Panoramic three-dimensional scanning device and measuring method for inner wall of pipeline

Abstract

The invention discloses a pipeline inner wall panoramic three-dimensional scanning device and a measuring method, and the device comprises a panoramic plane laser generator which comprises a point laser generator, an axicon, a laser focusing lens, a conical surface reflector and a transparent cylindrical support, and is used for transmitting a 360-degree panoramic plane laser beam to the inner wall of an object to be measured; according to the invention, single-exposure full-circumferential high-precision three-dimensional measurement is realized, and the device can synchronously obtain complete three-dimensional point cloud data of the circumference of the inner wall of the whole pipeline at the moment of single exposure through innovative combination of a panoramic annular imaging system and a panoramic planar laser projection technology; the method has the advantages that axial rotary scanning or multi-view data splicing required by a traditional method is avoided, measurement efficiency is improved, splicing accumulative errors are avoided, laser stripe image acquisition is complete and free of breakpoints, and completeness and accuracy of three-dimensional reconstruction data are guaranteed from the source.

Description

Technical Field

[0001] This invention relates to the field of three-dimensional measurement, specifically to a panoramic three-dimensional scanning device and measurement method for the inner wall of a pipe. Background Technology

[0002] As a critical component in industrial production and infrastructure, the accurate detection of defects such as corrosion, cracks, and deformation on the inner walls of pipelines is of paramount importance. Currently, pipeline inner wall measurement technologies are mainly divided into two categories: methods based on two-dimensional images and methods based on three-dimensional reconstruction.

[0003] The first type of method is based on two-dimensional image analysis. These systems typically employ monocular or multi-view cameras and use image processing algorithms (such as edge detection and template matching) to extract two-dimensional information about the pipe's inner wall, including edges, textures, and dimensions, from single or multiple planar images. However, this method essentially projects a three-dimensional scene onto a two-dimensional plane, failing to acquire depth information and thus making it difficult to accurately measure pits, bulges, and curved surfaces on the inner wall. Furthermore, two-dimensional measurements are susceptible to interference from lighting conditions, shadows, and surface reflections, resulting in insufficient stability and reliability of the measurement results, making it difficult to meet the demands of high-precision industrial inspection.

[0004] To acquire 3D information, the second type of method employs 3D measurement techniques. One approach is based on parallax principles (such as binocular vision) or active light sources (such as line laser scanning). Binocular vision relies on matching natural feature points on the inner wall to calculate depth information, but its reconstructed point cloud is sparse, with poor detail reproduction, and performs poorly in areas with missing or repetitive textures. Monocular line laser scanning obtains high-precision cross-sectional contours through laser triangulation, but requires axial movement to complete full-circumference measurement, resulting in extremely low measurement efficiency and unsuitability for rapid inspection of long-distance pipes. Another common drawback of both approaches is the low utilization of the central field of view; most of the field of view is used to photograph irrelevant internal pipe spaces, leading to low effective data density.

[0005] The third type of method aims to address the issues of measurement efficiency and completeness, employing multi-sensor fusion or complex layout schemes. For example, it uses a multi-camera array arranged around the perimeter, or combines cameras and LiDAR to stitch together multi-view point clouds for full-circumference coverage. While this type of method can theoretically achieve panoramic 3D reconstruction of the pipe's inner wall, its system structure is exceptionally complex. It requires precise calibration of the spatial relationships between multiple sensors, a cumbersome calibration process with low on-site deployment efficiency. Furthermore, the multi-source data fusion algorithms are complex and computationally intensive, making real-time processing difficult and increasing the overall system cost and maintenance complexity. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an improvement by offering a panoramic three-dimensional scanning device and measurement method for the inner wall of pipes. This invention is achieved through the following technical solution:

[0007] This invention discloses a panoramic three-dimensional scanning device for the inner wall of a pipe, comprising:

[0008] A panoramic planar laser generator includes a point laser generator, an axial cone mirror, a laser focusing lens, a conical reflector, and a transparent cylindrical support, used to emit a 360° panoramic planar laser beam onto the inner wall of the object to be measured.

[0009] A panoramic ring camera is used to capture images of laser stripes generated when the inner wall of an object under test is illuminated by a panoramic planar laser generator.

[0010] A displacement device is used to fix the panoramic planar laser generator and the panoramic ring camera, and to move them to achieve scanning;

[0011] A transparent mounting cover is used to connect and secure the panoramic loop camera to the panoramic planar laser generator;

[0012] A computer, connected to both a panoramic ring camera and a displacement device, is used to set the movement method of the displacement device, capture and process laser stripe images captured by the panoramic ring camera, and calculate the three-dimensional point cloud of the object.

[0013] As a further improvement, in the panoramic planar laser generator of the present invention, the point laser generator, the axial conical mirror, and the laser focusing lens are coaxially fixed inside the lens barrel along the laser emission direction. The emission end of the laser focusing lens is connected to the conical reflector through a transparent cylindrical bracket, and the axis of symmetry of the conical reflector also coincides with the optical axis of the laser focusing lens.

[0014] As a further improvement, the present invention also includes a test pipe used for verification as the test object. The test pipe is fixed on the experimental platform. The panoramic planar laser generator and the panoramic ring camera are connected through a transparent mounting cover and fixed at both ends of the transparent mounting cover, and the whole extends into the test pipe from one side and is fixed on the displacement device.

[0015] As a further improvement, the beam emitted by the point laser generator in the panoramic planar laser generator of the present invention is modulated by the axial conical mirror, the laser focusing lens, and the conical reflector to become a laser plane, and is emitted through a transparent cylindrical support. The base angle α of the axial conical mirror and the apex angle β of the conical reflector in the panoramic planar laser generator have the following relationship:

[0016]

[0017] Where n is the refractive index of the axial cone, γ is the refraction angle of the first surface of the axial cone, and θ is the exit angle of the second surface of the axial cone;

[0018] Furthermore, when the axial conical mirror and the conical reflector of the panoramic planar laser generator are not perfectly coaxially aligned, resulting in a deviation of δ degrees, the modulated image still forms a single laser plane, as shown in the following relationship:

[0019]

[0020] Where x is the angle between the laser plane and the optical axis, it can be found by comparing with the above formula that when the axial conical mirror and the conical reflector of the panoramic plane laser generator are not coaxially aligned and there is a deviation of δ degrees, the laser plane also has a deviation of δ degrees relative to the optical axis, but its surface shape does not change.

[0021] This invention also discloses a measurement method based on a panoramic three-dimensional scanning device for the inner wall of a pipe, comprising the following steps:

[0022] The panoramic planar laser generator and the panoramic ring camera are connected through a transparent mounting cover and fixed to both ends of the transparent mounting cover respectively. One end of the panoramic ring camera is fixed to the displacement device.

[0023] Place the checkerboard calibration board in different fields of view of the panoramic ring camera and take multiple images of the calibration board;

[0024] The camera's intrinsic parameters are calculated using the camera calibration algorithm and the obtained calibration board images;

[0025] The checkerboard calibration plate was placed in different fields of view of the panoramic ring camera, and multiple sets of images of the calibration plate illuminated by the laser emitted by the panoramic planar laser generator and those not illuminated were captured.

[0026] The sub-pixel coordinates of the center point of the laser line in the image are extracted using a laser centerline extraction algorithm and an image of a calibration board illuminated by a laser emitted from a panoramic planar laser generator.

[0027] By using the optical plane calibration algorithm, the three-dimensional coordinates of the laser line center point in the camera coordinate system are calculated by combining the camera's intrinsic parameters, the unilluminated calibration board image, and the sub-pixel coordinates of the corresponding laser line center point.

[0028] The equation of the light plane is calculated using a plane fitting algorithm and the three-dimensional coordinates of the center point of the laser line in the camera coordinate system.

[0029] The checkerboard calibration plate is fixed on the experimental platform. The computer controls the displacement device to move a certain distance and takes an image of the calibration plate.

[0030] Repeat the previous step to obtain at least three images of the calibration plate under different displacements;

[0031] By combining the camera's intrinsic parameters with the calibration plate images under different displacements using the orientation fitting algorithm, the movement direction vector of the displacement device in the camera coordinate system is calculated.

[0032] The pipe under test is fixed on the experimental platform, and the panoramic planar laser generator and panoramic ring camera are inserted from one side of the pipe under test. The displacement device is controlled by computer to move a certain distance and take a picture of the laser stripe on the pipe under test as the laser emitted by the panoramic planar laser generator illuminates it.

[0033] Repeat the previous step to obtain multiple laser stripe images with different displacements but the same interval distance;

[0034] Using a laser centerline extraction algorithm and multiple laser stripe images, the sub-pixel coordinates of the center point of the laser line in each laser stripe image are calculated.

[0035] By combining the camera's intrinsic parameters, the light plane equation, the movement direction vector, the sub-pixel coordinates of the center point of the laser stripe in each laser stripe image, and the interval distance, the three-dimensional coordinates of the inner wall of the pipe under test in the camera coordinate system are calculated.

[0036] As a further improvement, the camera calibration algorithm described in this invention is the panoramic ring camera calibration algorithm proposed by Christopher MEI, and the camera intrinsic parameters include the parameter matrix K, the distortion vector D, and the mirror parameters ξ.

[0037] As a further improvement, the laser centerline extraction algorithm of this invention uses the Hessian matrix to obtain the normal direction of the laser stripes in the image, and then performs Taylor expansion of the image grayscale along the normal direction to obtain its maximum value as the sub-pixel coordinates of the laser line center point. The optical plane calibration algorithm uses the Perspective-n-Point algorithm, combined with the camera's intrinsic parameters and the unilluminated calibration board image, to obtain the pose of the corresponding laser line center point, and calculates the three-dimensional coordinates corresponding to the sub-pixel coordinates of the laser line center point through geometric relationships. The plane fitting algorithm uses the least squares method to fit the three-dimensional coordinates into a plane. The optical plane equation is:

[0038] ax+by+cz+d=0.

[0039] As a further improvement, the orientation fitting algorithm described in this invention utilizes the Perspective-n-Point algorithm, combined with the camera's intrinsic parameters and calibration board images under different displacements, to obtain the pose of the corresponding calibration board, and then uses the least squares method to fit a spatial straight line to obtain the movement direction vector. The movement direction vector is:

[0040] M=(m x ,m y ,mz ).

[0041] As a further improvement, the specific steps of the three-dimensional reconstruction algorithm described in this invention are as follows:

[0042] Let the sub-pixel coordinates of the center point of the laser stripe in the i-th laser stripe image be (u i ,v i );

[0043] Using camera intrinsic parameters to (u i ,v i Transformed into normalized coordinates (x, y) in the camera coordinate system with respect to z. i ,y i ,1);

[0044] Solve for the optical center of the camera, i.e., the origin of the camera coordinate system and (x) i ,y i 1) The direction vector of the connecting lines (X) i ,Y i ,1);

[0045] The solution direction vector is (X) i ,Y i The intersection point of the line (1) and the equation of the light plane

[0046] The final three-dimensional coordinates of a point can be obtained by using the displacement interval t between the movement direction vector and each image.

[0047] The beneficial effects of this invention are as follows:

[0048] 1. This invention achieves high-precision three-dimensional measurement of the entire circumference in a single exposure. By innovatively combining a panoramic ring imaging system with panoramic planar laser projection technology, the device can simultaneously acquire complete three-dimensional point cloud data of the entire inner circumference of the pipe in a single exposure, avoiding the axial rotation scanning or multi-view data stitching required by traditional methods, thus improving measurement efficiency and eliminating stitching accumulation errors.

[0049] 2. The present invention reconstructs a point cloud with high density and strong detail restoration capability. Based on the active laser triangulation method, it directly calculates depth information by analyzing the deformation of panoramic planar laser stripes on the curved surface of the inner wall of the pipe. The three-dimensional point cloud density reconstructed by this method is higher than that of methods based on binocular parallax or structured light coding. It can accurately restore the microscopic defects such as corrosion, cracks, and pits on the inner wall. The measurement accuracy and resolution are significantly better than existing solutions.

[0050] 3. The system of the present invention has a compact structure and strong robustness. The core of the device consists of only two optical components: a panoramic ring camera and a panoramic planar laser generator. This eliminates the need for complex multi-camera arrays, motion mechanisms, or lidar combinations. The system has a simple structure, small size, and is easy to integrate and package. It is easy to enter the interior of pipes of different diameters. At the same time, the active laser has strong resistance to ambient light interference and is suitable for industrial sites with variable lighting conditions or dim lighting.

[0051] 4. This invention features a unique optical design, simple calibration, and high fault tolerance. The panoramic planar laser generator employs an innovative combination of an axial cone mirror and a conical reflector. Its optical characteristics allow for the effective modulation of a continuous laser plane covering 360° even with slight installation errors (not strictly coaxial). This feature reduces the stringent requirements for precision machining, simplifies assembly, and lowers manufacturing costs.

[0052] 5. The calibration process of this invention is simple and convenient to deploy. The device adopts an integrated design. The panoramic ring camera and the panoramic planar laser generator are fixedly connected through a transparent mounting cover to form a stable internal spatial relationship. Once the system parameters are calibrated before leaving the factory, no recalibration is required in all subsequent field testing applications, realizing "plug and play". This greatly improves the efficiency and convenience of field deployment and is suitable for automated, high-frequency industrial testing scenarios.

[0053] 6. The present invention provides an unobstructed field of view and complete data acquisition. The transparent bracket design of the device ensures the rigidity of the system structure while guaranteeing that the panoramic ring camera has a complete 360° unobstructed field of view, which makes the laser stripe image acquisition complete and without breaks, thus ensuring the integrity and accuracy of the 3D reconstruction data from the source. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of a panoramic 3D scanning device for the inner wall of a pipe.

[0055] Figure 2 This is a diagram illustrating the components of a panoramic planar laser generator;

[0056] Figure 3 This diagram illustrates the relationship between the base angle of the axial conical mirror and the apex angle of the conical reflector to ensure that the emitted laser beam is planar.

[0057] Figure 4 This diagram illustrates the change in the emitted laser surface when the axial conical mirror and the conical reflector are not coaxially aligned.

[0058] Figure 5 This is a flowchart of a panoramic 3D measurement scheme for the inner wall of a pipeline;

[0059] In the diagram, 1 is a panoramic planar laser generator, 2 is a panoramic ring camera, 3 is a displacement device, 4 is a transparent mounting cover, 5 is a computer, 6 is the pipe under test, 7 is a point laser generator, 8 is an axial cone mirror, 9 is a laser focusing lens, 10 is a conical reflector, 11 is a transparent cylindrical support, and 12 is the laser emitted by the point laser generator.

[0060] in, Figure 2 yes Figure 1 A partially enlarged structural diagram of component 2 (panoramic planar laser generator). Figure 3 and Figure 4 yes Figure 1 The enlarged schematic diagram of part 2 (panoramic planar laser generator) is mainly for illustrating the optical principle, and some parts of the structure are omitted. Detailed Implementation

[0061] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0062] This invention discloses a panoramic three-dimensional scanning device for the inner wall of a pipe. Figure 1 This is a schematic diagram of the device, which includes the following components:

[0063] Panoramic planar laser generator 1 is used to emit a 360° panoramic planar laser beam toward the inner wall of the object to be tested. Its specific composition will be analyzed later.

[0064] The panoramic ring camera 2 is used to capture images of laser stripes generated when the inner wall of the object under test is irradiated by the panoramic planar laser generator 1.

[0065] The displacement device 3 is used to fix the panoramic planar laser generator 1 and the panoramic ring camera 2, and to move them to achieve scanning;

[0066] Transparent mounting cover 4 is used to connect panoramic planar laser generator 1 and panoramic ring camera 2;

[0067] Computer 5 is connected to panoramic ring camera 2 and displacement device 3 respectively. It is used to capture and process laser stripe images captured by panoramic ring camera 2, set the movement method of displacement device 3, and calculate the three-dimensional point cloud of the object.

[0068] Pipe 6, to be tested, is used as the object to be tested;

[0069] In a specific embodiment, the test pipe 6 is fixed on the experimental platform, the panoramic planar laser generator 1 and the panoramic ring camera 2 are respectively fixed at both ends of the transparent mounting cover 4, placed inside the test pipe 6, and one end of the panoramic ring camera 2 is fixed on the displacement device 3 by a bracket.

[0070] The following is combined with Figure 2The specific components of the aforementioned panoramic planar laser generator are as follows:

[0071] A panoramic planar laser generator includes the following components:

[0072] Point laser generator 7 is used to emit a beam of expanded Gaussian point laser;

[0073] Axicone mirror 8 is used to transform the expanded Gaussian point laser into a conical laser.

[0074] Laser focusing lens 9 is used to focus the laser beam onto the conical surface;

[0075] A conical reflector 10 is used to modulate the focused conical laser into a panoramic planar laser;

[0076] A cylindrical transparent support 11 is used to transmit panoramic planar laser light, providing support for the conical reflector 10 without blocking the laser light.

[0077] In a specific embodiment, the point laser generator 7, the axial conical mirror 8, and the laser focusing lens 9 are coaxially fixed inside the lens barrel along the laser emission direction. The emission end of the laser focusing lens 9 is connected to the conical reflector 10 through a transparent cylindrical bracket 11. The axis of symmetry of the conical reflector 10 also coincides with the optical axis of the laser focusing lens 9. The axial conical mirror 8 and the conical reflector 10 have a decisive influence on the surface shape of the emitted laser, as will be discussed in the subsequent analysis.

[0078] The following is combined with Figure 3 Explanation: Assuming the modulated laser surface is planar, the relationship between the base angle of the central axis conical mirror and the apex angle of the conical reflector in the panoramic planar laser generator is as follows:

[0079] Assuming the axial conical mirror 8 and the conical reflector 10 are coaxially aligned, the laser beam 12 is an expanded Gaussian beam before passing through the axial conical mirror 8. After passing through the axial conical mirror 8, it becomes a conical laser beam, which, after being modulated by the conical reflector 10, becomes a laser plane perpendicular to the optical axis. The base angle α of the axial conical mirror 8 and the apex angle β of the conical reflector 10 have the following relationship:

[0080]

[0081] Where n is the refractive index of the material of the axial conical mirror 8, γ is the refraction angle of the first surface of the axial conical mirror 8, and θ is the refraction angle of the second surface of the axial conical mirror 8.

[0082] In a specific embodiment, the refractive index of the axial conical mirror 8 is 1.5, the base angle of the cone is 5°, and the apex angle of the conical reflector 10 is 92.5°, which satisfies the above relationship and makes the emitted laser a plane.

[0083] The following is combined with Figure 4Note that if the axial conical mirror and the conical reflector of the panoramic planar laser generator are not coaxially aligned and there is a deviation, the modulated laser surface will change as follows:

[0084] Furthermore, when the axial conical mirror 8 and the conical reflector 10 of the panoramic planar laser generator are not perfectly coaxially aligned and have a deviation of δ degrees, the modulated result is still a single laser plane, with the following relationship:

[0085]

[0086] Where x is the angle between the laser plane and the optical axis. Comparing with the above formula, it can be found that when the axis conical mirror 8 and the conical reflector 10 of the panoramic plane laser generator are not coaxially aligned and have a deviation of δ degrees, the laser beam 12 will also have a certain deviation after passing through the axis conical mirror 8 and the conical reflector 10. At this time, the laser plane also has a deviation of δ degrees relative to the optical axis, but it does not change its surface shape.

[0087] In a specific embodiment, there may be a certain error when the axial conical mirror 8 and the conical reflector 10 are installed, and it is not required that their optical axes coincide. At this time, the emitted laser is still a plane.

[0088] This invention also discloses a method for panoramic three-dimensional measurement of the inner wall of a pipe. Figure 5 This is a flowchart of the method, which includes the following steps:

[0089] 1. Connect the panoramic planar laser generator and the panoramic ring camera through a transparent mounting cover, fix them to both ends of the transparent mounting cover respectively, and fix the entire assembly of the panoramic ring camera to the displacement device through one end.

[0090] 2. Place the checkerboard calibration board in different fields of view of the panoramic ring camera, ensuring that the entire calibration board is clearly visible, and take multiple images of the calibration board. Using the panoramic ring camera calibration algorithm proposed by Christopher MEI, calculate the camera's intrinsic parameters, including the parameter matrix K, distortion vector D, and mirror parameters ξ.

[0091] 3. Place the checkerboard calibration board in different fields of view of the panoramic ring camera to ensure that the entire calibration board is clearly visible. Take multiple sets of images of the calibration board illuminated by the laser emitted by the panoramic planar laser generator and images of the calibration board that are not illuminated. Using the laser centerline extraction algorithm, extract the sub-pixel coordinates of the center point of the laser line in the calibration board image illuminated by the laser emitted by the panoramic planar laser generator. Combine the corresponding calibration board images and use the light plane calibration algorithm to obtain the three-dimensional coordinates of the center point of the laser line in the camera coordinate system. Calculate the light plane equation using the plane fitting algorithm.

[0092] Let the sub-pixel coordinates of the center point of the i-th laser line in the k-th calibration plate image be... The rotation matrix and translation vector corresponding to the calibration plate image are R and R, respectively. k With T k Then the equation of the calibration plate plane in the camera coordinate system can be obtained as follows:

[0093]

[0094] in, For R k The corresponding element in For T k Given the corresponding elements, and assuming the camera's intrinsic parameter transformation is f(K,D,ξ), then the normalized coordinates of the laser line center point in the camera coordinate system are... satisfy

[0095]

[0096] Simultaneous equations of a straight line in space The three-dimensional coordinates of the laser line in the camera coordinate system can be obtained by calculating the equation of the calibration plate plane in the camera coordinate system. according to

[0097]

[0098] The equation for the light plane can be obtained as ax + by + cz + d = 0, where a, b, c, and d are the four parameters of the light plane equation, K is the number of calibration plate images, and N is the number of images. k Let be the number of center points of the laser lines on the k-th calibration board.

[0099] 4. Fix the checkerboard calibration plate on the experimental platform. Control the displacement device to move a certain distance using a computer. Take a picture of the calibration plate with a panoramic ring camera. Obtain at least three images of the calibration plate under different displacements. Calculate the movement direction vector of the displacement device in the camera coordinate system by combining the direction fitting algorithm with the camera's intrinsic parameters.

[0100] Let T be the translation vector corresponding to the calibration plate image. k Then take a set of points For T k The corresponding elements are used to obtain the movement direction vector M = (m) through a spatial straight line fitting algorithm. x ,m y ,m z ).

[0101] 5. Fix the pipe to be tested on the experimental platform. Use a computer-controlled displacement device to move the pipe a certain distance at each step and take a picture of the laser stripe image emitted by the panoramic planar laser generator illuminating the pipe.

[0102] 6. Using the laser centerline extraction algorithm, extract the sub-pixel coordinates of the center points of the laser lines in the laser stripe image from step 5. Let the sub-pixel coordinates of the center point of the j-th laser line in the l-th image be...

[0103] 7. According to

[0104]

[0105] Find the normalized z-coordinates in the camera coordinate system.

[0106] 8. Find the optical center (0,0,0) and its normalized coordinates. Direction vectors of connected straight lines

[0107]

[0108] 9. Find the intersection point of the line obtained in step 7 and the light plane ax + by + cz + d = 0, and solve the system of equations simultaneously.

[0109]

[0110] The intersection point can then be obtained.

[0111] 10. The three-dimensional coordinates are obtained based on the displacement interval and the direction vector of movement. Let the step size of the computer-controlled displacement device be t. Then the final obtained three-dimensional coordinates are:

[0112] 11. The computer-controlled displacement device continues to move forward a distance t, and repeats steps 5 to 10 until the scan is complete.

[0113] The above description is not intended to limit the present invention. It should be noted that, for those skilled in the art, various changes, modifications, additions or substitutions can be made without departing from the essential scope of the present invention, and these improvements and refinements should also be considered within the scope of protection of the present invention.

Claims

1. A panoramic three-dimensional scanning device for the inner wall of a pipe, characterized in that, include: A panoramic planar laser generator includes a point laser generator, an axial cone mirror, a laser focusing lens, a conical reflector, and a transparent cylindrical support, used to emit a 360° panoramic planar laser beam onto the inner wall of the object to be measured. A panoramic ring camera is used to capture images of laser stripes generated when the inner wall of the object under test is irradiated by the panoramic planar laser generator. A displacement device is used to fix the panoramic planar laser generator and the panoramic ring camera, and to move them to achieve scanning; A transparent mounting cover is used to connect and fix the panoramic ring camera to the panoramic planar laser generator; A computer is connected to both the panoramic ring camera and the displacement device, and is used to set the movement method of the displacement device, capture and process the laser stripe image captured by the panoramic ring camera, and calculate the three-dimensional point cloud of the object.

2. The panoramic three-dimensional scanning device for the inner wall of a pipe according to claim 1, characterized in that, In the panoramic planar laser generator, the point laser generator, the axial conical mirror, and the laser focusing lens are coaxially fixed inside the lens barrel along the laser emission direction. The emission end of the laser focusing lens is connected to the conical reflector through a transparent cylindrical bracket. The axis of symmetry of the conical reflector also coincides with the optical axis of the laser focusing lens.

3. The panoramic three-dimensional scanning device for the inner wall of a pipe according to claim 1, characterized in that, It also includes a test pipe used as the test object for verification. The test pipe is fixed on the experimental platform. The panoramic planar laser generator and the panoramic ring camera are connected through the transparent mounting cover and fixed to both ends of the transparent mounting cover. The whole unit extends into the test pipe from one side and is fixed on the displacement device.

4. The panoramic three-dimensional scanning device for the inner wall of a pipe according to claim 2, characterized in that, The beam emitted by the point laser generator in the panoramic planar laser generator is modulated by the axial cone mirror, the laser focusing lens, and the conical reflector to become a laser plane, which is then emitted through a transparent cylindrical support. The base angle α of the axial cone mirror and the apex angle β of the conical reflector in the panoramic planar laser generator have the following relationship: Where n is the refractive index of the axial cone, γ is the refraction angle of the first surface of the axial cone, and θ is the exit angle of the second surface of the axial cone; Furthermore, when the axial conical mirror and the conical reflector of the panoramic planar laser generator are not perfectly coaxially aligned, resulting in a deviation of δ degrees, the modulated image still forms a single laser plane, as shown in the following relationship: Where x is the angle between the laser plane and the optical axis, it can be found by comparing with the above formula that when the axial conical mirror and the conical reflector of the panoramic plane laser generator are not coaxially aligned and there is a deviation of δ degrees, the laser plane also has a deviation of δ degrees relative to the optical axis, but its surface shape does not change.

5. A measurement method based on the panoramic three-dimensional scanning device for the inner wall of a pipe as described in claim 1, 2, 3, or 4, characterized in that, Includes the following steps: The panoramic planar laser generator and the panoramic ring camera are connected through a transparent mounting cover and fixed to both ends of the transparent mounting cover respectively. One end of the panoramic ring camera is fixed to the displacement device. The checkerboard calibration board is placed in different fields of view of the panoramic ring camera, and multiple images of the calibration board are taken; the camera's intrinsic parameters are calculated using the camera calibration algorithm and the obtained calibration board images. The checkerboard calibration plate was placed in different fields of view of the panoramic ring camera, and multiple sets of images of the calibration plate illuminated by the laser emitted by the panoramic planar laser generator and those not illuminated were captured. The sub-pixel coordinates of the center point of the laser line in the image are extracted using a laser centerline extraction algorithm and an image of a calibration board illuminated by a laser emitted from a panoramic planar laser generator. By using the optical plane calibration algorithm, the three-dimensional coordinates of the laser line center point in the camera coordinate system are calculated by combining the camera's intrinsic parameters, the unilluminated calibration board image, and the sub-pixel coordinates of the corresponding laser line center point. The equation of the light plane is calculated using a plane fitting algorithm and the three-dimensional coordinates of the center point of the laser line in the camera coordinate system. The checkerboard calibration plate is fixed on the experimental platform. The computer controls the displacement device to move a certain distance and takes an image of the calibration plate. Repeat the previous step to obtain at least three images of the calibration plate under different displacements; By combining the camera's intrinsic parameters with the calibration plate images under different displacements using the orientation fitting algorithm, the movement direction vector of the displacement device in the camera coordinate system is calculated. The pipe under test is fixed on the experimental platform, and the panoramic planar laser generator and panoramic ring camera are inserted from one side of the pipe under test. The displacement device is controlled by computer to move a certain distance and take a picture of the laser stripe on the pipe under test as the laser emitted by the panoramic planar laser generator illuminates it. Repeat the previous step to obtain multiple laser stripe images with different displacements but the same interval distance; Using a laser centerline extraction algorithm and multiple laser stripe images, the sub-pixel coordinates of the center point of the laser line in each laser stripe image are calculated. By combining the camera's intrinsic parameters, the light plane equation, the movement direction vector, the sub-pixel coordinates of the center point of the laser stripe in each laser stripe image, and the interval distance, the three-dimensional coordinates of the inner wall of the pipe under test in the camera coordinate system are calculated.

6. The panoramic three-dimensional measurement method for the inner wall of a pipeline according to claim 5, characterized in that, The camera calibration algorithm is the panoramic ring camera calibration algorithm proposed by Christopher MEI. The camera intrinsic parameters include the parameter matrix K, the distortion vector D, and the mirror parameters ξ.

7. The panoramic three-dimensional measurement method for the inner wall of a pipeline according to claim 5, characterized in that, The laser centerline extraction algorithm uses the Hessian matrix to obtain the normal direction of the laser stripes in the image, and then performs Taylor expansion of the image grayscale along the normal direction to obtain its maximum value as the sub-pixel coordinates of the laser line center point. The optical plane calibration algorithm uses the Perspective-n-Point algorithm, combined with the camera's intrinsic parameters and the unilluminated calibration board image, to obtain the pose of the corresponding laser line center point, and calculates the three-dimensional coordinates corresponding to the sub-pixel coordinates of the laser line center point through geometric relationships. The plane fitting algorithm uses the least squares method to fit the three-dimensional coordinates into a plane. The optical plane equation is: ax+by+cz+d=0.

8. The panoramic three-dimensional measurement method for the inner wall of a pipeline according to claim 5, characterized in that, The orientation fitting algorithm described above utilizes the Perspective-n-Point algorithm, combined with the camera's intrinsic parameters and calibration board images under different displacements, to obtain the pose of the corresponding calibration board. Then, it uses the least squares method to fit a spatial straight line to obtain the movement direction vector. The movement direction vector is: M=(m x ,m y ,m z )。 9. The panoramic three-dimensional measurement method for the inner wall of a pipeline according to claim 5, characterized in that, The specific steps of the 3D reconstruction algorithm are as follows: Let the sub-pixel coordinates of the center point of the laser stripe in the i-th laser stripe image be (u i ,v i ); Using camera intrinsic parameters to (u i ,v i Transformed into normalized coordinates (x, y) in the camera coordinate system with respect to z. i ,y i ,1); Solve for the optical center of the camera, i.e., the origin of the camera coordinate system and (x) i ,y i 1) The direction vector of the connecting lines (X) i ,Y i ,1); The solution direction vector is (X) i ,Y i The intersection point of the straight line (1) with the equation of the light plane The final three-dimensional coordinates of the point are obtained by using the displacement interval t between the movement direction vector and each image.

Images