阅读说明：本技术 一种测量钢管数字射线图像信噪比的方法 (Method for measuring signal-to-noise ratio of digital radiographic image of steel pipe ) 是由 焦锋 刘明清 祝江 李梦玲 卢曼 陈晓林 欧宁 张建平 贾晓红 薛帏 白清春 于 2021-03-25 设计创作，主要内容包括：本发明提供了一种测量钢管数字射线图像信噪比的方法,本发明包括测量前准备、确定钢管规格、确定检测系统,对钢管设备进行检测调整,对所用软件进行调整,静态检测,获取图像,图像基本质量判别,测量信噪比,计算测量区域的平均灰度值与信号统计标准差,按照信噪比得到测量信噪比SNRm,再得到归一化信噪比SNRn。本发明检测效率高,后续处理手段丰富,图像的交互性、存储的便利性好。在生产使用中,能够校正平板探测器不一致性,满足灵敏度要求,还能根据需要测量分辨率、信噪比等关键因素,能验证使用的数字成像系统性能和采用的射线检测工艺参数是否满足标准要求,从而调整透照参数,提高信噪比,提高缺陷检出率,确保产品质量,适合推广使用。(The invention provides a method for measuring the signal-to-noise ratio of a steel pipe digital radiographic image, which comprises the steps of preparing before measurement, determining the specification of a steel pipe, determining a detection system, carrying out detection adjustment on steel pipe equipment, adjusting software used, carrying out static detection, obtaining an image, judging the basic quality of the image, measuring the signal-to-noise ratio, calculating the average gray value and the signal statistical standard deviation of a measurement area, obtaining the measurement signal-to-noise ratio SNRm according to the signal-to-noise ratio, and obtaining the normalized signal-to-noise ratio SNRn. The invention has high detection efficiency, rich subsequent processing means and good image interactivity and storage convenience. In production and use, the method can correct the inconsistency of the flat panel detector, meet the sensitivity requirement, measure key factors such as resolution, signal to noise ratio and the like according to needs, and verify whether the performance of the used digital imaging system and the adopted ray detection process parameters meet the standard requirement, so that transillumination parameters are adjusted, the signal to noise ratio is improved, the defect detection rate is improved, the product quality is ensured, and the method is suitable for popularization and use.)

1. A method for measuring the signal-to-noise ratio of a digital radiographic image of a steel pipe is characterized by comprising the following steps: the method comprises the following steps:

s1, preparing before measurement, determining the specification of the steel pipe and determining a detection system;

s2, detecting and adjusting the steel pipe measuring equipment;

s3, adjusting software used for measurement: setting the frame overlapping times and frame rate of a flat panel detector, and respectively carrying out offset correction, gain correction and file storage format on the flat panel;

s4, static detection, image acquisition: placing a single-line image quality meter, a double-line image quality meter and a part identification mark at a welding seam on the inner surface of a steel pipe, adjusting a welding seam detection part to a detector display area by using a detection tool, enabling an X ray to pass through a detected component to image on a flat panel detector in real time, and acquiring a digital image by using a software static image capturing function;

s5, judging the basic quality of the image: judging the sensitivity and the spatial resolution of the imaging system, and if the sensitivity and the spatial resolution both satisfy the values determined in advance through experiments, performing step S6; otherwise, the step S2 is switched to for equipment adjustment;

s6, measuring the signal-to-noise ratio of the image: when the detection sensitivity and the resolution meet the standard requirements, the software sets the area of a measurement part, places a selection frame at a parent metal position near a heat affected zone or a welding seam, calculates the average gray value and the signal statistical standard deviation of a measurement area, obtains a measurement signal-to-noise ratio SNRm according to the definition of the signal-to-noise ratio, and obtains a normalized signal-to-noise ratio SNRn through calculation;

s7, if the calculated normalized signal-to-noise ratio SNRn in S5 does not meet the standard requirement, adjusting the frame overlapping times in the step S3, re-measuring according to the step S5 after adjustment, and ending when the measured value meets the standard.

2. The method of claim 1, wherein the method comprises the following steps: in step S1, the detection system sets the highest voltage value to 225Kv, the ray energy range is less than 225kVp, and the display resolution is greater than 1024 × 768.

3. The method of claim 1, wherein the method comprises the following steps: the step S2 is a method for detecting and adjusting the steel pipe measuring equipment, including:

a1, calculating the focal position of the steel tube, and measuring the distance L1 between the focal position and the surface of the steel tube and the distance L2 between the surface of the steel tube and a flat panel detector; geometric unsharpness Ug;

a2, adjusting the distance between the ray tube, the steel tube and the flat panel detector according to the distances L1 and L2;

a3, calculating a transillumination range, a tube voltage, a tube current, a focus size and an exposure time, and adjusting the focus size, the tube voltage, the tube current, the focus size and the exposure time on an operation panel of the X-ray machine.

4. The method of claim 1, wherein the method comprises the following steps: the method for placing the single-line image quality meter, the double-line image quality meter and the part identification mark in the S4 comprises the following steps: according to the thickness, a single-line type image quality meter (W10 FE) and a metal wire are placed on a welding seam on the inner surface of the steel pipe to cross the welding seam, a double-line type image quality meter (15D) is placed on a parent metal close to the detected welding seam, a small included angle (about 5 degrees) is formed between the metal wire and a row or a column of a detector, lead positioning marks and identification marks are placed near the detected welding seam, images in an effective evaluation range cannot be interfered by all the marks, and the marks can be displayed clearly on the images at the same time.

5. The method of claim 1, wherein the method comprises the following steps: step S5, image basic quality determination: judging the sensitivity, the spatial resolution and the signal-to-noise ratio of the imaging system; if the sensitivity, the spatial resolution and the signal-to-noise ratio all satisfy values determined in advance by experiment, the step S6 is performed; otherwise, the method for switching to step S2 to perform device adjustment includes:

b1, verifying sensitivity: adjusting the gray scale range by using a histogram function, and observing the identifiable finest single-line type image quality measuring wire number and checking the detection sensitivity;

b2, measurement resolution: starting a resolution measuring tool, measuring the wire number of the identifiable double-line type image quality meter, and determining the detection resolution;

b3, if the sensitivity and the measurement resolution do not meet the standard requirements, readjusting the steel pipe equipment in the step S2, and acquiring the image again until the sensitivity and the resolution meet the standard requirements.

6. The method of claim 5, wherein the method comprises the following steps: the checked component is characterized in that a single-wire image quality meter and a double-wire image quality meter image are pasted on the surface for receiving the X-ray; the resolution ratio of the flat panel detector is not lower than 3.5lp/mm, the gray scale is not lower than 16bit, and the flat panel detector has a long-term integration function; and wireless cloud data transmission is carried out between the industrial computer and the flat panel detector, so that remote image receiving is realized.

7. The method of claim 1, wherein the method comprises the following steps: in step S4, a fixed X-ray machine is used, and the voltage, current, exposure time, and X-ray machine delay on time are set by the central controller.

Technical Field

The invention relates to the field of measuring the quality of a steel pipe digital radiographic image, in particular to a method for measuring the signal-to-noise ratio of the steel pipe digital radiographic image.

Background

Pipeline transportation is used as an efficient special transportation means, and plays an increasingly important role in the field of petroleum and natural gas transportation. At present, domestic transportation pipelines are mainly constructed by spiral steel pipes and straight seam steel pipes. To ensure reliable operation of the transport pipeline, the quality of the steel pipes used must be strictly guaranteed. With the continuous development of X-ray detection technology in steel pipe production, the traditional film photographic technology and real-time imaging technology are gradually replaced by digital ray detection technology and are used for detecting the full weld joint of the steel pipe. The detection quality mainly depends on the quality of the digital image, and the method has the advantages of good real-time performance, high detection efficiency, rich subsequent processing means, and good image interactivity and storage convenience. However, in production and use, the inconsistency of the flat panel detector needs to be corrected, so that not only the sensitivity requirement is met, but also key factors such as measurement resolution, signal-to-noise ratio and the like are needed, and the image signal-to-noise ratio is a main index reflecting the performance and the image quality of an imaging system.

Chinese patent No. CN 109781752A relates to an X-ray digital imaging enhancement and quantitative identification method for detecting sleeve grouting defects. The working principle is as follows: the method comprises the following steps: s1, acquiring an image; s2, judging the basic quality of the image: judging the sensitivity, the spatial resolution and the signal-to-noise ratio of the imaging system; if the sensitivity, the spatial resolution and the signal-to-noise ratio all satisfy the values determined in advance by the experiment, the step S3 is performed; otherwise, the step S1 is switched to acquire the image again; s3, enhancing image quality; s4, identifying grouting defect interfaces; s5, grouting defect length measurement: if the grouting defect is positioned at the end part of the sleeve grout outlet, measuring the distance from the bottom of the sleeve grout outlet to the grouting defect interface; if the grout defect is located in the middle of the sleeve, the distance between the two grout defect interfaces is measured. The method solves the problems that the method can clearly image the whole length range of the sleeve, and can determine the defect interface and further determine the size of the defect based on the gray level calculation of the image. However, when the device is used, whether the process parameters meet the standard requirements or not cannot be detected, the performance of the used digital imaging system cannot be verified, the detection position is single, and the detection range is limited.

Disclosure of Invention

The invention provides a method for measuring the signal-to-noise ratio of a digital radiographic image of a steel pipe, which solves the technical problems of how to verify whether the performance of a used digital imaging system and adopted radiographic detection process parameters meet standard requirements, how to adjust transillumination parameters in detection, improve the signal-to-noise ratio, improve the defect detection rate, ensure the product quality and the like.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the method comprises the following steps of S1, preparation before measurement, steel pipe specification determination and detection system determination;

s2, detecting and adjusting the steel pipe measuring equipment;

s3, adjusting software used for measurement: setting the frame overlapping times and frame rate of a flat panel detector, and respectively carrying out offset correction, gain correction and file storage format on the flat panel;

s4, static detection, image acquisition: placing a single-line image quality meter, a double-line image quality meter and a part identification mark at a welding seam on the inner surface of a steel pipe, adjusting a welding seam detection part to a detector display area by using a detection tool, enabling an X ray to pass through a detected component to image on a flat panel detector in real time, and acquiring a digital image by using a software static image capturing function;

s5, judging the basic quality of the image: judging the sensitivity and the spatial resolution of the imaging system, and if the sensitivity and the spatial resolution both satisfy the values determined in advance through experiments, performing step S6; otherwise, the step S2 is switched to for equipment adjustment;

s6, measuring the signal-to-noise ratio of the image: when the detection sensitivity and the resolution meet the standard requirements, the software sets the area of a measurement part, places a selection frame at a parent metal position near a heat affected zone or a welding seam, calculates the average gray value and the signal statistical standard deviation of a measurement area, obtains a measurement signal-to-noise ratio SNRm according to the definition of the signal-to-noise ratio, and obtains a normalized signal-to-noise ratio SNRn through calculation;

s7, if the calculated normalized signal-to-noise ratio SNRn in S5 does not meet the standard requirement, adjusting the frame overlapping times in the step S3, re-measuring according to the step S5 after adjustment, and ending when the measured value meets the standard.

In a preferred embodiment, in step S1, the detection system sets the maximum voltage value to 225Kv, the radiation energy range is less than 225kVp, and the display resolution is greater than 1024 × 768.

In a preferred embodiment, the step S2 of detecting and adjusting the steel pipe measuring device includes:

a1, calculating the focal position of the steel tube, and measuring the distance L1 between the focal position and the surface of the steel tube and the distance L2 between the surface of the steel tube and a flat panel detector; geometric unsharpness Ug;

a2, adjusting the distance between the ray tube, the steel tube and the flat panel detector according to the distances L1 and L2;

a3, calculating a transillumination range, a tube voltage, a tube current, a focus size and an exposure time, and adjusting the focus size, the tube voltage, the tube current, the focus size and the exposure time on an operation panel of the X-ray machine.

Preferably, the method for placing the single-line image quality meter, the double-line image quality meter, and the part identification mark in S4 includes: according to the thickness, a single-line type image quality meter (W10 FE) and a metal wire are placed on a welding seam on the inner surface of the steel pipe to cross the welding seam, a double-line type image quality meter (15D) is placed on a parent metal close to the detected welding seam, a small included angle (about 5 degrees) is formed between the metal wire and a row or a column of a detector, lead positioning marks and identification marks are placed near the detected welding seam, images in an effective evaluation range cannot be interfered by all the marks, and the marks can be displayed clearly on the images at the same time.

Preferably, the step S5 is to judge the basic image quality: judging the sensitivity, the spatial resolution and the signal-to-noise ratio of the imaging system; if the sensitivity, the spatial resolution and the signal-to-noise ratio all satisfy values determined in advance by experiment, the step S6 is performed; otherwise, the method for switching to step S2 to perform device adjustment includes:

b1, verifying sensitivity: adjusting the gray scale range by using a histogram function, and observing the identifiable finest single-line type image quality measuring wire number and checking the detection sensitivity;

b2, measurement resolution: starting a resolution measuring tool, measuring the wire number of the identifiable double-line type image quality meter, and determining the detection resolution;

b3, if the sensitivity and the measurement resolution do not meet the standard requirements, readjusting the steel pipe equipment in the step S2, and acquiring the image again until the sensitivity and the resolution meet the standard requirements.

In a preferred scheme, a single-wire image quality meter and a double-wire image quality meter image are pasted on the surface of the detected component for receiving X-rays; the resolution ratio of the flat panel detector is not lower than 3.5lp/mm, the gray scale is not lower than 16bit, and the flat panel detector has a long-term integration function; and wireless cloud data transmission is carried out between the industrial computer and the flat panel detector, so that remote image receiving is realized.

Preferably, in step S4, a fixed X-ray machine is used, and the voltage, current, exposure time, and X-ray machine delay on time are set by the central controller.

The invention provides a method for measuring the signal-to-noise ratio of a digital radiographic image of a steel pipe, which solves the technical problems of how to verify whether the performance of a used digital imaging system and adopted radiographic detection process parameters meet standard requirements, how to adjust transillumination parameters in detection, improve the signal-to-noise ratio, improve the defect detection rate, ensure the product quality and the like. Compared with the prior art, the method comprises the steps of preparing before measurement, determining the specification of the steel pipe and determining a detection system; detecting and adjusting steel pipe measuring equipment; the software used for the measurements was adjusted: static detection, obtaining an image, and judging the basic quality of the image; and measuring the signal-to-noise ratio of the image, calculating the average gray value and the signal statistical standard deviation of the measurement region by software, obtaining a measurement signal-to-noise ratio SNRm according to the definition of the signal-to-noise ratio, and then obtaining a normalized signal-to-noise ratio SNRn. The structure function is various and the real-time performance is good, the detection efficiency is high, the subsequent processing means is rich, and the interaction and the storage convenience of the image are good. In production and use, the inconsistency of the flat panel detector needs to be corrected, the sensitivity requirement is met, key factors such as resolution, signal to noise ratio and the like can be measured according to needs, the performance and the image quality of an imaging system are reflected through the signal to noise ratio of the image, and the method is accurate, practical and suitable for popularization and use.

Drawings

The invention is further illustrated by the following examples in conjunction with the accompanying drawings:

FIG. 1 is an overall flow chart of the present invention.

Detailed Description

Example 1:

as shown in FIG. 1, a method for measuring the signal-to-noise ratio of a digital radiographic image of a steel pipe, taking the steel pipe specification phi 1016 x 21mm as an example to test the signal-to-noise ratio, comprises the following steps:

first step, preparation before measurement, steel pipe specification determination and detection system determination

(1) Computer for measurement preparation: operating system Windows 7 or above; CPU, 3.0GHz four-core and higher processor, memory 4GB and above; the hard disk has more than 100GB available space; the display card is an independent display card or an integrated display card which is driven by WDDM2.0 and supports DirectX 9 and has the level higher than 256MB video memory; kilomega wired network card; VIVA software matched with the flat panel detector, wherein the software functions comprise detector calibration, detector setting, image acquisition, image processing, format conversion and the like;

(2) determining a detection system; the X-ray machine model HS-XY-225, the X-ray tube model MXR-225/21, the highest tube voltage 225Kv, the focal size 1.0/3.0, the flat panel detector model VarexPS1313DX, the detector area 130X 130mm, the pixel size 127 μm, the ray energy range less than 225kVp, the A/D conversion digit 16bit, the frame rate 30fps (1X 1), 60fps (2X 2); the resolution of the display is more than or equal to 1024 multiplied by 768;

(3) determining the specification of the steel pipe: calculating the distance between a focus of phi 1016 multiplied by 21mm and the surface L1 of the steel pipe, wherein a radiation source transilluminates the steel pipe internally, and is usually placed at the center of the steel pipe, and the distance between the source and the surface of the steel pipe is L1 ═ 1016/2) -21 ═ 487mm, so that the minimum focal distance required by the standard is met; in order to ensure that the flat panel detector does not collide when detecting the steel tube, but the flat panel detector is close to the steel tube as much as possible, the distance between the outer surface of the steel tube and the flat panel detector is 20mm, the distance between the inner surface of the steel tube and the detector L2 is 20+21 is 41mm, and the magnification factor M is (487+41) ÷ 487 is approximately equal to 1.08; the ray source generally adopts a large focus, the focus size d is 3.0mm, the geometric ambiguity Ug is 3 multiplied by 41 ÷ 487 ≈ 0.25mm, the one-time transillumination range is the detector size 130mm, the transillumination parameters of the ray machine are checked, the tube voltage of the ray machine is set to 190Kv, the current of the ray tube is 5mA, and the transillumination time is the detection time required by the full steel tube and is 10 min.

Secondly, detecting and adjusting the steel pipe measuring equipment

And (3) adjusting the distance between the ray tube, the steel tube and the flat panel detector according to the L1 and the L2 calculated in the step (3), and adjusting the focal size of the ray source, the tube voltage, the tube current and the transillumination time on an operation panel of the X-ray machine.

Thirdly, adjusting software used for measurement: and setting the frame superposition times and the frame rate of the flat panel detector, and respectively carrying out offset correction, gain correction and file storage format on the flat panel.

And setting the frame superposition times of the flat panel detector to be 16 times and the frame rate to be 15 frames/second by using VIVA software, respectively carrying out offset correction and gain correction on the flat panel according to software correction instructions, eliminating bad pixels and system noise of the detector, and setting a file storage format to be a star-img.

Step four, static detection, image acquisition: the method comprises the steps of placing a single-line image quality meter, a double-line image quality meter and a part identification mark at a welding seam on the inner surface of a steel pipe, adjusting a welding seam detection part to a detector display area by using a detection tool, enabling an X ray to pass through a detected component to image on a flat panel detector in real time, and acquiring a digital image by using a software static image capturing function.

Placing a single-line type image quality meter (W10 FE) at the welding seam on the inner surface of the steel pipe according to the transillumination thickness, placing a double-line type image quality meter (15D) on a parent metal close to the detected welding seam, wherein the wire and the row or column of a detector form a small included angle (about 5 degrees), placing lead positioning marks and identification marks near the detected welding seam, and all marks are not required to interfere with images in an effective evaluation range and can be displayed clearly on images; starting an X-ray machine, adjusting a welding line detection part to a detector display area by using a detection tool, acquiring a digital image by using a software static image capturing function, and adjusting a gray scale range by using a histogram function.

And fifthly, judging the basic quality of the image: judging the sensitivity and the spatial resolution of the imaging system, and if the sensitivity and the spatial resolution both meet the numerical values determined in advance through experiments, performing step S6; otherwise, the process goes to step S2 to perform device adjustment.

Observing the identifiable finest single-line type image quality meter wire number, checking the detection sensitivity, starting a resolution measuring tool, measuring the identifiable double-line type image quality meter wire number, and determining the detection resolution; and if the calibration sensitivity and the measurement resolution do not meet the standard requirements, readjusting the step 2.

Sixthly, measuring the signal-to-noise ratio of the image: when the detection sensitivity and the resolution meet the standard requirements, the software sets the area of a measurement part, places a selection frame at a parent metal position near a heat affected zone or a welding seam, calculates the average gray value and the signal statistical standard deviation of the measurement area, obtains a measurement signal-to-noise ratio SNRm according to the definition of the signal-to-noise ratio, and obtains a normalized signal-to-noise ratio SNRn through calculation.

When the detection sensitivity and the resolution meet the standard requirements, software sets a rectangular frame with the area of the measurement part of 20 multiplied by 55 pixels, places the rectangular frame at the uniform part of the parent metal near the heat affected zone or the welding seam, and calculates the average gray value of the measurement areaAnd the signal statistical standard deviation sigma to obtain the measured signal-to-noise ratio according to the definition of the signal-to-noise ratioAnd then calculating to obtain the normalized signal-to-noise ratio SNRn which is SNRm multiplied by 88.6/pixel size SRb.

And seventhly, if the normalized signal-to-noise ratio SNRn calculated in the step S5 does not meet the standard requirement, adjusting the frame superposition times in the step S3, re-measuring according to the step S5 after adjustment, and finishing after the measured value meets the standard.

The above-described embodiments are merely preferred embodiments of the present invention, and should not be construed as limiting the present invention, and features in the embodiments and examples in the present application may be arbitrarily combined with each other without conflict. The protection scope of the present invention is defined by the claims, and includes equivalents of technical features of the claims. I.e., equivalent alterations and modifications within the scope hereof, are also intended to be within the scope of the invention.