Motorized high-speed wind tunnel femtosecond laser molecular marker speed measurement system

Abstract

The invention discloses a motorized high-speed wind tunnel femtosecond laser molecular marker speed measurement system, and belongs to the technical field of femtosecond laser molecular marker speed measurement. The problem of flow field measurement of integral movement is solved. The system comprises a movable femtosecond laser source platform, a plano-convex lens, a telephoto lens, an image intensifier, a high-speed camera and a computer device, femtosecond laser emitted by the movable femtosecond laser source platform penetrates through the plano-convex lens and irradiates a flow field area to be measured, the movable femtosecond laser source platform is connected with the image intensifier and the high-speed camera, the high-speed camera is connected with the image intensifier and the computer device, the image intensifier is connected with the telephoto lens, and the telephoto lens is connected with the computer device. The telephoto lens is used for shooting a to-be-measured flow field area irradiated by the femtosecond laser. According to the invention, the femtosecond laser, the temperature control module, the sequential control unit and the light path shaping component are packaged in the same movable platform in a centralized manner, so that the measurement system has good overall stability and deployment flexibility in a wind tunnel environment.

Description

Technical Field

[0001] This invention belongs to the field of femtosecond laser molecular marker velocimetry technology, specifically relating to a mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system. Background Technology

[0002] In wind tunnel testing and aerodynamics measurement, laser-based flow field measurement technology is widely used to measure local velocity, density changes, and flow structure due to its non-contact nature, fast response, and minimal interference with flow. However, such measurements often rely on multiple independent precision devices, including femtosecond lasers, optical reflection components, timing control units, and air conditioning and water cooling systems for stable operation. Existing testing systems are mainly arranged in fixed or distributed configurations, which is not conducive to rapid adjustments between different test sections and measurement points. Furthermore, the stability and repeatability of measurements are easily affected by long connecting lines between devices and significant variations in environmental conditions.

[0003] Wind tunnel testing is characterized by limited adjustment space, tight testing time, and high costs associated with repeated setup. When lasers, gain units, cooling systems, and other components are distributed, the optical path alignment cycle is long, environmental interference factors are numerous, and changes in the distance between different devices can easily introduce problems such as spot drift, synchronization errors, and beam path distortion. For experiments that require repeated switching between multiple model locations or observation windows, traditional fixed equipment layouts are insufficient to meet the requirements of high efficiency and high consistency.

[0004] Furthermore, femtosecond laser systems are highly sensitive to environmental conditions (temperature, humidity, vibration, air cleanliness, etc.), and it is difficult to maintain a consistent working environment for each dispersed device in a conventional test control room or wind tunnel. If the cooling or air conditioning system is arranged separately from the laser, asynchronous temperature control response times may occur, leading to laser instability and reducing the imaging signal-to-noise ratio.

[0005] Therefore, there is a lack of a flow field measurement system that can integrate and package key modules such as laser system, heat dissipation system and timing control in a structured manner, and can be moved as a whole to any test location. Summary of the Invention

[0006] The problem to be solved by this invention is to realize a flow field measurement system that is entirely mobile, and a mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system is proposed.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A mobile high-speed wind tunnel femtosecond laser molecular labeling velocimetry system includes a movable femtosecond laser source platform, a plano-convex lens, a telephoto lens, an image intensifier, a high-speed camera, and a computer device.

[0009] The femtosecond laser emitted by the movable femtosecond laser source platform passes through a plano-convex lens and irradiates the flow field region to be measured. The movable femtosecond laser source platform is connected to an image intensifier and a high-speed camera. The high-speed camera is connected to the image intensifier and a computer device. The image intensifier is connected to a telephoto lens, which is used to capture images of the flow field region to be measured irradiated by the femtosecond laser.

[0010] Furthermore, the upper part of the front of the movable femtosecond laser source platform is provided with a laser light output port, a steel handle, and a front door assembly; the lower part of the front of the movable femtosecond laser source platform is provided with a lower ventilation baffle; the upper part of the back of the movable femtosecond laser source platform is provided with an acrylic observation door assembly; the lower part of the back of the movable femtosecond laser source platform is provided with a wiring hole panel and a lower ventilation baffle; and the bottom of the movable femtosecond laser source platform is provided with universal casters.

[0011] Furthermore, the upper space inside the movable femtosecond laser source platform is equipped with a femtosecond laser, a reflector, a shock-absorbing air float, and a marble support. The femtosecond laser is placed on the marble support, and a shock-absorbing air float is installed at the bottom of the marble support. Multiple reflectors are arranged on the side of the femtosecond laser. The lower space inside the movable femtosecond laser source platform is equipped with an air conditioner, a water chiller, and a signal generator.

[0012] Furthermore, the reflector is used to adjust the laser transmission optical path to meet the optical path layout requirements under different experimental conditions.

[0013] Furthermore, the connector panel is provided with a power cord outlet, a control cord outlet, and a synchronous trigger signal cord outlet.

[0014] Furthermore, the signal generator is used to generate timing control signals to provide synchronous triggering for the coordinated operation of the high-speed camera, image intensifier, and laser.

[0015] Furthermore, the aforementioned mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system undergoes distance calibration before use.

[0016] Furthermore, a timing control design is performed on the aforementioned mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system.

[0017] Furthermore, the laser stripe images acquired by the mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system under different delay conditions are processed by an image processing algorithm to obtain clear laser stripe images.

[0018] The beneficial effects of this invention are:

[0019] This invention discloses a mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system. By encapsulating the femtosecond laser, temperature control module, timing control unit, and optical path shaping components within a single mobile platform, the measurement system exhibits excellent overall stability and deployment flexibility in a wind tunnel environment. The encapsulated structure maintains consistency in the laser optical path, heat dissipation conditions, and vibration environment, reducing optical path drift, inconsistent temperature control response, and circuit interference problems caused by dispersed equipment placement. The platform's mobility allows for rapid relocation between different test sections or measurement points, significantly reducing the time cost of system rebuilding and debugging, and improving the organizational efficiency of the experimental process. Furthermore, this invention processes laser stripe images acquired at different times, extracts the center position of each laser stripe, and calculates the target's velocity based on the pixel displacement of the stripe center in the image and the corresponding time interval, achieving non-contact velocity measurement. Combined with the calibration relationship between pixels and actual physical distance, the pixel displacement in the image domain can be accurately converted into actual spatial displacement, improving the quantitative accuracy of the velocimetry results. Meanwhile, by comprehensively calculating and averaging the measurement results of multiple laser stripes, the impact of single measurement errors and noise interference on the results is effectively reduced, enhancing the stability and repeatability of the velocity measurement results. This method still has good measurement reliability and engineering applicability in complex test environments. Attached Figure Description

[0020] Figure 1 is a schematic diagram of the structure of a mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system according to the present invention;

[0021] Figure 2 shows the front view and rear view of the mobile femtosecond laser source platform of the present invention, wherein (a) is the rear view and (b) is the front view;

[0022] Figure 3 shows the internal front view and three-dimensional view of the movable femtosecond laser source platform of the present invention, wherein (a) is the internal front view and (b) is the internal three-dimensional view;

[0023] Figure 4 shows the internal left view of the movable femtosecond laser source platform of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described specific embodiments are merely a part of the embodiments of the invention, and not all of them. The components of the specific embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations, and the invention may also have other embodiments.

[0025] Therefore, the following detailed description of specific embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected specific embodiments of the invention. All other specific embodiments obtained by those skilled in the art based on these specific embodiments without inventive effort are within the scope of protection of this invention.

[0026] To further understand the invention's content, features, and effects, the following specific embodiments are provided, and detailed descriptions are given in conjunction with Figures 1-4:

[0027] Example 1:

[0028] A mobile high-speed wind tunnel femtosecond laser molecular labeling velocimetry system includes a movable femtosecond laser source platform 1, a plano-convex lens 2, a telephoto lens 3, an image intensifier 4, a high-speed camera 5, and a computer device 6.

[0029] The femtosecond laser emitted by the movable femtosecond laser source platform 1 passes through the plano-convex lens 2 and irradiates the flow field region 7 to be measured. The movable femtosecond laser source platform 1 is connected to the image intensifier 4 and the high-speed camera 5. The high-speed camera 5 is connected to the image intensifier 4 and the computer device 6. The image intensifier 4 is connected to the telephoto lens 3. The telephoto lens 3 is used to photograph the flow field region 7 to be measured irradiated by the femtosecond laser.

[0030] Furthermore, the upper part of the front of the movable femtosecond laser source platform 1 is provided with a laser light output port 8, a steel handle 9, and a front door assembly 14; the lower part of the front of the movable femtosecond laser source platform 1 is provided with a lower ventilation block plate 12; the upper part of the back of the movable femtosecond laser source platform 1 is provided with an acrylic observation door assembly 10; the lower part of the back of the movable femtosecond laser source platform 1 is provided with a wiring hole panel 11 and a lower ventilation block plate 12; and the bottom of the movable femtosecond laser source platform 1 is provided with universal casters 13.

[0031] Furthermore, the upper space inside the movable femtosecond laser source platform 1 is equipped with a femtosecond laser 15, a reflector 16, a shock-absorbing air float 17, and a marble support 21. The femtosecond laser 15 is placed on the marble support 21, and the shock-absorbing air float 17 is installed at the lower part of the marble support 21. Multiple reflectors 16 are arranged on the side of the femtosecond laser 15 for adjusting the laser transmission optical path to meet the optical path layout requirements under different experimental conditions.

[0032] The lower space inside the movable femtosecond laser source platform 1 is equipped with an air conditioner 18, a water chiller 19, and a signal generator 20.

[0033] Furthermore, the connector panel 11 is provided with a power cord outlet, a control cord outlet, and a synchronous trigger signal cord outlet.

[0034] Furthermore, the signal generator 20 is used to generate timing control signals to provide synchronous triggering for the coordinated operation of the high-speed camera, image intensifier, and laser.

[0035] Furthermore, a detailed description of a mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system is provided below:

[0036] The movable femtosecond laser source platform is used to stably output femtosecond lasers with high peak power.

[0037] The plano-convex lens is used to focus the laser beam, inducing a series of complex changes in gas molecules to form a self-sustaining emission process on the order of tens of microseconds. The smaller the focal length, the smaller the focused laser spot, and the stronger the brightness.

[0038] The telephoto lens is a hardware device for imaging;

[0039] The high-speed camera is a fluorescence image acquisition and storage device. It requires the use of global shutter technology to expose the entire image simultaneously, avoiding spatial distortion and ensuring geometric accuracy. This increases the accuracy of the measurement results.

[0040] The computer device is used to store images and to perform velocity calculations based on those images.

[0041] As shown in Figure 2, the laser output port is used to output the laser beam processed by the femtosecond laser and pulse compression module inside the platform, providing stable and reliable light output for the external hypersonic flow field.

[0042] The steel handle is used to provide a stable force point during equipment movement, pushing, pulling, or position adjustment, making it easy for operators to move the platform safely and conveniently.

[0043] The acrylic observation gate assembly is used to enable visual viewing of the internal optical path, structural layout, and operating status of the platform while ensuring optical path safety and protection requirements, and is also used for forward opening operations during routine maintenance.

[0044] The connector panel provides standardized lead-out channels for power lines, control lines, and synchronous trigger signal lines, thereby enabling a reliable connection between the external control system and the core devices inside the platform.

[0045] The lower ventilation baffle is used to provide a heat dissipation and ventilation channel for the platform's internal air conditioning system, water cooling system and electronic modules, so as to maintain a stable thermal management environment for the laser and its supporting components.

[0046] The omnidirectional casters are used to enable the entire platform to move flexibly, be quickly deployed, and lock its position within the test site, in order to meet the flexible deployment requirements under multiple test conditions.

[0047] The rear section is used for backward inspection, troubleshooting, and modular replacement of the laser, drive power supply, and heat dissipation system inside the platform, facilitating safe and reliable back-end operations by maintenance personnel.

[0048] As shown in Figure 3, the femtosecond laser is used to provide a stable and high-intensity femtosecond laser beam, providing a precise excitation source for the external flow field.

[0049] The shock-absorbing air flotation is used to isolate external vibrations, ensuring the equipment remains stable during operation and preventing vibrations from affecting laser accuracy and experimental results.

[0050] The air conditioner is used to regulate the temperature and humidity inside the equipment, ensuring a stable working environment for the laser and other sensitive components, thereby improving the system's operational reliability and service life.

[0051] The water chiller is used to effectively dissipate heat from the laser, maintain the laser's optimal operating temperature, and prevent overheating from causing a decline in system performance.

[0052] The signal generator is used to generate precise timing control signals to provide synchronous triggering for the coordinated operation of the high-speed camera, image intensifier, and laser, ensuring the timing consistency between the laser output and the detection system.

[0053] The marble support frame provides a stable foundation platform, reduces vibration, and improves the overall stability of the equipment to ensure precise positioning of the laser path and other critical components.

[0054] As shown in Figure 4, the reflector is used to precisely reflect the laser beam from the femtosecond laser to achieve effective path adjustment of the laser beam.

[0055] Furthermore, the aforementioned mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system undergoes distance calibration before use.

[0056] Furthermore, to establish the proportional relationship between image pixels and actual physical distances in the imaging system, distance calibration is performed on the system. During calibration, a standard reference object of known size is placed in the measurement plane, and images are acquired. The pixel spacing between adjacent feature points in the reference object is extracted in the image using image processing methods, and combined with their corresponding actual physical distances, the proportional coefficient k between pixel distance and physical distance is calculated, thereby realizing the conversion from pixel scale to actual spatial scale.

[0057] Specifically, one or a combination of the following calibration methods can be used:

[0058] Ruler calibration method: Place a standard ruler with precise graduations on the measuring plane, acquire its image and extract the pixel distance between adjacent graduation lines in the image. Calculate the proportional relationship between pixels and physical distance based on the actual length between known graduations. This method is suitable for planar measurements and is easy to operate.

[0059] Checkerboard calibration method: Using a checkerboard calibration board with known geometric dimensions, the pixel coordinates of the checkerboard corner points are extracted and combined with the actual physical distance between adjacent corner points to establish a mapping relationship between pixel scale and spatial scale.

[0060] Through the above distance calibration process, a stable and reliable pixel-physical distance conversion relationship k can be obtained in the imaging system, providing a basis for subsequent displacement measurement and velocity calculation.

[0061] Furthermore, a timing control design is performed on the aforementioned mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system.

[0062] Furthermore, laser stripe images are acquired under different delay conditions. Specifically, after receiving a pulse signal, the femtosecond laser generates a femtosecond laser pulse, which illuminates the measured flow field region to form transient laser stripes. The imaging system performs multiple independent exposures under preset timing control, with each exposure corresponding to a gate opening, thereby acquiring multiple independent laser stripe images.

[0063] During a measurement, the image intensifier sequentially opens its gating window according to different delay parameters. The initial gating opening time is set to t0 after the laser trigger delay (generally, t0 is approximately 0), and each subsequent gating opening is delayed relative to the previous one. When a total of i images are acquired, the time of the i-th gating opening is t0. .

[0064] Each gated exposure corresponds to the laser stripe information formed under a single laser pulse. Therefore, each image only records the spatial distribution of the laser stripes at a specific point in time. By jointly analyzing multiple laser stripe images acquired in chronological order, the displacement variation law of the laser stripes over time can be obtained, thereby enabling the measurement of flow field velocity.

[0065] Furthermore, the laser stripe images acquired by the mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system under different delay conditions are processed by an image processing algorithm to obtain clear laser stripe images.

[0066] Furthermore, image processing algorithms are used to process the laser stripe images acquired under different delay conditions to extract the pixel coordinates of the center point of each laser stripe; based on the corresponding delay time, the image pixel displacement between the center points of laser stripes with different delays is calculated, and combined with the calibrated scaling factor k, the pixel displacement is converted into actual spatial displacement; further, the target's motion speed is calculated by combining the time difference between adjacent laser stripes.

[0067] Specifically, according to time-series control, n images are acquired. , , , Let I be an example. Let I be any image in the set. Calculate the center of the laser stripe using the following steps.

[0068] S1. Gaussian smoothing and scale space construction: To suppress noise and enhance the stripe structure, the original image is subjected to Gaussian filtering. I ,in = Let the half-width of the laser stripe be approximately w (pixels). ;

[0069] S2. For the smoothed image Calculate the first and second derivatives. First derivative , Second derivative: , , ;

[0070] S3. For each pixel (x, y), construct the Hessian matrix and perform eigenvalue decomposition: Hessian matrix:

[0071] ;

[0072] right Eigenvalue decomposition of the matrix yields , and the corresponding unit eigenvector , ;

[0073] S4. For laser stripes: the eigenvalues ​​corresponding to the normal and reverse directions satisfy... <0, eigenvalues ​​corresponding to the tangential direction of the stripes Pixels that meet the above conditions are identified as candidate points for stripe ridges, where n = The normal direction of the stripes;

[0074] S5. At the candidate points of the stripe ridges that satisfy S4, n= in the reverse direction along the normal. Find the extremum location of the second-order Taylor expansion; the Taylor expansion grayscale function along the normal direction can be expressed as... ,in = , = Setting the first derivative to 0, we can obtain the offset of the extreme point. ;

[0075] S6. Calculate the coordinates of the center point of the laser stripe at the sub-pixel boundary level. , ):

[0076] ;

[0077] when When the pixel value is less than 0.5 pixels, the point is considered a valid sub-pixel centerline point; the center position of the entire laser line is obtained by averaging all valid sub-pixel centerline points. , );

[0078] S7. The center positions of all n laser stripes are calculated using the method described above. ;

[0079] For any two stripes i and j (1... n); the pixel displacement vector is: ;

[0080] The corresponding pixel displacement modulus is:

[0081] ;

[0082] Let the delay time corresponding to the i-th laser stripe be . ,but = ;

[0083] The speed of the pixel domain is: The scaling factor k, obtained from distance calibration, is the ratio of the pixel distance to the actual distance. Therefore, the physical velocity is... k ;

[0084] By averaging the results for any two laser lines, a total of [number] can be calculated. Group results; average speed:

[0085] = , The interval between two adjacent laser lines;

[0086] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0087] Although this application has been described above with reference to specific embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of this application. In particular, as long as there is no structural conflict, the features in the specific embodiments disclosed in this application can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, this application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system, characterized in that, Includes a movable femtosecond laser source platform (1), a plano-convex lens (2), a telephoto lens (3), an image intensifier (4), a high-speed camera (5), and a computer device (6). The femtosecond laser emitted by the movable femtosecond laser source platform (1) passes through the plano-convex lens (2) and irradiates the flow field region (7) to be measured. The movable femtosecond laser source platform (1) is connected to the image intensifier (4) and the high-speed camera (5). The high-speed camera (5) is connected to the image intensifier (4) and the computer device (6). The image intensifier (4) is connected to the telephoto lens (3). The telephoto lens (3) is used to photograph the flow field region (7) to be measured irradiated by the femtosecond laser.

2. The mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system according to claim 1, characterized in that, The movable femtosecond laser source platform (1) has a laser output port (8), a steel handle (9), and a front door assembly (14) on the upper part of the front side. The movable femtosecond laser source platform (1) has a lower ventilation baffle (12) on the lower part of the front side. The movable femtosecond laser source platform (1) has an acrylic observation door assembly (10) on the upper part of the back side. The movable femtosecond laser source platform (1) has a wire insertion hole panel (11) and a lower ventilation baffle (12) on the lower part of the back side. The movable femtosecond laser source platform (1) has universal casters (13) at the bottom.

3. The mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system according to claim 2, characterized in that, The upper space inside the movable femtosecond laser source platform (1) is equipped with a femtosecond laser (15), a reflector (16), a shock-absorbing air float (17), and a marble support (21). The femtosecond laser (15) is placed on the marble support (21), and the shock-absorbing air float (17) is installed on the lower part of the marble support (21). Multiple reflectors (16) are arranged on the side of the femtosecond laser (15). The lower space inside the movable femtosecond laser source platform (1) is equipped with an air conditioner (18), a water chiller (19), and a signal generator (20).

4. The mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system according to claim 3, characterized in that, The reflector is used to adjust the laser transmission optical path to meet the optical path layout requirements under different experimental conditions.

5. The mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system according to claim 4, characterized in that, The connector panel (11) is provided with a power line lead-out hole, a control line lead-out hole and a synchronous trigger signal line lead-out hole.

6. The mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system according to claim 5, characterized in that, The signal generator (20) is used to generate timing control signals to provide synchronous triggering for the coordinated operation of the high-speed camera, image intensifier, and laser.

7. A mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system according to claim 6, characterized in that, The aforementioned mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system undergoes distance calibration before use.

8. The mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system according to claim 7, characterized in that, The timing control design of the aforementioned mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system is carried out.

9. A mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system according to claim 8, characterized in that, The laser stripe images acquired by the mobile high-speed wind tunnel femtosecond laser molecular marker velocimetry system under different delay conditions are processed by an image processing algorithm to obtain clear laser stripe images.

Images