Multifunctional binocular camera background orientation schlieren instrument

Abstract

The utility model discloses a multifunctional binocular camera background orientation schlieren instrument which comprises a supporting module, a lifting system, a background plate and a rotary stretching module, an image acquisition module is arranged on the lifting system, the lifting system comprises a lifting frame, a movable lifting platform is arranged on the lifting frame, and the background plate is arranged on the lifting platform. The image acquisition module comprises an image acquisition table arranged on a lifting table, a linear guide rail, a sliding block, a camera seat and a CCD industrial camera, the supporting module comprises a first supporting plate and a second supporting plate, the first supporting plate is provided with a first sliding groove and a first rack, the rotary stretching module comprises an upper gear clamp and a lower gear clamp which can slide, the upper gear clamp is provided with an upper gear, and the lower gear clamp is provided with a lower gear. A lower gear is arranged on the lower gear clamp, a bearing locking sleeve is arranged between the upper gear and the lower gear, and a thrust ball bearing is arranged in the lower end of the bearing locking sleeve. The schlieren instrument can complete omnibearing flow field information acquisition, more reliable three-dimensional reconstruction and displacement measurement, a wider view field is obtained, the influence of environment illumination change is reduced, and higher robustness is obtained.

Description

Technical Field

[0001] This utility model belongs to the field of background orientation schlieren measurement, specifically relating to a multifunctional binocular camera background orientation schlieren instrument. Background Technology

[0002] Background-oriented schileren (BOS) is a novel non-contact optical diagnostic technique used for visualizing flow fields of varying density and quantitatively measuring refractive index fields. It is widely used to visualize fluid flows, including liquids and gases, to study fluid dynamics phenomena such as eddies, turbulence, and boundary layers. Displacement estimation in fluid image sequences has always been an essential analytical step in fluid mechanics, medicine, and computer vision. Accurately extracting dense displacement vector fields from fluid visualization images is crucial for understanding the fundamental physical phenomena and flow mechanisms within these images.

[0003] BOS (Browser-Oriented System) can be broadly divided into three parts: hardware construction, background image displacement estimation, and refractive index reconstruction. The accuracy of BOS image displacement estimation directly determines the accuracy of refractive index field reconstruction. Currently, background schlieren techniques suffer from limitations such as optical path construction methods, vibration and illumination inhomogeneity, blurring and defocusing effects, and refocusing effects from volumetric refraction. These limitations make it difficult for BOS image sequences to meet the constant brightness assumption, resulting in low-precision and inaccurate flow field estimation. Current background directional schlieren techniques mostly rely on monocular camera measurements, which suffer from structural limitations in obtaining accurate 3D depth information and, due to limited field of view, cannot cover the required area. For BOS image processing, traditional cross-correlation algorithms require a large query window to ensure sufficient signal-to-noise ratio, limiting the algorithm's spatial resolution. Furthermore, its multi-grid iterative algorithm (WIDIM) is time-consuming. Utility Model Content

[0004] The purpose of this invention is to overcome the limitations of existing measurement devices in terms of flow field information dimensionality and observation area, as well as the low efficiency, low accuracy, and susceptibility to changes in lighting conditions. This invention provides a multifunctional binocular camera background orientation schlierenoscope. The observation platform can be raised, lowered, rotated, and extended to complete omnidirectional flow field information acquisition. The binocular camera enables more reliable 3D reconstruction and displacement measurement, obtains a wider field of view, reduces the impact of ambient lighting changes, and achieves higher robustness.

[0005] The technical solution to achieve the purpose of this utility model is:

[0006] A multifunctional binocular camera background orientation schlieren scanner includes a support module, a lifting system and a background plate respectively located at both ends of the support module, a rotation and stretching module in the middle of the support module, and an image acquisition module on the lifting system.

[0007] The lifting system includes a first lifting system and a second lifting system of identical specifications. The first lifting system includes a vertical lifting frame, which comprises a vertical plate and a first extension plate and a second extension plate perpendicular to both ends of the vertical plate. Two spaced-apart guide rods and a ball screw are provided between the first and second extension plates, with the ball screw located in the middle of the two guide rods. A servo motor with a coupling is located on the outward-facing surface of the first extension plate. The coupling passes through the first extension plate and connects to a fixed-end bearing seat on the inner wall of the first extension plate. A support-end bearing seat is located on the inner wall of the second extension plate, with both ends of the ball screw located on the fixed-end bearing seat and the support-end bearing seat, respectively. A lifting frame rib for supporting the lifting frame is provided on the vertical plate opposite to the second extension plate. The lifting frame also includes a lifting platform that moves through the two guide rods and the ball screw. A screw nut seat is provided on the lifting platform, through which the ball screw passes.

[0008] The image acquisition module includes a first image acquisition module and a second image acquisition module of the same specifications, respectively mounted on a first lifting system and mounted on a second lifting system. The first image acquisition module includes an image acquisition platform mounted on the lifting platform. The image acquisition platform is provided with a linear guide rail facing the same direction as the first extension plate. A slidable slider is provided on the linear guide rail. From bottom to top, a camera mount and a CCD industrial camera are arranged on the upper surface of the slider. A guide rail limiting clamp is provided at the outward end of the linear guide rail.

[0009] The support module includes a first support plate and a second support plate of the same specifications, which are movably and cross-stacked, with the first support plate on top and the second support plate on the bottom. The first support plate has a first rectangular groove in its middle, one long side of which has a first sliding groove of the same length as the long side, and the other long side has a first toothed rack of the same length as the long side. Caster wheel assemblies are provided on the bottom surfaces of both ends of the first support plate, and bullseye wheel assemblies are provided on the bottom surfaces of both ends of the second support plate.

[0010] The rotary stretching module includes an upper gear clamp with a groove at one end, which is slidable on a first slide groove. The other end of the upper gear clamp has a first upper gear extension plate of the same length and direction as the groove. The first upper gear extension plate has a candle-shaped hole. An upper gear is positioned between the groove of the upper gear clamp and the first rack. A first rectangular slider is positioned on the back of the groove of the upper gear clamp, and the first rectangular slider can slide within the first slide groove. The rotary stretching module also includes a lower gear clamp with a U-shaped groove, which is slidable on a second slide groove of a second support plate. A lower gear is positioned between the U-shaped groove of the lower gear clamp and the second rack. The back of the U-shaped groove of the lower gear clamp... The unit is equipped with a second rectangular slider, which can slide within a second groove. A stepped bearing locking sleeve is provided between the upper and lower gears. A thrust ball bearing is located near the interior of the lower gear within the bearing locking sleeve. The outer wall of the thrust ball bearing is interference-fitted with the inner wall of the lower end of the bearing locking sleeve, and the inner wall of the thrust ball bearing is interference-fitted with the shaft of the lower gear. The thrust ball bearing can withstand a large axial force and enables relative rotation of the upper and lower gears, thereby achieving relative rotation of the first and second support plates. The stepped hole in the bearing locking sleeve is interference-fitted with the shaft of the upper gear, preventing relative slippage. A locking pin is also provided on the side of the bearing locking sleeve.

[0011] The background panel includes a first background panel and a second background panel of the same specifications, respectively disposed at the same end of the first support panel and the second support panel. The first background panel includes a background support base with vertical edges at both ends. The inner sides of the two edges of the background support base are provided with horizontal slots, and the slots are provided with a first colored striped background. The back of the lower edge of the background support base is provided with a background rib.

[0012] The first lifting system and the second lifting system are located at the other ends of the first support plate and the second support plate, respectively. The first lifting system faces the first background plate, and the second lifting system faces the second background plate. The first image acquisition module and the second image acquisition module on the first lifting system and the second lifting system face the first colored striped background and the second colored striped background, respectively.

[0013] The first groove on the first support plate is on the same side as the second groove on the second support plate, and the first rack is on the same side as the second rack.

[0014] The fixed end bearing housing is equipped with a set of angular contact bearings mounted in opposite directions, which can withstand loads in both forward and reverse directions and play a fixing role.

[0015] The ball screw contacts the balls inside the screw nut seat so as to convert the rotational motion of the ball screw into the linear motion of the screw nut seat.

[0016] The combination of the two guide rods and the ball screw can improve the stability of the lifting system.

[0017] The support end bearing seat is bolted to the inner wall of the second extension plate of the lifting frame. The support end bearing seat is an angular contact bearing used to provide vertical support force.

[0018] The lifting frame ribs bear the longitudinal strength and provide support.

[0019] The lifting system works as follows: A servo motor drives the ball screw to rotate. The balls inside the ball screw nut seat contact the ball screw and move along the rotating thread track inside the ball screw nut seat, causing the ball screw nut seat to move linearly up and down along the ball screw. At the same time, the lifting platform that cooperates with the ball screw nut seat and the guide rod slides up and down to complete the lifting motion.

[0020] The linear guide rail is fixed to the image acquisition stage by bolts, and the guide rail limit clamp is locked on the outer end face of the linear guide rail to prevent the slider from derailing.

[0021] The image acquisition module works as follows: The lifting system drives the image acquisition module to move up and down to adjust it to a suitable height; the CCD industrial camera slides back and forth on the lifting platform by manually sliding the slider, reducing the work of adjusting the focal length of the CCD industrial camera.

[0022] The bullseye wheel assembly mounted on the bottom surface of the second support plate and the caster wheel assembly mounted on the bottom surface of the first support plate are used to support the support plate module on the ground and enable it to slide 360° in all directions.

[0023] Working principle of the support module: This module is used to adjust the horizontal movement of the entire schlieren device in all directions and is in direct contact with the ground to provide support. It can also stretch or rotate the first and second support plates to achieve the stretching and rotation of the entire schlieren device.

[0024] A candle is provided on the candle hole of the first upper gear plate. The candle is lit so that the schlieren phenomenon can be observed in the area above the flame corresponding to the first and second colored striped backgrounds.

[0025] The upper gear and the lower gear mesh with the first rack and the second rack respectively, so as to achieve horizontal stretching of the first support plate and the second support plate relative to the upper and lower gears.

[0026] The upper gear clamp includes a vertical upper gear plate. At the end of the upper gear plate away from the first upper gear extension plate, there are a second upper gear extension plate and a third upper gear extension plate that are in the same direction as the first upper gear extension plate. A groove portion of the upper gear clamp is formed between the second upper gear extension plate and the third upper gear extension plate. Both the second upper gear extension plate and the third upper gear extension plate are provided with a first through hole for the shaft of the upper gear to pass through. The lower gear clamp includes a lower gear plate, and a first lower gear extension plate and a second lower gear extension plate that are perpendicular to both ends of the lower gear plate. A U-shaped groove portion of the lower gear clamp is formed between the first lower gear extension plate and the second lower gear extension plate. Both the first lower gear extension plate and the second lower gear extension plate are provided with a second through hole for the shaft of the lower gear to pass through.

[0027] The bearing locking sleeve has milled flat surfaces on both sides, with a through hole drilled on one side and a threaded hole tapped on the other side, so that the through hole and the threaded hole are connected. The shaft of the lower gear has a third through hole in the transverse direction. After the shaft of the lower gear extends into the inner wall of the thrust ball bearing and is interference-fitted, the locking pin passes through the through hole of the bearing locking sleeve, the third through hole of the shaft of the lower gear and the threaded hole of the bearing locking sleeve in sequence. The locking pin can realize the relative fixation of the upper and lower gears, thereby realizing the same distance stretching of the first support plate and the second support plate.

[0028] The first lifting system, the first image acquisition module, the first support plate, and the first background plate form a schlieren device, and the second lifting system, the second image acquisition module, the second support plate, and the second background plate form another schlieren device.

[0029] Working principle of the rotation stretching module: When adjusting the relative angle of the two schlieren cameras, remove the locking pin, rotate the schlieren camera, and after the adjustment is completed, insert the locking pin; when adjusting the distance between the image acquisition module and the upper gear clamp, ensure that the locking pin is in the inserted state, and then stretch the two schlieren cameras.

[0030] The background support base has two side slots, one side of which is open and the other side is closed, to prevent the first colored striped background from sliding out.

[0031] Background panel working principle: Used to place the first and second colored striped backgrounds to obtain a large field of view schlieren.

[0032] Working principle of the schlieren spectrometer: First, adjust the rotation and stretching module. To adjust the relative angle between the two schlieren spectrometers, pull out the locking pin and rotate the support module. After rotation, the locking pin must be reinserted to prevent angle changes. Next, to adjust the relative distance between the image acquisition module and the flow field to be measured, stretch the support module back and forth. This allows for equal stretching of the first and second support plates. Second, arrange the background plate. Insert the first and second colored striped backgrounds into the background support base. Light the candle on the upper gear clamp to form the flow field to be measured. Then, adjust the lifting system, start the servo motor, and drive the lifting platform to move vertically, aligning the lens with the flow field area to be measured. Finally, adjust the image acquisition module and move the camera mount to ensure clear imaging by the CCD industrial camera, and then acquire the image.

[0033] A flow field displacement estimation method, comprising the aforementioned multifunctional binocular camera background orientation schlieren, the method comprising the following steps:

[0034] 1) Before lighting the candle, the angle and distance of the CCD industrial camera are fixed by the image acquisition module, support module, and rotation stretching module. The CCD industrial camera of the first image acquisition module is the left camera, and the CCD industrial camera of the second image acquisition module is the right camera. The left and right cameras respectively capture the first and second colored stripe backgrounds of the first and second background boards as reference background images I1 and I2. After lighting the candle, the first and second colored stripe backgrounds of the first and second background boards are captured again. The distorted image obtained by the left camera is I1. L The distorted image obtained by the right camera is I. R ;

[0035] 2) Set I1, I2, I L I R As input, a color image is converted to a grayscale image as follows: a pixel of the color image is represented as (R, G, B) to obtain a grayscale image, where R, G, and B represent the intensities of the red, green, and blue channels, respectively. The pixel value of the grayscale image is calculated using a weighted average formula: grayscale image pixel value = 0.299 * R + 0.587 * G + 0.114 * B;

[0036] 3) The left reference background image after being converted to grayscale and the left distorted image are used as a set of inputs, i.e., P1=(I1,I... L The right reference background image and the right distorted image are used as a set of inputs, i.e., P2=(I2,I... R The input objects for P1 and P2 are the optical flow algorithm framework;

[0037] 4) Optical Flow Algorithm: The main idea is that when an object moves in consecutive image frames, its pixel values ​​will change continuously. These changes can be obtained by performing pixel-by-pixel correlation matching analysis on two images. Typically, the input is two frames of images, and the output is an optical flow field representing the displacement vector of each pixel. The image pyramid-based optical flow algorithm is a technique for improving optical flow estimation. It performs multi-scale analysis of the image to handle motion of different scales and object sizes. It employs a "coarse-to-fine" multi-resolution scheme and warping techniques to handle large displacements in the flow field. Downsampling part: The optical flow algorithm uses a 6-layer image pyramid for downsampling, each layer being half the scale of the previous layer. Starting from the original image, a series of images with different resolutions are generated through multiple downsampling steps. Estimation part: Starting from the bottom of the pyramid, convolutional layers are applied to each pyramid layer to extract features. Beginning with low-resolution layers, a coarse optical flow is estimated first. Then, based on the estimation results of the previous layer, upsampling is used to generate a higher-resolution initial estimate for the current layer. Accumulated optical flow: Based on the estimation results at different scales, the optical flow is accumulated on the final high-resolution image to obtain the final optical flow field. When calculating the estimated optical flow, a loss function needs to be defined so that the model can automatically learn useful structures, features, or representations from unlabeled data. The loss function of the optical flow algorithm is based on minimizing an energy function and consists of a data term and a smoothing term. The data term satisfies the constant brightness and constant gradient assumptions, while the smoothing term is defined by constraints on divergence and curl to reduce the impact of outliers on motion estimation, thereby improving robustness to noise and illumination.

[0038] ,

[0039] in , It is a non-convex generalized Charbonnier penalty function, whose parameters are , , , Indicates image brightness. Indicates time, Denotes divergence, Indicates curl, , ;

[0040] 5) Input the object pairs P1 and P2 into the optical flow algorithm framework of step 4) respectively to obtain the displacement estimate of the flow field at full resolution, with U1 on the left and U2 on the right.

[0041] 6) Large Field of View and 3D Reconstruction: First, depth estimation is performed using parallax, i.e., the difference in horizontal position between corresponding points in the left and right cameras. Then, stereo vision triangulation is used to calculate the 3D coordinates of the corresponding points. The origin of the camera coordinate system is at the optical center of the camera, and the optical axis of the camera is perpendicular to the image plane. For a pixel (x1, y1) in the left camera and a pixel (x2, y2) in the right camera, the corresponding 3D coordinates (X, Y, Z) of the left camera can be calculated using the following formula, and the same applies to the right camera:

[0042] ,

[0043] in, Indicates the pixel coordinates of the optical center of the left camera. Indicates the focal length of the left and right cameras. Indicates the baseline of the left and right cameras. It's the parallax of the left camera. It's about depth.

[0044] This schlieren instrument can be raised, lowered, rotated, and extended through the observation platform to complete the acquisition of omnidirectional flow field information. It can also achieve more reliable three-dimensional reconstruction and displacement measurement through a binocular camera, obtain a wider field of view, reduce the impact of changes in ambient light, and achieve higher robustness. Attached Figure Description

[0045] Figure 1 This is a structural diagram of the schlieren device in the embodiment;

[0046] Figure 2 This is a structural diagram of the first lifting mechanism in the embodiment;

[0047] Figure 3 This is a structural diagram of the first image acquisition module in the embodiment;

[0048] Figure 4 This is a top view of the support module in the embodiment;

[0049] Figure 5 for Figure 4 A bottom view;

[0050] Figure 6 This is an assembly diagram of the rotary stretching module in the embodiment;

[0051] Figure 7 This is an exploded view of the rotary stretching module in the embodiment;

[0052] Figure 8 This is a structural diagram of the upper gear clamp in the embodiment;

[0053] Figure 9 This is a structural diagram of the first background plate in the embodiment;

[0054] Figure 10This is a flowchart of the method in the embodiment;

[0055] Figure 11 The flow field displacement diagrams obtained in the embodiments are shown in (a) and (b).

[0056] Figure 12 The following are renderings of the embodiments, wherein (a) is a rendering of the high-precision large field of view estimation and (b) is a rendering of the three-dimensional reconstruction.

[0057] In the diagram, 01. Lifting System; 1. Coupling; 2. Ball Screw; 3. Lifting Frame; 301. Vertical Plate; 302. First Extension Plate; 303. Second Extension Plate; 4. Lifting Platform; 5. Lifting Frame Rib; 6. Support End Bearing Seat; 7. Smooth Rod; 8. Screw Nut Seat; 9. Fixed End Bearing Seat; 10. Servo Motor; 02. Image Acquisition Module; 11. Image Acquisition Stage; 12. CCD Industrial Camera; 13. Camera Mount; 14. Slider; 15. Linear Guide Rail; 16. Guide Rail Limiting Clamp; 03. Support Module; 17. First Support Plate; 18. First Slide Groove; 19. First Rack; 20. Bullseye Wheel Assembly; 21. Caster Wheel Assembly; 04. Rotary Tension Module; 22. Upper Gear Clamp. 201. First upper gear extension plate 2202. Second upper gear extension plate 2203. Third upper gear extension plate 2204. First rectangular slider 2205. First through hole 2206. Upper gear plate 23. Upper gear 24. Bearing locking sleeve 25. Locking pin 26. Lower gear 2601. Third through hole 27. Thrust ball bearing 28. Lower gear clamp 2801. Second rectangular slider 2802. Lower gear plate 2803. First lower gear extension plate 2804. Second lower gear extension plate 2805. Second through hole 29. Candle 06. Background plate 30. First colored striped background 31. Background support base 32. Background rib plate 33. Slot. Detailed Implementation

[0058] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention.

[0059] Example:

[0060] Reference Figure 1 A multifunctional binocular camera background orientation schlieren scanner includes a support module 03, a lifting system 01 and a background plate 06 respectively located at both ends of the support module 03, a rotation and stretching module 04 located in the middle of the support module 03, and an image acquisition module 02 located on the lifting system 01.

[0061] The lifting system 01 includes a first lifting system and a second lifting system of the same specifications, such as... Figure 2As shown, the first lifting system includes a vertical lifting frame 3. The lifting frame 3 includes a vertical plate 301 and a first extension plate 302 and a second extension plate 303 perpendicular to both ends of the vertical plate 301. Two spaced-apart guide rods 7 and a ball screw 2 are provided between the first extension plate 302 and the second extension plate 303. The ball screw 2 is located in the middle of the two guide rods 7. A servo motor 10 with a coupling 1 is provided on the outward-facing surface of the first extension plate 302. The coupling 1 passes through the first extension plate 302 and is connected to the first extension plate 303. The inner wall of the second extension plate 303 is connected to the fixed end bearing seat 9, and the inner wall of the second extension plate 303 is provided with the support end bearing seat 6. The two ends of the ball screw 2 are respectively located on the fixed end bearing seat 9 and the support end bearing seat 6. The vertical plate 301 of the second extension plate 303 is provided with a lifting frame rib 5 for supporting the lifting frame 3. The lifting frame 3 is also provided with a lifting platform 4 that moves through the two smooth rods 7 and the ball screw 2. The lifting platform 4 is provided with a screw nut seat 8, and the ball screw 2 passes through the screw nut seat 8. In this example Figure 1 In lifting system 01, the part located at the front is the second lifting system, and the part at the rear is the first lifting system.

[0062] The image acquisition module 02 includes a first image acquisition module of the same specifications respectively installed on the first lifting system and a second image acquisition module installed on the second lifting system, such as... Figure 3 As shown, the first image acquisition module includes an image acquisition platform 11 mounted on a lifting platform 4. The image acquisition platform 11 is equipped with a linear guide rail 15 facing the same direction as the first extension plate 302. A slidable slider 14 is mounted on the linear guide rail 15. A camera mount 13 and a CCD industrial camera 12 are sequentially mounted on the upper surface of the slider 14 from bottom to top. A guide rail limiting clip 16 is provided at the outward-facing end of the linear guide rail 15.

[0063] like Figure 4 , Figure 5 As shown, the support module 03 includes a first support plate 17 and a second support plate of the same specifications, which are movably and cross-stacked. The first support plate 17 is on top, and the second support plate is on the bottom. The first support plate 17 has a first rectangular groove in the middle. One long side of the first rectangular groove has a first sliding groove 18 of the same length as the long side, and the other long side has a first rack 19 of the same length as the long side. Caster wheel sets 21 are provided on the bottom surfaces of both ends of the first support plate 17, and bullseye wheel sets 20 are provided on the bottom surfaces of both ends of the second support plate.

[0064] like Figure 6 , Figure 7As shown, the rotary stretching module 04 includes an upper gear clamp 22 with a groove at one end that is slidable on the first slide groove 18. The other end of the upper gear clamp 22 has a first upper gear extension plate 2201 of the same direction and length as the groove. The first upper gear extension plate 2201 has a candle hole. An upper gear 23 is provided between the groove of the upper gear clamp 22 and the first rack 19. A first rectangular slider 2204 is provided on the back of the groove of the upper gear clamp 22, and the first rectangular slider 2204 can slide within the first slide groove 18. The rotary stretching module 04 also includes a lower gear clamp 28 with a U-shaped groove that is slidable on the second slide groove of the second support plate. A lower gear 26 is provided between the U-shaped groove of the lower gear clamp 28 and the second rack. A second rectangular slider 2801 is provided on the back of the groove. The second rectangular slider 2801 can slide within the second groove. A stepped bearing locking sleeve 24 is provided between the upper gear 23 and the lower gear 26. A thrust ball bearing 27 is provided inside the bearing locking sleeve 24 near the lower gear 26. The outer wall of the thrust ball bearing 27 is interference-fitted with the inner wall of the lower end of the bearing locking sleeve 24. The inner wall of the thrust ball bearing 27 is interference-fitted with the shaft of the lower gear 26. The thrust ball bearing 27 can bear a large axial force and realize the relative rotation of the upper and lower gears, thereby realizing the relative rotation of the first support plate 17 and the second support plate. The stepped hole of the bearing locking sleeve 24 is interference-fitted with the shaft of the upper gear 23, with no relative slippage. A locking pin 25 is also provided on the side of the bearing locking sleeve 24.

[0065] The background plate 06 includes a first background plate and a second background plate of the same specifications, respectively disposed at the same end of the first support plate 17 and the second support plate, such as... Figure 9 As shown, the first background panel includes a background support base 31 with vertical extensions at both ends. Horizontal slots 33 are provided on the inner sides of the two extensions of the background support base 31. A first colored striped background 30 is placed within the slots 33. A background rib 32 is provided on the back of the lower extension of the background support base 31.

[0066] The first lifting system and the second lifting system are located at the other end of the first support plate 17 and the second support plate, respectively. The first lifting system faces the first background plate, and the second lifting system faces the second background plate. The first image acquisition module and the second image acquisition module on the first lifting system and the second lifting system face the first colored striped background 30 and the second colored striped background, respectively.

[0067] The first groove 18 on the first support plate 17 is on the same side as the second groove on the second support plate, and the first rack 19 is on the same side as the second rack.

[0068] The fixed end bearing housing 9 is equipped with a set of angular contact bearings mounted in opposite directions, which can withstand forward and reverse loads and play a fixing role.

[0069] The ball screw 2 contacts the balls inside the screw nut seat 8 so as to convert the rotational motion of the ball screw 2 into the linear motion of the screw nut seat 8.

[0070] The combination of the two optical rods 7 and the ball screw 2 can improve the stability of the lifting system.

[0071] The support end bearing seat 6 is bolted to the inner wall of the second extension plate 303 of the lifting frame 3. The support end bearing seat 6 is an angular contact bearing used to provide vertical support force.

[0072] The lifting frame rib 5 bears the longitudinal strength and plays a supporting role.

[0073] The working principle of the lifting system 01: The servo motor 10 drives the ball screw 2 to rotate. The balls inside the screw nut seat 8 contact the ball screw 2. The balls move along the rotating thread track inside the screw nut seat 8, which drives the screw nut seat 8 to move linearly in the up and down direction of the ball screw 2. At the same time, the lifting platform 4, which cooperates with the ball nut seat 8 and the guide rod 7, slides up and down to complete the lifting motion.

[0074] The linear guide rail 15 is fixed to the image acquisition stage 11 by bolts, and the guide rail limiting clip 16 is locked on the outer end face of the linear guide rail 15 to prevent the slider 14 from derailing.

[0075] The image acquisition module 02 works as follows: The lifting system drives the image acquisition module 02 to move up and down to adjust to a suitable height; the manual sliding slider 14 enables the CCD industrial camera 12 to slide back and forth on the lifting platform 4, reducing the work of adjusting the focal length of the CCD industrial camera 12.

[0076] The bullseye wheel assembly 20 mounted on the bottom surface of the second support plate and the caster wheel assembly 21 mounted on the bottom surface of the first support plate 17 are used to support the support plate module 03 on the ground and enable it to slide in all directions at 360°.

[0077] Working principle of support module 03: This module is used to adjust the horizontal movement of the entire schlieren device in all directions and directly contacts the ground to provide support. It can also stretch or rotate the first support plate 17 and the second support plate to achieve the stretching and rotation of the entire schlieren device.

[0078] A candle 29 is provided on the candle hole of the first upper gear extension plate 2201. The candle 29 is lit so that the schlieren phenomenon can be observed in the area above the flame corresponding to the first colored stripe background 30 and the second colored stripe background.

[0079] The upper gear 23 and the lower gear 26 mesh with the first rack 19 and the second rack respectively, realizing the horizontal stretching of the first support plate 17 and the second support plate relative to the upper and lower gears. In this example, both the upper gear 23 and the lower gear 26 adopt a detachable gear and shaft form.

[0080] like Figure 8 As shown, the upper gear clamp 22 includes a vertical upper gear plate 2206. At the end of the upper gear plate 2206 away from the first upper gear extension plate 2201, there are a second upper gear extension plate 2202 and a third upper gear extension plate 2203 spaced apart and aligned with the first upper gear extension plate 2201. A groove portion of the upper gear clamp 22 is formed between the second upper gear extension plate 2202 and the third upper gear extension plate 2203. Both the second upper gear extension plate 2202 and the third upper gear extension plate 2203 are provided with... The first through hole 2205 passes through the shaft of the upper gear 23. The lower gear clamp 28 includes a lower gear plate 2802, and a first lower gear extension plate 2803 and a second lower gear extension plate 2804 perpendicular to both ends of the lower gear plate 2802. A U-shaped groove of the lower gear clamp is formed between the first lower gear extension plate 2803 and the second lower gear extension plate 2804. The first lower gear extension plate 2803 and the second lower gear extension plate 2804 are both provided with a second through hole 2805 for the shaft of the lower gear 26 to pass through.

[0081] The bearing locking sleeve 24 has milled flat surfaces on both sides, with a through hole drilled on one side and a threaded hole tapped on the other side, so that the through hole and the threaded hole are connected. The shaft of the lower gear 26 has a third through hole 2601 in the transverse direction. After the shaft of the lower gear 26 extends into the inner wall of the thrust ball bearing 27 and is interference-fitted, the locking pin 25 passes through the through hole of the bearing locking sleeve 24, the third through hole 2601 of the shaft of the lower gear 26 and the threaded hole of the bearing locking sleeve 24 in sequence. The locking pin 25 can realize the relative fixation of the upper and lower gears, thereby realizing the same distance stretching of the first support plate 17 and the second support plate.

[0082] The first lifting system, the first image acquisition module, the first support plate, and the first background plate form a schlieren device, and the second lifting system, the second image acquisition module, the second support plate, and the second background plate form another schlieren device.

[0083] Working principle of the rotation stretching module 04: When adjusting the relative angle of the two schlieren instruments, remove the locking pin 25, rotate the schlieren instrument, and after the adjustment is completed, insert the locking pin 25; when adjusting the distance between the image acquisition module 02 and the upper gear clamp 22, ensure that the locking pin 25 is in the inserted state, and then stretch the two schlieren instruments.

[0084] The background support base 31 has two side slots 33, one side of which is open and the other side is closed, to prevent the first and second colored striped backgrounds from sliding out.

[0085] Background panel 06 working principle: Used to place the first and second colored striped backgrounds to obtain a large field of view schlieren.

[0086] Working principle of the schlieren spectrometer: First, adjust the rotation and stretching module 04. If it is necessary to adjust the relative angle between the two schlieren spectrometers, pull out the locking pin 25 and rotate the support module 03. After completing the rotation, the locking pin 25 needs to be reinserted to prevent angle changes. Then, if it is necessary to adjust the relative distance between the image acquisition module 02 and the flow field to be measured, stretch the support module 03 back and forth. This can also achieve equal stretching of the first support plate 17 and the second support plate. Next, arrange the background plate 06 and insert the first and second colored striped backgrounds on the background support base 31. Light the candle 29 on the upper gear clamp 22 to form the flow field to be measured. Then, adjust the lifting system 01, start the servo motor 10, and drive the lifting platform 4 to move vertically so that the lens is aligned with the flow field area to be measured. Finally, adjust the image acquisition module 02 and move the camera base 13 so that the CCD industrial camera 12 can clearly image the data and perform image acquisition.

[0087] like Figure 10 As shown, a flow field displacement estimation method includes the aforementioned multi-functional binocular camera background orientation schlieren scanner, and the method includes the following steps:

[0088] 1) Before lighting candle 29, the angle and distance of CCD industrial camera 12 are fixed by image acquisition module 02, support module 03, and rotation stretching module 04. The CCD industrial camera of the first image acquisition module is the left camera, and the CCD industrial camera of the second image acquisition module is the right camera. The left and right cameras respectively capture the first and second colored stripe backgrounds of the first and second background boards as reference background images I1 and I2. After lighting candle 29, the first and second colored stripe backgrounds of the first and second background boards are captured again. The distorted image obtained by the left camera is I1. L The distorted image obtained by the right camera is I. R ;

[0089] 2) Set I1, I2, I L I R As input, a color image is converted to a grayscale image as follows: a pixel of the color image is represented as (R, G, B) to obtain a grayscale image, where R, G, and B represent the intensities of the red, green, and blue channels, respectively. The pixel value of the grayscale image is calculated using a weighted average formula: grayscale image pixel value = 0.299 * R + 0.587 * G + 0.114 * B;

[0090] 3) The left reference background image after being converted to grayscale and the left distorted image are used as a set of inputs, i.e., P1=(I1,I... L The right reference background image and the right distorted image are used as a set of inputs, i.e., P2=(I2,I... R The input objects for P1 and P2 are the optical flow algorithm framework;

[0091] 4) Optical Flow Algorithm: The main idea is that when an object moves in consecutive image frames, its pixel values ​​will change continuously. These changes can be obtained by performing pixel-by-pixel correlation matching analysis on two images. Typically, the input is two frames of images, and the output is an optical flow field representing the displacement vector of each pixel. The image pyramid-based optical flow algorithm is a technique for improving optical flow estimation. It performs multi-scale analysis of the image to handle motion of different scales and object sizes. It employs a "coarse-to-fine" multi-resolution scheme and warping techniques to handle large displacements in the flow field. Downsampling part: The optical flow algorithm uses a 6-layer image pyramid for downsampling, each layer being half the scale of the previous layer. Starting from the original image, a series of images with different resolutions are generated through multiple downsampling steps. Estimation part: Starting from the bottom of the pyramid, convolutional layers are applied to each pyramid layer to extract features. Beginning with low-resolution layers, a coarse optical flow is estimated first. Then, based on the estimation results of the previous layer, upsampling is used to generate a higher-resolution initial estimate for the current layer. Accumulated optical flow: Based on the estimation results at different scales, the optical flow is accumulated on the final high-resolution image to obtain the final optical flow field. When calculating the estimated optical flow, a loss function needs to be defined so that the model can automatically learn useful structures, features, or representations from unlabeled data. The loss function of the optical flow algorithm is based on minimizing an energy function and consists of a data term and a smoothing term. The data term satisfies the constant brightness and constant gradient assumptions, while the smoothing term is defined by constraints on divergence and curl to reduce the impact of outliers on motion estimation, thereby improving robustness to noise and illumination.

[0092] ,

[0093] in , It is a non-convex generalized Charbonnier penalty function, whose parameters are , , , Indicates image brightness. Indicates time, Denotes divergence, Indicates curl, , ;

[0094] 5) Input object pairs P1 and P2 into the optical flow algorithm framework of step 4) respectively to obtain the displacement estimate of the flow field at full resolution, as shown below. Figure 11 As shown, the left side is U1. Figure 11 As shown in (a), the right side is U2 as... Figure 11 As shown in (b);

[0095] 6) Large Field of View and 3D Reconstruction: First, depth estimation is performed using parallax, i.e., the difference in horizontal position between corresponding points in the left and right cameras. Then, stereo vision triangulation is used to calculate the 3D coordinates of the corresponding points. The origin of the camera coordinate system is at the optical center of the camera, and the optical axis of the camera is perpendicular to the image plane. For a pixel (x1, y1) in the left camera and a pixel (x2, y2) in the right camera, the corresponding 3D coordinates (X, Y, Z) of the left camera can be calculated using the following formula, and the same applies to the right camera:

[0096] ,

[0097] in, Indicates the pixel coordinates of the optical center of the left camera. Indicates the focal length of the left and right cameras. Indicates the baseline of the left and right cameras. It's the parallax of the left camera. It's about depth, and the final effect is like... Figure 12 As shown, where Figure 12 (a) is a diagram showing the high-precision large field-of-view estimation result. Figure 12 (b) is a three-dimensional reconstruction effect diagram.

[0098] In this example, since the first and second lifting systems, the first and second image acquisition modules, the first and second background boards have the same specifications, this example only describes the structure of the first lifting system, the first image acquisition module, and the first background board. If the structure of the second lifting system, the second image acquisition module, and the second background board appears in this example, it is equivalent to the structure of the first lifting system, the first image acquisition module, and the first background board.

Claims

1. A multifunctional binocular camera background directional schlieren scanner, characterized in that, It includes a support module, a lifting system located at both ends of the support module, and a background plate. A rotation and stretching module is located in the middle of the support module, and an image acquisition module is located on the lifting system. The lifting system includes a first lifting system and a second lifting system of identical specifications. The first lifting system includes a vertical lifting frame, which comprises a vertical plate and a first extension plate and a second extension plate perpendicular to both ends of the vertical plate. Two spaced-apart guide rods and a ball screw are provided between the first and second extension plates, with the ball screw located in the middle of the two guide rods. A servo motor with a coupling is located on the outward-facing surface of the first extension plate. The coupling passes through the first extension plate and connects to a fixed-end bearing seat on the inner wall of the first extension plate. A support-end bearing seat is located on the inner wall of the second extension plate, with both ends of the ball screw located on the fixed-end bearing seat and the support-end bearing seat, respectively. A lifting frame rib for supporting the lifting frame is provided on the vertical plate opposite to the second extension plate. The lifting frame also includes a lifting platform that moves through the two guide rods and the ball screw. A screw nut seat is provided on the lifting platform, through which the ball screw passes. The image acquisition module includes a first image acquisition module and a second image acquisition module of the same specifications, respectively mounted on a first lifting system and mounted on a second lifting system. The first image acquisition module includes an image acquisition platform mounted on the lifting platform. The image acquisition platform is provided with a linear guide rail facing the same direction as the first extension plate. A slidable slider is provided on the linear guide rail. From bottom to top, a camera mount and a CCD industrial camera are arranged on the upper surface of the slider. A guide rail limiting clamp is provided at the outward end of the linear guide rail. The support module includes a first support plate and a second support plate of the same specifications that are movably and cross-stacked. The first support plate has a first rectangular groove in the middle, one long side of the first rectangular groove has a first sliding groove of the same length as the long side, and the other long side has a first toothed rack of the same length as the long side. Caster wheel sets are provided on the bottom surfaces of both ends of the first support plate, and bullseye wheel sets are provided on the bottom surfaces of both ends of the second support plate. The rotary stretching module includes an upper gear clamp with a groove at one end, slidable on a first slide groove. The other end of the upper gear clamp has a first upper gear extension plate of the same length and direction as the groove. The first upper gear extension plate has a candle-shaped hole. An upper gear is located between the groove of the upper gear clamp and the first rack. A first rectangular slider is located on the back of the groove of the upper gear clamp, and the first rectangular slider can slide within the first slide groove. The rotary stretching module also includes a lower gear clamp with a U-shaped groove, slidable on a second slide groove of a second support plate. A lower gear is located between the U-shaped groove of the lower gear clamp and the second rack. A second rectangular slider is located on the back of the U-shaped groove of the lower gear clamp, and the second rectangular slider can slide within the second slide groove. A stepped bearing locking sleeve is provided between the upper and lower gears. A thrust ball bearing is located near the interior of the lower gear in the bearing locking sleeve. The outer wall of the thrust ball bearing is interference-fitted with the inner wall of the lower end of the bearing locking sleeve. The inner wall of the thrust ball bearing is interference-fitted with the shaft of the lower gear. The stepped part of the bearing locking sleeve has a hole that is interference-fitted with the shaft of the upper gear. A locking pin is also provided on the side of the bearing locking sleeve. The background panel includes a first background panel and a second background panel of the same specifications, respectively disposed at the same end of the first support panel and the second support panel. The first background panel includes a background support base with vertical edges at both ends. The inner sides of the two edges of the background support base are provided with horizontal slots, and the slots are provided with a first colored striped background. The back of the lower edge of the background support base is provided with a background rib. The first lifting system and the second lifting system are located at the other end of the first support plate and the second support plate, respectively, and the first image acquisition module and the second image acquisition module on the first lifting system and the second lifting system face the first colored stripe background and the second colored stripe background, respectively.

2. The multifunctional binocular camera background directional schlieren scanner according to claim 1, characterized in that, The fixed-end bearing housing contains a set of angular contact bearings mounted in opposite directions.

3. The multifunctional binocular camera background directional schlieren scanner according to claim 1, characterized in that, The ball screw contacts the balls inside the screw nut seat.

4. The multifunctional binocular camera background orientation schlieren scanner according to claim 1, characterized in that, The upper gear clamp includes a vertical upper gear plate. At the end of the upper gear plate away from the first upper gear extension plate, there are a second upper gear extension plate and a third upper gear extension plate that are in the same direction as the first upper gear extension plate. A groove portion of the upper gear clamp is formed between the second upper gear extension plate and the third upper gear extension plate. Both the second upper gear extension plate and the third upper gear extension plate are provided with a first through hole for the shaft of the upper gear to pass through. The lower gear clamp includes a lower gear plate, and a first lower gear extension plate and a second lower gear extension plate that are perpendicular to both ends of the lower gear plate. A U-shaped groove portion of the lower gear clamp is formed between the first lower gear extension plate and the second lower gear extension plate. Both the first lower gear extension plate and the second lower gear extension plate are provided with a second through hole for the shaft of the lower gear to pass through.

5. The multifunctional binocular camera background directional schlieren scanner according to claim 1, characterized in that, The bearing locking sleeve has milled flat surfaces on both sides, with a through hole drilled on one side and a threaded hole tapped on the other side, so that the through hole and the threaded hole are connected. The shaft of the lower gear is provided with a third through hole in the transverse direction. After the shaft of the lower gear extends into the inner wall of the thrust ball bearing and is interference-fitted, the locking pin passes through the through hole of the bearing locking sleeve, the third through hole of the shaft of the lower gear and the threaded hole of the bearing locking sleeve in sequence.

6. The multifunctional binocular camera background directional schlieren scanner according to claim 1, characterized in that, The background support base has two side slots, one side of which is open and the other side is closed.

Images