decomposition product converted into plasma at a plurality of different temperatures of the plasma, and a peak ratio of the emission intensity of the two decomposition products converted into plasma at the plurality of temperatures or the 2 The composition ratio of the two decomposition products , and the substance identification information that associates the types of substances, are held in advance,
The material spectrum is derived by converting any material into plasma by laser-induced breakdown spectroscopy,
Compare the derived material spectrum with the index spectrum to identify the temperature of the plasma of the arbitrary material,
The peak ratio or composition ratio of the two decomposition products in the emission intensity of the substance spectrum is derived, and the peak ratio or composition ratio of the emission intensity of the two decomposition products is determined with reference to the substance specifying information. A method for specifying a substance , wherein the type of the arbitrary substance is specified based on a plasma temperature.

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