Underwater plane dimension measuring system and method based on multiple laser points

Abstract

The invention relates to the technical field of nuclear power defect identification, in particular to an underwater plane size measuring system and method based on multiple laser points, the system comprises an underwater image acquisition module and an overwater control module, the underwater image acquisition module comprises a pan-tilt camera, four lasers, four laser sealing shells and a laser mounting plate, a camera mounting hole is formed in the center of the laser mounting plate, and laser mounting holes are respectively formed in four corners of the laser mounting plate; a pan-tilt camera is mounted at a camera mounting hole of the laser mounting plate, and four lasers are fixedly mounted in four laser mounting holes of the laser mounting plate through laser sealing shells respectively; and the overwater control module is connected with the pan-tilt camera and the laser. The system can effectively solve the problem of measurement of the plane defect size in a scene lacking markers, and is beneficial to maintenance of a nuclear power plant pool, prevention of coolant leakage and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power defect identification, and in particular to an underwater plane dimension measurement system and a measurement method based on multiple laser points. Background Art

[0002] Reactor pools and spent fuel pools are crucial components of nuclear power plants, housing coolant, spent fuel, and other components. The integrity of the pool walls is directly linked to the structural safety of the entire plant. Over time, the pool walls may develop defects such as cracks, scratches, wear, and corrosion. These defects can compromise the seals of the pools, leading to coolant leaks and reduced reactor cooling, ultimately impacting the plant's normal operation. Regular defect measurement allows for timely remedial measures, ensuring the pools can function reliably throughout the plant's operating life and ensuring stable operation.

[0003] Currently, common defect measurement methods include 3D scanning systems, underwater measurement systems based on binocular vision, and measurement systems based on monocular vision. Using a 3D scanning system to scan defects can obtain the 3D shape of the defect. However, for tank wall defects such as cracks, scratches, and abrasion, which are small in depth, 3D scanning methods are difficult to identify. Underwater measurement systems based on binocular vision can also identify the 3D shape of defects, but the binocular vision measurement system is more complex. Furthermore, the imaging model formed by the refraction of light through multiple media such as water, glass, and air is complex, resulting in low measurement accuracy. Monocular vision-based measurement systems use a camera to capture an image of the defect and extract the number of pixels occupied by the defect. Based on the actual physical size of the marker in the image and the number of pixels occupied, the pixel scale is determined, thereby determining the physical size of the defect. This method requires the presence of markers of known size in the image. However, the smooth and sparsely featured surfaces of nuclear power plant tanks make monocular vision-based measurement methods unsuitable for tank wall defect measurement. Summary of the Invention

[0004] The present invention provides an underwater plane dimension measurement system and a measurement method based on multiple laser points, which are used to solve the problem of lack of nuclear power plant pool wall defect measurement tools in the prior art.

[0005] The technical solutions of the present invention are as follows:

[0006] The present invention discloses an underwater plane dimension measurement system based on multiple laser points. The system comprises an underwater image acquisition module and an above-water control module. The underwater image acquisition module comprises a pan-tilt camera, four lasers, four laser sealing shells and a laser mounting plate. A camera mounting hole is provided at the center of the laser mounting plate, and laser mounting holes are respectively provided at the four corners of the laser mounting plate. The pan-tilt camera is installed at the camera mounting hole of the laser mounting plate, and the four lasers are respectively fixedly mounted in the four laser mounting holes of the laser mounting plate through the laser sealing shells. The above-water control module is connected to the pan-tilt camera and the lasers.

[0007] In some embodiments, the above-water control module includes a control computer, cables, and control and measurement software. The control computer controls the pan-tilt camera and laser through the cables, and the control and measurement software is integrated into the control computer.

[0008] In some embodiments, the control and measurement software includes a gimbal motion control module, a camera control module, a laser control module, a calibration module and a measurement module. The gimbal motion control module controls the gimbal motion of the gimbal camera, the camera control module adjusts the camera parameters of the gimbal camera and controls the camera to take pictures, the laser control module controls the laser switch and adjusts the laser brightness, the calibration module calibrates the positional relationship between the four lasers before measurement, and the measurement module calculates the plane defect size based on the image captured by the gimbal camera.

[0009] The present invention proposes an underwater plane dimension measurement method based on multiple laser points, which includes:

[0010] Step 1: Calibrate the measurement system;

[0011] Step 1.1: Install the measurement system on the calibration device;

[0012] Step 1.2: Slide the checkerboard calibration plate to the initial calibration position of the unified calibration device;

[0013] Step 1.3: Slide the checkerboard calibration plate a certain distance away from the laser;

[0014] Step 1.4: Use the control and measurement software on the computer to adjust the camera parameters and take a clear image, and record the shooting distance lt;

[0015] Step 1.5: Repeat steps 1.3 and 1.4 until the checkerboard mark moves to the calibration end position;

[0016] Step 1.6: Establish a relationship between the laser point spacing and the measured distance. Obtain the sum of the pixel distances dt between the laser spot center points of the lasers in the image captured at the t-th shooting position. Obtain the sum of the actual distances Dt between the laser spot center points of the lasers in the t-th shooting position. Perform a linear fit between dt and the shooting distance lt to obtain a linear equation lt = k1dt + b1. Perform a linear fit between Dt and the shooting distance lt to obtain a linear equation lt = k2Dt + b2. Obtain the ratio αt of the pixel distances between the laser spot center points of a particular laser and its two adjacent lasers in the image captured at the t-th shooting position, and calculate the average value α of the αt at each position. Obtain the ratio βt of the pixel distance between the laser spot center points of a particular laser and one of its adjacent lasers to the pixel distances between the laser spot center points of the other two lasers in the image captured at the t-th shooting position, and calculate the average value β of the βt at each position.

[0017] Step 2: Move the measurement system to the vicinity of the defect to be measured, turn on the pan / tilt camera and laser of the measurement system, so that the four laser points and the defect features to be measured are all within the camera image;

[0018] Step 3: Adjust the gimbal angle according to the laser point pixel distance ratio so that the gimbal camera is perpendicular to the defect to be measured;

[0019] Step 4: Infer the current measurement distance l0;

[0020] Step 4.1: Extract the coordinates of the center point of the laser spot in the current captured image, and calculate the sum of the pixel distances d0 between the center points of the laser spot of the laser in the current captured image;

[0021] Step 4.2: Substitute d0 into the linear equation lt = k1dt + b1 to calculate the current shooting distance l0;

[0022] Step 5: Calculate the pixel scale of the current shooting distance;

[0023] Step 5.1: Substitute the current measured distance l0 into the lt of the linear equation lt = k2Dt + b2 to calculate the sum of the physical distances of the laser points at the current shooting distance, D0;

[0024] Step 5.2: The ratio of the sum of the physical distances D0 to the sum of the pixel distances d0 is the pixel scale of the current shooting distance.

[0025] Step 6: Calculate the defect characteristic size.

[0026] In some embodiments, the calibration device includes a sliding track, a tooling fixture, and a checkerboard calibration plate. The measurement system is installed on the calibration device, specifically including: the underwater image acquisition module is fixed at one end of the sliding guide rail through the tooling fixture, making the axis of the laser sealing housing parallel to the length direction of the sliding guide rail; the checkerboard calibration plate is installed on the sliding guide rail through the tooling fixture, making the plane of the checkerboard calibration plate parallel to the end faces of 4 laser sealing housings.

[0027] In some embodiments, in step one, the initial calibration position is that the checkerboard calibration plate is 200 mm away from the end face of the laser seal, moving a certain distance of 50 mm, and the end position is that the checkerboard calibration plate is 1000 mm away from the end face of the laser seal.

[0028] In some embodiments, in step one, the 4 lasers are respectively laser A, laser B, laser C, and laser D. Laser B is on the right side of laser A, laser D is below laser B, laser C is on the left side of laser D, and laser A is above laser C. The pixel distance between the center points of the light spot between the laser points of laser A and laser B in the image is d1, the pixel distance between the center points of the light spot between the laser points of laser B and laser D in the image is d2, the pixel distance between the center points of the light spot between the laser points of laser D and laser C in the image is d3, and the pixel distance between the center points of the light spot between the laser points of laser C and laser A in the image is d4; where αt is the ratio of d1 to d2 at the t-th shooting position, and βt is the ratio of d1 to d3 at the t-th shooting position.

[0029] In some embodiments, step three specifically includes:

[0030] Step 3.1: Obtain the coordinates of the center points of the laser spots of the 4 lasers in the current image, calculate the ratio α0 of the current laser pixel distance d1 to d2, and calculate the ratio β0 of the current laser pixel distance d1 to d3;

[0031] Step 3.2: Compare α0 with the calibration value α, and compare β0 with the calibration value β. If |α0 - α| < threshold and |β0 - β| < threshold, it means that the current camera pose meets the requirements. If the requirements are not met, adjust the rotation of the camera pan-tilt until the measurement requirements are met;

[0032] In some embodiments, in step 3.2, threshold is a preset threshold.

[0033] In some embodiments, step six specifically includes: Select an approximate geometric shape in the drawing tool according to the shape of the defect feature to envelope the defect in the captured image, calculate the size of the geometric shape, and then calculate the actual size of the geometric shape through the pixel scale, which is the defect feature size.

[0034] The implementation of the present invention has the following beneficial effects:

[0035] This paper proposes a multi-laser-point underwater plane dimension measurement system and method. This method utilizes four parallel lasers to project a light spot array onto the surface to be measured. A high-definition camera captures an image containing the light spots and defect features. The pixel scale of the current image is calculated based on the pixel distance and physical distance between the light spots, thereby quantitatively measuring the two-dimensional size of the defect. This system effectively solves the problem of measuring planar defect dimensions in the absence of landmarks, facilitating maintenance of nuclear power plant water tanks and preventing coolant leaks. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of an underwater plane dimension measurement system based on multiple laser points proposed in an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of the laser arrangement of an underwater plane dimension measurement system based on multiple laser points proposed in an embodiment of the present invention;

[0038] Figure 3 A schematic diagram of a measurement system for underwater plane dimension measurement based on multiple laser points proposed in an embodiment of the present invention;

[0039] Figure 4 A schematic diagram of laser points in an underwater plane dimension measurement system based on multiple laser points proposed in an embodiment of the present invention;

[0040] Figure 5 This is a calibration flow chart of a method for underwater plane dimension measurement based on multiple laser points proposed in an embodiment of the present invention;

[0041] Figure 6 A defect measurement flow chart of a method for underwater plane dimension measurement based on multiple laser points proposed in an embodiment of the present invention;

[0042] Description of the drawings: 1. Pan-tilt camera; 2. Laser A; 3. Laser B; 4. Laser C; 5. Laser D; 6. Laser sealed housing; 7. Laser mounting plate; 8. Control computer; 9. Cables. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] like Figures 1 to 6 As shown, the present invention proposes an underwater plane dimension measurement system based on multiple laser points. The measurement system includes an underwater image acquisition module and an above-water control module. The underwater image acquisition module includes a pan-tilt camera 1, four lasers, four laser sealed housings 6, and a laser mounting plate 7. The center of the laser mounting plate 7 is provided with a camera mounting hole, and the four corners of the laser mounting plate 7 are provided with laser mounting holes. The pan-tilt camera 1 is installed in the camera mounting hole of the laser mounting plate 7. Lasers A2, B3, C4, and D5 are fixedly mounted in the four laser mounting holes of the laser mounting plate 7 through the laser sealed housing 6. Specifically, laser B3 is to the right of laser A2, laser D5 is below laser B3, laser C4 is to the left of laser D5, and laser A2 is above laser C4.

[0045] After installation, the gimbal camera 1 is positioned at the center of the four lasers, directly facing the imaging plane. The gimbal camera 1 is fixed relative to the lasers, rotating and pitching as a whole under the control of the gimbal.

[0046] The above-water control module includes a control computer 8, a cable 9, and control and measurement software. The control computer 8 connects to the PTZ camera 1 and the laser via the cable 9. The control and measurement software is integrated into the control computer 8. The control and measurement software includes a PTZ motion control module, a camera control module, a laser control module, a calibration module, and a measurement module. The PTZ motion control module controls the PTZ camera 1's PTZ movements according to commands.

[0047] The camera control module can adjust parameters such as the camera exposure time of the pan-tilt camera 1 and send instructions to control the camera to take pictures; the laser control module can control the laser switch and adjust the laser brightness; the calibration module is used to calibrate the positional relationship between the four lasers before measurement; the measurement module is used to calculate the defect size based on the image taken by the pan-tilt camera 1.

[0048] The present invention proposes an underwater plane dimension measurement method based on multiple laser points, which includes:

[0049] Step 1: Calibrate the measurement system

[0050] Step 1.1: Install the laser mounting plate 7 of the underwater image acquisition module of the measurement system on the calibration device, which includes a sliding rail, a fixture and a checkerboard calibration plate. The underwater image acquisition module is fixed to one end of the sliding guide rail through the fixture, and the axis of the laser sealing shell 6 is parallel to the length direction of the guide rail; the checkerboard calibration plate is also installed on the sliding guide rail through the fixture, and the plane of the checkerboard calibration plate is parallel to the end faces of the four laser sealing shells.

[0051] Step 1.2: Slide the checkerboard calibration plate to the initial calibration position of the unified calibration device. The initial calibration position is 200 mm between the checkerboard calibration plate and the laser sealing end face. The control computer 8 controls the pan-tilt camera 1 to capture images.

[0052] Step 1.3: Slide the checkerboard calibration plate a certain distance away from the laser, and move the checkerboard calibration plate along the guide rail a certain distance (eg, 50 mm) away from the laser emission direction.

[0053] Step 1.4: Control computer 8 to adjust camera parameters to capture a clear image. The pan-tilt camera 1 used in the measurement system is a fixed-focus camera. Changes in object distance will cause the image to be out of focus. Observe the real-time image captured by the camera by controlling computer 8. Use the camera control module of the control and measurement software to automatically focus and adjust parameters such as exposure time and aperture until the pan-tilt camera 1 can capture a clear checkerboard image. Capture and save the image and record the current shooting distance.

[0054] Step 1.5: Repeat steps 1.3 and 1.4 until the checkerboard calibration plate moves to the calibration end position, which is 1000 mm from the checkerboard calibration plate to the laser sealing end face.

[0055] Step 1.6: Establish the relationship between the laser point spacing and the measured distance, extract the coordinates of the corner points of the checkerboard calibration plate in the captured image, and calculate the pixel scale of the current image based on the coordinates of the corner points of the checkerboard calibration plate and the actual physical distance of the corner points. The ratio of the physical distance between the corner points to the pixel distance in the image is the pixel scale. Record the shooting distance lt corresponding to the current image and extract the coordinates of the center points of the four laser spots in the image. Figure 4 As shown, the pixel distance between the center points of the light spots of the laser points of laser A2 and laser B3 in the image is d1, the pixel distance between the center points of the light spots of the laser points of laser B3 and laser D5 in the image is d2, the pixel distance between the center points of the light spots of the laser points of laser D5 and laser C4 in the image is d3, the pixel distance between the center points of the light spots of the laser points of laser C4 and laser A2 in the image is d4, the actual distance between the center points of the light spots of the laser points of laser A2 and laser B3 is D1, the pixel distance between the center points of the light spots of the laser points of laser A2 and laser B3 is D2, the pixel distance between the center points of the light spots of the laser points of laser A2 and laser B3 is D3, and the pixel distance between the center points of the light spots of the laser points of laser A2 and laser B3 is D4.

[0056] Calculate the sum of the pixel distances dt of each laser point at the t-th position captured, as calculated by formula (1). Calculate the sum of the actual laser point distances Dt at the t-th position, as calculated by formula (2).

[0057]

[0058] According to lt and dt, the linear equation Y = k1X + b1 is fitted (the horizontal axis is the sum of the laser point pixel distance, and the vertical axis is the shooting distance); according to lt and Dt, the linear equation Y = k2X + b2 is fitted (the horizontal axis is the shooting distance, and the vertical axis is the sum of the laser point physical distance).

[0059] Obtain the ratio αt of the t-th position d1 to d2, the ratio βt of the t-th position d1 to d3, and calculate the average value α of each position αt, and the average value β of each position βt, as shown in formula (3) and formula (4), where n is the total number of shooting positions.

[0060]

[0061] Step 2: If Figure 4 As shown, the measurement system reaches the vicinity of the defect to be measured. Use a floating robot or a long pole tool to carry the measurement system to the vicinity of the defect to be measured, turn on the pan-tilt camera 1 and the laser, so that the four laser points and the defect features are all in the camera image.

[0062] Step 3: Adjust the gimbal angle according to the laser point pixel distance ratio;

[0063] Step 3.1: Determine the coordinates of the laser spot centers of the four lasers in the current image, and calculate the ratio α0 of the current laser pixel distance d1 to d2, and the ratio β0 of the current laser pixel distance d1 to d3;

[0064] Step 3.2: Compare α0 with the calibration value α, and β0 with the calibration value β. If |α0-α|>threshold and |β0-β|>threshold, the current camera pose does not meet the requirements. Adjust the camera gimbal rotation based on the difference until the measurement requirements are met. Where threshold is a preset threshold. Smaller values ​​are closer to vertical, resulting in higher accuracy and longer pose adjustment time. Larger values ​​increase the error and make it easier to adjust to the measured pose.

[0065] Step 4: Infer the current pose and measure the distance;

[0066] Step 4.1: Extract the coordinates of the center point of the laser spot in the current captured image, and calculate the sum of the pixel distances d0 between the center points of the laser spot of the laser in the current captured image;

[0067] Step 4.2: Substitute d0 into X in the linear equation Y=k1X+b1 (the horizontal axis is the sum of the laser point pixel distance and the vertical axis is the shooting distance) to calculate the current shooting distance l0.

[0068] Step 5: Calculate the pixel scale of the current shooting distance;

[0069] Step 5.1: Substitute the current measured distance l0 into the linear equation Y = k2X + b2 (the horizontal axis is the shooting distance, the vertical axis is the sum of the physical distances of the laser points) to calculate the sum of the physical distances of the laser points at the current shooting distance, D0;

[0070] Step 5.2: The ratio of the sum of the physical distances D0 to the sum of the pixel distances d0 is the pixel scale of the current shooting distance, and its unit is mm / pixel.

[0071] Step 6: Calculate the defect feature size. Based on the shape of the defect feature, select an approximate geometric figure in the drawing tool to envelop the defect in the captured image, calculate the size of the geometric figure, and then calculate the size of the actual geometric figure using the pixel scale, which is the defect feature size. If the defect feature is a line feature such as a crack, select the straight line tool and calculate the length of the defect based on the length of the drawn straight line. If the defect is a nearly square feature, select the rectangle tool, draw a rectangular frame to envelop the defect feature, and calculate the length and width of the defect based on the pixel values ​​of the length and width of the rectangular frame. If the defect is a nearly circular or elliptical feature, select the circle or ellipse tool, draw a circle or ellipse feature to envelop the defect, and then obtain the diameter of the defect or the length of the ellipse.

[0072] The above embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. An underwater plane dimension measurement system based on multiple laser points, characterized in that: The system comprises an underwater image acquisition module and an above-water control module. The underwater image acquisition module comprises a pan-tilt camera (1), four lasers, four laser sealing shells (6) and a laser mounting plate (7). A camera mounting hole is provided at the center of the laser mounting plate (7), and laser mounting holes are respectively provided at four corners of the laser mounting plate (7). The pan-tilt camera (1) is installed at the camera mounting hole of the laser mounting plate (7), and the four lasers are respectively fixedly installed in the four laser mounting holes of the laser mounting plate (7) through the laser sealing shells (6). The above-water control module is connected to the pan-tilt camera (1) and the lasers.

2. The underwater plane dimension measurement system based on multiple laser points according to claim 1, characterized in that: The above-water control module comprises a control computer (8), a cable (9) and control and measurement software. The control computer (8) is connected to the pan-tilt camera (1) and the laser through the cable (9). The control and measurement software is integrated in the control computer (8).

3. The underwater plane dimension measurement system based on multiple laser points according to claim 2, characterized in that: The control and measurement software includes a pan-tilt motion control module, a camera control module, a laser control module, a calibration module and a measurement module. The pan-tilt motion control module controls the pan-tilt motion of the pan-tilt camera (1). The camera control module adjusts the camera parameters of the pan-tilt camera (1) and controls the camera to take pictures. The laser control module controls the laser switch and adjusts the laser brightness. The calibration module calibrates the positional relationship between the four lasers before measurement. The measurement module calculates the size of the plane defect based on the image captured by the pan-tilt camera (1).

4. The underwater plane dimension measurement method based on multiple laser points according to any one of claims 1 to 3, characterized in that: The method comprises: Step 1: calibrating the measurement system; Step 1.1: Install the measurement system on the calibration device; Step 1.2: Slide the checkerboard calibration plate to the initial calibration position of the unified calibration device; Step 1.3: Slide the checkerboard calibration plate a certain distance away from the laser; Step 1.4: The control and measurement software of the control computer (8) adjusts the camera parameters and takes a clear image, and records the shooting distance lt; Step 1.5: Repeat steps 1.3 and 1.4 until the checkerboard mark moves to the calibration end position; Step 1.6: Establish a relationship between the laser point spacing and the measured distance. Obtain the sum of the pixel distances dt between the laser spot center points of the lasers in the image captured at the t-th shooting position. Obtain the sum of the actual distances Dt between the laser spot center points of the lasers in the t-th shooting position. Perform a linear fit between dt and the shooting distance lt to obtain a linear equation lt = k1dt + b1. Perform a linear fit between Dt and the shooting distance lt to obtain a linear equation lt = k2Dt + b2. Obtain the ratio αt of the pixel distances between the laser spot center points of a particular laser and its two adjacent lasers in the image captured at the t-th shooting position, and calculate the average value α of the αt at each position. Obtain the ratio βt of the pixel distance between the laser spot center points of a particular laser and one of its adjacent lasers to the pixel distances between the laser spot center points of the other two lasers in the image captured at the t-th shooting position, and calculate the average value β of the βt at each position. Step 2: Move the measuring system to the vicinity of the defect to be measured, turn on the pan / tilt camera (1) and the laser of the measuring system, so that the four laser points and the features of the defect to be measured are all within the camera image; Step 3: Adjust the pan-tilt angle according to the laser point pixel distance ratio so that the pan-tilt camera (1) is perpendicular to the defect to be measured; Step 4: Infer the current measurement distance l0; Step 4.1: Extract the coordinates of the center point of the laser spot in the current captured image, and calculate the sum of the pixel distances d0 between the center points of the laser spot of the laser in the current captured image; Step 4.2: Substitute d0 into dt in the linear equation lt = k1dt + b1 to calculate the current shooting distance l0; Step 5: Calculate the pixel scale of the current shooting distance; Step 5.1: Substitute the current measured distance l0 into the lt of the linear equation lt = k2Dt + b2 to calculate the sum of the physical distances of the laser points at the current shooting distance, D0; Step 5.2: The ratio of the sum of the physical distances D0 to the sum of the pixel distances d0 is the pixel scale of the current shooting distance; Step 6: Calculate the defect characteristic size.

5. The underwater plane dimension measurement method based on multiple laser points according to claim 4 is characterized in that: The calibration device comprises a sliding rail, a fixture and a checkerboard calibration plate. The measurement system is installed on the calibration device, specifically comprising: fixing the underwater image acquisition module to one end of the sliding rail through the fixture so that the axis of the laser sealed housing (6) is parallel to the length direction of the sliding rail; and installing the checkerboard calibration plate on the sliding rail through the fixture so that the plane of the checkerboard calibration plate is parallel to the end faces of the four laser sealed housings.

6. The underwater plane dimension measurement method based on multiple laser points according to claim 5, characterized in that: In the step 1, the initial calibration position is 200 mm from the checkerboard calibration plate to the laser sealing end face, the movement distance is 50 mm, and the end position is 1000 mm from the checkerboard calibration plate to the laser sealing end face.

7. The underwater plane dimension measurement method based on multiple laser points according to claim 6, characterized in that: In step 1, the four lasers are laser A (2), laser B (3), laser C (4) and laser D (5). The right side of laser A (2) is laser B (3), the lower side of laser B (3) is laser D (5), the left side of laser D (5) is laser C (4), and the upper side of laser C (4) is laser A (2). The pixel distance between the center points of the laser spots of laser A (2) and laser B (3) in the image is d 1, the pixel distance between the center points of the light spots between the laser points of laser B (3) and laser D (5) in the image is d2, the pixel distance between the center points of the light spots between the laser points of laser D (5) and laser C (4) in the image is d3, and the pixel distance between the center points of the light spots between the laser points of laser C (4) and laser A (2) in the image is d4; where αt is the ratio of d1 to d2 at the t-th shooting position, and βt is the ratio of d1 to d3 at the t-th shooting position.

8. The underwater plane dimension measurement method based on multiple laser points according to claim 7, characterized in that: The step three specifically includes: Step 3.1: Determine the coordinates of the laser spot centers of the four lasers in the current image, and calculate the ratio α0 of the current laser pixel distance d1 to d2, and the ratio β0 of the current laser pixel distance d1 to d3; Step 3.2: Compare α0 with the calibration value α and β0 with the calibration value β. If |α0 - α| < threshold and |β0 - β| < threshold, it means that the current camera pose meets the requirements. If not, adjust the rotation of the camera pan-tilt until the measurement requirements are met.

9. The underwater plane dimension measurement method based on multiple laser points according to claim 8, characterized in that: The preset threshold preset for threshold in the said Step 3.

2.

10. The underwater plane dimension measurement method based on multiple laser points according to claim 9, characterized in that: The said Step Six specifically includes: Select an approximate geometric figure in the drawing tool according to the shape of the defect feature to envelope the defect in the captured image, calculate the size of the geometric figure, and then calculate the actual size of the geometric figure through the pixel scale, which is the defect feature size.

Images