A highly sensitive, miniaturized, and precise measurement device and method for HOx radicals

Abstract

The application discloses a high-sensitivity miniaturized HOx radical precision measuring device and method, relates to the technical field of atmospheric environment detection and automatic control, and is composed of a radical generation and removal device, a light source module, a longitudinal HOx double cavity, a gas distribution module and a collection and control system. The radical generation and removal device can generate HOx radicals or remove OH radicals; the light source module can emit laser for OH radical fluorescence generation and transmit the laser into the longitudinal HOx double cavity; the longitudinal HOx double cavity is used for exciting OH radicals to generate a large amount of fluorescence and collecting and converting the fluorescence into an electric signal; the gas distribution module is used for injecting gas in the device and maintaining the gas flow state; and the control and collection system is used for controlling the automatic operation of the device, data collection and processing. The application has the advantages of high detection sensitivity, small volume, fast acquisition, removal of OH radical measurement interference, fast calibration of similar concentrations according to the actual HOx concentration in the actual measurement environment, accurate spectrum of laser wavelength and high-sensitivity and precise measurement of HOx radicals.

Description

Technical Field

[0001] This invention relates to the field of atmospheric environment detection and automated control technology, and in particular to a highly sensitive, miniaturized, and precise measurement device and method for HOx free radicals. Background Technology

[0002] Atmospheric oxidation capacity is one of the key factors influencing regional pollution, global climate change, and the atmospheric ecological environment. Atmospheric oxidation of gaseous pollutants is a driving force behind secondary pollution. Free radicals contribute over 80% to atmospheric oxidation capacity. During the daytime, tropospheric oxidation capacity is mainly provided by photochemical chain reactions composed of HOx free radicals (a collective term for OH and HO2 free radicals), ultimately leading to complex atmospheric pollution characterized by haze and ozone. Therefore, accurately measuring the concentration of HOx free radicals in the atmosphere is particularly important. Due to its advantages of low background stray light, long fluorescence lifetime, high system detection sensitivity, and low spectral interference, laser-induced fluorescence technology has gradually become the main technique for measuring HOx free radicals in the field. A laser-induced fluorescence instrument consists of four core components: a laser emission unit, a low-pressure fluorescence detection cavity, a high-sensitivity photomultiplier tube, and a standard concentration calibration module. This instrument employs low-pressure expansion sampling technology. It collects atmospheric data through a micro-orifice at the top of the low-pressure fluorescence detection chamber. As the gas sample passes through the micro-orifice, it expands rapidly and is ejected downwards into the chamber. A laser beam irradiates the expanded gas sample, exciting OH radicals and generating characteristic fluorescence. The detection system captures the fluorescence signal using a photomultiplier tube. It distinguishes the instrument's background signal by using a method where the laser wavelength deviates from the fluorescence excitation band, and utilizes a quantitative relationship established by a standard concentration calibration module to ultimately determine the concentration of OH radicals. HO2 radicals are indirectly measured by converting them to OH radicals via NO conversion. However, there are two main limitations. First, because the concentration of HOx radicals in the atmosphere is very low, conventional single-emission fluorescence excitation methods are insufficient to accurately capture changes in HOx radical concentration when concentrations are low (e.g., in winter or at night). Second, due to environmental factors, the detection sensitivity of the laser-induced fluorescence spectrometer for HOx radicals varies slightly over time, leading to systematic measurement bias. Third, since the concentration of OH radicals in the actual atmosphere is much lower than that of HO2 radicals, conventional HOx radical standard sources can only generate known equal amounts of OH radicals and HO2 radicals, and can only adjust the concentration of HOx radicals within a small range. They cannot be calibrated to approximate the actual concentration of HOx radicals in the atmosphere. Due to changes in the actual atmospheric environment, the system's response to large-scale variations in HOx radical concentration may exhibit unknown nonlinearities, leading to additional system bias. Fourth, interference in the measurement of OH radicals using laser-induced fluorescence technology has been proven to be widespread, especially in forested areas. Since most of these interferences cannot be quantitatively subtracted, laser-induced fluorescence technology exhibits varying degrees of bias when measuring OH radicals.Fifth, laser-induced fluorescence analyzers typically include a laser wavelength calibration device to lock the peak values ​​of the fluorescence spectrum. The peak response of the photomultiplier tube within the laser wavelength calibration device deviates slightly from the peak response of the photomultiplier tube within the low-pressure fluorescence detection cavity. This leads to a slight decrease in the instrument's detection sensitivity, and the asynchronous changes in sensitivity between the two devices can introduce additional system bias, further increasing the instrument's complexity. Finally, due to its complex composition and gas expansion design requirements, laser-induced fluorescence analyzers are relatively large, making them inconvenient for placement and mobile measurement. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the present invention provides a highly sensitive, miniaturized, and precise HOx radical measurement device and method for achieving highly sensitive and precise measurement of HOx radicals.

[0004] To achieve the above objectives, the present invention adopts the following technical solution, including:

[0005] A highly sensitive, miniaturized, and precise HOx radical measurement device, comprising: a radical generation and removal device, a light source module, a longitudinal HOx dual-chamber, a gas distribution module, and a data acquisition and control system;

[0006] The free radical generation and removal device is used to generate HOx free radicals or remove OH free radicals, and it is installed at the top of the longitudinal HOx dual cavity;

[0007] The light source module is used to emit a laser that causes OH free radicals to fluoresce and transmit it into the longitudinal HOx dual cavity;

[0008] The longitudinal HOx dual cavity is used to laser-excite OH free radicals to generate fluorescence, and the fluorescence is collected and converted into an electrical signal;

[0009] The gas distribution module is used for injecting gas into the device and maintaining the airflow state.

[0010] The acquisition and control system is used to monitor and control the working status of the free radical generation and removal device and the gas distribution module, and at the same time to acquire and process the fluorescent photoelectric signals output from the longitudinal HOx dual chamber.

[0011] Preferably, the free radical generation and removal device includes: a quartz flow tube for generating or removing OH free radicals; a base for mounting and fixing the quartz flow tube and related components; a mercury lamp for emitting ultraviolet light to photolyze oxygen and water contained in humid synthetic air to generate HOx free radicals; a mercury lamp mounting base for mounting the mercury lamp and related components; a front connecting light tube for connecting the mercury lamp mounting base and the base; a photodiode for detecting the intensity of ultraviolet light; a photodiode mounting cylinder for mounting the photodiode and related components; and a rear connecting light tube for connecting the photodiode mounting cylinder and the base.

[0012] The front connecting light tube is provided with a mercury lamp, a mercury lamp collimating lens, a movable grating plate, and a fixed grating plate arranged sequentially along the ultraviolet light propagation direction; wherein, the movable grating plate and the fixed grating plate cooperate to adjust the light intensity of the mercury lamp irradiating the quartz flow tube.

[0013] The rear connecting optical tube is sequentially provided with a bandpass filter, a focusing lens, and a photodiode along the ultraviolet light propagation direction;

[0014] The quartz flow tube is used to inject humidified synthetic air; a through hole is provided around the position above the ultraviolet light path in the quartz flow tube for a capillary dispensing needle to be inserted into the quartz flow tube, and the capillary dispensing needle is used to inject propane gas into the quartz flow tube; the bottom of the quartz flow tube is provided with a gas outlet for the gas to flow out.

[0015] Preferably, the longitudinal HOx dual cavity includes: two fluorescent excitation cavities stacked vertically for exciting OH free radicals to generate fluorescence; a sampling nozzle for sampling the gas in the free radical generation and removal device into the upper fluorescent excitation cavity; a laser collimating lens for collimating the laser emitted from the light source module; a plane mirror and an off-axis parabolic mirror for turning the collimated laser beam into the lower fluorescent excitation cavity and performing secondary collimation; a laser energy meter for measuring the laser energy emitted from the lower fluorescent excitation cavity; and a protective gas annular injection pipe and a conversion gas annular injection pipe for injecting nitrogen and nitric oxide into the longitudinal HOx dual cavity, respectively.

[0016] Two fluorescence excitation cavities are symmetrically installed, one above the other. A protective gas annular injection tube is installed at the lower part of the sampling nozzle, and a conversion gas annular injection tube is installed between the two fluorescence excitation cavities. Several small holes are opened at the lower part of the circumference of the protective gas annular injection tube, and several small holes are opened at the inner side of the circumference of the conversion gas annular injection tube. The diameter of the conversion gas annular injection tube is larger than the diameter of the protective gas annular injection tube. A vacuum pump is connected to the bottom of the lower fluorescence excitation cavity. A laser collimating lens is installed at the light inlet of the upper fluorescence excitation cavity. A plane mirror is installed at the light outlet of the upper fluorescence excitation cavity. An off-axis parabolic mirror is installed at the light inlet of the lower fluorescence excitation cavity. A laser energy meter is installed at the light outlet of the lower fluorescence excitation cavity.

[0017] Preferably, a single fluorescence excitation cavity includes: a fluorescence cavity body, a photomultiplier tube for detecting fluorescence intensity, a bandpass filter, an incident optical arm for reducing stray light from the laser beam during incident, an exit optical arm for reducing stray light from the laser beam during exit, an incident convex cylindrical mirror and an exit convex cylindrical mirror for deflecting the collimated laser beam, an incident concave cylindrical mirror and an exit concave cylindrical mirror for reflecting the laser beam back and forth multiple times, a front concave spherical mirror and a rear concave spherical mirror for reflecting and focusing the fluorescence, and a concave spherical lens for collimating the fluorescence reflected by the front concave spherical mirror and the rear concave spherical mirror.

[0018] The main body of the fluorescence cavity is a square hollow structure with left and right symmetry. An incident optical arm and an exit optical arm are respectively provided on the left and right sides. The incident optical arm and the exit optical arm are symmetrical. A quartz window is provided on the end face of each of them located on the outside of the main body of the fluorescence cavity. Two conical apertures are installed inside each of them, with the larger opening of the aperture facing inward and the smaller opening facing outward.

[0019] The concave cylindrical reflector at the incident end and the concave cylindrical reflector at the exit end have the same structure and size, and are symmetrically installed on the left and right sides inside the main body of the fluorescence cavity, respectively.

[0020] The front concave spherical mirror and the rear concave spherical mirror are respectively installed on the front and rear sides inside the main body of the fluorescence cavity. The focal length of the front concave spherical mirror is more than twice the focal length of the rear concave spherical mirror. The focal point of the rear concave spherical mirror is located at the center of the main body of the fluorescence cavity. A through hole is opened at the center of the rear concave spherical mirror. The front concave spherical mirror, the rear concave spherical mirror, the concave spherical lens, the bandpass filter, and the photomultiplier tube are coaxially installed in sequence.

[0021] Preferably, the gas distribution module provides the following gases to the device;

[0022] Dry synthetic air is introduced into the water bottle group through flow meter No. 1 to become humidified synthetic air. The humidified synthetic air is mixed with the dry synthetic air flowing through flow meter No. 2 to become humidified synthetic air with adjustable water vapor concentration. The humidified synthetic air is mixed with carbon monoxide gas flowing out of flow meter No. 3 and then flows through the temperature and humidity sensor and is injected into the blowing pipe. The blowing pipe is used to blow humidified synthetic air into the quartz flow tube in the free radical generation and removal device. The temperature and humidity sensor is used to measure the temperature and humidity of the synthetic air injected into the blowing pipe.

[0023] The first stream of nitrogen gas is injected into the space connecting the mercury lamp and the photodiode through flow meter No. 4.

[0024] The second stream of nitrogen gas is injected from the protective gas annular injection pipe into the area around the top of the sampling gas flow through the No. 5 flow meter;

[0025] Propane gas is injected into the quartz flow tube through flow meter No. 6;

[0026] Nitric oxide gas was injected from the conversion gas annular injection pipe into the periphery of the middle of the sampling gas flow through flow meter No. 7;

[0027] The air pump is connected to the downward flow outlet at the bottom of the quartz flow tube via flow meter No. 8, causing the quartz flow tube to generate a downward airflow.

[0028] Preferably, the acquisition and control system includes: an ozone analyzer for measuring the ozone concentration in the gas flowing out from the bottom of the quartz flow tube; a microcontroller for controlling all electrical components in the device to simultaneously acquire signals from the temperature and humidity sensor and the photodiode; and an industrial control computer for receiving signals from the laser energy meter and the photomultiplier tubes in the two fluorescence excitation cavities and controlling and reading the signals from the microcontroller.

[0029] Preferably, the light source module includes: a laser for emitting a laser that causes OH free radicals to fluoresce, an optical fiber for transmitting the laser, and a coupling lens for focusing and coupling the laser into the optical fiber.

[0030] This invention also provides a highly sensitive, miniaturized, and precise measurement method for HOx free radicals, applied to the aforementioned highly sensitive, miniaturized, and precise measurement device for HOx free radicals. The method for capturing the trend of HOx free radical concentration changes is as follows:

[0031] Set three measurement states:

[0032] Measurement State 1: The output wavelength of the laser is locked at the fluorescence excitation peak of the OH free radical, and the propane gas injection is turned off by the No. 6 flow meter. During this period, the average signal measured by the upper fluorescence excitation cavity is S(OH)1, the average signal measured by the lower fluorescence excitation cavity is S(HO2)1, and the average signal measured by the laser energy meter is P1. This state is maintained for time t1.

[0033] Measurement State 2: The output wavelength of the laser is locked at the fluorescence excitation peak of OH free radicals. The No. 6 flow meter is turned on to inject propane gas into the quartz flow tube. The propane removes OH free radicals in the ambient atmosphere. During this period, the average signal measured by the upper fluorescence excitation cavity is S(OH)2, the average signal measured by the lower fluorescence excitation cavity is S(HO2)2, and the average signal measured by the laser energy meter is P2. This state is maintained for time t2.

[0034] Measurement State 3: The output wavelength of the laser is adjusted to be far away from the fluorescence excitation peak of OH free radicals, and the propane gas injection is turned off by flow meter No. 6. At this time, the laser and OH free radicals do not produce fluorescence. During this period, the average signal measured by the upper fluorescence excitation cavity is S(OH)3, the average signal measured by the lower fluorescence excitation cavity is S(HO2)3, and the average signal measured by the laser energy meter is P3. This state is maintained for time t3.

[0035] In actual measurement, the three measurement states are switched in a cycle. In these three measurement states, the position of the moving grating plate is adjusted so that the intensity of the ultraviolet light detected by the photodiode is zero, that is, the ultraviolet light emitted by the mercury lamp is completely blocked by the moving grating plate and the fixed grating plate.

[0036] The method for capturing the trend of OH free radical concentration changes is as follows:

[0037] First, in measurement state one, ambient air is drawn into the quartz flow tube and then drawn into the upper and lower fluorescence excitation cavities by the sampling nozzle. At this time, the signal S(OH)1 measured by the upper fluorescence excitation cavity is the sum of the real fluorescence signal of atmospheric OH, the OH interference signal and the background signal of the upper fluorescence excitation cavity. During this period, the average value of the signal measured by the laser energy meter is P1.

[0038] Then, in measurement state two, propane removes the OH free radicals that are drawn into the quartz flow tube. At this time, the signal S(OH)2 measured by the upper fluorescence excitation cavity is the sum of the OH interference signal and the background signal of the upper fluorescence excitation cavity. During this period, the average value of the signal measured by the laser energy meter is P2.

[0039] Finally, in measurement state three, the laser interacts with the OH free radical and does not produce fluorescence. At this time, the signal S(OH)3 measured by the upper fluorescence excitation cavity is the background signal of the upper fluorescence excitation cavity, and the average value of the signal measured by the laser energy meter during this period is P3.

[0040] The changing trend is the trend of the actual concentration of atmospheric OH free radicals.

[0041] The changing trend is the changing trend of the OH interference signal;

[0042] The method for capturing the trend of HO2 free radical concentration changes is as follows:

[0043] First, in measurement state one, ambient air is drawn into the quartz flow tube and then into the upper and lower fluorescence excitation chambers by sampling nozzle 2. Atmospheric HO2 free radicals are partially converted into OH free radicals by NO between the upper and lower fluorescence excitation chambers. At this time, the signal S(HO2)1 measured by the lower fluorescence excitation chamber is the sum of the fluorescence signal of atmospheric HO2 converted into OH, the background signal of the lower fluorescence excitation chamber, the real fluorescence signal of atmospheric OH, and the OH interference signal. During this period, the average value of the signal measured by the laser energy meter is P1.

[0044] Then, in state two, propane removes the OH radicals drawn into the quartz flow tube. At this time, the signal S(HO2)2 measured in the lower fluorescence excitation chamber is atmospheric HO. 2转化的 The sum of the fluorescence signal of OH, the background signal of the lower fluorescence excitation cavity, and the interference signal of OH, during which the average value of the signal measured by the laser energy meter is P2;

[0045] Finally, in measurement state three, the laser interacts with the OH free radical and does not produce fluorescence. At this time, the signal S(HO2)3 measured by the lower fluorescence excitation cavity is the background signal of the lower fluorescence excitation cavity, and the average value of the signal measured by the laser energy meter during this period is P3.

[0046] The changing trend is the trend of the actual concentration of atmospheric HO2 free radicals; where k is the ratio of the detection sensitivity of the upper and lower fluorescence excitation cavities.

[0047] This invention also provides a highly sensitive, miniaturized, and precise measurement method for HOx radicals, applied to the aforementioned highly sensitive, miniaturized, and precise measurement device for HOx radicals. The method utilizes a photomultiplier tube to lock the peak of the fluorescence spectrum, as detailed below:

[0048] Turn off the humidified synthetic air and carbon monoxide gas injected into the blowing pipe, and turn off the propane gas injected into the quartz flow tube;

[0049] Adjusting the position of the movable grating plate maximizes the intensity of ultraviolet light emitted by the mercury lamp detected by the photodiode. At this point, the ultraviolet light will photolyze water vapor in the ambient atmosphere, thereby generating OH free radicals.

[0050] Then, the light source module begins to adjust the wavelength of the emitted laser within a certain range. At this time, the fluorescence signal detected by the photomultiplier tube in the upper fluorescence excitation cavity also changes accordingly. After the scan is completed, the wavelength of the laser emitted by the light source module is positioned at the position where the fluorescence signal is highest.

[0051] The present invention also provides a computer program product comprising a computer program / instructions that, when executed by a processor, implement the above-described highly sensitive, miniaturized, and precise measurement method for HOx free radicals.

[0052] The advantages of this invention are:

[0053] (1) This invention provides a highly sensitive, miniaturized, and precise HOx radical measurement device. It aims to capture the trend of HOx radical concentration changes even in environments with lower HOx radical concentrations, and to quickly obtain the instrument's detection sensitivity at multiple different times throughout the day. Furthermore, during calibration, it outputs HOx radical concentrations close to the actual HOx radical concentration in the local environment to reduce system measurement errors. In addition, the use of efficient OH radical scavenging technology combined with the calibration device enables accurate subtraction of unknown interference signals. Simultaneously, it allows for peak locking of fluorescence spectra using the photomultiplier tube itself, thereby improving the response sensitivity and measurement accuracy of the laser-induced fluorescence spectrometer for HOx radical measurement. The compact structural design and multi-functional design concept reduce the overall size of the device, making it easy to place and move for measurement.

[0054] (2) The fluorescence excitation cavity of the device of the present invention adopts an optical structure combining two convex cylindrical mirrors and two concave cylindrical mirrors to realize multiple reflections of the laser back and forth. The central axis of the path of multiple laser reflections is tangent to the center of the fluorescence excitation cavity. This makes the multiple fluorescence excitation points of the laser on the sampling gas flow all near the center of the fluorescence excitation cavity, thereby significantly enhancing the fluorescence intensity after repeated excitation.

[0055] (3) The fluorescence collection mirror group of the fluorescence excitation cavity of the device of the present invention adopts a reflective structure. Compared with the transmission collection mirror group commonly used in laser-induced fluorescence instruments, the reflective collection mirror group of the device of the present invention has a larger light-receiving surface and a smaller external volume. Moreover, the transmittance of the ultraviolet fused silica lens after being coated with an ultraviolet-enhancing film is often lower than the reflectance of the reflective mirror after being coated with an ultraviolet-reflective medium film. This makes the fluorescence excitation cavity of the device of the present invention have higher fluorescence collection efficiency and smaller volume.

[0056] (4) The free radical generation and removal device of the present invention can not only realize the quantitative generation of HOx free radicals, but also has the function of efficiently removing OH free radicals to obtain accurate background signals of the instrument. The combined design of the two also has the function of peak locking of fluorescence spectrum. This makes it possible to eliminate the need for an additional laser wavelength calibration device, thereby reducing the overall size of the device.

[0057] (5) The free radical generation and scavenging device of the present invention can generate HOx free radicals of known concentration with a wide range of adjustable concentrations, thereby generating HOx free radicals of similar concentrations for calibration according to different actual atmospheric environments.

[0058] (6) The free radical generation and removal device of the present invention has the function of automatic and rapid calibration, thereby obtaining the detection sensitivity of the instrument at multiple different times of the day.

[0059] (7) The free radical generation and removal device of the present invention locks the peak of the fluorescence spectrum by using the photomultiplier tube in the fluorescence excitation cavity itself. This eliminates the systematic error caused by the photomultiplier tube in the additional laser wavelength calibration device and the photomultiplier tube in the fluorescence excitation cavity, and also allows the laser wavelength to be accurately locked at the optimal response wavelength of the photomultiplier tube in the fluorescence excitation cavity.

[0060] (8) Since the optical arms on both sides of the fluorescence excitation cavity of the laser-induced fluorescence instrument are relatively long, the superimposed dual-cavity fluorescence excitation design can effectively reduce the lateral size of the device and allow the two fluorescence excitation cavities to share a single vacuum pump. However, this increases the illumination distance of the collimated laser beam, resulting in a deterioration in the collimation effect of the laser beam at the lower fluorescence excitation cavity. This invention employs a collimation optical path design combining an aspherical plano-convex lens and an off-axis parabolic reflector, which greatly improves the collimation effect compared to conventional spherical plano-convex lenses. This effectively suppresses stray laser noise in the lower fluorescence excitation cavity, thereby improving the detection capability of the lower fluorescence excitation cavity. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the overall structure of a highly sensitive, miniaturized, and precise HOx radical measurement device provided in an embodiment of the present invention.

[0062] Figure 2 This is an isometric view of the free radical generation and scavenging device provided in an embodiment of the present invention.

[0063] Figure 3 This is a cross-sectional view of the free radical generation surface of the free radical generation and scavenging device provided in an embodiment of the present invention.

[0064] Figure 4 This is a cross-sectional view of the free radical removal surface of the free radical generation and removal device provided in an embodiment of the present invention.

[0065] Figure 5 This is a cross-sectional axonometric view of the mercury lamp mounting base and the components mounted thereon provided in an embodiment of the present invention.

[0066] Figure 6 This is a top view schematic diagram of the internal structure of the fluorescence excitation cavity provided in an embodiment of the present invention.

[0067] Figure 7 This is a comparison diagram of the external shape and structure of the protective gas annular injection pipe and the conversion gas annular injection pipe provided in the embodiments of the present invention.

[0068] The meanings of the reference numerals in the attached figures are as follows:

[0069] 1-Free radical generation and removal device; 101-Quartz flow tube; 102-Miniature stepper motor; 103-Mercury lamp; 104-Mercury lamp mounting base; 105-Front connecting optical tube; 106-Outlet vent; 107-Base; 108-Photodiode; 109-Photodiode mounting cylinder; 110-Rear connecting optical tube; 111-Upper sealing plate; 112-Removing agent connecting plate; 113-Precision threaded column; 114-Mercury lamp collimating lens; 115-Motor 116-Raster plate, 117-Telescopic spring post, 118-Fixed grating plate, 119-Lower sealing plate, 120-185nm bandpass filter, 121-Needle crimping plate, 122-Capillary dispensing needle, 2-Sampling nozzle, 3-Protective gas annular injection tube, 4-Water bottle assembly, 5-Flow meter 1, 6-Flow meter 2, 7-Flow meter 3, 8-Flow meter 4, 9-Flow meter 5, 10-Flow meter 6, 11-Flow meter 7 12-Industrial control computer, 13-Plane mirror, 14-Off-axis parabolic mirror, 15-Converting gas annular injection tube, 16-Fluorescence excitation cavity, 1601-Photomultiplier tube, 1602-308nm bandpass filter, 1603-Incident optical arm, 1604-Incident convex cylindrical mirror, 1605-Incident concave cylindrical mirror, 1606-Fluorescence cavity body, 1607-Front concave spherical mirror, 1608-Outgoing concave cylindrical mirror 1609-Outlet end convex cylindrical reflector, 1610-Outlet end optical arm, 1611-Backward concave spherical reflector, 1612-Concave spherical lens, 17-Laser energy meter, 18-Ozone analyzer, 19-Air pump, 20-Flow meter No. 8, 21-Laser, 22-Coupled lens, 23-Fiber optic cable, 24-Microcontroller, 25-Laser collimating lens, 26-Geared stepper motor, 27-Double parallelogram mechanism, 28-Air blowing pipe, 29-Temperature and humidity sensor. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] See Figure 1A highly sensitive, miniaturized HOx radical precision measurement device includes: a radical generation and removal device 1, a light source module, a longitudinal HOx dual-chamber, a gas distribution module, and a data acquisition and control system.

[0072] The free radical generation and scavenging device 1 is used to generate HOx free radicals of known concentration or to remove OH free radicals from the ambient atmosphere;

[0073] The light source module is used to emit a 308nm laser that causes OH free radicals to fluoresce and transmit it into the longitudinal HOx dual cavity;

[0074] The longitudinal HOx dual-cavity system is used to excite OH free radicals to generate a large amount of fluorescence and to efficiently collect the fluorescence and convert it into an electrical signal;

[0075] The gas distribution module is used for injecting gas into the device of the present invention and maintaining the airflow state.

[0076] The acquisition and control system is used to monitor and control the working status of the free radical generation and removal device 1 and the gas distribution module. At the same time, it acquires and processes the fluorescent photoelectric signals output from the longitudinal HOx dual chambers to obtain real-time and accurate data on the HOx free radical concentration.

[0077] See Figure 2 , Figure 3 , Figure 4 and Figure 5The free radical generation and removal device 1 includes: a quartz flow tube 101 for generating or removing OH free radicals; a miniature stepper motor 102 for driving the rotation of a precision threaded column 113; a mercury lamp 103 for emitting ultraviolet light to photolyze oxygen and water contained in humidified synthesis air to generate HOx free radicals; a mercury lamp mounting base 104 for mounting the mercury lamp 103 and related components; a front connecting light tube 105 for connecting the mercury lamp mounting base 104 and the base 107; and a quartz flow tube 101 for... The components include: a wall-mounted air outlet 106; a base 107 for mounting and fixing components such as the quartz flow tube 101; a photodiode 108 for detecting the intensity of ultraviolet light emitted by the mercury lamp 103; a photodiode mounting sleeve 109 for mounting the photodiode 108 and related components; a rear connecting light tube 110 for connecting the photodiode mounting sleeve 109 and the base 107; and an upper sealing plate 111 for sealing the upper end of the gap between the quartz flow tube 101 and the base 107. The components include: a propane gas purging agent connecting plate 112; a precision threaded post 113 for adjusting the up-and-down movement of the movable grating plate 115; a mercury lamp collimating lens 114 for collimating the ultraviolet light emitted by the mercury lamp 103; a movable grating plate 115 that cooperates with the fixed grating plate 117 to adjust the light intensity of the mercury lamp irradiating the quartz flow tube 101; and a telescopic spring post 116 that generates an elastic restoring force on the movable grating plate 115, which cooperates with the movable grating plate 115 to adjust the light intensity irradiated into the quartz flow tube 101. The system includes a fixed grating plate 117 for controlling the light intensity of the internal mercury lamp, a lower sealing plate 118 for sealing the lower end of the gap between the quartz flow tube 101 and the base 107, a focusing lens 119 for focusing the collimated mercury lamp light, a bandpass filter 120 for filtering out 185nm light from the emission line of the mercury lamp 103 except for 185nm light, a needle pressing plate 121 for pressing and sealing the capillary dispensing needle 122, and a capillary dispensing needle 122 for injecting propane into the quartz flow tube 101. In this embodiment, the mercury lamp 103 is a pencil-shaped mercury lamp.

[0078] Specifically, the quartz flow tube 101 is made of ultraviolet fused quartz and is installed at the center of the base 107. The base 107 has a through hole at its center with an inner diameter slightly larger than the outer diameter of the quartz flow tube 101. Sealing rings are installed at the upper and lower ends of the through hole, respectively sealed by an upper sealing plate 111 and a lower sealing plate 118, forming a gap around the base 107 between the quartz flow tube 101 and the base 107. The bottom of the base 107 has four outflow ports 106, the centers of which are flush with the bottom of the quartz flow tube 101. The mercury lamp mounting base 104 is a rectangular hollow structure. The mercury lamp 103 is mounted longitudinally on its leftmost side. An air hole communicating with the internal space is opened below the mercury lamp 103. A light-transmitting hole is opened in the middle of the lower light-emitting area near the mercury lamp 103. A mercury lamp collimating lens 114 is installed to the right of the light-transmitting hole. A movable grating plate 115 and a fixed grating plate 117 are respectively installed to the right of the mercury lamp collimating lens 114. Both the movable grating plate 115 and the fixed grating plate 117 have transverse light-blocking paths perpendicular to the quartz flow tube 101. The width of the light-blocking area of ​​the movable grating plate 115 and the fixed grating plate 117 is equal to the width of the light-transmitting area. The lower part of the movable grating plate 115 contacts the telescopic head of the telescopic spring column 116, and the upper part of the movable grating plate 115 contacts the lower end of the precision threaded column 113. The upper end of the precision threaded column 113 is connected to the output shaft of the micro stepper motor 102. The movable grating plate 115 can be moved up and down by the forward and reverse rotation of the micro stepper motor 102. The front connecting light tube 105 is a hollow cylindrical structure, which connects and fixes the mercury lamp mounting base 104 to the base 107. The photodiode mounting tube 109 is a cylindrical hollow structure. From left to right, a 185nm bandpass filter 120, a focusing lens 119, and a photodiode 108 are installed inside. An air hole communicating with the internal space is opened in the photodiode mounting tube 109 near the photodiode 108. There is a continuous space between the mercury lamp 103 and the photodiode 108, connected to the outside only by a vent hole on each of the mercury lamp mounting base 104 and the photodiode mounting cylinder 109. Four capillary dispensing needles 122 are mounted around the base 107 above the ultraviolet light path emitted by the mercury lamp 103. Four micro-holes are formed around the upper middle part of the quartz flow tube 101, from which the four capillary dispensing needles 122 extend, with each side extending approximately one-quarter of the inner diameter of the quartz flow tube 101. The left side of the cleaning agent connecting plate 112 has a threaded interface for connecting a propane line, and the right side has a conical hollow plunger for pressing and sealing the capillary dispensing needles 122. The needle crimping plate 121 is used to press and seal the capillary dispensing needles 122 onto the cleaning agent connecting plate 112.

[0079] See Figure 1The light source module includes: a laser 21 that emits a 308nm laser that causes OH free radicals to fluoresce, an optical fiber 23 for transmitting the 308nm laser, and a coupling lens 22 that focuses and couples the 308nm laser into the optical fiber 23.

[0080] See Figure 1 and Figure 7 The highly sensitive longitudinal HOx dual cavity includes: a sampling nozzle 2 for low-loss sampling; two superimposed fluorescence excitation cavities 16 for exciting OH free radicals to generate fluorescence; a laser collimating lens 25 for collimating the laser emitted from the fiber 23; a plane mirror 13 and an off-axis parabolic mirror 14 for redirecting the collimated laser beam into the lower fluorescence excitation cavity 16 and performing secondary collimation; a laser energy meter 17 for measuring the laser energy emitted from the lower fluorescence excitation cavity 16; and a protective gas annular injection tube 3 and a conversion gas annular injection tube 15 for injecting protective nitrogen and nitric oxide into the longitudinal HOx dual cavity.

[0081] Specifically, there are two fluorescence excitation cavities 16, stacked one on top of the other, arranged symmetrically. A sampling nozzle 2, a hollow cone with a small hole at the top, is installed at the top of the upper fluorescence excitation cavity 16. A protective gas annular injection pipe 3 is installed at the bottom of the sampling nozzle 2. A conversion gas annular injection pipe 15 is installed between the upper and lower fluorescence excitation cavities 16. A vacuum pump is connected to the bottom of the lower fluorescence excitation cavity 16, causing both fluorescence excitation cavities 16 to generate low pressure simultaneously, and the gas is injected into the two fluorescence excitation cavities 16 through the small hole at the top of the sampling nozzle 2. The laser collimating lens 25 is an aspherical plano-convex lens, installed at the light inlet of the upper fluorescence excitation cavity 16, converting the diverging laser emitted from the fiber optic 23 into a collimated laser beam. A plane mirror 13 is installed at the light outlet of the upper fluorescence excitation cavity 16, an off-axis parabolic mirror 14 is installed at the light inlet of the lower fluorescence excitation cavity 16, and a laser energy meter 17 is installed at the light outlet of the lower fluorescence excitation cavity 16. Figure 7 The upper part is the protective gas ring injection pipe 3, and several small holes are opened around its lower part. Figure 7 The lower one is the conversion gas annular injection pipe 15, which has several small holes on its inner circumference; the diameter of the conversion gas annular injection pipe 15 is larger than the diameter of the protective gas annular injection pipe 3, and both adopt a double-sided injection structure.

[0082] See Figure 6A single fluorescence excitation cavity 16 includes: a fluorescence cavity body 1606 for mounting all other components within the fluorescence excitation cavity 16; a photomultiplier tube 1601 for detecting fluorescence intensity; a 308nm bandpass filter 1602 for filtering out light other than 308nm; an incident optical arm 1603 for reducing stray light from the laser beam during incident; an exit optical arm 1610 for reducing stray light from the laser beam during exit; and a collimated laser beam generation... The laser beam is deflected by an incident convex cylindrical mirror 1604 and an exit convex cylindrical mirror 1609; an incident concave cylindrical mirror 1605 and an exit concave cylindrical mirror 1608, which cause the laser beam to reflect back and forth multiple times; a front concave spherical mirror 1607 and a rear concave spherical mirror 1611, which reflect and focus the fluorescence; and a concave spherical lens 1612, which collimates the fluorescence reflected by the front concave spherical mirror 1607 and the rear concave spherical mirror 1611.

[0083] Specifically, the main body of the fluorescence cavity 1606 is a symmetrical square hollow structure. Since the upper and lower fluorescence excitation cavities 16 are symmetrically installed, in this embodiment... Figure 6 Taking a collimated laser beam incident from the left and exiting from the right as an example, the fluorescence cavity body 1606 has an incident optical arm 1603 and an exit optical arm 1610 on its left and right sides, respectively. The incident optical arm 1603 and the exit optical arm 1610 have a symmetrical structure. Each of them has a high-transmittance ultraviolet fused silica window on its outer end face of the fluorescence cavity body 1606. Each of them has two conical apertures installed inside, with the larger aperture facing inward and the smaller aperture facing outward. The incident concave cylindrical mirror 1605 and the exit concave cylindrical mirror 1608 have the same structure and size and are symmetrically installed on the left and right sides inside the fluorescence cavity body 1606. The front concave spherical mirror 1607 is installed on the front side inside the fluorescence cavity body 1606 (i.e., the front concave spherical mirror 1607). Figure 6 The concave spherical mirror 1611 is installed on the rear side inside the fluorescent cavity body 1606 (i.e., below the center). Figure 6 (Above in the middle), the focal length of the front concave spherical mirror 1607 is slightly greater than twice that of the rear concave spherical mirror 1611. The focal point of the rear concave spherical mirror 1611 is located at the center of the fluorescent cavity body 1606, and a through hole is opened at the center of the rear concave spherical mirror 1611. The front concave spherical mirror 1607, the rear concave spherical mirror 1611, the concave spherical lens 1612, the 308nm bandpass filter 1602, and the photomultiplier tube 1601 are coaxially mounted in sequence.

[0084] See Figure 1The gas distribution module includes: a water-pass bottle group 4 for converting dry synthesis air into humid synthesis air; a flow meter 1 for controlling the flow rate of the water-pass synthesis air; a flow meter 2 for controlling the flow rate of dry synthesis air; a flow meter 3 for controlling the flow rate of carbon monoxide; a flow meter 4 for controlling the flow rate of nitrogen gas introduced into the free radical generation and removal device 1; a flow meter 5 for controlling the flow rate of the top protective nitrogen gas; a flow meter 6 for controlling the flow rate of propane; and a flow meter 7 for controlling the flow rate of nitric oxide. 11. An air pump 19 that generates a downward airflow in the quartz flow tube 101 within the free radical generation and removal device 1; 20. A flow meter 8 for controlling the pumping speed of the air pump 19; 28. An air blowing pipe 28 for blowing a uniform, high-flow-rate synthetic air to the top of the free radical generation and removal device 1; 27. A double parallelogram mechanism 27 for controlling the standing and folding of the air blowing pipe 28; 26. A speed-reducing stepper motor 26 for controlling the movement of the double parallelogram mechanism 27; and 29. A temperature and humidity sensor 29 for measuring the temperature and humidity of the synthetic air injected into the air blowing pipe 28.

[0085] Specifically, dry synthetic air is introduced into the water bottle group 4 through flow meter 5 and becomes humidified synthetic air. The humidified synthetic air is mixed with the dry synthetic air flowing through flow meter 6 and becomes humidified synthetic air with adjustable water vapor concentration. The humidified synthetic air with adjustable water vapor concentration is mixed with carbon monoxide gas flowing out of flow meter 7 and then flows through temperature and humidity sensor 29 and is injected into air blowing pipe 28. The first stream of nitrogen gas is injected through a vent on the mercury lamp mounting base 104 via flow meter 8 into the space connecting the mercury lamp 103 and the photodiode 108. The 185nm ultraviolet light emitted by the mercury lamp 103 is used to photolyze water vapor to generate OH radicals. The path from the mercury lamp to the photodiode and the aforementioned connecting space are connected to the ambient air, where gases such as oxygen and nitrous oxide may absorb the 185nm light. This absorption not only reduces the intensity of the 185nm light, but changes in the concentration of gases such as nitrous oxide, which strongly absorb 185nm light, can also cause instability in the intensity of the 185nm light. Therefore, continuously introducing nitrogen gas, which does not absorb 185nm ultraviolet light, into the connecting space can eliminate other gases and mitigate this effect. The second stream of nitrogen gas is injected through a protective gas annular injection pipe 3 via flow meter 9 into the area around the top of the sampling gas flow. Propane gas flows through flow meter 10 from the scavenger connection plate 112 to the capillary dispensing needle 122 and is then injected into the quartz flow tube 101. Nitric oxide gas is injected through flow meter 11 from the conversion gas annular injection tube 15 into the periphery of the middle of the sampling gas flow. Air pump 19 is connected to the four outflow ports 106 at the bottom of the free radical generation and scavenging device 1 via flow meter 20. The flow rate of the synthetic air injected into the blowing tube 28 is approximately twice the pumping flow rate of air pump 19.

[0086] See Figure 1 The acquisition and control system includes: an ozone analyzer 18 for measuring the ozone concentration in the gas flowing out from the bottom of the free radical generation and removal device 1; a microcontroller 24 for controlling the rotation of all motors in the device and simultaneously acquiring signals from the temperature and humidity sensor 29 and the photodiode 108; and an industrial control computer 12 for receiving signals from the laser energy meter 17 and two photomultiplier tubes 1601 and controlling and reading signals from the microcontroller 24.

[0087] Specifically, the industrial control computer 12 directly receives signals from the laser energy meter 17, two photomultiplier tubes 1601 and the ozone analyzer 18. The industrial control computer 12 indirectly receives signals from the temperature and humidity sensor 29 and the photodiode 108 through the microcontroller 24. The industrial control computer 12 indirectly controls the forward and reverse rotation of the micro stepper motor 102 and the geared stepper motor 26 through the microcontroller 24.

[0088] In this invention, a highly sensitive miniaturized HOx radical precision measurement method is used. This method employs a highly sensitive miniaturized HOx radical precision measurement device, which can capture the trend of HOx radical concentration changes, accurately subtract unknown interference signals, quickly obtain the detection sensitivity of the upper and lower fluorescence excitation cavities at different times throughout the day, and output HOx radical concentrations similar to the actual HOx radical concentrations under local conditions during calibration. Furthermore, it utilizes a photomultiplier tube 1601 to lock the peak of the fluorescence spectrum, thereby improving the response sensitivity and measurement accuracy of the laser-induced fluorescence instrument for HOx radical measurement. The specific process and principle are as follows:

[0089] (1) The process and principle of capturing OH free radical fluorescence signals in the upper fluorescence excitation chamber 16 of the device of the present invention: The air pump 19 draws ambient air into the quartz flow tube 101 and causes the ambient air to flow downward to the sampling nozzle 2. Since the two fluorescence excitation chambers 16 are connected vertically, the vacuum pump can simultaneously draw the two fluorescence excitation chambers 16 to a low pressure. The ambient air carrying HOx free radicals is drawn in from the sampling nozzle 2 and sprayed into the two fluorescence excitation chambers 16. At the same time as the sampling gas flow is sprayed downward from the center of the protective gas annular injection tube 3, nitrogen gas is introduced into the protective gas annular injection tube 3. The nitrogen gas flows downward through several small holes opened at the lower part of the circumference of the protective gas annular injection tube 3 to the circumference of the sprayed sampling gas flow, thereby forming a layer of clean protective gas to protect the cleanliness of the inside of the two fluorescence excitation chambers 16. The laser emitted by laser 21 is focused into the input head of optical fiber 23 by coupling lens 22. After exiting optical fiber 23, the diverging laser beam is collimated into a collimated laser beam by collimating lens 25. The laser beam enters the upper fluorescence excitation cavity 16 through the ultraviolet fused silica window on the input optical arm 1603. The laser beam is deflected by the convex cylindrical mirror 1604 at the input end and then by the concave cylindrical mirror 1608 at the output end. At this time, the laser beam is reflected multiple times between the concave cylindrical mirror 1608 at the output end and the concave cylindrical mirror 1605 at the input end. The reflected trajectories all pass near the center of the fluorescence excitation cavity 16. The laser beam, after multiple reflections, will conduct multiple reactions on the OH free radicals in the sampling gas stream. The excitation generates strong fluorescence. The upward-emitted portion of the fluorescence is reflected by the rear concave spherical mirror 1611 to the front concave spherical mirror 1607 and then reflected again. The downward-emitted portion of the fluorescence is reflected by the front concave spherical mirror 1607 and then focused into the vicinity of the concave spherical lens 1612 through the through-hole in the middle of the rear concave spherical mirror 1611. The collected fluorescence is collimated into a collimated fluorescence beam after passing through the concave spherical lens 1612. The collimated fluorescence beam is then irradiated onto the photosensitive surface of the photomultiplier tube 1601 through the 308nm bandpass filter 1602. The photomultiplier tube 1601 converts the fluorescence signal of OH free radicals into an electrical signal. At this time, the signal output by the photomultiplier tube 1601 in the upper fluorescence excitation cavity 16 and transmitted to the industrial control computer 12 is the fluorescence signal of OH free radicals.

[0090] (2) The process and principle of capturing the fluorescence signal of OH free radical converted from HO2 free radical in the lower fluorescence excitation cavity 16 of the device of the present invention: Nitric oxide is continuously introduced into the annular injection tube 15 of the conversion gas. Nitric oxide gas flows into the sampling gas flow through several small holes opened on the inner side of the annular injection tube 15 of the conversion gas. When it is near the annular injection tube 15 of the conversion gas, the HO2 free radical in the sampling gas flow is partially converted into OH free radical by nitric oxide. The laser beam in the upper fluorescence excitation cavity 16 is deflected after multiple reflections and strikes the convex cylindrical reflector 1609 at the exit end. Since the convex cylindrical reflectors 1604 at the incident end and 1609 at the exit end are convex cylindrical reflectors, the laser beam can be diverged. However, the concave cylindrical reflectors 1605 at the incident end and 1608 at the exit end are concave cylindrical reflectors, which can be focused. Therefore, after being reflected by these four cylindrical reflectors, the collimated laser beam is still a collimated laser beam coaxial with the collimated laser beam incident from the ultraviolet fused silica window of the optical arm 1603 at the incident end. The collimated laser beam reflected by the convex cylindrical reflector 1609 at the exit end exits from the ultraviolet fused silica window of the optical arm 1610 at the exit end. At this time, the collimated laser beam emitted from the upper fluorescence excitation cavity 16 is reflected by the plane mirror 13 and deflected downwards by 90 degrees before illuminating the off-axis parabolic mirror 14. Since the laser emitted from the fiber 23 is not an ideal point source, it is not an ideal collimated beam even after being collimated by the laser collimating lens 25. There will be divergence at a distance away from the laser collimating lens 25. The off-axis parabolic mirror 14 installed on the optical arm 1603 at the incident end of the lower fluorescence excitation cavity 16 can collimate the laser beam with a certain divergence a second time and reflect it into the lower fluorescence excitation cavity 16. At this time, the fluorescence excitation and collection process is the same as that in the upper fluorescence excitation cavity 16. The photomultiplier tube 1601 of the lower fluorescence excitation cavity 16 will convert the fluorescence signal of the OH free radical converted from nitric oxide into an electrical signal. At this time, the signal output by the photomultiplier tube 1601 of the lower fluorescence excitation cavity 16 and transmitted to the industrial control computer 12 is the fluorescence signal of the OH free radical converted from HO2 free radical.

[0091] (3) The process of capturing the concentration change trends of OH free radicals and HO2 free radicals by the device of the present invention includes the following three measurement states:

[0092] Measurement State 1 (HOx radical full signal measurement state): The output wavelength of laser 21 is locked at the fluorescence excitation peak of OH radical, and the propane gas injection is turned off by flow meter 10. During this period, the average signal measured by the upper fluorescence excitation cavity 16 is: S(OH)1=S(OH) 真实 +S(OH) 干扰 +S(OH) 背景 The average signal measured in the lower fluorescence excitation cavity 16 is: S(HO2)1=S(HO2) 真实+S(HO2) 背景 +S(OH) real +S(OH) interference, the average value of the signal measured by laser energy meter 17 is P1, and this state is maintained for 2 minutes;

[0093] Measurement State Two (Chemical Background Signal Measurement State): The output wavelength of laser 21 is locked at the fluorescence excitation peak of OH free radicals. Flow meter 10 is turned on to inject propane gas into the quartz flow tube 101. The propane removes OH free radicals from the ambient atmosphere. During this process, the average signal measured by the upper fluorescence excitation chamber 16 is: S(OH)2=S ... 干扰 +S(OH) 背景 The average signal measured in the lower fluorescence excitation cavity 16 is: S(HO2)2=S(HO2) 真实 +S(HO2) 背景 +S(OH) 干扰 The average value of the signal measured by laser energy meter 17 is P2, and this state is maintained for 2 minutes.

[0094] Measurement State 3 (Spectral Background Signal Measurement State): Adjust the output wavelength of laser 21 to be far away from the fluorescence excitation peak of OH free radicals, and shut off the propane gas injection of flow meter 10. At this time, the laser and OH free radicals do not produce fluorescence. During this period, the average signal measured by the upper fluorescence excitation cavity 16 is: S(OH)3=S ... 背景 The average signal measured in the lower fluorescence excitation cavity 16 is: S(HO2)3=S(HO2) 背景 The average value of the signal measured by laser energy meter 17 is P3, and this state is maintained for 1 minute.

[0095] In actual measurement, the three measurement states are switched cyclically within 5 minutes. In these three measurement states, the microcontroller 24 controls the deceleration stepper motor 26 to rotate and adjusts the position of the moving grating plate 115 so that the intensity of the mercury lamp detected by the photodiode 108 is zero. At this time, the mercury lamp is completely blocked by the moving grating plate 115 and the fixed grating plate 117.

[0096] (4) The principle of the device of the present invention for capturing the trend of OH free radical concentration is as follows:

[0097] First, in measurement state one, the air pump 19 draws ambient air into the quartz flow tube 101, and then the sampling nozzle 2 draws it into the upper and lower fluorescence excitation chambers 16. At this time, the signal S(OH)1 measured by the upper fluorescence excitation chamber 16 is the sum of the real fluorescence signal of atmospheric OH, the OH interference signal and the background signal of the upper fluorescence excitation chamber 16. During this period, the average value of the signal measured by the laser energy meter 17 is P1.

[0098] Then, in measurement state two, propane removes the OH free radicals drawn into the quartz flow tube 101. At this time, the signal S(OH)2 detected by the upper fluorescence excitation cavity 16 is the sum of the OH interference signal and the background signal of the upper fluorescence excitation cavity 16. During this period, the average value of the signal measured by the laser energy meter 17 is P2.

[0099] Finally, in measurement state three, the laser interacts with the OH free radical and does not produce fluorescence. At this time, the signal S(OH)3 detected by the upper fluorescence excitation cavity 16 is the background signal of the upper fluorescence excitation cavity 16, and the average value of the signal measured by the laser energy meter 17 during this period is P3.

[0100] but The changing trend is the trend of the actual concentration of atmospheric OH free radicals. The changing trend of OH interference signal is the changing trend of OH interference signal, which can be used to analyze the source of interference.

[0101] (5) The principle of the device of the present invention for capturing the trend of HO2 free radical concentration is as follows:

[0102] First, in measurement state one, the air pump 19 draws ambient air into the quartz flow tube 101, and then the sampling nozzle 2 draws it into the upper and lower fluorescence excitation chambers 16. Atmospheric HO2 free radicals are partially converted into OH free radicals by NO between the upper and lower fluorescence excitation chambers 16. At this time, the signal S(HO2)1 measured by the lower fluorescence excitation chamber 16 is the sum of the fluorescence signal of atmospheric HO2 converted into OH, the background signal of the lower fluorescence excitation chamber 16, the true fluorescence signal of atmospheric OH, and the OH interference signal. During this period, the average value of the signal measured by the laser energy meter 17 is P1.

[0103] Then, during measurement state two, propane removes OH radicals from the quartz flow tube 101. At this time, the signal S(HO2)2 detected by the lower fluorescence excitation chamber 16 is atmospheric HO. 2转化的 The sum of the fluorescence signal of OH, the background signal of the lower fluorescence excitation cavity 16, and the OH interference signal, during which the average value of the signal measured by the laser energy meter 17 is P2.

[0104] Finally, in measurement state three, the laser interacts with the OH free radical and does not produce fluorescence. At this time, the signal S(HO2)3 detected by the lower fluorescence excitation cavity 16 is the background signal of the lower fluorescence excitation cavity 16, and the average value of the signal measured by the laser energy meter 17 during this period is P3.

[0105] but The changing trend is the trend of the actual concentration of atmospheric HO2 free radicals, where k is the ratio of the detection sensitivity of the upper and lower fluorescence excitation cavities 16.

[0106] (6) The process and principle of the device of the present invention to quickly obtain the detection sensitivity of the upper and lower fluorescence excitation cavities at different times of the day: The propane gas injected into the quartz flow tube 15 is shut off, and the fourth flow meter 8 controls a small flow of nitrogen gas to continuously flow into the connecting space between the mercury lamp 103 and the photodiode 108, thereby eliminating the influence of the ultraviolet light emitted by the mercury lamp being absorbed by other gases. The microcontroller 24 controls the decelerated stepper motor 26 to rotate forward, and the double parallelogram mechanism 27 drives the air blowing pipe 28 to be raised to a position with an angle of 45 degrees with the quartz flow tube 101, and the air outlet direction of the air blowing pipe 28 is facing the center of the top of the quartz flow tube 101. Then, the first flow meter 5 and the second flow meter 6 are turned on. The synthetic air becomes humid synthetic air with adjustable water vapor concentration after passing through the first flow meter 5, the water bottle group 4, and the second flow meter 6. The humid synthetic air is then introduced into the air blowing pipe 28 after passing through the temperature and humidity sensor 29. At this time, the water vapor concentration in the synthetic air measured by the temperature and humidity sensor is [H2O]. About half of the humidified synthetic air, blown out through the air pipe 28, is drawn into the quartz flow tube 101. The microcontroller 24 controls the rotation of the decelerated stepper motor 26. At this time, the ultraviolet light emitted by the mercury lamp 103 passes sequentially through the mercury lamp collimating lens 114, the moving grating plate 115, and the fixed grating plate 117, illuminating the downward-flowing humidified synthetic air inside the quartz flow tube 101, causing photolysis of the humidified synthetic air. The concentrations of the generated OH radicals and HO2 radicals are [OH] and [HO2], respectively, and [OH] = [HO2]. Then, the mercury lamp passes sequentially through the 185nm bandpass filter-120 and the focusing lens 119, illuminating the photosensitive surface of the photodiode 108. At this time, the microcontroller 24 receives the output voltage of the photodiode 108 as V, the ozone analyzer 18 synchronously measures the ozone concentration as [O3], and the electrical signal output by the photomultiplier tube 1601 of the upper fluorescence excitation cavity 16 is S'. OH The signal from laser energy meter 17 is P'.

[0107] Based on equation (1), the sensitivity C of the upper fluorescence excitation cavity 16 for measuring OH free radicals is calculated. OH for:

[0108]

[0109] in, and These are the oxygen absorption cross section and the water vapor absorption cross section, respectively. These two parameters are fixed values ​​obtained from the literature. [O2] is the concentration of oxygen in the synthetic air inside the quartz flow tube 101, which is a factory value from the gas distribution company. k1 is the ratio of the laser energy in the upper fluorescence excitation cavity 16 to the laser energy irradiating the laser energy meter 17, which is a fixed value determined in advance in the laboratory.

[0110] Subsequently, flow meter 7 11 first shuts off the injection of nitric oxide gas. At this time, the electrical signal output by photomultiplier tube 1601 in the lower fluorescence excitation chamber 16 is S'. HO2 Then, flow meter 7 is turned on, and flow meter 7 controls the injection of nitric oxide gas through the conversion gas annular injection pipe 15 into the upper part of the lower fluorescence excitation chamber 16. At this time, some HO2 is converted into OH free radicals, and the electrical signal output by the photomultiplier tube 1601 in the lower fluorescence excitation chamber 16 is S. HO2,NO Finally, flow meter 7 controls the injection of carbon monoxide gas along with the moistened synthesis air into the blowing pipe 28. After being drawn into the quartz flow tube 101, the carbon monoxide gas completely converts OH radicals into HO2 radicals. Flow meter 11 maintains the injection of nitric oxide gas. At this time, the photomultiplier tube 1601 in the lower fluorescence excitation chamber 16 outputs an electrical signal of S. HO2,NO+CO .

[0111] Based on equation (2), the sensitivity C of the lower fluorescence excitation cavity 16 for measuring HO2 free radicals is calculated. HO2 for:

[0112]

[0113] Wherein, ρ is the proportion of HO2 radicals converted to OH radicals by nitric oxide input from the annular injection pipe 15. k2 is the ratio of the laser energy in the lower fluorescence excitation cavity 16 to the laser energy irradiating the laser energy meter 17, which is a pre-determined value in the laboratory. Since the entire calibration process is completed within ten minutes, the signals measured by the laser energy meter 17 and the ozone analyzer 18 are still P' and [O3].

[0114] Since the output voltage V of photodiode 108 and the ozone concentration [O3] measured by ozone analyzer 18 are linearly related, equations (1) and (2) can be rewritten as equations (3) and (4) respectively:

[0115]

[0116] Wherein, k3 is the ratio of the output voltage V of photodiode 108 to the ozone concentration [O3] measured by ozone analyzer 18, which is a fixed value measured in advance in the laboratory. In actual field observations, photodiode 108 can be used instead of ozone analyzer 18, thereby further reducing the overall size of the device.

[0117] Since the entire process of acquiring the detection sensitivity of the upper and lower fluorescence excitation cavities 16 is achieved by automated control, the acquisition of a single detection sensitivity is completed within 10 minutes, which is far more efficient than manual operation. Therefore, the detection sensitivity at different times of the day can be obtained. Finally, the real-time concentration of HOx free radicals can be obtained by dividing the real-time measured fluorescence signal by the product of the nearest calibrated detection sensitivity and the laser energy.

[0118] (7) The principle of the device of the present invention to output HOx free radicals with a concentration close to the actual HOx free radical concentration in the local environment: The propane gas injected into the quartz flow tube 15 is shut off. The light-blocking design of the moving grating plate 115 and the fixed grating plate 117 ensures that the passing mercury lamp light (ultraviolet light) remains uniform in the direction perpendicular to the quartz flow tube 101. The microcontroller 24 controls the rotation of the decelerated stepper motor 26, which drives the precision threaded column 113 to rotate. The precision threaded column 113 pushes the moving grating plate 115 up and down. The mutual movement between the moving grating plate 115 and the fixed grating plate 117 causes a change in the intensity of the mercury lamp light irradiating the quartz flow tube 101, and the concentration of OH free radicals and HO2 free radicals also changes accordingly. Therefore, the concentration of HOx free radicals with a concentration close to the actual HOx free radical concentration in the local environment can be adjusted according to the intensity of the fluorescence signal.

[0119] (8) The device of this invention utilizes the principle of photomultiplier tube 1601 itself to accurately lock the peak of the fluorescence spectrum: the microcontroller 24 controls the deceleration stepper motor 26 to reverse, the double parallelogram mechanism 27 drives the air blowing tube 28 to retract, shutting off the humidified synthetic air and carbon monoxide gas injected into the air blowing tube 28, and shutting off the propane gas injected into the quartz flow tube 15. The microcontroller 24 controls the deceleration stepper motor 26 to rotate, adjusting the position of the moving grating plate 115 so that the light intensity (ultraviolet light intensity) of the mercury lamp detected by the photodiode 108 reaches the maximum. At this time, the mercury lamp will photolyze the water vapor in the ambient atmosphere, thereby generating a high concentration of OH free radicals. Then, the laser 21 begins to slowly adjust the wavelength of the output laser within a certain range. At this time, the fluorescence signal detected by the photomultiplier tube 1601 in the upper fluorescence excitation cavity 16 also changes accordingly. After the scan is completed, the wavelength of the laser 21 is positioned at the position of the highest fluorescence signal.

[0120] The conventional method for peak locking is to use an additional laser wavelength calibration device. This device uses a high-temperature filament to generate a high concentration of OH radicals, and changes the wavelength of the laser to obtain the fluorescence signal, thereby accurately locking the fluorescence spectral peak of the OH radicals.

[0121] Because this invention uses the photomultiplier tube 1601 of the fluorescence excitation cavity 16 itself to lock the fluorescence spectral line, compared with the conventional method of additionally equipping a laser wavelength calibration device, this invention does not have the problem of the response peak of the photomultiplier tube in the laser wavelength calibration device and the photomultiplier tube in the low-pressure fluorescence detection cavity being deviated. In addition, the fluorescence excitation cavity of this invention has the characteristic of very high detection sensitivity, which allows the laser wavelength to be positioned at the position where the instrument sensitivity is best, and the process of locking the fluorescence spectral line peak can be performed once every hour.

[0122] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. 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 present invention.

Claims

1. A high-sensitivity miniaturized HOx radical precision measurement device, characterized in that, The device comprises: a radical generation and elimination device (1), a light source module, a longitudinal HOx double cavity, a gas distribution module, a collection and control system; the radical generation and elimination device (1) is used for generating HOx radicals or eliminating OH radicals, and is installed at the top end of the longitudinal HOx double cavity; the light source module is used for emitting laser that makes OH radicals generate fluorescence and transmitting into the longitudinal HOx double cavity; the longitudinal HOx double cavity is used for exciting OH radicals to generate fluorescence by laser and collecting and converting the fluorescence into an electric signal; the gas distribution module is used for injecting gas in the device and maintaining the flow state of the gas flow; the collection and control system is used for monitoring and controlling the working state of the radical generation and elimination device (1) and the gas distribution module, and collecting and processing the fluorescence photoelectric signal output by the longitudinal HOx double cavity; the longitudinal HOx double cavity comprises: two fluorescence excitation cavities (16) installed in an upper-lower superposition mode for exciting OH radicals to generate fluorescence, a sampling nozzle (2) for sampling gas in the radical generation and elimination device (1) to the upper fluorescence excitation cavity (16), a laser collimating lens (25) for collimating the laser emitted by the light source module, a plane mirror (13) and an off-axis parabolic mirror (14) for turning the collimated laser beam into the lower fluorescence excitation cavity (16) and performing secondary collimation, a laser energy meter (17) for measuring the laser energy emitted from the lower fluorescence excitation cavity (16), and a protective gas annular injection pipe (3) and a conversion gas annular injection pipe (15) for respectively injecting nitrogen and nitric oxide into the longitudinal HOx double cavity; the upper and lower fluorescence excitation cavities (16) are installed in a left-right symmetry mode; the protective gas annular injection pipe (3) is installed at the lower part of the sampling nozzle (2), the conversion gas annular injection pipe (15) is installed between the upper and lower fluorescence excitation cavities (16), a plurality of small holes are formed in the lower part of the periphery of the protective gas annular injection pipe (3), a plurality of small holes are formed in the inner side of the periphery of the conversion gas annular injection pipe (15), the diameter of the conversion gas annular injection pipe (15) is greater than that of the protective gas annular injection pipe (3); the bottom of the lower fluorescence excitation cavity (16) is connected with a vacuum pump; the laser collimating lens (25) is installed at the light inlet of the upper fluorescence excitation cavity (16); the plane mirror (13) is installed at the light outlet of the upper fluorescence excitation cavity (16); the off-axis parabolic mirror (14) is installed at the light inlet of the lower fluorescence excitation cavity (16); and the laser energy meter (17) is installed at the light outlet of the lower fluorescence excitation cavity (16). The single fluorescence excitation cavity (16) comprises: a fluorescence cavity body (1606), a photomultiplier tube (1601) for detecting fluorescence intensity, a band-pass filter two (1602), an incident end light arm (1603) for reducing stray light when the laser beam is incident, an exit end light arm (1610) for reducing stray light when the laser beam is emitted, an incident end convex cylindrical mirror (1604) and an exit end convex cylindrical mirror (1604) for deflecting the collimated laser beam, an incident end concave cylindrical mirror (1605) and an exit end concave cylindrical mirror (1608) for making the laser beam reflect back and forth multiple times, a front concave spherical mirror (1607) and a rear concave spherical mirror (1611) for reflecting and focusing the fluorescence, and a concave spherical lens (1612) for collimating the fluorescence reflected by the front concave spherical mirror (1607) and the rear concave spherical mirror (1611); The fluorescence cavity body (1606) is a left-right symmetrical square hollow structure, and the left and right sides are respectively provided with the incident end light arm (1603) and the exit end light arm (1610). The incident end light arm (1603) and the exit end light arm (1610) are symmetrical structures, and each of the two is provided with a quartz window piece on the end face outside the fluorescence cavity body (1606). The two are respectively provided with two tapered diaphragms, and the large opening of the diaphragm faces inward, and the small opening faces outward. The incident end concave cylindrical mirror (1605) and the exit end concave cylindrical mirror (1608) are symmetrical structures, and are respectively installed on the left and right sides inside the fluorescence cavity body (1606). The front concave spherical mirror (1607) and the rear concave spherical mirror (1611) are respectively installed on the front and rear sides inside the fluorescence cavity body (1606). The focal length of the front concave spherical mirror (1607) is greater than twice the focal length of the rear concave spherical mirror (1611). The focal point of the rear concave spherical mirror (1611) is located at the center of the fluorescence cavity body (1606), and a through hole is formed in the center of the rear concave spherical mirror (1611). The front concave spherical mirror (1607), the rear concave spherical mirror (1611), the concave spherical lens (1612), the band-pass filter two (1602) and the photomultiplier tube (1601) are coaxially installed in sequence. The upper fluorescence excitation cavity (16) captures the OH free radical fluorescence signal in the sampling gas flow; The lower fluorescence excitation cavity (16) captures the OH free radical fluorescence signal converted by the HO2 free radical in the sampling gas flow.

2. The high-sensitivity miniaturized HOx radical precision measurement device according to claim 1, characterized in that The radical generation and elimination device (1) comprises a quartz flow tube (101) for OH radical generation or elimination, a base (107) for mounting and fixing the quartz flow tube (101) and related components, a mercury lamp (103) for emitting ultraviolet light to photolyze oxygen and water contained in humid synthetic air to generate HOx radicals, a mercury lamp mounting seat (104) for mounting the mercury lamp (103) and related components, a front connecting light cylinder (105) for connecting the mercury lamp mounting seat (104) and the base (107), a photodiode (108) for detecting the intensity of ultraviolet light, a photodiode mounting cylinder (109) for mounting the photodiode (108) and related components, and a rear connecting light cylinder (110) for connecting the photodiode mounting cylinder (109) and the base (107). The front connecting light cylinder (105) is sequentially provided with the mercury lamp (103), a mercury lamp collimating lens (114), a movable grating plate (115), and a fixed grating plate (117) in the direction of ultraviolet light propagation; the movable grating plate (115) and the fixed grating plate (117) cooperate to adjust the intensity of mercury lamp light irradiated into the quartz flow tube (101). The rear connecting light cylinder (110) is sequentially provided with a band-pass filter (120), a focusing lens (119), and the photodiode (108) in the direction of ultraviolet light propagation. The quartz flow tube (101) is used for injecting humid synthetic air; a through hole is formed around a position above the ultraviolet light path in the quartz flow tube (101) for a capillary dispensing needle (122) to extend into the quartz flow tube (101), the capillary dispensing needle (122) is used for injecting propane gas into the quartz flow tube (101), and the bottom of the quartz flow tube (101) is provided with a gas outlet (106) for gas outflow.

3. The high-sensitivity miniaturized HOx radical precision measurement device according to claim 1, characterized in that The gas supply module supplies the device with the following gases. Dry synthetic air is supplied into a water bottle group (4) through a first flowmeter (5) to become humid synthetic air, the humid synthetic air is mixed with dry synthetic air flowing through a second flowmeter (6) to become humid synthetic air with adjustable water vapor concentration, the humid synthetic air is mixed with carbon monoxide gas flowing out of a third flowmeter (7) to flow through a temperature and humidity sensor (29) and be injected into a blowing tube (28); the blowing tube (28) is used for blowing humid synthetic air into the quartz flow tube (101) in the radical generation and elimination device (1), and the temperature and humidity sensor (29) is used for measuring the temperature and humidity of the synthetic air injected into the blowing tube (28); First route nitrogen is injected into a communication space between the mercury lamp (103) and the photodiode (108) through a fourth flowmeter (8); Second route nitrogen is injected from a protective gas annular injection tube (3) into the periphery of the top of the sampling gas flow through a fifth flowmeter (9); Propane gas is injected into the quartz flow tube (101) through a sixth flowmeter (10); Nitric oxide gas is injected from a conversion gas annular injection tube (15) into the periphery of the middle of the sampling gas flow through a seventh flowmeter (11); The air pump (19) is connected to the air outlet (106) at the bottom of the quartz flow tube (101) through the eighth flow meter (20), so that the quartz flow tube (101) generates downward airflow.

4. The high-sensitivity miniaturized HOx radical precision measurement device according to claim 3, characterized in that The acquisition and control system comprises an ozone analyzer (18) for measuring the ozone concentration in the gas flowing out of the bottom of the quartz flow tube (101), a single-chip microcomputer (24) for controlling all electrical elements in the device and simultaneously acquiring signals of the temperature and humidity sensor (29) and the photodiode (108), and an industrial computer (12) for receiving signals of the laser energy meter (17) and the photomultiplier (1601) in the two fluorescence excitation cavities (16) and controlling and reading the single-chip microcomputer (24).

5. The high-sensitivity miniaturized HOx radical precision measurement device according to claim 1, characterized in that, The light source module comprises a laser (21) for emitting laser light for generating fluorescence of OH radicals, an optical fiber (23) for transmitting the laser light, and a coupling lens (22) for focusing and coupling the laser light into the optical fiber (23).

6. A high-sensitivity miniaturized HOx radical precision measurement method, characterized in that, The method for capturing the change trend of the concentration of OH radicals is as follows: Three measurement states are set: Measurement state one: the output wavelength of the laser (21) is locked at the fluorescence excitation peak value of OH radicals, the sixth flow meter (10) is closed to stop the injection of propane gas, during which the average value of the signal measured by the upper fluorescence excitation cavity (16) is S(OH)1, the average value of the signal measured by the lower fluorescence excitation cavity (16) is S(HO2)1, and the average value of the signal measured by the laser energy meter (17) is P1, and this state is maintained for t1 time; Measurement state two: the output wavelength of the laser (21) is locked at the fluorescence excitation peak value of OH radicals, the sixth flow meter (10) is opened to inject propane gas into the quartz flow tube (101), and the propane removes the OH radicals in the ambient atmosphere, during which the average value of the signal measured by the upper fluorescence excitation cavity (16) is S(OH)2, the average value of the signal measured by the lower fluorescence excitation cavity (16) is S(HO2)2, and the average value of the signal measured by the laser energy meter (17) is P2, and this state is maintained for t2 time; Measurement state three: the output wavelength of the laser (21) is adjusted to be far away from the fluorescence excitation peak of OH radicals, and the sixth flow meter (10) is closed to stop the injection of propane gas, at this time, the laser does not intersect with OH radicals to generate fluorescence, during which the average value of the signal measured by the upper fluorescence excitation cavity (16) is S(OH)3, the average value of the signal measured by the lower fluorescence excitation cavity (16) is S(HO2)3, and the average value of the signal measured by the laser energy meter (17) is P3, and this state is maintained for t3 time; In actual measurement, the three measurement states are switched in sequence, and in the three measurement states, the position of the movable grating plate (115) is adjusted so that the intensity of the purple light detected by the photodiode (108) is zero, that is, the ultraviolet light emitted by the mercury lamp (103) is completely blocked by the movable grating plate (115) and the fixed grating plate (117); The method for capturing the change trend of the concentration of OH radicals is as follows: First, in the measurement state one, the ambient atmosphere is drawn into the quartz flow tube (101), and then is drawn into the upper and lower two fluorescence excitation cavities (16) by the sampling nozzle (2), at this time, the signal S(OH)1 measured by the upper fluorescence excitation cavity (16) is the sum of the OH real fluorescence signal, the OH interference signal and the background signal of the upper fluorescence excitation cavity (16), and the average value of the signal measured by the laser energy meter (17) during this period is P1; Then, in the measurement state two, the propane is drawn into the quartz flow tube (101) to remove the OH free radicals, at this time, the signal S(OH)2 measured by the upper fluorescence excitation cavity (16) is the sum of the OH interference signal and the background signal of the upper fluorescence excitation cavity (16), and the average value of the signal measured by the laser energy meter (17) during this period is P2; Finally, in the measurement state three, the laser does not produce fluorescence with the OH free radicals, at this time, the signal S(OH)3 measured by the upper fluorescence excitation cavity (16) is the background signal of the upper fluorescence excitation cavity (16), and the average value of the signal measured by the laser energy meter (17) during this period is P3; The changing trend is the trend of the actual concentration of atmospheric OH free radicals. The changing trend is the changing trend of the OH interference signal; The method for capturing the change trend of the HO2 free radical concentration is as follows: First, in the measurement state one, the ambient atmosphere is drawn into the quartz flow tube (101), and then is drawn into the upper and lower two fluorescence excitation cavities (16) by the sampling nozzle (2), at this time, the atmospheric HO2 free radicals are partially converted into OH free radicals between the upper and lower two fluorescence excitation cavities (16), at this time, the signal S(HO2)1 measured by the lower fluorescence excitation cavity (16) is the sum of the fluorescence signal of the atmospheric HO2 converted into OH, the background signal of the lower fluorescence excitation cavity (16), the OH real fluorescence signal and the OH interference signal, and the average value of the signal measured by the laser energy meter (17) during this period is P1; Then, in the second measurement state, the propane is pumped into the quartz flow tube (101) to scavenge the OH radicals, and the signal S(HO2)2 measured by the lower fluorescence excitation chamber (16) is the atmospheric HO 2转化的 the sum of the fluorescence signal of OH, the background signal of the lower fluorescence excitation chamber (16), and the interference signal of OH, and the average value of the signal measured by the laser energy meter (17) is P2; Finally, in the measurement state three, the laser does not produce fluorescence with the OH free radicals, at this time, the signal S(HO2)3 measured by the lower fluorescence excitation cavity (16) is the background signal of the lower fluorescence excitation cavity (16), and the average value of the signal measured by the laser energy meter (17) during this period is P3; The variation trend of k is the variation trend of the real concentration of atmospheric HO2 free radicals.

7. A high-sensitivity miniaturized HOx radical precision measurement method, characterized in that, The high-sensitivity miniaturized HOx free radical precision measurement device of claim 3 is used to lock the peak value of the fluorescence spectrum by the photomultiplier tube (1601) itself, and the specific manner is as follows: The humid synthetic air and carbon monoxide gas injected into the blowing tube (28) are closed, and the propane gas injected into the quartz flow tube (15) is closed; The position of the moving grating plate (115) is adjusted to make the intensity of the ultraviolet light emitted by the photodiode (108) to reach the highest, at this time, the ultraviolet light photolyzes the water vapor in the ambient atmosphere, thereby generating OH free radicals; Then, the light source module starts to adjust the wavelength of the emitted laser within a certain range, at this time, the fluorescence signal detected by the photomultiplier tube (1601) of the upper fluorescence excitation cavity (16) also changes, when the scanning is completed, the wavelength of the laser emitted by the light source module is positioned at the position where the fluorescence signal is the highest.

8. A computer program product, characterised in that, It comprises computer programs / instructions which, when executed by a processor, implement the high-sensitivity miniaturized HOx radical precision measurement method of claim 6 or 7.

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