Image distortion correction method for electron beam welding process monitoring system

Abstract

The present invention relates to the technical field of image acquisition, and in particular to an image distortion correction method for an electron beam welding process monitoring system. The method comprises the following steps: image acquisition, in which an electron beam is driven to scan by an S-shaped scanning control mode, and while scanning, backscattered electron information of a target area of ​​a sample excited by the electron beam is synchronously collected; image processing, in which digital image technology is used to filter the collected image data to achieve filtering and noise reduction of the image data; and image registration, in which image registration is used to perform image registration on the processed image data to correct shifted image data. The correction method combines S-shaped scanning with image registration, thereby improving the speed of image signal acquisition and the imaging quality at different scanning speeds, and solving the problems of vertical edge distortion and low image acquisition efficiency of images collected by a traditional raster scanning mode.

Description

Technical Field

[0001] The present invention relates to the technical field of image acquisition, and in particular to an image distortion correction method for an electron beam welding process monitoring system. Background Art

[0002] Electron beam welding is a technology that uses a high-energy, high-speed electron beam to impact metal samples, causing the metal to heat and melt, forming a weld. Electron beam welding has the advantages of high power density, high processing precision, strong process adaptability, and small welding deformation. It is now widely used in aerospace, shipbuilding and other fields.

[0003] Optical observation is the most widely used traditional observation method in the welding process. However, the metal vapor generated during the welding process is very easy to evaporate on the optical lens, and evaporation will occur on the sample surface, which is not conducive to long-term observation. Electron optical observation has the advantages of high sensitivity to sample surface morphology and suitability for high metal vapor, and has become one of the important development directions in the field of online observation of electron beam welding.

[0004] At present, although the electron optical observation system has overcome the shortcomings of the traditional optical observation system, the conventional electron optical observation system has low image acquisition efficiency, poor image signal-to-noise ratio, and imaging quality that is susceptible to electromagnetic interference. It is difficult to completely replace the traditional optical observation system and apply it to actual production activities. The traditional raster scanning imaging method, due to the limited response time of the scanning coil system and the electronic sensor system, causes a deviation between the actual position and the target position of the electron beam during the flyback motion, resulting in edge distortion of the vertical edge of the scanned image. Although the distortion of the image edge can be reduced by increasing the dwell time of the acquisition pixel points, it will also increase the total image acquisition time and electron injection dose. At the same time, the raster scanning imaging method cannot meet the high real-time requirements in the electron beam welding scenario, and the edge distortion of the image will also affect the imaging quality. Summary of the Invention

[0005] The purpose of the present invention is to provide an image distortion correction method for an electron beam welding process monitoring system. The method has the advantages of fast image acquisition speed and high image signal-to-noise ratio, and solves the technical problems of image edge distortion and low acquisition efficiency in conventional electron beam welding process monitoring systems in actual application scenarios.

[0006] To achieve the above object, the present invention provides an image distortion correction method for an electron beam welding process monitoring system, comprising the following steps:

[0007] Image acquisition, driving the electron beam to scan by an S-shaped scanning control method, and while scanning, synchronously collecting backscattered electron information of the target area of ​​the sample excited by the electron beam;

[0008] Image processing, using digital image technology to filter the collected image data to achieve filtering and noise reduction of the image data;

[0009] Image registration: using image registration technology to perform image registration on the processed image data and correct the shifted image data.

[0010] The image acquisition function is realized by a scanning signal control module, a digital-to-analog converter, a deflection coil driving module, a deflection coil, a backscattered electron receiving sensor, an image signal conditioning module, an analog-to-digital converter and a synchronous data acquisition module.

[0011] The specific steps of image acquisition, which involves driving the electron beam to scan by an S-shaped scanning control method and simultaneously acquiring backscattered electron information of a target area of ​​the sample excited by the electron beam, are as follows:

[0012] The scanning signal control module generates a scanning signal, transmits the scanning signal to a digital-to-analog converter, and performs digital-to-analog conversion on the scanning signal through the digital-to-analog converter;

[0013] Afterwards, the converted scanning signal is input to a deflection coil driving module, and the deflection coil is driven by the deflection coil driving module, so that the deflection coil controls the electron beam to scan the target area of ​​the sample point by point and line by line;

[0014] While scanning the target area, if the backscattered electron receiving sensor detects backscattered electron information, the backscattered electron information is transmitted to the image signal conditioning module for image signal conditioning;

[0015] After the image signal conditioning is completed, the image signal is transmitted to an analog-to-digital converter, and the image signal is converted into digital form by the analog-to-digital converter;

[0016] After the analog-to-digital conversion is completed, the synchronous data acquisition module collects pixel information and arranges the pixel information into an image in a scanning order and stores it.

[0017] The image processing function is realized by an image data filtering and noise reduction module and an image data storage module.

[0018] The image processing uses digital image technology to filter and reduce noise on the collected image data. The specific steps for implementing the filtering process on the image data are as follows:

[0019] The image data filtering and noise reduction module is used to filter the salt and pepper noise in the image data by using a median filter noise reduction method;

[0020] Then, the image data from which the salt and pepper noise is removed is further filtered using a bilateral filtering method;

[0021] After filtering, the processed image data is transmitted to an image data storage module for storage.

[0022] The image registration function is realized by the image pixel shift registration module and the HDMI display driver module.

[0023] The image registration uses image registration technology to perform image registration on the processed image data, and the specific steps of correcting the shifted image data are as follows:

[0024] Performing image registration on the filtered image data through an image pixel shift registration module to complete correction of the shifted image;

[0025] After correction, the corrected image data is transmitted to the HDMI display driver module, so that the HDMI display driver module can perform efficient and clear imaging display on the image data.

[0026] The present invention discloses an image distortion correction method for an electron beam welding process monitoring system, comprising the following steps: image acquisition, wherein an electron beam is driven to scan using an S-shaped scanning control mode, and backscattered electron information of a target area of ​​a sample excited by the electron beam is simultaneously collected during the scanning; image processing, wherein digital image technology is used to filter and reduce noise on the collected image data, thereby filtering the image data; and image registration, wherein image registration is performed on the processed image data using image registration technology to correct any shifted image data. The correction method utilizes a combination of S-shaped scanning and image registration, wherein the electron beam is driven to scan using the S-shaped scanning mode, enabling rapid and efficient scanning of the target area of ​​the sample, while simultaneously collecting backscattered electron information excited by the electron beam. After image acquisition is completed, image registration technology is used to filter and register the original image to improve the signal-to-noise ratio of the image. The combination of S-shaped scanning and image registration can solve the problems of vertical edge distortion and low image acquisition efficiency in images acquired using traditional raster scanning methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0028] Figure 1 This is a flowchart of the image distortion correction method of the electron beam welding process monitoring system according to the first embodiment of the present invention.

[0029] Figure 2 This is a diagram of the specific steps of image acquisition of the image distortion correction method of the electron beam welding process monitoring system of the first embodiment of the present invention, which drives the electron beam to scan through an S-shaped scanning control method, and while scanning, synchronously collects the backscattered electron information of the target area of ​​the sample excited by the electron beam.

[0030] Figure 3 This is a diagram of the specific steps of image processing of the image distortion correction method of the electron beam welding process monitoring system of the first embodiment of the present invention, which uses digital image technology to filter and reduce noise on the collected image data to achieve filtering processing of the image data.

[0031] Figure 4 This is a diagram of the specific steps of image registration of the image distortion correction method of the electron beam welding process monitoring system of the first embodiment of the present invention, which uses image registration technology to perform image registration on the processed image data and correct the shifted image data.

[0032] Figure 5 1 is a schematic structural diagram of an electron beam welding process monitoring system according to a first embodiment of the present invention.

[0033] Figure 6 This is a principle block diagram of the electron beam welding process monitoring system according to the first embodiment of the present invention.

[0034] Figure 7 This is a principle block diagram of the image acquisition part of the first embodiment of the present invention.

[0035] Figure 8 4 is a flowchart of image shift registration according to the first embodiment of the present invention.

[0036] Figure 9 1 is a waveform diagram of X deflection scanning control according to the first embodiment of the present invention.

[0037] Figure 10 This is a Y deflection scanning control waveform diagram of the first embodiment of the present invention. DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0039] First embodiment:

[0040] See also Figures 1 to 10 The present invention provides an image distortion correction method for an electron beam welding process monitoring system, comprising the following steps:

[0041] S1. Image acquisition: driving the electron beam to scan by an S-shaped scanning control method, and while scanning, synchronously acquiring backscattered electron information of the target area of ​​the sample excited by the electron beam.

[0042] Specifically, the image acquisition function is implemented by a scanning signal control module, a digital-to-analog converter, a deflection coil driving module, a deflection coil, a backscattered electron receiving sensor, an image signal conditioning module, an analog-to-digital converter, and a synchronous data acquisition module. The image acquisition is driven to scan the electron beam through an S-shaped scanning control method, and while scanning, the backscattered electron information of the target area of ​​the sample excited by the electron beam is synchronously collected in the following specific steps:

[0043] S11, generating a scanning signal by a scanning signal control module, transmitting the scanning signal to a digital-to-analog converter, and performing digital-to-analog conversion on the scanning signal by the digital-to-analog converter;

[0044] S12: Afterwards, the converted scanning signal is input to a deflection coil driving module, and the deflection coil driving module drives the deflection coil, so that the deflection coil controls the electron beam to scan the target area of ​​the sample point by point and line by line;

[0045] S13, while scanning the target area, if the backscattered electron receiving sensor detects backscattered electron information, transmitting the backscattered electron information to the image signal conditioning module for image signal conditioning;

[0046] S14, after the image signal conditioning is completed, transmitting the image signal to an analog-to-digital converter, and performing analog-to-digital conversion on the image signal through the analog-to-digital converter;

[0047] S15. After the analog-to-digital conversion is completed, the synchronous data acquisition module collects pixel information and arranges the pixel information into an image in a scanning order and stores it.

[0048] S2. Image processing: using digital image technology to perform filtering processing on the collected image data to achieve filtering and noise reduction of the image data.

[0049] Specifically, the image processing function is implemented by an image data filtering and noise reduction module and an image data storage module. The image processing uses digital image technology to filter and reduce noise on the collected image data. The specific steps for implementing the filtering processing of the image data are as follows:

[0050] S21, using an image data filtering and noise reduction module to first perform median filtering on the collected image data to filter salt and pepper noise in the image data;

[0051] S22, further filtering the image data from which the salt and pepper noise is removed by using a bilateral filtering method;

[0052] S23. After filtering, the processed image data is transmitted to an image data storage module for storage.

[0053] S3. Image registration: performing image registration on the processed image data using image registration technology, and correcting the shifted image data.

[0054] Specifically, the image registration function is implemented by the image pixel shift registration module and the HDMI display driver module. The image registration uses image registration technology to perform image registration on the processed image data. The specific steps of correcting the shifted image data are as follows:

[0055] S31, performing image registration on the filtered image data through an image pixel shift registration module to complete correction of the shifted image;

[0056] S32. After correction, the corrected image data is transmitted to an HDMI display driver module, so that the HDMI display driver module can perform efficient and clear imaging display on the image data.

[0057] The image registration includes image displacement calculation and image displacement correction, wherein the image displacement calculation is to shift the image to be registered within a preset range and obtain a shifted image set, and the image noise component of each element image of the shifted image set is estimated to obtain the noise component curve of the shifted image set, and then the relative displacement of the image to be registered is obtained by locating the minimum value of the noise component curve; the image displacement correction is to expand the two-dimensional image into a one-dimensional discrete image signal after completing the image displacement calculation, and compensate for the response lag by shifting the one-dimensional discrete image signal forward or backward according to the displacement, and then reconstruct the two-dimensional image according to the S-shaped scanning control strategy to achieve displacement correction of the registered image.

[0058] When using the image distortion correction method of an electron beam welding process monitoring system of this embodiment, this patent is a set of electron beam welding process monitoring system built on the basis of a vacuum electron beam welder, and based on this monitoring system, the image distortion of traditional imaging is corrected. The system mainly consists of two parts, namely the image acquisition part and the image processing part (scanning image distortion correction). The implementation of the two parts is mainly based on Figure 6The schematic diagram of the scanning imaging system shown in the figure above demonstrates its principle implementation. This system primarily utilizes the principles of electron optical imaging, controlling the electron beam to excite object characterization information (backscattered electron signals). A backscattered electron collector then converts the electron signals into weak voltage signals. After signal conditioning and analog-to-digital conversion, the voltage signals are transmitted to the digital control system (FPGA and CPU). The digital control system then filters and registers the collected information, generating a visual sample image and displaying the captured image information in real time, enabling online observation of the electron beam processing process.

[0059] (1) The image acquisition part mainly completes the acquisition of the backscattered electron signal of the target area of ​​the sample, providing a stable, high frame rate, and high signal-to-noise ratio data source for the image filtering and noise reduction part. The implementation of this part of the function is mainly completed by the scanning signal control module, digital-to-analog converter, deflection coil driver module, deflection coil, backscattered electron receiving sensor, image signal conditioning module, analog-to-digital converter and synchronous data acquisition module. The scanning signal is generated by the scanning signal control module, and after digital-to-analog conversion, it is input into the deflection coil driver module, thereby driving the scanning coil to control the electron beam to scan the target area point by point and line by line. While scanning the target area, the backscattered electron sensor detects the backscattered electron information and transmits the backscattered electron information to the image signal conditioning module. After completing the image signal conditioning and analog-to-digital conversion, the synchronous data acquisition module collects the pixel information and arranges it into an image in the scanning order and stores it.

[0060] The scanning imaging strategy of this patent adopts an efficient S-type scanning control strategy, and the scanning waveform is as follows: Figure 9 、 Figure 10 As shown in the figure, compared with raster scanning, S-shaped scanning has a shorter motion path and less injected electron dose. In addition, due to its unique scanning motion mode, S-shaped scanning does not have the jump back motion of the electron beam probe, thereby avoiding the feedback delay. Since the change in the scanning edge direction is relatively slow, the edge of the image collected by the S-shaped scanning method will not be distorted. Compared with raster scanning, the control strategy of S-shaped scanning is not complicated and the implementation difficulty is low. Moreover, since there is no need to increase the feedback delay, the total acquisition time of the scanning imaging can be reduced, and the imaging system can have real-time performance and high efficiency of image acquisition.

[0061] (2) Image processing: Image processing includes image filtering and image shift registration.

[0062] In image filtering processing, digital image technology is mainly used to complete the filtering and denoising of the acquired image data, improve the image quality based on the original acquired image, and provide a source image with a high signal-to-noise ratio for subsequent image registration. The functions of this part are mainly implemented by modules such as the image data filtering and denoising module and the image data storage module.

[0063] In the image registration part, image registration technology is used to register the processed image. After the image registration is completed, a sample image with high frame rate, high signal-to-noise ratio and low noise interference can be obtained. The function of this part is mainly completed by the image pixel shift registration module and the HDMI display driver module. Since the high-speed acquisition method will bring about pixel shift and image blur problems, the image registration part mainly completes the correction of the shifted image to achieve efficient and clear imaging. This part is mainly implemented by using the self-developed image registration algorithm to correct the shifted image.

[0064] In summary, this correction method uses a combination of S-shaped scanning and image registration. By driving the electron beam through an S-shaped scanning method, it can quickly and efficiently scan the target area of ​​the sample, while simultaneously collecting information about backscattered electrons stimulated by the electron beam. After image acquisition is completed, image registration technology is used to filter and register the original image to improve the image's signal-to-noise ratio. This combination of S-shaped scanning and image registration can solve the problems of vertical edge distortion and low image acquisition efficiency in traditional raster scanning methods.

[0065] The above disclosure is merely one or more preferred embodiments of the present application and is not intended to limit the scope of the present application. A person skilled in the art will understand that all or part of the processes of the above embodiments and equivalent changes made in accordance with the claims of the present application are still within the scope of the present application.

Claims

1. A method for correcting image distortion in an electron beam welding process monitoring system, characterized in that: The following steps are involved: Image acquisition, driving the electron beam to scan by an S-shaped scanning control method, and while scanning, synchronously collecting backscattered electron information of the target area of ​​the sample excited by the electron beam; Image processing, using digital image technology to filter the collected image data to achieve filtering and noise reduction of the image data; Image registration, using image registration technology to perform image registration on the processed image data and correct the shifted image data; The image acquisition is realized by a scanning signal control module, a digital-to-analog converter, a deflection coil driving module, a deflection coil, a backscattered electron receiving sensor, an image signal conditioning module, an analog-to-digital converter and a synchronous data acquisition module; The specific steps of the image acquisition, which involves driving the electron beam to scan by an S-shaped scanning control method and synchronously acquiring backscattered electron information of a target area of ​​the sample excited by the electron beam during scanning, are as follows: The scanning signal control module generates a scanning signal, transmits the scanning signal to a digital-to-analog converter, and performs digital-to-analog conversion on the scanning signal through the digital-to-analog converter; Afterwards, the converted scanning signal is input to a deflection coil driving module, and the deflection coil is driven by the deflection coil driving module, so that the deflection coil controls the electron beam to scan the target area of ​​the sample point by point and line by line; While scanning the target area, if the backscattered electron receiving sensor detects backscattered electron information, the backscattered electron information is transmitted to the image signal conditioning module for image signal conditioning; After the image signal conditioning is completed, the image signal is transmitted to an analog-to-digital converter, and the image signal is converted into digital form by the analog-to-digital converter; After the analog-to-digital conversion is completed, the synchronous data acquisition module collects pixel information and arranges the pixel information into an image in a scanning order and stores it.

2. The image distortion correction method for an electron beam welding process monitoring system according to claim 1, wherein: The image processing function is realized by the image data filtering and noise reduction module and the image data storage module.

3. The image distortion correction method for an electron beam welding process monitoring system according to claim 2, wherein: The image processing uses digital image technology to filter and reduce noise on the collected image data. The specific steps for implementing the filtering and reducing noise on the image data are as follows: The image data filtering and noise reduction module is used to filter the salt and pepper noise in the image data by using a median filter noise reduction method; Then, the image data from which the salt and pepper noise is removed is further filtered using a bilateral filtering method; After filtering, the processed image data is transmitted to an image data storage module for storage.

4. The image distortion correction method for an electron beam welding process monitoring system according to claim 1, wherein: The image registration is implemented by an image pixel shift registration module and an HDMI display driver module.

5. The image distortion correction method for an electron beam welding process monitoring system according to claim 4, wherein: The image registration uses image registration technology to perform image registration on the processed image data, and the specific steps of correcting the shifted image data are: Performing image registration on the filtered image data through an image pixel shift registration module to complete correction of the shifted image; After correction, the corrected image data is transmitted to the HDMI display driver module, so that the HDMI display driver module can perform efficient and clear imaging display on the image data.

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