Optical detection device and soil element detector

Abstract

The utility model relates to the technical field of rapid element detection, and provides an optical detection device and a soil element detector, and the device comprises a laser beam expanding and collimating system which is used for performing beam expanding and collimating on laser emitted by a laser and then inputting the laser into a multiplexing folding light path system; the multiplexing folding light path system carries out light beam folding on the laser subjected to beam expansion and collimation to obtain folding system emergent laser, and the folding system emergent laser is input into the surface scanning light path system; the surface scanning light path system focuses laser emitted by the folding system on a surface scanning target surface window to generate plasma; the spectral signal acquisition light path system acquires signal light radiated by the plasma; and the imaging system is used for imaging the window of the surface scanning target surface window on the CMOS camera. According to the device, through the design of a multi-stage optical system, the functions of laser beam expansion, collimation, folding, focusing, signal acquisition and the like are modularized, all the modules are independently optimized to improve the stability of the whole device, the stability of data is improved, rapid and accurate scanning type detection on a to-be-detected surface is achieved, and the anti-disturbance capability is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to element quick detection technical field especially, relate to an optical detection device and soil element detector. BACKGROUND

[0002] Portable laser-induced breakdown spectroscopy technology is also called portable LIBS (Laser Induced Breakdown Spectroscopy, LIBS) technology or portable laser probe technology, which is an integrated and miniaturized LIBS technology gradually derived in the continuous development of traditional LIBS technology. The principle of LIBS technology is to focus high-energy-density laser pulses on the surface of the measured sample target material, thereby ablation excitation to generate plasma. In the process of laser-induced plasma cooling and expansion, the optical collection system, spectrometer and detector are used to collect the spectrum generated by the plasma radiation, and then the types and content information of each element contained in the measured sample are obtained by analyzing these spectrum signals.

[0003] Portable LIBS soil element detection instrument has broad application space in the soil element detection industry, greatly shortens the detection period, and effectively promotes the rapid development of smart agriculture (big data control).

[0004] However, the currently launched portable LIBS soil element detection instrument has poor anti-disturbance ability in actual application and is greatly affected by environmental factors. UTILITY MODEL CONTENTS

[0005] The utility model provides a kind of optical detection device and soil element detector, to solve the defect that the currently launched portable LIBS soil element detection instrument has poor anti-disturbance ability in actual application and is greatly affected by environmental factors in prior art.

[0006] The utility model provides an optical detection device, including laser beam expanding collimation system, multiplexing folding optical path system, imaging system, surface scanning optical path system, spectrum signal acquisition optical path system;

[0007] Laser beam expanding collimation system inputs multiplexing folding optical path system after the laser emitted by the laser is expanded and collimated;

[0008] The multiplexing folding optical path system folds the laser after expansion and collimation, obtains folding system exit laser, and inputs folding system exit laser into surface scanning optical path system;

[0009] The surface scanning optical path system focuses folding system exit laser on surface scanning target surface window to generate plasma;

[0010] The spectrum signal acquisition light path system acquires signal light radiated by the plasma;

[0011] The imaging system images the window of the surface scanning target surface window on a CMOS camera.

[0012] According to the optical detection device, the variable diaphragm, the plano-concave lens and the first plano-convex lens are sequentially arranged along the incident direction of the incident laser light.

[0013] The variable diaphragm adjusts the energy of the laser light.

[0014] The plano-concave lens and the first plano-convex lens perform beam expansion and collimation on the adjusted laser light.

[0015] According to the optical detection device, the multiplexing folded light path system comprises a half-inch laser line reflector, a dichroic mirror and a one-inch laser line reflector.

[0016] The half-inch laser line reflector horizontally transmits the beam expanded and collimated laser light.

[0017] The lens of the dichroic mirror reflects laser light and transmits visible light, and the transmitted visible light comprises illumination light and imaging light.

[0018] The one-inch laser line reflector performs beam folding on the beam expanded and collimated laser light to obtain folded system exit laser light.

[0019] According to the optical detection device, the surface scanning light path system sequentially comprises a laser scanning galvanometer assembly, a second plano-convex lens, a third plano-convex lens and a surface scanning target surface window along the incident direction of the incident laser light.

[0020] A focusing lens group performs laser surface scanning on the surface scanning target surface window, and the focusing lens group comprises the second plano-convex lens and the third plano-convex lens.

[0021] The surface scanning target surface window is installed with quartz glass, the scanning target surface is a square target surface, and the size of the square target surface is adjustable.

[0022] According to the optical detection device, the imaging system sequentially comprises a field of view illumination light source, a first lenticular lens, a beam splitter, a second lenticular lens and a CMOS camera along the incident direction of the incident laser light.

[0023] The field of view illumination light source generates light for illuminating the surface scanning target surface window, and the field of view illumination light source controls the illumination time through a circuit switch.

[0024] The first lenticular lens changes the light emitted by the field of view illumination light source into parallel light.

[0025] The beam splitter reflects the parallel light into the multiplexing folded optical path system;

[0026] The second lenticular lens collects the imaging light of the surface scanning target surface window;

[0027] The CMOS camera displays the imaging light.

[0028] According to the optical detection device, the spectrum signal collection optical path system comprises a fourth plano-convex lens and an off-axis parabolic mirror;

[0029] The surface scanning target surface window is between the focal point of the fourth plano-convex lens and the fourth plano-convex lens, and all signal lights radiated by the plasmas between the focal point and the edge light of the fourth plano-convex lens are collected;

[0030] The off-axis parabolic mirror collects the signal light.

[0031] The utility model also provides a soil element detector, including above-mentioned optical detection device.

[0032] According to the soil element detector provided by the utility model, it is characterized in that, further include laser instrument, spectrometer, embedded main control board and sensor;

[0033] The laser emits laser;

[0034] The optical detection device produces plasma through the laser ablation of the detection surface scanning of different detection depth soil, and collects the signal light radiated by the plasma;

[0035] The spectrometer converts the spectrum signal obtained by the signal light into spectrum data;

[0036] The sensor collects the position information and environmental information of soil;

[0037] The embedded main control board is connected with the spectrometer and the sensor respectively, and is used for displaying the position information and the environmental information, and the soil element component and soil element content corresponding to the spectrum data.

[0038] The optical detection device and the soil element detector provided by the utility model have the advantages that the laser beam emitted by the laser is expanded and collimated by the laser beam expansion and collimation system, and then input into the multiplexing and folding optical path system, the laser beam expanded and collimated is folded by the multiplexing and folding optical path system, the folded laser beam is input into the area scanning optical path system, the folded laser beam is focused on the area scanning target window to generate plasma, the signal light radiated by the plasma is collected by the spectrum signal collection optical path system, and the window of the area scanning target window is imaged on the CMOS camera by the imaging system. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical scheme in the utility model or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or the prior art description, and obviously, the drawings in the following description are some embodiments of the utility model, and for those skilled in the art, other drawings can also be obtained according to these drawings without creative labor.

[0040] Figure 1 It is the structural schematic diagram of the optical detection device provided by the utility model.

[0041] Figure 2 It is the structural schematic diagram of the optical system installation cavity in the soil element detector provided by the utility model.

[0042] Figure 3 It is the schematic diagram of the multiplexing and folding optical path system provided by the utility model.

[0043] Figure 4 It is the schematic diagram of the area scanning optical path system provided by the utility model.

[0044] Figure 5 It is the area scanning light focusing light spot simulation diagram provided by the utility model.

[0045] Figure 6 It is the schematic diagram of the spectrum signal collection optical path system provided by the utility model.

[0046] Figure 7 It is the signal light focusing light spot simulation diagram provided by the utility model.

[0047] Figure 8 It is the schematic diagram of the imaging system provided by the utility model.

[0048] Figure 9 is one of the external structure schematic diagram of the soil element detector provided by the utility model.

[0049] Figure 10 is one of the flow schematic diagram of the soil element detection method provided by the utility model.

[0050] Figure 11 is the working flow chart of the soil element detector provided by the utility model.

[0051] Figure 12 is the working mode diagram of the galvanometer assembly provided by the utility model.

[0052] Figure 13 is the second flow schematic diagram of the soil element detection method provided by the utility model.

[0053] Figure 14 is the industrial control schematic diagram of the soil element detector provided by the utility model.

[0054] Figure 15 is the spectrum diagram of the soil element detector for soil detection provided by the utility model.

[0055] Figure 16 is the fitting curve diagram of the spectrum intensity and the drilling speed of the soil element detector provided by the utility model using the two detection methods of fixed point detection and drilling detection.

[0056] Figure 17 is the intensity comparison diagram of the Al element characteristic spectrum line of the soil element detector provided by the utility model using the two detection methods of fixed point detection and drilling detection. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical scheme and advantages of the utility model more clear, the technical scheme in the utility model will be described clearly and completely below by combining with the drawings in the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all the other embodiments obtained by the ordinary skilled in the art without creative labor belong to the protection scope of the utility model.

[0058] In the related art, the LIBS technology has been widely applied in soil analysis, environmental monitoring, industrial metallurgy, biological medicine, food safety and many other fields in recent years due to its advantages of fast analysis speed, simple sample preparation, micro-damage or even no damage, simultaneous detection of multiple elements and the like. The detection capability of the LIBS technology has been confirmed many times in a laboratory environment. However, the traditional LIBS system is large in size and high in power consumption, and cannot meet the needs of field operation and online detection in industrial production and sample characteristics diversification, limiting the flexibility and convenience of the system in practical application, and making it difficult to fully exert the advantages of in-situ and rapid detection. With the rapid development and continuous progress of instrument technology and computer technology, the size and power consumption of core devices such as lasers, spectrometers, optical systems and microcomputers are gradually reduced, so that the LIBS system gradually tends to be instrumental, professional and portable. The portable LIBS device has the advantages of small size, light weight and easy use, and has better applicability in industrial sites and harsh outdoor conditions. The portable LIBS technology is obviously different from the traditional benchtop LIBS technology in system composition, system performance and application characteristics, and generally has the characteristics of compact system components, easy movement of the whole machine, automation integration and integration of detection and analysis. According to the detection site requirements, the system composition is gradually simplified and efficient, and the system form gradually tends to diversification from singleness. According to the application requirements of the detection site, the system has gradually developed into a variety of styles such as a portable case, a backpack, a handheld device and a wearable device with greatly improved portability.

[0059] With the continuous advancement of urbanization and industrialization, people pay more and more attention to environmental detection, soil scientific research and agricultural production, and environmental problems such as soil heavy metal pollution are becoming increasingly prominent, so it is particularly important to establish a perfect soil element detection system. Under this background, the emergence of portable LIBS element detection instruments provides convenience for rapid and accurate detection of soil element content information. Although portable LIBS equipment has been widely used in coal, mining, metallurgy and other fields and has been reported a lot, most of the reports on soil element detection are still based on soil sample collection and laboratory detection, and there are relatively few reports on soil element detection in the operation site.

[0060] The portable LIBS soil element detection instrument has a wide application space in the soil element detection industry, greatly shortens the detection period and effectively promotes the rapid development of smart agriculture (big data control). However, the currently launched portable LIBS soil element detection instrument is greatly affected by environmental factors in practical application: the portable LIBS soil element detection instrument is affected by environmental conditions: temperature, humidity and soil texture conditions will affect the performance, and the operator needs to use it in a controlled environment to ensure accuracy.

[0061] Based on the above problems, the utility model provides an optical detection device,Figure 1 is a structural schematic view of an optical detection device provided by the utility model, Figure 2 is a structural schematic view of an optical system mounting cavity in a soil element detector provided by the utility model, as shown in Figure 1 、 Figure 2 The optical detection device 40 comprises a laser beam expanding and collimating system 10, a multiplexing and folding optical path system 11, an imaging system 12, a surface scanning optical path system 13 and a spectral signal acquisition optical path system 14.

[0062] The laser beam expanding and collimating system 10 inputs the laser emitted by the laser 9 after expanding and collimating the laser.

[0063] The multiplexing and folding optical path system 11 folds the laser after expanding and collimating the laser, obtains folded system exit laser and inputs the folded system exit laser into the surface scanning optical path system 13.

[0064] The surface scanning optical path system 13 focuses the folded system exit laser onto a surface scanning target window to generate plasma.

[0065] The spectral signal acquisition optical path system 14 acquires signal light radiated by the plasma.

[0066] The imaging system 12 images the window of the surface scanning target window on a CMOS camera.

[0067] Specifically, the laser beam expanding and collimating system 10 inputs the multiplexing and folding optical path system 11 after expanding and collimating the laser emitted by the laser 9.

[0068] As shown in Figure 2 The laser beam expanding and collimating system 10 comprises a variable diaphragm 22, a plano-concave lens 23 and a first plano-convex lens 24, wherein the variable diaphragm 22 adjusts the energy size of the laser by changing the size of the light aperture, and by adjusting the energy size of the laser, the weak spectral signal caused by too small laser energy and the spectral signal oversaturation caused by too large laser energy are avoided.

[0069] The plano-concave lens 23 and the first plano-convex lens 24 jointly realize the expansion and collimation of the laser (reduce the divergence angle of the laser beam, facilitate long-distance transmission of the laser and improve the focusing quality of the laser).

[0070] The multiplexing and folding optical path system 11 is used for folding the laser after expanding and collimating the laser to compress the optical path volume, obtaining folded system exit laser and inputting the folded system exit laser into the surface scanning optical path system 13.

[0071] Figure 3 is a schematic view of a multiplexing and folding optical path system provided by the utility model, as shown in Figure 3As shown, the multiplexed folded optical path system 11 includes a half-inch laser line mirror 25, a dichroic mirror 26, and a one-inch laser line mirror 27.

[0072] The optical path system has two main functions: the first function is to achieve coaxial transmission of three beams of laser scanning focusing light, target surface illumination light, and target surface imaging light; the second function is beam folding, which compresses the volume of the overall optical path system. Among them, the half-inch laser line mirror 25 is installed at a 45-degree angle with the horizontal plane, so that the expanded and collimated laser is transmitted horizontally. The dichroic mirror 26 is installed at a 45-degree angle with the horizontal plane, and is connected to the imaging system (illumination and CMOS imaging multiplexing optical path system) 12 above. The dichroic mirror 26 can reflect laser and transmit visible light, and here, the transmitted visible light includes illumination light and imaging light.

[0073] It should be noted that the imaging system 12 also includes a CMOS camera 21.

[0074] The one-inch laser line mirror 27 is installed at a 60-degree angle with the horizontal plane, and is used to fold the expanded and collimated laser beam to compress the volume of the optical path, obtain the folded system exit laser, and input the folded system exit laser into the area scanning optical path system 13.

[0075] Here, the main function of the area scanning optical path system 13 is to realize the area scanning of the laser, which is used to focus the folded system exit laser onto the area scanning target window to generate plasma.

[0076] Figure 4 is a schematic view of the area scanning optical path system provided by the utility model, Figure 5 is an area scanning optical path focusing spot simulation diagram provided by the utility model, like Figure 4 、 Figure 5 As shown, the area scanning optical path system 13 includes a laser scanning galvanometer assembly 28, a second plano-convex lens 29, a third plano-convex lens 30, and an area scanning target window 31.

[0077] Among them, the laser scanning galvanometer assembly 28 is installed at a 70-degree angle with the horizontal plane (initial angle), and the angle change of the galvanometer in the laser scanning galvanometer assembly is realized through the embedded main control board 16.

[0078] The second plano-convex lens 29 and the third plano-convex lens 30 realize laser area scanning through the focusing lens group, so as to realize the focusing of the laser and the position compensation of the focusing point.

[0079] The area scanning target window 31 is installed with quartz glass, and the scanning target surface is a square target surface. The size of the square target surface can be adjusted and controlled, and the maximum target surface is a square target surface of 2cm*2cm. The area of the area scanning target window 31 will be larger than the actual scanning target surface area.

[0080] The surface scanning light path system 13 can be realized by a galvanometer, and the galvanometer includes a first detection mode and a second detection mode.

[0081] The second detection mode is a drilling scanning mode when the galvanometer is fixed, and is used for realizing drilling, that is, a detection mode of drilling while measuring.

[0082] Figure 6 is a schematic view of the spectrum signal acquisition light path system provided by the utility model, Figure 7 is a signal light focusing spot simulation diagram provided by the utility model, as shown in Figure 6 、 Figure 7 The spectrum signal acquisition light path system 14 is used for transmitting the collected signal light to the spectrometer 15 through an optical fiber, and the spectrum signal acquisition light path system 14 includes a fourth plano-convex lens 32 and an off-axis parabolic reflector 34.

[0083] The fourth plano-convex lens 32 is used for collecting signal light, and the surface scanning target surface window 31 is located between the focal point 33 of the fourth plano-convex lens and the fourth plano-convex lens 32.

[0084] The off-axis parabolic reflector 34 transmits the collected signal light to the spectrometer 15 through an optical fiber.

[0085] Here, the illumination and CMOS imaging multiplexing light path system 12 is used for imaging the surface scanning target surface window 31 on the CMOS camera 21 and transmitting the imaging of the surface scanning target surface window 31 to the embedded main control board 16 to analyze whether there is foreign matter in the surface scanning target surface window 31.

[0086] Figure 8 is a schematic view of the imaging system provided by the utility model, as shown in Figure 8 The imaging system (illumination and CMOS imaging multiplexing light path system) multiplexing light path system 12 includes a beam splitter 17, a first double convex lens 18, a second double convex lens 19, a field of view illumination light source 20 and a CMOS camera 21.

[0087] The beam splitter 17 is installed at an angle of 45 degrees with the horizontal plane, and is used to reflect part of the light emitted by the field illumination light source 20 into the multiplexing folded light path system 11, while transmitting the imaging light of the face scanning target surface window 31 into the CMOS camera 21.

[0088] The first lenticular lens 18 is used to change the light emitted by the field illumination light source 20 into parallel light for long-distance transmission.

[0089] The second lenticular lens 19 is used to collect the imaging light of the face scanning target surface window 31.

[0090] The field illumination light source 20 is used to generate light to illuminate the face scanning target surface window 31, and the field illumination light source 20 controls the illumination time through a circuit switch. The CMOS camera 21 is used for imaging of the face scanning target surface window 31, for feedback of imaging information, and for transmission of the imaging of the face scanning target surface window 31 to the embedded host board 16 for analysis of whether there is foreign matter on the face scanning target surface window 31.

[0091] The optical detection device provided by the embodiment of the utility model, the laser beam expansion collimation system inputs the multiplexing folded light path system after expanding and collimating the laser emitted by the laser, the multiplexing folded light path system folds the light beam of the expanded and collimated laser, obtains the folded system exit laser, and inputs the folded system exit laser into the face scanning light path system, the face scanning light path system focuses the folded system exit laser on the face scanning target surface window to generate plasma, the spectrum signal acquisition light path system acquires the signal light radiated by the plasma, and the imaging system images the window of the face scanning target surface window on the CMOS camera. The device modularizes the functions such as expansion, collimation, folding, focusing and signal acquisition of the laser through the design of the multi-stage optical system, each module can be optimized independently to improve the stability of the whole device, thereby improving the stability of data, realizing the rapid and accurate scanning detection of the measured surface, and further improving the anti-disturbance capability.

[0092] In the related art, the portable LIBS soil element detection instrument has a wide application space in the soil element detection industry, greatly shortens the detection period, and effectively promotes the rapid development of smart agriculture (big data control). However, the currently released portable LIBS soil element detection instrument has some deficiencies in actual application, as follows:

[0093] (1) Complicated operation process, poor portability: the existing portable LIBS soil element detection instrument usually performs simple sample preparation on site, which cannot completely realize on-site measurement, increases the complexity of operation, and is easy to cause pollution and interference problems, affecting the accuracy of analysis results.

[0094] (2) The precision of the measured data is not high: the portable LIBS soil element detector instrument has a fixed ablation range, is easily affected by other impurities and equipment stability, etc., resulting in relatively less spectral data obtained, thereby affecting the precision and accuracy of the detection.

[0095] (3) Poor scalability: the existing portable LIBS technology has a relatively narrow detection range, is limited to small-scale local detection, and is difficult to meet the application requirements in a wide area, and lacks compatibility with other devices, which greatly limits its wide application in environmental monitoring, agricultural analysis, geological exploration and other fields.

[0096] Based on the above problems, the utility model provides a soil element detector, Figure 9 It is the external structure schematic view of the soil element detector provided by the utility model, as Figure 9 Indicated, the soil element detector includes an optical detection device 40, an optical system installation cavity including a laser 9, a spectrometer 15, an embedded main control board 16, and the optical detection device 40.

[0097] It should be noted that the multifunctional portable surface and shallow soil LIBS rapid detector in the utility model embodiment is a soil element detection device.

[0098] The external structure of the multifunctional portable surface and shallow soil LIBS rapid detector overall includes a force arm handle 1, a control panel 2, an extension rod 3, an electronic device installation cavity 4, a power supply 5, an optical system installation cavity 6, a sensor 7 and an auxiliary detection structure 8.

[0099] The internal structure of the multifunctional portable surface and shallow soil LIBS rapid detector includes a laser 9, a spectrometer 15, an embedded main control board 16, a sensor 7, an optical detection device 40 and a control panel 2. Among them, the drill-in button 35 is used for the auxiliary structure drill bit 8 to drill into the soil; the spin-out button 36 is used to start the auxiliary structure drill bit 8 to spin out of the soil; the detection button 37 is used to actually issue a start detection instruction; the power button 38 is a device switch, used for power on and power off of the entire device;

[0100] The above four buttons are used to simplify the operation process, so that the detection operation is more convenient.

[0101] In the drilling process (two detection modes), the user presses the drill button to start the measurement, and the system immediately records the time. As the drill bit gradually penetrates the soil, the user releases the button to end the measurement, and the system stops timing. The measurement time is calculated by the time points of pressing and releasing the button, representing the duration of the drill bit moving in the soil. This time data is accurately recorded, providing an important reference for subsequent depth and average speed calculation of the drill bit penetrating the soil, while the control panel program monitors and ensures the accuracy of the measurement time.

[0102] The external displacement sensor is placed at an angle, and the angle is set according to the area of the soil turned over during drilling. The angle is , the distance measured by the displacement sensor is , and the distance from the displacement sensor light signal output port to the center of the detection window is , then the depth of drilling into the soil is which can be calculated by the following formula:

[0103]

[0104] This process can directly calculate the depth of drilling into the soil through the program calculation. Combined with the required measurement time, the average speed of the drill bit descending can be further calculated. The average speed ( ) can be calculated by the following formula:

[0105]

[0106] Through the relationship between depth and time, the control panel built-in program calculates the average speed of the drill bit when drilling into the soil.

[0107] Finally, the program controls these calculations and directly displays the average speed information of the drill bit descending on the display screen of the device, providing real-time measurement results for the user.

[0108] Through the above process, the variable depth soil element detector can realize the function of drilling and measuring at the same time, accurately measuring the depth and average speed of the drill bit during drilling. The design of the control part ensures the stability and accuracy of the system, allowing users to easily obtain the required data and analyze it. This intelligent design greatly simplifies the operation process of soil element detection, improving the efficiency and accuracy of measurement.

[0109] Considering the limited longitudinal depth measurement range of soil, the existing portable LIBS soil element detector can only measure in the range of several hundred microns to several millimeters (i.e. the surface layer of soil), and there is almost no design of soil element detection equipment for different depths, or while considering soil detection at different depths, it can also ensure its detection accuracy, and most of them cannot penetrate into the soil, resulting in limitations in detecting the vertical distribution of elements in the soil, and cannot accurately measure uneven soil samples. Therefore, the portable LIBS rapid detector of the embodiment of the utility model increases the auxiliary detection structure 8.

[0110] In addition, the telescopic rod 3 can adjust the rod length according to the detection depth of the soil and the needs of the operator during measurement. It should be noted that the telescopic rod 3 and the auxiliary detection structure 8 are used to insert the detection instrument into the shallow surface layer (the deepest distance is 25 cm).

[0111] The sensor 7 is used to install and place environmental temperature and humidity sensors, displacement sensors, GPS positioning sensors and other sensor components. The position information and environmental information of the soil can be obtained through the sensor.

[0112] The detection depth of the auxiliary detection structure 8 is determined based on the displacement sensor, and the auxiliary detection structure can realize the function of drilling and measuring at the same time. It should be noted that it can replace the appropriate auxiliary detection structure at any time according to different soil texture environment, so as to ensure that the LIBS rapid detector can efficiently and accurately complete the drilling task. The portable LIBS rapid detector can be directly taken to the detection site, fully utilizes the in-situ analysis and rapid response capability of LIBS technology, and greatly improves the detection efficiency and flexibility.

[0113] It should be noted that the auxiliary detection structure 8 of the surface and shallow soil LIBS rapid detector integrated with the drilling function is matched with a small drill bit, which can drill into the shallow soil, so that the rapid detector can detect the surface layer of the soil and the shallow layer of the soil, so that the obtained soil detection data is more accurate and comprehensive. The maximum soil depth that can be detected is 25 cm, and the displacement sensor can be matched to realize real-time monitoring of the soil depth during detection.

[0114] The main part of the portable LIBS rapid detector is composed of a cylindrical outer structure, which can detect the vertical distribution of elements in the soil within the limited range under the cooperation of the auxiliary detection structure 8 (a soil drill bit with a damping device). The displacement sensor in the auxiliary detection structure 8 can transmit the real-time soil depth and component information to the user end.

[0115] The optical system mounting cavity includes a laser 9, a spectrometer 15, an embedded main control board 16, a sensor 7 and an optical detection device 40.

[0116] The laser 9 is used to emit laser light, and the laser light is used to scan the detection surface of the soil at different detection depths to generate plasma by ablation, and the signal light emitted by the plasma is collected and transmitted to the spectrometer through an optical fiber. The detection depth is determined based on the auxiliary detection structure, which can realize the function of drilling while measuring. Here, the optical detection device 40 includes a laser beam expansion and collimation system 10, a multiplexed folding optical path system 11, an illumination and CMOS imaging multiplexed optical path system 12, a surface scanning optical path system 13, and a spectral signal acquisition optical path system 14. It should be noted that the optical detection device 40 can maintain a stable structure and is convenient for installation and debugging.

[0117] Here, the wavelength of the laser light emitted by the laser 9 is 1064 nm, and the wavelength beam has the advantages of safety and no radiation, and the detection process does not involve the use, generation and discharge of other pollutants, reducing the risk to the operator and the environment. That is, compared with the traditional analysis method, the portable LIBS rapid detector is safer during operation.

[0118] The spectral signal acquisition optical path system 14 is connected with the spectrometer 15 using an optical fiber to transmit the optical signal.

[0119] The spectrometer 15 is used to convert the transmitted spectral signal into spectral data and send the spectral data to the embedded main control board. It can be understood that the spectral signal is converted into spectral data, thereby enhancing the intuitiveness, and in addition, the spectral data is easier to perform qualitative and quantitative analysis compared with the original spectral signal. Researchers can identify the composition difference, concentration change or structure change between samples by comparing the differences between different spectral data. Further, the spectral data can also be matched with a known spectral database to quickly determine the composition of unknown samples.

[0120] The sensor 7 is used to collect the position information and environmental information of the soil and send the position information and environmental information to the embedded main control board 16.

[0121] The sensor 7 includes an environmental temperature and humidity sensor, a displacement sensor and a GPS sensor, the displacement sensor and the GPS sensor are used to collect the position information of the soil, and the environmental temperature and humidity sensor is used to collect the environmental information.

[0122] It can be understood that the sensor 7 includes an environmental temperature and humidity sensor, a displacement sensor and a GPS sensor, thereby improving the accuracy and reliability of the position information and environmental information.

[0123] The embedded main control board 16 sends the spectral data, position information and environment information to the control panel, so that the control panel displays the element composition and element content of the soil corresponding to the spectral data, the position information and environment information of the soil, and the soil detection analysis result determined based on the spectral data, the position information and environment information of the soil.

[0124] In addition, the portable LIBS rapid detector can perform sensitive analysis at a low concentration, and generally has a detection limit of ppm (parts per million) level. This makes it very useful in applications of tracking and detecting low-concentration elements, even though the sensitivity of the portable LIBS rapid detector is very high.

[0125] Further, the detection can be completed without professional operation. Compared with other analysis techniques, the portable LIBS rapid detector does not require cumbersome sample preparation steps, and the instrument has an easy-to-use user interface and operation guide, which makes the analysis process more simple and efficient, so that the detection can be completed without professional operation. Non-professionals only need to turn on the device, aim at the target, and then start measurement, and wait for the detection result to be displayed.

[0126] The optical detection device 40 intelligently distinguishes the soil environment to be detected by means of the illumination and CMOS imaging multiplexing optical path system and image recognition algorithm, determines the characteristics and conditions of the soil sample, and judges whether the detection requirements are met, so that data affected by impurities can be automatically excluded before element spectrum analysis is performed. Secondly, the rotation angle of the laser scanning galvanometer is precisely controlled to realize face scanning of the soil to be detected, so that single spectrum measurement integrates multi-point data acquisition and average calculation, can extract more comprehensive sample information, effectively reduces external interference, improves measurement accuracy and stability, and ensures that accurate and reliable detection results can be presented in complex environments.

[0127] It should be noted that the LIBS rapid detector provided in the embodiments of the utility model does not require sample preparation, that is, does not require a complex sample preparation process, can directly analyze actual samples, saves time, avoids interference problems caused by sample pollution, and ensures the accuracy of soil detection results.

[0128] The portable LIBS rapid detector provided in the embodiments of the utility model completes soil detection at different depths through the auxiliary detection structure, improves the stability of the device by using the optical detection device, thereby improving the stability of data, realizes rapid and accurate scanning detection of the surface to be detected, improves the anti-disturbance capability of the portable LIBS rapid detector, and meanwhile, the LIBS rapid detector meets the requirement of portability. In summary, the portable LIBS rapid detector meets the requirement of rapid and accurate detection of different depths of soil in a wide area in modern intelligent agriculture.

[0129] It is to be noted that the optical detection device and spectrometer in the portable LIBS rapid detector have built-in data processing and analysis functions, which can perform real-time data processing and result analysis after on-site detection, provide immediate feedback and judgment, and reduce the waiting time for laboratory analysis after sample collection. The real-time and fast data analysis feature enables users to quickly obtain results in the field or on-site environment and make timely decisions. This realizes the application of soil detection in a wide range of scenarios, enabling large-scale detection and vertical depth layer detection. It enables a more three-dimensional soil detection mode and more comprehensive soil detection data, ultimately forming a more intelligent soil element rapid detection method integrating "measurement and control-analysis". Moreover, it can realize multi-element synchronous detection: LIBS technology can simultaneously analyze multiple elements, including metals, non-metals, and rare earth elements, and can obtain information on multiple elements in one test without the need for multiple tests.

[0130] High integration: The overall volume of the LIBS rapid detector is small, the power consumption is low, and the weight is light. Compared with traditional LIBS systems, the portable LIBS rapid detector has the characteristics of miniaturization, simplicity, and lightness, and can be easily carried to the work site for detection. Due to its mobility, it is not only convenient for manual carrying, but also can be mounted on intelligent devices such as unmanned vehicles, providing more possibilities for some harsh environments or high-efficiency work scenarios, greatly expanding the application range and practicality of LIBS element detection technology.

[0131] Integrated structure design for easy carrying to the work site for in-situ detection. The LIBS rapid detector adopts an integrated structure design scheme, i.e., the laser, spectrometer, detachable power supply, and embedded main control board are designed as a "probe type" structure, and a hard soil drill bit is used as an auxiliary detection structure. This ensures that the LIBS rapid detector can efficiently and accurately complete the drilling task. The portable detection device can be directly taken to the detection site, fully utilizing the in-situ analysis and rapid response capability of LIBS technology, greatly improving the detection efficiency and flexibility.

[0132] The soil element detector provided by the embodiment of the utility model, based on laser-induced breakdown spectroscopy technology, does not need sample preparation, can detect soil elements at different depths, can cope with different soil environments (sensors monitor environmental information in real time), has accurate analysis, high integration, intelligence, and integrated structure, and can realize face scanning element detection. The portable rapid detector considers portability and integration, can be carried by workers to the work site for use as a portable device, or can be part of an integrated device mounted on unmanned vehicles and other equipment, integrated into modern automated and intelligent operation systems, and realized more efficient and intelligent operation modes.

[0133] It should be noted that the detection depth of the auxiliary detection structure 8 in the soil element detector provided in the embodiments of the present application is determined based on the displacement sensor, and the auxiliary detection structure can realize the function of drilling and measuring at the same time. For different soil texture environments, the appropriate auxiliary detection structure can be replaced at any time to ensure that the portable LIBS rapid detector can efficiently and accurately complete the drilling task. Thus, the depth of soil detection is improved, the optical detection device 40 in the portable LIBS rapid detector improves the accuracy of soil detection, and the breadth of soil detection is further improved, which is suitable for the rapid and large-area detection requirements of modern intelligent agriculture.

[0134] The soil element detection method provided by the present application will be described below, and the soil element detection method described below can be correspondingly referred to the soil element detector described above.

[0135] Based on any of the above embodiments, the present application provides a soil element detection method, Figure 10 is one of the process schematic diagrams of the soil element detection method provided by the present application, as Figure 10 indicated, the method comprises:

[0136] Step 1010, in the working process of the soil element detector, receiving the spectrum signal emitted by the plasma, and converting the spectrum signal into spectrum data, the plasma is obtained by the laser emitting laser to the soil to be detected of the soil element detector;

[0137] Step 1020, based on the spectrum data, determining the element composition and element content of the soil corresponding to the soil to be detected.

[0138] Specifically, in the working process of the soil element detector, the spectrum signal emitted by the plasma is received, and the spectrum signal is converted into spectrum data, and the plasma is obtained by the laser 9 emitting laser to the soil to be detected of the soil element detector.

[0139] After obtaining the spectrum data, the element composition and element content of the soil corresponding to the soil to be detected can be determined based on the spectrum data.

[0140] Figure 11 is a working flowchart of the soil element detector provided by the present application, as Figure 11 indicated, the device has two detection modes: the first kind is the fixed point surface scanning mode of the galvanometer movement. The second kind is the drilling scanning mode when the galvanometer is fixed.

[0141] 1. In the fixed-point second scanning mode, the position of each fixed-point detection is fed back to the main control system by the displacement sensor before starting scanning. After clicking the start detection, the CMOS camera first takes a picture of the scanning area, and then the laser 9 emits laser light to complete the surface scanning with the movement of the galvanometer. Subsequently, the multiple sets of spectral information collected by the spectrometer are averaged and converted into a spectral graph, which is saved in the same folder (named by the detection depth data) as the picture taken before starting scanning. At the same time, the image recognition algorithm will automatically distinguish whether there is impurity interfering with the detection result by calling the picture information in the folder. If there is, all information in the folder will be deleted and the detection position will be prompted to be adjusted. If not, the qualitative and quantitative analysis algorithm will call the spectral graph information in the folder to calculate the types and contents of elements in the soil, and display them together with the position, temperature, humidity and other information on the interface. Finally, after the detection is completed, all devices enter the standby state and wait for the next operation instruction.

[0142] 2. In the drilling scanning mode, the scanning action is performed while the drill bit works into the soil. In this mode, the galvanometer is fixed at the initial position without rotating. After the detection window is clicked to start detection, the CMOS camera will take a picture of the scanning target surface before each laser 9 emits light (the light emission frequency can be set by the user), and then the laser 9 emits light to complete a fixed-point scanning of the galvanometer. Subsequently, the spectral information collected by the spectrometer 15 is converted into a spectral graph, which is saved in the same folder as the picture taken before starting scanning. At the same time, the image recognition algorithm will automatically distinguish whether there is impurity interfering with the detection result by calling the picture information in the folder. If there is, all information in the folder will be deleted and the detection position will be prompted to be adjusted. If not, the quantitative analysis algorithm will call the spectral graph information in the folder to calculate the types and contents of elements in the soil, and display them together with the position, temperature, humidity and other information on the interface. In this mode, the number of detections needs to be set in advance, and the corresponding number of detections will be performed as the drill bit works into the soil. Then, the useful detection data of each detection will be displayed according to the different detection positions. After drilling is completed, the drill button is clicked to remove the device from the soil, and all devices enter the standby state and wait for the next operation instruction.

[0143] Figure 12 is the working mode diagram of the galvanometer assembly provided by the utility model, as shown in Figure 12 The entire galvanometer assembly is composed of a galvanometer A that can rotate in the X-axis direction, a motor A that controls the rotation of the galvanometer A, a galvanometer B that can rotate in the Y-axis direction, and a motor B that controls the rotation of the galvanometer B.

[0144] The Raspberry Pi sends preset coordinate information (X, Y values) to the MCU control board, the MCU extracts these values after receiving and calculates the corresponding analog voltage. The X value controls motor A, and the Y value controls motor B. The MCU outputs the calculated analog voltage signal to the corresponding motor. By changing the input voltage value of the motor, the galvanometer can be controlled to move different angles in the corresponding X-axis or Y-axis direction. For example, when the input voltage value is 3V, the galvanometer will rotate by 3°. In the face scanning mode, first, the galvanometer A rotates in the X-axis direction, so that the laser focal point moves on the X-axis. Then, after the galvanometer A stops rotating, the galvanometer B rotates in the Y-axis direction, so that the laser focal point moves on the Y-axis. Finally, after the galvanometer B stops rotating, the galvanometer A rotates again in the opposite direction by the same angle, so that it scans along the preset path. The laser focal point moves back and forth on the X-axis at different Y-axis coordinates to complete face scanning (snake motion as shown in Figure 1 In the initial stage, the size of the face scanning area is set to 1cm 1cm square, and the laser frequency is 5Hz. In 5S, a total of 25 points are scanned.

[0145] It can be understood that the portable LIBS rapid detector (soil element detector) can perform image automatic recognition and in-situ rapid detection.

[0146] To achieve the above purpose, the technical scheme adopted by the utility model is: a portable soil element detection device adopting soil image recognition technology, laser galvanometer scanning technology, highly integrated space coupling optical structure and drilling measurement synchronization.

[0147] Figure 13 is the second flowchart of the soil element detection method provided by the utility model, as shown in Figure 13 The method comprises the following steps:

[0148] 1. Through an image recognition algorithm, for example, a convolutional neural network algorithm (CNN), the abnormal spectrum data is removed, so as to avoid the influence of soil impurities on data accuracy; the convolutional neural network algorithm mainly converts the original image to a hyperplane coordinate system through a trained network model, then extracts the features of each image, and identifies and classifies the same images to the greatest extent. In our detection, each scanning target surface is photographed and saved. Before data analysis and processing, the convolutional neural network algorithm is used to classify the pictures containing stones, dry branches, garbage and other impurities, then the spectrum data in the folder to which the removed pictures belong is deleted.

[0149] 2. The method of reducing random errors that may exist in a single measurement point, reducing the influence of environmental factors and device noise, and weakening the influence of uneven element content distribution on the accuracy of the final data by simply averaging a plurality of sets of spectral data of a scanned target surface (point detection mode), thereby improving the accuracy and reliability of the spectral data. In the point detection mode, 25 sets of spectral data are collected for each scanned target surface, and then a set of data is formed by averaging the 25 sets of data. The obtained spectral data is a set of wavelength and spectral intensity corresponding data. We test 25 sets of spectral data by merging them into a wavelength corresponding to multiple sets of spectral intensity data, and then taking the average of the 25 sets of spectral intensity data corresponding to each wavelength to obtain a set of average spectral data E for subsequent algorithm processing.

[0150] E =

[0151] 3. The spectral graph formed by averaging the spectral data is processed by background subtraction to eliminate the influence of environmental light and illumination light source and other interference signals on the spectrum, highlight the target signal, reduce data noise, and improve the accuracy and reliability of the spectral data. A polynomial fitting method is provided for baseline correction. By fitting the baseline signal and subtracting the background signal, the final analysis and processing of the spectral data can effectively improve the data quality and accuracy, and provide a reliable basis for further spectral analysis.

[0152] 4. The spectral graph formed by averaging the spectral data is processed by background subtraction to eliminate the influence of environmental light and illumination light source and other interference signals on the spectrum, highlight the target signal, reduce data noise, and improve the accuracy and reliability of the spectral data. A spectral splicing method is provided, which integrates different spectral data sets into a single optical spectrum using wavelength alignment and intensity correction technology based on background subtraction, and combines the information of each waveband to obtain comprehensive spectral characteristics.

[0153] 5. The spectral data is smoothed by using a sliding average filtering algorithm to reduce noise and fluctuations. In a set of experimental data, N consecutive data points are selected, the average value of these points is calculated, and the average value is assigned to the center point of the N data points. The formula is as follows:

[0154]

[0155] wherein, is the sliding average value of the i-th data point, N is the window length, represents the j-th data point in the window. By calculating this average value, the smoothing of the data sequence can be realized.

[0156] 6. Find the peak value spectral data by peak search algorithm (local maximum algorithm), then determine the element types contained in the soil by comparing each characteristic peak with the element characteristic database. The basic principle of local maximum algorithm is that for a set of LIBS spectral data, the intensity value is regarded as a discrete sequence. If the first data satisfies the relationship, there is a maximum value between and. If it is Gaussian distribution, k is 1.5.

[0157]

[0158] By determining the element types contained in the sample, the qualitative analysis is completed.

[0159] 7. Quantitative analysis algorithm

[0160] Finally, the detection device uses the free calibration method (Calibration-Free Laser-Induced Breakdown Spectroscopy, CF-LIBS) to quantitatively analyze the content of each element contained in the soil. The free calibration method uses the spectral intensity of the sample to calculate the element concentration of the sample. When using the free calibration method to predict the concentration, the plasma needs to satisfy the local thermodynamic equilibrium condition, and the atomic spectral line intensity

[0161]

[0162] wherein,

[0163] Let: The above formula can be described as:

[0164] (1)

[0165] The above formula ​​​​​​​​​​​​​​​Where F is the instrument response parameter, and is a parameter related to the plasma temperature.

[0166] (2)

[0167] The calculation formula of the relative content of the element is obtained by back calculation:

[0168]

[0169] Generally, the radiation from neutral atoms and singly ionized ions will be measured in the experiment. The above formula is the relative content of the neutral atom. And for the singly ionized ion, it is generally obtained by Saha equation, so the total relative content can be written as:

[0170] (3)

[0171] Then the steps of measuring the relative content of the element using the free scaling method are as follows:

[0172] (1) Determine the plasma electron temperature;

[0173] (2) Obtain the intercept of the measured element on the Y axis of formula (1) ;

[0174] (3) Obtain the partition function of the element to be measured at the electron temperature by searching the NIST database ;

[0175] (4) Calculate the instrument response parameter by formula (2) F ;

[0176] (5) Calculate the response parameter F After that, the relative content of the measured element is calculated by formula (3).

[0177] Figure 14 The industrial control schematic diagram of the soil element detector is shown in the figure, Figure 14As shown, the system as a whole realizes the control of the mechanical equipment and the transmission of information through the embedded main control board 16 (the embedded main control board 16 is composed of a linux embedded control board and an MCU control board). The MCU control board controls the work of the driving auxiliary detection structure 8, the laser 9 and the driver of the laser scanning galvanometer assembly 28 through the driver; meanwhile, the work control and information transmission of the displacement sensor, the temperature sensor, the GPS positioning module and other sensors installed in the sensor 7 installation cavity and the spectrometer 15 are also realized; then the information is transmitted to the linux embedded control board. The linux embedded control board is installed with a core operating system and can control the camera of the CMOS camera 21 to take pictures for detecting the environment screening, and after analyzing and sorting all the information, the information is transmitted to the display screen module of the upper control panel 2 or APP for display. Figure 15 is a schematic diagram of a spectrum obtained by the soil element detector provided by the utility model for soil detection, as shown in Figure 15 , the abscissa is wavelength, and the ordinate is relative intensity, and it can be seen that the detector can extract effective spectral lines of Fe, Mg, Al, Ca and Pb and is used for subsequent content analysis, thereby proving the feasibility of the portable LIBS rapid detector for soil element detection.

[0178] Figure 16 is a fitting curve diagram of spectral intensity and drilling speed obtained by the soil element detector provided by the utility model by using the two detection methods of fixed-point detection and drilling detection, Figure 17 is an intensity comparison diagram of Al element characteristic spectral lines obtained by the soil element detector provided by the utility model by using the two detection methods of fixed-point detection and drilling detection, as shown in Figure 16 , Figure 17 , it can be known from the several groups of data diagrams that spectral data can be effectively obtained and content analysis can be performed for fixed-point detection and drilling detection at different speeds, but the drilling speed cannot be too fast (cannot exceed 5cm / s), otherwise the spectral data intensity will be too low, and the final obtained element content result will have a large error. It can be known from the fitting curve diagram of spectral intensity and drilling speed that within a reasonable drilling speed range, the intensity of the characteristic spectral line and the drilling speed are negatively correlated (approximately a first-order function).

[0179] The utility model embodiment provides a kind of in-situ, rapid soil detection operation method of field in the wild using the above portable detection equipment, specifically according to following steps:

[0180] Step 1, before using detection equipment, first, open the power supply switch of equipment, then click equipment self-check on control panel 2, ensure that each component in equipment can work normally, if there is equipment failure, then self-check fails and shows faulty component.

[0181] Step 2, according to the texture of the soil to be tested, different auxiliary detection structures 8 are selected, and then the operator enters the shallow soil with the portable rapid detector through the force arm handle 1, the telescopic rod 3 and the matched auxiliary detection structure 8, and determines the detection depth according to the feedback data of the displacement sensor.

[0182] Step 3, after the detection depth is determined, the entire portable rapid detector is adjusted to a height suitable for the operator to use by adjusting the length of the telescopic rod 3. After the adjustment is completed, the field illumination light source 20 is turned on, the surface scanning target surface window 31 is illuminated, and then the surface scanning target surface window 31 is imaged on the CMOS camera 21. Then the imaging information is sent to the control panel 2 through the embedded main control board 16, and then the target surface image transmitted back is automatically analyzed through the image recognition program (manual reinspection), to confirm whether there are impurities in the detection target surface window that affect the detection result. According to the analysis result, if there are no impurities in the surface scanning target surface window 31 at this moment, the next step is performed; if there are impurities, the detection position is replaced and steps 2 and 3 are repeated.

[0183] It should be noted that the image recognition program is deployed on the software end electrically connected with the portable LIBS rapid detector, and the image recognition program can be determined based on a machine learning or deep learning algorithm, and the embodiments of the present application do not make specific limitations.

[0184] Step 4, after confirming that the surface scanning target surface window 31 has no impurities, the field illumination light source 20 is turned off, and then the laser energy is set by changing the size of the variable diaphragm 22 to avoid weak spectral signals caused by too small laser energy and avoid spectral signal oversaturation caused by too large laser energy. Then the parameter setting option on the control panel 2 is clicked to enter the device parameter setting interface, the light output frequency of the laser 9 and the rotation speed of the laser scanning galvanometer assembly 28 are changed to meet the actual surface scanning point number requirement (at the same time, the size of the scanning target surface can be set by changing the rotation angle of the galvanometer). Finally, the spectral integration time and spectral average number of the spectrometer 15 are set according to the actual surface scanning point number.

[0185] Among them, the detection mode can include two kinds, one is the galvanometer motion surface scanning focusing detection mode, which can realize multi-point data acquisition at the same detection position, can extract more comprehensive sample information, effectively reduce external interference, further improve the measurement precision and stability, and ensure that accurate and reliable detection results can be presented in complex environments.

[0186] The second is the fixed-point focusing detection mode without galvanometer motion, which is mainly used for rapid detection mode of drilling (the device drills into the soil while the soil detection is performed). The two detection methods can be applied to different detection requirements in actual application scenarios.

[0187] It should be noted that the detection method includes an image recognition algorithm. In each soil detection, each detection point is photographed by a CMOS camera, and then the image recognition algorithm is used to determine whether there are interfering impurities that affect the detection at the detection point. If there are, the measurement data will be automatically deleted. This method can effectively improve the accuracy and reliability of the detection, and effectively avoid the problem of measurement position not meeting the detection conditions due to not preparing the sample.

[0188] Step 5, after setting the detection parameters, click the start detection option on the control panel 2, and the laser 9, spectrometer 15 and laser scanning galvanometer assembly 28 perform soil detection according to the set parameters. After completing a surface scan in the surface scanning target window 31, the laser 9 stops emitting light and automatically powers off (safety protection), the laser scanning galvanometer assembly 28 returns to the initial installation angle and stops rotating, and the spectrometer 15 converts the obtained spectral signals into spectral data and sends them to the control panel 2 through the embedded main control board 16. Then, the LIBS quantitative analysis program calculates the element composition and content in the soil and displays them on the control panel 2. At the same time, the environmental temperature and humidity sensor, displacement sensor, GPS sensor and other sensor components on the device also send the location information and environmental information of the detected soil to the control panel 2 through the embedded main control board 16, and display them together with the qualitative and quantitative analysis results.

[0189] Step 6, after completing the measurement, the measurement results can be saved and viewed anytime and anywhere in the local "query" and APP. The measurement results include spectral images, soil environmental information and qualitative and quantitative analysis results.

[0190] In summary, the above steps 1 to 6 can be summarized as the following four steps: 1. Detection position confirmation (detection depth and scanning target surface); 2. Detection parameter setting; 3. Start detection (collect spectral signals of the scanning target surface); 4. Data analysis (qualitative and quantitative analysis of soil elements through spectral data calculation).

[0191] It can be understood that the detection method includes a multi-element quantitative analysis algorithm based on spectrum. The collected spectral data is used for calculation and analysis to obtain the content of each element. At the same time, the temperature and humidity influence factors are added to the algorithm, which can correct the final calculated element content according to the real-time temperature and humidity information detected by the sensor, and improve the detection accuracy again.

[0192] In order to ensure that the portable element detection instrument receives sufficient light signals for accurate element quantitative analysis, it is necessary to ensure that the spot diameter of the focused laser for surface scanning is less than 0.5mm, and the spot diameter of the signal light coupled into the optical fiber is less than 0.3mm. We simulate and simulate the optical structure through the optical design software Zemax, and the results are shown in Figure 5 、 Figure 7 According to the simulation results of the software, it can be seen that the maximum spot diameter of the focused laser for maximum surface scanning (2cm x 2cm) is 243.881μm, and the maximum spot diameter of the signal light coupled into the optical fiber is 72.155μm, which meets the design requirements.

[0193] According to the test steps and methods of the embodiments of the utility model, we successfully obtain and arrange a set of detailed data. The following table lists the data results under some test conditions: Table 1 shows the corresponding relationship between the drill drilling speed and the element concentration when detecting the same piece of soil under different detection modes; Table 2 further analyzes the element concentration prediction error value when the drill drilling speed is within a certain range and exceeds the controllable range.

[0194] Table 1

[0195]

[0196] Table 2

[0197]

[0198] The data in the above two tables show that the drilling feasibility (which can detect the concentration of elements when fixed and moved) error is about 5%, but the speed cannot be too fast. As can be seen from the error comparison analysis table shown in Table 2, the error detected when the drill drilling speed is within a certain range (about 5cm / s) is about 5%, which is within the controllable error range. However, when the speed is too fast (10cm / s), the error will increase, resulting in inaccurate analysis results.

[0199] These data not only verify the accuracy and reliability of the method described in the utility model, but also provide a solid experimental basis for subsequent application and optimization.

[0200] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the utility model, but not to limit them; although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the utility model.

Claims

1. An optical detection device, characterized in that The laser beam expanding and collimating system, the multiplexing and folding optical path system, the imaging system, the area scanning optical path system, and the spectral signal acquisition optical path system are included. The laser beam expanding and collimating system expands and collimates the laser emitted by the laser and inputs the laser into the multiplexing and folding optical path system. The multiplexing and folding optical path system folds the expanded and collimated laser beam to obtain folded system exit laser and inputs the folded system exit laser into the area scanning optical path system. The area scanning optical path system focuses the folded system exit laser onto an area scanning target window to generate plasma. The spectral signal acquisition optical path system acquires signal light radiated by the plasma. The imaging system images the window of the area scanning target window on a CMOS camera.

2. The optical detection device of claim 1, wherein, The laser beam expanding and collimating system is sequentially provided with a variable diaphragm, a plano-concave lens, and a first plano-convex lens along the incident direction of the incident laser. The variable diaphragm adjusts the energy of the laser. The plano-concave lens and the first plano-convex lens expand and collimate the adjusted laser.

3. The optical detection device of claim 1, wherein, The multiplexing and folding optical path system includes a half-inch laser line mirror, a dichroic mirror, and a one-inch laser line mirror. The half-inch laser line mirror horizontally transmits the expanded and collimated laser. The dichroic mirror reflects laser light and transmits visible light, and the transmitted visible light includes illumination light and imaging light. The one-inch laser line mirror folds the expanded and collimated laser beam to obtain folded system exit laser.

4. The optical detection device according to any one of claims 1 to 3, characterized in that, The area scanning optical path system is sequentially provided with a laser scanning galvanometer assembly, a second plano-convex lens, a third plano-convex lens, and an area scanning target window along the incident direction of the incident laser. A focusing lens group performs laser area scanning at the area scanning target window, and the focusing lens group includes the second plano-convex lens and the third plano-convex lens. The area scanning target window is installed with quartz glass, and the scanning target surface is a square target surface, and the size of the square target surface is adjustable.

5. The optical detection device according to any one of claims 1 to 3, characterized in that, The imaging system is sequentially provided with a field of view illumination light source, a first lenticular lens, a beam splitter, a second lenticular lens, and a CMOS camera along the incident direction of the incident laser. The field of view illumination light source generates light for illuminating the area scanning target window, and the field of view illumination light source controls the illumination time through a circuit switch. The first lenticular lens changes the light emitted by the field of view illumination light source into parallel light. The beam splitter reflects the parallel light into the multiplexing and folding optical path system. The second lenticular lens collects imaging light of the area scanning target window. The CMOS camera displays the imaging light.

6. The optical detection device according to any one of claims 1 to 3, characterized in that The spectral signal acquisition optical path system includes a fourth plano-convex lens and an off-axis parabolic mirror. The area scanning target window is between the focal point of the fourth plano-convex lens and the fourth plano-convex lens, and all signal light radiated by the plasma between the focal point and the edge light of the fourth plano-convex lens is collected. The off-axis parabolic mirror collects the signal light.

7. A soil element detector, characterized by, The optical detection device includes: The optical detection device according to any one of claims 1 to 6.

8. The soil element detector of claim 7, wherein, Further includes a laser, a spectrometer, an embedded main control board, and a sensor; The laser emits laser light; The optical detection device includes: The optical detection device generates plasma by scanning ablation of a detection surface of soil at different detection depths by the laser, and collects signal light radiated by the plasma; The spectrometer converts a spectrum signal obtained by transmission of the signal light into spectrum data; The sensor collects position information and environmental information of the soil; The embedded main control board is connected with the spectrometer and the sensor respectively, and is used for displaying the position information and the environmental information, and soil element components and soil element contents corresponding to the spectrum data.

Images