Capillary outer diameter determination method, electronic equipment, storage medium and detection system

Abstract

The invention relates to the technical field of online detection of capillary diameters based on images, in particular to a capillary outer diameter determination method, electronic equipment, a storage medium and a detection system.The method includes the steps that firstly, a first image and a second image are obtained; then respectively extracting image coordinate information of the laser rays in the images from the first image and the second image, and performing coordinate conversion on the two pieces of image coordinate information to obtain two pieces of world coordinate information; then determining two positioning center coordinates according to the two pieces of world coordinate information, and determining the gradient of the capillary tube according to the two center coordinates; and finally, performing circle fitting according to the gradient and the two pieces of world coordinate information to obtain the outer diameter of the capillary. The coordinates of the two laser lines on the capillary in the image are converted into the world coordinates, the gradient of the capillary is determined through the world coordinates, the diameter of the capillary is determined based on the gradient, and compared with the prior art, the diameter detection result is more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of on-line detection of capillary tube diameters based on images, and particularly relates to a method for determining the outer diameter of a capillary tube, an electronic device, a storage medium, and a detection system. Background Art

[0002] The steel pipe billet refers to a hollow long-strip semi-finished product with certain dimensions and surface quality processed from an ingot or a billet through processes such as piercing during the steel pipe production process. It is the basis for further processing into various specifications and applications of steel pipes. The main use of the steel pipe billet is as an intermediate raw material for further processing of steel pipes. Through subsequent hot rolling, cold rolling, cold drawing and other processes, the billet can be processed into finished steel pipes of various different specifications and uses, and is widely used in many fields such as construction, machinery, petrochemical industry, shipbuilding, and aerospace.

[0003] On-line detection during billet production refers to the real-time detection of multiple parameters including the outer diameter of the billet during the billet production process, so as to timely adjust the production equipment to meet the quality requirements of the billet.

[0004] Currently, the mainstream technologies for on-line detection of billet outer diameters include: machine vision detection method, photoelectric on-line diameter measuring instrument detection method, and ultrasonic detection method. Among these, the machine vision detection method is highly regarded due to its high environmental adaptability. However, the main problem with the machine vision detection method is that it is affected by the production environment, and its detection results are unstable. Especially when the billet is tilted during the production process, a large error will occur.

[0005] Based on this, it is necessary to develop and design a method for determining the outer diameter of a billet. Summary of the Invention

[0006] The embodiments of the present invention provide a method for determining the outer diameter of a billet, an electronic device, a storage medium, and a detection system, which are used to solve the problem that the results of detecting the outer diameter of a billet by the machine vision detection method in the prior art are inaccurate.

[0007] In a first aspect, an embodiment of the present invention provides a billet outer diameter detection system, including: two line-structured lasers, two cameras, and a processor; The two line-structured lasers and the two cameras are respectively electrically connected to the processor; The laser wavelengths emitted by the two line-structured lasers are different; When the billet is located in the laser projection area of the two line-structured lasers, the two line-structured lasers project two laser lines on the outer contour of the billet; The two cameras are respectively provided with filtering devices, and the wavelengths corresponding to the filtering devices of the two cameras correspond one-to-one to the wavelengths of the two line-structured lasers emitting light; When the two cameras respectively capture images containing laser line images, the processor determines the surface profile of the capillary tube based on the positions of the laser line in the two images, and determines the outer diameter of the capillary tube based on the surface profile.

[0008] In a possible implementation manner, the two stripe structure lasers and the two cameras are all located at the same height, and the horizontal distance between the two stripe structure lasers is the same as the horizontal distance between the two cameras.

[0009] In a second aspect, an embodiment of the present invention provides a method for determining the outer diameter of a capillary tube, including: Obtain a first image and a second image, where the first image and the second image respectively include laser lines generated by a stripe structure laser on the capillary tube; Extract the image coordinate information of the laser line in the image from the first image and the second image respectively, and perform coordinate transformation on the two image coordinate information to obtain two world coordinate information, where the world coordinate information is the coordinate information of the laser line in the world coordinate system; Determine two positioning center coordinates according to the two world coordinate information, and determine the inclination of the capillary tube according to the two center coordinates, where the positioning center coordinate is the center coordinate of the cross-section of the capillary tube where the laser line is located; Perform circular fitting according to the inclination and the two world coordinate information to obtain the outer diameter of the capillary tube.

[0010] In a possible implementation manner, the performing coordinate transformation on the two image coordinate information to obtain two world coordinate information includes: The image coordinate information includes multiple pixel coordinates of the laser line image. For each image coordinate information, the following steps are respectively performed: Obtain depth information, an internal camera parameter matrix, and an external camera parameter matrix, where the internal parameter matrix reflects the relationship between the pixel coordinates on the camera imaging plane and the coordinates in the camera coordinate system, the external camera parameter matrix reflects the relationship between the camera coordinate system and the world coordinate system, and the depth information reflects the distance from the point in the image to the camera; Convert the image coordinate information according to the internal camera parameter matrix and the depth information to obtain intermediate coordinate information, where the intermediate coordinate information represents the coordinates of each point of the laser line in the coordinate system with the camera optical center as the coordinate origin; Convert the intermediate coordinate information according to the external camera parameter matrix to obtain world coordinate information, where the world coordinate information represents the coordinates of each point of the laser line in the world coordinate system.

[0011] In a possible implementation manner, converting the image coordinate information according to the camera intrinsic matrix and the depth information to obtain intermediate coordinate information includes: Converting the image coordinate information according to a first formula, the camera intrinsic matrix, and the depth information to obtain intermediate coordinate information, where the first formula is:

[0012] In the formula: 、 and are the coordinates of the x-axis, y-axis, and z-axis in the intermediate coordinate system of the laser point respectively, is the depth information, is the intrinsic matrix, is the focal length of the x-axis, is the focal length of the y-axis, and are the coordinates of the x-axis and y-axis of the intersection point of the optical axis and the image plane on the image plane respectively, 、 and are the coordinates of the x-axis, y-axis, and z-axis of the laser point in the image coordinate system respectively; Converting the intermediate coordinate information according to the camera extrinsic matrix to obtain world coordinate information includes: Converting the intermediate coordinate information according to a second formula and the camera extrinsic matrix to obtain world coordinate information, where the second formula is:

[0013] In the formula: is the rotation matrix describing the rotation of the camera in the world coordinate system, is the vector describing the translation of the camera in the world coordinate system, 、 and are the coordinates of the x-axis, y-axis, and z-axis of the laser point in the world coordinate system respectively.

[0014] In a possible implementation manner, determining two positioning center coordinates according to the two world coordinate information, and determining the inclination of the capillary according to the two center coordinates includes: Constructing a first ellipse equation based on the focus; Fitting the first ellipse equation according to the two world coordinate information by using the least squares method or the random sample consensus algorithm to obtain a second ellipse equation and a third ellipse equation; According to the second ellipse equation and the third ellipse equation, determine a first focal pair and a second focal pair respectively, where the first focal pair and the second focal pair each include two foci extracted according to the second ellipse equation and the third ellipse equation; Determine a first positioning center coordinate and a second positioning center coordinate according to the first focal pair and the second focal pair; Calculate the difference between the first positioning center coordinate and the second positioning center coordinate to obtain a coordinate difference; Determine the inclination of the capillary according to the coordinate difference and the length of the laser line spacing, where the laser line spacing is the spacing between two laser lines on the capillary.

[0015] In a possible implementation manner, the first ellipse equation is:

[0016] In the formula, is the distance from the laser point to the first focus, is the distance from the laser point to the second focus, , and are the coordinates of the laser point on the x-axis, y-axis and z-axis in the world coordinate system respectively, , and are the coordinates of the first focus of the ellipse on the x-axis, y-axis and z-axis in the world coordinate system respectively, , and are the coordinates of the second focus of the ellipse on the x-axis, y-axis and z-axis in the world coordinate system respectively, is a sum constant; The determining the inclination of the capillary according to the coordinate difference and the length of the laser line spacing includes: Determine the inclination of the capillary according to a third formula, the coordinate difference and the length of the laser line spacing, where the third formula is:

[0017] In the formula, , and are the coordinate differences of the x-axis, y-axis and z-axis respectively, is the angle between the capillary and the x-axis in the xy plane, is the angle between the capillary and the x-axis in the xz plane, is the comprehensive inclination, is the length of the laser line spacing, is the arcsine function.

[0018] In a possible implementation manner, one of the two world coordinate information is used as the outer diameter estimation coordinate information. The circular fitting based on the inclination and the two world coordinate information to obtain the capillary outer diameter includes: Construct a fourth ellipse equation based on the major axis and the minor axis according to the inclination, where the fourth ellipse equation is:

[0019] In the formula, 、 and are the coordinates of the laser point on the x-axis, y-axis, and z-axis in the world coordinate system respectively, 、 and are the coordinates of the laser point on the x-axis, y-axis, and z-axis after rotating degrees in the xz coordinate plane respectively, 、 and are the coordinates of the laser point on the x-axis, y-axis, and z-axis after rotating degrees in the xy coordinate plane respectively, is the major axis, is the minor axis, is the capillary radius, is the angle between the capillary and the x-axis in the xy plane, is the angle between the capillary and the x-axis in the xz plane; According to the outer diameter estimation coordinate information, use the least squares method or the random sample consensus algorithm to fit the fourth ellipse equation to obtain the fifth ellipse equation; Determine the capillary diameter according to the capillary radius in the fifth ellipse equation.

[0020] In a third aspect, an embodiment of the present invention provides a capillary outer diameter determination device for implementing the capillary outer diameter determination method described in the above second aspect or any possible implementation manner of the second aspect. The capillary outer diameter determination device includes: An image acquisition module for acquiring a first image and a second image, where the first image and the second image respectively include laser lines generated by a line structure laser on the capillary; A coordinate conversion module for respectively extracting the image coordinate information of the laser line in the image from the first image and the second image, and performing coordinate conversion on the two image coordinate information to obtain two world coordinate information, where the world coordinate information is the coordinate information of the laser line in the world coordinate system; ​​​​The capillary inclination determination module is configured to determine two positioning center coordinates according to the two world coordinate information, and determine the inclination of the capillary according to the two center coordinates, where the positioning center coordinate is the center coordinate of the cross-section of the capillary where the laser line is located; And, The capillary outer diameter determination module is configured to perform circular fitting according to the inclination and the two world coordinate information to obtain the outer diameter of the capillary.

[0021] In a fourth aspect, an embodiment of the present invention provides an electronic device, including a memory and a processor. A computer program that can run on the processor is stored in the memory. When the processor executes the computer program, the steps of the method described in the second aspect or any possible implementation manner of the second aspect above are implemented.

[0022] In a fifth aspect, an embodiment of the present invention provides a computer-readable storage medium. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the steps of the method described in the second aspect or any possible implementation manner of the second aspect above are implemented.

[0023] The beneficial effect of the embodiment of the present invention compared with the prior art is: An embodiment of the present invention discloses a method for determining the outer diameter of a capillary. First, a first image and a second image are obtained, where the first image and the second image respectively include laser lines generated by a line structure laser on the capillary; then, the image coordinate information of the laser lines in the images is respectively extracted from the first image and the second image, and the two image coordinate information is subjected to coordinate transformation to obtain two world coordinate information, where the world coordinate information is the coordinate information of the laser line in the world coordinate system; then, according to the two world coordinate information, two positioning center coordinates are determined, and the inclination of the capillary is determined according to the two center coordinates, where the positioning center coordinate is the center coordinate of the cross-section of the capillary where the laser line is located; finally, circular fitting is performed according to the inclination and the two world coordinate information to obtain the outer diameter of the capillary. The present invention first generates two laser lines on the capillary through a laser, then converts the coordinates of the laser lines in the image to the world coordinates, then determines the inclination of the capillary through the world coordinates, and finally determines the diameter of the capillary based on the inclination. Since the influence of the inclination on the detection of the capillary diameter is considered, the diameter detection result is more accurate than the current technology. Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 is the schematic diagram of the capillary outer diameter detection system provided by the embodiment of the present invention; Figure 2 is the flowchart of the method for determining the outer diameter of the capillary provided by the embodiment of the present invention; Figure 3 is the functional block diagram of the device for determining the outer diameter of the capillary provided by the embodiment of the present invention; Figure 4 is the functional block diagram of the electronic device provided by the embodiment of the present invention. Detailed Embodiments

[0026] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will be described through specific embodiments in conjunction with the drawings.

[0028] The following will give a detailed description of the embodiments of the present invention. This example is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0029] Figure 1 is the schematic diagram of the capillary outer diameter detection system provided by the first aspect of the embodiment of the present invention.

[0030] The embodiment of the present invention provides a capillary outer diameter detection system, including: two line-structured lasers, two cameras, and a processor; The two line-structured lasers and the two cameras are respectively electrically connected to the processor; The laser wavelengths emitted by the two line-structured lasers are different; When the capillary is located in the laser projection area of the two line-structured lasers, the two line-structured lasers project two laser lines on the outer contour of the capillary; Each of the two cameras is provided with a filtering device, and the wavelengths corresponding to the filtering devices of the two cameras correspond one-to-one to the emission wavelengths of the two stripe structure lasers; When the two cameras respectively acquire laser line images, the processor determines the surface profile of the capillary tube based on the positions of the laser lines in the two images, and determines the outer diameter of the capillary tube based on the surface profile.

[0031] In a possible implementation manner, the two stripe structure lasers and the two cameras are all located at the same height, and the horizontal distance between the two stripe structure lasers is the same as the horizontal distance between the two cameras.

[0032] Exemplarily, as Figure 1 shown, the installation positions of the components of the outer diameter detection system for the capillary tube in the steel pipe production line are as Figure 1 shown. This detection system adopts a non-contact method. The cylinder is the capillary tube 101 to be measured, the horizontal plane and the vertical plane are part of the capillary tube processing equipment 102: the piercing mill. Above the front of the capillary tube 101 is the stripe structure laser 103, the upper left is the camera 104, and in front of the capillary tube 101 is the hot metal detection sensor 105. In an application scenario, two stripe structure lasers 103 each emit a blue and a green laser line from a height of 2400 mm relative to the ground and a horizontal distance of 1600 mm relative to the axis of the capillary tube 101 to irradiate the capillary tube 101 to be measured, and the two cameras 104 observe the laser lines on the capillary tube 101 at a place 1400 mm horizontally away from the stripe structure lasers 103. The hot metal detection sensor 105 is installed in the space below the cameras 104 and the stripe structure lasers 103.

[0033] In order to ensure that each of the two cameras only observes one laser line, a filtering device is added to the system. Through filtering, the camera can only receive photons in a specific wavelength band. For example, when using a blue laser with a wavelength of 450 ± 5 nm, a filtering device is installed on the camera observing the laser, and only photons with wavelengths from 440 nm to 480 nm are allowed to pass through.

[0034] The specific detection steps of this system are as follows: First, project two line structure lasers onto the surface of the capillary tube, and use two cameras to respectively acquire the surface laser line images; then use an image analysis model to extract the centers of the laser lines, so as to obtain the laser line profile on the surface of the capillary tube through three-dimensional space coordinate conversion; then correct the detection error caused by the inclination of the capillary tube through the synchronous detection of the two laser line profiles to achieve the correction of the outer diameter profile of the capillary tube; finally, perform circular fitting on the obtained corrected continuous capillary tube cross-sectional profile information to obtain the outer diameter size of the capillary tube.

[0035] The embodiment of the present invention elaborates on the above process in detail from the second aspect.

[0036] Figure 2 This is a flowchart of the method for determining the outer diameter of a capillary tube provided in the second aspect of the embodiments of the present invention.

[0037] As Figure 2 shown, it shows the implementation flowchart of the method for determining the outer diameter of a capillary tube provided in the embodiments of the present invention, which is described in detail as follows: In step 201, a first image and a second image are acquired, wherein the first image and the second image respectively include laser lines generated by a line-structured laser on the capillary tube.

[0038] In step 202, the image coordinate information of the laser lines in the image is respectively extracted from the first image and the second image, and the two image coordinate information is subjected to coordinate transformation to obtain two world coordinate information, wherein the world coordinate information is the coordinate information of the laser lines in the world coordinate system.

[0039] In some embodiments, the performing coordinate transformation on the two image coordinate information to obtain two world coordinate information includes: The image coordinate information includes multiple pixel coordinates of the laser line image. For each image coordinate information, the following steps are respectively performed: Depth information, an internal camera matrix, and an external camera matrix are acquired, wherein the internal matrix reflects the relationship between the pixel coordinates on the camera imaging plane and the coordinates in the camera coordinate system, the external camera matrix reflects the relationship between the camera coordinate system and the world coordinate system, and the depth information reflects the distance from the points in the image to the camera; The image coordinate information is transformed according to the internal camera matrix and the depth information to obtain intermediate coordinate information, wherein the intermediate coordinate information represents the coordinates of each point of the laser line in the coordinate system with the camera optical center as the coordinate origin; The intermediate coordinate information is transformed according to the external camera matrix to obtain world coordinate information, wherein the world coordinate information represents the coordinates of each point of the laser line in the world coordinate system.

[0040] In some embodiments, the transforming the image coordinate information according to the internal camera matrix and the depth information to obtain intermediate coordinate information includes: The image coordinate information is transformed according to a first formula, the internal camera matrix, and the depth information to obtain intermediate coordinate information, wherein the first formula is:

[0041] In the formula, , and are respectively the coordinates of the x-axis, y-axis, and z-axis in the intermediate coordinate system of the laser point, is the depth information, is the intrinsic matrix, is the focal length on the x-axis, is the focal length on the y-axis, and are the x-axis and y-axis coordinates of the intersection point of the optical axis and the image plane on the image plane respectively, 、 and are the x-axis, y-axis and z-axis coordinates of the laser point in the image coordinate system respectively; The conversion of the intermediate coordinate information according to the external camera matrix to obtain world coordinate information includes: Converting the intermediate coordinate information according to the second formula and the external camera matrix to obtain world coordinate information, where the second formula is:

[0042] In the formula, is the rotation matrix describing the rotation of the camera in the world coordinate system, is the vector describing the translation of the camera in the world coordinate system, 、 and are the x-axis, y-axis and z-axis coordinates of the laser point in the world coordinate system respectively.

[0043] Exemplarily, as described above, the laser generated by the laser will generate a laser line on the capillary tube. The wavelengths generated by the two lasers are different, and the filters at the front ends of the two cameras correspond to the wavelengths of the two lasers. That is to say, the two cameras respectively capture the images of a laser line. Since the images of the laser line are significantly different in color from the images generated by other objects, the images of other objects can be further eliminated by a color filtering algorithm, and only the laser line is retained.

[0044] The coordinate information of the laser line in the world coordinate can be calculated from the laser line image. In fact, the world coordinate information of the laser line is a set of the coordinates of multiple laser line pixel points in the world coordinate.

[0045] Before the conversion, the camera will be calibrated to obtain the depth information, the intrinsic matrix of the camera and the external matrix of the camera.

[0046] There are various methods to obtain the intrinsic matrix. For example, the self-calibration method is adopted. Principle: It is not necessary to use a specific calibration board, but to use the geometric relationship and motion information between images to estimate the camera intrinsic parameters.

[0047] For example, by taking images of a series of scenes, analyzing the motion and transformation of feature points in the images, and using geometric constraint conditions such as epipolar geometry and homography matrix, combined with some assumptions and algorithms to solve for the camera internal parameters.

[0048] In the present invention, the distance from the hot metal detection sensor to the capillary is determined (the hot metal detection sensor and the axis of the capillary are at the same height), and then the depth information is determined according to the position of the hot metal detection sensor relative to the camera and the position relative to the laser.

[0049] The external parameter matrix is used to describe the position and orientation of the camera coordinate system relative to the world coordinate system, and is composed of a rotation matrix R (representing rotation) and a translation vector T (representing translation). The method of camera calibration is usually adopted to determine the external parameter matrix: Prepare the calibration object: Select a calibration object with known geometric features. The most commonly used is the checkerboard calibration board. The checkerboard consists of black and white square grids, and the side length of each grid is known and fixed. Through precise machining and measurement, the three-dimensional coordinates of the feature points (usually the corner points of the black and white grids) on the checkerboard in the world coordinate system are determined. Generally, the origin of the world coordinate system is set at a certain corner point of the checkerboard, and the coordinate axis directions are parallel to the sides of the checkerboard.

[0050] Collect calibration images: Use the camera to be calibrated to take multiple images of the calibration object from different angles and positions. When taking pictures, ensure that the calibration object occupies an appropriate size and position in the image, and the image is clear enough to accurately detect the feature points on the calibration object. Generally, it is recommended to take 10 to 20 images to cover various possible postures and perspectives of the camera.

[0051] Feature point detection: Process each collected calibration image, and use image processing algorithms (such as corner detection algorithms, common ones include Harris corner detection, Shi-Tomasi corner detection, etc.) to detect the pixel coordinates of the feature points on the calibration object in the image. The coordinates of these feature points in the image will be important data for subsequent calculations.

[0052] Calculation based on mathematical model: The coordinates of the feature points in the world coordinate system (determined by the calibration object) and the pixel coordinates in the image , as well as the camera internal parameter matrix K obtained in advance by other methods, optimization algorithms such as the least squares method can be used to solve for the rotation matrix R and the translation vector T. In actual calculations, some mature computer vision libraries (such as OpenCV) are usually used to implement these algorithms. OpenCV provides special functions and tools that can conveniently perform camera calibration and calculation of the external parameter matrix.

[0053] Optimization and Verification: To improve the accuracy of the extrinsic parameter matrix, the calculation results are usually optimized. Methods such as maximum likelihood estimation can be used to further adjust the values of the rotation matrix R and the translation vector T to minimize the reprojection error (i.e., the error between the coordinates obtained by projecting points in the world coordinate system onto the image plane according to the calculated extrinsic and intrinsic parameter matrices and the actual detected image coordinates). At the same time, additional image data can be used to verify the calculated extrinsic parameter matrix to check its accuracy and reliability in different scenarios. Through the above steps, the extrinsic parameter matrix of the camera can be determined, thus establishing the conversion relationship between the camera coordinate system and the world coordinate system.

[0054] After obtaining the depth information, the camera intrinsic parameter matrix, and the camera extrinsic parameter matrix, the image coordinate information can be converted into intermediate coordinate information through the first formula:

[0055] In the formula, 、 and are the coordinates of the x-axis, y-axis, and z-axis in the intermediate coordinate system of the laser point respectively, is the depth information, is the intrinsic parameter matrix, is the focal length of the x-axis, is the focal length of the y-axis, and are the coordinates of the x-axis and y-axis of the intersection point of the optical axis and the image plane on the image plane respectively, 、 and are the coordinates of the x-axis, y-axis, and z-axis of the laser point in the image coordinate system respectively.

[0056] Then, the intermediate coordinate information is converted into world coordinate information again through the second formula:

[0057] In the formula, is the rotation matrix describing the rotation of the camera in the world coordinate system, is the vector describing the translation of the camera in the world coordinate system, 、 and are the coordinates of the x-axis, y-axis, and z-axis of the laser point in the world coordinate system respectively.

[0058] In step 203, according to the two world coordinate information, two positioning center coordinates are determined, and the inclination of the capillary is determined according to the two center coordinates, where the positioning center coordinate is the center coordinate of the cross-section of the capillary where the laser line is located.

[0059] In some embodiments, determining two positioning center coordinates according to the two world coordinate information and determining the inclination of the capillary according to the two center coordinates includes: Construct a first ellipse equation based on the focus; According to the two world coordinate information, use the least squares method or the random sample consensus algorithm to fit the first ellipse equation to obtain a second ellipse equation and a third ellipse equation; According to the second ellipse equation and the third ellipse equation, determine a first focus pair and a second focus pair respectively, where the first focus pair and the second focus pair each include two foci extracted according to the second ellipse equation and the third ellipse equation; According to the first focus pair and the second focus pair, determine a first positioning center coordinate and a second positioning center coordinate; Calculate the difference between the first positioning center coordinate and the second positioning center coordinate to obtain a coordinate difference; Determine the inclination of the capillary according to the coordinate difference and the length of the laser line spacing, where the laser line spacing is the spacing between two laser lines on the capillary.

[0060] In some embodiments, the first ellipse equation is:

[0061] In the formula, is the distance from the laser point to the first focus, is the distance from the laser point to the second focus, , and are the coordinates of the laser point on the x-axis, y-axis and z-axis in the world coordinate system respectively, , and are the coordinates of the first focus of the ellipse on the x-axis, y-axis and z-axis in the world coordinate system respectively, , and are the coordinates of the second focus of the ellipse on the x-axis, y-axis and z-axis in the world coordinate system respectively, is a constant; The determining the inclination of the capillary according to the coordinate difference and the length of the laser line spacing includes: Determine the inclination of the capillary according to a third formula, the coordinate difference and the length of the laser line spacing, where the third formula is:

[0062] In the formula, , and They are the coordinate differences of the x-axis, y-axis, and z-axis respectively. is the angle between the capillary and the x-axis in the xy plane. is the angle between the capillary and the x-axis in the xz plane. is the comprehensive inclination. is the length of the laser line spacing. is the arcsine function.

[0063] Exemplarily, the embodiment of the present invention determines the inclination of the capillary axis according to the centers of two laser lines, and then fits one of the laser lines (elliptical contour) based on the inclination, so as to determine the diameter of the capillary.

[0064] In determining the inclination of the capillary, in the first elliptical equation based on two world coordinate information and the focus, the least squares method or the random sample consensus algorithm is used to fit the first elliptical equation to obtain the elliptical equation with the best fitting degree. According to the coordinates of the two foci in this elliptical equation with the best fitting degree, the center of the ellipse where the elliptical line is located is found, and then based on the two centers, the inclination of the capillary is determined.

[0065] The first elliptical equation is:

[0066] In the formula, is the distance from the laser point to the first focus. is the distance from the laser point to the second focus. , and are the coordinates of the laser point on the x-axis, y-axis, and z-axis in the world coordinate system respectively. , and are the coordinates of the first focus of the ellipse on the x-axis, y-axis, and z-axis in the world coordinate system respectively. , and are the coordinates of the second focus of the ellipse on the x-axis, y-axis, and z-axis in the world coordinate system respectively. is the sum constant.

[0067] In an application scenario, the Random Sample Consensus (RANSAC) algorithm is used to fit the first ellipse equation. The principle of this algorithm is as follows: The core idea of RANSAC is to randomly select a minimum subset from the dataset through random sampling. This subset contains enough sample points to estimate the parameters of the model. For example, for line fitting, the minimum subset usually contains 2 points (because two points determine a line); for estimating a plane, 3 points are required. An estimated model is obtained using the selected minimum subset, and then this model is used to test all points in the dataset. According to a certain error threshold, each point is determined whether it is an inlier (i.e., a point that conforms to the model) or an outlier (i.e., a point that does not conform to the model). The above processes of sampling, estimating the model, and classifying inliers and outliers are repeated multiple times, and the number of inliers is recorded for each iteration. When the algorithm ends, the model obtained from the iteration with the largest number of inliers is selected as the final estimated model.

[0068] Steps of the algorithm: First, initialize: Set parameters such as the number of iterations N and the error threshold t. Then, randomly sample: Randomly select a minimum subset S from the dataset. Then, estimate the model: Use the subset S to estimate a model M. Next, count the inliers: Traverse all points in the dataset, calculate the error between each point and the model M. If the error is less than the threshold t, then this point is an inlier, and count the number of inliers n. Then, make an iteration judgment: If the maximum number of iterations N is reached or the number of inliers n is large enough (exceeding the preset threshold), then stop the iteration; otherwise, return to continue sampling. Finally, determine the model: Select the model with the largest number of inliers as the final estimated result.

[0069] The RANSAC algorithm has strong robustness and can effectively handle a large number of outliers and noise in the dataset because it does not rely on all data points to estimate the model but approximates the true model by finding the model with the most inliers. The RANSAC algorithm performs well when dealing with data containing noise and outliers and is a very practical parameter estimation method.

[0070] When applying the RANSAC algorithm in the present invention, 7 parameters need to be determined: the coordinates of two foci (each focus coordinate has three parameters) and a constant. And the coordinates of each laser point in the world coordinate system can construct three equations. Therefore, the minimum subset S should be 3. That is to say, each time three coordinate points are extracted from the world coordinate information for the above iteration process, a final ellipse equation can be determined. The coordinates of the two foci are extracted from this ellipse equation, and the median value of the two focus coordinates is used as the center coordinate. That is to say, a center coordinate is obtained through each world coordinate information (each laser line obtains a world coordinate information). Then, the inclination of the capillary can be obtained through the third formula:

[0071] In the formula, , and are the coordinate differences of the x-axis, y-axis, and z-axis respectively, is the angle between the capillary and the x-axis in the xy plane, is the angle between the capillary and the x-axis in the xz plane, is the comprehensive inclination, is the length of the laser line spacing, is the arcsine function.

[0072] In step 204, circular fitting is performed according to the inclination and the two world coordinate information to obtain the outer diameter of the capillary.

[0073] In some embodiments, one of the two world coordinate information is used as the outer diameter estimation coordinate information. The circular fitting according to the inclination and the two world coordinate information to obtain the outer diameter of the capillary includes: Construct a fourth ellipse equation based on the major axis and minor axis according to the inclination, where the fourth ellipse equation is:

[0074] In the formula, , and are the coordinates of the laser point on the x-axis, y-axis, and z-axis in the world coordinate system respectively, , and are the coordinates of the laser point on the x-axis, y-axis, and z-axis after rotating degrees in the xz coordinate plane respectively, , and are the coordinates of the laser point on the x-axis, y-axis, and z-axis after rotating degrees in the xy coordinate plane respectively, is the major axis, is the minor axis, is the radius of the capillary, is the angle between the capillary and the x-axis in the xy plane, is the angle between the capillary and the x-axis in the xz plane; Perform fitting on the fourth ellipse equation using the least squares method or the random sample consensus algorithm according to the outer diameter estimation coordinate information to obtain a fifth ellipse equation; Determine the diameter of the capillary according to the capillary radius in the fifth ellipse equation.

[0075] Exemplarily, an equation based on the inclination, the major axis of the ellipse, and the minor axis of the ellipse can be constructed according to the inclination of the capillary. In fact, the minor axis of the ellipse is the diameter of the capillary. This equation (the fourth ellipse equation) is:

[0076] In the formula, , and are the coordinates of the laser point on the x-axis, y-axis, and z-axis in the world coordinate system respectively. , and are the coordinates of the laser point on the x-axis, y-axis, and z-axis after rotating by degrees in the xz coordinate plane respectively. , and are the coordinates of the laser point on the x-axis, y-axis, and z-axis after rotating by degrees in the xy coordinate plane respectively. is the major axis, is the minor axis, is the capillary radius, is the angle between the capillary and the x-axis in the xy plane, is the angle between the capillary and the x-axis in the xz plane.

[0077] Actually, taking Figure 1 as an example, this equation is a coordinate system assuming that the positive direction of the z-axis coordinate is above the world coordinate system, the positive direction of the y-axis coordinate is in front, and the positive direction of the x-axis is on the right. If this coordinate system is transformed to the yz plane, then the equation will be in the following form (the ellipse equation based on the major and minor axes):

[0078] In the formula is the major axis, is the minor axis, is the capillary radius, and are the equations after transforming the ellipse to the yz plane coordinate system respectively. However, as mentioned above, when the capillary is inclined, the above equation cannot be used to express it.

[0079] Actually, the inclination of the capillary is the synthesis of two directions of inclination. One is the up and down inclination, and the other is the front and back inclination. The above two inclinations have actually been obtained through the previous steps, which are and respectively. The synthesis of the two inclinations is: , our existing two world coordinate information, one of which is used as the coordinate information for determining the capillary diameter (outer diameter estimation coordinate information), can be converted by tilting in two directions. The converted plane coordinate system is coplanar with the elliptical plane, so that the above equation can be applied.

[0080] The first conversion in the embodiment of the present invention utilizes , specifically, it is converted by the following formula:

[0081] In the formula, , and are the coordinates of the laser point on the x-axis, y-axis and z-axis in the world coordinate system respectively, , and are the coordinates of the laser point on the x-axis, y-axis and z-axis after rotating angle in the xz coordinate plane respectively.

[0082] Then, the second conversion utilizes , specifically, it utilizes the following formula:

[0083] In the formula, , and are the coordinates of the laser point on the x-axis, y-axis and z-axis after rotating angle in the xy coordinate plane respectively, is the major axis, is the minor axis, is the capillary radius, is the angle between the capillary and the x-axis in the xy plane, is the angle between the capillary and the x-axis in the xz plane.

[0084] In this way, the converted coordinate plane is coplanar with the elliptical line, and the previous equation (the fourth elliptical equation) can be used to fit the outer diameter estimation coordinate information. The fitting method can also adopt the least square method or the random sample consensus algorithm. Those skilled in the art can realize the fitting process according to the existing technology and the relatively detailed description of the foregoing process without creative labor. Therefore, it will not be elaborated. After fitting, the fifth equation is obtained, that is, the equation that makes the most points in the outer diameter estimation coordinate information on the elliptical curve. The capillary radius in this equation is used as the finally determined capillary radius.

[0085] Embodiment of the method for determining the outer diameter of a capillary tube of the present invention. First, a first image and a second image are obtained, wherein the first image and the second image respectively include laser lines generated by a line-structured laser on the capillary tube. Then, the image coordinate information of the laser lines in the images is respectively extracted from the first image and the second image, and the two image coordinate information is subjected to coordinate transformation to obtain two world coordinate information, wherein the world coordinate information is the coordinate information of the laser line in the world coordinate system. Next, according to the two world coordinate information, two positioning center coordinates are determined, and the inclination of the capillary tube is determined according to the two center coordinates, wherein the positioning center coordinate is the center coordinate of the cross-section of the capillary tube where the laser line is located. Finally, circular fitting is performed according to the inclination and the two world coordinate information to obtain the outer diameter of the capillary tube. The present invention first generates two laser lines on the capillary tube through a laser, then converts the coordinates of the laser lines in the image to the world coordinates, then determines the inclination of the capillary tube through the world coordinates, and finally determines the diameter of the capillary tube based on the inclination. Since the influence of inclination on the detection of the capillary tube diameter is considered, the diameter detection result is more accurate than the current technology.

[0086] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0087] The following is the device embodiment of the present invention. For the details not described in detail therein, reference can be made to the corresponding method embodiment above.

[0088] Figure 3 is the functional block diagram of the capillary tube outer diameter determination device provided by the embodiment of the present invention. Referring to Figure 3 , the capillary tube outer diameter determination device includes: an image acquisition module 301, a coordinate transformation module 302, a capillary tube inclination determination module 303, and a capillary tube outer diameter determination module 304, wherein: The image acquisition module 301 is used to acquire a first image and a second image, wherein the first image and the second image respectively include laser lines generated by a line-structured laser on the capillary tube; The coordinate transformation module 302 is used to respectively extract the image coordinate information of the laser lines in the first image and the second image, and perform coordinate transformation on the two image coordinate information to obtain two world coordinate information, wherein the world coordinate information is the coordinate information of the laser line in the world coordinate system; The capillary tube inclination determination module 303 is used to determine two positioning center coordinates according to the two world coordinate information, and determine the inclination of the capillary tube according to the two center coordinates, wherein the positioning center coordinate is the center coordinate of the cross-section of the capillary tube where the laser line is located; The capillary outer diameter determination module 304 is configured to perform circular fitting based on the inclination and the two world coordinate information to obtain the capillary outer diameter.

[0089] Figure 4 It is a functional block diagram of an electronic device provided by an embodiment of the present invention. As Figure 4 shown, the electronic device 4 of this embodiment includes: a processor 400 and a memory 401, and a computer program 402 that can run on the processor 400 is stored in the memory 401. When the processor 400 executes the computer program 402, the steps in the above-mentioned various capillary outer diameter determination methods and embodiments are implemented, such as Figure 1 the steps 201 to 204 shown.

[0090] Exemplarily, the computer program 402 can be divided into one or more modules / units, and the one or more modules / units are stored in the memory 401 and executed by the processor 400 to complete the present invention.

[0091] The electronic device 4 can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The electronic device 4 may include, but is not limited to, a processor 400 and a memory 401. Those skilled in the art can understand that Figure 4 merely examples of the electronic device 4 do not constitute a limitation on the electronic device 4, and it may include more or fewer components than shown in the figure, or combine certain components, or different components. For example, the electronic device 4 may further include input / output devices, network access devices, buses, etc.

[0092] The so-called processor 400 may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0093] The memory 401 may be an internal storage unit of the electronic device 4, such as a hard disk or memory of the electronic device 4. The memory 401 may also be an external storage device of the electronic device 4, such as a plug-in hard disk equipped on the electronic device 4, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. Further, the memory 401 may also include both the internal storage unit and the external storage device of the electronic device 4. The memory 401 is used to store the computer program 402 and other programs and data required by the electronic device 4. The memory 401 may also be used to temporarily store the data that has been output or will be output.

[0094] Those skilled in the art can clearly understand that, for the convenience and conciseness of description, only the above-mentioned division of each functional unit and module is used as an example. In actual applications, the above-mentioned functions can be allocated to different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction and do not limit the protection scope of the present application. The specific working processes of the units and modules in the above system can refer to the corresponding processes in the foregoing method embodiments and will not be described in detail here.

[0095] In the above embodiments, each embodiment is described with emphasis. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0096] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or by a combination of computer software and electronic hardware. Whether these functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0097] In the embodiments provided by the present invention, it should be understood that the disclosed device / electronic device and method can be implemented in other ways. For example, the device / electronic device embodiments described above are merely illustrative. For example, the division of the modules or units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the couplings or direct couplings or communication connections shown or discussed with each other can be through some interfaces. The indirect couplings or communication connections of the devices or units can be in electrical, mechanical or other forms.

[0098] The units described as separate components may or may not be physically separated. The components shown as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0099] In addition, in each embodiment of the present invention, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0100] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, to implement all or part of the processes in the above-described method embodiments of the present invention, it can also be completed by a computer program instructing relevant hardware. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-described method and device embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0101] The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A capillary outer diameter detection system, characterized in that: include: Two stripe structure lasers, two cameras and a processor; The two stripe structure lasers and the two cameras are electrically connected to the processor respectively; The laser wavelengths emitted by the two stripe structure lasers are different; When the capillary tube is located in the laser projection area of ​​the two stripe structure lasers, the two stripe structure lasers project two laser lines on the outer contour of the capillary tube; The two cameras are respectively provided with a filtering device, and the wavelengths corresponding to the filtering devices of the two cameras correspond one-to-one to the emission wavelengths of the two stripe structure lasers; When the two cameras respectively capture images containing laser lines, the processor determines the surface contour of the capillary tube through the positions of the laser lines in the two images, and determines the outer diameter of the capillary tube based on the surface contour.

2. The capillary outer diameter detection system according to claim 1, characterized in that: The two stripe structure lasers and the two cameras are located at the same height, and the horizontal spacing between the two stripe structure lasers is the same as the horizontal spacing between the two cameras.

3. A method for determining the outer diameter of a capillary tube, characterized in that: Using the capillary outer diameter detection system according to any one of claims 1 to 2, the capillary outer diameter determination method comprises: Acquire a first image and a second image, wherein the first image and the second image respectively include a laser line generated by a line structure laser on the capillary tube; Extracting image coordinate information of the laser line in the image from the first image and the second image respectively, and performing coordinate conversion on the two image coordinate information to obtain two world coordinate information, wherein the world coordinate information is the coordinate information of the laser line in the world coordinate system; Determine two positioning center coordinates according to the two world coordinate information, and determine the inclination of the capillary tube according to the two center coordinates, wherein the positioning center coordinates are the center coordinates of the capillary tube cross section where the laser line is located; A circular fitting is performed according to the inclination and the two world coordinate information to obtain the outer diameter of the capillary tube.

4. The method for determining the outer diameter of a capillary tube according to claim 3, characterized in that: The step of performing coordinate conversion on the two image coordinate information to obtain two world coordinate information includes: The image coordinate information includes multiple pixel coordinates of the laser line image. For each image coordinate information, the following steps are performed respectively: Acquire depth information, a camera intrinsic parameter matrix, and a camera extrinsic parameter matrix, wherein the intrinsic parameter matrix reflects the relationship between pixel coordinates on the camera imaging plane and coordinates in the camera coordinate system, the camera extrinsic parameter matrix reflects the relationship between the camera coordinate system and the world coordinate system, and the depth information reflects the distance from a point in the image to the camera; The image coordinate information is converted according to the camera intrinsic parameter matrix and the depth information to obtain intermediate coordinate information, wherein the intermediate coordinate information represents the coordinates of each point of the laser line in a coordinate system with the camera optical center as the coordinate origin; The intermediate coordinate information is converted according to the camera extrinsic matrix to obtain world coordinate information, wherein the world coordinate information represents the coordinates of each point of the laser line in the world coordinate system.

5. The method for determining the outer diameter of a capillary tube according to claim 4, characterized in that: The converting the image coordinate information according to the camera intrinsic parameter matrix and the depth information to obtain the intermediate coordinate information includes: The image coordinate information is converted according to the first formula, the camera intrinsic parameter matrix and the depth information to obtain the intermediate coordinate information, wherein the first formula is: In the formula, , as well as are the coordinates of the x-axis, y-axis and z-axis in the intermediate coordinate system of the laser point, is the depth information, is the internal parameter matrix, is the x-axis focal length, is the y-axis focal length, as well as are the x-axis and y-axis coordinates of the intersection of the optical axis and the image plane on the image plane, , as well as are the x-axis, y-axis, and z-axis coordinates of the laser point in the image coordinate system; The converting the intermediate coordinate information according to the camera extrinsic parameter matrix to obtain world coordinate information includes: The intermediate coordinate information is converted according to the second formula and the camera extrinsic matrix to obtain world coordinate information, wherein the second formula is: In the formula, is the rotation matrix that describes the rotation of the camera in the world coordinate system. is a vector describing the translation of the camera in the world coordinate system, , as well as They are the x-axis, y-axis, and z-axis coordinates of the laser point in the world coordinate system.

6. The method for determining the outer diameter of a capillary tube according to claim 3, characterized in that: Determining two positioning center coordinates according to the two world coordinate information, and determining the inclination of the capillary tube according to the two center coordinates, includes: Construct the equation of the first ellipse based on the focus; According to the two world coordinate information, the first ellipse equation is fitted by using a least square method or a random sampling consensus algorithm to obtain a second ellipse equation and a third ellipse equation; Determine a first focus pair and a second focus pair according to the second ellipse equation and the third ellipse equation, respectively, wherein the first focus pair and the second focus pair respectively include two foci extracted according to the second ellipse equation and the third ellipse equation; Determine first positioning center coordinates and second positioning center coordinates according to the first focus pair and the second focus pair; Calculating the difference between the first positioning center coordinates and the second positioning center coordinates to obtain a coordinate difference; The inclination of the capillary tube is determined according to the coordinate difference and the length of the laser line spacing, wherein the laser line spacing is the spacing between two laser lines on the capillary tube.

7. The method for determining the outer diameter of a capillary tube according to claim 6, characterized in that: The first ellipse equation is: In the formula, is the distance from the laser point to the first focus, is the distance from the laser point to the second focus, , as well as are the x-axis, y-axis, and z-axis coordinates of the laser point in the world coordinate system, , as well as are the coordinates of the first focus of the ellipse in the world coordinate system, respectively, the x-axis, y-axis, and z-axis. , as well as are the coordinates of the second focus of the ellipse in the world coordinate system, respectively, the x-axis, y-axis, and z-axis. is the sum constant; Determining the inclination of the capillary tube according to the coordinate difference and the laser line spacing length includes: The inclination of the capillary tube is determined according to a third formula, the coordinate difference and the laser line spacing length, wherein the third formula is: In the formula, , as well as are the x-axis, y-axis, and z-axis coordinate differences, respectively. is the angle between the capillary tube and the x-axis in the xy plane, is the angle between the capillary tube and the x-axis in the xz plane, is the comprehensive inclination, is the laser line spacing length, is the inverse sine function.

8. The method for determining the outer diameter of a capillary tube according to any one of claims 3 to 7, characterized in that: Using one of the two world coordinate information as outer diameter estimation coordinate information, and performing circular fitting according to the inclination and the two world coordinate information to obtain the outer diameter of the capillary tube, comprises: A fourth ellipse equation based on the major axis and the minor axis is constructed according to the inclination, wherein the fourth ellipse equation is: In the formula, , as well as are the x-axis, y-axis, and z-axis coordinates of the laser point in the world coordinate system, , as well as The laser point rotates in the xz coordinate plane The coordinates of the x-axis, y-axis, and z-axis after the angle, , as well as The laser point rotates in the xy coordinate plane. The coordinates of the x-axis, y-axis, and z-axis after the angle, is the long axis, is the short axis, is the capillary radius, is the angle between the capillary tube and the x-axis in the xy plane, is the angle between the capillary tube and the x-axis in the xz plane; According to the outer diameter estimation coordinate information, the fourth ellipse equation is fitted by using the least square method or the random sampling consensus algorithm to obtain the fifth ellipse equation; The capillary diameter is determined according to the capillary radius in the fifth ellipse equation.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program that can be run on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 3 to 8 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method as claimed in any one of claims 3 to 8 are implemented.

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