Track deformation offset correction method for extra-high voltage GIL / GIS in-situ detection

Abstract

The invention relates to an extra-high voltage GIL / GIS in-situ detection track deformation offset correction method, a circular track is provided with a radiation source and a detector, the center of the circular track is provided with an objective table, the objective table is provided with a coordinate calibration die body, and the coordinate calibration die body comprises a cylindrical body and two metal balls embedded in the cylindrical body; the objective table is rotated by a circle, or the radiation source and the detector are rotated by a circle along the circular orbit, images formed by multiple frames of coordinate calibration die bodies on the detector are collected in the rotation process, and projection coordinates of the two metal balls in each frame of image are obtained; the physical site corresponding to each frame of image is independently corrected, so that the influence of track deformation on the image reconstruction quality is solved, the accuracy of CT image reconstruction is improved, the system can adapt to various non-standard circular tracks, and the adaptability and flexibility of the system in different application environments are improved; and reworking or re-detection requirements caused by inaccurate geometric calibration are reduced, so that the overall detection cost is reduced.

Description

Technical Field

[0001] The invention relates to industrial CT technology, in particular to a track deformation deviation correction method for ultra-high voltage GIL / GIS in-situ detection. Background Art

[0002] GIL (Gas insulated Metalenclosed Transmission Iines), that is, gas-insulated metal transmission lines, have the characteristics of large transmission capacity, flexible spatial distribution, and small environmental impact, and have been widely used in the field of large-capacity and long-distance transmission. GIS (Gas Insulated Switchgear), that is, gas-insulated metal-enclosed switchgear, centrally installs the main circuit components, such as circuit breakers, disconnectors, grounding switches, mutual inductors, lightning arresters, etc., in a metal-enclosed shell filled with SF6 gas. This design not only reduces the footprint of the equipment, but also improves the reliability and safety of equipment operation.

[0003] Existing GIL / GIS equipment mostly adopts modular design, and it is not easy to find structural defects inside. Industrial CT equipment is needed to perform non-destructive testing and analysis of the internal structure. For example, a clamping-type pipeline CT scanning imaging device disclosed in Chinese patent document 202210581208.1 can perform CT non-destructive testing on the internal structure of the pipeline.

[0004] Industrial CT (industrial computed tomography) is a non-contact imaging technology that is widely used in materials science, biomedicine, quality control, engineering inspection and other fields. It uses X-rays to penetrate objects and constructs a three-dimensional image of the object by collecting ray intensity data at different angles. Existing process CT equipment, circular trajectory cone beam CT scanning, as an advanced imaging technology, shows unique advantages in detecting complex material structures; however, in actual applications, due to mechanical errors, the motion trajectories of the radiation source and detector are not perfect circles. This error may lead to inaccurate geometric calibration, which in turn affects the quality of CT reconstructed images. Summary of the invention

[0005] The purpose of the present invention is to provide a track deformation offset correction method for UHV GIL / GIS in-situ detection, which is used to solve the problem that the motion track deformation of the radiation source and detector of the existing industrial CT equipment affects the quality of CT reconstructed images.

[0006] In order to solve the above problems, the present invention provides a method for correcting track deformation offset of UHV GIL / GIS in-situ detection, wherein a radiation source and a detector are arranged on a circular track, a stage is placed at the center of the circular track, and a coordinate calibration model is placed on the stage, wherein the coordinate calibration model comprises a columnar body and two metal balls embedded in the columnar body, the center line of the two metal balls coincides with the center axis of the columnar body, the center axis of the stage coincides with the center axis of the columnar body, and the following steps are also included: S10, fixing the coordinate calibration model on the stage so that the columnar body is parallel to the central axis of the circular track, and the distance between the columnar body and the central axis of the circular track is a first preset value; S20, rotating the stage for one circle, or the radiation source and the detector for one circle along the circular track, during the rotation process, performing a first scan on the coordinate calibration phantom, collecting multiple frames of images formed by the coordinate calibration phantom on the detector, and obtaining the projection coordinates of the two metal balls in each frame of the image; Fitting the elliptical trajectories of the two metal balls according to the projection coordinates of the two metal balls in each frame image, According to the projection coordinates of the two metal balls in each frame of image, a Δvi of the metal ball along the short axis direction of the elliptical trajectory is set, and the first distance between the sum of the coordinate values ​​of the two metal balls along the short axis direction of the elliptical trajectory and the corresponding elliptical trajectory in the short axis direction of the corresponding elliptical trajectory is calculated respectively, and the Δvi that minimizes the sum of the two first distances in the position corresponding to each frame of image is calculated; S30, placing the object to be detected in the circular orbit and between the radiation source and the detector, rotating the stage for one circle, or the radiation source and the detector rotate along the circular orbit for one circle, and during the rotation process, collecting multiple frames of images of the object to be detected formed on the detector, and when reconstructing a three-dimensional image of the object to be detected using the images of each frame of the object to be detected, correcting each frame of the image of the object to be detected using Δvi of the corresponding position.

[0007] The track deformation deviation correction method for UHV GIL / GIS in-situ detection provided by the present invention also has the following technical features: Furthermore, the columnar body has a square cross-section with a side length of 1 cm to 2 cm, a length of 10 cm to 20 cm, and is made of polyethylene porous plastic; the two metal balls are made of the same material and have a diameter of 2 mm to 5 mm.

[0008] Furthermore, in the step S20, 120 frames of images formed by the coordinate calibration model on the detector are collected, and the interval of each collection is 3°; in the step S30, the number of frames of the image of the object to be detected collected is the same as that in the step S20.

[0009] Furthermore, between step S20 and step 30, step S21 is also included, in which the coordinate calibration phantom is rotated 90° around the central axis of the circular orbit, and step S20 is repeated to scan the coordinate calibration phantom for a second time; the coordinate calibration phantom is rotated 90° around the central axis of the circular orbit again, and step S20 is repeated to scan the coordinate calibration phantom for a third time; the coordinate calibration phantom is rotated 90° around the central axis of the circular orbit again, and step S20 is repeated to scan the coordinate calibration phantom for a fourth time; the average value of Δvi of each point obtained by the four scans is calculated, and Δvi in ​​step S30 adopts the average value of Δvi of each point obtained by the four scans.

[0010] Furthermore, in step S21, the arithmetic mean value of Δvi of each point obtained by four scans is calculated.

[0011] Furthermore, in the step S20, according to the projection coordinates of the two metal balls in each frame image, the elliptical trajectories of the two metal balls are respectively fitted using the CV2.fitEllipse function in OpenCV.

[0012] Furthermore, in step S30, when reconstructing a three-dimensional image of the object to be detected using the image of each frame of the object to be detected, the transmission matrix is ​​obtained using the GetPerspectiveTransform function in OpenCV to correct the image of each frame of the object to be detected using Δvi of the corresponding position.

[0013] The present application solves the impact of track deformation on image reconstruction quality by individually correcting the physical location corresponding to each frame of image, thereby improving the accuracy of CT image reconstruction, enabling the system to adapt to a variety of non-standard circular trajectories, and improving its adaptability and flexibility in different application environments; reducing the need for rework or re-inspection due to inaccurate geometric calibration, thereby reducing overall inspection costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a coordinate diagram of an existing cone-beam CT system; Figure 2 It is a schematic diagram of parameter errors of existing cone-beam CT systems; Figure 3 It is a schematic diagram of the coordinate projection of the metal ball before and after the circular orbit deformation; Figure 4 Schematic diagram of the coordinate projection of the metal ball before and after correction in an embodiment of the present invention; Figure 5 Schematic diagram of the metal ball coordinate projection correction process in an embodiment of the present invention; Figure 6 Schematic diagram of the structure of the coordinate calibration phantom in an embodiment of the present invention; Figure 7 Schematic diagram of position adjustment of a coordinate calibration phantom in an embodiment of the present invention. DETAILED DESCRIPTION

[0015] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0016] Industrial CT (industrial computed tomography) is a non-contact imaging technology that is widely used in materials science, biomedicine, quality control, engineering inspection and other fields. It uses X-rays to penetrate objects and constructs a three-dimensional image of the object by collecting ray intensity data at different angles. Circular trajectory geometric calibration technology is the key to ensuring that the CT system accurately reconstructs objects during imaging. Existing systems of this type usually use the "double-ball calibration" method, that is, placing two standard spheres on the source and detector paths, and scanning these two spheres to obtain geometric parameters for subsequent image reconstruction processes. However, in actual applications, due to manufacturing errors in mechanical structures or deformation of circular tracks due to wear, the moving paths of the source and detector may deviate from the ideal circular trajectory, which will lead to a decrease in the accuracy of geometric calibration, thereby affecting the quality of subsequent image reconstruction and ultimately affecting the accuracy of the detection results.

[0017] In one embodiment of the track deformation offset correction method for in-situ detection of UHV GIL / GIS of the present invention, the track deformation offset correction method for in-situ detection of UHV GIL / GIS is provided with a radiation source and a detector on a circular track, a stage is placed at the center of the circular track, a coordinate calibration model is placed on the stage, the coordinate calibration model includes a columnar body and two metal balls embedded in the columnar body, the center line of the two metal balls coincides with the center axis of the columnar body, the center axis of the stage coincides with the center axis of the columnar body, and the following steps are also included: S10, fixing the coordinate calibration model on the stage so that the columnar body is parallel to the central axis of the circular track, and the distance between the columnar body and the central axis of the circular track is a first preset value; S20, rotating the stage for one circle, or the radiation source and the detector for one circle along the circular track, during the rotation process, performing a first scan on the coordinate calibration phantom, collecting multiple frames of images formed by the coordinate calibration phantom on the detector, and obtaining the projection coordinates of the two metal balls in each frame of the image; Fitting the elliptical trajectories of the two metal balls according to the projection coordinates of the two metal balls in each frame image, According to the projection coordinates of the two metal balls in each frame of image, a Δvi of the metal ball along the short axis direction of the elliptical trajectory is set, and the first distance between the sum of the coordinate values ​​of the two metal balls along the short axis direction of the elliptical trajectory and the corresponding elliptical trajectory in the short axis direction of the corresponding elliptical trajectory is calculated respectively, and the Δvi that minimizes the sum of the two first distances in the position corresponding to each frame of image is calculated; S30, placing the object to be detected in the circular orbit and between the radiation source and the detector, rotating the stage for one circle, or the radiation source and the detector rotate along the circular orbit for one circle, and during the rotation process, collecting multiple frames of images of the object to be detected formed on the detector, and when reconstructing a three-dimensional image of the object to be detected using the images of each frame of the object to be detected, correcting each frame of the image of the object to be detected using Δvi of the corresponding position.

[0018] The present application solves the impact of track deformation on image reconstruction quality by individually correcting the physical location corresponding to each frame of image, thereby improving the accuracy of CT image reconstruction, enabling the system to adapt to a variety of non-standard circular trajectories, and improving its adaptability and flexibility in different application environments; reducing the need for rework or re-inspection due to inaccurate geometric calibration, thereby reducing overall inspection costs.

[0019] Specifically, the track deformation deviation correction method for in-situ detection of UHV GIL / GIS in this application is mainly used for Figure 1 In the actual application of the cone-beam CT system, due to the mechanical structure manufacturing equipment error, wear, or deformation of the circular track, the cone-beam CT can usually be attributed to the following Figure 2The five parameter errors shown are: the displacement errors Δu and Δv of the detector along the U and V axes, and the rotation angle errors θ, β, and η of the detector around the U, V, and X axes; in the calibration used in existing 3D image reconstruction, Δu, Δv, θ, and η are mainly calculated, and then the distance SDD between the focus and the detector, and the distance SOD between the focus and the origin of the spatial coordinate system, a total of 6 parameters, are added to the corresponding detector fixed parameters to obtain the affine matrix, correct the input image, and then use the corrected image for FDK reconstruction; the correction of each image does not take into account the circular orbit deformation, and the same Δu, Δv, θ, and η are used in the correction process of each image, resulting in inaccurate geometric calibration, which in turn affects the quality of CT reconstructed images.

[0020] Ideally, the circular orbit is a standard circle, and the projections of the centers of the two metal balls should be two standard ellipses, such as Figure 3 As shown in the two figures on the left, the elliptical trajectories of the two metal balls fitted according to the projection of the sphere center of the two metal balls coincide with the projection of the sphere center. When the circular orbit is deformed, the projection of the sphere center of the two metal balls is not a standard ellipse, such as Figure 3 As shown in the two figures on the right, the projections of the centers of the two metal balls do not completely coincide with the fitted elliptical trajectories, so the fitted elliptical trajectories can be used to correct each physical location.

[0021] When the circular orbit is deformed, the projection of the center of the two metal balls is not a standard ellipse, such as Figure 4 As shown in the two figures on the left, the projection of the center of the two metal balls does not completely coincide with the fitted ellipse trajectory. The fitted ellipse corrected by Δvi is as follows: Figure 4 As shown in the two figures on the right, the projection of the center of the two metal balls has a higher degree of coincidence with the fitted elliptical trajectory.

[0022] The metal ball coordinate projection correction process in the embodiment of the present invention is as follows: Figure 5 As shown, Figure 5 The two "cross" symbols on the left are the actual projection positions of the centers of the two metal balls, and the two ellipses are the elliptical trajectories of the two metal balls fitted according to the projection coordinates of the centers of the two metal balls in each frame image; the two "cross" symbols on the right are the corrected projection positions of the centers of the two metal balls, and after correction, the projections of the centers of the two metal balls have a higher degree of coincidence with the fitted elliptical trajectories.

[0023] The track deformation deviation correction method for UHV GIL / GIS in-situ detection provided by the present invention also has the following technical features: In one embodiment of the present application, preferably, Figure 6As shown, the cross-section of the columnar body is square with a side length of 1 cm to 2 cm, a length of 10 cm to 20 cm, for example 15 cm, and is made of polyethylene porous plastic; the two metal balls are made of the same material, with a diameter of 2 mm to 5 mm, a radius error within 5%, and a spacing greater than 8 cm, for example 10 cm.

[0024] In one embodiment of the present application, preferably, in the step S20, 120 frames of images formed by the coordinate calibration model on the detector are collected, and the interval between each collection is 3°; in the step S30, the number of frames of the image of the object to be detected collected is the same as that in the step S20.

[0025] In one embodiment of the present application, preferably, between step S20 and step 30, step S21 is further included, wherein the coordinate calibration phantom is rotated 90° around the central axis of the circular track, and step S20 is repeated to scan the coordinate calibration phantom for a second time; the coordinate calibration phantom is rotated 90° around the central axis of the circular track again, and step S20 is repeated to scan the coordinate calibration phantom for a third time; the coordinate calibration phantom is rotated 90° around the central axis of the circular track again, and step S20 is repeated to scan the coordinate calibration phantom for a fourth time; the mean of Δvi of each point obtained by the four scans is calculated, and the Δvi in ​​step S30 adopts the mean of Δvi of each point obtained by the four scans; preferably, the arithmetic mean of Δvi of each point obtained by the four scans is calculated in step S21. Figure 7 As shown, during the first scan, the coordinate calibration phantom is at position 1; during the second scan, the coordinate calibration phantom is rotated 90° around the central axis (virtual rotation axis) of the circular track (motion track) to position 2; during the third scan, the coordinate calibration phantom is rotated 90° around the central axis (virtual rotation axis) of the circular track (motion track) to position 3; during the fourth scan, the coordinate calibration phantom is rotated 90° around the central axis (virtual rotation axis) of the circular track (motion track) to position 4. Through multiple scans, the calibration of each point is more accurate and reliable.

[0026] In one embodiment of the present application, preferably, in step S20, according to the projection coordinates of the two metal balls in each frame image, the elliptical trajectories of the two metal balls are respectively fitted using CV2.fitEllipse in the OpenCV (Open Source Computer Vision Library) function.

[0027] In one embodiment of the present application, preferably, in the step S30, when the three-dimensional image of the object to be detected is reconstructed using the image of the object to be detected in each frame, the transmission matrix is ​​obtained using the GetPerspectiveTransform function in OpenCV to correct the image of the object to be detected in each frame using Δvi of the corresponding position.

[0028] Finally, it should be noted that the above 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for correcting track deformation and deviation during in-situ detection of UHV GIL / GIS, characterized in that: A radiation source and a detector are arranged on the circular track, a stage is placed at the center of the circular track, a coordinate calibration model is placed on the stage, the coordinate calibration model comprises a columnar body and two metal balls embedded in the columnar body, the center line of the two metal balls coincides with the central axis of the columnar body, the central axis of the stage coincides with the central axis of the columnar body, and the following steps are also included: S10, fixing the coordinate calibration model on the stage so that the columnar body is parallel to the central axis of the circular track, and the distance between the columnar body and the central axis of the circular track is a first preset value; S20, rotating the stage for one circle, or the radiation source and the detector for one circle along the circular track, during the rotation process, performing a first scan on the coordinate calibration phantom, collecting multiple frames of images formed by the coordinate calibration phantom on the detector, and obtaining the projection coordinates of the two metal balls in each frame of the image; Fitting the elliptical trajectories of the two metal balls according to the projection coordinates of the two metal balls in each frame image, According to the projection coordinates of the two metal balls in each frame of image, a Δvi of the metal ball along the short axis direction of the elliptical trajectory is set, and the first distance between the sum of the coordinate values ​​of the two metal balls along the short axis direction of the elliptical trajectory and the corresponding elliptical trajectory in the short axis direction of the corresponding elliptical trajectory is calculated respectively, and the Δvi that minimizes the sum of the two first distances in the position corresponding to each frame of image is calculated; S30, placing the object to be detected in the circular orbit and between the radiation source and the detector, rotating the stage for one circle, or the radiation source and the detector rotate along the circular orbit for one circle, and during the rotation process, collecting multiple frames of images of the object to be detected formed on the detector, and when reconstructing a three-dimensional image of the object to be detected using the images of each frame of the object to be detected, correcting each frame of the image of the object to be detected using Δvi of the corresponding position.

2. The method for correcting track deformation deviation according to claim 1, characterized in that: The columnar body has a square cross section with a side length of 1 cm to 2 cm and a length of 10 cm to 20 cm, and is made of polyethylene porous plastic; the two metal balls are made of the same material and have a diameter of 2 mm to 5 mm.

3. The method for correcting track deformation and deviation according to claim 1, characterized in that: In the step S20, 120 frames of images formed by the coordinate calibration phantom on the detector are collected, and the interval of each collection is 3°; in the step S30, the number of frames of the image of the object to be detected collected is the same as that in the step S20.

4. The method for correcting track deformation and deviation according to claim 3, characterized in that: Between step S20 and step 30, step S21 is also included, in which the coordinate calibration phantom is rotated 90° around the central axis of the circular orbit, and step S20 is repeated to scan the coordinate calibration phantom for a second time; the coordinate calibration phantom is rotated 90° around the central axis of the circular orbit again, and step S20 is repeated to scan the coordinate calibration phantom for a third time; the coordinate calibration phantom is rotated 90° around the central axis of the circular orbit again, and step S20 is repeated to scan the coordinate calibration phantom for a fourth time; the average value of Δvi of each point obtained by the four scans is calculated, and Δvi in ​​step S30 adopts the average value of Δvi of each point obtained by the four scans.

5. The method for correcting track deformation and deviation according to claim 4, characterized in that: In step S21, the arithmetic mean value of Δvi at each point obtained by four scans is calculated.

6. The method for correcting track deformation and deviation according to claim 1, characterized in that: In the step S20, according to the projection coordinates of the two metal balls in each frame image, the elliptical trajectories of the two metal balls are respectively fitted using the CV2.fitEllipse function in OpenCV.

7. The method for correcting track deformation and deviation according to claim 1, characterized in that: In the step S30, when reconstructing a three-dimensional image of the object to be detected using the image of each frame of the object to be detected, the transmission matrix is ​​obtained using the GetPerspectiveTransform function in OpenCV to correct the image of each frame of the object to be detected using Δvi of the corresponding position.

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