Coal isotope online detection system and method based on multi-wavelength coupling resonance enhancement

Abstract

The invention relates to a coal isotope on-line detection system and method based on multi-wavelength coupling resonance enhancement, and the system comprises a laser generation unit which is configured to generate a preprocessing light beam and an excitation light beam, and a light beam guiding unit, the guiding assembly is configured to guide the pretreatment light beam and the excitation light beam to the surface of a coal mine sample in a fixed spatial relative position relation, and the scanning assembly is configured to drive the pretreatment light beam and the excitation light beam to synchronously scan the surface of the sample, so that the sample can be scanned at any scanning position. The preprocessing light beam always acts on the same sample point before the excitation light beam, and the preprocessing light beam is configured to preprocess the sample point so as to reduce the matrix effect of subsequent spectrum detection; the excitation light beam comprises a resonance laser component, the wavelength of the resonance laser component is matched with the characteristic wavelength of the element to be measured, and the excitation light beam is configured to generate plasma on the pretreated sample point and perform resonance excitation so as to obtain enhanced radiation light.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser spectrum detection, in particular to a coal isotope online detection system and method based on multi-wavelength coupling resonance enhancement. BACKGROUND

[0002] Coal occupies an important position in the global energy structure, however, due to the possibility of uranium isotopes (such as U238 and U235) in coal, these isotopes will release radioactive substances during the mining process, endangering the environment and human health, therefore, online detection of uranium isotopes in coal is crucial, in addition, while monitoring environmental safety, recycling uranium resources can also be used for nuclear power generation, promoting the rational utilization of coal resources.

[0003] In the prior art, the patent application file with the application number CN202510041697.5 relates to a LIBS detection device and method for nitrogen, hydrogen and oxygen elements in stainless steel, which comprises: a LIBS element detection unit and a calculation control unit; the LIBS element detection unit generates a pulsed laser, and guides the laser beam to the surface of the stainless steel coal sample through a beam splitter and a galvanometer, excites to generate plasma, and collects the plasma spectrum through a six-channel optical fiber spectrometer; the calculation control unit controls the timing of laser emission and spectrum acquisition, and analyzes the spectrum data in real time to detect the concentration distribution of nitrogen, hydrogen and oxygen elements in the coal sample.

[0004] When the above and existing LIBS detection systems are used to detect elements in coal, the formed spectrum signal is weak and the spectral lines are complex and overlapping, thereby interfering with the detection work, and the detection efficiency and effect are not ideal. SUMMARY

[0005] The present application provides a coal isotope online detection system and method based on multi-wavelength coupling resonance enhancement, which can solve the problem of unsatisfactory detection efficiency and effect of the existing LIBS detection system when detecting elements in coal.

[0006] The technical solution of the present application is as follows: a coal isotope online detection system based on multi-wavelength coupling resonance enhancement, comprising: a laser generation unit configured to generate a pretreatment beam and an excitation beam; a beam guiding unit configured to guide the pretreatment beam and the excitation beam to a coal sample surface with a fixed spatial relative position relationship; a scanning assembly configured to drive the pretreatment beam and the excitation beam to perform synchronous scanning on the sample surface, so that at any scanning position, the pretreatment beam always acts on the same sample point before the excitation beam; The pre-treatment light beam is configured to pre-treat the sample point to reduce the matrix effect of subsequent spectral detection; the excitation light beam comprises a resonant laser component whose wavelength matches the characteristic wavelength of the element to be detected, and the excitation light beam is configured to generate plasma on the pre-treated sample point and perform resonant excitation to obtain enhanced radiation.

[0007] By using the above scheme, by using the laser generating unit to generate the pre-treatment light beam and the excitation light beam, the device is used for scanning the coal sample, and the scanning assembly is used for scanning the excitation light beam along the moving path of the pre-treatment light beam. The energy of the pre-treatment light beam causes the low-boiling-point components on the surface of the coal sample to sublimate. Since the pre-treatment light beam and the high-frequency laser have a certain distance between the action points on the coal sample, it is ensured that the smoke formed by sublimation does not affect the resonant excitation of the excitation light beam to the plasma, avoiding the influence of the smoke generated by the single laser on the surface of the coal sample on the excitation of the plasma, reducing the interference, and increasing the data reliability. At the same time, when the excitation light beam excites the plasma on the surface of the coal sample, part of the low-boiling-point components sublimate, thereby reducing the spectral signal generated by other element components when the excitation light beam resonantly excites the plasma and emits radiation, and further reducing the complexity of the spectrum line. In addition, since the excitation light beam moves along the path of the pre-treatment light beam, the afterglow generated by the pre-treatment light beam on the surface of the coal sample can also reduce the smoke generated when the excitation light beam generates the plasma. Furthermore, the resonant laser is set to be consistent with the characteristic wavelength of the element to be detected. When the resonant laser irradiates on the plasma, the energy required for the element to be detected to occur in the plasma is met, thereby increasing the probability of transition, and further increasing the light intensity of the radiation emitted by the element to be detected, so that the element to be detected is more easily detected.

[0008] In one embodiment of the present application, the laser generating unit comprises a first laser, a second laser and a control module, the first laser and the second laser are electrically connected with the control module, the first laser is configured to emit high-frequency narrow-line-width laser, the second laser is configured to emit resonant laser, and the control module is configured to control the frequency of the first laser and the second laser to set the delay time between the picosecond-level pulses of the high-frequency narrow-line-width laser and the resonant laser.

[0009] By adopting the scheme, the second laser can not only adjust the wavelength of the emitted laser to be consistent with the characteristic wavelength of the element to be detected to improve the transition probability of the element to be detected, but also can control the frequencies of the first laser and the second laser, so that the high-frequency narrow-linewidth laser and the resonance laser emitted by the two lasers can have a picosecond-level inter-pulse delay, so that when the high-frequency narrow-linewidth laser generates plasma on the surface of the coal sample and no radiation light is generated, the resonance laser can irradiate the plasma to increase the transition probability of the element to be detected in the plasma, and then when the plasma emits radiation light, the radiation light signal of the element to be detected in the plasma is enhanced.

[0010] In one of the embodiments of the present application, the laser generating unit further comprises a beam splitting device and a beam combining device located on the light path thereof, and the beam splitting device comprises a beam splitter and a laser reflecting mirror. The beam splitter is arranged along the propagation direction of the high-frequency narrow-linewidth laser, and is used to split the high-frequency narrow-linewidth laser and form a pretreatment beam and a high-frequency laser, so that the pretreatment beam is incident into the scanning assembly. The laser reflecting mirror is arranged along the propagation direction of the high-frequency laser, and is used to deflect the high-frequency laser so that the high-frequency laser is parallel to the pretreatment beam and is incident into the beam combining device.

[0011] By adopting the scheme, the transmission and reflection ratios of the beam splitter are limited, so that the laser is split after passing through the beam splitter and forms the pretreatment beam and the high-frequency laser with different energies, so that the pretreatment beam is parallel to the high-frequency laser after being reflected twice and is incident into the scanning assembly, and then the low-boiling-point components on the surface of the coal sample are pre-sublimated and pre-heated, thereby reducing the adverse effects on the detection of the spectrum signal.

[0012] In one of the embodiments of the present application, the beam combining device comprises a reflecting mirror and a first dichroic mirror. The reflecting mirror is arranged along the propagation direction of the resonance laser, and is used to reflect the resonance laser to the first dichroic mirror. The first dichroic mirror is arranged along the propagation direction of the high-frequency laser, and is used to transmit the high-frequency laser and reflect the resonance laser emitted by the second laser, so that the high-frequency laser and the resonance laser are combined to form the excitation beam.

[0013] By adopting the scheme, the reflecting mirror and the first dichroic mirror are arranged, so that the resonance laser is reflected by the reflecting mirror to the first dichroic mirror after being emitted, the first dichroic mirror can reflect the resonance laser twice and transmit the high-frequency laser, so that the high-frequency laser can be combined with the resonance laser, and then the two kinds of lasers are overlapped on the light path.

[0014] In one embodiment of the present application, the scanning assembly comprises a galvanometer cavity, at least two guide mirrors and a driving device. The at least two guide mirrors are arranged inside the galvanometer cavity and are arranged in sequence along the propagation direction of the excitation light beam and the pretreatment light beam, and the guide mirrors are coated with ultraviolet-enhanced aluminum film. The driving device is arranged on the galvanometer cavity and connected to the guide mirrors to deflect the pretreatment light beam and the excitation light beam so that the pretreatment light beam and the excitation light beam are emitted in a direction perpendicular to the incident direction of the excitation light beam.

[0015] By adopting the above scheme, by arranging at least two mirrors inside the galvanometer cavity, the pretreatment light beam and the excitation light beam can be emitted in a direction perpendicular to the incident path after being reflected by the two mirrors, and the driving device is used to adjust the angle of the mirrors, so that the pretreatment light beam can move on the surface of the coal sample when emitted to perform dot array scanning.

[0016] In one embodiment of the present application, the scanning assembly further comprises a focusing lens, the focusing lens is arranged vertically to the excitation light beam, and the focusing lens is configured to focus the pretreatment light beam and the excitation light beam so that the focal points of the pretreatment light beam and the excitation light beam are located on the surface of the coal sample.

[0017] By adopting the above scheme, by arranging the focusing lens, the pretreatment light beam and the excitation light beam are focused and emitted from the galvanometer cavity, and pass through the focusing lens to ensure that the focusing of the pretreatment light beam and the excitation light beam can be focused on the surface of the coal sample, and the coal sample surface is preheated at the same time, and plasma is ablated and resonantly excited.

[0018] In one embodiment of the present application, the beam guiding unit is a second dichroic mirror, and the beam guiding unit is arranged on the optical path between the beam combining device and the scanning assembly.

[0019] By adopting the above scheme, by arranging the second dichroic mirror, it can only reflect the radiation light, so as not to affect the propagation of the excitation light beam, and the reflected radiation light can also be reflected into the signal collection optical fiber to be introduced into the spectrometer to form a spectrum signal.

[0020] In one embodiment of the present application, the receiving and detecting device is located in the emission direction of the scanning assembly to receive and detect the radiation light, and the receiving and detecting device comprises an optical fiber assembly, a spectrometer and a computer. The optical fiber assembly is connected with the optical spectrum analyzer, the control module is electrically connected with the optical spectrum analyzer, the computer and the driving device, the optical fiber assembly is used for receiving the reflected radiation light of the light beam guiding unit and guiding the radiation light signal to the optical spectrum analyzer to form a spectrum signal, and the spectrum signal is analyzed by using the computer; The optical fiber assembly comprises: A collection focusing lens is arranged on one side of the light beam guiding unit, and the surface of the collection focusing lens is perpendicular to the reflected radiation light of the light beam guiding unit to focus the radiation light. A signal collection optical fiber is arranged on one side of the collection focusing lens to collect the radiation light emitted by the collection focusing lens and couple the radiation light into the optical spectrum analyzer.

[0021] Through the above scheme, after the radiation light is emitted, it sequentially passes through the scanning assembly and the light beam guiding unit and is transmitted into the signal collection optical fiber, and the signal collection optical fiber cooperates with the collection focusing lens to couple the radiation light into the optical spectrum analyzer, so that the spectrum signal is analyzed by using the computer, and the content and abundance of the to-be-measured element inside the plasma are conveniently calculated.

[0022] In one embodiment of the present application, the control module comprises a digital signal generator and a galvanometer control card. The digital signal generator is electrically connected with the first laser, the second laser and the computer. The galvanometer control card is electrically connected with the driving device and is used for controlling the rotation of the directing mirror to make the pretreatment light beam and the excitation light beam move on a two-dimensional plane.

[0023] Through the above scheme, the frequency of the first laser and the second laser is controlled by using the digital signal generator, so that the pulse sequence of the high-frequency narrow-line-width laser and the resonance laser is controlled, the pulse delay of the high-frequency laser and the resonance laser is consistent with the time evolution process of the plasma, and then the high-frequency laser acts on the surface of the coal sample to generate the plasma, and the resonance laser can reach the plasma before the plasma emits the radiation light, so as to resonate the to-be-measured element.

[0024] The second purpose of the present application is to provide a coal isotope online detection method based on multi-wavelength coupling resonance enhancement.

[0025] In order to achieve the above purpose, the technical scheme of the present application is as follows: a coal isotope online detection method based on multi-wavelength coupling resonance enhancement is detected by using a coal isotope online detection system based on multi-wavelength coupling resonance enhancement, and comprises the following steps: A pretreatment step: a first energy beam is applied to a to-be-measured point of a coal sample to perform pretreatment before spectrum analysis of the to-be-measured point, and a purified analysis area is formed. The excitation enhancement step: in the purified analysis area, a second energy beam containing a resonant laser matched with the characteristic wavelength of the element to be detected is applied to excite the plasma and achieve resonance enhancement, so as to obtain a radiation light signal with high signal-to-noise ratio; The analysis step: collect and analyze the radiation light signal to obtain the isotope information of the element to be detected.

[0026] By using the above scheme, the surface of the coal sample is pretreated by the first energy beam, and then when the second energy beam irradiates the measured point passed by the first energy beam, the low-boiling-point impurities have been sublimed in advance, reducing the interference of the smoke generated by the low-boiling-point impurities on the radiation light signal, reducing the complexity of the spectrum line, and also reducing the smoke generated when the second energy beam irradiates the measured point. At the same time, it also reduces the difficulty of preparing the coal sample.

[0027] In summary, the present application has at least one of the following beneficial technical effects: by splitting the high-frequency narrow-line-width laser before combining it with the resonant laser, and combining the high-frequency laser formed after splitting with the resonant laser, and making the pretreatment beam and the excitation beam parallel to the scanning assembly, the scanning assembly is used to realize the same-angle deflection of the two lasers, so that the two lasers act on the surface of the coal sample in parallel and with a certain interval. The excitation beam can move along the moving route of the pretreatment beam, thereby ensuring that the excitation beam produces less impurity component radiation light when resonantly exciting the coal sample, and also avoiding the interference of the generated smoke on the collection of radiation light, and improving the data reliability.

[0028] By combining the high-frequency laser and the resonant laser, and setting the picosecond-level pulse interval of the two lasers, the two lasers can produce plasma when acting on the surface of the coal sample, and the resonant laser resonantly excites the element to be detected inside the plasma before the plasma emits radiation light, so that the element to be detected emits a radiation light signal with higher light intensity. Therefore, when analyzing the spectrum signal of the radiation light, the spectrum signal is more obvious.

[0029] By using the driving device to deflect the galvanometer at a high speed and a small angle, the excitation beam can scan the surface of the coal sample in a dot matrix manner. Compared with the movement of the coal sample, the scanning speed is faster, which improves the efficiency of scanning the coal sample. In combination with the focusing lens, not only the scanning is fast, but also the laser spot can be made very small, realizing high-resolution detection and avoiding signal blurring.

[0030] In the two processes of exciting plasma on the surface of the coal sample and collecting the radiation light emitted by the plasma, the light paths of the above excitation and collection are highly coincident, so that the collection focus moves synchronously with the excitation focus, ensuring that the signal can be efficiently and stably collected, and greatly improving the integration and collection efficiency of the system. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a schematic diagram of a coal isotope online detection system based on multi-wavelength coupling resonance enhancement provided in an embodiment of the present application; Figure 2 is a front view of a scanning assembly of a coal isotope online detection system based on multi-wavelength coupling resonance enhancement provided in an embodiment of the present application; Figure 3 is a path schematic diagram of the excitation light beam scanning the coal sample in the coal isotope online detection system based on multi-wavelength coupling resonance enhancement provided in an embodiment of the present application; Figure 4 is a flow schematic diagram of a coal isotope online detection method based on multi-wavelength coupling resonance enhancement provided in an embodiment of the present application.

[0032] Reference signs: 1, laser generation unit; 11, first laser; 12, second laser; 13, control module; 2, beam combining device; 21, reflecting mirror; 22, first dichroic mirror; 3, scanning assembly; 31, galvanometer cavity; 32, guide reflecting mirror; 33, driving device; 34, focusing lens; 4, beam guiding unit; 41, second dichroic mirror; 5, receiving and detecting device; 51, optical fiber assembly; 511, collection focusing lens; 512, signal collection optical fiber; 52, spectrometer; 53, computer; 6, beam splitting device; 61, beam splitter; 62, laser reflecting mirror; 7, coal sample. DETAILED DESCRIPTION

[0033] The following will be described in detail in combination with the accompanying Figures 1-4 The coal isotope online detection system and method based on multi-wavelength coupling resonance enhancement provided in the present application will be further described in detail.

[0034] Please refer to Figure 1The coal isotope online detection system based on multi-wavelength coupling resonance enhancement provided in the embodiments of the present application comprises a laser generation unit 1, a scanning assembly 3 and a beam guiding unit 4, one laser generation unit 1 is configured to generate a pretreatment beam and an excitation beam, one beam guiding unit 4 is configured to guide the pretreatment beam and the excitation beam to a coal sample surface in a fixed spatial relative position relationship, and one scanning assembly 3 is configured to drive the pretreatment beam and the excitation beam to synchronously scan on the sample surface, so that at any scanning position, the pretreatment beam always acts on the same sample point before the excitation beam, wherein the pretreatment beam is configured to pretreat the sample point to reduce the matrix effect of subsequent spectrum detection; the excitation beam comprises a resonance laser component, the wavelength of which matches the characteristic wavelength of the element to be detected, and the excitation beam is configured to produce plasma on the pretreated sample point and perform resonance excitation to obtain enhanced radiation light, the device is configured to make the pretreatment beam and the excitation beam act on the coal sample 7 in parallel and at intervals, so that the coal sample performs resonance excitation on the plasma after the plasma is produced, the probability of migration of the element to be detected is greater, and the spectrum signal of the element to be detected is enhanced, at the same time, the pretreatment beam evaporates impurities with low boiling points in advance, reduces the generation of smoke and dust, and reduces the interference on the collected radiation light.

[0035] Please continue to refer to Figure 1 The laser generation unit 1 comprises a first laser 11, a second laser 12 and a control module 13, the first laser 11 and the second laser 12 are electrically connected with the control module 13, the first laser 11 is configured to emit the high-frequency narrow linewidth laser, the second laser 12 is configured to emit the resonance laser, and the control module 13 is configured to control the frequencies of the first laser 11 and the second laser 12 to set the delay time between the picosecond-level pulses of the high-frequency narrow linewidth laser and the resonance laser.

[0036] In the embodiment, the working wavelength of the high-frequency narrow linewidth laser can be 532 nm, and the frequency is 10-150 KHz. The first laser 11 can be a high-frequency fiber laser, the second laser 12 can be an optical parametric oscillator (OPO) wavelength continuous tunable fiber laser, and the first laser 11 and the second laser 12 are arranged in parallel. The power of the first laser 11 is above 50 W, the frequency is above 1 KHz, and the pulse width is above 10 ns. The working range of the second laser 12 is between 220-400 nm, the power is above 25 W, the frequency is above 3 KHz, and the pulse width is 5 ns.

[0037] Please continue to refer to Figure 1The laser generating unit 1 further comprises a beam splitting device 6 and a beam combining device 2 on the light path of the laser generating unit 1, the beam splitting device 6 comprises a beam splitter 61 and a laser reflecting mirror 62; The beam splitter 61 is arranged along the propagation direction of the high-frequency narrow linewidth laser and is used for splitting the high-frequency narrow linewidth laser and forming a pretreatment beam and a high-frequency laser, so that the pretreatment beam is incident into the scanning assembly 3, and the laser reflecting mirror 62 is arranged along the propagation direction of the high-frequency laser and is used for deflecting the high-frequency laser, so that the high-frequency laser is incident into the beam combining device 2.

[0038] Please continue to refer to Figure 1 The beam combining device 2 comprises a reflecting mirror 21 and a first dichroic mirror 22. The reflecting mirror 21 is arranged along the propagation direction of the resonant laser and is used for reflecting the resonant laser to the first dichroic mirror 22, and the first dichroic mirror 22 is arranged along the propagation direction of the high-frequency laser and is used for transmitting the high-frequency laser and reflecting the resonant laser emitted by the second laser 12, so that the high-frequency laser and the resonant laser are combined to form the excitation beam.

[0039] In the embodiment, the reflecting mirror 21 is arranged at 45° along the propagation direction of the resonant laser, the surface of the reflecting mirror 21 can be coated with an ultraviolet-enhanced aluminum film, so that the resonant laser is turned by 90° after passing through the reflecting mirror 21, and the reflectivity of the reflecting mirror 21 in the wavelength band of 220-400 nm reaches 85%-95%; The first dichroic mirror 22 is a long-wave dichroic mirror, and the working wavelength range is visible light to near-infrared band, the first dichroic mirror 22 is arranged at 45° along the propagation direction of the high-frequency narrow linewidth laser, and the first dichroic mirror 22 is arranged above the reflecting mirror 21, so that the resonant laser is incident into the first dichroic mirror 22 at an incident angle of 45°, and then the resonant laser can be combined with the high-frequency narrow linewidth laser and emitted.

[0040] Please refer to Figure 1 and Figure 3The scanning assembly 3 comprises a galvanometer cavity 31, at least two guide mirrors 32 and a driving device 33. The at least two guide mirrors 32 are arranged in the galvanometer cavity 31 in sequence along the propagation direction of the excitation light beam and the pretreatment light beam. The guide mirrors 32 are coated with ultraviolet-enhanced aluminum film. The driving device 33 is arranged on the galvanometer cavity 31 and connected with the guide mirrors 32 to deflect the pretreatment light beam and the excitation light beam so that the pretreatment light beam and the excitation light beam are emitted in a direction perpendicular to the incident direction of the excitation light beam.

[0041] Please refer to Figure 2 The driving device 33 can be a servo motor. The driving shaft of the servo motor is connected with the guide mirror 32. By controlling the rotation angle and rotation speed of the servo motor, the deflection angle and rotation speed of the guide mirror 32 can be controlled so that the beam combining fiber can perform dot array scanning on the surface of the coal sample.

[0042] Please refer to Figure 3 The scanning assembly 3 further comprises a focusing lens 34 arranged on the galvanometer cavity 31. The focusing lens 34 is configured to focus the pretreatment light beam and the excitation light beam so that the focal points of the pretreatment light beam and the excitation light beam are located on the surface of the coal sample.

[0043] In the embodiment, the focusing lens 34 can be a microscopic focusing objective lens.

[0044] Please continue to refer to Figure 1 The light beam guiding unit 4 is a second dichroic mirror 41. The light beam guiding unit 4 is arranged on the light path between the beam combining device 2 and the scanning assembly 3.

[0045] In the embodiment, the second dichroic mirror 41 can also be a long-wave pass dichroic mirror with a working wavelength range from ultraviolet to near-infrared band. The second dichroic mirror 41 is used to couple the radiation light into the fiber while filtering out stray light generated during excitation of the excitation light beam. The first dichroic mirror 22 and the second dichroic mirror 41 are long-wave pass mirror pieces capable of providing high reflectivity and transmissivity to ensure effective use of light energy and realize light beam isolation in a specific wavelength range to improve collection efficiency.

[0046] The second dichroic mirror 41 is arranged at an angle of 45° along the propagation direction of the excitation light beam. The fiber assembly 51 is located above the second dichroic mirror 41. When the radiation light returns along the original light path, the radiation light is reflected by the second dichroic mirror 41 and deflected by 90° to be incident into the fiber assembly 51.

[0047] Please continue to refer to Figure 1Further comprising a receiving detection device 5 located in the direction of the outgoing light of the scanning assembly 3 to receive and detect the radiation light, the receiving detection device 5 comprising a fiber assembly 51, a spectrometer 52 and a computer 53, the fiber assembly 51 being connected with the spectrometer 52, the control module 13 being electrically connected with the spectrometer 52, the computer 53 and the driving device 33, the fiber assembly 51 being used to receive the reflected radiation light of the light beam guiding unit 4 and guide the radiation light signal to the spectrometer 52 to form a spectrum signal, and the computer 53 is used to analyze the spectrum signal.

[0048] In the embodiment, the resolution of the spectrometer 52 is 0.01 nm, which is higher than the spectral shift of the laser-induced breakdown spectroscopy of the detected substance molecules; Wherein, since the spectral shift of the isotopes is small, the signal peak to be detected is easily covered in the interference peak, and no obvious wave peak can be observed, in order to avoid the peak position information error caused by the overlapping of the signal peaks, in addition to the high-resolution excitation collection of the system, high-resolution processing is needed in data analysis, in order to realize the high-resolution analysis of the spectrum peak and improve the detection sensitivity of the system, the data processing can be carried out in the following steps: a: spectrum data pretreatment: the spectrum noise is smoothed and denoised, and after the spectrum fluctuation is removed, the main characteristics and trends of the spectrum can be clearly shown, and the possibility of misjudgment of the overlapping peaks of the spectrum is reduced. In the embodiment of the application, the collected spectrum signal is smoothed by using the Savitzky-Golay (S-G) algorithm to obtain the smoothed spectrum data; b: determination of the existence of isotopes: the spectral shift between isotopes is small, which leads to the overlapping of multiple peaks, and no obvious wave peak can be observed on the spectrum graph, but the peak shape deviates from the standard single-peak shape, whether there is an overlapping peak can be analyzed and explained by the symmetry or the peak width of the peak, the spectrum is pixel-level abnormally detected by using an attention mechanism convolutional neural network (AM-CNN), the convolutional neural network (CNN) automatically extracts the spectrum features, the attention mechanism module enhances the abnormal spectrum features, the model is divided into a convolutional layer, an attention mechanism module and a fully connected layer, the smoothed spectrum data is input into the convolutional layer to extract the spectrum features; The fully connected layer and the output layer are used for the spectrum classification task with overlapping peaks, the attention mechanism module extracts the features based on the channel dimension, and the features are fused through the fully connected layer, the channel attention weight is obtained, the features in the spectrum are multiplied by the weight and output, the fully connected layer integrates and converts the features, learns the complex linear relationship between the features and maps them to a new feature space, the AM-CNN gives different weights to each pixel in the spectrum during the analysis process, highlights the pixels related to the abnormal features, and accurately locates the potential overlapping position through a large amount of data learning; c: Minimum Covariance Determinant (MCD) algorithm aims to find the subset with the minimum covariance determinant, in the overlapping peak spectrum screening scenario, it extracts the corresponding part of each spectrum according to the abnormal features extracted by AM-CNN to construct a sample matrix, and applies the MCD algorithm to find the subset with the minimum covariance determinant, the spectrum data corresponding to these subsets are normal spectrum, and the Mahalanobis distance between each spectrum data and the normal subset is calculated as formula:

[0049] Wherein, is a single spectrum sample, is the MCD overall mean estimation, is the minimum covariance subset matrix, and comparison is made according to a suitable threshold to determine whether there is an overlapping peak, MCD has fast calculation speed and is suitable for multivariate data screening analysis in industrial field; By training the AM-CNN model in advance, learning a large number of non-overlapping peak models and overlapping peak models, inputting the denoised spectrum data when applying, quickly extracting the spectrum abnormal features, inputting the spectrum sample matrix of MCD, calculating the minimum covariance determinant value, calculating the covariance of each spectrum, and comparing with the former, screening out the abnormal spectrum data exceeding the threshold range and outputting; d: After determining that there is an overlapping peak, the related peak information of the element to be tested needs to be extracted for peak separation and subsequent abundance and quantitative analysis, since the spectrum of the element to be tested has a small offset, the overlapping peak situation is complex, and the detailed information of the spectrum peak of the isotopes to be tested is easily disturbed by other elements, so a peak resolution enhancement algorithm is needed to highlight the peak position.

[0050] In the related art, the Richard-Lucy algorithm considers that the observation data is the convolution result of the true data and the instrument function, which is commonly used in image processing to improve the resolution by deconvolution of low-resolution images; In the example of the present application, the instrument function selects a one-dimensional Gaussian kernel psf_width (point spread function width) and the number of iterations to realize the amplification of the small details of the spectrum with overlapping peaks, focus on the abnormal features in the spectrum data caused by overlapping, and increase the separation degree of the overlapping peaks; Through wavelet transform combined with curve fitting algorithm, coarse screening and fine repair of peak information are realized, appropriate wavelet basis is selected, not only denoising but also screening peak candidate area, on the basis of wavelet transform identifying potential peaks, multi-peak fitting is based on Voigt line type using formula:

[0051] The overlapped peaks are fitted, the initial parameters extracted based on the wavelet are finely adjusted, overfitting is prevented, the Daubechies 4 is selected as a base function of wavelet transform, the high-frequency wavelet coefficients are extracted, and the data after wavelet reconstruction is subjected to peak searching to obtain the preliminary screened peak value, peak height and peak width, so that subsequent fitting is facilitated, and in order to realize lightweight operation, the Levenberg-Marquardt (LM) algorithm is combined in the multi-peak fitting process to adjust parameters, accelerate convergence, and adapt to online rapid detection.

[0052] In actual application, the isotopic abundance is calculated through the ratio of parameters such as peak height and area, and distribution imaging and quantification are realized according to the spectrum collection position, the performance is comprehensively evaluated before the model is applied, and the performance of completing pretreatment, qualitative and quantitative is guaranteed.

[0053] Among them, the accuracy Accuracy of the overlapped peak classification is used as an evaluation index as formula (1); the determination coefficient R2 of the multi-peak fitting is used as an evaluation index as formula (2), and absolute and relative indexes are used in the quantitative process, including the mean absolute error MAE in formula (3), the root mean square error RMSE in formula (4) and the determination coefficient R2.

[0054]

[0055] 1 when the sample classification is correct, otherwise 0, n represents the number of samples; represents the observed value (label) of the i th sample, represents the predicted value of the i th sample, and represents the average value of all sample observed values.

[0056] In addition, for the parts not fully disclosed in the present application, those skilled in the art can ensure that the scheme of the present application can be smoothly implemented based on common sense, normal thinking logic and existing technology.

[0057] Please continue to refer to Figure 1 The optical fiber assembly 51 comprises a collection focusing lens 511 and a signal collection optical fiber 512, the collection focusing lens 511 is arranged on one side of the light beam guiding unit 4, the surface of the collection focusing lens 511 is perpendicular to the reflected radiation light of the light beam guiding unit 4, so as to focus the radiation light, and the signal collection optical fiber 512 is located on one side of the collection focusing lens 511, so as to collect the radiation light emitted by the collection focusing lens 511 and couple the radiation light into the spectrometer 52.

[0058] Please continue to refer to Figure 1The control module 13 comprises a digital signal generator (not shown in the figure) and a galvanometer control card (not shown in the figure), the digital signal generator is electrically connected with the first laser 11, the second laser 12 and the computer 53, and the galvanometer control card is electrically connected with the driving device 33, so as to control the rotation of the directing mirror 32, so that the pretreatment light beam and the excitation light beam move on a two-dimensional plane.

[0059] In the embodiment, the delay resolution of each channel of the digital signal generator in the control module 13 is not less than 10 ps, and the delay jitter between channels is not greater than 50 ps. The electrical connection mode between the digital signal generator and the first laser 11, the second laser 12 and the computer 53, and the electrical connection mode between the galvanometer control card and the driving device 33 are all conventional technical means of those skilled in the art, so they are not described again.

[0060] The second purpose of the present application is to provide a coal isotope online detection method based on multi-wavelength coupling resonance enhancement.

[0061] Please refer to Figure 4 In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows: a coal isotope online detection method based on multi-wavelength coupling resonance enhancement, which is detected by a coal isotope online detection system based on multi-wavelength coupling resonance enhancement, comprising the following steps: A pretreatment step: a first energy beam is applied to a to-be-measured point of a coal sample to perform pretreatment before spectral analysis of the to-be-measured point, thereby forming a purified analysis area; An excitation enhancement step: a second energy beam containing a resonance laser matched with the characteristic wavelength of the to-be-measured element is applied to the purified analysis area to excite plasma and achieve resonance enhancement, thereby obtaining a radiation light signal with high signal-to-noise ratio; An analysis step: the radiation light signal is collected and analyzed to obtain the isotope information of the to-be-measured element.

[0062] As described above, when the device is used to detect the to-be-measured element in the coal sample, first, the scanning assembly 3 is started, and the coal sample is placed on the workbench to ensure that the coal sample is within the scanning range of the scanning assembly 3. The laser generation unit 1 is turned on, and the high-frequency narrow linewidth laser forms a pretreatment light beam and a high-frequency laser after passing through the beam splitting device 6. The high-frequency laser and the resonance laser are combined into an excitation light beam capable of resonantly exciting the surface of the coal sample 7 after passing through the beam combining device 2. The excitation light beam generates plasma by acting on the surface of the coal sample, and resonantly excites the radiation light. The control assembly sets the pulse interval delay between the two lasers to ensure the best excitation effect. After the plasma emits the radiation light, the radiation light returns along the light path of the excitation light beam, and at the second dichroic mirror 41, is reflected into the signal collection optical fiber 512, and forms a corresponding spectral signal in the spectrometer 52; After the spectral signal collection of a single point is completed, the scanning assembly 3 is controlled to make the excitation light beam move along the moving path of the pretreatment light beam, and the spectral signal collection of the next point is performed, until the point array scanning is completed. Finally, the spectrometer 52 collects the spectral information of the isotopes contained in the coal sample scanning point array, and finally delivers the spectral information to the computer 53 for analysis and processing.

[0063] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, so that: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. The coal isotope online detection system based on multi-wavelength coupled resonance enhancement is characterized by: include: A laser generating unit (1) is configured to generate a pretreatment beam and an excitation beam; a beam guiding unit (4) configured to guide the pre-processing beam and the excitation beam to a surface of a coal mine sample in a fixed spatial relative position relationship; a scanning assembly (3) configured to drive the pretreatment light beam and the excitation light beam to perform synchronous scanning on the sample surface, so that at any scanning position, the pretreatment light beam always acts on the same sample point before the excitation light beam; The pretreatment beam is configured to pretreatment the sample point to reduce the matrix effect of subsequent spectral detection; the excitation beam contains a resonant laser component whose wavelength matches the characteristic wavelength of the element to be measured, and the excitation beam is configured to generate plasma at the pretreated sample point and perform resonant excitation to obtain enhanced radiation light.

2. The coal isotope online detection system based on multi-wavelength coupled resonance enhancement according to claim 1 is characterized in that: The laser generating unit (1) comprises a first laser (11), a second laser (12) and a control module (13); the first laser (11) and the second laser (12) are both electrically connected to the control module (13); the first laser (11) is configured to emit high-frequency narrow-linewidth laser light; the second laser (12) is configured to emit resonant laser light; and the control module (13) is configured to control the frequencies of the first laser (11) and the second laser (12) to set a picosecond pulse delay between the high-frequency narrow-linewidth laser light and the resonant laser light.

3. The coal isotope online detection system based on multi-wavelength coupled resonance enhancement according to claim 2 is characterized in that: The laser generating unit (1) further comprises a beam splitting device (6) and a beam combining device (2) located on its light output path, wherein the beam splitting device (6) comprises a beam splitter (61) and a laser reflecting mirror (62); The beam splitter (61) is arranged along the propagation direction of the high-frequency narrow-linewidth laser and is used to split the high-frequency narrow-linewidth laser and form the pre-processing beam and the high-frequency laser, so that the pre-processing beam is injected into the scanning component (3); The laser reflector (62) is arranged along the propagation direction of the high-frequency laser and is used to deflect the high-frequency laser so that the high-frequency laser is parallel to the pre-processed light beam and is emitted into the beam combining device (2).

4. The coal isotope online detection system based on multi-wavelength coupled resonance enhancement according to claim 3 is characterized in that: The beam combining device (2) comprises a reflector (21) and a first dichroic mirror (22); The reflecting mirror (21) is arranged along the propagation direction of the resonant laser and is used to reflect the resonant laser to the first dichroic mirror (22); The first dichroic mirror (22) is arranged along the propagation direction of the high-frequency laser and is used to transmit the high-frequency laser and reflect the resonant laser emitted by the second laser (12), so that the high-frequency laser and the resonant laser are combined to form the excitation light beam.

5. The coal isotope online detection system based on multi-wavelength coupling resonance enhancement according to claim 2 is characterized in that: The scanning assembly (3) comprises: a galvanometer cavity (31), at least two guide reflective mirrors (32) and a driving device (33); At least two guide reflectors (32) are arranged inside the galvanometer cavity (31) and are sequentially arranged along the propagation directions of the excitation light beam and the pre-processing light beam, and the guide reflectors (32) are coated with a UV-enhanced aluminum film; The driving device (33) is arranged on the galvanometer cavity (31) and is connected to the guide reflector (32) to deflect the preprocessing light beam and the excitation light beam so that the preprocessing light beam and the excitation light beam are emitted along an incident direction perpendicular to the excitation light beam.

6. The coal isotope online detection system based on multi-wavelength coupling resonance enhancement according to claim 5 is characterized in that: The scanning assembly (3) further includes a focusing lens (34), which is mounted on the galvanometer cavity (31). The focusing lens (34) is configured to focus the pre-processing light beam and the excitation light beam so that the focal points of the pre-processing light beam and the excitation light beam are located on the surface of the coal mine sample.

7. The coal isotope online detection system based on multi-wavelength coupled resonance enhancement according to claim 3 is characterized in that: The light beam guiding unit (4) is a second dichroic mirror (41), and the light beam guiding unit (4) is arranged on the light path between the beam combining device (2) and the scanning component (3).

8. The coal isotope online detection system based on multi-wavelength coupled resonance enhancement according to claim 5 is characterized in that: The system further comprises a receiving and detecting device (5), which is located in the direction of the emitted light of the scanning component (3) to receive and detect the radiated light, and the receiving and detecting device (5) comprises an optical fiber component (51), a spectrometer (52) and a computer (53); The optical fiber assembly (51) is connected to the spectrometer (52), the control module (13) is electrically connected to the spectrometer (52), the computer (53) and the driving device (33), the optical fiber assembly (51) is used to receive the radiation light reflected by the light beam guiding unit (4), and guide the radiation light signal to the spectrometer (52) to form a spectrum signal, and the computer (53) is used to analyze the spectrum signal; The optical fiber assembly (51) comprises: a collecting and focusing lens (511), the collecting and focusing lens (511) being arranged on one side of the light beam guiding unit (4), the surface of the collecting and focusing lens (511) being perpendicular to the radiation light reflected by the light beam guiding unit (4), so as to focus the radiation light; A signal collecting optical fiber (512) is located on one side of the collecting focusing lens (511) to collect the radiation light emitted by the collecting focusing lens (511) and couple the radiation light into the spectrometer (52).

9. The coal isotope online detection system based on multi-wavelength coupled resonance enhancement according to claim 8, characterized in that: The control module (13) includes a digital signal generator and a galvanometer control card; The digital signal generator is electrically connected to the first laser (11), the second laser (12) and the computer (53); The galvanometer control card is electrically connected to the driving device (33) and is used to control the rotation of the guide reflector (32) so that the preprocessing light beam and the excitation light beam move on a two-dimensional plane.

10. A method for online detection of coal isotopes based on multi-wavelength coupled resonance enhancement, characterized in that: Detection is performed using the coal isotope online detection system based on multi-wavelength coupled resonance enhancement as described in any one of claims 1 to 9, comprising the following steps: Pre-processing step: applying a first energy beam to a point to be measured on a coal mine sample to perform pre-processing on the point to be measured before spectral analysis to form a purified analysis area; Excitation enhancement step: applying a second energy beam containing a resonant laser that matches the characteristic wavelength of the element to be measured in the purified analysis area to excite and generate plasma and achieve resonance enhancement, thereby obtaining a radiation light signal with a high signal-to-noise ratio; Analysis step: Collecting and analyzing the radiation light signal to obtain the isotope information of the element to be measured.

Images