A 3D reconstruction system and method for underwater concrete defects

Abstract

The present invention discloses a 3D reconstruction system for underwater concrete defects and a reconstruction method thereof, belonging to the technical field of underwater laser image shooting. The underwater concrete defect 3D reconstruction system comprises a water tank, a stepper motor scanning system, an underwater image acquisition device, a system parameter calibration system and a 3D laser point cloud reconstruction system. The stepper motor scanning system drives the underwater image acquisition device to move horizontally back and forth linearly inside the water tank. The underwater image acquisition device is used to capture images of underwater concrete defects with strong characteristic lasers. The system parameter calibration system is used to calibrate the parameters of the underwater image acquisition device. The 3D laser point cloud reconstruction system realizes 3D reconstruction of underwater concrete defects based on images of underwater concrete defects with strong characteristic lasers, thereby greatly improving the detection efficiency and detection accuracy of underwater concrete defects and solving the problem that existing underwater camera equipment limits the effect of underwater 3D reconstruction, resulting in low accuracy of underwater concrete defects.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater laser image shooting, and in particular relates to an underwater concrete defect three-dimensional reconstruction system and a reconstruction method thereof. Background Art

[0002] Infrastructure such as water conservancy projects, bridges, ports, and water tunnels bear the crucial responsibility for the development and utilization of water resources and the safety of life and property. However, these underwater concrete structures have long been susceptible to various defects, such as cracks, scour, wear, and exposed rebar, when exposed to natural disasters like earthquakes, geological disasters, and floods, posing a serious threat to the safe operation of the projects. Therefore, timely and accurate defect detection and hidden danger investigation are extremely urgent. However, currently, no image acquisition device for underwater 3D reconstruction has emerged on the market that can fully utilize the fusion of binocular camera and line laser technology. Existing underwater camera equipment typically only provides either binocular camera or line laser functionality, but cannot achieve the fusion of both, limiting the effectiveness and application scope of underwater 3D reconstruction. Summary of the Invention

[0003] The present invention aims to provide a three-dimensional reconstruction system and method for underwater concrete defects, which solves the problem that existing underwater camera equipment limits the effect of underwater three-dimensional reconstruction and leads to low accuracy of underwater concrete defects.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0005] Provided is an underwater concrete defect 3D reconstruction system, which includes a water tank, a stepper motor scanning system, an underwater image acquisition device, a system parameter calibration system, and a 3D laser point cloud reconstruction system;

[0006] The water tank has an opening at the top and a closed bottom. A shooting window is provided on the bottom of the water tank. The underwater image acquisition device is provided on a stepper motor scanning system. The underwater image acquisition device is located inside the water tank and faces the shooting window. The stepper motor scanning system drives the underwater image acquisition device to move horizontally and linearly inside the water tank.

[0007] The underwater image acquisition device includes two cameras and a laser transmitter, and is used to capture underwater concrete defect images with a strong characteristic laser;

[0008] The system parameter calibration system is used to calibrate the parameters of underwater image acquisition equipment;

[0009] The 3D laser point cloud reconstruction system is used to convert underwater concrete defect images with strong characteristic lasers into 3D point cloud data, and color the 3D point cloud data through a color camera to achieve 3D reconstruction.

[0010] The basic principle of the underwater concrete defect three-dimensional reconstruction system in the present invention is: a stepper motor scanning system drives the underwater image acquisition device to move horizontally back and forth in a straight line inside the water tank, which can obtain a wider range of shooting angles, and the underwater image acquisition device captures underwater concrete defect images with strong characteristic lasers, while the system parameter calibration system and the three-dimensional laser point cloud reconstruction system generate three-dimensional point cloud data based on the underwater concrete defect images with strong characteristic lasers, and color the three-dimensional point cloud data to realize three-dimensional reconstruction of underwater concrete defects, greatly improving the detection efficiency and detection accuracy of underwater concrete defects, and solving the problem that existing underwater camera equipment limits the effect of underwater three-dimensional reconstruction, resulting in low accuracy of underwater concrete defects.

[0011] Furthermore, as a specific setting method of the stepper motor scanning system, the stepper motor scanning system includes a mounting bracket arranged on the top of the water tank, a screw is rotatably arranged in the mounting bracket, and a slider is threadedly connected to the screw; a stepper motor is arranged on one side of the mounting bracket, and the output end of the stepper motor is fixedly connected to one end of the screw through a coupling; a mounting bracket is vertically arranged on the slider, the top of the mounting bracket is fixedly connected to the slider, and the bottom of the mounting bracket is located at the bottom of the water tank; the underwater image acquisition device is fixedly connected to the bottom of the mounting bracket.

[0012] The process of the stepper motor scanning system driving the underwater image acquisition device to move horizontally back and forth linearly inside the water tank is as follows: by starting the stepper motor to drive the screw to rotate, the rotating screw drives the slider to move back and forth linearly along the length direction of the screw, thereby driving the mounting bracket fixedly connected to the slider and the underwater image acquisition device fixedly connected to the mounting bracket to move horizontally back and forth linearly inside the water tank, so that the underwater image acquisition device has a wider shooting range, enabling the underwater image acquisition device to completely scan the target and obtain images corresponding to different positions.

[0013] Furthermore, as a specific setting mode of the underwater image acquisition device, the underwater image acquisition device includes a binocular cabin and an aviation plug, the binocular cabin is fixedly connected to the bottom of the mounting bracket; the binocular cabin includes an intermediate cabin, two camera cabins are obliquely arranged on both sides of the intermediate cabin, and the two camera cabins are symmetrically arranged; a camera front view glass is provided at the front end of each camera cabin, a camera is provided in each camera cabin, and a lens is provided at the front end of each camera with a shooting direction toward the camera front view glass;

[0014] A laser front-view glass is provided in the middle of the front of the middle cabin, and a laser emitter is provided inside the middle cabin to emit laser light in the direction of the laser front-view glass; the angle between the emission direction of the laser emitter and the shooting direction of each camera is an acute angle;

[0015] The aviation plug is sealed and connected to the bulkhead of the middle cabin. The aviation plug inside the middle cabin is electrically connected to the laser transmitter and the camera. The aviation plug outside the middle cabin is electrically connected to the power supply, the system parameter calibration system, and the 3D laser point cloud reconstruction system.

[0016] The illumination directions of the two cameras and one laser transmitter are all toward the shooting window.

[0017] In the above technical solution, by arranging two camera cabins on both sides of the middle cabin, arranging a laser transmitter in the middle cabin and arranging a camera in the camera cabin, the binocular camera and line laser technology are integrated into a set of equipment. The binocular camera integrates the line laser to realize the underwater image shooting function and realize high-precision and high-stability underwater three-dimensional reconstruction, thereby meeting the needs of marine engineering, marine science and other fields for underwater three-dimensional data acquisition, and solving the problem that existing underwater camera equipment cannot realize the binocular camera and line laser functions at the same time, thereby limiting the effect and application scope of underwater three-dimensional reconstruction.

[0018] Furthermore, the middle cabin is connected to the two camera cabins, and the back of the middle cabin is sealed and detachably provided with a rear cover plate, and the aviation plug is sealed and connected to the rear cover plate; the rear end of each camera cabin is sealed and detachably provided with a rear end sealing cover; the setting of the rear cover plate and the rear end sealing cover can facilitate the assembly and subsequent disassembly and maintenance of the laser emitter and camera.

[0019] The camera front view glass and the laser front view glass are sealed and connected to the front end of the camera cabin and the front face of the middle cabin respectively through mounting parts. The mounting parts are in a circular ring structure, and a plurality of bolt connectors are evenly arranged on the mounting parts at circumferential intervals with their own axis as the center.

[0020] Furthermore, each camera cabin is provided with a camera fixing block, each camera fixing block is a hollow square column structure with an opening at one end and a sealed end at the other end. The end with the opening of the camera fixing block is arranged toward the camera front glass, and the other end of the camera fixing block is fixedly connected to the inner wall of the rear end sealing cover; the camera is fixedly arranged inside the camera fixing block;

[0021] The camera and the camera fixing block are movably matched. A long hole is provided on the side wall of the camera fixing block. The long hole is arranged along the length direction of the camera cabin. A bolt locking part for locking the camera is provided in the long hole.

[0022] In the above technical solution, the position of the camera in the camera fixing block can be adjusted, the distance between the lens on the camera and the camera front glass can be adjusted, and after the distance is adjusted, the current position of the camera and lens can be fixed by tightening the bolt locking member to adapt to the use of different models of cameras and improve the flexibility of use of the entire underwater three-dimensional reconstruction image acquisition equipment.

[0023] Furthermore, a laser fixing block for fixing the laser transmitter is provided inside the intermediate cabin, and the rear end of the laser fixing block is sealed and connected to the rear cover plate, thereby improving the stability of laser installation and laser use; waterproof strips are provided on the connecting end surfaces of the rear cover plate and the rear end sealing cover, and the waterproof strips are used for waterproof treatment to prevent water from entering the interior of the device and causing malfunctions when the underwater image acquisition device is shooting underwater.

[0024] The present invention also provides a reconstruction method of an underwater concrete defect three-dimensional reconstruction system, which comprises:

[0025] Step 1: Use underwater image acquisition equipment to obtain multiple underwater concrete defect images with different poses and strong characteristic lasers, and use Gaussian filtering to eliminate noise from the multiple images. Then, based on the air and underwater light refraction model, restore the underwater image field coordinates of the multiple images to obtain the field coordinates of the multiple images in air;

[0026] Step 2: System parameter calibration: The system uses Zhang's calibration method to calibrate the internal reference table of the two cameras in the underwater image acquisition device;

[0027] Step 3: extract the two-dimensional coordinates of the laser stripes from multiple underwater concrete defect images with different postures and strong characteristic lasers;

[0028] Step 4: System parameter calibration: The system captures a checkerboard calibration plate without laser stripes and extracts the intersections of the laser lines and the lines connecting the checkerboard corners from the image of the checkerboard calibration plate with laser. The world coordinates of the intersections are obtained by substituting the cross ratio invariance into the extrinsic parameter matrix, and these intersections are fitted to obtain the laser plane equation.

[0029] Step 5: The 3D laser point cloud reconstruction system incorporates the laser stripes into the laser plane equation and, based on the field of view coordinates of multiple images in the air, selects the underwater concrete defect images with strong characteristic lasers from the left and right cameras for mirror-symmetric epipolar line matching to obtain 3D point cloud data.

[0030] Step 6: Use a color camera to extract the color value corresponding to the laser line pixel coordinates and color the 3D point cloud data to achieve 3D reconstruction of underwater concrete defects.

[0031] The beneficial effects of the present invention are as follows: a three-dimensional reconstruction system and a reconstruction method of underwater concrete defects in the present invention, an underwater image acquisition device based on the binocular imaging principle and the principle of adding strong features to objects with laser lines, obtains underwater concrete defect images with strong characteristic lasers, and converts the underwater concrete defect images with strong characteristic lasers into three-dimensional point cloud data through a system parameter calibration system and a three-dimensional laser point cloud reconstruction system, and colors the three-dimensional point cloud data through a color camera to achieve three-dimensional reconstruction, which greatly improves the detection efficiency and detection accuracy of underwater concrete defects, and solves the problem that existing underwater camera equipment limits the effect of underwater three-dimensional reconstruction, resulting in low accuracy of underwater concrete defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the structure of an underwater concrete defect 3D reconstruction system.

[0033] Figure 2 This is a schematic diagram of the structure of the stepper motor scanning system connected and fixed to the underwater image acquisition equipment.

[0034] Figure 3 Schematic diagram of the structure of underwater image acquisition equipment Figure 1 .

[0035] Figure 4 Schematic diagram of the structure of underwater image acquisition equipment Figure 2 .

[0036] Figure 5 Flowchart of the reconstruction method of the underwater concrete defect 3D reconstruction system.

[0037] Among them, 1. Water tank; 2. Stepper motor scanning system; 201. Mounting frame; 202. Screw; 203. Slider; 204. Stepper motor; 205. Mounting bracket; 3. Underwater image acquisition equipment; 301. Camera; 302. Laser transmitter; 303. Binocular cabin; 3031. Intermediate cabin; 3032. Camera cabin; 304. Aviation plug; 305. Lens; 306. Laser front view glass; 307. Rear cover; 308. Rear sealing cover; 309. Mounting parts; 310. Camera fixing block; 311. Long hole; 312. Laser fixing block; 313. Camera front view glass. DETAILED DESCRIPTION

[0038] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0039] The present invention provides an underwater concrete defect three-dimensional reconstruction system, which includes a water tank 1, a stepper motor scanning system 2, an underwater image acquisition device 3, a system parameter calibration system and a three-dimensional laser point cloud reconstruction system;

[0040] like Figure 1 As shown, the top of the water tank 1 has an opening and the bottom is a closed structure, and a shooting window is provided on the bottom of the water tank 1; the underwater image acquisition device 3 is provided on the stepper motor scanning system 2, and the underwater image acquisition device 3 is located inside the water tank 1 and the shooting direction is toward the shooting window. The stepper motor scanning system 2 drives the underwater image acquisition device 3 to move horizontally back and forth linearly inside the water tank 1.

[0041] The underwater image acquisition device 3 includes two cameras 301 and a laser emitter 302. The underwater image acquisition device 3 is used to capture underwater concrete defect images with strong characteristic lasers. The system parameter calibration system is used to calibrate the parameters of the underwater image acquisition device 3. The three-dimensional laser point cloud reconstruction system is used to convert underwater concrete defect images with strong characteristic lasers into three-dimensional point cloud data, and color the three-dimensional point cloud data through the color camera 301 to achieve three-dimensional reconstruction.

[0042] The basic principle of the underwater concrete defect three-dimensional reconstruction system in the present invention is: the stepper motor scanning system 2 drives the underwater image acquisition device 3 to move horizontally back and forth in a straight line inside the water tank 1, which can obtain a wider range of shooting angles, and the underwater image acquisition device 3 captures underwater concrete defect images with strong characteristic lasers, and the system parameter calibration system and the three-dimensional laser point cloud reconstruction system generate three-dimensional point cloud data based on the underwater concrete defect images with strong characteristic lasers, and color the three-dimensional point cloud data to achieve three-dimensional reconstruction of underwater concrete defects, greatly improving the detection efficiency and detection accuracy of underwater concrete defects, and solving the problem that existing underwater camera equipment limits the effect of underwater three-dimensional reconstruction, resulting in low accuracy of underwater concrete defects.

[0043] Specifically, if Figure 1 and Figure 2 As shown, as a specific setting method of the stepper motor scanning system 2, the stepper motor scanning system 2 includes a mounting frame 201 arranged on the top of the water tank 1, a screw rod 202 is rotatably arranged in the mounting frame 201, and a slider 203 is threadedly connected to the screw rod 202; a stepper motor 204 is arranged on one side of the mounting frame 201, and the output end of the stepper motor 204 is fixedly connected to one end of the screw rod 202 through a coupling; a mounting bracket 205 is vertically arranged on the slider 203, the top of the mounting bracket 205 is fixedly connected to the slider 203, and the bottom of the mounting bracket 205 is located at the bottom of the water tank 1; the underwater image acquisition device 3 is fixedly connected to the bottom of the mounting bracket 205.

[0044] The process of the stepper motor scanning system 2 driving the underwater image acquisition device 3 to move horizontally back and forth linearly inside the water tank 1 is as follows: by starting the stepper motor 204 to drive the screw rod 202 to rotate, the rotating screw rod 202 drives the slider 203 to move back and forth linearly along the length direction of the screw rod 202, thereby driving the mounting bracket 205 fixedly connected to the slider 203 and the underwater image acquisition device 3 fixedly connected to the mounting bracket 205 to move horizontally back and forth linearly inside the water tank 1, so that the underwater image acquisition device 3 has a wider shooting range, so that the underwater image acquisition device 3 can completely scan the target and obtain images corresponding to different positions.

[0045] like Figures 1 to 4 As shown, as a specific setting method of the underwater image acquisition device 3, the underwater image acquisition device 3 includes a binocular cabin 303 and an aviation plug 304, and the binocular cabin 303 is fixedly connected to the bottom of the mounting bracket 205; the binocular cabin 303 includes an intermediate cabin 3031, and two camera cabins 3032 are obliquely arranged on both sides of the intermediate cabin 3031, and the two camera cabins 3032 are symmetrically arranged; a camera front view glass 313 is provided at the front end of each camera cabin 3032, a camera 301 is provided in each camera cabin 3032, and a lens 305 is provided at the front end of each camera 301 with a shooting direction toward the camera front view glass 313.

[0046] A laser front-view glass 306 is provided in the middle of the front of the middle cabin 3031, and a laser emitter 302 is provided inside the middle cabin 3031 to emit laser lines toward the laser front-view glass 306; the angle between the emission direction of the laser emitter 302 and the shooting direction of each camera 301 is an acute angle.

[0047] The aviation plug 304 is sealed and connected to the wall of the intermediate cabin 3031. The aviation plug 304 inside the intermediate cabin 3031 is electrically connected to the laser emitter 302 and the camera 301. The aviation plug 304 outside the intermediate cabin 3031 is electrically connected to the power supply, system parameter calibration system and three-dimensional laser point cloud reconstruction system.

[0048] The illumination directions of the two cameras 301 and the one laser emitter 302 are all toward the shooting window.

[0049] In the above technical solution, by arranging two camera cabins 3032 on both sides of the middle cabin 3031, arranging a laser emitter 302 in the middle cabin 3031 and arranging a camera 301 in the camera cabin 3032, the binocular camera 301 and the line laser technology are integrated into a set of equipment. The binocular camera 301 integrates the line laser to realize the underwater image shooting function and realize high-precision and high-stability underwater three-dimensional reconstruction, thereby meeting the needs of marine engineering, marine science and other fields for underwater three-dimensional data acquisition, and solving the problem that the existing underwater camera 301 equipment cannot realize the binocular camera 301 and line laser functions at the same time, thereby limiting the effect and application scope of underwater three-dimensional reconstruction.

[0050] Preferably, but not limited to, the middle cabin 3031 is connected to the two camera cabins 3032, the back of the middle cabin 3031 is sealed and detachably provided with a rear cover 307, and the aviation plug 304 is sealed and connected to the rear cover 307; the rear end of each camera cabin 3032 is sealed and detachably provided with a rear end sealing cover 308; the setting of the rear cover 307 and the rear end sealing cover 308 can facilitate the assembly and subsequent disassembly and maintenance of the laser emitter 302 and the camera 301.

[0051] The camera front view glass 313 and the laser front view glass 306 are sealedly connected to the front end of the camera cabin 3032 and the front face of the middle cabin 3031 respectively through the mounting parts 309. The mounting parts 309 are in a circular ring structure, and a plurality of bolt connectors are evenly arranged on the mounting parts 309 at circumferential intervals with their own axis as the center.

[0052] Each camera cabin 3032 is provided with a camera fixing block 310. Each camera fixing block 310 has a hollow square column structure with an opening at one end and a sealed end at the other end. The open end of the camera fixing block 310 is arranged toward the camera front view glass 313, and the other end of the camera fixing block 310 is fixedly connected to the inner wall of the rear end sealing cover 308; the camera 301 is fixedly set inside the camera fixing block 310.

[0053] The camera 301 is movably fitted with the camera fixing block 310 . A long hole 311 is provided on the side wall of the camera fixing block 310 . The long hole 311 is arranged along the length direction of the camera cabin 3032 . A bolt locking member for locking the camera 301 is provided in the long hole 311 .

[0054] In the above technical solution, the position of the camera 301 in the camera fixing block 310 can be adjusted, the distance between the lens 305 on the camera 301 and the camera front view glass 313 can be adjusted, and after the distance is adjusted, the current position of the camera 301 and the lens 305 can be fixed by tightening the bolt locking member to adapt to the use of different models of cameras 301, thereby improving the flexibility of use of the entire underwater three-dimensional reconstruction image acquisition equipment.

[0055] Specifically, a laser fixing block 312 for fixing the laser emitter 302 is provided inside the middle cabin 3031. The rear end of the laser fixing block 312 is sealed and connected to the rear cover 307, which improves the stability of laser installation and laser use; waterproof strips are provided on the connecting end surfaces of the rear cover 307 and the rear sealing cover 308. The waterproof strips are used for waterproof treatment to prevent water from entering the interior of the device and causing malfunctions when the underwater image acquisition device 3 is shooting underwater.

[0056] like Figure 5 As shown, the present invention also provides a reconstruction method of an underwater concrete defect 3D reconstruction system, which includes:

[0057] Step 1: Acquire multiple underwater concrete defect images with strong characteristic laser light at different positions using underwater image acquisition equipment 3, eliminate noise from the multiple images using Gaussian filtering, and then restore the underwater image field coordinates of the multiple images based on the air and underwater light refraction model to obtain the field coordinates of the multiple images in air;

[0058] Step 2: System parameter calibration: The system uses Zhang's calibration method to calibrate the internal reference table of the two cameras in the underwater image acquisition device;

[0059] Step 3: extract the two-dimensional coordinates of the laser stripes from multiple underwater concrete defect images with different postures and strong characteristic lasers;

[0060] Step 4: System parameter calibration: The system captures a checkerboard calibration plate without laser stripes and extracts the intersections of the laser lines and the lines connecting the checkerboard corners from the image of the checkerboard calibration plate with laser. The world coordinates of the intersections are obtained by substituting the cross ratio invariance into the extrinsic parameter matrix, and these intersections are fitted to obtain the laser plane equation.

[0061] Step 5: The 3D laser point cloud reconstruction system substitutes the laser stripes into the laser plane equation and selects the underwater concrete defect images with strong characteristic lasers from the left and right cameras 301 according to the field of view coordinates in the air of the multiple images, performs mirror-symmetric epipolar line matching, and obtains 3D point cloud data.

[0062] Step 6: Use a color camera to extract the color values ​​corresponding to the laser line pixel coordinates and colorize the 3D point cloud data to achieve 3D reconstruction of underwater concrete defects. CloudCompare software can be used for modeling.

[0063] Furthermore, in step 1, the calculation formula for obtaining the field of view coordinates of multiple images in air is:

[0064]

[0065] in, is the field of view coordinate of a point in the image in air; is the underwater field coordinate of a certain point in the image; is the affine transformation matrix, The 8 position parameters of the affine transformation matrix.

[0066] In summary, the present invention provides a three-dimensional reconstruction system and reconstruction method for underwater concrete defects. The underwater image acquisition device 3 obtains underwater concrete defect images with strong characteristic lasers based on the binocular imaging principle and the principle of adding strong features to objects using laser lines. The underwater concrete defect images with strong characteristic lasers are converted into three-dimensional point cloud data through the system parameter calibration system and the three-dimensional laser point cloud reconstruction system, and the three-dimensional point cloud data are colored by the color camera 301 to achieve three-dimensional reconstruction, which greatly improves the detection efficiency and detection accuracy of underwater concrete defects and solves the problem that the existing underwater camera equipment limits the effect of underwater three-dimensional reconstruction, resulting in low accuracy of underwater concrete defects.

Claims

1. A 3D reconstruction system for underwater concrete defects, characterized by: It includes a water tank, a stepper motor scanning system, underwater image acquisition equipment, a system parameter calibration system and a 3D laser point cloud reconstruction system; The water tank has an opening at the top and a closed bottom, and a shooting window is provided on the bottom of the water tank; the underwater image acquisition device is provided on the stepper motor scanning system, and the underwater image acquisition device is located inside the water tank with the shooting direction facing the shooting window, and the stepper motor scanning system drives the underwater image acquisition device to move horizontally and reciprocatingly in a linear manner inside the water tank; The underwater image acquisition device includes two cameras and a laser transmitter, and is used to capture underwater concrete defect images with a strong characteristic laser; The system parameter calibration system is used to calibrate the parameters of the underwater image acquisition equipment; The 3D laser point cloud reconstruction system is used to convert underwater concrete defect images with strong characteristic lasers into 3D point cloud data, and color the 3D point cloud data through a color camera to achieve 3D reconstruction; The underwater image acquisition device includes a binocular cabin and an aviation plug, wherein the binocular cabin is fixedly connected to the bottom of the mounting bracket; the binocular cabin includes an intermediate cabin, and two camera cabins are obliquely arranged on both sides of the intermediate cabin, and the two camera cabins are symmetrically arranged; a camera front view glass is provided at the front end of each camera cabin, and a camera is provided in each camera cabin, and a lens is provided at the front end of each camera with a shooting direction facing the camera front view glass; A laser front-view glass is provided in the middle of the front of the middle cabin, and a laser emitter is provided inside the middle cabin for emitting laser lines in the direction of the laser front-view glass; the angle between the emission direction of the laser emitter and the shooting direction of each camera is an acute angle; The aviation plug is sealed and connected to the wall of the intermediate cabin. The aviation plug inside the intermediate cabin is electrically connected to the laser emitter and the camera. The aviation plug outside the intermediate cabin is electrically connected to the power supply, the system parameter calibration system, and the three-dimensional laser point cloud reconstruction system. The irradiation directions of the two cameras and the one laser transmitter are all toward the shooting window.

2. The underwater concrete defect 3D reconstruction system according to claim 1, characterized in that: The stepper motor scanning system includes a mounting bracket arranged on the top of the water tank, a screw is rotatably arranged in the mounting bracket, and a slider is threadedly connected to the screw; a stepper motor is arranged on one side of the mounting bracket, and the output end of the stepper motor is fixedly connected to one end of the screw through a coupling; a mounting bracket is vertically arranged on the slider, the top of the mounting bracket is fixedly connected to the slider, and the bottom of the mounting bracket is located at the bottom of the water tank; the underwater image acquisition device is fixedly connected to the bottom of the mounting bracket.

3. The underwater concrete defect 3D reconstruction system according to claim 1, characterized in that: The middle cabin is connected to the two camera cabins, and the back of the middle cabin is sealed and detachably provided with a rear cover, and the aviation plug is sealed and connected to the rear cover; the rear end of each camera cabin is sealed and detachably provided with a rear end sealing cover; the camera front view glass and the laser front view glass are respectively sealed and connected to the front end of the camera cabin and the front face of the middle cabin through mounting parts, and the mounting parts are in a circular ring structure, and a plurality of bolt connectors are evenly arranged on the mounting parts at circumferential intervals with their own axis as the center.

4. The underwater concrete defect 3D reconstruction system according to claim 3, characterized in that: Each of the camera cabins is provided with a camera fixing block, each of which is a hollow square column structure with an opening at one end and a sealed end at the other end. The end of the camera fixing block with the opening is arranged toward the camera front glass, and the other end of the camera fixing block is fixedly connected to the inner wall of the rear end sealing cover; the camera is fixedly arranged inside the camera fixing block; The camera is movably matched with the camera fixing block. A long hole is provided on the side wall of the camera fixing block. The long hole is arranged along the length direction of the camera cabin. A bolt locking member for locking the camera is provided in the long hole.

5. The underwater concrete defect 3D reconstruction system according to claim 4, characterized in that: A laser fixing block for fixing the laser emitter is provided inside the intermediate cabin, and the rear end of the laser fixing block is sealed with the rear cover plate; waterproof strips are provided on the connecting end surfaces of the rear cover plate and the rear end sealing cover.

6. A reconstruction method based on the underwater concrete defect 3D reconstruction system according to any one of claims 1 to 5, characterized in that: include: Step 1: Use underwater image acquisition equipment to obtain multiple underwater concrete defect images with different poses and strong characteristic lasers, and use Gaussian filtering to eliminate noise from the multiple images. Then, based on the air and underwater light refraction model, restore the underwater image field coordinates of the multiple images to obtain the field coordinates of the multiple images in air; Step 2: System parameter calibration: The system uses Zhang's calibration method to calibrate the internal reference table of the two cameras in the underwater image acquisition device; Step 3: extract the two-dimensional coordinates of the laser stripes from multiple underwater concrete defect images with different postures and strong characteristic lasers; Step 4: System parameter calibration: The system captures a checkerboard calibration plate without laser stripes and extracts the intersections of the laser lines and the lines connecting the checkerboard corners from the image of the checkerboard calibration plate with laser. The world coordinates of the intersections are obtained by substituting the cross ratio invariance into the extrinsic parameter matrix, and these intersections are fitted to obtain the laser plane equation. Step 5: The 3D laser point cloud reconstruction system incorporates the laser stripes into the laser plane equation and, based on the field of view coordinates of multiple images in the air, selects the underwater concrete defect images with strong characteristic lasers from the left and right cameras for mirror-symmetric epipolar line matching to obtain 3D point cloud data. Step 6: Use a color camera to extract the color value corresponding to the laser line pixel coordinates and color the 3D point cloud data to achieve 3D reconstruction of underwater concrete defects.

Images