Calibration Method and System for Gas Detection Lidar

Abstract

The present application discloses a calibration method and system for a gas detection lidar, relating to the technical field of lidar. The method includes: obtaining a first echo signal intensity and a second echo signal intensity of the lidar to be processed; wherein, the first echo signal intensity is detected by using an auxiliary calibration device and the lidar to be processed, and the light emission and reception optical path of the auxiliary calibration device meets a preset transmission and reception field of view condition; based on the first echo signal intensity and the second echo signal intensity, using a preset calibration algorithm, obtaining a target calibration parameter; based on the target calibration parameter, using a preset influence value algorithm, determining a lidar system efficiency influence value; based on the lidar system efficiency influence value, performing calibration processing on the lidar to be processed to obtain a calibrated lidar.

Description

Technical Field

[0001] This application relates to the technical field of lidar, specifically to technical fields such as gas density detection technology and gas density detection lidar technology, and particularly relates to a calibration method and system for a gas detection lidar. Background Art

[0002] Generally, in order to ensure the detection accuracy and precision of a gas detection lidar, the lidar needs to be calibrated before use. In the related art, a horizontal detection method is adopted to obtain the variation of the lidar system efficiency with distance, so as to realize the calibration of the gas detection lidar.

[0003] However, this method has two main defects. First, the detection process requires an extremely open experimental site. Second, the ideal condition for the atmosphere to be uniform in the horizontal direction has a large error in the actual detection process. Summary of the Invention

[0004] This application provides a calibration method and system for a gas detection lidar, which can solve the problem of poor accuracy in calibrating the gas detection lidar. The technical solutions are as follows:

[0005] In a first aspect, a calibration method for a gas detection lidar is provided. The method includes:

[0006] Obtain the first echo signal intensity and the second echo signal intensity of the lidar to be processed; wherein, the first echo signal intensity is detected by using an auxiliary calibration device and the lidar to be processed, and the light receiving and transmitting optical path of the auxiliary calibration device meets the preset receiving and transmitting field of view conditions; the time interval between the detection time of the first echo signal intensity and the detection time of the second echo signal intensity is less than a preset time threshold, and the distance between the detection position of the first echo signal intensity and the detection position of the second echo signal intensity is less than a preset distance threshold;

[0007] Based on the first echo signal intensity and the second echo signal intensity, use a preset calibration algorithm to obtain target calibration parameters;

[0008] Based on the target calibration parameters, use a preset influence value algorithm to determine the lidar system efficiency influence value;

[0009] Based on the lidar system efficiency influence value, perform calibration processing on the lidar to be processed to obtain a calibrated lidar.

[0010] In a possible implementation manner, the obtaining of the first echo signal intensity of the lidar to be processed includes:

[0011] The lidar to be processed emits a first laser to the auxiliary calibration device;

[0012] The auxiliary calibration device performs a first detection process on the atmosphere based on the first laser to obtain the intensity of the first echo signal.

[0013] Obtain the intensity of the first echo signal of the lidar to be processed from the auxiliary calibration device.

[0014] In a possible implementation, the auxiliary calibration device includes a beam integration module, an echo reception module, and a signal processing module. The auxiliary calibration device performs a first detection process on the atmosphere based on the first laser to obtain the intensity of the first echo signal, including:

[0015] The beam integration module receives the first laser emitted by the lidar to be processed;

[0016] The beam integration module performs adjustment processing on the received first laser to obtain the adjusted first echo light, and sends the first echo light to the echo reception module;

[0017] The echo reception module performs conversion processing on the received first echo light to obtain a first electrical signal, and sends the first electrical signal to the signal processing module;

[0018] The signal processing module performs calculation processing on the first electrical signal to obtain the intensity of the first echo signal.

[0019] In a possible implementation, obtaining the intensity of the second echo signal of the lidar to be processed includes:

[0020] The lidar to be processed emits a second laser vertically upward;

[0021] The lidar to be processed performs a second detection process on the atmosphere based on the second laser to obtain the intensity of the second echo signal;

[0022] Obtain the intensity of the second echo signal from the lidar to be processed.

[0023] In a possible implementation, the lidar to be processed includes a transceiver optical path module, an optoelectronic processing module, and a data processing module. The lidar to be processed performs a second detection process on the atmosphere based on the second laser to obtain the intensity of the second echo signal, including:

[0024] The transceiver optical path module receives the second echo light returned based on the second laser;

[0025] The optical transceiver module sends the second backscattered light to the optoelectronic processing module;

[0026] The optoelectronic processing module performs conversion processing on the second backscattered light to obtain the second electrical signal, and sends the second electrical signal to the data processing module;

[0027] The optoelectronic processing module performs calculation processing on the second electrical signal to obtain the intensity of the second echo signal.

[0028] In a possible implementation manner, the intensity of the first echo signal includes the intensity of the first echo signal at the first position and the intensity of the first echo signal at the second position, the intensity of the second echo signal includes the intensity of the second echo signal at the first position and the intensity of the second echo signal at the second position, and based on the intensity of the first echo signal and the intensity of the second echo signal, using a preset calibration algorithm to obtain a target calibration parameter, including:

[0029] Based on the intensity of the first echo signal at the first position and the intensity of the first echo signal at the second position, and the intensity of the second echo signal at the first position and the intensity of the second echo signal at the second position, using a preset calibration algorithm to calculate the calibration parameter;

[0030] Take the calibration parameter as the target calibration parameter.

[0031] In a possible implementation manner, the target calibration parameter includes target calibration parameters of at least two wavelengths, and based on the target calibration parameter, using a preset influence value algorithm to determine the influence value of the lidar system efficiency, including:

[0032] Obtain the target calibration parameter of the first wavelength and the target calibration parameter of the second wavelength;

[0033] Based on the target calibration parameter of the first wavelength and the target calibration parameter of the second wavelength, using a preset influence value algorithm to calculate the influence value of the lidar system efficiency.

[0034] In a possible implementation manner, the preset transceiver field-of-view condition may include that the receiving diameter of the receiving field-of-view is greater than the transmitting spot diameter of the transmitting field-of-view, and the receiving field-of-view angle is greater than the sum of the transmitting field-of-view angle and a preset coefficient, and the preset coefficient is determined based on the angle between the optical axis of the receiving field-of-view and the optical axis of the transmitting field-of-view.

[0035] In a second aspect, a calibration system for a gas detection lidar is provided, and the calibration system includes: an auxiliary calibration device, a lidar to be processed, and a data processing device; the data processing device is respectively communicatively connected to the auxiliary calibration device and the lidar to be processed;

[0036] The auxiliary calibration device is used to detect the intensity of the first echo signal based on the laser sent by the lidar to be processed received;

[0037] The lidar to be processed is used to detect the intensity of the second echo signal;

[0038] The data processing device is used to execute the calibration method of the gas detection lidar in the above-mentioned aspects and any possible implementation manners.

[0039] In a possible implementation manner, the auxiliary calibration device includes a beam integration module, an echo receiving module, and a signal processing module;

[0040] The beam integration module is used to control the center of the emission spot in the emission field of view to coincide with the center of the reception field of view;

[0041] The echo receiving module is used to control the reception field of view angle and the emission field of view angle to meet the preset field of view angle condition, and the reception field of view diameter and the emission field of view diameter to meet the preset length condition;

[0042] The signal processing module is used to calculate and store the intensity of the first echo signal.

[0043] In a third aspect, a computer-readable storage medium is provided. At least one instruction is stored in the storage medium, and the at least one instruction is loaded and executed by a processor to implement the methods in the above-mentioned aspects and any possible implementation manners.

[0044] In a fourth aspect, an electronic device is provided, including:

[0045] At least one processor; and

[0046] A memory communicatively connected to the at least one processor; wherein,

[0047] The memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the methods in the above-mentioned aspects and any possible implementation manners.

[0048] The beneficial effects of the technical solution provided by this application at least include:

[0049] As can be seen from the above technical solution, embodiments of the present application can obtain the first echo signal intensity and the second echo signal intensity of the lidar to be processed. Among them, the first echo signal intensity is detected by using an auxiliary calibration device and the lidar to be processed, and the light receiving and transmitting optical path of the auxiliary calibration device satisfies a preset receiving and transmitting field of view condition; the time interval between the detection time of the first echo signal intensity and the detection time of the second echo signal intensity is less than a preset time threshold, and the distance between the detection position of the first echo signal intensity and the detection position of the second echo signal intensity is less than a preset distance threshold. Furthermore, based on the first echo signal intensity and the second echo signal intensity, a target calibration parameter can be obtained by using a preset calibration algorithm. Based on the target calibration parameter, a system efficiency influence value of the lidar to be processed can be determined by using a preset influence value algorithm. Based on the system efficiency influence value of the lidar to be processed, a calibrated lidar can be obtained. Since the target calibration parameter of the lidar can be determined by detecting the first echo signal intensity of the lidar to be processed using an auxiliary calibration device and the second echo signal intensity detected by the lidar to be processed itself, the accuracy of the calibration parameter can be improved, and the inversion result of the gas concentration can be better corrected, that is, a system efficiency influence value with higher accuracy can be obtained, improving the inversion accuracy of the gas concentration, thereby ensuring the detection accuracy and reliability of the gas detection lidar.

[0050] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained without creative efforts based on these drawings.

[0052] Figure 1 is a schematic flowchart of a calibration method for a gas detection lidar provided by an embodiment of the present application;

[0053] Figure 2 is a schematic architecture diagram of a calibration system for a gas detection lidar provided by an embodiment of the present application;

[0054] Figure 3 is a schematic diagram of the process of a calibration method for a gas detection lidar provided by an embodiment of the present application;

[0055] Figure 4It is a schematic diagram of an application scenario of a calibration method for a gas detection lidar provided by an embodiment of the present application;

[0056] Figure 5 It is a schematic diagram of the transceiver field of view of an auxiliary calibration device for a calibration method of a gas detection lidar provided by an embodiment of the present application;

[0057] Figure 6 It is a schematic diagram of the structure of an auxiliary calibration device for a calibration method of a gas detection lidar provided by an embodiment of the present application;

[0058] Figure 7 It is a schematic diagram of the structure of another auxiliary calibration device for a calibration method of a gas detection lidar provided by another embodiment of the present application. Detailed implementation manners

[0059] The following describes exemplary embodiments of the present application with reference to the accompanying drawings. Various details of the embodiments of the present application are included to facilitate understanding, and they should be considered merely exemplary. Therefore, those of ordinary skill in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, for clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description.

[0060] Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts fall within the scope of protection of the present application.

[0061] It should be noted that the hardware observation device terminals involved in the embodiments of the present application may include, but are not limited to, devices in meteorological observation stations such as receivers, integrated processors, remote control devices, and base measurement boxes.

[0062] In addition, the term "and / or" in this article is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0063] A gas detection lidar, that is, a gas component concentration detection lidar, means that the lidar emits pulsed light into the atmosphere, and measures the gas components by collecting the backscattered light of the pulsed light by atmospheric molecules and aerosols. Atmospheric molecules include nitrogen, oxygen, carbon dioxide, water vapor, ozone, etc., and aerosols include dust, fine particulate matter, etc. Atmospheric molecules and aerosols will absorb and scatter pulsed laser light. Assume that the pulsed energy emitted by the lidar is , the height received by the lidar At, the thickness is The intensity of the backscattered pulse echo signal Is shown in formula (1):

[0064]

[0065] Among them, Is the lidar system efficiency, including factors such as the matching degree of the transceiver field of view, transmission efficiency, reception efficiency, and optoelectronic conversion efficiency. Is the Planck constant, Is the speed of light, Is the laser wavelength, Is the atmospheric backscattering coefficient, Is the atmospheric extinction coefficient, Is the pulse energy emitted by the lidar, Is the detection height, Is the detection range resolution (obtain an echo signal value every such a distance).

[0066] Here, the atmospheric backscattering coefficient Represents the atmospheric backscattering ability of light, which is related to the total concentration of atmospheric molecules, aerosol concentration, and laser wavelength. Generally, the gas to be measured accounts for a small proportion of the total amount of atmospheric molecules, and its concentration change has little impact on the total concentration of atmospheric molecules. Therefore, the impact on the atmospheric backscattering coefficient can be basically ignored, and the backscattering coefficient does not change with the concentration of the gas to be measured. However, the gas has a characteristic absorption effect. When the wavelength of the laser pulse is in the characteristic absorption band of the gas to be measured, the gas to be measured has a strong absorption ability for the laser, and the impact of the concentration of the gas to be measured on the atmospheric extinction coefficient cannot be ignored. Usually, the absorption cross-section Is used to represent the absorption ability of the unit gas for the laser. Generally, the higher the gas concentration, the stronger the absorption ability. Therefore, the atmospheric extinction coefficient at any wavelength can be expressed as formula (2):

[0067]

[0068] Among them, Is the extinction coefficient after removing the gas to be measured, Is the absorption cross-section of the gas to be measured at the wavelength At, Is the concentration of the gas to be measured. Therefore, formula (1) can be rewritten as formula (3)

[0069]

[0070] During the process of gas concentration detection, lidar usually emits one or more sets of laser pulses with different wavelengths into the atmosphere. Here, taking the emission of one set of laser pulses with different wavelengths as an example, assume that the emission wavelengths and pulse energies are respectively and and and . The echo signal intensities at at the wavelengths of and are expressed by Formulas (4) and (5):

[0071]

[0072]

[0073] Here, Formulas (4) and (5) can be simplified, and combined with the echo signal intensities at different wavelengths at , it can be calculated that

[0074]

[0075]

[0076]

[0077]

[0078] Among them, A can represent the influence of the echo signal intensity on the inversion of the concentration of the gas to be measured, B can represent the influence of the lidar system efficiency on the inversion of the concentration of the gas to be measured, that is, the system efficiency influence value, and C can represent the influence of the change of the atmospheric components (except the gas to be measured) on the inversion of the concentration of the gas to be measured. Among them, the inversion accuracy can be improved by correcting item B, that is, determining the change amount of the system efficiency with distance .

[0079] Generally, the emission efficiency, reception efficiency, and photoelectric conversion efficiency do not vary with distance. The change in system efficiency is caused by the change in the matching degree of the transceiver fields of view. When the reception field of view can always cover the emission field of view, the system efficiency remains unchanged. However, the optical path of lidar mainly has two forms: coaxial transceiver and non-coaxial transceiver. On the one hand, in order to ensure the emission efficiency, coaxial transceiver lidar generally adopts the form of central hole punching. Specifically, light is emitted from the internal "hole", and after being reflected by the atmosphere, it is received through the external "ring". The optical reception position is equivalent to the external "ring"-type receiving lens, and the optical emission position is equivalent to the internal "hole"-type emitting lens. The reception position cannot cover the emission position. Therefore, even if the reception field of view angle is greater than the emission field of view angle, the reception field of view cannot cover the emission field of view within the entire detection range, resulting in a change in system efficiency with the change of distance. On the other hand, in the non-coaxial transceiver structure, the reception field of view also cannot cover the emission field of view within the entire detection range, resulting in a change in system efficiency with the change of distance.

[0080] In traditional gas detection lidar, the horizontal detection method is usually adopted to determine the change amount of system efficiency with distance. . Specifically, a mechanical or optical mechanism can be used to horizontally emit the detection beam, and it is defaulted that the atmosphere is uniform in this direction, and the backscattering coefficient and extinction coefficient are both constants. According to the echo signal intensity in formula (1), the change amount of system efficiency can be deduced.

[0081] However, this method has two main defects. First, the detection process requires an extremely open experimental site, and the horizontal distance should be greater than two kilometers. Second, the uniform atmosphere in the horizontal direction is an ideal condition, and there are large errors in the actual detection process.

[0082] Therefore, there is an urgent need for a calibration method for gas detection lidar that can accurately determine the change amount of system efficiency with distance, so as to ensure the accuracy and reliability of gas detection lidar calibration.

[0083] Please refer to Figure 1 , which shows a schematic flow chart of the calibration method for gas detection lidar provided by an embodiment of the present application. The calibration method for gas detection lidar can specifically include:

[0084] Step 101: Obtain the first echo signal intensity and the second echo signal intensity of the lidar to be processed; wherein, the first echo signal intensity is detected by using an auxiliary calibration device and the lidar to be processed, and the light emitting and receiving optical path of the auxiliary calibration device meets the preset transmitting and receiving field of view conditions; the time interval between the detection time of the first echo signal intensity and the detection time of the second echo signal intensity is less than a preset time threshold, and the distance between the detection position of the first echo signal intensity and the detection position of the second echo signal intensity is less than a preset distance threshold.

[0085] Step 102: Based on the first echo signal intensity and the second echo signal intensity, use a preset calibration algorithm to obtain target calibration parameters.

[0086] Step 103: Based on the target calibration parameters, use a preset influence value algorithm to determine the lidar system efficiency influence value.

[0087] Step 104: Based on the lidar system efficiency influence value, perform calibration processing on the lidar to be processed to obtain a calibrated lidar.

[0088] It should be noted that the target calibration parameter can be the variation of the lidar system efficiency with distance. The system efficiency influence value can be the influence of the lidar system efficiency on the inversion of the concentration of the gas to be measured, that is, the influence value of the lidar system efficiency on the inversion of the concentration of the gas to be measured.

[0089] It should be noted that the lidar to be processed can be a gas detection lidar to be calibrated. The gas detection lidar can include a lidar for detecting different gases in the atmosphere.

[0090] It should be noted that the first echo signal intensity can include the echo signal intensities at at least two wavelengths. The second echo signal intensity can also include the echo signal intensities at at least two wavelengths.

[0091] It should be noted that the first echo signal intensity can be detected by using an auxiliary calibration device and the lidar to be processed. The second echo signal intensity can be directly detected by using the lidar to be processed.

[0092] It can be understood that before the detection process, the device working parameters of the lidar to be processed and its corresponding auxiliary calibration device can be pre-configured according to the requirements of the actual detection scenario.

[0093] It should be noted that the preset time threshold and the preset distance threshold can be determined according to the actual application scenario. For example, the preset time threshold can be 3 minutes, and the preset distance threshold can be 3 meters. Here, based on the interval between the detection time of the first echo signal intensity and the detection time of the second echo signal intensity being less than the preset time threshold, and the distance between the detection position of the first echo signal intensity and the detection position of the second echo signal intensity being less than the preset distance threshold, it can be ensured that the atmospheric extinction coefficient and the backscattering coefficient involved in the first echo signal intensity and the second echo signal intensity are the same value.

[0094] In this way, by using the first echo signal intensity of the lidar to be processed detected by the auxiliary calibration device and the second echo signal intensity detected by the lidar to be processed itself, the target calibration parameters of the lidar can be determined, which can improve the accuracy of the calibration parameters, better correct the inversion result of the gas concentration, that is, obtain a system efficiency influence value with higher precision, improve the inversion accuracy of the gas concentration, and thus ensure the detection accuracy and reliability of the gas detection lidar.

[0095] Optionally, in a possible implementation manner of this embodiment, in step 101, first, the lidar to be processed may emit a first laser to the auxiliary calibration device. Secondly, the auxiliary calibration device performs a first detection process on the atmosphere based on the first laser to obtain the first echo signal intensity. Thirdly, the first echo signal intensity of the lidar to be processed is obtained from the auxiliary calibration device.

[0096] In this implementation manner, the auxiliary calibration device may include a beam integration module, an echo reception module, and a signal processing module.

[0097] In a specific implementation process of this implementation manner, first, the beam integration module receives the first laser emitted by the lidar to be processed. Secondly, the beam integration module performs adjustment processing on the received first laser to obtain the adjusted first echo light, and sends the first echo light to the echo reception module. Thirdly, the echo reception module performs conversion processing on the received first echo light to obtain a first electrical signal, and sends the first electrical signal to the signal processing module. Thirdly, the signal processing module performs calculation processing on the first electrical signal to obtain the first echo signal intensity.

[0098] Exemplarily, first, the gas detection lidar to be calibrated can emit a first laser to the auxiliary calibration device. This first laser can be referred to as the incident light. The incident light is sent to the high-altitude atmosphere as detection light vertically through the beam integration module. After the detection light undergoes atmospheric extinction and backscattering, echo light is generated. The echo light enters the echo receiving module after passing through the beam integration module. In the echo receiving module, the optical signal of the echo light can be converted into an electrical signal and sent to the signal processing module. The signal processing module can calculate the intensity of the first echo signal varying with height and can perform processing such as detection and storage on the received electrical signal.

[0099] In this implementation, the beam integration module can control the center of the emission spot of the emission field of view to coincide with the center of the reception field of view. The echo receiving module can control the reception field of view angle and the emission field of view angle to meet the preset field of view angle condition, and the reception field of view diameter and the emission field of view diameter to meet the preset length condition.

[0100] Preferably, the preset field of view angle condition can include that the reception field of view angle is greater than the sum of the emission field of view angle and twice the angle between the reception and emission optical axes, and the angle between the reception and emission optical axes can be 500 micro-radians (urad). Here, twice the angle between the reception and emission optical axes can be a preset coefficient. The preset length condition can include that the reception diameter of the reception field of view is greater than the emission spot diameter of the emission field of view.

[0101] Here, the beam integration system can be used to achieve the coincidence of the center of the emission spot and the center of the effective reception area, and the echo receiving system can be used to achieve the emission spot diameter of the emission field of view and the effective reception diameter of the reception field of view should satisfy , the reception field of view angle should be greater than the emission field of view angle , satisfy , is the angle between the reception and emission optical axes, is 500 urad, so that the reception field of view can cover the emission field of view.

[0102] In this way, by using the auxiliary calibration device that meets the preset reception and emission field of view conditions, the laser emitted by the lidar to be processed can be adjusted to obtain the electrical signal of the light whose reception field of view can cover the emission field of view. Furthermore, a more accurate first echo signal intensity can be obtained, so as to further improve the reliability of the subsequent calibration.

[0103] Optionally, in a possible implementation manner of this embodiment, in step 101, first, the lidar to be processed emits a second laser vertically upward. Secondly, the lidar to be processed performs a second detection process on the atmosphere based on the second laser to obtain the second echo signal intensity. Thirdly, the second echo signal intensity is obtained from the lidar to be processed.

[0104] In this implementation manner, the lidar to be processed may include a transceiver optical path module, an optoelectronic processing module, and a data processing module.

[0105] Here, the transceiver optical path module, the optoelectronic processing module, and the data processing module may be disposed inside the lidar to be processed.

[0106] In a specific implementation process of this implementation manner, first, the transceiver optical path module receives the second echo light returned based on the second laser. Secondly, the transceiver optical path module sends the second echo light to the optoelectronic processing module. Thirdly, the optoelectronic processing module performs a conversion process on the second echo light to obtain the second electrical signal, and sends the second electrical signal to the data processing module. Thirdly, the optoelectronic processing module performs a calculation process on the second electrical signal to obtain the second echo signal intensity.

[0107] Here, the direction in which the lidar to be processed emits laser pulses is vertically upward, so that the deviation between the emission optical axis and the vertical direction can be further reduced.

[0108] It should be noted that the specific implementation process provided in this implementation manner can be combined with the multiple specific implementation processes provided in the foregoing implementation manner to implement the calibration method of the gas detection lidar in this embodiment. For a detailed description, reference can be made to the relevant content in the foregoing implementation manner, which will not be elaborated here.

[0109] Optionally, in a possible implementation manner of this embodiment, the first echo signal intensity may include the first echo signal intensity at the first position and the first echo signal intensity at the second position, and the second echo signal intensity may include the second echo signal intensity at the first position and the second echo signal intensity at the second position. In step 102, based on the first echo signal intensity at the first position and the first echo signal intensity at the second position, and the second echo signal intensity at the first position and the second echo signal intensity at the second position, a calibration parameter can be calculated using a preset calibration algorithm, and then the calibration parameter can be used as the target calibration parameter.

[0110] In this implementation manner, the first position may represent the position of the laser detection height and the second position may represent the position of the laser detection height Plus the detection distance resolution corresponding to the acquisition period position.

[0111] In a specific implementation process of this implementation manner, first, the ratio of the first echo signal intensity at the first position to the first echo signal intensity at the second position can be calculated to obtain a first ratio. Secondly, the ratio of the second echo signal intensity at the first position to the second echo signal intensity at the second position is calculated to obtain a second ratio. Thirdly, the ratio of the first ratio to the second ratio is calculated to obtain a calibration parameter, that is, the target calibration parameter.

[0112] Here, the target calibration parameter can be the change amount of the system efficiency of the lidar to be calibrated with height.

[0113] It can be understood that here, the first echo signal intensity and the second echo signal intensity of lasers with different wavelengths can be detected. Here, the target calibration parameter can include the calibration parameters of lasers with different wavelengths.

[0114] In this way, by comparing the first echo signal intensity at the first position with the first echo signal intensity at the second position, and the second echo signal intensity at the first position with the second echo signal intensity at the second position, a more accurate and effective target calibration parameter can be calculated.

[0115] It should be noted that the specific implementation process provided in this implementation manner can be combined with various specific implementation processes provided in the foregoing implementation manner to implement the calibration method of the gas detection lidar in this embodiment. For a detailed description, reference can be made to the relevant content in the foregoing implementation manner, which will not be elaborated here.

[0116] Optionally, in a possible implementation manner of this embodiment, the target calibration parameter includes target calibration parameters of at least two wavelengths. In step 103, first, the target calibration parameter of the first wavelength and the target calibration parameter of the second wavelength are obtained. Secondly, based on the target calibration parameter of the first wavelength and the target calibration parameter of the second wavelength, the lidar system efficiency influence value can be calculated by using a preset influence value algorithm.

[0117] In this implementation manner, the target calibration parameters of different wavelengths can be the target calibration parameters corresponding to lasers of different wavelengths. The target calibration parameter of the first wavelength can be the target calibration parameter corresponding to the first wavelength laser. The target calibration parameter of the second wavelength can be the target calibration parameter corresponding to the second wavelength laser.

[0118] In a specific implementation process of this implementation manner, the preset influence value algorithm can be as shown in formula (8). Specifically, based on the target calibration parameter of the first wavelength and the target calibration parameter of the second wavelength, the lidar system efficiency influence value can be calculated by using formula (8).

[0119] Here, the system efficiency influence value of the lidar to be processed can represent the influence of the lidar system efficiency on the inversion of the concentration of the gas to be measured.

[0120] It can be understood that the calculated lidar system efficiency influence value can be used as the system efficiency influence value of the lidar to be processed, and the calibration process of the lidar to be processed can be completed.

[0121] In this way, the lidar system efficiency influence value can be calculated by using the preset influence value algorithm with the target calibration parameters corresponding to any two wavelengths, which can improve the accuracy of the lidar system efficiency influence value.

[0122] It should be noted that the specific implementation process provided in this implementation manner can be combined with the various specific implementation processes provided in the foregoing implementation manner to implement the calibration method of the gas detection lidar in this embodiment. For a detailed description, reference can be made to the relevant content in the foregoing implementation manner, which will not be elaborated here.

[0123] Optionally, in a possible implementation manner of this embodiment, the preset transceiver field of view conditions may include that the receiving diameter of the receiving field of view is greater than the transmitting spot diameter of the transmitting field of view, and the receiving field of view angle is greater than the sum of the transmitting field of view angle and a preset coefficient, where the preset coefficient is determined based on the angle between the optical axis of the receiving field of view and the optical axis of the transmitting field of view.

[0124] In this implementation manner, the preset transceiver field of view conditions may include a preset field of view angle condition and a preset length condition. The preset coefficient may be twice the angle between the receiving and transmitting optical axes.

[0125] Preferably, the preset field of view angle condition may include that the receiving field of view angle is greater than the sum of the transmitting field of view angle and twice the angle between the receiving and transmitting optical axes, and the angle between the receiving and transmitting optical axes may be 500 urad. The preset length condition may include that the receiving diameter of the receiving field of view is greater than the transmitting spot diameter of the transmitting field of view.

[0126] Here, the receiving diameter of the receiving field of view may be the effective receiving diameter of the receiving field of view.

[0127] In this implementation manner, the preset transceiver field of view conditions may further include that the center of the transmitting spot of the transmitting field of view coincides with the center of the receiving field of view.

[0128] Here, the center of the receiving field of view may be the center of the effective receiving area of the receiving field of view.

[0129] It can be understood that the beam integration module of the auxiliary calibration device can achieve the coincidence of the center of the emission spot in the emission field of view and the center of the reception field of view. The echo reception module of the auxiliary calibration device can achieve controlling the reception field of view angle and the emission field of view angle to meet the preset field of view angle conditions, and the reception field of view diameter and the emission field of view diameter to meet the preset length conditions.

[0130] In this way, it can be ensured that the light emission and reception optical paths of the auxiliary calibration device can meet the preset light emission and reception field of view conditions, and it can be ensured that the reception field of view of the auxiliary calibration device can cover the emission field of view. Furthermore, the first echo signal intensity calculated based on the auxiliary calibration device can be used to determine more accurate target calibration parameters.

[0131] It should be noted that the specific implementation process provided in this implementation manner can be combined with the various specific implementation processes provided in the foregoing implementation manner to implement the calibration method of the gas detection lidar in this embodiment. For a detailed description, reference can be made to the relevant content in the foregoing implementation manner, which will not be elaborated here.

[0132] Figure 2 The schematic diagram of the architecture of the calibration system of the gas detection lidar provided by an embodiment of the present application is shown as Figure 2 shown.

[0133] In this embodiment, the calibration system of the gas detection lidar may include an auxiliary calibration device, a lidar to be processed, and a data processing device. The data processing device is communicatively connected to the auxiliary calibration device and the lidar to be processed respectively. The auxiliary calibration device is used to detect the first echo signal intensity based on the laser light transmitted by the lidar to be processed received. The lidar to be processed is used to detect the second echo signal intensity. The data processing device is used to execute the calibration method of the gas detection lidar as described in the foregoing embodiment.

[0134] Optionally, in a possible implementation manner of this embodiment, the auxiliary calibration device may include a beam integration module, an echo reception module, and a signal processing module.

[0135] Preferably, the beam integration module can be used to control the coincidence of the center of the emission spot in the emission field of view and the center of the reception field of view.

[0136] The echo reception module can be used to control the reception field of view angle and the emission field of view angle to meet the preset field of view angle conditions, and the reception field of view diameter and the emission field of view diameter to meet the preset length conditions.

[0137] The signal processing module can be used to calculate and store the first echo signal intensity.

[0138] Preferably, the preset transceiver field-of-view conditions may include a preset field-of-view angle condition and a preset length condition.

[0139] Preferably, the preset field-of-view angle condition may include that the receiving field-of-view angle is greater than the sum of the transmitting field-of-view angle and a preset coefficient, and the preset coefficient may be twice the angle between the receiving and transmitting optical axes. For example, the angle between the receiving and transmitting optical axes may be 500 urad. The preset length condition may include that the receiving diameter of the receiving field-of-view is greater than the transmitting spot diameter of the transmitting field-of-view.

[0140] In this embodiment, a set of echo signal data can be obtained by using the auxiliary calibration device of the calibration system, and the data processing device is used to perform differential processing on the echo signal data and the echo signal data of the gas detection lidar to be calibrated, so as to obtain a more accurate change amount of the efficiency of the gas detection lidar system to be calibrated with distance, improve the influence value of the lidar system efficiency on the inversion of the concentration of the gas to be measured, and thus invert more accurate gas concentration data.

[0141] To better illustrate the calibration method of the gas detection lidar in this application, in combination with the calibration system and application scenarios of the gas detection lidar, the calibration method of the gas detection lidar will be described in detail.

[0142] Figure 3 The schematic diagram of the flow of the calibration method of the gas detection lidar provided by another embodiment of this application is shown, as Figure 3 shown. In this embodiment, the calibration method of the gas detection lidar can be specifically implemented as the following steps:

[0143] Step 301: The gas detection lidar to be calibrated emits a first laser to the auxiliary calibration device.

[0144] In this implementation, before calibration, first, the working parameters of the gas detection lidar to be calibrated can be determined. The working parameters may include laser wavelength, energy, spot size, field-of-view angle, etc. Secondly, according to the working parameters of the gas detection lidar to be calibrated, the component specifications in the auxiliary calibration device are adjusted so that the receiving field-of-view of the auxiliary calibration device can cover the transmitting field-of-view, and the work of echo signal detection is completed.

[0145] Step 302: The beam integration module of the auxiliary calibration device receives the first laser, performs adjustment processing on the received first laser to obtain the adjusted first echo light, and sends the first echo light to the echo receiving module of the auxiliary calibration device.

[0146] Step 303: The echo receiving module of the auxiliary calibration device performs conversion processing on the first echo light of the gas detection lidar to be calibrated received, to obtain a first electrical signal, and sends the first electrical signal of the gas detection lidar to be calibrated to the signal processing module of the auxiliary calibration device.

[0147] Step 304: The signal processing module of the auxiliary calibration device performs calculation processing on the first electrical signal of the gas detection lidar to be calibrated, to obtain the first echo signal intensity.

[0148] Step 305: The gas detection lidar to be calibrated emits a second laser vertically upward, to perform a second detection process on the atmosphere based on the second laser of the gas detection lidar to be calibrated, and obtain a second echo signal intensity.

[0149] In this embodiment, the auxiliary calibration device may include a beam integration module, an echo receiving module, and a signal processing module. The auxiliary calibration device may be an auxiliary calibration device.

[0150] In this embodiment, the emission pulse direction of the gas detection lidar to be calibrated is vertically upward. In this way, the deviation between the emission optical axis and the vertical direction can be minimized as much as possible.

[0151] Figure 4 The figure shows a schematic diagram of an application scenario of a calibration method for a gas detection lidar provided in another embodiment of the present application, as Figure 4 shown. This application scenario includes a gas detection lidar to be calibrated and an auxiliary calibration device. The auxiliary calibration device includes a beam integration module, an echo receiving module, and a signal processing module.

[0152] In this embodiment, by way of example, as Figure 4 shown, first, the gas detection lidar to be calibrated emits a first laser to the auxiliary calibration device. This first laser may be referred to as incident light. After passing through the beam integration module, the incident light vertically sends detection light to the upper atmosphere. After the detection light undergoes atmospheric extinction and backscattering effects, echo light is generated. The echo light enters the echo receiving module after passing through the beam integration module. In the echo receiving module, the optical signal of the echo light can be converted into an electrical signal and transmitted to the signal processing module for calculation, detection, storage, and other processing, and the first echo signal intensity varying with height can be calculated. Here, before detection, time synchronization processing can be performed on the signal processing modules of the gas detection lidar to be calibrated and the auxiliary calibration device.

[0153] Secondly, the auxiliary calibration device of the lidar can be removed, and the gas detection lidar to be calibrated is used to directly emit a second laser vertically. Using the self-emission and reception optical path module, photoelectric processing module, and data processing module of the gas detection lidar to be calibrated, another set of echo signal intensities varying with height can be calculated.

[0154] Here, the test positions and test times of the gas detection lidar to be calibrated and the auxiliary calibration device are close during the test. The test time interval can be less than 3 minutes, and the distance between the test positions can be less than 3 meters. Therefore, among the two sets of first echo signal intensities and second echo signal intensities, the atmospheric extinction coefficient and the backscattering coefficient at different heights can be considered as the same value. According to formula (1), the following formulas (10) and (11) can be obtained:

[0155]

[0156]

[0157] Among them, is the first echo signal intensity, is the second echo signal intensity, is the system efficiency under the use of the auxiliary calibration device, is the system efficiency of the gas detection lidar to be calibrated, is the pulse energy emitted by the gas detection lidar to be calibrated, is the loss of the light receiving and emitting optical path of the auxiliary calibration device. is the Planck constant, is the speed of light, is the laser wavelength, is the atmospheric backscattering coefficient, is the atmospheric extinction coefficient, is the detection height, is the detection distance resolution.

[0158] It can be understood that is determined by the acquisition time interval of the signal collector. For example, when the acquisition time interval is 50 nanoseconds (ns), the corresponding distance at the speed of light is 15 meters (m). There is light return during detection, and the corresponding detection distance resolution at this time is 7.5 m. Among them, the signal collector can be set in the signal processing module of the gas detection lidar to be calibrated. At the same time, the signal collector can also be set in the signal processing module of the auxiliary calibration device.

[0159] Furthermore, formulas (10) and (11) can be simplified, and combined with the number of echo photons at, that is the echo signal intensity at, formula (12) can be obtained:

[0160]

[0161] Here, since the receiving field of view of the auxiliary calibration device can cover the transmitting field of view. Therefore, the system efficiency parameter is a constant and does not change with height. Thus, the change in the system efficiency of the gas detection lidar to be calibrated with height can be obtained, that is, the target calibration parameter , which can be expressed by formula (13):

[0162]

[0163] Wherein, is the echo signal intensity at the position in the first echo signal intensity, that is, the first echo signal intensity at the first position, is the echo signal intensity at the position in the first echo signal intensity, that is, the first echo signal intensity at the second position, is the echo signal intensity at the position in the second echo signal intensity, that is, the second echo signal intensity at the first position, is the echo signal intensity at the position in the second echo signal intensity, that is, the second echo signal intensity at the second position.

[0164] Step 306, the data processing device obtains the first echo signal intensity and the second echo signal intensity.

[0165] Step 307, the data processing device calculates the target calibration parameter based on the first echo signal intensity and the second echo signal intensity of the gas detection lidar to be calibrated, using a preset calibration algorithm.

[0166] In this embodiment, the data processing device calculates the target calibration parameter based on the first echo signal intensity and the second echo signal intensity of the gas detection lidar to be calibrated, using the preset calibration algorithm shown in formula (13) .

[0167] It can be understood that, first, the first echo signal intensity and the second echo signal intensity of multiple wavelength lasers can be obtained. Second, based on the first echo signal intensity and the second echo signal intensity of each wavelength laser respectively, the target calibration parameter of each wavelength laser is calculated using the preset calibration algorithm shown in formula (13).

[0168] Step 308, the data processing device calculates the lidar system efficiency influence value based on the target calibration parameter of the gas detection lidar to be calibrated, using a preset influence value algorithm.

[0169] In this embodiment, the target calibration parameter may include the target calibration parameters of different wavelengths. For example, the target calibration parameter of the gas detection lidar to be calibrated may include the target calibration parameter of the first wavelength and the target calibration parameter of the second wavelength.

[0170] Here, the target calibration parameters of the first wavelength and the target calibration parameters of the second wavelength can be obtained, and the influence value of the laser radar system efficiency can be calculated using the preset influence value algorithm shown in formula (8).

[0171] Step 309: Use the laser radar system efficiency impact value as the system efficiency impact value of the gas detection laser radar to be calibrated to obtain the gas detection laser radar after calibration.

[0172] In this embodiment, the light transmission and light transmission path of the auxiliary calibration device should meet the preset transmission and reception field of view conditions. The preset transmission and reception field of view conditions may include that the transmission spot diameter of the transmission field of view is smaller than the receiving diameter of the receiving field of view, the transmission spot center of the transmission field of view coincides with the center of the receiving field of view, and the receiving field of view angle is greater than the sum of the transmission field of view angle and the preset coefficient. The preset coefficient of the gas detection laser radar to be calibrated is determined based on the angle between the optical axis of the receiving field of view and the optical axis of the transmission field of view.

[0173] In this embodiment, illustratively, Figure 5 A schematic diagram of the receiving and transmitting field of view of an auxiliary calibration device of a gas detection laser radar calibration method provided in another embodiment of the present application is shown. Figure 5 The light receiving and transmitting path of the auxiliary calibration equipment can meet the following two conditions, namely the preset receiving and transmitting field conditions: 1. The diameter of the transmitting light spot in the transmitting field Receiving diameter and receiving field of view Should meet , and the center points coincide; 2. Receiving field of view Should be larger than the launch field of view ,satisfy , is the angle between the receiving and transmitting optical axes, Smaller, for example, It can be 500urad. In this way, the purpose of the receiving field of view of the auxiliary calibration device covering the transmitting field of view can be achieved.

[0174] In addition, it can be understood that the auxiliary calibration device can be implemented using a variety of structures.

[0175] For example, Figure 6 A schematic diagram showing the structure of an auxiliary calibration device for a calibration method of a gas detection laser radar provided in another embodiment of the present application is shown. Figure 6As shown. The lidar 1 to be calibrated can be a lidar for gas detection to be calibrated. The emission pulse direction of the lidar 1 to be calibrated is vertically upward to reduce the deviation between the emission optical axis and the vertical direction. The beam integration system 3 can be the beam integration module of the auxiliary calibration device, the echo receiving system 4 can be the echo receiving module of the auxiliary calibration device, and the echo receiving system 5 can be the signal processing module 5 of the auxiliary calibration device. The beam integration system 3 can include a light-transmitting small hole 31, a beam splitter 32, and an extinction chamber 33. The echo receiving system 4 can include a receiving lens group 41, a filter 42, and a photoelectric converter 43.

[0176] Here, the transmission-reflection ratio of the beam splitter 32 can be 1:1. The horizontal laser is incident on the beam splitter 32 at an angle of 45°. By adjusting the relative position, the center of the light spot coincides with the center of the beam splitter 32. Part of the light is reflected to become the detection light and vertically enters the atmosphere, and part of the transmitted light enters the extinction chamber 34 and is absorbed. At the same time, the echo light can be transmitted and reflected by the beam splitter 32. The reflected part finally reaches the extinction chamber 33 and is absorbed, and the transmitted part is converged and received by the echo receiving system 4. In addition to the installation position and the transmission-reflection ratio, the beam splitter 32 has a certain area size and does not block the receiving field of view. The extinction chamber 33 can absorb the laser energy to prevent the laser from being reflected again. The signal processing system 5 is time-synchronized with the lidar 1 for gas detection to be calibrated, and detects and records the electrical signal generated by the echo light to obtain the echo signal intensity.

[0177] Preferably, the main function of the receiving lens group 41 is to shape the receiving field of view. The echo light is converged onto the photoelectric converter by the receiving lens group 41. To better meet the purpose of the receiving field of view covering the emission field of view, the optical center of the receiving lens group coincides with the center of the beam splitter 32 in the vertical direction, and it is satisfied that the receiving diameter of the receiving field of view is greater than the emission light spot diameter of the emission field of view, and the receiving field of view angle is greater than the sum of the emission field of view angle and twice the angle between the receiving and emission optical axes. The angle between the receiving and emission optical axes can be small. For example, the angle between the receiving and emission optical axes can be 500 urad. The filter 42 can be a narrow-band filter to filter out the background light outside the laser wavelength. It can use a filter with a bandwidth less than 1 nm and an optical density of one in one hundred thousand. The photoelectric converter 43 can be a vacuum-type photomultiplier tube to convert and amplify the weak optical signal into an electrical signal for detection and recording.

[0178] Here, as Figure 6As shown, during the processing of the auxiliary calibration device, the incident light of the lidar 1 to be calibrated reaches the beam splitter 32 through the light-transmitting small hole 31. The beam splitter 32 is a semi-transmissive and semi-reflective mirror. Part of the incident light is reflected by the beam splitter 32 to the extinction chamber 33 and thus absorbed. Part of the incident light, after being transmitted by the beam splitter 32, is vertically incident into the atmosphere and can be called the detection light. After the detection light undergoes the extinction and backscattering effects of the atmosphere, the echo light is generated. The echo light passes through the beam splitter 32 again. Part of it is reflected to the echo receiving system 4, and part of it, after being transmitted, reaches the light-transmitting small hole 31. The small hole area of the light-transmitting small hole 31 is relatively small compared to the light-transmitting small hole 31 and has a strong absorption effect on the laser of this wavelength. Therefore, the influence of the transmitted light can be ignored. The echo receiving system 4 is composed of a receiving lens group 41, a filter 42, and a photoelectric converter 43. The receiving lens group 41 controls the size of the receiving field angle and the receiving field diameter through optical processing. The filter 42 selects a narrow-band filter to filter the background light. The photoelectric converter 43 can be a high-sensitivity photomultiplier tube, and the photoelectric converter 43 is used for the conversion processing of optical signals into electrical signals. The electrical signal is input to the signal processing system 5 for the acquisition and storage of electrical signals. Here, the beam integration system 3 can be used to make the center of the emission spot coincide with the center of the effective receiving area. The echo receiving system 4 can be used to make the receiving diameter of the receiving field greater than the emission spot diameter of the emission field, and the receiving field angle is greater than the sum of the emission field angle and twice the angle between the receiving and emission optical axes. The angle between the receiving and emission optical axes can be 500 urad, so that the receiving field can cover the emission field. Thus, when the system efficiency of the auxiliary calibration device is a constant, a set of echo signal intensity information varying with height is obtained, that is, the first echo signal intensity information.

[0179] For another example, Figure 7 shows a schematic diagram of the structure of another auxiliary calibration device for the calibration method of the gas detection lidar provided in another embodiment of the present application, as Figure 7 shown. The lidar 1 to be calibrated can be a gas detection lidar to be calibrated. The emission pulse direction of the lidar 1 to be calibrated is vertically upward to reduce the deviation between the emission optical axis and the vertical direction. The beam integration system 3 can be the beam integration module of the auxiliary calibration device, the echo receiving system 4 can be the echo receiving module of the auxiliary calibration device, and the echo receiving system 5 can be the signal processing module 5 of the auxiliary calibration device. The beam integration system 3 can include a reflector 35, a beam splitter 32, an extinction chamber 33, and an extinction chamber 34. The echo receiving system 4 can include a receiving lens group 41, a filter 42, and a photoelectric converter 43.

[0180] Here, the extinction chamber 34 can be used to absorb the laser energy and prevent the laser from being reflected again. To ensure that the laser is efficiently converted from the vertical direction to the horizontal direction, the mirror 35 can be installed with a horizontal tilt of 45°, adjust the relative position so that the center of the mirror 35 coincides with the center of the light spot, and a high-reflectivity thin film can be deposited on the surface. In addition, to reduce the intensity of the backscattered light reflected by the beam splitter 32 and then reflected back to the lidar by the mirror 35, the area of the mirror 35 can be reduced on the premise of ensuring the vertical-to-horizontal conversion efficiency.

[0181] It can be understood that the settings and uses of other components can be the same as those of the corresponding components of the Figure 6 auxiliary calibration device shown, and reference can be made to the foregoing relevant content, which will not be elaborated here.

[0182] Here, as Figure 7 shown, during the processing of the auxiliary calibration device, the to-be-calibrated lidar 1 emits laser vertically upward, which is called the incident light and enters the beam integration system 3. The incident light hits the mirror 35, and the mirror 35 is installed at an angle of 45°, which can convert the laser in the vertical direction into the laser in the horizontal direction. The surface of the mirror 35 is coated with a high-reflectivity thin film, so that the reflectivity can reach more than 95%. The beam splitter 32 partially transmits and reflects the light. When the incident light reaches the beam splitter 32, part of the light will pass through the beam splitter 32 and reach the extinction chamber 34 to be absorbed and not participate in the subsequent detection process; part of the light will be reflected by the beam splitter 32 to form vertically upward detection light. After the detection light undergoes extinction and backscattering by atmospheric molecules, backscattered light is generated. Part of the backscattered light passes through the beam splitter 32 and reaches the echo receiving system 4; part of the backscattered light is reflected by the beam splitter 32 and then reaches the extinction chamber 33 to be absorbed. Here, the presence of the mirror 35 may affect the propagation path of part of the backscattered light reaching the extinction chamber 33, but this effect can be made negligible by reducing the size of the mirror 35. The receiving lens group 41 of the echo receiving system 4 controls the size of the receiving field of view and the receiving diameter through optical processing. The filter 42 is a narrow-band filter for background light filtering, and the photoelectric converter 43 is a high-sensitivity photomultiplier for converting the optical signal into an electrical signal. The electrical signal is input to the signal processing system 5 for calculation and storage of the electrical signal.

[0183] It can be understood that, Figure 6 and Figure 7The difference in the auxiliary calibration settings lies in the different structures of the beam integration system 3, while the functions achieved by the auxiliary calibration devices are the same. The beam integration system 3 can all achieve the coincidence of the center of the emission spot and the center of the effective reception area. The echo reception system 4 can all meet the requirements that the reception diameter of the reception field of view is greater than the emission spot diameter of the emission field of view, the reception field angle is greater than the emission field angle and the sum of twice the angle between the reception and emission optical axes, and the angle between the reception and emission optical axes can be 500 urad, so that the reception field of view can cover the emission field of view. Thus, when the system efficiency corresponding to the auxiliary calibration device is a constant, a set of echo signal intensity information varying with height is obtained, that is, the first echo signal intensity information.

[0184] It can be understood that here, other existing devices that can achieve the same functions as the auxiliary calibration device in this embodiment can also be used, and the specific structure of the auxiliary calibration device may not be specifically limited herein.

[0185] In this embodiment, a set of echo signal data can be obtained by using the auxiliary calibration device, and the data is differentially processed with the echo signal data of the gas detection lidar to be calibrated, so as to obtain a more accurate variation of the system efficiency of the gas detection lidar to be calibrated with distance, improve the influence value of the lidar system efficiency on the inversion of the concentration of the gas to be measured, and thus invert more accurate gas concentration data.

[0186] In this embodiment, by way of example, an ozone lidar can be selected as the gas detection lidar to be calibrated, taking the laser with emission wavelengths of 289 nanometers (nm) and 316 nm as an example. Among them, the working parameters such as single-pulse energy, spot diameter, field of view angle, and the angle between the optical axis and the vertical direction are shown in the following table.

[0187] Single pulse energy / millijoule (mJ) Spot diameter / centimeter (cm) Field of view angle / milliradian (mrad) Optical axis included angle / mrad 289 nm 12 2 0.15 0.1 316 nm 14 1.5 0.1 0.1

[0188] Here, such as Figure 7Taking the shown auxiliary calibration device as an example, based on the working parameters of the ozone lidar, the working parameters of the corresponding auxiliary calibration device are set. Among them, the mirror 35 should be larger than the spot size, and the lens diameter can be selected as 3 cm. A highly reflective film is coated on the surface of the mirror 35 to ensure that when incident at 45°, the light in the wavelength band of 285 nm - 320 nm has a reflection efficiency higher than 95%. The relative position is adjusted so that the center of the mirror 35 coincides with the center of the spot. The beam splitter 32 is selected as a lens with a transmission-reflection ratio of 1:1 when incident at 45° in the wavelength band of 285 nm - 320 nm, and the lens diameter is selected as 10 cm. When installed, the center positions of the mirror 35 and the beam splitter 32 can coincide in the horizontal direction. The surfaces of the extinction chambers 33 and 34 in the light incident direction can be antireflection-treated, and an optical absorbent is used for optical absorption inside. The receiving lens group 41 coincides with the beam splitter 32 in the vertical center position, and the effective diameter is 8 cm. Considering the optical axis deviation and installation error, it is configured according to a field of view angle of 1 mrad. The specifications of the filter 42 are respectively selected as 289 nm ± 0.25 nm and 316 ± 0.25 nm, OD5, and OD5 can represent that in the non-selected wavelength band, the transmittance is lower than 10 to the negative fifth power. The photoelectric converter 43 can select a vacuum-type photomultiplier tube, and the multiplication wavelength covers the wavelength band of 285 nm - 320 nm. The signal processing module 5 can include a signal acquisition unit, namely a signal collector, a time synchronization unit, a data storage unit, a power supply unit, a control processing unit, etc.

[0189] Here, first, the filter 42 can be set as a filter of 289 nm ± 0.25 nm, and the signal processing modules of the ozone lidar and the auxiliary calibration device are time-synchronized. The mirror 35 is 30 cm - 50 cm from the light-emitting port on the lidar. The relative positions of the ozone lidar and the auxiliary calibration device are adjusted so that the center of the mirror 35 coincides with the center of the spot. Specifically, a spot analyzer can be used for position inspection.

[0190] Secondly, after the position adjustment is completed, the echo signal intensity at a wavelength of 289 nm is detected using the auxiliary calibration device , and then the auxiliary calibration device is immediately removed, and the echo signal intensity at a wavelength of 289 nm is detected using the ozone lidar to be calibrated . After replacing the filter with a specification of 316 ± 0.25 nm, the and at a wavelength of 316 nm are measured in the same way. According to formula (13), the change of the system efficiency of the ozone lidar to be calibrated with distance at wavelengths of 289 nm and 316 nm is calculated, that is, the target calibration parameters, as shown in the following formulas (14) and (15):

[0191]

[0192]

[0193] Among them, is the target calibration parameter at a wavelength of 289 nm, is the first echo signal intensity at a wavelength of 289 nm at position, is the first echo signal intensity at a wavelength of 289 nm at position, is the second echo signal intensity at a wavelength of 289 nm at position, is the second echo signal intensity at a wavelength of 289 nm at position, is the target calibration parameter at a wavelength of 316 nm, is the first echo signal intensity at a wavelength of 289 nm at position, is the first echo signal intensity at a wavelength of 316 nm at position, is the second echo signal intensity at a wavelength of 316 nm at position, is the second echo signal intensity at a wavelength of 316 nm at position, is the detection altitude, is the detection distance resolution.

[0194] Again, based on the variation of the system efficiency with distance at wavelengths of 289 nm and 316 nm of the ozone lidar to be calibrated, the preset influence value algorithm shown in the aforementioned formula (8) can be used to calculate the influence of the lidar system efficiency on the inversion of the concentration of the gas to be measured, that is, the system efficiency influence value.

[0195] Finally, taking this system efficiency influence value as the influence of the lidar system efficiency of this ozone lidar on the inversion of the concentration of the gas to be measured, the calibrated ozone lidar is obtained.

[0196] In this embodiment, by adopting the solution in this example, the differential processing can be performed on the two types of echo signal intensities obtained by the gas detection lidar to be calibrated and the auxiliary equipment to obtain the variation of the system efficiency, which solves the requirements of the existing horizontal direction detection scheme for a large test site, etc., and does not need to assume that the atmosphere is uniform within a long distance range, thereby reducing the test error of the detection result.

[0197] In addition, by adopting the solution in this embodiment, differential processing can be performed on the intensities of two types of echo signals obtained by the gas detection lidar to be calibrated and the auxiliary equipment, and the change amount of the system efficiency can be obtained. While simplifying the test site, the convenience of calibration is also improved.

[0198] In addition, by adopting the solution in this embodiment, a system efficiency change amount with higher accuracy can be obtained, so as to better correct the inversion result and improve the inversion accuracy of the gas concentration.

[0199] It should be noted that for the foregoing embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that this application is not limited by the described action sequence, because according to this application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0200] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0201] In the technical solution of this application, the collection, storage, use, processing, transmission, provision, and disclosure of user personal information involved, such as the user's images and attribute data, etc., and the collection, storage, use, processing, transmission, provision, and disclosure of meteorological information, weather detection-related data, atmospheric detection-related data, etc., all comply with the provisions of relevant laws and regulations and do not violate public order and good customs.

[0202] According to the embodiments of this application, this application also provides an electronic device, a readable storage medium, and a computer program product for executing the calibration method of the gas detection lidar in the foregoing embodiments.

[0203] It should be understood that various forms of the processes shown above can be used, steps can be reordered, added, or deleted. For example, the steps recorded in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired results of the technical solution disclosed in this application can be achieved. This is not limited herein.

[0204] The above specific implementation manners do not constitute a limitation to the protection scope of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims

1. A gas detection laser radar calibration method, characterized in that: The method comprises: Obtain the first echo signal strength and the second echo signal strength of the laser radar to be processed; wherein the first echo signal strength is obtained by detection using the auxiliary calibration device and the laser radar, and the light-receiving and light-emitting paths of the auxiliary calibration device meet the preset receiving and transmitting field of view conditions; the interval between the detection time of the first echo signal strength and the detection time of the second echo signal strength is less than the preset time threshold, and the distance between the detection position of the first echo signal strength and the detection position of the second echo signal strength is less than the preset distance threshold; the receiving field of view of the auxiliary calibration device covers the transmitting field of view; the second echo signal strength is directly detected by the laser radar; The first echo signal strength includes the first echo signal strength at the first position and the first echo signal strength at the second position, and the second echo signal strength includes the second echo signal strength at the first position and the second echo signal strength at the second position; the ratio of the first echo signal strength at the first position and the first echo signal strength at the second position is calculated to obtain a first ratio; the ratio of the second echo signal strength at the first position and the second echo signal strength at the second position is calculated to obtain a second ratio; the ratio of the first ratio and the second ratio is used as a target calibration parameter; the target calibration parameter is the amount by which the efficiency of the laser radar system changes with distance; The target calibration parameters include target calibration parameters of at least two wavelengths. Based on the target calibration parameters of the first wavelength and the target calibration parameters of the second wavelength, a preset influence value algorithm is used to calculate the influence value of the laser radar system efficiency. The influence value algorithm is expressed as: in, is the target calibration parameter for the first wavelength, a target calibration parameter for the second wavelength; Based on the laser radar system efficiency impact value, the laser radar is calibrated to obtain a calibrated laser radar.

2. The method according to claim 1, characterized in that The obtaining of the first echo signal strength of the laser radar to be processed includes: The laser radar to be processed emits a first laser to the auxiliary calibration device; The auxiliary calibration device performs a first detection process on the atmosphere based on the first laser to obtain the first echo signal strength; The first echo signal strength of the laser radar to be processed is obtained from the auxiliary calibration device.

3. The method according to claim 2, characterized in that The auxiliary calibration device includes a beam integration module, an echo receiving module, and a signal processing module. The auxiliary calibration device performs a first detection process on the atmosphere based on the first laser to obtain the first echo signal strength, including: The beam integration module receives the first laser emitted by the laser radar to be processed; The beam integration module adjusts the received first laser to obtain an adjusted first echo light, and sends the first echo light to the echo receiving module; The echo receiving module converts the received first echo light to obtain a first electrical signal, and sends the first electrical signal to the signal processing module; The signal processing module performs calculation processing on the first electrical signal to obtain the first echo signal strength.

4. The method according to claim 1, characterized in that: Get the second echo signal strength of the laser radar to be processed, including: The laser radar to be processed emits a second laser vertically upward; The laser radar to be processed performs a second detection process on the atmosphere based on the second laser to obtain the second echo signal intensity; The second echo signal strength is obtained from the laser radar to be processed.

5. The method according to claim 4, characterized in that The laser radar to be processed includes a light-receiving and light-emitting circuit module, an optoelectronic processing module and a data processing module. The laser radar to be processed performs a second detection process on the atmosphere based on the second laser to obtain the second echo signal strength, including: The light receiving and transmitting circuit module receives a second echo light returned based on the second laser; The light receiving and transmitting circuit module sends the second echo light to the photoelectric processing module; The photoelectric processing module converts the second echo light to obtain a second electrical signal, and sends the second electrical signal to the data processing module; The optoelectronic processing module performs calculation processing on the second electrical signal to obtain the second echo signal strength.

6. The method according to claim 1, characterized in that The preset receiving and transmitting field of view conditions include that the receiving diameter of the receiving field of view is greater than the transmitting spot diameter of the transmitting field of view, and the receiving field of view angle is greater than the sum of the transmitting field of view angle and a preset coefficient, and the preset coefficient is determined based on the angle between the optical axis of the receiving field of view and the optical axis of the transmitting field of view.

7. A gas detection laser radar calibration system, characterized in that: The calibration system comprises: an auxiliary calibration device, a laser radar to be processed, and a data processing device; the data processing device is respectively connected to the auxiliary calibration device and the laser radar to be processed in communication; The auxiliary calibration device is used to detect and obtain the first echo signal strength based on the received laser sent by the laser radar to be processed; The laser radar to be processed is used to detect and obtain the second echo signal strength; The data processing device is used to execute the calibration method of the gas detection laser radar as described in any one of claims 1-6.

8. The system according to claim 7, characterized in that The auxiliary calibration equipment includes a beam integration module, an echo receiving module, and a signal processing module; The beam integration module is used to control the center of the emission spot of the emission field of view to coincide with the center of the receiving field of view; The echo receiving module is used to control the receiving field of view angle and the transmitting field of view angle to meet the preset field of view angle condition, and the receiving field of view diameter and the transmitting field of view diameter to meet the preset length condition; The signal processing module is used to calculate and store the first echo signal strength.

Images