Ray detection method and system for workpiece with large thickness ratio

Abstract

The invention relates to a ray detection method and system for a workpiece with a large thickness ratio, belongs to the technical field of ray nondestructive detection, and solves the problem of inaccurate workpiece quality judgment caused by poor quality of a ray image obtained in the prior art. The method comprises the following steps: setting a series of ray energies with different magnitudes according to the maximum thickness, the minimum thickness and a workpiece material of a to-be-detected workpiece; performing transillumination on the workpiece to be detected by adopting the series of ray energy to obtain ray images under different ray energy; based on wavelet analysis, performing image fusion on the ray images under different ray energies to obtain a fused image; and carrying out image enhancement processing on the fused image to obtain an enhanced fused image for judging the quality of the to-be-detected workpiece. According to the invention, the high-efficiency detection of the workpiece with the large thickness ratio is realized, the obtained ray image can completely and clearly present the structural information of the workpiece, and the improvement of the accuracy of the quality judgment of the workpiece is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of radiographic nondestructive testing, and in particular to a radiographic testing method and system for workpieces with a large thickness ratio. Background Art

[0002] Digital radiographic nondestructive testing technology has been widely used in the industrial field. By using X-rays to perform transillumination imaging of workpieces, the quality of the workpieces can be judged based on the radiographic images, and nondestructive testing can be performed on the workpieces. Due to the limited dynamic range of detector imaging, when the equivalent thickness of different parts of the workpiece vary greatly, such as in cases of complex structures, large thickness differences, and large differences in material density, it is impossible to fully present the entire workpiece structural information under a single energy. When the radiation energy meets the exposure requirements for the thicker parts of the workpiece, the thinner parts will be overexposed. When the radiation energy meets the exposure requirements for the thinner parts of the workpiece, the thicker parts will be underexposed. As a result, the workpiece structural information is missing from the imaging results, affecting the accuracy of the workpiece quality judgment.

[0003] Existing radiographic inspection methods for workpieces with large thickness ratios include zoned radiography, thickness compensation, and variable energy radiography. The zoned radiography divides the workpiece into different regions and performs radiographic imaging based on the conditions of each region. This method is complex and inefficient. The thickness compensation method uses the same or similar material as the workpiece to compensate for thickness in areas with smaller thicknesses. This method requires material preparation, is inefficient, and defects in the compensation material can lead to misjudgments of the workpiece. The variable energy radiography method uses different radiation energies to obtain radiographic images of workpieces with different thickness ranges and then uses weighted image fusion to obtain the final image. However, this weighted fusion process causes the image grayscale range to exceed the display device's capabilities, making the fused image incomplete, which in turn affects the accuracy of workpiece quality judgments. Summary of the Invention

[0004] In view of the above analysis, an embodiment of the present invention aims to provide a method and system for X-ray detection of workpieces with a large thickness ratio, so as to solve the problem that the X-ray image quality obtained by the existing X-ray detection method for workpieces with a large thickness ratio is poor, resulting in inaccurate workpiece quality judgment.

[0005] In one aspect, an embodiment of the present invention provides a method for radiographic inspection of a workpiece having a large thickness ratio, the method comprising:

[0006] Set a series of different ray energies according to the maximum thickness, minimum thickness and material of the workpiece to be measured;

[0007] The workpiece to be tested is respectively illuminated using the series of ray energies to obtain ray images under different ray energies;

[0008] Based on wavelet analysis, the ray images under different ray energies are fused to obtain a fused image;

[0009] Performing image enhancement processing on the fused image to obtain an enhanced fused image for use in judging the quality of the workpiece to be measured.

[0010] Based on the further improvement of the above method, the image fusion of the radiographic images at different ray energies based on wavelet analysis to obtain a fused image includes the following steps:

[0011] Performing wavelet transform on each of the radiation images at different radiation energies to obtain wavelet coefficients at different scales and positions;

[0012] For each wavelet coefficient at each scale and position, the coefficient with the largest absolute value is selected from the wavelet coefficients at the scale and position corresponding to each ray image as the fused coefficient;

[0013] The fused coefficients are transformed through inverse wavelet transform to reconstruct the image and obtain the fused image.

[0014] Based on a further improvement of the above method, the image enhancement processing on the fused image includes:

[0015] Performing color scale mapping on the fused image so that the grayscale range of the fused image is adjusted to the displayable grayscale range of the display device;

[0016] The contrast enhancement process is performed on the fused image after the color scale mapping to obtain an enhanced fused image.

[0017] Based on the further improvement of the above method, gamma transform is used to perform color scale mapping on the fused image. The formula of the gamma transform is:

[0018] s=c(r+ε) γ ;

[0019] Where s is the pixel value on the output image; r is the pixel value on the original image; ε is the offset; γ is the gamma value, which is used to control the area and degree of image grayscale stretching; c is a constant.

[0020] Based on the further improvement of the above method, the contrast-limited adaptive histogram equalization algorithm is used to perform contrast enhancement on the fused image after color level mapping.

[0021] Based on the further improvement of the above method, a series of different radiation energies are set according to the maximum thickness, minimum thickness and material of the workpiece to be measured, including:

[0022] Testing the detector to obtain a corresponding relationship between a grayscale value detected by the detector and the energy of the ray emitted by the ray source when there is no object between the ray source and the detector;

[0023] Determine a series of expected grayscale values ​​corresponding to different thicknesses according to the maximum grayscale value detected by the detector, the maximum thickness and the minimum thickness of the workpiece to be measured;

[0024] Determining the expected ray energy corresponding to the expected grayscale values ​​corresponding to a series of different thicknesses according to the corresponding relationship;

[0025] Based on the radiation energy attenuation formula, a series of radiation energies of different sizes are calculated according to the workpiece material of the workpiece to be measured and the expected radiation energies corresponding to the series of different thicknesses.

[0026] Based on the further improvement of the above method, the ray energy attenuation formula is:

[0027] I=I0*e -μx ;

[0028] Where I0 is the energy intensity of the ray when it reaches the surface of the object, e is a natural constant, μ is the linear attenuation coefficient, which is determined by the material of the workpiece to be measured; x is the thickness of the object, and I is the energy intensity of the ray after passing through the object.

[0029] Based on a further improvement of the above method, the method of determining a series of expected grayscale values ​​corresponding to different thicknesses according to the maximum grayscale value of the detector and the maximum and minimum thicknesses of the workpiece to be measured includes:

[0030] According to the maximum gray value of the detector, the gray value interval is set to [P1·I max ,P2·I max ]; among them, I max is the maximum grayscale value of the detector; P1 and P2 are percentages, and 0<P1<P2<100%;

[0031] Set the gray value corresponding to the minimum thickness of the workpiece to be measured to P1·I max The maximum thickness of the workpiece to be measured corresponds to the gray value P2·I max , the grayscale values ​​corresponding to other thicknesses between the minimum thickness and the maximum thickness of the workpiece to be measured are in the grayscale value interval [P1·I max ,P2·I max ]Interpolation values ​​are selected to determine a series of expected grayscale values ​​corresponding to different thicknesses.

[0032] Based on the further improvement of the above method, P1 and P2 meet the following value ranges:

[0033] 10%≤P1≤30%; 70%≤P2≤90%.

[0034] On the other hand, an embodiment of the present invention provides a radiographic inspection system for workpieces with a large thickness ratio, the system comprising:

[0035] The radiation energy calculation module sets a series of different radiation energies according to the maximum thickness, minimum thickness and material of the workpiece to be measured;

[0036] A radiographic imaging device, wherein the radiographic imaging system comprises a radiation source and a detector, wherein the radiation source respectively uses the series of radiation energies to transilluminate the workpiece to be measured, and the detector senses the radiation that penetrates the workpiece to be measured and generates radiation images at different radiation energies;

[0037] An image processing module includes an image fusion module and an image enhancement module, wherein the image fusion module fuses the radiation images under different radiation energies based on wavelet analysis to obtain a fused image, and the image enhancement module performs image enhancement processing on the fused image to obtain an enhanced fused image to judge the quality of the workpiece to be measured.

[0038] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0039] 1. In the present invention, for a workpiece with a large thickness ratio and large differences in equivalent thickness at different parts, a series of different radiation energies are used to perform transillumination imaging on the workpiece. Then, the radiation images are fused based on wavelet analysis, so that the fused image contains information from radiation images of each energy. The complete structural information of the workpiece can be presented on a single image without the need for operations such as partitioned transillumination and thickness compensation. The operation is simple and efficient. After obtaining the fused image, the fused image is enhanced to enhance the details and contrast of the image, so that the structural information of the workpiece is displayed clearly and completely, which is conducive to improving the accuracy of workpiece quality judgment.

[0040] Among them, image fusion based on wavelet analysis can more effectively process the local features and overall structure in the image, thereby retaining more image details. Compared with the weighted summation image fusion method, it can more effectively extract and fuse the key information in the image. Image fusion based on wavelet analysis can better control the grayscale value of the fused image to keep it within a reasonable display range.

[0041] 2. In this invention, we consider that image fusion will increase the grayscale value of the image to a certain extent, resulting in weak image contrast and an inability to fully and clearly present the workpiece's structural information. Therefore, during the image enhancement process, we first perform color mapping on the fused image to adjust the image's grayscale range, and then enhance the image's contrast to obtain an image that fully and clearly presents the workpiece's structural information.

[0042] 3. In the present invention, energy is adaptively selected for radiographic imaging according to the workpiece structure, and the radiation energy is designed through grayscale value testing and radiation energy attenuation formula, thereby achieving precise energy control and scientific calculation, reducing errors and radiation risks, and improving the accuracy, adaptability and safety of detection.

[0043] Specifically, in the present invention, considering that different detectors respond differently to the same energy, the detectors are grayscale tested in advance to improve the adaptability of the detection method. Then, combined with the radiation energy attenuation formula, a quantitative relationship between the image grayscale value and the radiation energy can be established. Then, according to the maximum thickness, minimum thickness and workpiece material of the workpiece to be measured, a series of radiation energies of different sizes are set to match the radiation energy with the actual situation of the workpiece to be measured, ensuring that the structures at different thickness positions of the workpiece can be clearly displayed on the radiation image, reducing the detection error caused by improper selection of radiation energy, thereby improving the accuracy of detection. At the same time, through precise energy design, the use of radiation can be optimized and unnecessary radiation can be reduced.

[0044] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0046] Figure 1 The figure is a flow chart of a method for radiographic inspection of a workpiece with a large thickness ratio according to an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0048] A specific embodiment of the present invention discloses a method for detecting a workpiece with a large thickness ratio. Figure 1 The method of the present invention comprises:

[0049] Step 1: Set a series of different radiation energies according to the maximum thickness, minimum thickness and material of the workpiece to be measured;

[0050] Step 2, using the series of radiation energies to respectively illuminate the workpiece to be measured, and obtaining radiation images under different radiation energies;

[0051] Step 3: Based on wavelet analysis, the ray images at different ray energies are fused to obtain a fused image;

[0052] Step 4: perform image enhancement processing on the fused image to obtain an enhanced fused image for use in judging the quality of the workpiece to be measured.

[0053] Compared with the prior art, in the embodiment of the present invention, for a large thickness ratio workpiece with large differences in equivalent thickness at different parts, a series of different radiation energies are used to perform transillumination imaging on the workpiece, and then the radiation images are fused based on wavelet analysis, so that the fused image contains information of radiation images of each energy. The complete structural information of the workpiece can be presented on one image without performing operations such as partitioned transillumination and thickness compensation. The operation is simple and efficient. After obtaining the fused image, the fused image is enhanced to enhance the details and contrast of the image, so that the structural information of the workpiece is displayed clearly and completely, which is conducive to improving the accuracy of workpiece quality judgment.

[0054] Among them, image fusion based on wavelet analysis can more effectively process the local features and overall structure in the image, thereby retaining more image details. Compared with the weighted summation image fusion method, it can more effectively extract and fuse the key information in the image. Image fusion based on wavelet analysis can better control the grayscale value of the fused image to keep it within a reasonable display range.

[0055] Step 1, setting a series of different ray energies according to the maximum thickness, minimum thickness and material of the workpiece to be measured, includes:

[0056] Testing the detector to obtain a corresponding relationship between a grayscale value detected by the detector and the energy of the ray emitted by the ray source when there is no object between the ray source and the detector;

[0057] Determine a series of expected grayscale values ​​corresponding to different thicknesses according to the maximum grayscale value detected by the detector, the maximum thickness and the minimum thickness of the workpiece to be measured;

[0058] Determining the expected ray energy corresponding to the expected grayscale values ​​corresponding to a series of different thicknesses according to the corresponding relationship;

[0059] Based on the radiation energy attenuation formula, a series of radiation energies of different sizes are calculated according to the workpiece material of the workpiece to be measured and the expected radiation energies corresponding to the series of different thicknesses.

[0060] In the present invention, energy is adaptively selected for radiographic imaging according to the workpiece structure, and radiographic energy design is performed through grayscale value testing and the radiographic energy attenuation formula, thereby achieving precise energy control and scientific calculation, reducing errors and radiation risks, and improving the accuracy, adaptability, and safety of detection.

[0061] Specifically, in the present invention, considering that different detectors respond differently to the same energy, the detectors are grayscale tested in advance to improve the adaptability of the detection method. Then, combined with the radiation energy attenuation formula, a quantitative relationship between the image grayscale value and the radiation energy can be established. Then, according to the maximum thickness, minimum thickness and workpiece material of the workpiece to be measured, a series of radiation energies of different sizes are set to match the radiation energy with the actual situation of the workpiece to be measured, ensuring that the structures at different thickness positions of the workpiece can be clearly displayed on the radiation image, reducing the detection error caused by improper selection of radiation energy, thereby improving the accuracy of detection. At the same time, through precise energy design, the use of radiation can be optimized and unnecessary radiation can be reduced.

[0062] Specifically, the ray energy attenuation formula is:

[0063] I=I0*e -μx ;

[0064] Where I0 is the energy intensity of the ray when it reaches the surface of the object, e is a natural constant, μ is the linear attenuation coefficient, which is determined by the material of the workpiece to be measured; x is the thickness of the object, and I is the energy intensity of the ray after passing through the object.

[0065] In the present invention, the ray energy attenuation calculation is performed according to the exponential attenuation law of the monoenergetic narrow beam X-ray. When the ray passes through an object, its attenuation conforms to the above-mentioned ray energy attenuation formula.

[0066] It should be noted that when the workpiece material is known, the linear attenuation coefficient μ is determined, and when the thickness and expected grayscale value are determined, the ray energy I when the ray reaches the detector surface can be determined based on the grayscale test results of the detector. From this, the energy intensity I0 of the ray when it reaches the object surface can be calculated based on the ray energy attenuation formula.

[0067] More specifically, determining a series of expected grayscale values ​​corresponding to different thicknesses based on the maximum grayscale value of the detector and the maximum and minimum thicknesses of the workpiece to be measured includes:

[0068] According to the maximum gray value of the detector, the gray value interval is set to [P1·I max ,P2·I max ]; among them, I max is the maximum grayscale value of the detector; P1 and P2 are percentages, and 0<P1<P2<100%;

[0069] Set the gray value corresponding to the minimum thickness of the workpiece to be measured to P1·I max The maximum thickness of the workpiece to be measured corresponds to the gray value P2·I max , the grayscale values ​​corresponding to other thicknesses between the minimum thickness and the maximum thickness of the workpiece to be measured are in the grayscale value interval [P1·I max ,P2·I max ]Interpolation values ​​are selected to determine a series of expected grayscale values ​​corresponding to different thicknesses.

[0070] Specifically, P1 and P2 satisfy the following value ranges:

[0071] 10%≤P1≤30%; 70%≤P2≤90%.

[0072] During implementation, according to experience, P1 = 20%, P2 = 80%, that is, the gray value interval is [20%·I max ,80%·I max ].

[0073] In an embodiment of the present invention, controlling the image grayscale value within the above-mentioned percentage range of the maximum grayscale value of the detector can optimize the dynamic range of the image, improve the image contrast, and adapt to the limitations of the display device. Such processing can make the image visually clearer while retaining more detail information.

[0074] Meanwhile, it is worth noting that in the embodiment of the present invention, the gray value corresponding to the minimum thickness of the workpiece to be measured is set to the minimum expected gray value in the gray value interval (P1·I max ), set the gray value corresponding to the maximum thickness of the workpiece to be measured to the maximum expected gray value in the gray value interval (P2·I max ), so that the thinnest part of the workpiece can be clearly imaged on the detector when the lowest ray energy is used for acquisition, and the thickest part of the workpiece can also be clearly imaged on the detector when the highest ray energy is used for acquisition. Furthermore, the grayscale values ​​corresponding to other thicknesses between the minimum thickness and the maximum thickness of the workpiece to be measured are in the grayscale value interval [P1·I max ,P2·I max ]Interpolation value selection ensures that other thickness parts of the workpiece can also be clearly imaged on the detector.

[0075] Step 2: Use the series of radiation energies to irradiate the workpiece to be measured, and obtain radiation images under different radiation energies.

[0076] Specifically, a radiographic imaging system primarily consists of a radiation source, a detector, and imaging control software. During imaging, a workpiece is placed on a stage, and the radiation source emits radiation that passes through the object, forming an image on the detector. The imaging control software controls the imaging process, setting parameters such as the radiation source voltage and current, detector gain, and scanning position. Adjusting these parameters, such as the source voltage and current, adjusts the radiation energy.

[0077] Step 3, fusing the radiographic images at different ray energies based on wavelet analysis to obtain a fused image, includes the following steps:

[0078] Performing wavelet transform on each of the radiation images at different radiation energies to obtain wavelet coefficients at different scales and positions;

[0079] For each wavelet coefficient at each scale and position, the coefficient with the largest absolute value is selected from the wavelet coefficients at the scale and position corresponding to each ray image as the fused coefficient;

[0080] The fused coefficients are transformed through inverse wavelet transform to reconstruct the image and obtain the fused image.

[0081] Among them, the X-ray images collected under different X-ray energies contain the structural information of different thickness parts of the workpiece. Through image fusion, the useful information in each image is extracted and fused into one image, so that the fused image can contain complete workpiece structural information.

[0082] In an embodiment of the present invention, the "absolute value maximum method" is adopted as the fusion rule, which means that among the wavelet coefficients at the same scale and position, the coefficient with the largest absolute value is selected as the coefficient of the fused image. This fusion rule helps to retain important details and edge information in the image, and can effectively enhance the visual effect and information content of the fused image.

[0083] Step 4, performing image enhancement processing on the fused image, includes:

[0084] Performing color scale mapping on the fused image so that the grayscale range of the fused image is adjusted to the displayable grayscale range of the display device;

[0085] The contrast enhancement process is performed on the fused image after the color scale mapping to obtain an enhanced fused image.

[0086] Compared to existing technologies, the present invention takes into account that image fusion will increase the grayscale value of the image to a certain extent, resulting in weak image contrast and an inability to fully and clearly present the workpiece's structural information. Therefore, during the image enhancement process, the fused image is first subjected to color gradation mapping to adjust the image's grayscale range, and then the image contrast is enhanced to obtain an image that fully and clearly presents the workpiece's structural information.

[0087] Specifically, gamma transformation is used to perform color scale mapping on the fused image. The formula of the gamma transformation is:

[0088] s=c(r+ε) γ ;

[0089] Where s is the pixel value on the output image; r is the pixel value on the original image; ε is the offset; γ is the gamma value, which is used to control the area and degree of image grayscale stretching; c is a constant.

[0090] Tone mapping refers to the process of mapping the pixel values ​​of an image from one range to another. Gamma transform is a tone mapping method that achieves this by nonlinearly adjusting the brightness of the image. During the gamma transform process, the pixel value of the output image is calculated using the above formula for each pixel value in the original image.

[0091] Specifically, a contrast-limited adaptive histogram equalization algorithm is used to perform contrast enhancement processing on the fused image after color level mapping.

[0092] After gamma transformation, the grayscale range of the image is adjusted to the range that can be displayed by the display device. The fused image contains the complete structural information of the workpiece. Due to the large difference in workpiece thickness, the grayscale value difference between the thinner part and the thicker part of the workpiece in the fused image will also be large. The large overall grayscale range of the image makes the details of the darker part of the image not clear enough and the image contrast is weak. Therefore, the distribution of the image grayscale histogram is adjusted by the contrast-limited adaptive histogram equalization algorithm to enhance the image contrast so that the workpiece structural information can be displayed completely and clearly.

[0093] Histogram equalization is an image enhancement method that improves image contrast. It works by stretching or evenly distributing the image's grayscale histogram, thereby achieving a more balanced brightness distribution. The contrast-constrained adaptive histogram equalization algorithm is an improved adaptive histogram equalization algorithm that limits the local contrast enhancement by limiting the height of the local histogram, thereby limiting noise amplification and over-enhancement of local contrast.

[0094] On the other hand, the present invention also provides a radiographic inspection system for workpieces with a large thickness ratio, the system comprising:

[0095] The radiation energy calculation module sets a series of different radiation energies according to the maximum thickness, minimum thickness and material of the workpiece to be measured;

[0096] A radiographic imaging device, comprising a radiation source and a detector, wherein the radiation source uses the series of radiation energies to transilluminate a workpiece to be measured, and the detector senses radiation that penetrates the workpiece to be measured and generates radiation images at different radiation energies; and

[0097] An image processing module includes an image fusion module and an image enhancement module, wherein the image fusion module fuses the radiation images under different radiation energies based on wavelet analysis to obtain a fused image, and the image enhancement module performs image enhancement processing on the fused image to obtain an enhanced fused image to judge the quality of the workpiece to be measured.

[0098] The ray detection system of the embodiment of the present invention is used to implement the ray detection method of the above embodiment. The two have the same features and can achieve the same technical effects, which will not be described in detail here.

[0099] Those skilled in the art will appreciate that all or part of the process steps of the above-described embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, such as a magnetic disk, an optical disk, a read-only memory, or a random access memory.

[0100] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for detecting a workpiece with a large thickness ratio, characterized in that: The method comprises: Set a series of different radiation energies according to the maximum thickness, minimum thickness and material of the workpiece to be measured; The series of radiation energies are respectively used to irradiate the workpiece to be measured, and the radiation images under different radiation energies are obtained; Based on wavelet analysis, the ray images under different ray energies are fused to obtain a fused image; The fused image is subjected to image enhancement processing to obtain an enhanced fused image for use in judging the quality of the workpiece to be measured.

2. The ray detection method according to claim 1, characterized in that: The method of fusing the ray images under different ray energies based on wavelet analysis to obtain a fused image includes the following steps: Performing wavelet transform on each of the ray images under different ray energies to obtain wavelet coefficients of different scales and positions; For each wavelet coefficient at each scale and position, the coefficient with the largest absolute value is selected from the wavelet coefficients at the scale and position corresponding to each ray image as the fused coefficient; The fused coefficients are transformed through inverse wavelet transform to reconstruct the image and obtain the fused image.

3. The ray detection method according to claim 1 or 2, characterized in that: The performing image enhancement processing on the fused image comprises: Performing color scale mapping on the fused image so that the grayscale range of the fused image is adjusted to the displayable grayscale range of the display device; The contrast enhancement process is performed on the fused image after the color scale mapping, so as to obtain an enhanced fused image.

4. The ray detection method according to claim 3, characterized in that: Gamma transformation is used to perform color scale mapping on the fused image. The formula of the gamma transformation is: s=c(r+ε) γ ; Where s is the pixel value on the output image; r is the pixel value on the original image; ε is the offset; γ is the gamma value, which is used to control the area and degree of grayscale stretching of the image; c is a constant.

5. The ray detection method according to claim 3, characterized in that: The contrast of the fused image after color level mapping is enhanced by using the limited contrast adaptive histogram equalization algorithm.

6. The ray detection method according to claim 1 or 2, characterized in that: The method of setting a series of different radiation energies according to the maximum thickness, minimum thickness and material of the workpiece to be measured includes: Testing the detector to obtain a corresponding relationship between a gray value detected by the detector and a ray energy emitted by the ray source when there is no object between the ray source and the detector; Determine a series of expected grayscale values ​​corresponding to different thicknesses according to the maximum grayscale value detected by the detector, the maximum thickness and the minimum thickness of the workpiece to be measured; Determine the expected ray energy corresponding to a series of expected grayscale values ​​corresponding to different thicknesses according to the corresponding relationship; Based on the radiation energy attenuation formula, a series of radiation energies of different magnitudes are calculated according to the workpiece material of the workpiece to be measured and the expected radiation energies corresponding to the series of different thicknesses.

7. The ray detection method according to claim 6, characterized in that: The ray energy attenuation formula is: I=I0*e -μx ; Where I0 is the energy intensity of the ray when it reaches the surface of the object, e is a natural constant, μ is the linear attenuation coefficient, which is determined by the material of the workpiece to be measured; x is the thickness of the object, and I is the energy intensity of the ray after passing through the object.

8. The ray detection method according to claim 6, characterized in that: The step of determining a series of expected grayscale values ​​corresponding to different thicknesses according to the maximum grayscale value of the detector, the maximum thickness and the minimum thickness of the workpiece to be measured comprises: According to the maximum gray value of the detector, the gray value interval is set to [P1·I max ,P2·I max ]; among them, I max is the maximum grayscale value of the detector; P1 and P2 are percentages, and 0<P1<P2<100%; Set the gray value corresponding to the minimum thickness of the workpiece to be measured to P1·I max The maximum thickness of the workpiece to be measured corresponds to the gray value P2·I max , the grayscale values ​​corresponding to other thicknesses between the minimum thickness and the maximum thickness of the workpiece to be measured are in the grayscale value interval [P1·I max ,P2·I max ]Interpolation values ​​are selected to determine a series of expected grayscale values ​​corresponding to different thicknesses.

9. The ray detection method according to claim 8, characterized in that: P1 and P2 satisfy the following value ranges: 10%≤P1≤30%; 70%≤P2≤90%.

10. A radiographic inspection system for workpieces with a large thickness ratio, characterized in that: The system comprises: The radiation energy calculation module sets a series of different radiation energies according to the maximum thickness, minimum thickness and material of the workpiece to be measured; A radiographic imaging device, comprising a radiation source and a detector, wherein the radiation source respectively uses the series of radiation energies to irradiate the workpiece to be measured, and the detector senses the radiation penetrating the workpiece to be measured and generates radiation images under different radiation energies; and An image processing module, wherein the image processing module includes an image fusion module and an image enhancement module, wherein the image fusion module performs image fusion on the radiation images under different radiation energies based on wavelet analysis to obtain a fused image, and the image enhancement module performs image enhancement processing on the fused image to obtain an enhanced fused image to judge the quality of the workpiece to be measured.

Images