An open optical path-based atmospheric no3 radical measurement system and method

Abstract

The present application relates to the field of optical measurement technology, disclose a kind of based on open optical path atmospheric NO3 radical measurement system and method, system includes light source module, first convex lens, first high reflectivity lens, second high reflectivity lens, detachable cavity, second convex lens and spectrometer, the present application is directly sampled to the air between high reflect lens by the design of open optical path, avoid the wall loss of NO3 radical in active sampling, to improve the sensitivity and accuracy of measurement. While introducing the design of detachable cavity, realize the flexible switching of zero air and actual atmospheric sampling. The introduction of zero-point spectral library method effectively compensates the influence of temperature and humidity change on light source and spectrometer, the spectral shift caused by environmental change is eliminated by dynamic calibration, in addition, the input of real-time water vapor absorption cross section can accurately remove the influence of water vapor absorption on NO3 radical measurement, further improve the reliability of measurement result.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and more specifically, to an atmospheric NO3 free radical measurement system and method based on an open optical path. Background Technology

[0002] Monitoring NO3 free radicals in the atmosphere is particularly important. NO3 free radicals are gases that are more active at night and play a crucial role in atmospheric chemical reactions, participating in the formation of various atmospheric reactions, especially significantly influencing the formation of secondary air pollution and secondary organic aerosols. Therefore, accurately measuring the concentration of NO3 free radicals in the atmosphere can provide vital data for air quality monitoring, pollutant emission control, and environmental science research.

[0003] Currently, some air pollution monitoring systems on the market use spectral analysis to detect NO3 free radicals in the atmosphere. However, most existing measurement systems suffer from problems such as blocked optical paths, which can easily lead to NO3 free radical wall loss. Furthermore, the measurement accuracy is greatly affected by the external environment, especially under conditions of high humidity and large temperature variations, resulting in high instability and low accuracy of the measurement results. Summary of the Invention

[0004] To overcome the shortcomings of low accuracy and instability in existing NO3 radical measurement techniques, this invention proposes the following technical solution:

[0005] In a first aspect, the present invention proposes an atmospheric NO3 radical measurement system based on an open optical path, comprising:

[0006] A light source module used to emit light beams of a specific wavelength;

[0007] The first convex lens is used to focus the light beam emitted by the light source module;

[0008] The first high-reflectivity lens is positioned after the first convex lens;

[0009] The second high-reflectivity lens is positioned opposite to the first high-reflectivity lens to form an optical resonant cavity, allowing the light beam to undergo multiple reflections between the first and second high-reflectivity lenses.

[0010] A detachable cavity is disposed between the first high-reflectivity lens and the second high-reflectivity lens to form a closed sampling cavity when acquiring zero-point spectra and calibrating reflectivity. After the detachable cavity is removed, an open optical path is formed between the first high-reflectivity lens and the second high-reflectivity lens.

[0011] The second convex lens, positioned after the second high-reflectivity lens, is used to focus the light beam after multiple reflections in the open optical path.

[0012] A spectrometer is used to receive the spectral information of a beam focused by a second convex lens in order to obtain the concentration of NO3 free radicals in the atmosphere.

[0013] As a preferred technical solution, the system also includes a first optical fiber and a second optical fiber.

[0014] The light beam emitted by the light source module is transmitted to the first convex lens through the first optical fiber;

[0015] The beam focused by the second convex lens is transmitted to the spectrometer through the second optical fiber.

[0016] As a preferred technical solution, a first air inlet is provided on the light-emitting surface side of the first high-reflectivity lens, and a second air inlet is provided on the light-incident surface side of the second high-reflectivity lens.

[0017] As a preferred technical solution, the light source module is an LED light source, and the wavelength range of the light beam emitted by the LED light source covers 640-680nm, with a center wavelength of 660nm.

[0018] As a preferred technical solution, the system also includes a temperature and humidity sensor, which is used to measure the temperature and humidity of the environment in real time.

[0019] As a preferred technical solution, the system also includes a zero-point spectral library module, which is used to collect zero-point spectra under different temperature and humidity conditions and store them in the zero-point spectral library.

[0020] Secondly, the present invention also proposes an atmospheric NO3 radical measurement method based on an open optical path, applicable to an atmospheric NO3 radical measurement system based on an open optical path as described in any of the schemes of the first aspect, comprising:

[0021] A detachable cavity is installed between the first high-reflectivity lens and the second high-reflectivity lens to form a closed sampling cavity;

[0022] Nitrogen gas is introduced into the sealed sampling chamber through the first and second air inlets.

[0023] A light beam is emitted by the light source module. After being focused by the first convex lens, the beam is reflected by the closed sampling cavity between the first and second high-reflectivity lenses. Finally, it is focused by the second convex lens and transmitted to the spectrometer.

[0024] The spectrometer receives the light beam and records the spectral information as the zero-point spectrum, which is then stored in the zero-point spectrum library.

[0025] Remove the detachable cavity to form an open optical path between the first high-reflectivity lens and the second high-reflectivity lens;

[0026] The light beam is emitted again by the light source module. After being focused by the first convex lens, the beam is reflected by the open sampling cavity between the first and second high-reflectivity lenses. Finally, it is focused by the second convex lens and transmitted to the spectrometer.

[0027] The spectrometer receives the light beam and records the spectral information as a sampled spectrum.

[0028] The concentration of NO3 free radicals in the atmosphere is determined by comparing the sampled spectrum with the zero-point spectrum in the zero-point spectrum library.

[0029] As a preferred technical solution, the sampled spectrum is compared with the zero-point spectrum in the zero-point spectral library to determine the concentration of NO3 free radicals in the atmosphere, including:

[0030] Select the zero-point spectrum from the zero-point spectrum library as the reference spectrum. ;

[0031] Calculate the absorption coefficient of the substance based on the reference spectrum. Its expression is as follows:

[0032]

[0033] in, For sampling spectrum, For high reflectivity lenses at wavelength reflectivity, The effective cavity length between the first high-reflectivity lens and the second high-reflectivity lens;

[0034] Based on the absorption coefficient of multiple substances The concentration of NO3 free radicals was calculated using the least squares fitting method.

[0035] As a preferred technical solution, the zero-point library method is used to select a zero-point spectrum as the reference spectrum from the zero-point spectrum library. ,include:

[0036] For each sampled spectrum I i ( i =1,2,..., m ) and all zero-point spectra in the zero-point spectrum library I 0j ( j =1,2,..., n Calculate the absorption coefficients in the 645-650nm and 668-673nm wavelength bands, respectively. α 1 ij and α 2 ij ;

[0037] For each pair of sampled spectra I i and zero-point spectrum I 0j ,calculate α 1 ij and α2 ij average α 1_mean and α 2_mean and standard deviation α 1_std and α 2_std;

[0038] The deviation X between the sampled spectrum and the zero-point spectrum is calculated using the following formula.

[0039] X=| α 1_mean- α 2_mean+ α 1_std+ α 2_std|

[0040] Repeat the above steps for all zero-point spectra in the zero-point spectrum library to obtain a set of X values;

[0041] Find the minimum value in the set of X values, and use the zero-point spectrum corresponding to the minimum value as the reference spectrum.

[0042] As a preferred technical solution, based on the absorption coefficients of multiple substances... The concentration of NO3 free radicals was calculated using the least squares fitting method, including:

[0043] It measures the current ambient temperature and humidity in real time, and calculates the water vapor concentration at wavelength based on the current ambient temperature and humidity. Absorption cross section at the location;

[0044] Based on the absorption coefficient of multiple substances The absorption contributions of NO3 radicals, NO2, and water vapor are calculated, and the expressions are as follows:

[0045]

[0046] in, , and These represent the concentrations of NO3 free radicals, NO2, and water vapor, respectively. and These represent the wavelengths of NO3 radical and NO2, respectively. The absorption cross section at that point This indicates the current water vapor at wavelength Absorption cross section at the location;

[0047] The concentration of NO3 radicals was extracted using the least squares fitting method based on the absorption contributions of NO3 radicals, NO2, and water vapor.

[0048] The beneficial effects of the present invention include at least the following:

[0049] First, by designing an open optical path, the system can directly sample the air between the high-reflectivity mirrors, avoiding wall loss of NO3 radicals in traditional active sampling, thus improving the sensitivity and accuracy of the measurement. Simultaneously, the introduction of a detachable cavity design not only enables flexible switching between zero-air and actual atmospheric sampling, but also ensures unobstructed beam reflection during multiple reflections, guaranteeing the stability and accuracy of the spectral signal. Second, the introduction of the zero-point spectral library method effectively compensates for the effects of temperature and humidity changes on the light source and spectrometer, and eliminates spectral shifts caused by environmental changes through dynamic calibration, further improving the reliability of the measurement results. Finally, the input of real-time water vapor absorption cross-sections can remove the influence of water vapor absorption on NO3 radical measurement, improving measurement accuracy. Overall, this invention provides a high-precision, flexible, and stable atmospheric NO3 radical measurement scheme with broader application potential, particularly suitable for atmospheric environmental monitoring and pollutant emission assessment. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the structure of an atmospheric NO3 free radical measurement system based on an open optical path provided in an embodiment of the present invention.

[0051] Figure 2 This is a schematic flowchart of the atmospheric NO3 free radical measurement method based on an open optical path provided in an embodiment of the present invention.

[0052] Figure 3 This is a schematic diagram of the process for matching the optimal zero-point spectrum provided in an embodiment of the present invention.

[0053] Figure 4 This is a flowchart illustrating the real-time water vapor absorption cross-section calculation method provided in an embodiment of the present invention.

[0054] The light source module 1, the first convex lens 2, the first high reflectivity lens 3, the second high reflectivity lens 4, the detachable cavity 5, the second convex lens 6, the spectrometer 7, the first optical fiber 8, the second optical fiber 9, the first air inlet 10, and the second air inlet 11. Detailed Implementation

[0055] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred technical solutions. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred technical solutions are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0056] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0057] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0058] Example 1

[0059] This embodiment proposes an atmospheric NO3 radical measurement system based on an open optical path, such as... Figure 1 As shown, Figure 1 The schematic diagram of an atmospheric NO3 free radical measurement system based on an open optical path provided in this embodiment includes: a light source module 1, a first convex lens 2, a first high reflectivity lens 3, a second high reflectivity lens 4, a detachable cavity 5, a second convex lens 6, and a spectrometer 7.

[0060] The light source module 1 emits a beam of a specific wavelength. A first convex lens 2 focuses the beam emitted by the light source module 1. A first high-reflectivity lens 3 is positioned after the first convex lens 2, and a second high-reflectivity lens 4 is positioned opposite the first high-reflectivity lens 3, together forming an optical resonant cavity, allowing the beam to undergo multiple reflections between the first high-reflectivity lens 3 and the second high-reflectivity lens 4. A detachable cavity 5 is positioned between the first high-reflectivity lens 3 and the second high-reflectivity lens 4, forming a closed sampling cavity for acquiring zero-point spectra and calibrating reflectivity. After the detachable cavity 5 is removed, an open optical path is formed between the first high-reflectivity lens 3 and the second high-reflectivity lens 4. A second convex lens 6 is positioned after the second high-reflectivity lens 4, focusing the beam after multiple reflections in the open optical path. A spectrometer 7 receives the spectral information of the beam focused by the second convex lens 6 to obtain the concentration of NO3 free radicals in the atmosphere.

[0061] In this embodiment, the system also includes a first optical fiber 8 and a second optical fiber 9.

[0062] The light beam emitted by the light source module is transmitted to the first convex lens 2 through the first optical fiber 8;

[0063] The beam focused by the second convex lens 6 is transmitted to the spectrometer 7 through the second optical fiber 9.

[0064] In this embodiment, a first air inlet 10 is provided on the light-emitting surface side of the first high-reflectivity lens 3, and a second air inlet 11 is provided on the light-incident surface side of the second high-reflectivity lens 4.

[0065] In this embodiment, the light source module 1 is an LED light source, which is coaxially arranged with the LED light source, the first high reflectivity lens 3, and the first high reflectivity lens 4. The wavelength range of the light beam emitted by the LED light source covers 640-680nm, with a center wavelength of 660nm.

[0066] In this embodiment, the system also includes a temperature and humidity sensor, which is used to measure the temperature and humidity of the environment in real time.

[0067] In this embodiment, the system also includes a zero-point spectral library module, which is used to collect zero-point spectra under different temperature and humidity conditions and store them in the zero-point spectral library.

[0068] Understandably, by designing an open optical path, the system can directly sample the air between the high-reflectivity mirrors, avoiding wall loss of NO3 radicals in traditional active sampling, thereby improving the sensitivity and accuracy of the measurement. Simultaneously, the introduction of the detachable cavity 5 not only enables flexible switching between zero-air and actual atmospheric sampling, but also ensures that the LED light source, the first high-reflectivity mirror 3, and the first high-reflectivity mirror 4 are coaxially aligned, guaranteeing unobstructed beam reflection during multiple reflections and ensuring the stability and accuracy of the spectral signal. Secondly, the introduction of the zero-point spectral library method effectively compensates for the effects of temperature and humidity changes on the light source and spectrometer 7. Dynamic calibration eliminates spectral shifts caused by environmental changes, further improving the reliability of the measurement results. Real-time input of the water vapor absorption cross section accurately eliminates the influence of water vapor absorption on NO3 radical measurement, improving the accuracy of the measurement results. Overall, this invention provides a high-precision, flexible, and stable atmospheric NO3 radical measurement scheme with broader application potential, particularly suitable for atmospheric environmental monitoring and pollutant emission assessment.

[0069] Example 2

[0070] like Figure 2 As shown, this embodiment proposes an atmospheric NO3 radical measurement method based on an open optical path, applied to the atmospheric NO3 radical measurement system based on an open optical path as described in the above embodiment, including:

[0071] S1: The detachable cavity 5 is installed between the first high-reflectivity lens 3 and the second high-reflectivity lens 4 to form a closed sampling cavity. At this time, the optical path within the cavity is closed, allowing for zero-point spectrum acquisition and reflectivity calibration. The cavity installation ensures that the beam propagation within the optical system is not interfered with by external gas, making it suitable for stable measurement of background signals.

[0072] S2: Nitrogen gas is introduced into the sealed sampling chamber through the first air inlet 10 and the second air inlet 11. The purpose of nitrogen gas is to purge air from the chamber, preventing interference from water vapor and other gases. Nitrogen gas also acts as a purge gas to protect the high-reflectivity lens from particulate contamination. Introducing nitrogen gas ensures that no other gaseous components that might affect spectral analysis are present in the system when acquiring zero-point spectra.

[0073] S3: Activate light source module 1 to emit a light beam. After being focused by the first convex lens 2, the beam passes through the installed closed sampling cavity and is reflected between the first high-reflectivity lens 3 and the second high-reflectivity lens 4. After multiple reflections, the beam is finally focused again by the second convex lens 6 and transmitted to the spectrometer 7.

[0074] S4: The spectrometer receives the light beam and records the spectral information as the zero-point spectrum, which is then stored in the zero-point spectrum library. Since the cavity is in a nitrogen environment, the measured spectral data is the zero-point spectrum. This zero-point spectrum is stored in the zero-point spectrum library module as a comparison benchmark for subsequent actual sampling.

[0075] S5: Before the actual measurement, the detachable cavity 5 is first removed from the system. After the cavity is removed, an open optical path is formed between the first high-reflectivity lens 3 and the second high-reflectivity lens 4. At this time, the optical path is no longer closed, and the system is in direct contact with the atmospheric environment.

[0076] S6: The light beam is emitted again for actual sampling, activating the light source module 1. The light beam is then focused by the first convex lens 2, passes through the open optical path between the first high-reflectivity lens 3 and the second high-reflectivity lens 4, and interacts with molecules such as NO3 free radicals in the external atmosphere during this process, generating a spectral absorption signal.

[0077] S7: After reflection, the light beam is focused by the second convex lens 6 and transmitted to the spectrometer 7. At this time, the light beam received by the spectrometer 7 carries the characteristic spectral information of NO3 free radicals in the atmosphere.

[0078] S8: Spectrometer 7 receives the light beam and records the spectral information as a sampled spectrum.

[0079] S9: Compare the sampled spectrum with the zero-point spectrum in the zero-point spectrum library to determine the concentration of NO3 free radicals in the atmosphere.

[0080] In this embodiment, the concentration of NO3 free radicals in the atmosphere is determined by comparing the sampled spectrum with the zero-point spectrum in the zero-point spectral library, including:

[0081] Select the zero-point spectrum from the zero-point spectrum library as the reference spectrum. .

[0082] Calculate the absorption coefficient of the substance based on the reference spectrum. Its expression is as follows:

[0083]

[0084] in, For sampling spectrum, For high reflectivity lenses at wavelength reflectivity, The effective cavity length between the first high-reflectivity lens 3 and the second high-reflectivity lens 4.

[0085] Based on the absorption coefficient of multiple substances The concentration of NO3 free radicals was calculated using the least squares fitting method.

[0086] It should be noted that the periodic variations in atmospheric temperature and relative humidity between day and night significantly affect the light source and spectrometer 7 of the measurement system. This effect can cause varying degrees of shift in the sampled spectra, leading to deviations in the NO3 radical concentration obtained from the spectral analysis. Furthermore, because this system employs passive sampling via an open optical path, traditional chemical titration methods cannot obtain the dynamic zero point. This invention innovatively proposes a zero-point spectral library method, aiming to effectively eliminate the influence of temperature and relative humidity variations on the sampled spectra.

[0087] The zero-point spectral library of this invention covers a large number of zero-point spectra reflecting diurnal variations in temperature and relative humidity. In practical applications, when calculating absorption coefficients... α At that time, the system will intelligently filter the spectrum that is currently being sampled. I The zero-point spectrum where temperature and relative humidity are closest is used as I 0. This method can effectively eliminate the sampling spectral shift caused by changes in environmental factors, thereby improving the calculated absorption coefficient. α More accurate and closer to reality.

[0088] LED light sources inherently exhibit temperature drift. As the light source temperature changes, the luminous intensity and emission wavelength of the LED will also change accordingly. Furthermore, the CCD in the spectrometer 7 is also affected by temperature during operation, resulting in varying degrees of noise in the acquired spectrum. If a fixed zero-point spectrum is still used under these circumstances... I 0, when the light source experiences temperature drift, the sampled spectrum I The band will be with I A mismatch occurs. This mismatch causes a baseline shift in the absorption coefficient α, ultimately leading to significant uncertainty in the NO3 radical concentration obtained from the spectral analysis.

[0089] This invention selects and samples spectra I The zero-point spectrum, with its highly consistent temperature and relative humidity, ensures that the environmental influences on the light source and spectrometer 7 are essentially the same. This strategy is crucial for calculating the absorption coefficient. α This method can largely eliminate the drift effects of temperature and relative humidity changes on the light source and spectrometer 7, thereby significantly improving the accuracy and reliability of measurements. There are several options for selecting the zero-point spectrum. Nitrogen gas spectrum can be used as the zero-point spectral library. Alternatively, the midday sampling spectrum (without NO3 radical absorption) can be selected as the zero-point spectrum. Using the midday sampling spectrum as the zero-point spectrum can simultaneously eliminate some of the effects of water vapor absorption and particulate matter absorption.

[0090] like Figure 3As shown, this invention uses a high-power monochromatic LED red light source with a center wavelength of 660nm and an effective wavelength range covering 640-680nm. This wavelength range precisely includes the main absorption peak of NO3 free radicals near 662nm.

[0091] Based on the spectral characteristics of NO3 radicals, in actual observations, the absorption coefficients of non-NO3 radical absorption bands such as 640-650 nm and 668-680 nm are... α The values ​​should remain relatively stable and close. However, temperature drift of the light source will cause corresponding changes in the absorption coefficients of these two bands.

[0092] Based on this principle, the present invention designs such as Figure 4 The precise screening steps shown:

[0093] For each sampled spectrum I i ( i =1,2,..., m ) and all zero-point spectra in the zero-point spectrum library I 0j ( j =1,2,..., n Calculate the absorption coefficients in the 645-650nm and 668-673nm wavelength bands, respectively. α 1 ij and α 2 ij ;

[0094] For each pair of sampled spectra I i and zero-point spectrum I 0j ,calculate α 1 ij and α2 ij average α 1_mean and α 2_mean and standard deviation α 1_std and α 2_std;

[0095] The deviation X between the sampled spectrum and the zero-point spectrum is calculated using the following formula:

[0096] X=| α 1_mean- α 2_mean+ α 1_std+ α 2_std|

[0097] Repeat the above steps for all zero-point spectra in the zero-point spectrum library to obtain a set of X values;

[0098] Find the minimum value in the set of X values, and use the zero-point spectrum corresponding to the minimum value as the reference spectrum.

[0099] This process is performed on each sampled spectrum. I The best matching zero-point spectrum was found for all of them. I 0. This method effectively compensates for spectral shifts caused by temperature drift and other environmental factors, thus significantly improving the accuracy of NO3 radical concentration measurements. Notably, this screening method considers not only the overall shape of the spectrum but also assesses spectral stability by calculating the standard deviation, making the selection process more comprehensive and reliable. By performing this screening step on each sampled spectrum, a highly matched zero-point spectrum is ultimately obtained. I The 0 set lays a solid foundation for subsequent calculations of NO3 radical concentration.

[0100] In this embodiment, based on the absorption coefficients of multiple substances... The concentration of NO3 free radicals was calculated using the least squares fitting method, including:

[0101] It measures the current ambient temperature and humidity in real time, and calculates the water vapor concentration at wavelength based on the current ambient temperature and humidity. Absorption cross section at the location;

[0102] Based on the absorption coefficient of multiple substances The absorption contributions of NO3 radicals, NO2, and water vapor are calculated, and the expressions are as follows:

[0103]

[0104] in, , and These represent the concentrations of NO3 free radicals, NO2, and water vapor, respectively. , and These represent NO3 radicals, NO2, and water vapor at wavelengths of [wavelength values ​​missing]. The absorption cross section at that location.

[0105] The concentration of NO3 radicals was extracted using the least squares fitting method based on the absorption contributions of NO3 radicals, NO2, and water vapor.

[0106] In this embodiment, as Figure 4As shown, when calculating the real-time water vapor absorption cross section, high-resolution spectral data of water must first be downloaded from the HITRAN database. Each spectral line broadens due to the thermal motion of molecules. Under low pressure conditions, this phenomenon mainly manifests as the Doppler effect, causing the spectral line broadening to follow a Gaussian distribution, i.e., Gaussian broadening. This broadening is primarily affected by temperature. Under high pressure conditions, frequent collisions of molecules or atoms lead to an increase in the frequency width of the radiation. This broadening increases linearly with particle density and external particle pressure, known as pressure broadening. At this point, the spectral line broadening distribution follows a Lorentz distribution, also called Lorentz broadening, which is mainly affected by pressure and the collision cross section of molecules.

[0107] Under actual atmospheric conditions, spectral lines exhibit characteristics of both Gaussian and Lorentz distributions; this intermediate distribution is called the Viogt distribution. While both Gaussian and Lorentz functions are analytic functions that can be directly solved, the Viogt function is a convolution function and has no analytical solution, requiring an approximate solution obtained through algorithms. To eliminate the broadening effect, the Viogt integral approximation method is used to calculate the H2O absorption cross-section under specified temperature and pressure conditions. This method allows for the calculation of the H2O absorption cross-section under specific conditions, which is then convolved using high-resolution spectral lines and instrument functions to obtain the H2O absorption cross-section under the corresponding specified conditions. This method not only improves computational efficiency but also ensures real-time input of the water vapor absorption cross-section during spectral interpretation, resulting in a more accurate calculation of NO3 radical concentration.

[0108] It should be noted that the foregoing explanation of the embodiment of the atmospheric NO3 free radical measurement method based on open optical path also applies to the atmospheric NO3 free radical measurement system based on open optical path in this embodiment, and will not be repeated here.

[0109] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0110] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0111] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more N executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0112] It should be understood that the various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (FPGAs), field-programmable gate arrays (FPGAs), etc.

[0113] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by a program instructing related hardware, and the program can be stored in a computer-readable storage medium. When executed, the program includes one or a combination of the steps of the method embodiments.

[0114] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An open optical path based atmospheric NO3 radical measurement method applied to an open optical path based atmospheric NO3 radical measurement system, the system comprising: A light source module (1) is used to emit a beam of light of a specific wavelength; The first convex lens (2) is used to focus the light beam emitted by the light source module (1); the first high reflectivity lens (3) is disposed behind the first convex lens (2); the second high reflectivity lens (4) is disposed opposite to the first high reflectivity lens (3) and together they form an optical resonant cavity, so that the light beam undergoes multiple reflections between the first high reflectivity lens (3) and the second high reflectivity lens (4); the detachable cavity (5) is disposed between the first high reflectivity lens (3) and the second high reflectivity lens (4) to form a closed sampling cavity when collecting zero-point spectra and calibrating reflectivity. The body, after the detachable cavity (5) is removed, forms an open optical path between the first high reflectivity lens (3) and the second high reflectivity lens (4); the second convex lens (6), disposed after the second high reflectivity lens (4), is used to focus the light beam after multiple reflections in the open optical path; the spectrometer (7) is used to receive the spectral information of the light beam focused by the second convex lens (6) to obtain the concentration of NO3 free radicals in the atmosphere; the zero-point spectral library module is used to collect zero-point spectra under different temperature and humidity conditions and store them in the zero-point spectral library, characterized in that it includes: The detachable cavity (5) is installed between the first high reflectivity lens (3) and the second high reflectivity lens (4) to form a closed sampling cavity; Nitrogen gas is introduced into the closed sampling cavity through the first air inlet (10) and the second air inlet (11); The light beam is emitted by the light source module (1), and after being focused by the first convex lens (2), it is reflected by the closed sampling cavity between the first high reflectivity lens (3) and the second high reflectivity lens (4), and finally focused by the second convex lens (6) and transmitted to the spectrometer (7). The spectrometer (7) receives the beam and records the spectral information as the zero-point spectrum, and stores the zero-point spectrum in the zero-point spectrum library; Remove the detachable cavity (5) to form an open optical path between the first high reflectivity lens (3) and the second high reflectivity lens (4); The light beam is emitted again by the light source module (1). After being focused by the first convex lens (2), the beam is reflected by the open sampling cavity between the first high reflectivity lens (3) and the second high reflectivity lens (4). Finally, it is focused by the second convex lens (6) and transmitted to the spectrometer (7). The spectrometer (7) receives the light beam and records the spectral information as a sampled spectrum; it compares the sampled spectrum with the zero-point spectrum in the zero-point spectral library to determine the concentration of NO3 free radicals in the atmosphere, including: selecting a zero point spectrum from a zero point spectral library as a reference spectrum comprising: For each sampled spectrum I i and all zero-point spectra in the zero-point spectrum library I 0j Calculate the absorption coefficients in the 645-650nm and 668-673nm wavelength bands, respectively. α 1 ij and α 2 ij For each pair of sampled spectra I i and zero-point spectrum I 0j ,calculate α 1 ij and α2 ij average α 1_mean and α 2_mean and standard deviation α 1_std and α 2_std; where, i =1,2,..., m , j =1,2,..., n ; The deviation X between the sampled spectrum and the zero-point spectrum is calculated using the following formula: X=| α 1_mean- α 2_mean+ α 1_std+ α 2_std| Repeat the above steps for all zero-point spectra in the zero-point spectrum library to obtain a set of X values; Find the minimum value in the set of X values, and use the zero-point spectrum corresponding to the minimum value as the reference spectrum; Calculate the absorption coefficients of multiple substances based on the reference spectrum. Its expression is as follows: in, For sampling spectrum, For high reflectivity lenses at wavelength reflectivity, The effective cavity length between the first high-reflectivity lens (3) and the second high-reflectivity lens (4); Based on the absorption coefficient of multiple substances The concentration of NO3 free radicals was calculated using the least squares fitting method.

2. The atmospheric NO3 free radical measurement method based on an open optical path according to claim 1, characterized in that, The system also includes a first optical fiber (8) and a second optical fiber (9); The light beam emitted by the light source module is transmitted to the first convex lens (2) through the first optical fiber (8); The beam focused by the second convex lens (6) is transmitted to the spectrometer (7) through the second optical fiber (9).

3. The method for measuring atmospheric NO3 free radicals based on an open optical path according to claim 1, characterized in that, The first high reflectivity lens (3) has a first air inlet (10) on the light-emitting side and the second high reflectivity lens (4) has a second air inlet (11) on the light-incident side.

4. The method for measuring atmospheric NO3 free radicals based on an open optical path according to claim 1, characterized in that, The light source module (1) is an LED light source. The wavelength range of the light beam emitted by the LED light source covers 640-680 nm, and the center wavelength is 660 nm.

5. The atmospheric NO3 free radical measurement method based on an open optical path according to claim 1, characterized in that, The system also includes a temperature and humidity sensor, which is used to measure the temperature and humidity of the environment in real time.

6. The method for measuring atmospheric NO3 free radicals based on an open optical path according to claim 1, characterized in that, Based on the absorption coefficient of multiple substances The concentration of NO3 free radicals was calculated using the least squares fitting method, including: It measures the current ambient temperature and humidity in real time, and calculates the water vapor concentration at wavelength based on the current ambient temperature and humidity. Absorption cross section at the location; Based on the absorption coefficient of multiple substances The absorption contributions of NO3 radicals, NO2, and water vapor are calculated, and the expressions are as follows: in, , and These represent the concentrations of NO3 free radicals, NO2, and water vapor, respectively. and These represent the wavelengths of NO3 radical and NO2, respectively. The absorption cross section at that point This indicates the current water vapor at wavelength Absorption cross section at the location; The concentration of NO3 radicals was extracted using the least squares fitting method based on the absorption contributions of NO3 radicals, NO2, and water vapor.

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