CN102183524B - Double-CCD (Charge Coupled Device) detecting method and system for apparent defect assessment of civil engineering structure - Google Patents

Abstract

A dual-CCD detection method and its equipment for evaluating the apparent defects of civil engineering structures, the method includes the following methods: the structural configuration method of the dual-CCD detection system for apparent defects, the calculation method of the feature point space coordinates of the dual-CCD detection method, the structural appearance The matching method of defect image feature points and the evaluation method of structural apparent defect size. The detection system is composed of dual CCD cameras, bracket, dual-channel image acquisition card, computer and apparent defect detection and evaluation software. The image acquisition card is installed on the computer, and the assessment software control system realizes the acquisition, processing and assessment of structural apparent defect images. The invention has the functions of dual CCD synchronous acquisition, image display and storage, feature matching, defect damage assessment and providing detection report, has the advantages of real-time acquisition and fast processing, and is suitable for on-site measurement of engineering structures.

Description

Double CCD detection method and system for evaluating apparent defects of civil engineering structures

technical field

The invention relates to the technical field of defect detection of civil engineering structures, in particular to a double-CCD detection method and system for evaluating apparent defects of civil engineering structures.

Background technique

Due to changes in the external environment and the influence of human errors, civil engineering structures will suffer various degrees of damage during service, while most of the defects of concrete structures originate or appear on the surface of the structure, such as cracks, holes, corrosion pits, Grooves, etc., reduce the safety, integrity and serviceability of the overall structure, affecting the normal use of the structure. The existence of these defects seriously threatens the safety and reliability of the structure, may lead to structural instability or strength damage, and seriously even affect the normal operation and benefit of the project. In order to ensure safe production, it is necessary to regularly inspect and evaluate the structure.

The traditional inspection methods for the apparent defects of civil engineering structures mainly rely on visual inspection, and inspectors conduct naked eye observation or touch. In this way, visual inspection can only roughly estimate the size range of cracks, but cannot obtain accurate results; moreover, due to the limitation of its own conditions, the visual inspection method has the disadvantages of limited detection ability, low detection reliability, long detection time, and high cost. In order to improve detection efficiency and accuracy, reduce labor intensity, and save detection costs, people have been exploring more effective detection methods and methods.

As an important non-destructive testing method, CCD imaging technology has the advantages of fast speed, non-contact, high precision, and simple operation. It has played a huge role in many fields. Provide a new technical support. The dual-CCD detection method can not only evaluate the in-plane size of the apparent defects of civil engineering structures, but also realize the measurement of the depth from the surface of the defect size, which can better meet the actual needs of engineering inspections.

Contents of the invention

The purpose of the present invention is to provide a dual-CCD detection method and system suitable for evaluating apparent defects of civil engineering structures.

A dual-CCD detection method for the evaluation of apparent defects in civil engineering structures is as follows:

(1) Structural configuration method of dual CCD detection system for apparent defects:

In order to obtain the spatial coordinates of structural apparent defect feature points from two-dimensional images, dual CCD cameras need to acquire two images containing structural apparent defect feature points from different positions; two CCD cameras are placed crosswise from different angles to observe the same For the object under test, the structural configuration of the dual-CCD detection system must first determine the angle of view of a single CCD camera, and then design the baseline distance B and angle α between the two CCD cameras according to the actual situation of engineering applications to obtain the best common Field of view, in order to obtain the viewing angle of the CCD camera in the actual inspection, it is necessary to make the CCD camera perpendicular to a plane, adjust the distance between the CCD camera and the surface of the structure to make the image clear, and let the optical axis of the CCD camera point to the center of the cross on the plane, and Let the optical axis of the CCD camera point to the center of the cross on the plane, place two rulers in the direction perpendicular to each other in the center of the cross, and then take a picture. According to the distance of the rulers that can be captured in the image, the CCD camera can be calculated. Viewing angles in the horizontal and vertical directions, and finally, the public field of view of the dual-CCD detection system can be calculated according to the baseline distance between the two CCD cameras, the angle between the camera and the baseline, and the viewing angle of the cameras;

(2) Calculation method of feature point space coordinates of double CCD detection method:

Double CCD cameras watch a certain feature point P on the surface of the structure at the same time, and use the left and right CCD cameras to obtain images of point P respectively. Their image coordinates are P _l = (X _l , Y _l ), P _r = (X _r , Y _r ), when the image planes of the two CCD cameras are on the same plane, the Y coordinates of the image coordinates of the feature point P are the same, that is, Y _left = Y _right = Y, obtained by the perspective transformation principle:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; left</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}\frac{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}$ ${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; right</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}$ $\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}\frac{{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}$

Then the time difference is: Disparity=|X _left -X _right |=X _left -X _right .

From this, the spatial coordinates of the feature points on the surface of the structure in the coordinate system of the dual-CCD detection system can be calculated as:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}}{\mathrm{<span\; class="notranslate">\; Disparity</span>}}\\ {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; Y</span>}}{\mathrm{<span\; class="notranslate">\; Disparity</span>}}\\ {\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; Disparity</span>}}\end{array}\right.$

Therefore, as long as any point on the left CCD camera surface can find the corresponding matching point on the right CCD camera image surface, that is, the two are the same point in space on the left and right CCD cameras, it can be determined according to the inherent geometric constraints of the dual CCD camera This method is a point-to-point operation. As long as there are matching points for all points on the image, they can participate in the above operation, so as to obtain the spatial coordinates of the structural apparent defect feature points. Therefore, the measurement efficiency higher.

(3) Matching method of structural apparent defect image feature points:

The matching of the feature points of the apparent defect image is to find the corresponding relationship between the feature points in the two images through the method of image matching, so as to determine the coordinates of the same feature point in the two images, and the characteristics of the defect image Matching requires feature extraction of two apparent defect images, and Harris corner point extraction algorithm, SUSAN corner point extraction algorithm or SIFT feature point extraction algorithm can be used;

When obtaining the coordinates of the image, two methods, interactive recognition and automatic feature matching, can be used. The advantage of interactive recognition is that it can accurately find the same feature point in two views. The disadvantage is that it cannot accurately determine the coordinates of the point. Automatic feature matching Matching is to use the feature point extraction and matching algorithm to accurately locate the feature points, but the matching result of the feature points may not be able to match the key position of the defect, so the feature point matching can be carried out through the automatic matching method first. can meet the requirements, and then use the method of interactive recognition for matching,

In the dual-CCD detection method, the matching of corresponding feature points is mainly the similarity of geometric primitives such as points, edges or regions in the two images, and then the image coordinates of the corresponding points formed by projecting the same feature point into the two images respectively , the spatial coordinates of the feature points can be calculated according to the mathematical model of the dual-CCD detection method;

(4) Evaluation method of structural apparent defect size:

After obtaining the spatial coordinates of the characteristic points of structural apparent defects, the length of the defect can be obtained according to the distance between two points in the space, and the coordinates of the two points in the space are respectively P ₁ (X ₁ , Y ₁ , Z ₁ ) , P ₂ (X ₂ , Y ₂ , Z ₂ ), then the length calculation formula is:

$\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; =</span>\sqrt{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

Depth measurement of defects first needs to establish a measurement reference plane, and the obtained depth is relative to this reference plane. Space plane, let the coordinates of three points in the space be P ₁ (X ₁ , Y ₁ , Z ₁ ), P ₂ (X ₂ , Y ₂ , Z ₂ ), P ₃ (X ₃ , Y ₃ , Z ₃ ), then the space plane equation is:

[(Y ₁ Z ₂ +Y ₂ Z ₃ +Y ₃ Z ₁ )-(Y ₃ Z ₂ +Y ₂ Z ₁ +Y ₁ Z ₃ )]X

+[(X ₁ Z ₂ +X ₂ Z ₃ +X ₃ Z ₁ )-(X ₂ Z ₂ +X ₂ Z.+X ₁ Z ₃ )]Y

+[(X ₁ Y ₂ +X ₂ Y ₃ +X ₃ Y ₁ )-(X ₃ Y ₁ +X ₂ Y ₁ +X ₃ Y3)]Z

+[(X ₁ Y ₂ Z ₃ +X ₂ Y ₃ Z ₁ +X ₃ Y ₁ Z ₃ )-(X ₃ Y ₂ Z ₁ +X ₂ Y ₁ Z ₃ +X ₁ Y ₃ Z ₂ )]＝0

(Y ₁ Z ₂ +Y ₂ Z ₃ +Y ₃ Z ₁ )-(Y ₃ Z ₂ +Y ₂ Z ₁ +Y ₁ Z ₃ )＝A

(X ₁ Z ₂ +X ₂ Z ₃ +X ₃ Z ₁ )-(X ₂ Z ₂ +X ₂ Z.+X ₁ Z ₃ )＝B

make

(X ₁ Y ₂ +X ₂ Y ₃ +X ₃ Y ₁ )-(X ₃ Y ₁ +X ₂ Y ₁ +X ₃ Y ₃ )＝C

(X ₁ Y ₂ Z ₃ +X ₂ Y ₃ Z ₁ +X ₃ Y ₁ Z ₃ )-(X ₃ Y ₂ Z ₁ +X ₂ Y ₁ Z ₃ +X ₁ Y ₃ Z ₂ )＝D

Then the plane equation is AX+BY+CZ+D=0,

Let the coordinates of the space point be K(X _k , Y _k , Z _k ), then the distance from the space point to the space plane is:

$\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Bb</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Cc</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; |</span>}{\sqrt{{\mathrm{<span\; class="notranslate">\; A</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}$

From this, the length, width and depth information of structural apparent defects are calculated,

Therefore, as long as the coordinates of the spatial points in the image are obtained, the three-dimensional coordinates of the spatial points can be calculated, and then the relative positional relationship of the spatial points can be obtained, and the damage assessment of the apparent defects of civil engineering structures is completed.

The present invention also has the following features:

A dual-CCD detection system for evaluating apparent defects of civil engineering structures. The system consists of dual-CCD cameras, brackets, dual-channel image acquisition cards, computers and apparent defect detection and evaluation software. It is characterized in that: the dual-CCD cameras are installed on On the bracket, the dual CCD cameras are connected to the dual-channel image acquisition card through wires, and the dual-channel image acquisition card is installed on the computer, and the detection system is controlled by the apparent defect detection and evaluation software to realize the acquisition, processing and evaluation of the structural apparent defect image; The performance of the double CCD camera model is the same, with higher image resolution, automatic gain control and automatic background light compensation function, and the size of the optical lens must match the size of the CCD sensor, the interface type must match, and it is a megapixel lens; Two CCD cameras can be installed on the bracket, and its two sides are symmetrical and can move closer to the center at the same time, which can realize the horizontal and pitch rotation of each camera; the two-way image acquisition card can be an analog acquisition card or a digital acquisition card, and the interface type It can be IEEE1394, gigabit network card or USB2.0; the apparent defect detection and evaluation software is controlled by a computer to realize the functions of dual-channel image synchronous acquisition, display processing, feature matching, damage evaluation and interactive identification, according to the apparent defect evaluation algorithm Measure the three-dimensional size of the apparent defect of the structure, and provide the inspection report of the apparent defect of the structure.

The invention has the functions of dual CCD synchronous acquisition, image display and storage, feature matching, defect damage assessment, and detection report provision, and has the advantages of real-time acquisition, fast processing, simple operation, etc., and is suitable for on-site measurement of engineering structures.

Description of drawings

Figure 1 is a schematic configuration diagram of the dual CCD camera detection system.

Fig. 2 is a schematic diagram of the space coordinate calculation of the present invention.

Fig. 3 is a detection principle diagram of the present invention.

Detailed ways

Example:

A dual-CCD detection method for the evaluation of apparent defects in civil engineering structures is as follows:

(1) Structural configuration method of dual CCD detection system for apparent defects:

In order to obtain the spatial coordinates of structural apparent defect feature points from two-dimensional images, dual CCD cameras need to acquire two images containing structural apparent defect feature points from different positions; two CCD cameras are placed crosswise from different angles to observe the same The object to be measured, Figure 1 is the structural configuration mode of the dual CCD camera detection system.

The structural configuration of the dual-CCD detection system must first determine the viewing angle of a single CCD camera, and then design the baseline distance B and the angle α between the two CCD cameras according to the actual situation of engineering applications to obtain the best common field of view. To obtain the angle of view of the CCD camera in the actual inspection, it is necessary to make the CCD camera perpendicular to a plane, adjust the distance between the CCD camera and the surface of the structure to make the image clear, and let the optical axis of the CCD camera point to the center of the cross on the plane, and let the CCD camera’s The optical axis points to the center of the cross on the plane. Place two scales in the direction perpendicular to the cross center, and then take a picture. According to the distance between the scales that can be photographed in the image, the CCD camera can be calculated in the horizontal direction and The angle of view in the vertical direction, and finally, the public field of view of the dual-CCD detection system can be calculated according to the baseline distance between the two CCD cameras, the angle between the camera and the baseline, and the angle of view of the cameras;

(2) Calculation method of feature point space coordinates of double CCD detection method:

As shown in Figure 2, dual CCD cameras watch a certain feature point P on the surface of the structure at the same time, and use the left and right CCD cameras to obtain images of point P respectively. Their image coordinates are P _l = (X _l , Y _l ), P _r =(X _r , Y _r ), when the image planes of the two CCD cameras are on the same plane, the Y coordinates of the image coordinates of the feature point P are the same, that is, Y _left =Y _right =Y, obtained by the perspective transformation principle:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; left</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}\frac{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}$ ${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; right</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}$ $\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}\frac{{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}$

Then the time difference is: Disparity=|X _left -X _right |=X _left -X _right .

From this, the spatial coordinates of the feature points on the surface of the structure in the coordinate system of the dual-CCD detection system can be calculated as:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}}{\mathrm{<span\; class="notranslate">\; Disparity</span>}}\\ {\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; Y</span>}}{\mathrm{<span\; class="notranslate">\; Disparity</span>}}\\ {\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; Disparity</span>}}\end{array}\right.$

Therefore, as long as any point on the left CCD camera surface can find the corresponding matching point on the right CCD camera image surface, that is, the two are the same point in space on the left and right CCD cameras, it can be determined according to the inherent geometric constraints of the dual CCD camera This method is a point-to-point operation. As long as there are matching points for all points on the image, they can participate in the above operation, so as to obtain the spatial coordinates of the structural apparent defect feature points. Therefore, the measurement efficiency higher.

(3) Matching method of structural apparent defect image feature points:

The matching of the feature points of the apparent defect image is to find the corresponding relationship between the feature points in the two images through the method of image matching, so as to determine the coordinates of the same feature point in the two images, and the characteristics of the defect image Matching requires feature extraction of two apparent defect images, and Harris corner point extraction algorithm, SUSAN corner point extraction algorithm or SIFT feature point extraction algorithm can be used;

When obtaining the coordinates of the image, two methods, interactive recognition and automatic feature matching, can be used. The advantage of interactive recognition is that it can accurately find the same feature point in two views. The disadvantage is that it cannot accurately determine the coordinates of the point. Automatic feature matching Matching is to use the feature point extraction and matching algorithm to accurately locate the feature points, but the matching result of the feature points may not be able to match the key position of the defect, so the feature point matching can be carried out through the automatic matching method first. can meet the requirements, and then use the method of interactive recognition for matching,

In the dual-CCD detection method, the matching of corresponding feature points is mainly the similarity of geometric primitives such as points, edges or regions in the two images, and then the image coordinates of the corresponding points formed by projecting the same feature point into the two images respectively , the spatial coordinates of the feature points can be calculated according to the mathematical model of the dual-CCD detection method;

(4) Evaluation method of structural apparent defect size:

After obtaining the spatial coordinates of the characteristic points of structural apparent defects, the length of the defect can be obtained according to the distance between two points in the space, and the coordinates of the two points in the space are respectively P ₁ (X ₁ , Y ₁ , Z ₁ ) , P ₂ (X ₂ , Y ₂ , Z ₂ ), then the length calculation formula is:

$\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; =</span>\sqrt{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

Depth measurement of defects first needs to establish a measurement reference plane, and the obtained depth is relative to this reference plane. Space plane, let the coordinates of three points in the space be P ₁ (X ₁ , Y ₁ , Z ₁ ), P ₂ (X ₂ , Y ₂ , Z ₂ ), P ₃ (X ₃ , Y ₃ , Z ₃ ), then the space plane equation is:

[(Y ₁ Z ₂ +Y ₂ Z ₃ +Y ₃ Z ₁ )-(Y ₃ Z ₂ +Y ₂ Z ₁ +Y ₁ Z ₃ )]X

+[(X ₁ Z ₂ +X ₂ Z ₃ +X ₃ Z ₁ )-(X ₂ Z ₂ +X ₂ Z.+X ₁ Z ₃ )]Y

+[(X ₁ Y ₂ +X ₂ Y ₃ +X ₃ Y ₁ )-(X ₃ Y ₁ +X ₂ Y ₁ +X ₃ Y3)]Z

+[(X ₁ Y ₂ Z ₃ +X ₂ Y ₃ Z ₁ +X ₃ Y ₁ Z ₃ )-(X ₃ Y ₂ Z ₁ +X ₂ Y ₁ Z ₃ +X ₁ Y ₃ Z ₂ )]＝0

(Y ₁ Z ₂ +Y ₂ Z ₃ +Y ₃ Z ₁ )-(Y ₃ Z ₂ +Y ₂ Z ₁ +Y ₁ Z ₃ )＝A

(X ₁ Z ₂ +X ₂ Z ₃ +X ₃ Z ₁ )-(X ₂ Z ₂ +X ₂ Z.+X ₁ Z ₃ )＝B

make

(X ₁ Y ₂ +X ₂ Y ₃ +X ₃ Y ₁ )-(X ₃ Y ₁ +X ₂ Y ₁ +X ₃ Y ₃ )＝C

(X ₁ Y ₂ Z ₃ +X ₂ Y ₃ Z ₁ +X ₃ Y ₁ Z ₃ )-(X ₃ Y ₂ Z ₁ +X ₂ Y ₁ Z ₃ +X ₁ Y ₃ Z ₂ )＝D

Then the plane equation is AX+BY+CZ+D=0,

Let the coordinates of the space point be K(X _k , Y _k , Z _k ), then the distance from the space point to the space plane is:

$\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Bb</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Cc</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; |</span>}{\sqrt{{\mathrm{<span\; class="notranslate">\; A</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}$

From this, the length, width and depth information of structural apparent defects are calculated,

Therefore, as long as the coordinates of the spatial points in the image are obtained, the three-dimensional coordinates of the spatial points can be calculated, and then the relative positional relationship of the spatial points can be obtained, and the damage assessment of the apparent defects of civil engineering structures is completed.

A dual-CCD inspection system for the evaluation of apparent defects in civil engineering structures consists of dual-CCD cameras, a bracket, a dual-channel image acquisition card, a computer and software for the detection and evaluation of apparent defects, wherein the dual-CCD cameras are installed on the bracket, and the dual-CCD The camera is connected to the dual-channel image acquisition card through wires, and the dual-channel image acquisition card is installed on the computer, and the detection system is controlled by the apparent defect detection and evaluation software to realize the acquisition, processing and evaluation of the structural apparent defect image; the dual CCD camera model The performance is the same, with higher image resolution, automatic gain control and background light automatic compensation function, and the size of the optical lens must match the size of the CCD sensor, the interface type must match, and it is a megapixel lens; the bracket can install two CCD camera, both sides are symmetrical and can move closer to the center at the same time, can realize the horizontal and pitch rotation of each camera; The described two-way image acquisition card can be an analog acquisition card or a digital acquisition card, and the interface type can be IEEE1394, Gigabit Network card or USB2.0. The apparent defect detection and evaluation software of the present invention is controlled by a computer to realize the functions of dual-channel image synchronous acquisition, display processing, feature matching, damage evaluation and interactive recognition, and measure the three-dimensional size of the apparent defect of the structure according to the apparent defect evaluation algorithm, and Provide structural apparent defect detection report.

In this implementation, combined with Figure 3, according to the actual inspection requirements of the structure, adjust the distance between the dual CCD camera bracket and the surface of the structure to be tested, and rotate the optical lens so that the dual CCD cameras can simultaneously display clear images of the measured defects on the structure surface . The computer collects the apparent defect image of the structure under test through the dual-channel synchronous acquisition of the apparent defect detection and evaluation software, reads the image, converts and stores it for display, and processes it with the defect image matching algorithm to realize the feature point extraction and matching of the dual-CCD defect image; according to the dual-CCD detection The algorithm calculates the spatial three-dimensional coordinates of defect image feature points, and evaluates the size of structural apparent defects through geometric relations. For structural apparent crack defects, the crack width can be measured by the defect damage assessment algorithm, and the straight line length or curve length of the crack can be evaluated; for structural apparent surface defects, in addition to measuring the length, width and depth of the three-dimensional dimension of the defect, the defect geometry can also be evaluated. area, and automatically provide the detection report of the apparent defect of the measured object.

Claims (1)

1. A double CCD detection method for civil engineering structure apparent defect assessment, characterized in that, the method is as follows: (1) Structural configuration method of dual CCD detection system for apparent defects: In order to obtain the spatial coordinates of structural apparent defect feature points from two-dimensional images, dual CCD cameras need to acquire two images containing structural apparent defect feature points from different positions; two CCD cameras are placed crosswise from different angles to observe the same For the object to be measured, first determine the viewing angle of a single CCD camera, and then design the baseline distance B and angle α between the two CCD cameras according to the actual situation of engineering applications to obtain the best public field of view. In order to obtain the actual detection For the angle of view of the CCD camera, it is necessary to make the CCD camera perpendicular to a plane, adjust the distance between the CCD camera and the surface of the structure to make the image clear, and let the optical axis of the CCD camera point to the center of the cross on the plane, in the direction perpendicular to the cross centers , place two rulers, and then take pictures, calculate the angle of view of the CCD camera in the horizontal and vertical directions according to the distance of the rulers that can be photographed in the image, and finally according to the baseline distance of the two CCD cameras, the CCD camera The common field of view of the dual-CCD detection system can be calculated from the included angle with the baseline and the viewing angle of the CCD camera; (2) Calculation method of feature point space coordinates of double CCD detection method: Double CCD cameras watch a certain feature point P on the surface of the structure at the same time, and use the left and right CCD cameras to obtain images of point P respectively. Their image coordinates are P _l = (X _l , Y _l ), P _r = (X _r , Y _r ), when the image planes of the two CCD cameras are on the same plane, the Y coordinates of the image coordinates of the feature point P are the same, that is, Y _left = Y _right = Y, obtained by the perspective transformation principle:

Then the parallax is: Disparity=|X _left -X _right |=X _left -X _right ; From this, the spatial coordinates of the structural surface feature points in the dual CCD detection system coordinate system are calculated as:

Therefore, as long as any point on the left CCD camera surface can find the corresponding matching point on the right CCD camera image surface, that is, the two are points on the left and right CCD cameras at the same spatial point, it can be determined according to the inherent geometric constraints of the dual CCD camera. Determine the spatial coordinates of the structural apparent defect feature points. This method is a point-to-point operation. As long as there are matching points for all points on the image, they can participate in the above operation, thereby obtaining the spatial coordinates of the structural apparent defect feature points. Therefore, the measurement higher efficiency; (3) Matching method of structural apparent defect image feature points: The matching of the feature points of the apparent defect image is to find the corresponding relationship between the feature points in the two images through the method of image matching, so as to determine the coordinates of the same feature point in the two images, and the characteristics of the defect image Matching requires feature extraction of two apparent defect images, using Harris corner point extraction algorithm, SUSAN corner point extraction algorithm or SIFT feature point extraction algorithm; When acquiring the coordinates of the image, two methods of interactive recognition and automatic feature matching are used. First, the automatic matching method is used to match the feature points. If the matching result cannot meet the requirements, then the interactive recognition method is used for matching. In the dual-CCD detection method, the matching of the corresponding feature points is mainly the similarity of the geometric primitives of the points, edges or regions in the two images, and then the image coordinates of the corresponding points formed by the same feature point being projected into the two images respectively , the spatial coordinates of the feature points can be calculated according to the mathematical model of the dual-CCD detection method; (4) Evaluation method for apparent defect size of structure: After obtaining the spatial coordinates of the characteristic points of structural apparent defects, the length of the defect is obtained according to the distance between two points in the space, and the coordinates of the two points in the space are respectively P ₁ (X ₁ , Y ₁ , Z ₁ ), P ₂ (X ₂ , Y ₂ , Z ₂ ), the length calculation formula is:

The depth measurement of defects first needs to establish a measurement reference plane, and the obtained depth is relative to this reference plane. plane, let the coordinates of three points in the space be P ₁ (X ₁ , Y ₁ , Z ₁ ), P ₂ (X ₂ , Y ₂ , Z ₂ ), P ₃ (X ₃ , Y ₃ , Z ₃ ) , then the space plane equation is: [(Y ₁ Z ₂ +Y ₂ Z ₃ +Y ₃ Z ₁ )-(Y ₃ Z ₂ +Y ₂ Z ₁ +Y ₁ Z ₃ )]X +[(X ₁ Z ₂ +X ₂ Z ₃ +X ₃ Z ₁ )-(X ₂ Z ₂ +X ₂ Z ₁ +X ₁ Z ₃ )]Y +[(X ₁ Y ₂ +X ₂ Y ₃ +X ₃ Y ₁ )-(X ₃ Y ₁ +X ₂ Y ₁ +X ₃ Y ₃ )]Z +[(X ₁ Y ₂ Z ₃ +X ₂ Y ₃ Z ₁ +X ₃ Y ₁ Z ₃ )-(X ₃ Y ₂ Z ₁ +X ₂ Y ₁ Z ₃ +X ₁ Y ₃ Z ₂ )]＝0 (Y ₁ Z ₂ +Y ₂ Z ₃ +Y ₃ Z ₁ )-(Y ₃ Z ₂ +Y ₂ Z ₁ +Y ₁ Z ₃ )＝A (X ₁ Z ₂ +X ₂ Z ₃ +X ₃ Z ₁ )-(X ₂ Z ₂ +X ₂ Z ₁ +X ₁ Z ₃ )＝B make (X ₁ Y ₂ +X ₂ Y ₃ +X ₃ Y ₁ )-(X ₃ Y ₁ +X ₂ Y ₁ +X ₃ Y ₃ )＝C (X ₁ Y ₂ Z ₃ +X ₂ Y ₃ Z ₁ +X ₃ Y ₁ Z ₃ )-(X ₃ Y ₂ Z ₁ +X ₂ Y ₁ Z ₃ +X ₁ Y ₃ Z ₂ )＝D Then the plane equation is AX+BY+CZ+D=0, Let the coordinates of the space point be K(X _k , Y _k , Z _k ), then the distance from the space point to the space plane is:

From this, the length, width and depth information of structural apparent defects are calculated, Therefore, as long as the coordinates of the spatial points in the image are obtained, the three-dimensional coordinates of the spatial points can be calculated, and then the relative positional relationship of the spatial points can be obtained, and the damage assessment of the apparent defects of civil engineering structures is completed. the

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