Image distortion correction method of electron beam welding process monitoring system

Abstract

The invention relates to the technical field of image acquisition, in particular to an image distortion correction method of an electron beam welding process monitoring system, which comprises the following steps of: acquiring an image, carrying out driving scanning on an electron beam in an S-shaped scanning control mode, and carrying out image distortion correction on the electron beam while scanning; synchronously collecting back scattering electronic information of a target area of the sample excited by the electron beam; image processing: carrying out filtering processing on the acquired image data by using a digital image technology to realize filtering and noise reduction on the image data; image registration: performing image registration on the processed image data by adopting an image registration technology, and correcting the shifted image data, and the correction method adopts a mode of combining S-shaped scanning and image registration, so that the image signal acquisition speed and the imaging quality at different scanning speeds can be improved; the problems of vertical edge distortion and low image acquisition efficiency of an image acquired by a traditional grating type scanning mode are solved.

Description

Technical Field

[0001] The 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 to heat and melt the metal to form 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 can easily 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 electronic optical observation system has overcome the shortcomings of the traditional optical observation system, the conventional electronic 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 grating 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, the total image acquisition time and electron injection dose will also increase. At the same time, the grating 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 and scanning the electron beam 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 while scanning;

[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, driving and scanning the electron beam by an S-shaped scanning control method, and synchronously acquiring backscattered electron information of the target area of ​​the sample excited by the electron beam during scanning, 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 acquires pixel point information and arranges the pixel point information into an image in a scanning order for storage.

[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 denoising module is used to first perform median filtering and denoising on the collected image data to filter the salt and pepper noise in the image data;

[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 an image pixel shift registration module and an 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 image data after filtering 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 image distortion correction method of an electron beam welding process monitoring system of the present invention comprises the following steps: image acquisition, driving and scanning the electron beam through an S-shaped scanning control mode, and synchronously acquiring the backscattered electron information of the target area of ​​the sample excited by the electron beam while scanning; image processing, filtering and denoising the acquired image data using digital image technology to realize filtering processing of the image data; image registration, image registration technology is used to perform image registration on the processed image data, and the shifted image data is corrected. The correction method adopts a combination of S-shaped scanning and image registration, and drives the electron beam to scan through an S-shaped scanning mode, which can quickly and efficiently scan the target area of ​​the sample, and synchronously acquire the backscattered electron information excited by the electron beam while scanning. After the image acquisition is completed, the image registration technology is used to perform image filtering and image registration on the original image to improve the signal-to-noise ratio of the image. By adopting a combination of S-shaped scanning and image registration, the problem of vertical edge distortion of the image acquired by the traditional grating scanning mode and the problem of low image acquisition efficiency can be solved. 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 drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

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

[0029] Figure 2 This is a specific step diagram of the 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 acquires the backscattered electron information of the target area of ​​the sample excited by the electron beam.

[0030] Figure 3 This is a specific step diagram of the 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 It is a structural schematic diagram of the electron beam welding process monitoring system of the first embodiment of the present invention.

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

[0034] Figure 7 It 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] Fig. 9 1 is a waveform diagram of X deflection scanning control according to the first embodiment of the present invention.

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

[0038] 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 construed 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 and scanning the electron beam 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 while scanning.

[0042] Specifically, 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. The image acquisition drives the electron beam to scan by 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. The specific steps are as follows:

[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, after that, 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;

[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 acquires 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 filter 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:

[0050] S21, using an image data filtering and noise reduction module to first perform median filtering and noise reduction on the collected image data to filter the 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, transmitting the processed image data to an image data storage module for storage.

[0053] S3. Image registration: using image registration technology to perform image registration on the processed image data and correct the shifted image data.

[0054] Specifically, the image registration function is implemented by an image pixel shift registration module and an HDMI display driver module. The image registration uses an 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 image data after filtering through an image pixel shift registration module to complete correction of the shifted image;

[0056] S32, after correction, transmitting the corrected image data 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 noise component curve of the shifted image set is obtained by estimating the image noise component of each element image 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 welding machine, and based on the monitoring system, the image distortion of traditional imaging is corrected. The system is mainly composed of two parts, namely, an image acquisition part and an 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 FIG. 1 is implemented. In the implementation of this system, the system mainly utilizes the principle of electron optical imaging, controls the electron beam to excite the object characterization information (backscattered electron signal), and then uses the backscattered electron collector to convert the electron signal into a weak voltage signal. The voltage signal is transmitted to the digital control system (FPGA and CPU) after signal conditioning, analog-to-digital conversion, etc. After that, the digital control system generates a visualized sample image and displays the collected image information in real time by filtering and registering the collected information, thereby realizing 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, and provides 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, the digital-to-analog converter, the deflection coil driving module, the deflection coil, the backscattered electron receiving sensor, the image signal conditioning module, the analog-to-digital converter, and the synchronous data acquisition module. The scanning signal is generated by the scanning signal control module, and after the digital-to-analog conversion, it is input into the deflection coil driving 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. The scanning waveform is as follows: Fig. 9 , Fig.10 As shown in the figure, compared with grating 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 flyback 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 grating 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 flyback delay, the total acquisition time of 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 realized 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 realized by the image pixel shift registration module and the HDMI display driver module. Since the high-speed acquisition method will cause pixel shift and image blur, the image registration part mainly completes the correction of the shifted image to achieve efficient and clear imaging. This part is mainly realized by using the self-developed image registration algorithm to correct the shifted image.

[0064] In summary, the correction method adopts a combination of S-type scanning and image registration. By driving the electron beam to scan in an S-type scanning manner, the target area of ​​the sample can be scanned quickly and efficiently, and the backscattered electron information excited by the electron beam can be collected synchronously while scanning. After the image is acquired, the image registration technology is used to perform image filtering and image registration on the original image to improve the signal-to-noise ratio of the image. By adopting a combination of S-type scanning and image registration, the problem of vertical edge distortion of the image acquired by the traditional raster scanning method and the problem of low image acquisition efficiency can be solved.

[0065] What is disclosed above is only one or more preferred embodiments of the present application, and cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiments and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. An image distortion correction method for an electron beam welding process monitoring system, characterized in that: The following steps are involved: Image acquisition, driving and scanning the electron beam 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 while scanning; 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.

2. The image distortion correction method of the electron beam welding process monitoring system according to claim 1, characterized in that: 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.

3. The image distortion correction method of the electron beam welding process monitoring system according to claim 2, characterized in that: The specific steps of the image acquisition, driving and scanning the electron beam by an S-shaped scanning control method, and synchronously acquiring the backscattered electron information of the 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 acquires pixel point information and arranges the pixel point information into an image in a scanning order for storage.

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

5. The image distortion correction method of the electron beam welding process monitoring system according to claim 4, characterized in that: 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 on the image data are as follows: The image data filtering and denoising module is used to first perform median filtering and denoising on the collected image data to filter the salt and pepper noise in the image data; 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.

6. The image distortion correction method of the electron beam welding process monitoring system according to claim 1, characterized in that: The image registration function is realized by the image pixel shift registration module and the HDMI display driver module.

7. The image distortion correction method of the electron beam welding process monitoring system according to claim 6, characterized in that: 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 image data after filtering 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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