A probe type mineral multi-element laser-induced breakdown spectroscopy detection device

Abstract

This invention provides a probe-type multi-element laser-induced breakdown spectroscopy detection device for minerals, comprising: a sealed quartz optical window mounted on the side of the probe box; a laser facing the sealed quartz optical window, emitting laser pulses towards the mineral being detected; a quartz crescent-shaped focusing lens, with its convex surface facing the laser and its concave surface facing the sealed quartz optical window, focusing the laser pulses onto the surface of the mineral being detected to generate plasma; a dichroic mirror reflecting the plasma emitted light to a dual-lens group; the emitted light being converged by the dual-lens group to form a plasma image with reduced chromatic aberration; and a spectrometer coupled to the plasma image via an optical fiber mechanism to record spectra in different wavelength bands. Thus, the focal point of the light reflected by the crescent-shaped focusing lens is pushed back behind the laser, avoiding damage to its optical components; the dual-lens group reduces the chromatic aberration of the plasma image; and the optical fiber mechanism, through spatial resolution, balances the spectral intensity of different wavelength bands and suppresses the continuous spectrum.

Description

Technical Field

[0001] This invention relates to the field of mineral fragment element detection technology, and in particular to a probe-type multi-element laser-induced breakdown spectroscopy detection device for minerals. Background Technology

[0002] Sampling and analyzing mineral fragments, or conducting online testing directly on conveyor belts, is of great significance to many sectors of the national economy, such as mineral mining and processing, customs inspection of imported minerals, and industrial process optimization and control. Typical requirements include multi-element, multi-index analysis of ores, providing in-situ, online, real-time, accurate, and efficient analytical data.

[0003] Laser-induced breakdown spectroscopy (LIBS) has the potential to achieve the above-mentioned detection and analysis. However, real-world engineering applications place special requirements on LIBS equipment: for example, sufficient working distance, a sealed equipment environment, a stable and compact structure, and reasonable weight to adapt to changing and complex detection scenarios.

[0004] Currently, some existing LIBS devices designed for in-situ, online applications still have some shortcomings:

[0005] The complexity of the optical system leads to an increase in the number of optical components, equipment size, and weight; the use of plano-convex focusing lenses causes the laser pulse to be reflected at the interface between the convex or flat lens and the air, and then focused back by the lens, resulting in damage to other optical components and the laser in the equipment; the plasma emission light collection optical system exhibits significant chromatic aberration, which makes it impossible to simultaneously optimize the spectral intensity of the near-ultraviolet, visible, and infrared spectral channels.

[0006] Therefore, there is an urgent need for a new type of multi-element laser-induced breakdown spectroscopy detection equipment for minerals to solve the above problems. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a probe-type multi-element laser-induced breakdown spectroscopy detection device for minerals, which solves or partially solves the technical problems in the prior art such as excessively large device size and weight, easy damage to optical components such as lasers by reflected light, inability to simultaneously optimize the spectral intensity of different spectral channels, and impact on the accuracy of element content prediction.

[0008] This invention provides a probe-type mineral multi-element laser-induced breakdown spectroscopy detection device, the device comprising: a probe box, a laser, a quartz crescent focusing lens, a dichroic mirror, a dual lens group, an optical fiber mechanism, and a spectrometer;

[0009] A sealed quartz optical window is provided on one side of the probe box;

[0010] The laser is installed inside the probe box, facing the mineral being detected, and emits laser pulses through the sealed quartz optical window; the emission optical axis of the laser passes through the dichroic mirror, the quartz crescent focusing lens, and the sealed quartz optical window, and is perpendicularly pointed to the contour surface of the mineral being detected.

[0011] The quartz crescent focusing lens is located between the laser and the sealed quartz optical window. The convex surface of the quartz crescent focusing lens faces the laser, and the concave surface of the quartz crescent focusing lens faces the sealed quartz optical window. The quartz crescent focusing lens is used to focus the laser pulse emitted by the laser onto the surface of the mineral being detected to generate plasma.

[0012] The dichroic mirror is located between the laser and the quartz crescent focusing lens, and is positioned on the emission optical axis of the laser to reflect the emitted light of the plasma to the dual lens group.

[0013] The dual-lens group is located on one side of the dichroic mirror and on the collecting optical axis perpendicular to the emission optical axis. The dual-lens group is used to converge the emitted light of the plasma reflected by the dichroic mirror to form a plasma image on the collecting optical axis. The plasma image is coupled to the spectrometer through the optical fiber mechanism.

[0014] The spectrometer is used to perform spectral detection on the plasma image to obtain the emission spectra of the plasma in different wavebands.

[0015] In the above scheme, the industrial control computer is located inside the probe box and is used to read the emission spectrum of the plasma transmitted by the spectrometer and analyze the emission spectrum of the plasma.

[0016] In the above scheme, the spectrometer includes: an ultraviolet light module, a visible light module, and an infrared light module;

[0017] The ultraviolet light module is used to record spectra with a wavelength range of 230~350nm;

[0018] The visible light module is used to record spectra with wavelengths ranging from 340 to 505 nm;

[0019] The infrared light module is used to record spectra with wavelengths ranging from 495 to 800 nm.

[0020] In the above scheme, the optical fiber mechanism includes: an optical fiber and an optical fiber adjustment bracket;

[0021] The optical fiber is a three-core split fiber patch cord, with the input end mounted on the fiber adjustment bracket and the output end connected to the ultraviolet light module, visible light module and infrared light module of the spectrometer, respectively.

[0022] A fiber optic adjustment bracket, located downstream of the optical path of the dual-lens group, is used to adjust the fiber input end to be aligned with the collecting optical axis, so that the fiber input end overlaps face-to-face with the plasma image. The fiber optic adjustment bracket is also used to adjust the spatial position of the fiber input end according to the plasma image. The fiber optic adjustment bracket is fixed by a fixing component, and in a coordinate system constructed with the fixing component as the origin, the fiber optic adjustment bracket can be adjusted in the x, y, and z directions.

[0023] In the above scheme, the optical fiber includes: ultraviolet band optical fiber, visible band optical fiber and infrared band optical fiber;

[0024] When the input end of the optical fiber is installed on the optical fiber adjustment bracket, the ultraviolet band optical fiber and the visible band optical fiber are placed side by side in the upper row, and the infrared band optical fiber is placed in the lower row adjacent to the upper row. The infrared band optical fiber is located below the contact position of the ultraviolet band optical fiber and the visible band optical fiber.

[0025] In the above scheme, the dual-lens group includes: a biconvex lens and a biconcave lens;

[0026] The biconvex lens is a positive focal length lens, located downstream of the optical path of the dichroic mirror; the biconcave lens is a negative focal length lens, located downstream of the optical path of the biconvex lens; the biconvex lens is made of calcium fluoride, and the biconcave lens is made of fused silica.

[0027] The surface radius of curvature, focal length, surface radius of curvature, and focal length of the biconvex lens can be combined according to the detection wavelength range of the spectrometer.

[0028] In the above solution, the device further includes:

[0029] The first water-cooled heat dissipation plate is in contact with one side of the industrial control computer and is used to dissipate heat from the industrial control computer.

[0030] In the above solution, the device further includes:

[0031] A photodiode, located on the other side of the dichroic mirror, is positioned on a collecting optical axis perpendicular to the emitting optical axis. It is used to receive a small portion of the laser pulses and determine the energy of the laser pulses based on the small portion of the laser pulses.

[0032] In the above scheme, the device further includes: a second water-cooled heat dissipation plate, which is in contact with one side of the laser and is used to dissipate heat from the laser.

[0033] In the above solution, the device further includes:

[0034] The dust removal and drying cold air inlet is located on the other side of the probe box;

[0035] The cooling water inlet is located on one side of the dust removal and drying cold air inlet;

[0036] The cooling water outlet is located on one side of the cooling water inlet;

[0037] The electrical signal inlet and outlet are located on one side of the cooling water outlet;

[0038] The power supply, located inside the probe housing, provides power to the laser, industrial control computer, and photodiode.

[0039] This invention provides a probe-type multi-element laser-induced breakdown spectroscopy (LIBS) detection device for minerals. The device includes: a probe box, a laser, a quartz crescent-shaped focusing lens, a dichroic mirror, a dual-lens group, an optical fiber mechanism, and a spectrometer. A sealed quartz optical window is provided on one side of the probe box. The laser is installed inside the probe box, facing the mineral being detected, and emits laser pulses through the sealed quartz optical window. The emission optical axis of the laser passes through the dichroic mirror, the quartz crescent-shaped focusing lens, and the sealed quartz optical window, and is perpendicularly pointed to the contour surface of the mineral being detected. The quartz crescent-shaped focusing lens is located between the laser and the sealed quartz optical window. The convex surface of the quartz crescent-shaped focusing lens faces the laser, and the concave surface faces the sealed quartz optical window. The quartz crescent-shaped focusing lens is used to focus the laser pulse emitted by the laser onto the surface of the mineral being detected, generating plasma. The dichroic mirror is located between the laser and the quartz crescent-shaped focusing lens. The dichroic mirror is located on the emission optical axis of the laser and is used to reflect the emitted light from the plasma to the dual-lens group. A dual-lens group is located on one side of the dichroic mirror and on the collecting optical axis perpendicular to the emission optical axis. The dual-lens group is used to converge the emitted light of the plasma reflected by the dichroic mirror, forming a plasma image on the collecting optical axis. The intensity of the plasma image is coupled to the spectrometer via an optical fiber mechanism. The spectrometer is used to detect the spectrum of the plasma image to obtain the emission spectrum of the plasma in different wavelength bands. Thus, a crescent-shaped focusing lens can be used to focus the laser pulse, and because the convex surface of the crescent-shaped lens faces the laser pulse... The crescent-shaped focusing lens reflects the laser pulse in the direction of emission, causing it to diverge. The focal point of the reflected light can be pushed far behind the laser, avoiding the focal point falling inside the laser and damaging the optical components. In addition, with the crescent lens, there is no need to use a high-reflection mirror to deflect the light, nor is there a need to use a beam expander to extend the diameter of the laser beam. This shortens the optical path, improves the compactness of the equipment, and reduces the size and weight of the equipment. The fiber optic structure, through spatial resolution, can balance the spectral intensity of different bands and suppress the continuous spectrum, thereby simultaneously optimizing the spectral intensity of different spectral channels and improving the accuracy of elemental content prediction. Attached Figure Description

[0040] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0041] Figure 1A schematic diagram of the probe structure of a probe-type mineral multi-element laser-induced breakdown spectroscopy detection device according to an embodiment of the present invention is shown;

[0042] Figure 2 A schematic diagram of the ultraviolet, visible, and infrared three-band spectral balance before optimization is shown according to an embodiment of the present invention.

[0043] Figure 3 A schematic diagram of the spectrum after optimization of the ultraviolet, visible, and infrared three-band spectral balance according to an embodiment of the present invention is shown.

[0044] Figure 4 A schematic diagram of a spectrum without suppression of the continuous spectrum is shown according to an embodiment of the present invention;

[0045] Figure 5 A schematic diagram of the spectrum after continuous spectrum suppression according to an embodiment of the present invention is shown;

[0046] Figure 6 A schematic diagram of a probe-type multi-element laser-induced breakdown spectroscopy detection system for minerals according to an embodiment of the present invention is shown.

[0047] Figure 7 The diagram shows the performance of a multivariate regression model for Al2O3 trained on a convolutional neural network, trained with 75 bauxite crushed stone samples and tested with 15 independent bauxite crushed stone samples.

[0048] Figure 8 The diagram shows the performance of a multivariate regression model for SiO2 trained on a convolutional neural network, trained with 75 bauxite crushed stone samples and tested with 15 independent bauxite crushed stone samples.

[0049] Figure 9 The diagram illustrates the performance of a multivariate regression model for Fe2O3 trained using a convolutional neural network, trained with 75 bauxite gravel samples and tested with 15 independent bauxite gravel samples.

[0050] Explanation of reference numerals in the attached figures:

[0051] 1-Probe box; 2-Laser; 3-Quartz crescent focusing lens; 4-Dichroic mirror; 5-Photodiode; 6-Spectrometer; 71-Biconvex lens; 72-Biconcave lens; 8-Sealed quartz optical window; 91-Mineral to be detected; 92-Plasma; 10-Fiber optic cable; 11-Fiber optic cable adjustment bracket; 12-Three-core split fiber optic cable inlet; 13-Industrial control computer; 14-First water-cooled heat sink; 15-Second water-cooled heat sink; 16-Dust removal and drying cold air inlet; 17-Cooling water inlet; 18-Cooling water outlet; 19-Electrical signal inlet / outlet; 20-Power supply. Detailed Implementation

[0052] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0053] Due to the specific requirements of practical engineering applications for LIBS testing equipment, these requirements are mainly reflected in the following aspects:

[0054] 1. Sufficient working distance (0.2-0.8 meters) to ensure normal and efficient operation of the equipment under complex physical and material conditions;

[0055] 2. Wide spectrum (200–900nm) and high resolution detection to meet the requirements of multi-element and multi-index detection and analysis;

[0056] 3. Sufficient built-in computing and storage capabilities for in-situ data caching and processing; network connectivity for remote device control, such as monitoring device status and transmitting commands and data;

[0057] 4. The sealed internal environment of the equipment ensures that the core components (laser, spectrometer, industrial control computer) can operate in a stable laboratory-like environment, achieving dust prevention, moisture control, and constant temperature, enabling continuous operation around the clock;

[0058] 5. Stable and compact structure and reasonable weight to adapt to changing and complex application scenarios.

[0059] In addition to the problems mentioned in the background section, some existing LIBS testing equipment also have the following problems:

[0060] 1. The plasma emission light collection system has severe color difference, which makes it impossible to simultaneously and effectively couple different wavelengths of light to different wavelength spectrometer modules, resulting in an imbalance between multiple wavelength spectra.

[0061] 2. Spatially resolved emission collection is impossible for a given plasma. Because charge-coupled device (CCD) spectrometers lack sufficiently precise detection gating, the ultraviolet and visible emission spectra are severely affected by the continuous spectrum without spatially resolved collection. This significantly reduces the detection dynamic range of effective elemental emission spectra, causing strong spectral lines to saturate and weak lines to become indistinguishable from noise. The lack of spatially resolved emission collection also exacerbates the aforementioned imbalance between multi-band spectra. Spectra that lack inter-band balance and are severely affected by the continuous spectrum particularly negatively impact multivariate regression based on machine learning, reducing the accuracy of model elemental content predictions.

[0062] 3. The equipment itself does not have computing, storage, and network connection functions, and cannot effectively perform in-situ data caching and processing; it is also inconvenient to remotely control LIBS testing equipment.

[0063] Based on this, the present invention provides a multi-element laser-induced breakdown spectroscopy detection device for ores, such as... Figure 1 As shown, the equipment mainly includes: probe box 1, laser 2, quartz crescent focusing lens 3, dichroic mirror 4, photodiode 5, dual lens group, and spectrometer 6; wherein, the dual lens group includes: biconvex lens 71 and biconcave lens 72.

[0064] A sealed quartz optical window 8 is provided on one side of the probe box 1;

[0065] Laser 2 is installed inside probe box 1. Laser 2 faces the mineral 91 to be detected and emits laser pulses through sealed quartz optical window 8. The emission optical axis of laser 2 is perpendicular to the macroscopic contour surface of the mineral 91 to be detected through dichroic mirror 4, quartz crescent focusing lens 3, and sealed quartz optical window 8.

[0066] A quartz crescent-shaped focusing lens 3 is located between the laser 2 and the sealed quartz optical window 8. The convex surface of the quartz crescent-shaped focusing lens 3 faces the laser 2, and the concave surface faces the sealed quartz optical window 8. The quartz crescent-shaped focusing lens 3 is used to focus the laser pulse emitted by the laser 2 onto the surface of the mineral 91 being detected. The mineral 91 being detected generates plasma 92 under the action of energy. The distance between the mineral 91 being detected and the sealed quartz optical window 8 is approximately 30 cm.

[0067] Dichroic mirror 4 is located between laser 2 and quartz crescent focusing lens 3. Dichroic mirror 4 is located on the emission optical axis and is used to reflect the emitted light of plasma 92 to the double lens group.

[0068] A dual-lens group is located on one side of the dichroic mirror 4 and on the collecting optical axis perpendicular to the emission optical axis. The dual-lens group is used to converge the emitted light of the plasma 92 reflected by the dichroic mirror 4 to form a plasma image on the collecting optical axis. The dual-lens group can reduce the imaging chromatic aberration of the plasma 92. The plasma image is coupled to the spectrometer 6 through an optical fiber mechanism.

[0069] Photodiode 5 is located on the other side of dichroic mirror 4. Photodiode 5 is located on another collecting optical axis perpendicular to the emitting optical axis. It is used to receive a small portion of the laser pulses and determine the energy of the laser pulses based on the small portion of the laser pulses.

[0070] Spectrometer 6 is used to detect the spectrum of the plasma image and record the spectra of plasma 92 in different wavelength bands;

[0071] The industrial control computer 13, located inside the probe box 1, is used to read the spectrum of plasma 92 transmitted by the spectrometer 6 and to analyze the spectrum of plasma 92.

[0072] That is, the emission axis of the laser 2 is directed to the macroscopic contour surface of the mineral 91 being tested via the dichroic mirror 4, the quartz crescent focusing lens 3, and the sealed quartz optical window 8; plasma is generated on the surface of the mineral 91 being tested under the action of high-energy laser pulses, and the emission light of the plasma 92 reaches the dichroic mirror 4 via the sealed quartz optical window 8 and the quartz crescent focusing lens 3. The emission light of the plasma 92 is reflected by the dichroic mirror 4 to the double lens group, and the emission light of the plasma enters the spectrometer 6 after being converged by the double lens group.

[0073] In fact, the emitted light from plasma 92 is focused by a double lens group to form a plasma image, and the light intensity of different parts of the plasma image is coupled to the spectrometer 6 through an optical fiber mechanism.

[0074] The plasma image represents the spatial distribution of light intensity, but optical fibers cannot transmit this spatial distribution globally. Therefore, the optical fiber mechanism cannot directly couple the plasma image, but instead couples the light intensity of different parts of the plasma image to the spectrometer 6.

[0075] Specifically, to provide a sealed environment similar to that of a laboratory for the detection equipment, this invention includes a probe box 1, which is approximately 0.5m in length, width, and height. A sealed quartz optical window 8 is provided on one side of the probe box 1. When the laser 2 emits a laser pulse, it forms an emission optical axis. This axis passes through the quartz crescent focusing lens 3 and the sealed quartz optical window 8, pointing perpendicularly to the macroscopic contour surface of the mineral 91 being detected, generating plasma 92. The reflected light from the plasma 92 enters the probe box 1 through the sealed quartz optical window 8.

[0076] In this process, most laser pulses (approximately 96%) first pass through dichroic mirror 4. Dichroic mirror 4 selectively reflects and transmits light of specific wavelengths, guiding the laser pulses to the sample being tested. Dichroic mirror 4 preferentially exhibits high transmittance (transmittance > 96%) for light waves with wavelengths between 1054 nm and 1074 nm, and high reflectance (reflectance > 90%) for light waves with wavelengths between 230 nm and 850 nm.

[0077] A small portion of the laser pulses (about 4% of the energy) are reflected by the dichroic mirror 4 and enter the photodiode 5. The photodiode 5 is located on one side of the dichroic mirror 4. The photodiode 5 determines the energy of the laser pulse based on the small portion of the laser pulses and sends the energy of the laser pulses to the industrial control computer 13, so that the staff can monitor the operating status of the laser 2 in real time.

[0078] Then, most of the laser pulse energy is focused by the quartz crescent focusing lens 3 and reaches the surface of the mineral 91 being tested. The focused laser pulse has a sufficiently high energy density, generating plasma 92 and causing the plasma 92 to emit light. The emitted light from the plasma 92 then passes through the sealed quartz optical window 8 and reaches the quartz crescent focusing lens 3. After being collimated by the quartz crescent focusing lens 3, it reaches the dichroic mirror 4 and is reflected by the dichroic mirror 4 to the double lens group.

[0079] Laser 2 can be a semiconductor laser-pumped Q-switched Nd:YAG laser with a wavelength of 1064 nm, a frequency of 1-20 Hz, and a single-pulse energy of 40 mJ-120 mJ. For example, a frequency of 10 Hz and a single-pulse energy of 80 mJ can be used.

[0080] The material of the sealed quartz optical window 8 is fused silica, without antireflective coating. The sealed quartz optical window 8 is installed at an angle of 1° to 10° on one side of the probe box 1, for example, 5°.

[0081] The quartz crescent focusing lens 3 is made of fused silica, without an anti-reflective coating, and has a focal length of 300-500mm. In this invention, the focal length of the quartz crescent focusing lens 3 can be 300mm. The convex surface of the quartz crescent focusing lens 3 faces the laser 2 (directly facing the laser pulse emission direction), and the concave surface faces the sealed quartz optical window 8. In this way, while ensuring that the forward focal length remains unchanged, the reverse focal length can be expanded, thereby ensuring that the focal point of the reflected laser pulse falls behind the laser 2 (and does not fall inside the laser), thus avoiding damage to the optical components of the laser 2.

[0082] In addition, by directly using the quartz crescent focusing lens 3, there is no need to use a high-reflection mirror to deflect the light, nor is there a need to use a beam expander to extend the diameter of the laser beam. This can shorten the optical path, improve the compactness of the equipment, and reduce the weight of the equipment.

[0083] Furthermore, after the plasma 92 emitted light is reflected by the dichroic mirror 4 to the double lens group, the double lens group can converge the plasma 92 spectral signal with wavelengths of 230~800nm, reduce color difference, and facilitate the balance between the ultraviolet-visible-infrared (UV-VIS-IR) three-band spectra.

[0084] refer to Figure 1 The dual-lens group includes a biconvex lens 71 and a biconcave lens 72. The biconvex lens 71 is a positive focal length lens, located downstream of the optical path of the dichroic mirror 4; the biconcave lens 72 is a negative focal length lens, located downstream of the optical path of the biconvex lens 71. The biconvex lens 71 is made of calcium fluoride, and the biconcave lens 72 is made of fused silica. The focal lengths of the biconvex lens 71 and the biconcave lens 72 can be optimized according to the detection wavelength range of the spectrometer 6 to reduce chromatic aberration in imaging.

[0085] The emitted light from plasma 92 first enters the biconvex lens 71, and then enters the biconcave lens 72. The focal length of the biconvex lens 71 can be 25.0 mm, and the focal length of the biconcave lens 72 can be -50.0 mm. The combined equivalent focal length of the two lens groups is approximately 35 mm.

[0086] For example, if the equivalent focal length is f3, the focal length of the biconvex lens 71 is f1, the focal length of the biconcave lens 72 is f2, and the distance between the two lenses is t, then we have 1 / f3 = 1 / f1 + 1 / f2 - t / (f1 × f2).

[0087] It is understood that materials have different refractive indices for different wavelengths of light, i.e., dispersion exists. Therefore, this invention reduces the dispersion effect by combining positive and negative lenses made of materials with different refractive indices.

[0088] Further, refer to Figure 1 The fiber optic mechanism includes: fiber 10 and fiber optic adjustment bracket 11; plasma 92, as a light emitter, forms an image on the collecting optical axis after passing through two lenses. The input end of fiber 10 overlaps with the plasma image, and the light intensity from different parts of the plasma image is coupled into the three optical modules of spectrometer 6 through three optical splitting fibers. Spectrometer 6 records the emission spectra of plasma 92 in different bands.

[0089] The spectrometer 6 includes: an ultraviolet light module, a visible light module, and an infrared light module;

[0090] The ultraviolet light module is used to record spectra in the wavelength range of 230~350nm;

[0091] The visible light module is used to record spectra in the wavelength range of 340~505nm;

[0092] The infrared light module is used to record the spectrum with a wavelength range of 495 - 800 nm.

[0093] The specific spectral ranges recorded by the ultraviolet light module, visible light module, and infrared light module can be adjusted according to application requirements and are not limited to the spectra within the above ranges.

[0094] The optical fiber 10 is a three - core split optical fiber jumper. The input end of the optical fiber 10 is installed on the optical fiber adjustment bracket 11, and the output ends (three split optical fibers) of the optical fiber 10 are respectively connected to the ultraviolet light module, visible light module, and infrared light module of the spectrometer 6; at the input end of the optical fiber 10, the three optical fibers are bundled together, and at the output end of the optical fiber 10, the three optical fibers are separated.

[0095] The optical fiber adjustment bracket 11 is located downstream of the optical path of the double - lens group. The optical fiber adjustment bracket 11 is used to adjust the input end of the optical fiber 10 onto the collection optical axis, so that the input end of the optical fiber 10 overlaps face - to - face with the plasma image; the optical fiber adjustment bracket 11 is also used to adjust the spatial position of the input end of the optical fiber 10 according to the plasma image. Among them, the optical fiber adjustment bracket 11 is fixed by a fixing component. In the coordinate system constructed with the fixing component as the origin, the optical fiber adjustment bracket 11 can be adjusted in the x - direction, y - direction, and z - direction. Specifically, the optical fiber adjustment bracket 11 can be adjusted by threading in the x - direction and y - direction, and can be adjusted by sliding in the cage - type structure in the z - direction.

[0096] The optical fiber 10 includes an ultraviolet - band optical fiber, a visible - band optical fiber, and an infrared - band optical fiber; when the input end of the optical fiber 10 is installed on the optical fiber adjustment bracket 11, the ultraviolet - band optical fiber and the visible - band optical fiber are placed side by side in the upper row, and the infrared - band optical fiber is placed in the lower row adjacent to the upper row, and the infrared - band optical fiber is located below the contact position of the ultraviolet - band optical fiber and the visible - band optical fiber.

[0097] That is, the ultraviolet - band optical fiber, visible - band optical fiber, and infrared - band optical fiber are arranged in an inverted “pin” shape, with the ultraviolet - band optical fiber and the visible - band optical fiber placed side by side in one row and the infrared - band optical fiber placed in another row; the ultraviolet - band optical fiber and the visible - band optical fiber are located above the infrared - band optical fiber.

[0098] The core diameter of each single optical fiber in the ultraviolet - band optical fiber, visible - light - band optical fiber, and infrared - band optical fiber can be 300 microns, and the total light - passing diameter after the three single optical fibers are combined is 720 microns.

[0099] Specifically, this invention requires spatial positioning calibration of the ultraviolet (UV), visible, and infrared (IR) optical fibers at the three-core fiber optic inlet 12. During calibration, the position of each fiber relative to the plasma image is adjusted using the fiber adjustment bracket 11. For example, the UV and visible fibers are placed horizontally in the upper row, and the IR fiber is placed in the lower row. Vertical (x) adjustments can balance the UV and visible fibers relative to the IR band, horizontal (y) adjustments can balance the UV band relative to the visible band, and axial (z) adjustments can optimize the size matching between the fiber bundle and the plasma image, thereby optimizing the spectral balance of the UV, visible, and IR bands.

[0100] LIBS spectral acquisition was performed on a bauxite gravel sample. The spectrum before optimization of the three-band spectral balance (UV, VI, and IR) is as follows: Figure 2 As shown, the optimized spectrum after balancing the ultraviolet, visible, and infrared bands is as follows: Figure 3 As shown. From Figure 2 It can be seen that before equilibrium, the spectral intensity of the ultraviolet band is very high (peak value of about 42,000), far exceeding the spectral intensity of the visible and infrared bands (lowest value of only 5,000).

[0101] After balancing, you can refer to Figure 3 The spectral intensity of the ultraviolet band is reduced, with a peak intensity of about 19,000. The peak intensity of the visible band is about 15,000, and the peak intensity of the infrared band is about 7,500. The difference between the spectral intensities of the three bands is reduced, which avoids signal saturation or loss and improves the collaborative analysis capability of multi-band data. The spectral intensities of each band are coordinated, making it easier for multivariate analysis and feature extraction.

[0102] In addition, for the ultraviolet and visible bands, besides containing useful spectral signals (the spectra corresponding to elements), there are also continuous spectral signals (meaningless spectral signals because they do not contain element information). The presence of these continuous spectra will occupy the dynamic range of the CCD detection in the spectrometer 6. For example, the dynamic detection range of the CCD in the spectrometer 6 is 0~65000, but if the continuous spectrum occupies 0~35000, the dynamic detection range of the effective spectrum will be compressed to the interval of 35000~65000, causing spectral lines with an intensity above 30000 to saturate.

[0103] Since plasma 92 is a non-uniform light emitter, meaning that the continuous spectrum will be emitted at specific locations in plasma 92, this invention utilizes the spatial resolution method to minimize the continuous spectrum in the ultraviolet band. That is, the position of the ultraviolet band fiber is adjusted by adjusting the corresponding screws on the fiber adjustment bracket 11, thereby reducing the intensity of the continuous spectrum in the ultraviolet band. This allows for full utilization of the detection range of the CCD in the spectrometer 6 to optimize the detection of the effective spectral signal.

[0104] One sample of bauxite gravel underwent LIBS spectral acquisition. The spectrum before continuous spectrum compression was analyzed using the spatial resolution method, as shown below. Figure 4 As shown, the spectrum after continuous spectrum compression using the spatial resolution method is as follows: Figure 5 As shown. From Figure 4 It can be seen that the continuous spectral intensity near 240 nm in the spectrum can be as high as 50,000, which causes the spectral line to be raised and saturated. Figure 5 In the spectrum, the continuous spectral intensity in the same band (240nm) drops to 28000, and the spectral saturation phenomenon disappears.

[0105] The above-mentioned adjustment of the fiber position not only ensures efficient coupling of the spectral signal into the fiber 10, but also suppresses the continuous spectrum in the spectral signal, preventing invalid signals from occupying the dynamic detection range of the CCD in the spectrometer 6.

[0106] The optical fiber 10 transmits the spectral signals from different parts of the plasma 92 detected by the three-core split optical fiber inlet 12 to the three modules of the spectrometer 6, respectively. The spectrometer 6 can record the emission spectra of the plasma 92 in different bands.

[0107] The spectrometer 6 can transmit the spectra of plasma 92 at different wavelengths to the industrial control computer 13, which is located inside the probe box 1. The industrial control computer 13 analyzes the spectra of plasma 92 and stores the analysis results in real time; the analysis results include the predicted content of each element. (Reference) Figure 1 An industrial control computer 13 is installed on one side of the spectrometer 6. The industrial control computer 13 is also used to control the operation of the entire LIBS system, including triggering the laser 2 and recording data from the spectrometer 6.

[0108] In addition, the device also includes: a first water-cooled heat sink 14 and a second water-cooled heat sink 15. The first water-cooled heat sink 14 is in contact with one side of the industrial control computer 13 and is used to dissipate heat from the industrial control computer 13.

[0109] The second water-cooled heat sink 15 contacts one side of the laser 2 and is used to dissipate heat from the laser 2. Specifically, water circulation removes the heat generated by the laser 2 during operation, ensuring that the laser 2 operates stably at a suitable temperature.

[0110] The equipment also includes a dust removal and drying cold air inlet 16, which is located on the other side of the probe box 1. The dust removal and drying cold air inlet 16 is used to introduce dust removal and drying cold air into the probe box 1 to keep the laser 2 and the industrial control computer 13 clean, prevent dust accumulation from affecting the optical path, and at the same time play a role in heat dissipation.

[0111] Cooling water inlet 17 is located on the other side of probe box 1, and is located on one side of dust removal and drying cold air inlet 16;

[0112] Cooling water outlet 18 is located on the other side of probe box 1, and cooling water outlet 18 is located on the side of cooling water inlet 17;

[0113] The electrical signal inlet / outlet 19 is located on one side of the cooling water outlet 18 and is used to transmit various electrical signals, such as control signals, feedback signals, and data signals, to realize communication and collaborative work between various components.

[0114] The power supply 20 is located inside the probe box 1 and is placed on the other side of the laser 2. The power supply 20 is used to provide power to the industrial control computer 13, the laser 2 and the photodiode 5.

[0115] Cooling water inlet 17 and cooling water outlet 18 are connected to the water cooling system, providing cooling water circulation channels for the first water-cooled heat sink 14 and the second water-cooled heat sink 15.

[0116] The beneficial effects of the probe-type multi-element laser-induced breakdown spectroscopy detection device for minerals provided by this invention are at least as follows:

[0117] 1. A quartz crescent-shaped focusing lens is used to directly focus the laser pulse. Since the convex surface of the quartz crescent-shaped focusing lens faces the incident direction of the laser pulse, the reflected light is diverged. The focal point of the reflected light can be pushed far behind the laser, avoiding the focal point falling inside the laser and damaging the optical components. In addition, by directly using the quartz crescent-shaped focusing lens, there is no need to use a high-reflection mirror to deflect the light or a beam expander to expand the diameter of the laser beam. This can minimize the number of optical components, shorten the optical path, improve the compactness of the equipment, and reduce the weight of the equipment.

[0118] 2. Using a combination of convex and concave lenses made of different optical materials to converge the plasma emitted light reduces imaging chromatic aberration and is beneficial to the spectral balance among the ultraviolet, visible and infrared bands.

[0119] 3. Using fiber optic adjustment brackets, the spatial positions of the three optical fibers are calibrated. The balance of the ultraviolet and visible bands relative to the infrared band is adjusted vertically, and the balance of the ultraviolet band relative to the visible band is adjusted horizontally. This optimizes the spectral balance of the three bands (ultraviolet, visible, and infrared). Through spatially resolved detection, the continuous spectrum of the ultraviolet and visible bands is suppressed. The dynamic detection range of the CCD in the spectrometer is fully utilized to optimize the detection of effective spectral signals and avoid invalid signals.

[0120] 4. The industrial control computer is built into the probe box to avoid signal interference over long distances, optimize the control of core equipment components, realize local data processing and caching, and reduce network transmission traffic pressure.

[0121] Based on the same inventive concept as the foregoing embodiments, the present invention also provides a probe-type multi-element laser-induced breakdown spectroscopy detection system for minerals, such as... Figure 6 As shown, the system includes:

[0122] Water supply equipment 61, gas supply equipment 62, control cabinet 63, and the probe-type mineral multi-element laser-induced breakdown spectroscopy detection equipment 64 mentioned above;

[0123] The water supply equipment 61 includes a water tank and a temperature-controlled water chiller; the gas supply equipment 62 includes an air compressor and a refrigerated dryer. After filtering the raw gas in the application environment, the air compressor compresses the filtered gas, and the refrigerated dryer dries the compressed air to reduce the moisture content. The air valve at the dust removal and drying cold air inlet 16 delivers the treated gas to various components in the probe box 1 (such as the laser 2, industrial control computer 13, etc.) to ensure that the internal temperature, humidity and cleanliness of the probe are maintained within the range required by the equipment.

[0124] An external water tank provides the water source required for recycling. After the temperature-controlled water chiller adjusts the water source temperature, it delivers the cold water required for cooling the laser 2 and the industrial control computer 13 to the first water-cooled heat sink 14 and the second water-cooled heat sink 15 through the cooling water inlet 17, ensuring that the laser 2 and the industrial control computer 13 operate within the specified operating temperature range.

[0125] The control cabinet 63 is equipped with an AC-DC converter connected to a 220V power supply. It is used to convert AC power into stable DC power required by the probe-type mineral multi-element laser-induced breakdown spectroscopy detection device 64 and deliver it to the power supply 20 (DC power supply) in the probe box 1.

[0126] The control cabinet 63 is also equipped with a controller that connects to the water supply equipment 61 and the gas supply equipment 62. The controller is used to control the water supply equipment 61 and the gas supply equipment 62 respectively (such as controlling the gas flow rate and water flow rate) so that the probe-type mineral multi-element laser-induced breakdown spectroscopy detection equipment 64 generates a laboratory-like environment atmosphere.

[0127] The control cabinet 63 is also equipped with an Ethernet adapter, which connects to the communication network at the application site and provides an Internet interface for the industrial control computer 13. The industrial control computer 13 can remotely control the equipment, read the emission spectrum of the plasma transmitted by the spectrometer 6, analyze the emission spectrum of the plasma, and output the predicted content of each element.

[0128] Example 1

[0129] Using the probe-type multi-element laser-induced breakdown spectroscopy detection equipment and system for minerals provided in the above embodiments, LIBS spectra were acquired from 90 samples of bauxite gravel. Figure 2 and Figure 3 The comparison results show the spectra of one sample before and after the balance optimization of the three bands (UV, VI, and IR). Figure 4 and Figure 5 The comparison results of the spectrum of one sample before and after spatially resolved continuous spectrum compression are shown. Figures 7-9 The performance of multivariate regression models for Al2O3, SiO2, and Fe2O3 elements was tested using 75 bauxite crushed stone samples for training and 15 independent bauxite crushed stone samples for testing. The multivariate regression models were trained based on convolutional neural networks.

[0130] Figure 7 , Figure 8 and Figure 9 The circles in the diagram represent training data points, and the crosses represent test data points. "" represents the linear fit of the training data points, and the R-squared value of the fit is... 2 The values ​​were 0.9944 (Al2O3), 0.9951 (SiO2), and 0.9975 (Fe2O3), respectively. "Represents a 1:1 line," "Represents ±5% measurement relative error line." Figure 7 This is the result of predicting the Al2O3 element content. Figure 8 This is the result of predicting the SiO2 element content. Figure 9 This is the result of predicting the Fe2O3 element content. Figures 7 to 9 In this context, "wt" stands for weight and "wt%" stands for mass percentage.

[0131] by Figure 7 For example, Figure 7 The R-squared value for linear fitting is given in the figure. 2 The value is 0.9944, R 2 The closer the value is to 1, the better the model fits the data.

[0132] Closeness to the 1:1 line: The 1:1 line indicates that the predicted content value is exactly equal to the reference content value. The closer the training data points (circles) and test data points (crosses) are to this line, the closer the predicted content value is to the reference content value, and the better the prediction effect. From Figure 7 In the middle, most data points are closely clustered around the 1:1 line, indicating that the model prediction is relatively accurate.

[0133] Relationship with ±5% relative measurement error line: The ±5% relative measurement error line defines an error range. If most data points fall within the ±5% relative measurement error line, it means that the error between the predicted content and the reference content is within an acceptable ±5% range, indicating that the model's prediction accuracy is high. Figure 7 Most data points are within ±5% of the relative measurement error line, reflecting good model prediction accuracy.

[0134] Similarly, Figure 8 and Figure 9 The prediction results also reflect that the model has good prediction accuracy.

[0135] Through one or more embodiments of the present invention, the present invention has the following beneficial effects or advantages:

[0136] This invention provides a probe-type multi-element laser-induced breakdown spectroscopy detection device for minerals, comprising: a probe box, a laser, a quartz crescent-shaped focusing lens, a dichroic mirror, a dual-lens group, an optical fiber mechanism, and a spectrometer; a sealed quartz optical window is provided on one side of the probe box; the laser is installed inside the probe box, facing the mineral to be detected, and emits laser pulses through the sealed quartz optical window; the emission optical axis of the laser passes through the dichroic mirror, the quartz crescent-shaped focusing lens, and the sealed quartz optical window, and is perpendicularly pointed to the contour surface of the mineral to be detected; A quartz crescent-shaped focusing lens is located between the laser and the sealed quartz optical window. The convex surface of the quartz crescent-shaped focusing lens faces the laser, and the concave surface faces the sealed quartz optical window. The quartz crescent-shaped focusing lens is used to focus the laser pulse emitted by the laser onto the surface of the mineral being tested, generating plasma. A dichroic mirror is located between the laser and the quartz crescent-shaped focusing lens. The dichroic mirror is positioned on the emission optical axis of the laser and is used to reflect the emitted light from the plasma to the dual-lens group. The dual-lens group... The mirror group is located on one side of the dichroic mirror, and the double lens group is located on the collecting optical axis perpendicular to the emission optical axis. The double lens group is used to converge the emitted light of the plasma reflected by the dichroic mirror to form a plasma image on the collecting optical axis. The plasma image is coupled to the spectrometer via an optical fiber mechanism. The spectrometer is used to detect the spectrum of the plasma image to obtain the emission spectrum of the plasma in different wavelength bands. In this way, a quartz crescent-shaped focusing lens can be used to focus the laser pulse, and since the convex surface of the quartz crescent-shaped lens faces the laser pulse... The laser pulse is reflected and diffused by the quartz crescent-shaped focusing lens, which pushes the focal point of the reflected light further away from the laser, preventing the focal point from falling inside the laser and damaging the optical components. In addition, with the crescent lens, there is no need to use a high-reflection mirror to deflect the light or a beam expander to extend the diameter of the laser beam. This shortens the optical path, improves the compactness of the equipment, and reduces its weight. The fiber optic structure, through spatial resolution, can balance the spectral intensity of different bands and suppress the continuous spectrum, thereby simultaneously optimizing the spectral intensity of different spectral channels and improving the accuracy of elemental content prediction.

Claims

1. A probe-type multi-element laser-induced breakdown spectroscopy detection device for minerals, characterized in that, The device includes: a probe box, a laser, a quartz crescent focusing lens, a dichroic mirror, a dual lens group, an optical fiber mechanism, and a spectrometer; A sealed quartz optical window is provided on one side of the probe box; The laser is installed inside the probe box, facing the mineral being detected, and emits laser pulses through the sealed quartz optical window; the emission optical axis of the laser passes through the dichroic mirror, the quartz crescent focusing lens, and the sealed quartz optical window, and is perpendicularly pointed to the contour surface of the mineral being detected. The quartz crescent focusing lens is located between the laser and the sealed quartz optical window. The convex surface of the quartz crescent focusing lens faces the laser, and the concave surface of the quartz crescent focusing lens faces the sealed quartz optical window. The quartz crescent focusing lens is used to focus the laser pulse emitted by the laser onto the surface of the mineral being detected to generate plasma. The dichroic mirror is located between the laser and the quartz crescent focusing lens, and is positioned on the emission optical axis of the laser to reflect the emitted light of the plasma to the dual lens group. The dual-lens group is located on one side of the dichroic mirror and on the collecting optical axis perpendicular to the emission optical axis. The dual-lens group is used to converge the emitted light of the plasma reflected by the dichroic mirror to form a plasma image on the collecting optical axis. The plasma image is coupled to the spectrometer through the optical fiber mechanism. The spectrometer is used to perform spectral detection on the plasma image and record the emission spectra of the plasma in different spectral bands; The spectrometer includes: an ultraviolet light module, a visible light module, and an infrared light module; The optical fiber mechanism includes: an optical fiber and an optical fiber adjustment bracket; The optical fiber is a three-core split fiber patch cord, with the input end mounted on the fiber adjustment bracket and the output end connected to the ultraviolet light module, visible light module and infrared light module of the spectrometer, respectively. A fiber optic adjustment bracket, located downstream of the optical path of the dual-lens group, is used to adjust the fiber input end to be aligned with the collecting optical axis, so that the fiber input end overlaps face-to-face with the plasma image. The fiber optic adjustment bracket is also used to adjust the spatial position of the fiber input end according to the plasma image. The fiber optic adjustment bracket is fixed by a fixing component, and in a coordinate system constructed with the fixing component as the origin, the fiber optic adjustment bracket can be adjusted in the x, y, and z directions.

2. The device as described in claim 1, characterized in that, The device also includes: An industrial control computer, located inside the probe box, is used to read the emission spectrum of the plasma transmitted by the spectrometer and analyze the emission spectrum of the plasma.

3. The device as described in claim 1, characterized in that, The ultraviolet light module is used to record spectra with a wavelength range of 230~350nm; The visible light module is used to record spectra with wavelengths ranging from 340 to 505 nm; The infrared light module is used to record spectra with wavelengths ranging from 495 to 800 nm.

4. The device as described in claim 1, characterized in that, The optical fibers include: ultraviolet band optical fibers, visible band optical fibers, and infrared band optical fibers; When the input end of the optical fiber is installed on the optical fiber adjustment bracket, the ultraviolet band optical fiber and the visible band optical fiber are placed side by side in the upper row, and the infrared band optical fiber is placed in the lower row adjacent to the upper row. The infrared band optical fiber is located below the contact position of the ultraviolet band optical fiber and the visible band optical fiber.

5. The device as described in claim 1, characterized in that, The dual-lens group includes: a biconvex lens and a biconcave lens; The biconvex lens is a positive focal length lens, located downstream of the optical path of the dichroic mirror; the biconcave lens is a negative focal length lens, located downstream of the optical path of the biconvex lens; the biconvex lens is made of calcium fluoride, and the biconcave lens is made of fused silica. The surface radius of curvature, focal length, surface radius of curvature, and focal length of the biconvex lens can be combined according to the detection wavelength range of the spectrometer.

6. The device as described in claim 2, characterized in that, The device also includes: The first water-cooled heat dissipation plate is in contact with one side of the industrial control computer and is used to dissipate heat from the industrial control computer.

7. The device as described in claim 1, characterized in that, The device also includes: A photodiode, located on the other side of the dichroic mirror, is positioned on a collecting optical axis perpendicular to the emitting optical axis. It is used to receive a small portion of the laser pulses and determine the energy of the laser pulses based on this small portion.

8. The device as described in claim 1, characterized in that, The device further includes a second water-cooled heat sink, which is in contact with one side of the laser and is used to dissipate heat from the laser.

9. The device as described in claim 1, characterized in that, The device also includes: The dust removal and drying cold air inlet is located on the other side of the probe box; The cooling water inlet is located on one side of the dust removal and drying cold air inlet; The cooling water outlet is located on one side of the cooling water inlet; The electrical signal inlet and outlet are located on one side of the cooling water outlet; The power supply, located inside the probe housing, provides power to the laser, industrial control computer, and photodiode.

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