Three-dimensional gas concentration field measurement device, method, system and supporting probe system

Abstract

The present invention belongs to the field of three-dimensional gas concentration measurement, and discloses a three-dimensional gas concentration field measurement device, method, system and its supporting probe system, including a translation stage, a probe, a stage, a bracket, multiple motors, an optical reflector, a temperature and current control module, etc. The laser light emitted by the laser is reflected from the optical reflector to the photodetector and subjected to photoelectric conversion, and then processed by a phase-locked amplifier to detect the second harmonic signal, and finally obtain the concentration information of the target gas. The present invention designs a three-dimensional gas concentration field measurement device and a supporting reflective probe, and uses an optical reflector in combination with a laser and a photodetector to realize the collection and processing of the target gas concentration; the unknown target gas concentration is detected, the operation is convenient, and the target gas concentration can be detected with high accuracy and high precision.

Description

Technical Field

[0001] The present invention belongs to the field of three-dimensional gas concentration measurement, and in particular relates to a three-dimensional gas concentration field measurement device, method, system and a matching probe system. Background Art

[0002] Currently, the three-dimensional gas concentration fields of specific gases in various conditions, such as flame combustion, landfill emissions, and factory pipelines, often vary with the progress of their reactions. Monitoring target gas concentrations can often help analyze the course of events or prevent disasters. This is explained in detail below using flame combustion as an example. Flame combustion is a chemical reaction that involves changes in key parameters such as temperature, velocity, and gas concentration. As a core parameter that reflects the state of a combustion field, carbon dioxide concentration plays an increasingly important role in predicting, controlling, and comprehensively monitoring combustion. Existing carbon dioxide concentration measurement technology primarily uses current and temperature to tune the output wavelength of a semiconductor laser, scanning a specific absorption line of the substance being measured, and detecting the absorption intensity of the absorption spectrum to determine the measured carbon dioxide concentration. Using probe measurement technology to measure carbon dioxide concentration in combustion fields can significantly improve measurement accuracy, overcoming the limitations of traditional carbon dioxide detection technology in some specific scenarios. This technology has been widely used to measure carbon dioxide concentration in high-temperature combustion fields, such as engines and gas turbines.

[0003] Tunable laser absorption spectroscopy (TDLAS) is a non-contact method for measuring gas. When the laser passes through the gas, by adjusting the sawtooth signal, the laser output wavelength can be made to cover the absorption spectrum of the target gas, thereby detecting the concentration of the substance being measured. This technology can directly obtain the gas concentration through calculation, without the need for concentration calibration using standard gases. However, in actual measurements, the existing TDLAS for measuring the target gas concentration in a confined space with a relatively large background three-dimensional gas concentration field still has problems such as difficult operation and low detection sensitivity. Especially in trace gases, the measurement error is large.

[0004] Typically, measurement results in TDLAS technology are easily interfered with by the laser, detector, and noise, and may even be lost in the system noise. Furthermore, the concentration of the target gas being measured is low, and the data obtained is often incomplete.

[0005] Through the above analysis, the problems and defects of the existing technology are as follows:

[0006] (1) In actual measurement, for the target gas concentration measurement in a confined space with a relatively large background three-dimensional gas concentration field, the existing tunable laser absorption spectroscopy technology has the problems of difficult operation and low detection sensitivity, especially in trace gases, the measurement error is large.

[0007] (2) The measurement results of existing tunable laser absorption spectroscopy technology are easily interfered by the laser, detector and noise, and are even annihilated by the noise of the system. In addition, the concentration of the target gas being measured is low, and the data obtained are often incomplete. Summary of the Invention

[0008] In response to the problems existing in the prior art, the present invention provides a three-dimensional gas concentration field measurement device, method, system and a supporting probe system.

[0009] The present invention is implemented as follows: a three-dimensional gas concentration field measuring device, the three-dimensional gas concentration field measuring device comprising:

[0010] Translation stage, probe system (including bracket, laser, photodetector, optical reflector), stage, multiple motors, temperature and current control modules, lock-in amplifier, data acquisition card and host computer;

[0011] The translation stage is a three-axis motion system built by linear modules, with bearings fixing both ends of the lead screw to achieve three-dimensional motion;

[0012] The stage is mounted on the displacement stage;

[0013] The probe is mounted on the stage and is used for detection as the stage moves;

[0014] The plurality of motors are mounted on the translation stage and are used to drive the X, Y and Z axis motions of the translation stage;

[0015] The temperature and current control module is connected to the laser, and the input end is connected to the output end of the data acquisition card, and is used to drive the laser to emit laser light;

[0016] The laser is connected to the fiber collimator interface and installed on the mounting base of the temperature and current control module. Its input end is connected to the output end of the data acquisition card and is used to emit near-infrared visible light with a wavelength of 1573.2nm (taking carbon dioxide gas in the combustion field as an example);

[0017] The optical reflector is placed on the bracket and is used to emit the absorbed laser light to the photodetector;

[0018] The photodetector is connected to the input end of the lock-in amplifier and is used to perform photoelectric conversion on the received laser light;

[0019] The output end of the lock-in amplifier is connected to the input end of the data acquisition card, and is used to demodulate the signal output by the photodetector, and transmit the demodulated signal to the host computer through the data acquisition card;

[0020] The data acquisition card is connected to the host computer and is used to send the signal demodulated by the lock-in amplifier to the host computer;

[0021] The host computer is used to modulate the signal and process the signal collected by the data acquisition card to finally obtain the concentration of the gas to be measured.

[0022] Furthermore, the device adopts a linear parallel measurement method.

[0023] Furthermore, the photodetector is a low-noise preamplifier indium gallium arsenide photodetector with a detection wavelength range of 0.8 to 2.1 μm. It amplifies and measures the intensity of the laser reflected by the gas and converts the laser intensity into a voltage signal. Its output end is first connected to the input end of the oscilloscope and then connected to the input end of the phase-locked amplifier after debugging is completed.

[0024] Furthermore, the host computer generates a low-frequency scanning signal and a high-frequency modulation signal in a digital manner, and the two voltage signals are superimposed and converted into a current signal to control the working current of the laser.

[0025] Furthermore, the laser is a DFB semiconductor laser, the central wavelength of the laser covers the absorption peak of the target gas, the continuous output optical power is 10mW, and the single-mode pigtail output is used.

[0026] Furthermore, the temperature and current control module has a temperature control stability of 0.01°C, a driving current range of 0-250mA, an analog modulation bandwidth of 100kHz, and supports external analog modulation.

[0027] Another object of the present invention is to provide a three-dimensional gas concentration field measurement method implementing the three-dimensional gas concentration field measurement device, the specific process of the three-dimensional gas concentration field measurement method is:

[0028] First, the laser light emitted by the laser is reflected by the optical reflector to the photodetector, which receives and converts it into an electrical signal. The electrical signal carrying gas information is demodulated by the lock-in amplifier to obtain a second harmonic signal. The digital signal is obtained using the data acquisition card, and the harmonic signal is extracted.

[0029] Then, data filtering and background subtraction are used to remove the interference of background signals in harmonic signals;

[0030] Finally, the amplitude of the processed second harmonic signal is extracted, and the data is collected by the data acquisition card and transmitted to the host computer. The extracted data points are fitted, and the concentration of the gas to be measured is inverted by the fitting equation obtained by fitting, and finally the concentration information of the carbon dioxide of the gas to be measured is obtained.

[0031] Another object of the present invention is to provide a three-dimensional gas concentration field measurement system for implementing the three-dimensional gas concentration field measurement method, the three-dimensional gas concentration field measurement system comprising:

[0032] Laser, for emitting laser light;

[0033] a temperature and current controller for coarsely adjusting the temperature of the laser;

[0034] an optical reflector, used to reflect the laser signal to the photodetector 9;

[0035] Photoelectric detector, install the photoelectric detector and the light end floor, facing the reflected light outlet of the optical reflector;

[0036] The lock-in amplifier is used to demodulate the signal output by the photodetector and transmit the demodulated signal to the host computer through the data acquisition card. Its output end is connected to the input end of the data acquisition card.

[0037] The data acquisition card is a multifunctional data acquisition card of the PCIe / PXIe-5500 series. It runs on PCIe, PXIe, TXI, and USB buses and is used to send the demodulated signal of the lock-in amplifier to the host computer.

[0038] The host computer is a microcomputer, and its output end is connected to the input end of the data acquisition card.

[0039] Furthermore, the detection process of the three-dimensional gas concentration field measurement system includes the following steps:

[0040] Step 1: Place the translation stage at any point on a plane, connect the power supply, and make motor 1 drive the Y-axis of the translation stage, motor 3 drive the X-axis of the translation stage, and motor 2 drive the Z-axis of the translation stage to perform three-dimensional motion.

[0041] Step 2: The temperature and current control module is connected to the laser, and the optical reflector is placed on the bracket. The laser outputs light power, passes through the three-dimensional gas concentration field, and is then reflected by the optical reflector to the photodetector.

[0042] Step 3: Connect the output end of the photodetector to an oscilloscope. After the photodetector receives the target gas reflected by the optical reflector, wait for the oscilloscope waveform to show sufficient absorption.

[0043] Step 4: Connect the output of the photodetector to the input of the lock-in amplifier for phase-locked demodulation. The output of the lock-in amplifier is connected to the input of the data acquisition card. The output of the data acquisition card is connected to the host computer. The data is collected by the data acquisition card and transmitted to the host computer for processing.

[0044] Step 5: Move the translation stage in three-dimensional space and repeat steps 1 to 4 until the target concentration measurement area is covered, and draw the recorded data into an image.

[0045] Another object of the present invention is to provide a matching reflective probe system for implementing the three-dimensional gas concentration field measurement device, wherein the matching reflective probe system includes a laser, a photodetector, a bracket and an optical reflector.

[0046] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0047] First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving these problems, this paper closely combines the technical solutions to be protected by the present invention and the results and data during the research and development process, and analyzes in detail and in depth how the technical solutions of the present invention solve the technical problems and some creative technical effects brought about by solving the problems. The specific description is as follows:

[0048] The present invention designs a three-dimensional gas concentration field measurement device and a matching reflective probe, and uses an optical reflector in combination with a laser and a photodetector to realize the collection and processing of the target gas concentration; for the concentration information at a specific position in the three-dimensional gas concentration field, the position of the stage is changed by driving the displacement stage on the X-axis, Y-axis, and Z-axis by a motor, and then the laser on the stage emits a sawtooth wave modulated by a high-frequency signal that can cover the absorption peak of the target gas; after the frequency center of the sawtooth wave is absorbed by the target gas, the photodetector detects the sawtooth wave light intensity information; then a phase-locked amplifier is used to demodulate the signal carrying the gas information, and after eliminating the interference of the background signal in the harmonic signal, the data is fitted to complete the detection of the unknown target gas concentration. The operation is convenient and can realize high-precision and high-accuracy detection of the target gas concentration.

[0049] Second, considering the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by the present invention are described in detail as follows:

[0050] This invention provides a three-dimensional gas concentration field measurement device and a matching reflective probe. TDLAS technology, with its strong adaptability to complex environments, high selectivity, and low cost, is often used for trace gas measurement. This device, based on tunable semiconductor laser absorption spectroscopy, improves upon TDLAS technology. By adjusting the laser position via a motor-controlled translation stage, it enables targeted measurement of specific locations in the three-dimensional gas concentration field. This measurement device offers the advantages of ease of operation and high sensitivity, significantly improving the accuracy of measured gas concentrations.

[0051] Third, as auxiliary evidence for the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0052] Does the technical solution of the present invention solve the technical problems that people have always wanted to solve but have never been able to solve successfully?

[0053] The challenges and drawbacks of existing technologies are as follows: First, in actual measurements, existing tunable laser absorption spectroscopy technology is difficult to operate and has low detection sensitivity when measuring target gas concentrations in a confined space with a relatively large background three-dimensional gas concentration field. This leads to large measurement errors, especially in trace gases. The three-dimensional gas concentration field measurement device and accompanying reflective probe system designed in this invention utilize a method combining an optical reflector with a laser and a photodetector to achieve the acquisition and processing of target gas concentrations. This method facilitates the detection of unknown target gas concentrations and enables highly accurate and precise measurement of target gas concentrations.

[0054] Secondly, the detection results of tunable laser absorption spectroscopy technology are often interfered by lasers, detectors and noise, and are even annihilated in the noise of the system. When the concentration of the target gas to be measured is low, the data obtained is often incomplete. The present invention uses an optical reflector to reflect the laser into a photodetector, which receives and converts the laser into an electrical signal. The electrical signal carrying gas information is demodulated by a phase-locked amplifier to obtain a second harmonic signal. The digital signal is obtained by using the data acquisition card, and the harmonic signal is extracted. Then, data filtering and background subtraction are used to remove the interference of the background signal in the harmonic signal. The amplitude of the processed second harmonic signal is extracted, the collected data is transmitted, and the extracted data points are fitted. The gas concentration is inverted by the fitting equation obtained by fitting, and the concentration information of the gas to be measured, carbon dioxide, is obtained. In the present invention, the interference of the background signal can be eliminated by the method of data filtering and background subtraction, the noise of the system is reduced, and the data extracted by the collected second harmonic is also more complete. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of the structure of a three-dimensional gas concentration field measurement device provided by an embodiment of the present invention;

[0056] Figure 2 Schematic diagram of the structure of a three-dimensional gas concentration field measurement system provided by an embodiment of the present invention;

[0057] Figure 3 This is a schematic diagram of the internal structure of the matching probe system provided by an embodiment of the present invention;

[0058] Figure 4 This is a second harmonic diagram of a common detection system provided by an embodiment of the present invention;

[0059] Figure 5 This is a second harmonic detection diagram of the system provided by an embodiment of the present invention;

[0060] Figure 6 This is a concentration distribution diagram on the XY plane with Z set to 0, provided by an embodiment of the present invention;

[0061] Figure 7 This is a concentration distribution diagram of the Z axis with X and Y set to 0 provided by an embodiment of the present invention.

[0062] In the figure, 1. Motor; 2. Motor; 3. Motor; 4. Y-axis of the translation stage; 5. X-axis of the translation stage; 6. Probe; 7. Z-axis of the translation stage; 8. Stage; 9. Photodetector; 10. Laser; 11. Bracket; 12. Optical reflector; 13. Temperature and current control module; 14. Phase-locked amplifier; 15. Data acquisition card; 16. Host computer. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0064] In order to enable those skilled in the art to fully understand how to implement the present invention, this section provides an explanatory embodiment that expands on the technical solutions of the claims.

[0065] like Figure 1 As shown, the three-dimensional gas concentration field measurement device provided by the embodiment of the present invention includes:

[0066] Translation stage, probe system (including photodetector 9, laser 10, bracket 11, optical reflector 12), stage 8, motor 1, temperature and current control module 13, lock-in amplifier 14, data acquisition card 15 and host computer 16;

[0067] Stage 8 is placed on a translation stage, and a motor drives the stage's position along the X, Y, and Z axes. A probe is placed on the stage, where the laser's output wavelength is tuned by both temperature and current control modules 13. Temperature control primarily controls the center wavelength, while current determines the sawtooth waveform. After being absorbed by the gas, the laser is reflected by optical mirror 12 on bracket 11 onto a detector, where it is demodulated in a lock-in amplifier. The demodulated second harmonic signal is collected by an acquisition card and analyzed by a host computer to extract concentration information.

[0068] like Figure 3 , the photodetector, laser, bracket, and optical reflector together constitute the probe system 6;

[0069] like Figure 2 The probe system 6 may be mounted on a three-dimensional measuring device.

[0070] The translation stage is a three-axis motion system built by linear modules, with bearings fixing both ends of the lead screw to achieve three-dimensional motion;

[0071] The stage 8 is mounted on the displacement stage;

[0072] The probe 6 is mounted on the stage 8 and is used for detection as the stage moves;

[0073] The motor is mounted on the translation stage and is used to drive the X, Y and Z axis motions of the translation stage;

[0074] The temperature and current control module 13 is connected to the laser 10, and its input end is connected to the output end of the data acquisition card 15, and is used to drive the laser 10 to emit laser light;

[0075] The laser 10 is connected to the fiber collimator interface and mounted on the mounting base of the temperature and current control module 13 , and its input end is connected to the output end of the data acquisition card 15 .

[0076] Used to emit near-infrared visible light with a wavelength of 1573.2nm (different target gases emit different wavelengths, this is taking carbon dioxide gas in a combustion field as an example);

[0077] The optical reflector 12 is placed on the bracket 11 and is used to transmit the absorbed laser light to the photodetector 9;

[0078] The photodetector 9 is connected to the input end of the lock-in amplifier 14 and is used to perform photoelectric conversion on the received laser light;

[0079] The output end of the lock-in amplifier 14 is connected to the input end of the data acquisition card 15, which is used to demodulate the signal output by the photodetector 9 and transmit the demodulated signal to the host computer 16 through the data acquisition card 15;

[0080] The data acquisition card 15 is connected to the host computer 16 and is used to send the signal demodulated by the lock-in amplifier 14 to the host computer 16;

[0081] The host computer 16 is used to modulate the signal and process the signal collected by the data acquisition card 15 to finally obtain the concentration of the gas to be measured.

[0082] Furthermore, the device adopts a linear parallel measurement method instead of a traditional fixed random point measurement method, and can be adjusted according to the needs of the measurement area to improve the measurement accuracy of the target gas.

[0083] Furthermore, the photodetector 9 is a low-noise preamplifier indium gallium arsenide photodetector 9 with a detection wavelength range of 0.8 to 2.1 μm. It amplifies and measures the intensity of the laser reflected by the gas and converts the laser intensity into a voltage signal. Its output end is first connected to the input end of the oscilloscope and then connected to the input end of the phase-locked amplifier 14 after debugging is completed.

[0084] Furthermore, the host computer 16 generates a low-frequency scanning signal and a high-frequency modulation signal in a digital manner, and the two voltage signals are superimposed and converted into a current signal to control the working current of the laser 10.

[0085] Furthermore, the laser 10 is a DFB semiconductor laser, the central wavelength of the laser 10 covers the absorption peak of the target gas, the continuous output optical power is 10 mW, and the single-mode pigtail output is used.

[0086] The temperature and current control module 13 has a temperature control stability of 0.01° C., a driving current range of 0-250 mA, an analog modulation bandwidth of 100 kHz, and supports external analog modulation.

[0087] Furthermore, the data acquisition card 15 is a multifunctional data acquisition card of the PCIe / PXIe-5500 series, which can run on PCIe, PXIe, TXI and USB buses.

[0088] The present invention also provides a three-dimensional gas concentration field measurement method, comprising the following steps:

[0089] First, the laser light emitted by the laser 10 is reflected by the optical reflector 12 to the photodetector, which receives the light and converts it into an electrical signal. The electrical signal carrying gas information is demodulated by the lock-in amplifier 14 to obtain a second harmonic signal, which is then obtained as a digital signal using the data acquisition card 15, i.e., the harmonic signal is extracted.

[0090] Then, data filtering and background subtraction were used to remove the interference of background signals;

[0091] The detected harmonic signal may still be interfered by various background signals, including residual amplitude modulation noise and large-pitch optical interference fringes. The residual amplitude modulation includes linear and nonlinear parts. The linear part is caused by the linear relationship between the light intensity of the laser 10 and the injected current, and the nonlinear part is caused by the slight nonlinearity of the signal amplitude in the laser driver or signal source. In particular, when the low-frequency scanning signal contains fringes, periodic background signals will appear on the harmonics, which can be filtered out by background subtraction.

[0092] Finally, after the data is filtered and the background is subtracted, the amplitude of the processed second harmonic signal is extracted, and the data is collected by the data acquisition card 15 and transmitted to the host computer 16. The extracted data points are fitted, and the concentration of the gas to be measured is inverted by the fitting equation (i.e., the inversion equation) obtained by fitting, and finally the concentration information of the carbon dioxide of the gas to be measured is obtained.

[0093] Furthermore, the area between the probe and the optical reflector 12 is a flame area, ie, a target concentration measurement area.

[0094] like Figure 2 As shown, an embodiment of the present invention further provides a three-dimensional gas concentration field measurement system, comprising:

[0095] A laser 10, configured to emit laser light;

[0096] a temperature and current controller for coarsely adjusting the temperature of the laser 10;

[0097] an optical reflector 12, for reflecting the laser signal to the photodetector 9;

[0098] Photoelectric detector 9, install photoelectric detector 9 and light end floor, reflect light outlet of optical reflector 12;

[0099] The lock-in amplifier 14 is used to demodulate the signal output by the photodetector 9 and transmit the demodulated signal to the host computer 16 through the data acquisition card 15, and its output end is connected to the input end of the data acquisition card 15;

[0100] The data acquisition card 15 sends the demodulated signal of the lock-in amplifier 14 to the host computer 16;

[0101] The host computer 16 is a microcomputer, and its output end is connected to the input end of the data acquisition card 15 .

[0102] Furthermore, the detection process of the three-dimensional gas concentration field detection system includes the following steps:

[0103] Step 1: Place the translation stage at any point on a plane, turn on the power, and make motor 1 drive the Y-axis 4 of the translation stage, motor 3 drive the X-axis 5 of the translation stage, and motor 2 drive the Z-axis 7 of the translation stage to perform three-dimensional motion;

[0104] Step 2: The temperature and current control module 13 is connected to the laser 10, and the optical reflector 12 is placed on the bracket 11. The laser 10 outputs light power, passes through the three-dimensional gas concentration field, and is then reflected by the optical reflector 12 to the photodetector 9;

[0105] Step 3: The output end of the photodetector 9 is connected to an oscilloscope. After the photodetector 9 receives the target gas reflected by the optical reflector 12, it waits for the oscilloscope waveform to show that it is fully absorbed.

[0106] Step 4: Connect the output of the photodetector 9 to the input of the lock-in amplifier 14 for phase-locked demodulation. The output of the lock-in amplifier 14 is connected to the input of the data acquisition card 15. The output of the data acquisition card 15 is connected to the host computer 16. The data is collected by the data acquisition card 15 and transmitted to the host computer 16 for processing.

[0107] Step 5: Move the translation stage in three-dimensional space and repeat steps 1 to 4 until the target concentration measurement area is covered, and draw the recorded data into an image.

[0108] like Figure 3 As shown, the present invention also provides a matching reflective probe system of the three-dimensional gas concentration field measurement device, including a laser, a photodetector, a bracket and an optical reflector.

[0109] In order to prove the creativity and technical value of the technical solution of the present invention, this section provides application examples of the claimed technical solution on specific products or related technologies.

[0110] The present invention utilizes a probe system to better improve measurement accuracy when measuring carbon dioxide concentration in a combustion field, solves the limitations of traditional carbon dioxide detection technology under specific circumstances, and can be widely used in carbon dioxide concentration detection in high-temperature combustion fields.

[0111] The embodiments of the present invention have achieved some positive results during the development or use process, and indeed have great advantages over the existing technology. The following content describes them in conjunction with data, charts, etc. from the experimental process.

[0112] A cubic enclosed area with a length, width and height of 20m was filled with a certain amount of carbon dioxide gas. The carbon dioxide concentration was detected using a conventional system and the invented system respectively. It can be seen that the second harmonic peak value detected by the system was significantly improved. Figure 4 It is the second harmonic of the ordinary detection system; Figure 5 The system provided by the embodiment of the present invention detects the second harmonic; taking the center of the site as the origin, a carbon dioxide concentration distribution map of the site is drawn, and it can be observed that the data detected by the system is relatively continuous and complete. Figure 6 The concentration distribution diagram on the XY plane is when Z is 0; Figure 7 It is a concentration distribution diagram with X and Y taking 0 and Z axis.

[0113] It should be noted that the embodiments of the method portion of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware portion can be implemented using dedicated logic; the software portion can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. Those skilled in the art will appreciate that the above-mentioned devices and methods can be implemented using computer-executable instructions and / or contained in processor control code, for example, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, or can be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0114] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A three-dimensional gas concentration field measurement device, characterized in that: The three-dimensional gas concentration field measuring device comprises: Translation stage, probe, stage, bracket, multiple motors, optical mirrors, temperature and current control modules, lasers, photodetectors, lock-in amplifiers, data acquisition cards and host computers; The translation stage is a three-axis motion system built by linear modules, with bearings fixing both ends of the lead screw to achieve three-dimensional motion; The stage is mounted on the displacement stage; The probe is mounted on the stage and is used for detection as the stage moves; The plurality of motors are mounted on the translation stage and are used to drive the X, Y and Z axis motions of the translation stage; The temperature and current control module is connected to the laser, and the input end is connected to the output end of the data acquisition card, and is used to drive the laser to emit laser light; The laser output end of the laser is connected to the fiber collimator interface and is installed on the mounting base of the temperature and current control module. Its input and output ends are connected to the output end of the data acquisition card and are used to emit near-infrared visible light with a wavelength of 1573.2nm; The optical reflector is placed on the bracket and is used to emit the absorbed laser light to the photodetector; The photodetector is connected to the input end of the lock-in amplifier and is used to perform photoelectric conversion on the received laser light; The output end of the lock-in amplifier is connected to the input end of the data acquisition card, and is used to demodulate the signal output by the photodetector, and transmit the demodulated signal to the host computer through the data acquisition card; The data acquisition card is connected to the host computer and is used to send the signal demodulated by the lock-in amplifier to the host computer; The host computer is used to modulate the signal and process the signal collected by the data acquisition card to finally obtain the concentration of the gas to be measured; The photodetector is a low-noise preamplifier indium gallium arsenide photodetector with a detection wavelength range of 0.8 to 2.1 μm. It amplifies and measures the intensity of the laser reflected by the gas and converts the laser intensity into a voltage signal. Its output is first connected to the input of an oscilloscope and then to the input of a lock-in amplifier after debugging is completed. The host computer generates a low-frequency scanning signal and a high-frequency modulation signal in a digital manner. The two voltage signals are superimposed and converted into a current signal to control the working current of the laser.

2. The three-dimensional gas concentration field measurement device according to claim 1, characterized in that: The device adopts a linear parallel measurement method.

3. The three-dimensional gas concentration field measurement device according to claim 1, characterized in that: The laser is a DFB semiconductor laser, the central wavelength of the laser covers the absorption peak of the target gas, the continuous output optical power is 10mW, and the single-mode pigtail output is used.

4. The three-dimensional gas concentration field measurement device according to claim 1, characterized in that: The temperature and current control module has a temperature control stability of 0.01°C, a driving current range of 0-250mA, an analog modulation bandwidth of 100kHz, and supports external analog modulation.

5. A matching reflection probe system for implementing the three-dimensional gas concentration field measurement device according to any one of claims 1 to 4, characterized in that: The matching reflective probe system includes a laser, a photoelectric detector, a bracket and an optical reflector, wherein the laser and the photoelectric detector are respectively inserted into ports on the bracket, and the optical reflector is installed on the bracket base.

6. A three-dimensional gas concentration field measurement method using the three-dimensional gas concentration field measurement device according to any one of claims 1 to 4, characterized in that: The specific process of the three-dimensional gas concentration field measurement method is as follows: First, the laser light emitted by the laser is reflected by the optical reflector to the photodetector, which receives and converts it into an electrical signal. The electrical signal carrying gas information is demodulated by the lock-in amplifier to obtain a second harmonic signal. The digital signal is obtained using the data acquisition card, and the harmonic signal is extracted. Then, data filtering and background subtraction are used to remove the interference of background signals in harmonic signals; Finally, the amplitude of the processed second harmonic signal is extracted, and the data is collected by the data acquisition card and transmitted to the host computer. The extracted data points are fitted, and the concentration of the gas to be measured is inverted by the least squares fitting equation obtained by fitting, such as y=aX+b, to finally obtain the concentration information of the gas to be measured.

7. A three-dimensional gas concentration field measurement system for implementing the three-dimensional gas concentration field measurement method according to claim 6, characterized in that: The three-dimensional gas concentration field measurement system comprises: Laser, for emitting laser light; a temperature and current controller for coarsely adjusting the temperature of the laser; an optical reflector for reflecting the laser signal to a photodetector; Photoelectric detector, install the photoelectric detector and connect it to the light end floor, and reflect the light outlet of the optical reflector; The lock-in amplifier is used to demodulate the signal output by the photodetector and transmit the demodulated signal to the host computer through the data acquisition card. Its output end is connected to the input end of the data acquisition card. The data acquisition card is a multifunctional data acquisition card of the PCIe / PXIe-5500 series. It runs on PCIe, PXIe, TXI, and USB buses and is used to send the demodulated signal of the lock-in amplifier to the host computer. The host computer is a microcomputer, and its output end is connected to the input end of the data acquisition card.

8. The three-dimensional gas concentration field measurement system according to claim 7, characterized in that: The detection process of the three-dimensional gas concentration field measurement system includes the following steps: Step 1: Place the translation stage at any point on a plane, connect the power supply, and make motor 1 drive the Y-axis of the translation stage, motor 3 drive the X-axis of the translation stage, and motor 2 drive the Z-axis of the translation stage to perform three-dimensional motion. Step 2: The temperature and current control module is connected to the laser, and the optical reflector is placed on the bracket. The laser outputs light power, passes through the three-dimensional gas concentration field, and is then reflected by the optical reflector to the photodetector. Step 3: Connect the output end of the photodetector to an oscilloscope. After the photodetector receives the target gas reflected by the optical reflector, wait for the oscilloscope waveform to show sufficient absorption. Step 4: Connect the output of the photodetector to the input of the lock-in amplifier for phase-locked demodulation. The output of the lock-in amplifier is connected to the input of the data acquisition card. The output of the data acquisition card is connected to the host computer. The data is collected by the data acquisition card and transmitted to the host computer for processing. Step 5: Move the translation stage in three-dimensional space and repeat steps 1 to 4 until the target concentration measurement area is covered, and draw the recorded data into an image.

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