High-enthalpy flow field particle concentration measurement system and method based on two-photon laser induced fluorescence

Abstract

The invention provides a high-enthalpy flow field particle concentration measurement system and method based on two-photon laser-induced fluorescence. The system comprises a laser, a high-enthalpy flow field wind tunnel module, an imaging module, an image processing module, a reflector, a three-dimensional galvanometer, a three-axis displacement table and a collecting lens. The centers of the reflecting mirror, the three-dimensional galvanometer and the collecting lens are coaxial and located on the same light path plane, and the three-dimensional galvanometer and the collecting lens are both fixedly installed on the three-axis displacement table; the laser device generates a laser beam, the laser beam is irradiated to the three-dimensional galvanometer through the reflecting mirror, the direction of the laser beam is changed by deflecting the three-dimensional galvanometer and / or moving the three-axis displacement table, and then the laser beam with the changed direction is irradiated to particles to be measured in a flow field area to be measured through the collecting mirror to generate fluorescent light; the imaging module collects fluorescence generated by irradiation of the laser beams to obtain fluorescence data; and the image processing module is used for processing the fluorescence data to obtain a three-dimensional image of the to-be-detected particle. According to the scheme, three-dimensional scanning measurement of the high-enthalpy flow field without a sheet light source is realized, the measurement precision is improved, and the requirement on the energy of the laser is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of non-contact flow field measurement, and in particular to a high-enthalpy flow field particle concentration measurement system and method based on two-photon laser induced fluorescence. Background Art

[0002] High enthalpy flow fields are mainly formed in high-speed flowing gases. For example, when a hypersonic vehicle reenters the atmosphere, due to the extremely high speed, the friction between the gas and the vehicle surface generates a large amount of heat, which leads to an increase in gas temperature and total enthalpy value. The gas molecules are in a highly excited state, and thermochemical non-equilibrium phenomena may occur. Therefore, in high enthalpy flow field experiments, the parameters of the flow field are very important, so it is necessary to diagnose the flow field through measurement methods, such as the flow field temperature and the concentration of atoms, molecules and other components. Spectral diagnostic methods can use the characteristics of atomic and molecular characteristic energy level transitions to generate or absorb light signals, and detect light signals to invert flow field parameters. At present, high enthalpy non-equilibrium flow field spectral diagnostic technologies mainly include absorption spectroscopy (LAS), emission spectroscopy (OES) and laser induced fluorescence (LIF). Among them, two-photon laser induced fluorescence is a special type of laser induced fluorescence technology. Since it can effectively avoid the vacuum ultraviolet band, it can be used to measure O and N atoms, which have difficult transitions and need to absorb large photon energy.

[0003] At present, the research on two-photon laser induced fluorescence of high enthalpy flow fields is mostly in the form of one-dimensional measurement, that is, a laser beam is used to irradiate the flow field and receive the fluorescence signal emitted by the irradiated particles. However, this method cannot obtain parameters such as the particle concentration of the entire flow field in real time. Although the use of a sheet light source for two-dimensional measurement can obtain more parameters of the flow field, since two-photon absorption is a third-order nonlinear effect, a higher laser intensity is required. In the process of shaping the laser beam into a sheet light source, the beam energy will be dispersed, the light intensity will be reduced, and the degree of two-photon absorption will be reduced, thereby affecting the observation of the fluorescence signal. Therefore, a higher power laser is required, which increases the cost of measurement. Therefore, a high-enthalpy flow field particle concentration measurement system and method based on two-photon laser induced fluorescence is needed. Summary of the invention

[0004] The present invention provides a high-enthalpy flow field particle concentration measurement system and method based on two-photon laser induced fluorescence, which realizes three-dimensional scanning measurement of high-enthalpy flow fields without the need for a sheet light source, thereby not only improving the particle concentration measurement accuracy, but also reducing the requirement for laser energy.

[0005] In a first aspect, the present invention provides a high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence, comprising: a laser, a three-dimensional scanning module, a high enthalpy flow field wind tunnel module, an imaging module and an image processing module; the three-dimensional scanning module comprises a reflector, a three-dimensional galvanometer, a three-axis translation stage and a condenser;

[0006] The centers of the reflector, the three-dimensional galvanometer and the condenser are coaxial and located on the same optical path plane, and the three-dimensional galvanometer and the condenser are fixedly mounted on the three-axis translation stage; during measurement, the focus of the condenser is located at the flow field to be measured area of ​​the high enthalpy flow field wind tunnel module that generates a high enthalpy flow field;

[0007] The laser beam generated by the laser is irradiated onto the three-dimensional galvanometer through the reflector, and the direction of the laser beam is changed by deflecting the three-dimensional galvanometer and / or moving the three-axis translation stage. Then, the laser beam with changed direction is irradiated onto the particles to be measured in the flow field to be measured area through the condenser to generate fluorescence; the imaging module collects the fluorescence generated by the laser beam irradiation to obtain fluorescence data; the image processing module obtains a three-dimensional image of the particles to be measured by processing the fluorescence data.

[0008] Preferably, the laser comprises: a pump laser and a dye laser; the laser light emitted by the pump laser passes through the dye laser to generate the laser beam; the laser beam is used to cause the particle to undergo energy level transition to generate fluorescence.

[0009] Preferably, the high enthalpy flow field wind tunnel module is a high-frequency plasma wind tunnel.

[0010] Preferably, the reflectivity of the reflector is greater than 90%.

[0011] Preferably, the three-dimensional scanning module further includes: an aperture diaphragm and a galvanometer control module; the aperture diaphragm is arranged between the reflector and the three-dimensional galvanometer; the galvanometer control module is used to deflect the three-dimensional galvanometer and move the three-axis translation stage.

[0012] Preferably, the imaging module comprises an ICCD camera, a cutoff filter, and a synchronization trigger; the synchronization trigger is used to control the laser and the ICCD camera to start synchronously; and the cutoff filter is installed on the ICCD camera.

[0013] Preferably, the high enthalpy flow field wind tunnel module is provided with an incident window and an observation window; the laser beam enters the flow field to be measured area through the incident window; and the imaging module acquires the fluorescence data through the observation window.

[0014] In a second aspect, the present invention further provides a method for measuring the concentration of particles in a high enthalpy flow field based on two-photon laser induced fluorescence, which is implemented by using any one of the high enthalpy flow field particle concentration measurement systems based on two-photon laser induced fluorescence of the first aspect above, and the method comprises:

[0015] Determining the wavelength of the laser beam according to the particles to be measured in the high enthalpy flow field;

[0016] determining a target laser according to the wavelength;

[0017] Determining the adjustment parameters of the three-dimensional scanning module according to the flow field to be measured area; wherein the adjustment parameters include the position and angle of the reflector, the deflection range of the three-dimensional galvanometer and the movement range of the three-axis translation stage;

[0018] Setting a scanning path of the three-dimensional scanning module according to the adjustment parameters;

[0019] The imaging module collects fluorescence data when the three-dimensional scanning module moves along the scanning path, and processes the fluorescence data based on the image processing module to obtain a three-dimensional image of the particle to be detected.

[0020] Preferably, determining the adjustment parameters of the three-dimensional scanning module according to the flow field to be measured area includes:

[0021] For any position point in the flow field to be measured area, execute:

[0022] According to the focal length of the condenser, the positional relationship between the condenser and the flow field test interval and the three-dimensional coordinates of the position point, the positions of the reflector, the three-dimensional galvanometer and the three-axis translation stage are adjusted, and the adjustment parameters for the position point are determined so that the focus of the condenser is located at the position point; wherein the three-dimensional coordinates of different position points are different.

[0023] Preferably, setting the scanning path of the three-dimensional scanning module according to the adjustment parameters includes:

[0024] After determining the adjustment parameters at any position point in the flow field to be measured area, the position points are scanned in sequence from left to right and from front to back according to the three-dimensional coordinates of the position points to determine the scanning path including the adjustment parameter sequence of each position point.

[0025] Preferably, after obtaining the three-dimensional image of the particles to be detected, the method further includes: calculating the concentration of the particles to be detected according to the particles to be detected included in the three-dimensional image.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] The present invention provides a high-enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence. Through a three-dimensional galvanometer and a three-axis displacement platform, a three-dimensional in-situ measurement of a high-enthalpy flow field without sheet light is achieved, which reduces the requirements for the laser and improves the system life. By controlling the movement of the light beam through a three-dimensional galvanometer and a high-precision displacement platform, the problem of rapid reduction of the light beam intensity caused by laser beam shaping can be effectively avoided, which not only realizes fast and large-range three-dimensional scanning measurement and improves the measurement accuracy, but also breaks through the problem of limited scanning range of the galvanometer through the coordinated movement of the three-dimensional galvanometer and the three-axis displacement platform, and at the same time reduces the requirements for laser energy without the need for a sheet light source.

[0028] In the present invention, since lasers at different positions can be controlled only by a three-dimensional galvanometer and a three-axis displacement platform, the consistency of the beam is very high, avoiding the measurement error caused by the uneven shaping of the light beam of the sheet light source. At the same time, the use of a high-precision three-axis displacement platform avoids the sector error caused by large-range movement controlled only by the galvanometer, thereby improving the measurement accuracy of the particle concentration in the high enthalpy flow field.

[0029] In the present invention, the focal position of the light beam is controlled by a three-dimensional galvanometer. Combined with laser power regulation and a condenser, the threshold effect of two-photon absorption can be utilized to control the area emitting fluorescence to an extremely small point, and the fluorescence signal is collected by time accumulation, thereby achieving high spatial resolution measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 is a schematic diagram of a high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence provided by an embodiment of the present invention;

[0032] Figure 2 is a schematic diagram of another high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence provided by an embodiment of the present invention;

[0033] Figure 3 It is a flow chart of a method for measuring particle concentration in a high enthalpy flow field based on two-photon laser induced fluorescence provided by one embodiment of the present invention;

[0034] Figure numerals: 10 - laser; 20 - three-dimensional scanning module; 30 - high enthalpy flow field wind tunnel module; 40 - imaging module; 50 - image processing module; 101 - pump laser; 102 - dye laser; 201 - reflector; 202 - three-dimensional galvanometer; 203 - three-axis translation stage; 204 - condenser; 301 - incident window; 302 - observation window; 401 - ICCD camera; 402 - cutoff filter; 403 - synchronization trigger. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] Please refer to Figure 1 and Figure 2 The embodiment of the present invention provides a high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence, comprising: a laser 10, a three-dimensional scanning module 20, a high enthalpy flow field wind tunnel module 30, an imaging module 40 and an image processing module 50; the three-dimensional scanning module 20 comprises a reflector 201, a three-dimensional galvanometer 202, a three-axis translation stage 203 and a condenser 204;

[0037] The centers of the reflector 201, the three-dimensional galvanometer 202 and the condenser 204 are coaxial and located on the same optical path plane, and the three-dimensional galvanometer 202 and the condenser 204 are fixedly mounted on the three-axis translation stage 203; during measurement, the focus of the condenser 204 is located at the flow field to be measured area of ​​the high enthalpy flow field wind tunnel module 30 that generates the high enthalpy flow field;

[0038] The laser beam generated by the laser 10 is irradiated to the three-dimensional galvanometer 202 through the reflector 201. The direction of the laser beam is changed by deflecting the three-dimensional galvanometer 202 and / or moving the three-axis translation stage 203. Then, the laser beam with changed direction is irradiated to the particles to be tested in the test area of ​​the flow field through the condenser 204 to generate fluorescence; the imaging module 40 collects the fluorescence generated by the laser beam irradiation to obtain fluorescence data; the image processing module 50 obtains a three-dimensional image of the particles to be tested by processing the fluorescence data.

[0039] It should be noted that the three-dimensional galvanometer is fixedly mounted on the three-axis translation stage but can be deflected. The condenser can be a set of lens groups.

[0040] In the embodiment of the present invention, a three-dimensional scanning module including a three-dimensional galvanometer, a three-axis translation platform, a reflector, and a condenser is used to realize three-dimensional in-situ measurement of high-enthalpy flow fields without sheet light, thereby reducing the requirements for lasers and improving the life of the system. By controlling the movement of the light beam through a three-dimensional galvanometer and a high-precision displacement platform, the problem of rapid reduction in beam intensity caused by laser beam shaping can be effectively avoided, which not only realizes fast and large-scale three-dimensional scanning measurement and improves measurement accuracy, but also drives the coordinated movement of the three-axis translation platform to break through the problem of limited scanning range of the three-dimensional galvanometer, while reducing the requirements for laser energy without the need for a sheet light source.

[0041] In the present invention, in order to achieve three-dimensional in-situ high-precision measurement of the concentration of particles such as oxygen and nitrogen atoms in a high-enthalpy flow field, a three-dimensional galvanometer and a three-axis high-precision displacement platform are combined to achieve three-dimensional scanning of the laser in the high-enthalpy flow field, thereby avoiding the energy loss of the laser in the airspace. The fluorescence signal of the flow field to be measured is obtained by three-dimensional scanning, and after image calibration and processing, three-dimensional reconstruction is performed, thereby completing the in-situ measurement of the flow field in a short time.

[0042] In the embodiment of the present invention, a three-dimensional galvanometer is used to realize the rapid movement of the light beam in a smaller range, and a high-precision three-axis translation stage is used to realize the movement of the light beam in a larger range. The two cooperate with each other to realize the entire process of three-dimensional scanning.

[0043] In the embodiment of the present invention, the energy of the laser beam is strongest at the focus of the condenser, so double absorption is more likely to occur. Therefore, placing the focus at the flow field to be measured can achieve high-resolution measurement at the focus.

[0044] In a preferred embodiment, the laser 10 includes: a pump laser 101 and a dye laser 102; the laser light emitted by the pump laser 101 generates a laser beam after passing through the dye laser 102; the laser beam is used to cause the particle to undergo energy level transition to generate fluorescence.

[0045] In the embodiment of the present invention, the laser uses a nanosecond laser with high beam quality, and the nanosecond laser includes a group of pump lasers and dye lasers. Different excitation lasers can be obtained by changing the wavelength of the pump laser and the type of dye, so that the measurement system is suitable for measuring the concentration of multiple particles. It should be noted that different particles require different energies for energy level transitions, so the required excitation lasers are also different.

[0046] In a preferred embodiment, the high enthalpy flow field wind tunnel module 30 is a high frequency plasma wind tunnel.

[0047] In the embodiment of the present invention, the flow field of the high-frequency plasma wind tunnel is relatively pure and stable, and the laser scattering absorption attenuation is small. Moreover, the flow field enthalpy value is high, and the concentration of particles such as oxygen atoms and nitrogen atoms has a significant relationship with the state of the wind tunnel.

[0048] In a preferred embodiment, the reflectivity of the reflector 201 is greater than 90%.

[0049] In the embodiment of the present invention, selecting a reflector with a reflectivity greater than 90% can reduce the loss of the light beam during the reflection process, while ensuring the precise guidance and transmission of the laser beam, so as to ensure the accuracy of the measurement result and achieve high-precision measurement. For example, the reflectivity of the reflector can be 91%, 92%, 93%, 94%, 95%, 96%, 99%, etc.

[0050] In a preferred embodiment, the three-dimensional scanning module 30 also includes: an aperture diaphragm and a galvanometer control module; the aperture diaphragm is arranged between the reflector 201 and the three-dimensional galvanometer 202; the galvanometer control module is used to deflect the three-dimensional galvanometer 201 and move the three-axis translation stage 203.

[0051] In the embodiment of the present invention, the aperture stop improves the imaging quality and reduces aberration and distortion by limiting the light that deviates from the ideal position, while effectively intercepting stray light and improving the imaging clarity and contrast.

[0052] It should be noted that Figure 1 The aperture stop and galvanometer control module are not shown.

[0053] In a preferred embodiment, the imaging module 40 includes an ICCD camera 401 , a cutoff filter 402 , and a synchronization trigger 403 ; the synchronization trigger 403 is used to control the laser 10 and the ICCD camera 401 to start synchronously; and the cutoff filter 402 is installed on the ICCD camera 401 .

[0054] In an embodiment of the present invention, the imaging module includes an ICCD camera with high sensitivity, high resolution, low noise and fast frame rate, a cutoff filter, and a synchronization trigger. The cutoff filter can be used to filter out stray light and improve the imaging quality. The collection of fluorescence signals in the required band can be achieved by replacing the cutoff filter. Since the laser used in the present invention is a pulsed laser tube, in order to ensure that the imaging module and the laser are turned on at the same time, imaging can be performed in time after the laser is emitted, a synchronization trigger is used. The delay between laser emission and imaging is avoided by using a synchronization trigger.

[0055] In a preferred embodiment, the high enthalpy flow field wind tunnel module 30 is provided with an incident window 301 and an observation window 302 ; the laser beam enters the flow field to be measured area through the incident window 301 ; and the imaging module 40 acquires fluorescence data through the observation window 302 .

[0056] It should be noted that the image processing module includes but is not limited to a computer with image processing function. The image processing module is used to obtain an imaging image based on the fluorescence data, correct the imaging image to obtain a three-dimensional image, and analyze the three-dimensional image to obtain the concentration field of the particles to be measured.

[0057] like Figure 3 As shown, the present invention also provides a high enthalpy flow field particle concentration measurement method based on two-photon laser induced fluorescence based on any of the above-mentioned high enthalpy flow field particle concentration measurement systems based on two-photon laser induced fluorescence, the method comprising:

[0058] Step S0, determining the wavelength of the laser beam according to the particles to be measured in the high enthalpy flow field;

[0059] Step S2, determining the target laser according to the wavelength;

[0060] Step S4, determining the adjustment parameters of the three-dimensional scanning module according to the flow field to be measured area; wherein the adjustment parameters include the position and angle of the reflector, the deflection range of the three-dimensional galvanometer and the movement range of the three-axis translation stage;

[0061] Step S6, setting the scanning path of the three-dimensional scanning module according to the adjustment parameters;

[0062] Step S8, the imaging module collects the fluorescence data when the three-dimensional scanning module moves along the scanning path, and processes the fluorescence data based on the image processing module to obtain a three-dimensional image of the particle to be measured.

[0063] In an embodiment of the present invention, since different particles to be measured require different excitation energies, it is necessary to determine the wavelength of the laser beam according to the particles to be measured, and further determine the laser that can emit the laser beam of this wavelength, and then determine the adjustment parameters of the three-dimensional scanning module based on the flow field to be measured area, so as to determine the specific scanning path, realize the scanning of any point in the flow field to be measured area, realize comprehensive three-dimensional in-situ scanning, and obtain more comprehensive fluorescence data, and obtain a three-dimensional image of the particles to be measured in the high enthalpy flow field.

[0064] In a preferred embodiment, after obtaining the three-dimensional image of the particles to be detected in step S8, the method further includes: calculating the concentration of the particles to be detected according to the particles to be detected included in the three-dimensional image.

[0065] In the embodiment of the present invention, the three-dimensional image includes the distribution of the particles to be measured in the high enthalpy flow field, so the concentration of the particles to be measured in the high enthalpy flow field can be calculated by counting the number of particles to be measured in a certain area.

[0066] In a preferred embodiment, step S4 determines the adjustment parameters of the three-dimensional scanning module according to the flow field to be measured area, including:

[0067] For any position point in the flow field to be measured, execute:

[0068] According to the focal length of the condenser, the positional relationship between the condenser and the flow field test area and the three-dimensional coordinates of the position point, the positions of the reflector, the three-dimensional galvanometer and the three-axis translation stage are adjusted to determine the adjustment parameters for the position point so that the focus of the condenser is located at the position point; wherein the three-dimensional coordinates of different position points are different.

[0069] In the embodiment of the present invention, in order to realize the three-dimensional in-situ scanning of the high enthalpy flow field in the flow field to be measured, it is necessary to scan any position point in the flow field to be measured, that is, any point in the three-dimensional space that the laser beam can illuminate through the incident window needs to obtain its fluorescence signal. At the same time, by adjusting the adjustment parameters of the three-dimensional scanning module so that the focus of the condenser is located at any position point, the fluorescence signal intensity of each position point is further improved, thereby improving the measurement accuracy of the concentration of the particles to be measured.

[0070] In a preferred embodiment, step S6 sets the scanning path of the three-dimensional scanning module according to the adjustment parameters, including:

[0071] After determining the adjustment parameters at any position point in the flow field test area, the position points are scanned in sequence from left to right and from front to back according to the three-dimensional coordinates of the position points to determine a scanning path including the adjustment parameter sequence of each position point.

[0072] In an embodiment of the present invention, the scanning path is determined based on the adjustment parameters of each position point in the order of its three-dimensional coordinates from left to right and from front to back, so that the three-dimensional scanning module can be adjusted in an orderly manner, making the adjustment more convenient and efficient, and avoiding missed scans or repeated scanning of the same position point to affect the accuracy of the measurement results.

[0073] In a specific embodiment, using Figure 1 The high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence is shown to measure the oxygen atom concentration in the high enthalpy flow field. The measurement steps are as follows:

[0074] (1) Installation stage: Select a pump laser 101 and a dye laser 102 that can emit a 225 nm laser beam; use a 225 nm reflector 201 with a mounting angle of 45 degrees and a reflectivity of 95%; use a 225 nm high transmittance lens for the incident window 301;

[0075] The pump laser 101, the dye laser 102, the reflector 201, the three-dimensional galvanometer 202, the three-axis translation stage 203, the condenser 204 (i.e. Figure 1The focusing system in the high enthalpy flow field wind tunnel module 30, ICCD camera 401, cutoff filter 402, synchronization trigger 403 and image processing module 50 are constructed to obtain a high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence. Among them, the centers of the reflector 201, the three-dimensional galvanometer 202 and the condenser 204 are coaxial and located on the same optical path plane, and the three-dimensional galvanometer 202 and the condenser 204 are fixedly mounted on the three-axis translation stage 203; the high enthalpy flow field wind tunnel module 30 is provided with an incident window 301 and an observation window 302; the synchronization trigger 403 is used to control the laser 10 and the ICCD camera 401 to start synchronously; the cutoff filter 402 is installed on the ICCD camera 401;

[0076] (2) Debugging stage: During measurement, preparation work is first performed, the high enthalpy flow field wind tunnel module 30 is turned on, and then the laser and imaging module are synchronously turned on based on the synchronization trigger 403, and then the laser wavelength is fine-tuned and the ICCD camera parameters are adjusted until a clear fluorescence signal can be observed;

[0077] (3) Setting the scanning path: using the method of steps S4 and S6 above to determine the scanning path of the three-dimensional scanning module; at the same time, setting the scanning parameters and selecting the scanning rate to ensure that the scanning rate is within an appropriate range, not too fast to make the signal unable to be collected, nor too slow to make the collected signal lose timeliness;

[0078] (4) Measurement stage: The laser emitted by the pump laser 101 generates a laser beam after passing through the dye laser 102; the laser beam is irradiated to the three-dimensional galvanometer 202 through the reflector 201, and the three-dimensional galvanometer 202 is deflected and / or the three-axis displacement stage 203 is moved according to the scanning path to change the direction of the laser beam, and the optical path is adjusted so that the horizontal incident height of the laser is consistent with the center height of the flow field to be measured area; then the laser beam with changed direction passes through the condenser 204 and the incident window 301 to irradiate the particle to be measured to generate fluorescence; the ICCD camera 401 collects the fluorescence signal generated by the laser beam irradiation through the observation window 302 after filtering by the cutoff filter 402 to obtain fluorescence data; the image processing module 50 processes the fluorescence data to obtain a three-dimensional image of the particle to be measured, and analyzes and calculates the three-dimensional image to obtain the concentration of oxygen atoms. Among them, the focus of the condenser 204 is located in the flow field to be measured area where the high enthalpy flow field is generated.

[0079] It is to be understood that the structure illustrated in the embodiment of the present invention does not constitute a specific limitation on a high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence. In other embodiments of the present invention, a high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence may include more or fewer components than shown in the figure, or combine some components, or split some components, or arrange the components differently.

[0080] It should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical factors in the process, method, article or device including the elements.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence, characterized in that: include: Laser, three-dimensional scanning module, high enthalpy flow field wind tunnel module, imaging module and image processing module; the three-dimensional scanning module includes a reflector, a three-dimensional galvanometer, a three-axis translation stage and a condenser; The centers of the reflector, the three-dimensional galvanometer and the condenser are coaxial and located on the same optical path plane, and the three-dimensional galvanometer and the condenser are fixedly mounted on the three-axis translation stage; during measurement, the focus of the condenser is located at the flow field to be measured area of ​​the high enthalpy flow field wind tunnel module that generates a high enthalpy flow field; The laser beam generated by the laser is irradiated onto the three-dimensional galvanometer through the reflector, and the direction of the laser beam is changed by deflecting the three-dimensional galvanometer and / or moving the three-axis translation stage. Then, the laser beam with changed direction is irradiated onto the particles to be measured in the flow field to be measured area through the condenser to generate fluorescence; the imaging module collects the fluorescence generated by the laser beam irradiation to obtain fluorescence data; the image processing module obtains a three-dimensional image of the particles to be measured by processing the fluorescence data.

2. The high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence according to claim 1, characterized in that: The laser comprises: a pump laser and a dye laser; the laser light emitted by the pump laser generates the laser beam after passing through the dye laser; the laser beam is used to make the particle to be detected undergo energy level transition and generate fluorescence.

3. The high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence according to claim 1, characterized in that: The high enthalpy flow field wind tunnel module is a high-frequency plasma wind tunnel.

4. The high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence according to claim 1, characterized in that: The reflectivity of the reflector is greater than 90%.

5. The high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence according to claim 1, characterized in that: The three-dimensional scanning module also includes: an aperture diaphragm and a galvanometer control module; the aperture diaphragm is arranged between the reflector and the three-dimensional galvanometer; the galvanometer control module is used to deflect the three-dimensional galvanometer and move the three-axis translation stage.

6. The high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence according to claim 1, characterized in that: The imaging module comprises an ICCD camera, a cutoff filter, and a synchronization trigger; the synchronization trigger is used to control the laser and the ICCD camera to start synchronously; the cutoff filter is installed on the ICCD camera.

7. The high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence according to any one of claims 1 to 6, characterized in that: The high enthalpy flow field wind tunnel module is provided with an incident window and an observation window; the laser beam enters the flow field to be measured area through the incident window; and the imaging module acquires the fluorescence data through the observation window.

8. A measurement method for a high enthalpy flow field particle concentration measurement system based on two-photon laser induced fluorescence according to any one of claims 1 to 7, characterized in that: include: Determining the wavelength of the laser beam according to the particles to be measured in the high enthalpy flow field; determining a target laser according to the wavelength; Determining the adjustment parameters of the three-dimensional scanning module according to the flow field to be measured area; wherein the adjustment parameters include the position and angle of the reflector, the deflection range of the three-dimensional galvanometer and the movement range of the three-axis translation stage; Setting a scanning path of the three-dimensional scanning module according to the adjustment parameters; The imaging module collects fluorescence data when the three-dimensional scanning module moves along the scanning path, and processes the fluorescence data based on the image processing module to obtain a three-dimensional image of the particle to be detected.

9. The measuring method according to claim 8, characterized in that: The step of determining the adjustment parameters of the three-dimensional scanning module according to the flow field to be measured area includes: For any position point in the flow field to be measured area, execute: According to the focal length of the condenser, the positional relationship between the condenser and the flow field to be measured interval and the three-dimensional coordinates of the position point, the positions of the reflector, the three-dimensional galvanometer and the three-axis translation stage are adjusted to determine the adjustment parameters for the position point so that the focus of the condenser is located at the position point; wherein the three-dimensional coordinates of different position points are different; and / or, The step of setting the scanning path of the three-dimensional scanning module according to the adjustment parameters includes: After determining the adjustment parameters at any position point in the flow field test area, the position points are scanned in sequence from left to right and from front to back according to the three-dimensional coordinates of the position points to determine the scanning path including the order of the adjustment parameters of each position point.

10. The measuring method according to claim 8 or 9, characterized in that: After obtaining the three-dimensional image of the particles to be detected, the method further includes: calculating the concentration of the particles to be detected according to the particles to be detected included in the three-dimensional image.

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