阅读说明：本技术 基于太赫兹成像的缺陷检测方法及系统 (Terahertz imaging-based defect detection method and system ) 是由 刘荣海 程志强 孔旭晖 阎占元 李松涛 郭新良 杨迎春 郑欣 何运华 程雪婷 杨 于 2019-10-18 设计创作，主要内容包括：本申请公开了一种基于太赫兹成像的缺陷检测方法及系统,该方法包括：将被检测样品划分为若干扫查点,利用太赫兹波对若干所述扫查点进行步进扫查,得到若干所述扫查点分别对应的太赫兹时域透射脉冲；对若干所述太赫兹时域透射脉冲进行分析,得到若干扫查点对应的时域透射脉冲幅值；根据所述时域透射脉冲幅值,计算若干扫查点对应的灰度值,得到被检测样品的灰度图；根据灰度图中的明暗对比,定位被检测样品中的缺陷部位。本申请中基于太赫兹成像技术,对被检测样品进行成像,能够根据被检测样品提取出时域光谱数据,最终生成相应的灰度图,通过得到的灰度图能够使得待检测样品各种内部缺陷的形态可视化,从而准确的对待检测样品进行缺陷检测。(The application discloses a terahertz imaging-based defect detection method and system, and the method comprises the following steps: dividing a detected sample into a plurality of scanning points, and scanning the scanning points step by utilizing terahertz waves to obtain terahertz time-domain transmission pulses respectively corresponding to the scanning points; analyzing the plurality of terahertz time-domain transmission pulses to obtain time-domain transmission pulse amplitudes corresponding to the plurality of scanning points; calculating gray values corresponding to the plurality of scanning points according to the time domain transmission pulse amplitude values to obtain a gray map of the detected sample; and positioning the defect part in the detected sample according to the light and shade contrast in the gray-scale image. According to the method and the device, the detected sample is imaged based on the terahertz imaging technology, time domain spectral data can be extracted according to the detected sample, a corresponding gray-scale image is finally generated, the forms of various internal defects of the sample to be detected can be visualized through the obtained gray-scale image, and therefore defect detection can be accurately performed on the sample to be detected.)

1. A terahertz imaging-based defect detection method is characterized by comprising the following steps:

dividing a detected sample into a plurality of scanning points, and scanning the scanning points step by utilizing terahertz waves to obtain terahertz time-domain transmission pulses respectively corresponding to the scanning points;

analyzing the plurality of terahertz time-domain transmission pulses to obtain time-domain transmission pulse amplitudes corresponding to the plurality of scanning points;

calculating gray values corresponding to the scanning points according to the time domain transmission pulse amplitude to obtain a gray map of the detected sample;

and positioning the defect part in the detected sample according to the light and shade contrast in the gray-scale image.

2. The terahertz imaging based defect detection method according to claim 1, wherein the step scanning of the scanning points by the terahertz waves comprises:

and scanning the scanning point by stepping at 0.1 mm/time to 1 mm/time by using a terahertz imaging system with the signal-to-noise ratio of 1000dB and the spectral resolution of over 40 GHz.

3. The method for detecting the defect based on terahertz imaging according to claim 1, wherein the calculating the gray values corresponding to a plurality of scanning points according to the time-domain transmission pulse amplitude comprises:

comparing all the time domain transmission pulse amplitudes to obtain the maximum value and the minimum value of the time domain transmission pulse amplitudes;

recording the gray value corresponding to the maximum value as 255 and recording the gray value corresponding to the minimum value as 0;

the gray value corresponding to any one scanning point is as follows:

in the formula I_iTime domain transmission pulse amplitude, I, corresponding to any point scanned_minIs the minimum value of the amplitude of the time-domain transmission pulse, I_maxIs the maximum value of the time domain transmission pulse amplitude.

4. The method for detecting the defect based on terahertz imaging according to claim 1, wherein the locating the defect position in the detected sample according to the light and shade contrast in the gray scale image comprises:

comparing a gray value corresponding to any one scanning point with a preset threshold value, and screening defect points in all the scanning points, wherein the scanning points with the gray values smaller than the preset threshold value are defect points;

and obtaining the defect part of the detected sample according to the position of the defect point in the gray scale map.

5. A terahertz imaging based defect detection system, the system comprising:

the scanning module is used for dividing a detected sample into a plurality of scanning points, and performing stepping scanning on the plurality of scanning points by utilizing terahertz waves to obtain terahertz time-domain transmission pulses respectively corresponding to the plurality of scanning points;

the analysis module is used for analyzing the plurality of terahertz time-domain transmission pulses to obtain time-domain transmission pulse amplitudes corresponding to the scanning points;

the gray value calculation module is used for calculating gray values corresponding to the scanning points according to the time domain transmission pulse amplitude values to obtain a gray map of the detected sample;

and the defect positioning module is used for positioning the defect part in the detected sample according to the light and shade contrast in the gray-scale image.

6. The terahertz imaging based defect detection system of claim 5, wherein the gray value calculation module comprises:

the comparison unit is used for comparing all the time domain transmission pulse amplitudes to obtain the maximum value and the minimum value of the time domain transmission pulse amplitudes;

the assignment unit is used for recording the gray value corresponding to the maximum value as 255 and recording the gray value corresponding to the minimum value as 0;

the calculation unit is used for calculating the gray value corresponding to any one scanning point, and the calculation formula is as follows:

in the formula I_iTime domain transmission pulse amplitude, I, corresponding to any point scanned_minIs the minimum value of the amplitude of the time-domain transmission pulse, I_mazIs the maximum value of the time domain transmission pulse amplitude.

7. The terahertz imaging based defect detection system of claim 5, wherein the defect localization module comprises:

the screening unit is used for comparing a gray value corresponding to any scanning point with a preset threshold, wherein the scanning point with the gray value smaller than the preset threshold is a defect point, and screening all the defect points;

and the external unit is used for obtaining the defect part of the detected sample according to the position of the defect point in the gray scale image.

Technical Field

The application relates to the technical field of terahertz nondestructive testing, in particular to a terahertz imaging-based defect detection method and system.

Background

In the power system, the quality and reliability of live working tools and power insulators directly affect the safe and economic operation of the power system grid and the life safety of live working personnel. In the actual use process, the insulating operating rod can generate phenomena such as material degradation, insulation moisture or fiber breakage along with the increase of the service life. Therefore, defect detection is essential for the hot-line tool and the power insulator.

At present, the defect detection method for live working tools and power insulators is to perform power frequency and operating wave withstand voltage tests. The test procedure was as follows: connecting the tested sample to the equipment, switching on the power supply and starting the boosting test. In the boosting process, the high-voltage loop is monitored in real time, and whether the tested sample has abnormal sound or not is monitored. And when the voltage is increased to the test voltage, timing is started, and after a certain time is reached, voltage reduction is carried out and the power supply is cut off. If no destructive discharge occurs during the above test, it is considered that the test passed the withstand voltage test.

The above-described method is generally used for testing the hot-line tool and the power insulator before use, but the above-described testing method can only detect surface defects of the hot-line tool and the power insulator, but cannot effectively detect defects such as air holes, delamination, debonding, and fiber breakage in the hot-line tool and the power insulator, and cannot ensure reliability of the hot-line tool and the power insulator.

Disclosure of Invention

The application provides a defect detection method and system based on terahertz imaging, and aims to solve the technical problem that defects in live working tools and power insulators cannot be detected in the prior art.

In order to solve the technical problem, the embodiment of the application discloses the following technical scheme:

in a first aspect, an embodiment of the application discloses a defect detection method based on terahertz imaging, and the method includes:

dividing a detected sample into a plurality of scanning points, and scanning the scanning points step by utilizing terahertz waves to obtain terahertz time-domain transmission pulses respectively corresponding to the scanning points;

analyzing the plurality of terahertz time-domain transmission pulses to obtain time-domain transmission pulse amplitudes corresponding to the plurality of scanning points;

calculating gray values corresponding to the scanning points according to the time domain transmission pulse amplitude to obtain a gray map of the detected sample;

and positioning the defect part in the detected sample according to the light and shade contrast in the gray-scale image.

Optionally, in the method for detecting defects based on terahertz imaging, the step-by-step scanning of a plurality of scanning points by using terahertz waves includes:

and scanning the scanning point by stepping at 0.1 mm/time to 1 mm/time by using a terahertz imaging system with the signal-to-noise ratio of 1000dB and the spectral resolution of over 40 GHz.

Optionally, in the method for detecting defects based on terahertz imaging, the calculating a gray value corresponding to a plurality of scanning points according to the time-domain transmission pulse amplitude includes:

comparing all the time domain transmission pulse amplitudes to obtain the maximum value and the minimum value of the time domain transmission pulse amplitudes;

recording the gray value corresponding to the maximum value as 255 and recording the gray value corresponding to the minimum value as 0;

the gray value corresponding to any one scanning point is as follows:

in the formula I_iTime domain transmission pulse amplitude, I, corresponding to any point scanned_minIs the minimum value of the amplitude of the time-domain transmission pulse, I_maxIs the maximum value of the time domain transmission pulse amplitude.

Optionally, in the method for detecting defects based on terahertz imaging, the locating a defect site in the detected sample according to the contrast in the grayscale map includes:

comparing a gray value corresponding to any one scanning point with a preset threshold value, and screening defect points in all the scanning points, wherein the scanning points with the gray values smaller than the preset threshold value are defect points;

and obtaining the defect part of the detected sample according to the position of the defect point in the gray scale map.

In a second aspect, an embodiment of the present application discloses a defect detection system based on terahertz imaging, the system includes:

the scanning module is used for dividing a detected sample into a plurality of scanning points, and performing stepping scanning on the plurality of scanning points by utilizing terahertz waves to obtain terahertz time-domain transmission pulses respectively corresponding to the plurality of scanning points;

the analysis module is used for analyzing the plurality of terahertz time-domain transmission pulses to obtain time-domain transmission pulse amplitudes corresponding to the scanning points;

the gray value calculation module is used for calculating gray values corresponding to the scanning points according to the time domain transmission pulse amplitude values to obtain a gray map of the detected sample;

and the defect positioning module is used for positioning the defect part in the detected sample according to the light and shade contrast in the gray-scale image.

Optionally, in the defect detecting system based on terahertz imaging, the gray value calculating module includes:

the comparison unit is used for comparing all the time domain transmission pulse amplitudes to obtain the maximum value and the minimum value of the time domain transmission pulse amplitudes;

the assignment unit is used for recording the gray value corresponding to the maximum value as 255 and recording the gray value corresponding to the minimum value as 0;

the calculation unit is used for calculating the gray value corresponding to any one scanning point, and the calculation formula is as follows:

in the formula I_iTime domain transmission pulse amplitude, I, corresponding to any point scanned_minIs the minimum value of the amplitude of the time-domain transmission pulse, I_maxIs the maximum value of the time domain transmission pulse amplitude.

Optionally, in the defect detecting system based on terahertz imaging, the defect locating module includes:

the screening unit is used for comparing a gray value corresponding to any scanning point with a preset threshold, wherein the scanning point with the gray value smaller than the preset threshold is a defect point, and screening all the defect points;

and the external unit is used for obtaining the defect part of the detected sample according to the position of the defect point in the gray scale image.

Compared with the prior art, the beneficial effect of this application is:

the application provides a defect detection method and system based on terahertz imaging, wherein a sample to be detected is divided into a plurality of scanning points, and the plurality of scanning points are scanned step by utilizing terahertz waves to obtain terahertz time-domain transmission pulses respectively corresponding to the plurality of scanning points; analyzing the plurality of terahertz time-domain transmission pulses to respectively obtain time-domain transmission pulse amplitudes corresponding to the plurality of scanning points; then, calculating gray values corresponding to a plurality of scanning points one by one according to the time domain transmission pulse amplitude to obtain a gray map of the detected sample; and positioning the defect part in the detected sample according to the light and shade contrast in the gray-scale image. According to the method and the device, the detected sample is imaged based on the terahertz imaging technology, time domain spectral data can be extracted according to the detected sample, a corresponding gray-scale image is finally generated, the forms of various internal defects of the sample to be detected can be visualized through the obtained gray-scale image, and therefore defect detection can be accurately performed on the sample to be detected.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.

Drawings

In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic flow chart of a defect detection method based on terahertz imaging according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a basic structure of a defect detection system based on terahertz imaging according to an embodiment of the present invention.

Detailed Description

In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Referring to fig. 1, a schematic flow chart of a defect detection method based on terahertz imaging according to an embodiment of the present invention is provided. With reference to fig. 1, the defect detection method in the present application includes the following steps:

step S110: dividing a detected sample into a plurality of scanning points, and scanning the scanning points step by utilizing terahertz waves to obtain terahertz time-domain transmission pulses respectively corresponding to the scanning points;

the sample to be detected in the application can be a live working tool, a power insulator or a drop-out fuse and the like. Dividing the sample to be detected into a plurality of scanning points, and scanning the scanning points in sequence until the whole sample to be detected is scanned. Terahertz is an electromagnetic wave between microwave and infrared ray, has very strong penetrating power, and can obtain higher resolution by utilizing terahertz imaging. If defects exist in the sample to be detected or on the surface of the sample to be detected, such as impurities, dislocation, microcracks, fiber delamination, fiber and matrix interface cracking, fiber curling, glue rich or poor, holes, degumming, oxidation and the like, terahertz waves are scattered at the defect part, energy is greatly lost, and therefore obvious difference is generated between the terahertz waves and the imaging result of a continuous and uniform part of a material during imaging. By scanning and imaging the whole sample to be detected, the defect condition of the sample to be detected can be more clearly reflected on the imaging result after image processing.

According to the method, the terahertz imaging system with the signal-to-noise ratio of 1000dB and the spectral resolution of over 40GHz is used for transmitting the terahertz waves, the sample to be detected is placed at a focal plane between a terahertz wave transmitting head and a terahertz wave receiving head in the terahertz imaging system, and all scanning points are scanned in steps of 0.1 mm/time to 1 mm/time.

Step S120: analyzing the plurality of terahertz time-domain transmission pulses to obtain time-domain transmission pulse amplitudes corresponding to the plurality of scanning points;

step S130: calculating gray values corresponding to the scanning points according to the time domain transmission pulse amplitude to obtain a gray map of the detected sample;

firstly, all the time domain transmission pulse amplitude values I are_iComparing to obtain the maximum value I of the time domain transmission pulse amplitude_maxAnd a minimum value I_min. Wherein, I_max＝max(I₁,I₂,I₃……I_N)，I_min＝min(I₁,I₂,I₃……I_N) N isA natural number.

The maximum value I_maxThe corresponding gray value is recorded as 255, and the minimum value I is recorded_minAnd if the corresponding gray value is marked as 0, the gray value corresponding to any one scanning point is as follows:

in the formula I_iTime domain transmission pulse amplitude, I, corresponding to any point scanned_minIs the minimum value of the amplitude of the time-domain transmission pulse, I_maxIs the maximum value of the time domain transmission pulse amplitude.

Step S140: and positioning the defect part in the detected sample according to the light and shade contrast in the gray-scale image.

Comparing the gray value corresponding to any scanning point with a preset threshold value, and screening all the defect points in the scanning points, wherein the scanning points with the gray value smaller than the preset threshold value are the defect points. The size of the preset threshold value can be set by a worker according to the type of the sample to be detected. And finally, obtaining the defect part of the detected sample according to the position of the defect point in the gray scale image.

According to the method and the device, the detected sample is imaged based on the terahertz imaging technology, time domain spectral data can be extracted according to the detected sample, a corresponding gray-scale image is finally generated, the forms of various internal defects of the sample to be detected can be visualized through the obtained gray-scale image, and therefore defect detection can be accurately performed on the sample to be detected.

Based on the same technical concept, an embodiment of the present invention further provides a defect detection system based on terahertz imaging, and referring to fig. 2, a basic structural schematic diagram of the defect detection system based on terahertz imaging provided by the embodiment of the present invention is shown. As shown in fig. 2, the system includes:

the scanning module 21 is configured to divide a detected sample into a plurality of scanning points, and perform step-by-step scanning on the plurality of scanning points by using terahertz waves to obtain terahertz time-domain transmission pulses corresponding to the plurality of scanning points respectively;

the analysis module 22 is configured to analyze the plurality of terahertz time-domain transmission pulses to obtain time-domain transmission pulse amplitudes corresponding to the plurality of scanning points;

the gray value calculation module 23 is configured to calculate a gray value corresponding to the scanning points according to the time domain transmission pulse amplitude, so as to obtain a gray map of the detected sample;

and the defect positioning module 24 is used for positioning the defect part in the detected sample according to the light and shade contrast in the gray-scale image.

Further, the gray value calculating module 23 includes:

the comparison unit is used for comparing all the time domain transmission pulse amplitudes to obtain the maximum value and the minimum value of the time domain transmission pulse amplitudes;

the assignment unit is used for recording the gray value corresponding to the maximum value as 255 and recording the gray value corresponding to the minimum value as 0;

the calculation unit is used for calculating the gray value corresponding to any one scanning point, and the calculation formula is as follows:

in the formula I_iTime domain transmission pulse amplitude, I, corresponding to any point scanned_minIs the minimum value of the amplitude of the time-domain transmission pulse, I_maxIs the maximum value of the time domain transmission pulse amplitude.

Further, the defect localization module 24 includes:

the screening unit is used for comparing a gray value corresponding to any scanning point with a preset threshold, wherein the scanning point with the gray value smaller than the preset threshold is a defect point, and screening all the defect points;

and the external unit is used for obtaining the defect part of the detected sample according to the position of the defect point in the gray scale image.

Since the above embodiments are all described by referring to and combining with other embodiments, the same portions are provided between different embodiments, and the same and similar portions between the various embodiments in this specification may be referred to each other. And will not be described in detail herein.

It is noted that, in this specification, relational terms such as "first" and "second," and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a circuit structure, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such circuit structure, article, or apparatus. Without further limitation, the presence of an element identified by the phrase "comprising an … …" does not exclude the presence of other like elements in a circuit structure, article or device comprising the element.

Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.

The above-described embodiments of the present application do not limit the scope of the present application.