Cloud particle turbulence synchronous measurement device and method based on digital holography and particle image velocimetry

Abstract

This invention discloses a device and method for synchronously measuring cloud particle turbulence based on digital holography and particle image velocimetry. The device includes a housing with a laser emitting arm and a laser receiving arm mounted on it, forming a sampling area between the two arms. Inside the housing are a dual-optical-path holographic measurement unit, a PIV turbulence measurement unit, and a control unit. The dual-optical-path holographic measurement unit generates two laser beams: one beam travels along its original path and exits through the laser emitting arm, while the other beam is redirected and then emitted through the same arm. The two laser beams cross each other in the sampling area and are incident on the laser receiving arm, where they are imaged onto two cameras to obtain holographic images. The PIV turbulence measurement unit generates one laser beam to form a sheet light source, which exits from the laser emitting arm and illuminates the flow field between the sampling areas, acquiring scattering images of the particles. This invention can simultaneously achieve holographic cloud particle measurement and turbulence measurement, increasing the sampling volume while also improving measurement accuracy.

Description

Technical Field

[0001] This invention relates to the field of cloud physics measurement technology, specifically to a device and method for synchronous measurement of cloud particle turbulence based on digital holography and particle image velocimetry. Background Technology

[0002] Clouds cover approximately 70% of the Earth's surface and have a significant impact on the radiation balance of the Earth-atmosphere system and the global water cycle. Many severe weather events are also closely related to clouds. Cloud turbulence has a high Reynolds number, and cloud development and evolution are influenced by turbulence at various scales. The most direct manifestation of this is the complex microphysical processes experienced by cloud particles, such as condensation, collision, growth, freezing, and frost formation. By simultaneously measuring the microscopic characteristic parameters of cloud particles, such as size, concentration, phase, velocity, and shape, as well as turbulent structural parameters, we can understand the life history of cloud particles, infer the interactions between cloud dynamics, thermodynamics, and microphysics, and thus obtain the laws governing cloud development and evolution. This can then be used for weather modification and numerical simulation forecasting.

[0003] In existing technologies, cloud particle measurement typically employs cloud particle measurement instruments. Based on measurement principles, these instruments mainly include collision sampling, optical scattering, and optical imaging types. Among these, optical scattering is the most widely used. However, optical scattering instruments require assumptions about particle shape, cannot acquire particle velocity information, and cannot directly obtain particle phase information. Digital holography, as an emerging three-dimensional particle field measurement technology, can simultaneously acquire information such as particle size, quantity, velocity, and shape. Existing holographic particle measurement instruments typically employ single-path holographic measurement, i.e., completing holographic measurement by emitting a single beam. However, this type of single-path holographic measurement has a small sampling volume, resulting in fewer cloud particle features collected in each measurement, and the accuracy of single-view reconstruction is also low.

[0004] In existing technologies, cloud turbulence measurement is usually achieved by directly probing sensors such as ultrasonic anemometers or hot-wire anemometers. To simultaneously measure cloud particles and cloud turbulence, cloud particle measurement instruments and turbulence measurement sensors need to be deployed at the same time. This is not only costly, but the sensor probes are also prone to interfering with the flow field measurement. Furthermore, particle impacts can reduce sensor sensitivity and increase measurement errors. Therefore, the accuracy of cloud turbulence measurement using sensors is not high. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a cloud particle turbulence synchronous measurement device and method based on digital holography and particle image velocimetry, which has a large sampling volume and high particle measurement accuracy. It can realize cloud particle feature measurement using a single device, obtain more cloud particle features in a larger sampling volume, and simultaneously realize the measurement of turbulence velocity field in the sampling area.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry includes a housing with a laser emitting arm and a laser receiving arm mounted on it, forming a sampling area between the laser emitting arm and the laser receiving arm. Inside the housing are a dual-optical-path holographic measurement unit, a PIV turbulence measurement unit, and a control unit for overall control. The dual-optical-path holographic measurement unit generates two laser beams. One beam travels along its original path and exits through the laser emitting arm, while the other beam is redirected and then travels back through the laser emitting arm before exiting. The two laser beams cross each other after exiting the sampling area and are incident on the laser receiving arm, where they are imaged onto a camera to obtain holographic images for cloud particle feature measurement. The PIV turbulence measurement unit generates one laser beam to form a sheet light source, which exits from the laser emitting arm and illuminates the flow field between the sampling areas. By acquiring particle scattering images, turbulence field measurement is achieved synchronously.

[0008] Furthermore, the dual-optical-path holographic measurement unit includes a first measurement optical path disposed on the laser emitting arm side and a second measurement optical path disposed on the laser receiving arm side. The first measurement optical path includes a pulsed laser, a spatial filter, a collimating lens, a beam expander, a first dichroic mirror, a beam splitter, and two outgoing transmission branches arranged in sequence. The pulsed laser emits a laser beam, which passes through the spatial filter and the collimating lens in sequence, and is then expanded by the beam expander. After the expanded laser pulse passes through the first dichroic mirror, it is split into two beams at the position of the beam splitter. The two beams are then transmitted to different exit ports of the laser emitting arm by the two outgoing transmission branches. The second measurement optical path includes two incident measurement branches for imaging the beams incident through different incident ports onto a camera.

[0009] Furthermore, one of the outgoing transmission branches includes a first reflecting mirror, a second dichroic mirror, and a first rotating prism arranged in sequence; another outgoing transmission branch includes a second reflecting mirror and a third reflecting mirror arranged in sequence; one incident measurement branch includes a fourth reflecting mirror, a first lens, and a first camera arranged in sequence; and another incident measurement branch includes a second rotating prism, a second lens, and a second camera arranged in sequence. The beam transmitted along the original optical path passes through the second dichroic mirror, is redirected at the first rotating prism, exits from the first exit port of the laser emitting arm, passes through the sampling area, enters from the first entrance port of the laser receiving arm, and is again redirected by the fourth reflecting mirror, before being imaged on the first camera by the first lens. Another beam, redirected 90° at the beam splitter, exits from the second exit port of the laser emitting arm through the first and third reflecting mirrors, passes through the sampling area, enters from the second entrance port of the laser receiving arm, and is imaged on the second camera after passing through the second rotating prism and the second lens.

[0010] Furthermore, the dual-optical-path holographic measurement unit also includes a timing controller for controlling the working timing of the first camera and the second camera according to a set exposure time sequence when a trigger signal is received. The trigger signal is generated when the pulsed laser emits a laser beam. The dual-optical-path holographic measurement unit also includes a data acquisition and storage unit for acquiring and storing the holographic images recorded by the first camera and the second camera.

[0011] Furthermore, the laser emitting arm and the laser receiving arm are arranged symmetrically along the central axis and form a wedge shape with a sharp top. The laser emitting arm and the laser receiving arm are respectively provided with two or more light-transmitting holes as exit ports and entrance ports. The laser emitting arm is provided with at least three exit ports to emit the two beams generated by the dual-optical-path holographic measurement unit and the sheet light source generated by the PIV turbulence measurement unit. The laser receiving arm is provided with at least two entrance ends to correspond to the two beams generated by the dual-optical-path holographic measurement unit. The laser receiving arm on the side opposite to the third exit port (14) of the laser emitting arm used to emit the sheet light source generated by the PIV turbulence measurement unit is provided with a high-reflectivity material coating so that the sheet light source generated by the PIV turbulence measurement unit illuminates the flow field of the sampling area.

[0012] Furthermore, the PIV turbulence measurement unit includes a continuous laser, a cylindrical mirror, and a third camera. The continuous laser emits a laser beam, which is deflected by 90° after passing through the first dichroic mirror and is transmitted coaxially with the pulsed laser beam emitted by the pulsed laser. After being deflected by the beam splitter at the position of the second dichroic mirror, it is formed into a sheet light source by the cylindrical mirror and emitted from the corresponding outlet on the laser emitting arm to illuminate the flow field of the sampling area. The laser receiving arm on the laser emitting arm, which is used to emit the sheet light source generated by the PIV turbulence measurement unit, is coated with a highly reflective material. The third camera records the scattering image of the particles in the sampling area.

[0013] Furthermore, the housing also includes a heat insulation plate, a heating unit, and a temperature and humidity monitoring unit connected to the control unit. The interior of the housing is divided into multiple areas by the heat insulation plate, and multiple temperature and humidity sensors are installed in each of the divided areas. The temperature and humidity monitoring unit monitors the temperature and / or humidity status of each divided area through the temperature and humidity sensors, and generates control signals to the control unit based on the monitored temperature and / or humidity status. Specifically, when the temperature or humidity is higher than a preset threshold, a first control signal is generated to the control unit to control the power supply to be cut off; when the temperature is lower than the preset threshold, a second control signal is generated to the control unit to control the heating unit to be turned on for heating.

[0014] Furthermore, it also includes a balancing tail fin disposed at the tail of the housing for overall auxiliary balancing during ball-borne measurement. The balancing tail fin includes a connecting rod, a secondary tail fin, and a main tail fin arranged in sequence. The main tail fin is connected to the housing through the connecting rod and is positioned directly opposite the midpoint between the laser emitting arm and the laser receiving arm. The secondary tail fins are symmetrically arranged on both sides of the main tail fin.

[0015] A measurement method utilizing the aforementioned cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry includes the following steps:

[0016] When measuring cloud particle characteristics, a laser beam is emitted by a pulsed laser. After passing through the spatial filter and collimating lens, the beam is expanded by a beam expander. The expanded laser pulse is split into two beams at the beam splitter position after passing through the first dichroic mirror. The beam that travels along the original optical path passes through the second dichroic mirror and is redirected at the first rotating prism. It exits from the first exit port of the laser emitting arm, passes through the sampling area, and enters from the first entrance port of the laser receiving arm. It is then redirected again by the fourth reflecting mirror and imaged on the first camera by the first lens to obtain a holographic image. The other beam, which is redirected 90° at the beam splitter, exits from the second exit port of the laser emitting arm after passing through the first and third reflecting mirrors. It enters from the second entrance port of the laser receiving arm after passing through the sampling area, and then imaged on the second camera by the second rotating prism and the second lens to obtain a holographic image.

[0017] During turbulence measurement, a laser beam is emitted by a continuous laser, deflected by 90° after passing through the first dichroic mirror, and transmitted coaxially with the pulsed laser beam emitted by the pulsed laser. After being deflected by the beam splitter at the position of the second dichroic mirror, it exits from the corresponding exit port on the laser emitting arm to illuminate the flow field of the sampling area. The scattering image of the particles is recorded by the third camera.

[0018] Furthermore, the cloud particle feature measurement also includes a fusion process for the holograms obtained from the dual optical paths. Specific steps include:

[0019] Establish a coordinate system, where the coordinate system corresponding to the optical path traversed by the continuous laser in the sampling area is denoted as ( x , y , z The coordinate systems of the two optical paths generated by the pulsed laser are denoted as ( ). x 1, y 1, z 1) and ( x 2, y 2, z 2);

[0020] After obtaining particle information from the holographic images recorded by the two optical paths, the particle information is uniformly transformed to the coordinate system corresponding to the continuous laser according to the following formula to obtain the final three-dimensional particle field characteristics:

[0021]

[0022] in, The angle between the two coordinate systems. , and Related to the included angle The coordinate translation coefficient.

[0023] Compared with existing technologies, the advantages of this invention mainly include: This invention forms a sampling area by setting a laser emitting arm and a laser receiving arm on a housing, and sets a dual-optical-path holographic measurement unit inside the housing. The dual-optical-path holographic measurement unit uses a dual-optical-path measurement structure to achieve dual-optical-path digital coaxial holographic measurement, which can quickly and accurately acquire holographic images of cloud particles, thereby achieving synchronous measurement of characteristics such as the size, quantity, shape, phase, and velocity of cloud particles in the sampling area. Furthermore, the dual-optical-path structure can effectively increase the sampling volume, thereby effectively increasing the acquired cloud particle features. Simultaneously, a PIV turbulence measurement unit is also set inside the housing to synchronously measure the flow field in the sampling area between the two arms, avoiding measurement interference and improving measurement accuracy. Moreover, a single device can simultaneously achieve cloud particle feature measurement and flow field measurement in the sampling area, ensuring measurement accuracy while reducing implementation costs and improving measurement flexibility, thus conveniently acquiring accurate cloud particle microphysical processes under the influence of turbulence. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry in an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the coordinates of cross-sampling region data fusion in an embodiment of the present invention.

[0026] Figure 3 This is a flowchart of the cross-sampling region data fusion method in an embodiment of the present invention.

[0027] Legend:

[0028] 1. Housing; 2. Pulsed laser; 3. Spatial filter; 4. Collimating lens; 5. Beam expander; 6. First dichroic mirror; 7. First reflecting mirror; 8. Beam splitter; 9. Second reflecting mirror; 10. Third camera; 11. Third reflecting mirror; 12. Second exit port; 13. Second dichroic mirror; 14. Third exit port; 15. First exit port; 16. First rotating prism; 17. Second rotating prism; 18. Second entrance port; 19. First lens 20. Second camera; 21. First entrance port; 22. Fourth reflector; 23. Second lens; 24. First camera; 25. Continuous laser; 26. Timing controller; 27. Control unit; 28. Data acquisition card; 29. ​​Solid state drive; 30. Signal transmission card; 31. Temperature and humidity monitoring unit; 32. Power supply unit; 33. Navigation and positioning unit; 34. Connecting rod; 35. Secondary tail fin; 36. Main tail fin; 37. Heat shield. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0030] like Figures 1-3 As shown, the cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry in this embodiment includes a housing 1, on which a laser emitting arm and a laser receiving arm are provided, and a sampling area is formed between the laser emitting arm and the laser receiving arm. Inside the housing 1, there is a dual-optical-path holographic measurement unit, a PIV (particle image velocimetry) turbulence measurement unit, and a control unit 27 for overall control. The dual-optical-path holographic measurement unit is used to generate two laser beams. One beam is transmitted along the original optical path and emitted from the laser emitting arm, while the other beam is redirected and transmitted and emitted from the laser emitting arm. After the two laser beams are emitted, they cross and are incident on the laser receiving arm through the sampling area, and are respectively imaged on a camera to obtain holographic images to realize cloud particle feature measurement. The PIV (particle image velocimetry) turbulence measurement unit is used to generate one laser beam and form a sheet light source. After being emitted from the laser emitting arm, it illuminates the flow field between the sampling areas and realizes turbulence field measurement by acquiring the scattering images of particles.

[0031] This embodiment forms a sampling area by setting a laser emitting arm and a laser receiving arm on a housing 1. A dual-optical-path holographic measurement unit is set inside the housing 1. The dual-optical-path holographic measurement unit adopts a dual-optical-path measurement structure to realize dual-optical-path digital coaxial holographic measurement, which can quickly and accurately acquire cloud particle holographic images, thereby realizing the synchronous measurement of cloud particle size, quantity, shape, phase and velocity characteristics in the sampling area. Moreover, the dual-optical-path structure can also effectively increase the sampling volume, thereby effectively increasing the acquired cloud particle features. At the same time, a PIV turbulence measurement unit is also set inside the housing 1 to simultaneously measure the flow field in the sampling area between the two arms, which can avoid measurement interference and improve measurement accuracy. Moreover, cloud particle feature measurement and flow field measurement in the sampling area can be realized simultaneously with one device. While ensuring measurement accuracy, it can also reduce implementation costs and improve measurement flexibility, thus conveniently obtaining accurate cloud particle microphysical processes under the influence of turbulence.

[0032] In this embodiment, the dual-optical-path holographic measurement unit specifically includes a first measurement optical path disposed on the laser emitting arm side and a second measurement optical path disposed on the laser receiving arm side. The first measurement optical path includes a pulsed laser 2, a spatial filter 3, a collimating lens 4, a beam expander 5, a first dichroic mirror 6, a beam splitter 8, and two outgoing transmission branches arranged in sequence. The pulsed laser 2 emits a laser beam, which passes through the spatial filter 3 and the collimating lens 4 in sequence, and is expanded by the beam expander 5. After the expanded laser pulse passes through the first dichroic mirror 6, it is split into two beams at the position of the beam splitter 8. The two beams are transmitted to different exit ports of the laser emitting arm by the two outgoing transmission branches. The second measurement optical path includes two incident measurement branches for imaging the beams incident through different incident ports onto a camera.

[0033] Preferably, the pulsed laser 2 can be a 355nm pulsed laser.

[0034] Preferably, when the beam is split at position 8, the intensity ratio of the two laser beams is 1:1, that is, they are split into two beams with the same intensity, so as to ensure that the two holographic measurement sampling beams have the same sampling capability.

[0035] In this embodiment, in the two outgoing transmission branches of the dual-optical-path holographic measurement unit, one outgoing transmission branch includes a first reflecting mirror 9, a second dichroic mirror 13, and a first rotating prism 16 arranged in sequence; the other outgoing transmission branch includes a second reflecting mirror 7 and a third reflecting mirror 11 arranged in sequence. One incident measurement branch includes a fourth reflecting mirror 22, a first lens 23, and a first camera 24 arranged in sequence; the other incident measurement branch includes a second rotating prism 17, a second lens 19, and a second camera 20 arranged in sequence. The light beam transmitted along the original optical path passes through the second dichroic mirror 13. Then, the beam is redirected at the first rotating prism 16 and exits from the first exit port 15 of the laser emitting arm. After passing through the sampling area, it enters from the first entrance port 21 of the laser receiving arm and is redirected again by the fourth reflecting mirror 22. It is then imaged on the first camera 24 by the first lens 23. The other beam, after being redirected 90° at the beam splitter 8, exits from the second exit port 12 of the laser emitting arm through the first reflecting mirror 7 and the third reflecting mirror 11. After passing through the sampling area, it enters from the second entrance port 18 of the laser receiving arm and is imaged on the second camera 20 after passing through the second rotating prism 17 and the second lens 19.

[0036] Preferably, both the first camera 24 and the second camera 20 can be CCD cameras. Both the first lens 23 and the second lens 19 can be telecentric lenses.

[0037] In this embodiment, the dual-optical-path holographic measurement unit further includes a timing controller 26, which controls the working timing of the first camera 24 and the second camera 20 according to the set exposure time sequence when a trigger signal is received. The trigger signal is generated when the pulsed laser 2 emits a laser beam, that is, when the pulsed laser 2 emits a laser beam, it outputs a trigger signal to the timing controller 26, and controls the first camera 20 and the second camera 24 to work according to the set exposure time sequence.

[0038] In this embodiment, the dual-optical-path holographic measurement unit further includes a data acquisition and storage unit for acquiring and storing holographic images recorded by the first camera 24 and the second camera 20. The data acquisition and storage unit specifically includes a data acquisition card 28, a signal transmission card 30, and a solid-state drive 29. The holograms recorded by the first camera 24 and the second camera 20 are transmitted to the data acquisition card 28, and after image conversion and compression, are stored in the solid-state drive 29. Based on the recorded holographic images, characteristic information such as particle size, shape, and velocity can be obtained.

[0039] In this embodiment, a fixing plate is also provided inside the housing 1 for fixing the components. The housing 1 and the internal fixing plate can form an effective protective structure. Furthermore, the tip of the housing 1 can be formed into a wedge shape with a sharp top. The housing 1 and the measuring arms are integrally cast and divided into upper and lower halves. The fixing plate is fixed to the lower half of the device housing 1 with a threaded nut. The fixing plate has engineering threaded holes for fixing other accessories of the device.

[0040] Preferably, the laser emitting arm and the laser receiving arm are arranged symmetrically along the central axis. The laser emitting arm and the laser receiving arm are each provided with two or more light-transmitting holes (optical windows) to serve as the emission port and the inlet port, respectively. The laser emitting arm is provided with at least three emission ports to emit two beams generated by the dual-optical-path holographic measurement unit and a sheet light source generated by the PIV turbulence measurement unit, respectively. The first emission port 15 and the second emission port 12 correspond to the emission of the two beams generated by the dual-optical-path holographic measurement unit, respectively. The third emission port 14 corresponds to the emission of the sheet light source generated by the PIV turbulence measurement unit. The laser receiving arm is provided with at least two incident ends (the first incident end 21 and the second incident end 18) to correspond to the incident of the two beams generated by the dual-optical-path holographic measurement unit, respectively. A high-reflectivity material coating is provided on the laser receiving arm on the side of the third emission port 14 on the laser emitting arm so that the sheet light source generated by the PIV turbulence measurement unit illuminates the flow field of the sampling area.

[0041] Preferably, all optical windows on the laser emitting arm and laser receiving arm are sealed with sapphire crystal to reduce the influence of stray light and minimize water vapor condensation. Furthermore, some or all of the optical windows are equipped with heating resistance wires. During measurement, the resistance wires around the optical windows are activated at specified intervals to heat the optical windows for a specified duration, preventing water vapor condensation or frost formation.

[0042] In this embodiment, the PIV turbulence measurement unit specifically includes a continuous laser 25, a cylindrical mirror, and a third camera 10. The continuous laser 25 emits a laser beam, which is deflected by 90° after passing through the first dichroic mirror 6 and is transmitted coaxially with the pulsed laser beam emitted by the pulsed laser 2. After being deflected at the position of the second dichroic mirror 13 by the beam splitter 8, it passes through the cylindrical mirror to form a sheet light source, which is emitted from the corresponding outlet on the laser emitting arm. The sheet light source is coated with a high reflectivity material on the laser receiving arm so that it illuminates the flow field of the sampling area. The third camera 10 records the scattering image of the particles.

[0043] Preferably, in this embodiment, the continuous laser 25 is a 532nm continuous laser, and the third camera 10 can be a high-speed camera.

[0044] Optionally, in addition to the above-mentioned coaxial transmission structure for holographic measurement and turbulence measurement, other methods of holographic measurement and turbulence measurement can also be used. For example, the pulsed laser 2 used in holographic measurement is a 532nm pulsed laser. The holographic measurement optical path and the PIV turbulence measurement optical path are not coaxially transmitted, but are transmitted at a certain height difference. The holographic 532nm laser beam transmission path is below, and the PIV turbulence 532nm laser beam is above.

[0045] In this embodiment, the housing 1 also includes a heat insulation plate 37, a heating unit, and a temperature and humidity monitoring unit connected to the control unit 27. The interior of the housing 1 is divided into multiple areas by the heat insulation plate 37, and multiple temperature and humidity sensors are installed in each of the divided areas. The temperature and humidity monitoring unit 31 monitors the temperature and / or humidity status of each divided area through the temperature and humidity sensors, and generates control signals to the control unit 27 based on the monitored temperature and / or humidity status. Specifically, when the temperature or humidity is higher than a preset first threshold, a first control signal is generated to the control unit 27 to control the power supply to be cut off; when the temperature is lower than a second preset threshold, a second control signal is generated to the microcomputer control unit 27 to control the heating unit to be turned on for heating. The temperature and humidity monitoring unit 31 can specifically be a temperature control chip. The heating unit can specifically be a thermal resistance wire, etc.

[0046] Specifically, the pulsed laser 2, the second camera 24, and the image recording and acquisition device 10 are divided into separate areas by the heat insulation plate 37, and temperature and humidity sensors are installed in each area. When the pulsed laser 2 and the continuous laser 25 are working, the temperature and humidity monitoring unit 31 controls the device according to the values ​​displayed by the internal temperature and humidity sensors. When the internal temperature is higher than the first preset threshold, the temperature and humidity monitoring unit 31 outputs a signal to the control unit 27, the control unit 27 cuts off the power supply, and the pulsed laser 2, the continuous laser 25, the first camera 24, and the second camera 20 stop working. When the internal temperature is lower than the second preset threshold, the temperature and humidity monitoring unit 31 outputs a signal to the control unit 27, the control unit 27 turns on the heating wire to heat the inside of the device. When the internal humidity is higher than the third preset threshold, it indicates that there may be water vapor leakage. The temperature and humidity monitoring unit 31 outputs a signal to the control unit 27, the control unit 27 cuts off the power supply, the pulsed laser 2, the continuous laser 25, the first camera 24, and the second camera 20 stop working, and the control unit 27 controls the signal transmitting card 30 to send a warning signal to the ground to protect the internal optics. Preferably, the first preset threshold can be set to 40°, the second preset threshold can be set to 10°, and the third preset threshold can be set to 75%, which can be configured according to actual needs.

[0047] In this embodiment, a balancing tail fin is also included at the tail of the housing 1 for overall balancing during ball-borne measurements. The balancing tail fin includes a connecting rod 34, a secondary tail fin 35, and a main tail fin 36 arranged sequentially. The main tail fin 36 is connected to the housing 1 via the connecting rod 34 and faces the midpoint between the laser emitting arm and the laser receiving arm. The secondary tail fins 35 are symmetrically arranged on both sides of the main tail fin 36. By setting up the tail fin balancing mechanism, stable measurements of the instrument can be achieved during ball-borne launch and detection.

[0048] Furthermore, in this embodiment, the housing 1 is also provided with a lithium battery as a power supply unit 32 for powering the operation of all devices in the device, and a navigation and positioning unit 33 for the device navigation and positioning.

[0049] This invention utilizes the above-mentioned method for synchronous measurement of cloud particle turbulence based on digital holography and particle image velocimetry, and includes the following steps:

[0050] When measuring cloud particle characteristics, a laser beam is emitted by a pulsed laser 2, passes through a spatial filter 3 and a collimating lens 4, and is then expanded by a beam expander 5. The expanded laser pulse passes through a first dichroic mirror 6 and is split into two beams at a beam splitter 8. The beam that travels along the original optical path passes through a second dichroic mirror 13 and is redirected at a first rotating prism 16. It exits from the first exit port of the laser emitting arm, passes through a sampling area, and enters from the first entrance port of the laser receiving arm. It is then redirected again by a fourth reflecting mirror 22 and imaged on a first camera 24 by a first lens 23 to obtain a holographic image. The other beam, which is redirected 90° at the beam splitter 8, exits from the second exit port of the laser emitting arm through a first reflecting mirror 7 and a third reflecting mirror 11. It passes through a sampling area and enters from the second entrance port of the laser receiving arm. It then passes through a second rotating prism 17 and a second lens 19 and imaged on a second camera 20 to obtain a holographic image.

[0051] During turbulence measurement, a laser beam is emitted by a continuous laser 25, deflected by 90° after passing through the first dichroic mirror 6, and transmitted coaxially with the pulsed laser beam emitted by the pulsed laser 2. After being deflected at the position of the second dichroic mirror 13 by the beam splitter 8, it is emitted from the corresponding exit port on the laser emitting arm to illuminate the flow field of the sampling area. The scattering image of the particles is recorded by the third camera 10.

[0052] like Figure 2 , 3 As shown, this embodiment also includes a step of fusing the holograms obtained from the dual optical paths when measuring cloud particle features. The specific steps include:

[0053] Establish a coordinate system, such as Figure 3 As shown, the coordinate system corresponding to the optical path traversed by the continuous laser 25 in the sampling area is denoted as ( x , y , z The coordinate systems of the two optical paths generated by pulsed laser 2 are denoted as ( x 1, y 1, z 1) and ( x 2, y 2, z 2);

[0054] After obtaining particle information from the holographic images recorded by the two optical paths, the particle information is uniformly transformed to the coordinate system corresponding to the continuous laser 25 according to the following formula to obtain the final three-dimensional particle field characteristics:

[0055] (1)

[0056] in, The angle between the two coordinate systems. , and Related to the included angle The coordinate translation coefficient. Once the optical path is fixed... , , and These are all constants, which can be obtained through experimental measurement.

[0057] In this embodiment, particle information is first obtained from the first optical path holographic image and the second optical path holographic image, respectively. The particle information obtained from the first optical path holographic image and the second optical path holographic image is then transformed according to equation (1) and matched with the particle information of the first optical path holographic image. Alternatively, the second optical path holographic image can be transformed to be consistent with the first optical path holographic image before particle matching is performed (e.g., ...). Figure 2 As shown in the figure, the three-dimensional particle field characteristics are finally obtained. Using the measurement results from the dual-path intersection region, the measurement accuracy of the particle characteristics can be further improved through data fusion.

[0058] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry, characterized in that, The system includes a housing (1), on which a laser emitting arm and a laser receiving arm are provided, forming a sampling area between the laser emitting arm and the laser receiving arm; inside the housing (1) are a dual-optical-path holographic measurement unit, a PIV turbulence measurement unit, and a control unit (27) for overall control; the dual-optical-path holographic measurement unit is used to generate two laser beams, one beam is transmitted along the original optical path and emitted through the laser emitting arm, and the other beam is redirected and transmitted and emitted through the laser emitting arm. After the two laser beams are emitted, they cross and are incident on the laser receiving arm through the sampling area, and are respectively imaged on a camera to obtain holographic images to realize cloud particle feature measurement; the PIV turbulence measurement unit is used to generate one laser beam and form a sheet light source, which is emitted from the laser emitting arm and illuminates the flow field between the sampling areas, and the turbulence field is measured synchronously by collecting the scattering images of the particles; The dual-optical-path holographic measurement unit includes a first measurement optical path disposed on the side of the laser emitting arm and a second measurement optical path disposed on the side of the laser receiving arm. The first measurement optical path includes a pulsed laser (2), a spatial filter (3), a collimating lens (4), a beam expander (5), a first dichroic mirror (6), a beam splitter (8), and two outgoing transmission branches disposed in sequence. The pulsed laser (2) emits a laser beam, which passes through the spatial filter (3) and the collimating lens (4) in sequence, and is expanded by the beam expander (5). The expanded laser pulse passes through the first dichroic mirror (6) and is split into two beams at the position of the beam splitter (8). The two beams are transmitted to different exit ports of the laser emitting arm by the two outgoing transmission branches respectively. The second measurement optical path includes two incident measurement branches for imaging the beams incident through different incident ports onto a camera respectively.

2. The cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry according to claim 1, characterized in that, One of the outgoing transmission branches includes a first reflecting mirror (9), a second dichroic mirror (13), and a first rotating prism (16) arranged in sequence; another outgoing transmission branch includes a second reflecting mirror (7) and a third reflecting mirror (11) arranged in sequence; one incident measurement branch includes a fourth reflecting mirror (22), a first lens (23), and a first camera (24) arranged in sequence; another incident measurement branch includes a second rotating prism (17), a second lens (19), and a second camera (20) arranged in sequence; the light beam transmitted along the original optical path is redirected at the first rotating prism (16) after passing through the second dichroic mirror (13). The laser beam exits from the first exit port (15) of the laser emitting arm, passes through the sampling area, and enters from the first entrance port (21) of the laser receiving arm. It is then redirected by the fourth reflector (22) and imaged on the first camera (24) by the first lens (23). Another beam, after being redirected 90° at the beam splitter (8), exits from the second exit port (12) of the laser emitting arm through the first reflector (7) and the third reflector (11). After passing through the sampling area, it enters from the second entrance port (18) of the laser receiving arm and imaged on the second camera (20) after passing through the second rotating prism (17) and the second lens (19).

3. The cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry according to claim 2, characterized in that, The dual-optical-path holographic measurement unit further includes a timing controller (26) for controlling the working timing of the first camera (24) and the second camera (20) according to the set exposure time sequence when a trigger signal is received. The trigger signal is generated when the pulsed laser (2) emits a laser beam. The dual-optical-path holographic measurement unit further includes a data acquisition and storage unit for acquiring and storing the holographic images recorded by the first camera (24) and the second camera (20).

4. The cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry according to claim 1, characterized in that, The laser emitting arm and the laser receiving arm are arranged symmetrically along the central axis and form a wedge shape with a sharp top. The laser emitting arm and the laser receiving arm are respectively provided with two or more light-transmitting holes as exit ports and entrance ports. The laser emitting arm is provided with at least three exit ports to emit the two beams generated by the dual-optical-path holographic measurement unit and the sheet light source generated by the PIV turbulence measurement unit. The laser receiving arm is provided with at least two entrance ends to correspond to the two beams generated by the dual-optical-path holographic measurement unit. The laser receiving arm on the side opposite to the third exit port (14) of the laser emitting arm used to emit the sheet light source generated by the PIV turbulence measurement unit is provided with a high-reflectivity material coating so that the sheet light source generated by the PIV turbulence measurement unit illuminates the flow field of the sampling area.

5. The cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry according to any one of claims 1 to 4, characterized in that, The PIV turbulence measurement unit includes a continuous laser (25), a cylindrical mirror, and a third camera (10). The continuous laser (25) emits a laser beam, which is deflected by 90° after passing through the first dichroic mirror (6) and is transmitted coaxially with the pulsed laser beam emitted by the pulsed laser (2). After being deflected at the position of the second dichroic mirror (13) by the beam splitter (8), it forms a sheet light source through the cylindrical mirror and emits the light from the corresponding outlet on the laser emitting arm to illuminate the flow field of the sampling area. A high reflectivity material coating is provided on the laser receiving arm on the side opposite to the third outlet (14) of the sheet light source generated by the PIV turbulence measurement unit on the laser emitting arm. The third camera (10) records the scattering image of the particles in the sampling area.

6. The cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry according to any one of claims 1 to 4, characterized in that, The housing (1) is also provided with a heat insulation plate (37), a heating unit and a temperature and humidity monitoring unit (31) connected to the control unit (27). The interior of the housing (1) is divided into multiple areas by the heat insulation plate (37), and multiple temperature and humidity sensors are provided in each of the divided areas. The temperature and humidity monitoring unit (31) monitors the temperature and / or humidity status of each divided area through the temperature and humidity sensors, and generates control signals to the control unit (27) according to the monitored temperature and / or humidity status. When the temperature or humidity is higher than a preset threshold, a first control signal is generated to the control unit (27) to control the power supply to be cut off. When the temperature is lower than the preset threshold, a second control signal is generated to the control unit (27) to control the heating unit to be turned on for heating.

7. The cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry according to any one of claims 1 to 4, characterized in that, It also includes a balancing tail fin disposed at the tail of the housing (1) for overall auxiliary balancing during ball-borne measurement. The balancing tail fin includes a connecting rod (34), a secondary tail fin (35), and a main tail fin (36) disposed in sequence. The main tail fin (36) is connected to the housing (1) through the connecting rod (34) and is positioned directly opposite the middle position between the laser emitting arm and the laser receiving arm. The secondary tail fin (35) is symmetrically arranged on both sides of the main tail fin (36).

8. A measurement method using the cloud particle turbulence synchronous measurement device based on digital holography and particle image velocimetry as described in any one of claims 1 to 7, characterized in that, Includes the following steps: When performing cloud particle feature measurement, a laser beam is emitted by a pulsed laser (2), passes through the spatial filter (3) and collimating lens (4) in sequence, and is expanded by a beam expander (5). The expanded laser pulse passes through the first dichroic mirror (6) and is split into two beams at the beam splitter (8). The beams that are transmitted along the original optical path pass through the second dichroic mirror (13) and are turned at the first rotating prism (16), exiting from the first exit port of the laser emitting arm. After passing through the sampling area, they exit from the first entry port of the laser receiving arm. The laser beam enters through the emitting port and is redirected again by the fourth reflecting mirror (22). It then passes through the first lens (23) and is imaged on the first camera (24) to obtain a holographic image. Another beam, after being redirected 90° at the beam splitter (8), exits from the second exit port of the laser emitting arm through the first reflecting mirror (7) and the third reflecting mirror (11). After passing through the sampling area, it enters from the second entrance port of the laser receiving arm and passes through the second rotating prism (17) and the second lens (19) before being imaged on the second camera (20) to obtain a holographic image. During turbulence measurement, a laser beam is emitted by a continuous laser (25), deflected by 90° after passing through the first dichroic mirror (6), and transmitted coaxially with the pulsed laser beam emitted by the pulsed laser (2). After being deflected at the position of the second dichroic mirror (13) by the beam splitter (8), the beam is emitted from the corresponding outlet on the laser emission arm to illuminate the flow field of the sampling area. The scattering image of the particles is recorded by the third camera (10).

9. The measurement method according to claim 8, characterized in that, The cloud particle feature measurement process also includes a fusion processing step of the holograms obtained from the dual optical paths. The specific steps include: Establish a coordinate system, where the coordinate system corresponding to the optical path traversed by the continuous laser (25) in the sampling area is denoted as ( x , y , z The coordinate systems of the two optical paths generated by the pulsed laser (2) are respectively denoted as ( x 1, y 1, z 1) and ( x 2, y 2, z 2); After obtaining particle information from the holographic images recorded by the two optical paths, the particle information is uniformly transformed to the coordinate system corresponding to the continuous laser (25) according to the following formula to obtain the final three-dimensional particle field characteristics: in, The angle between the two coordinate systems. , and Related to the included angle The coordinate translation coefficient.

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