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CN116242253A - Underwater concrete apparent laser line three-dimensional scanning measurement method - Google Patents

Underwater concrete apparent laser line three-dimensional scanning measurement methodDownload PDF

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CN116242253A
CN116242253ACN202310527270.7ACN202310527270ACN116242253ACN 116242253 ACN116242253 ACN 116242253ACN 202310527270 ACN202310527270 ACN 202310527270ACN 116242253 ACN116242253 ACN 116242253A
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laser line
laser
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CN116242253B (en
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林海涛
陈永灿
张华�
李林静
陈波
周怀芳
霍建文
徐鹏
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Southwest University of Science and Technology
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Abstract

The invention discloses a three-dimensional scanning measurement method of an apparent laser line of underwater concrete, which comprises the following steps: s1, performing laser line plane calibration on laser line scanning imaging equipment in a clear water replacement device, and constructing a laser plane equation; s2, establishing a ray tracing model of rays on the surfaces of different media, and further establishing a multi-medium refraction model between a real image point and a camera imaging point; s3, fusing the multi-medium refraction model with the camera imaging model to obtain a normalization model of underwater imaging; s4, converting the obtained apparent laser line image of the underwater concrete into a laser line image in corresponding air by using a normalization model and a laser plane equation, and realizing three-dimensional scanning measurement of the apparent laser line of the underwater concrete. The method eliminates the influence of turbid water environment on laser line scanning, establishes a normalized model of laser line scanning imaging, and eliminates the influence of refractive distortion.

Description

Translated fromChinese
一种水下混凝土表观激光线三维扫描测量方法A laser line three-dimensional scanning measurement method for the surface of underwater concrete

技术领域technical field

本发明属于水基础设施安全测量技术领域，具体涉及一种水下混凝土表观激光线三维扫描测量方法。The invention belongs to the technical field of water infrastructure safety measurement, and in particular relates to a three-dimensional scanning measurement method of underwater concrete surface laser line.

背景技术Background technique

高坝大库、桥梁港口、输引水隧洞等是保障防洪安全、支撑水资源综合开发利用的重大涉水基础设施。在长期服役过程中，由地震、地质、洪涝等灾害引起基础设施水下混凝土结构缺陷，如裂缝、冲坑、磨蚀、露筋等，是影响工程安全运行的关键，需要及时、准确的缺陷检测和隐患排查。目前水下混凝土表观三维测量主要采用激光扫描的方法进行测量，但在自然流域中由于水体浑浊以及水体对激光线的吸收与散射，导致水下激光线三维扫描并不能采集到有效的三维点云数据。High dams, large reservoirs, bridges and ports, and water transmission and diversion tunnels are major wading infrastructures that ensure flood control safety and support the comprehensive development and utilization of water resources. During the long-term service, the defects of the underwater concrete structure of the infrastructure caused by earthquakes, geology, floods and other disasters, such as cracks, scoured pits, abrasions, exposed bars, etc., are the key to the safe operation of the project, and timely and accurate defect detection is required and hidden danger investigation. At present, the apparent three-dimensional measurement of underwater concrete is mainly carried out by laser scanning method. However, in natural watersheds, due to the turbidity of the water body and the absorption and scattering of the laser line by the water body, the effective three-dimensional point cannot be collected by underwater laser line three-dimensional scanning. cloud data.

利用当前的水下激光线三维扫描设备在清水环境中能采集到点云图象数据，但是由于在不同的水域环境中水体溶解杂质不同介质的折射率也不同，因此在不同清水环境中采集到的点云图像数据其测量精度也不能有效保证。The current underwater laser line 3D scanning equipment can collect point cloud image data in clear water environments. However, due to the different refractive indices of dissolved impurities in water bodies and different media in different water environments, the data collected in different clear water environments The measurement accuracy of the point cloud image data cannot be effectively guaranteed.

发明内容Contents of the invention

针对现有技术中的上述不足，本发明提供的水下混凝土表观激光线三维扫描测量方法消除了浊水环境对激光线扫描的影响，建立了激光线扫描成像的归一化模型消除了折射畸变的影响。In view of the above-mentioned deficiencies in the prior art, the three-dimensional laser line scanning measurement method for the underwater concrete surface provided by the present invention eliminates the influence of the turbid water environment on the laser line scan, and establishes a normalized model of the laser line scan imaging to eliminate the refraction Distortion effects.

为了达到上述发明目的，本发明采用的技术方案为：一种水下混凝土表观激光线三维扫描测量方法，包括以下步骤In order to achieve the purpose of the above invention, the technical solution adopted in the present invention is: a method for measuring the apparent laser line three-dimensional scanning of underwater concrete, comprising the following steps

S1、对清水置换装置内的激光线扫描成像设备进行激光线平面标定，构建激光平面方程；S1. Calibrate the laser line plane of the laser line scan imaging equipment in the clean water replacement device, and construct the laser plane equation;

S2、建立光线在不同介质表面的光线追踪模型，进而建立真实像点与相机成像点之间的多介质折射模型；S2. Establish a ray tracing model of light on the surface of different media, and then establish a multi-media refraction model between the real image point and the camera imaging point;

S3、将多介质折射模型与相机成像模型融合，获得水下成像的归一化模型；S3. Merging the multi-media refraction model with the camera imaging model to obtain a normalized model for underwater imaging;

S4、利用归一化模型和激光平面方程将获取的水下混凝土表观激光线图像转换至对应空气中的激光线图像中，实现水下混凝土表观激光线三维扫描测量。S4. Using the normalized model and the laser plane equation, the obtained underwater concrete apparent laser line image is converted into the corresponding laser line image in the air, so as to realize the three-dimensional scanning measurement of the underwater concrete apparent laser line.

进一步地，所述步骤S1具体为：Further, the step S1 is specifically:

S11、将激光线扫描成像设备密封置于清水置换装置中；S11. Sealing the laser line scan imaging device in the water replacement device;

其中，清水置换装置为内含清水的玻璃块组成的密封结构，用于放置激光扫描成像设备，当水域水质浑浊影响激光扫描成像设备成像时，通过清水置换装置中的清水替换激光扫描成像设备中相机与被测物体间的浑浊水，以获取被测物体的清晰成像；Among them, the clear water replacement device is a sealed structure composed of glass blocks containing clear water, which is used to place the laser scanning imaging equipment. When the water quality in the water area is turbid and affects the imaging of the laser scanning imaging equipment, the clean water in the clear water replacement device replaces the laser scanning imaging equipment. The turbid water between the camera and the measured object to obtain a clear image of the measured object;

S12、利用激光线扫描成像设备扫描获取图像对相机参数进行标定；S12. Using a laser line scan imaging device to scan and obtain an image to calibrate the camera parameters;

S13、基于参数标定的相机，利用交比不变性对激光平面方程进行标定，构建激光平面方程。S13. Based on the parameter calibration camera, the laser plane equation is calibrated by using cross-ratio invariance, and the laser plane equation is constructed.

进一步地，所述步骤S11中，激光线扫描成像设备中的激光线在相机视场所成的像在视野正中央。Further, in the step S11, the image formed by the laser line in the laser line scanning imaging device in the field of view of the camera is in the center of the field of view.

进一步地，所述步骤S13中，交比不变性的表达式为：Further, in the step S13, the expression of cross-ratio invariance is:

Figure SMS_1
Figure SMS_1

式中，

Figure SMS_2
为交比函数，/>
Figure SMS_3
为世界坐标系下的点，/>
Figure SMS_4
为Q对应图像坐标系下的点，下标i为点的序号；其中，Q为进行激光线平面标定时需要确定的特征点；In the formula,
Figure SMS_2
is the ratio function, />
Figure SMS_3
is a point in the world coordinate system, />
Figure SMS_4
is the point under the image coordinate system corresponding toQ , and the subscripti is the serial number of the point; wherein,Q is the feature point that needs to be determined when performing laser line plane calibration;

所述步骤S13中，对激光平面方程进行标定的方法为：In the step S13, the method for calibrating the laser plane equation is:

利用激光线与标定板的角点的交线确定Q点在图像坐标系中的坐标，利用交比不变性确定Q点在世界坐标系中的坐标，进而利用三张不同角度标定板与激光线交线确定三个不同的Q点，进而获得标定的激光线平面方程；Use the intersection line of the laser line and the corner point of the calibration plate to determine the coordinates ofthe Q point in the image coordinate system, use the cross-ratio invariance to determine the coordinates ofthe Q point in the world coordinate system, and then use three different angle calibration plates and laser lines The intersection line determines three differentQ points, and then obtains the calibrated laser line plane equation;

Figure SMS_5
Figure SMS_5

式中，A,B,C,D均为激光平面方程中的待定系数，x,y,z为平面任意的三维点。In the formula,A, B, C, and D are undetermined coefficients in the laser plane equation, andx, y, and z are arbitrary three-dimensional points on the plane.

进一步地，所述步骤S2中的光线追踪模型的表达式为：Further, the expression of the ray tracing model in the step S2 is:

Figure SMS_6
Figure SMS_6

Figure SMS_7
Figure SMS_7

式中，

Figure SMS_9
为成像的像点位置，/>
Figure SMS_13
为有机玻璃的厚度，/>
Figure SMS_16
为成像目标位于水中经过第一次折射后光线与交界面的夹角，/>
Figure SMS_11
为相机与有机玻璃之间的夹角，/>
Figure SMS_14
为相机焦距，/>
Figure SMS_18
为水中折射角，/>
Figure SMS_21
为成像目标点的世界坐标，/>
Figure SMS_8
为成像目标点与相机的距离，/>
Figure SMS_12
为成像目标点入射光线与交界法线的夹角，/>
Figure SMS_17
为水中的折射率，/>
Figure SMS_20
为有机玻璃的折射率，/>
Figure SMS_10
为空气中的折射率，/>
Figure SMS_15
为真实的像点位置，/>
Figure SMS_19
为成像目标点位于空气中经过第一次折射后光线与交界法线的夹角，/>
Figure SMS_22
为物体位于空气时经过第二次折射后光线与折射面法线的夹角。In the formula,
Figure SMS_9
is the imaging point position, />
Figure SMS_13
is the thickness of plexiglass, />
Figure SMS_16
is the angle between the light and the interface after the first refraction of the imaging target in water, />
Figure SMS_11
is the angle between the camera and the plexiglass, />
Figure SMS_14
is the focal length of the camera, />
Figure SMS_18
is the angle of refraction in water, />
Figure SMS_21
is the world coordinate of the imaging target point, />
Figure SMS_8
is the distance between the imaging target point and the camera, />
Figure SMS_12
is the angle between the incident light at the imaging target point and the boundary normal, />
Figure SMS_17
is the refractive index in water, />
Figure SMS_20
is the refractive index of organic glass, />
Figure SMS_10
is the refractive index in air, />
Figure SMS_15
is the real image point position, />
Figure SMS_19
is the angle between the ray and the boundary normal after the first refraction of the imaging target point in the air, />
Figure SMS_22
It is the angle between the light and the normal line of the refraction surface after the second refraction when the object is in the air.

进一步地，所述步骤S2中的多介质折射模型的表达式为：Further, the expression of the multi-medium refraction model in the step S2 is:

Figure SMS_23
。
Figure SMS_23
.

进一步地，所述步骤S3中，归一化模型的表达式为：Further, in the step S3, the expression of the normalized model is:

Figure SMS_24
Figure SMS_24

式中，

Figure SMS_38
为/>
Figure SMS_30
，/>
Figure SMS_34
为像素点对应的相机坐标系下Z轴的值，/>
Figure SMS_33
为像素坐标横坐标，
Figure SMS_39
为相机中心点横坐标，/>
Figure SMS_37
为像素坐标纵坐标，/>
Figure SMS_40
为相机中心点纵坐标，/>
Figure SMS_28
为使用像素来描述x轴方向焦距的长度，/>
Figure SMS_36
为使用像素来描述y轴方向焦距的长度，/>
Figure SMS_25
为3x3的旋转矩阵，G为1x3的平移矩阵，/>
Figure SMS_31
为世界坐标X轴的值，/>
Figure SMS_26
为世界坐标Y轴的值，/>
Figure SMS_32
为世界坐标Z轴的值；其中，/>
Figure SMS_29
，/>
Figure SMS_35
为空气折射率，/>
Figure SMS_27
为水的折射率；In the formula,
Figure SMS_38
for />
Figure SMS_30
, />
Figure SMS_34
is the value of the Z axis in the camera coordinate system corresponding to the pixel point, />
Figure SMS_33
is the pixel coordinate abscissa,
Figure SMS_39
The abscissa of the camera center point, />
Figure SMS_37
is the pixel coordinate ordinate, />
Figure SMS_40
is the vertical coordinate of the camera center point, />
Figure SMS_28
To use pixels to describe the length of the focal length in the x-axis direction, />
Figure SMS_36
To use pixels to describe the length of the focal length in the y-axis direction, />
Figure SMS_25
is a 3x3 rotation matrix,G is a 1x3 translation matrix, />
Figure SMS_31
is the value of the world coordinate X axis, />
Figure SMS_26
is the value of the world coordinate Y axis, />
Figure SMS_32
is the value of the world coordinate Z axis; where, />
Figure SMS_29
, />
Figure SMS_35
is the refractive index of air, />
Figure SMS_27
is the refractive index of water;

Figure SMS_41
，/>
Figure SMS_42
为玻璃折射率；
Figure SMS_41
, />
Figure SMS_42
is the glass refractive index;

Figure SMS_43
，/>
Figure SMS_44
为成像目标点的图像坐标系下的/>
Figure SMS_45
值；
Figure SMS_43
, />
Figure SMS_44
is the image coordinate system of the imaging target point />
Figure SMS_45
value;

Figure SMS_46
，/>
Figure SMS_47
，/>
Figure SMS_48
，T为玻璃厚度，/>
Figure SMS_49
、/>
Figure SMS_50
分别为光路在玻璃的折射角度沿x,y轴方向的角度，/>
Figure SMS_51
、/>
Figure SMS_52
分别为图像坐标系下x,y对应值，d为相机光心到玻璃的距离。
Figure SMS_46
, />
Figure SMS_47
, />
Figure SMS_48
,T is the glass thickness, />
Figure SMS_49
, />
Figure SMS_50
Respectively, the refraction angle of the optical path in the glass alongthe x and y axis directions, />
Figure SMS_51
, />
Figure SMS_52
are the corresponding values ofx and y in the image coordinate system,and d is the distance from the optical center of the camera to the glass.

进一步地，所述步骤S4具体为：Further, the step S4 is specifically:

S41、利用完成参数标定的相机获取水下混凝土表观激光线图像；S41. Acquire the apparent laser line image of the underwater concrete by using the camera whose parameters have been calibrated;

S42、利用归一化模型对激光线图像中的像素坐标进行转换，获得消除畸变像素坐标的激光线图像；S42. Using the normalization model to convert the pixel coordinates in the laser line image to obtain the laser line image with the pixel coordinates of the distortion eliminated;

S43、对消除畸变像素坐标的激光线图像依次进行闭运算和骨架提取，获得无缺损激光线图像；S43. Perform closed operation and skeleton extraction on the laser line image with the pixel coordinates of the distortion eliminated in sequence to obtain a defect-free laser line image;

S44、利用灰度重心法对无缺损激光线图像提取激光线；S44. Using the gray-scale centroid method to extract laser lines from the defect-free laser line image;

S45、将提取的激光线中的像素点坐标带入激光平面方程，得到单列像素激光的三维坐标；S45. Bringing the pixel point coordinates in the extracted laser line into the laser plane equation to obtain the three-dimensional coordinates of the single-column pixel laser;

S46、将连续多帧激光线的三维坐标进行拼接，获得目标区域内水下混凝土的三维点云坐标，实现三维扫描测量。S46. Splicing the three-dimensional coordinates of the continuous multiple frames of laser lines to obtain the three-dimensional point cloud coordinates of the underwater concrete in the target area, so as to realize three-dimensional scanning measurement.

本发明的有益效果为：The beneficial effects of the present invention are:

1.本发明建立了归一化模型实现成像点与真实像点之间的转换，传统方法通过相机标定来减小误差，但是多介质折射影响不能完全通过畸变来消除。1. The present invention establishes a normalized model to realize the conversion between the imaging point and the real image point. The traditional method reduces the error through camera calibration, but the influence of multi-media refraction cannot be completely eliminated through distortion.

2.本发明中将激光线扫描设备放置在了清水置换装置内部，消除了浊水环境的激光线扫描的影响。2. In the present invention, the laser line scanning equipment is placed inside the clear water replacement device, which eliminates the influence of the laser line scanning in the turbid water environment.

3.本发明中水下激光线扫描设备图像传输采用网络传输，能极大程度的降低图像数据传输的延时。3. The image transmission of the underwater laser line scanning equipment in the present invention adopts network transmission, which can greatly reduce the delay of image data transmission.

附图说明Description of drawings

图1为本发明提供的水下混凝土表观激光线三维扫描测量方法流程图。Fig. 1 is a flow chart of the three-dimensional laser line scanning measurement method for the appearance of underwater concrete provided by the present invention.

图2为本发明提供的激光线扫描成像设备示意图。FIG. 2 is a schematic diagram of a laser line scan imaging device provided by the present invention.

图3为本发明提供的激光线平面标定示意图。Fig. 3 is a schematic diagram of laser line plane calibration provided by the present invention.

图4为本发明提供的光线追踪模型示意图。Fig. 4 is a schematic diagram of a ray tracing model provided by the present invention.

其中：1、电机；2、轴联器；3、黑白相机；4、532nm激光；5、彩色相机；6、固定板；7、丝杠；8、编码器；9、滑台。Among them: 1. Motor; 2. Coupling; 3. Black and white camera; 4. 532nm laser; 5. Color camera; 6. Fixed plate; 7. Lead screw; 8. Encoder; 9. Sliding table.

具体实施方式Detailed ways

下面对本发明的具体实施方式进行描述，以便于本技术领域的技术人员理解本发明，但应该清楚，本发明不限于具体实施方式的范围，对本技术领域的普通技术人员来讲，只要各种变化在所附的权利要求限定和确定的本发明的精神和范围内，这些变化是显而易见的，一切利用本发明构思的发明创造均在保护之列。The specific embodiments of the present invention are described below so that those skilled in the art can understand the present invention, but it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes Within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are included in the protection list.

本发明实施例提供了一种水下混凝土表观激光线三维扫描测量方法，如图1所示，包括以下步骤The embodiment of the present invention provides a three-dimensional scanning measurement method of underwater concrete surface laser line, as shown in Figure 1, including the following steps

S1、对清水置换装置内的激光线扫描成像设备进行激光线平面标定，构建激光平面方程；S1. Calibrate the laser line plane of the laser line scan imaging equipment in the clean water replacement device, and construct the laser plane equation;

S2、建立光线在不同介质表面的光线追踪模型，进而建立真实像点与相机成像点之间的多介质折射模型；S2. Establish a ray tracing model of light on the surface of different media, and then establish a multi-media refraction model between the real image point and the camera imaging point;

S3、将多介质折射模型与相机成像模型融合，获得水下成像的归一化模型；S3. Merging the multi-media refraction model with the camera imaging model to obtain a normalized model for underwater imaging;

S4、利用归一化模型和激光平面方程将获取的水下混凝土表观激光线图像转换至对应空气中的激光线图像中，实现水下混凝土表观激光线三维扫描测量。S4. Using the normalized model and the laser plane equation, the obtained underwater concrete apparent laser line image is converted into the corresponding laser line image in the air, so as to realize the three-dimensional scanning measurement of the underwater concrete apparent laser line.

本发明实施例的步骤S1具体为：Step S1 of the embodiment of the present invention is specifically:

S11、将激光线扫描成像设备密封置于清水置换装置中；S11. Sealing the laser line scan imaging device in the water replacement device;

其中，清水置换装置为内含清水的玻璃块组成的密封结构，用于放置激光扫描成像设备，当水域水质浑浊影响激光扫描成像设备成像时，通过清水置换装置中的清水替换激光扫描成像设备中相机与被测物体间的浑浊水，以获取被测物体的清晰成像；Among them, the clear water replacement device is a sealed structure composed of glass blocks containing clear water, which is used to place the laser scanning imaging equipment. When the water quality in the water area is turbid and affects the imaging of the laser scanning imaging equipment, the clean water in the clear water replacement device replaces the laser scanning imaging equipment. The turbid water between the camera and the measured object to obtain a clear image of the measured object;

S12、利用激光线扫描成像设备扫描获取图像对相机参数进行标定；S12. Using a laser line scan imaging device to scan and obtain an image to calibrate the camera parameters;

S13、基于参数标定的相机，利用交比不变性对激光平面方程进行标定，构建激光平面方程。S13. Based on the parameter calibration camera, the laser plane equation is calibrated by using cross-ratio invariance, and the laser plane equation is constructed.

在本发明实施例中，激光线扫描成像设备结构如图2所示，包括电机、轴联器、黑白相机、彩色相机、532nm激光以及编码器；其中，532nm激光、黑白相机以及彩色相机均固定在固定板上，且532nm激光设置在黑白相机和彩色相机之间，固定板固定在滑台上，使相机与532nm激光能够在滑台上自由移动；具体地，滑台上设置有丝杠、编码器和轴联器，固定板设置在丝杠上，丝杠的一端与编码器连接，另一端通过轴联器与电机连接，轴联器在电机的转动下驱动固定板在丝杠上左右移动，并由编码器记录并反馈电机工作参数，进而控制电机工作以调整固定板的位置。In the embodiment of the present invention, the structure of the laser line scan imaging device is shown in Figure 2, including a motor, a coupling, a black and white camera, a color camera, a 532nm laser, and an encoder; wherein, the 532nm laser, the black and white camera, and the color camera are all fixed On the fixed plate, and the 532nm laser is set between the black-and-white camera and the color camera, the fixed plate is fixed on the slide table, so that the camera and the 532nm laser can move freely on the slide table; specifically, the slide table is provided with a screw, Encoder and shaft coupling, the fixed plate is set on the screw, one end of the screw is connected to the encoder, the other end is connected to the motor through the shaft coupling, and the shaft coupling drives the fixed plate to the left and right on the screw under the rotation of the motor Move, and the encoder records and feeds back the working parameters of the motor, and then controls the work of the motor to adjust the position of the fixed plate.

在本实施例的步骤S11中，基于上述激光线扫描成像设备的结构，其中激光线在相机（彩色相机和黑白相机）视场所成的像在视野正中央。In step S11 of this embodiment, based on the structure of the above-mentioned laser line scanning imaging device, the image formed by the laser line in the field of view of the camera (color camera and black and white camera) is in the center of the field of view.

在本实施例的步骤S11中，将上述激光线扫描成像设备密封在有机玻璃内部，并放置于清水置换装置中。In step S11 of this embodiment, the above-mentioned laser line scan imaging device is sealed inside the plexiglass and placed in a water replacement device.

在本实施例的步骤S13中，基于图3所示相机成像示意图，图中标定板指带棋盘格的标准板子，Li表示激光线在标定板上所呈现的直线条，li为Li在相机成像面上所呈现的直线段；得到在对激光线平面标定时的交比不变性的表达式为：In step S13 of this embodiment, based on the schematic diagram of camera imaging shown in FIG. 3 , the calibration board in the figure refers to a standard board with checkerboard grids,Li represents the straight line presented by the laser line on the calibration board, andli isLi The straight line segment presented on the imaging surface of the camera; the expression of the cross-ratio invariance when the laser line plane is calibrated is obtained as:

Figure SMS_53
Figure SMS_53

式中，

Figure SMS_54
为交比函数，/>
Figure SMS_55
为世界坐标系下的点，/>
Figure SMS_56
为Q对应图像坐标系下的点，下标i为点的序号；其中，Q为进行激光线平面标定时需要确定的特征点；In the formula,
Figure SMS_54
is the ratio function, />
Figure SMS_55
is a point in the world coordinate system, />
Figure SMS_56
is the point under the image coordinate system corresponding toQ , and the subscripti is the serial number of the point; wherein,Q is the feature point that needs to be determined when performing laser line plane calibration;

所述步骤S13中，对激光平面方程进行标定的方法为：In the step S13, the method for calibrating the laser plane equation is:

利用激光线与标定板的角点的交线确定Q点在图像坐标系中的坐标，利用交比不变性确定Q点在世界坐标系中的坐标，进而利用三张不同角度标定板与激光线交线确定三个不同的Q点，进而获得标定的激光线平面方程；Use the intersection line of the laser line and the corner point of the calibration plate to determine the coordinates ofthe Q point in the image coordinate system, use the cross-ratio invariance to determine the coordinates ofthe Q point in the world coordinate system, and then use three different angle calibration plates and laser lines The intersection line determines three differentQ points, and then obtains the calibrated laser line plane equation;

Figure SMS_57
Figure SMS_57

式中，A,B,C,D均为激光平面方程中的待定系数，x,y,z为平面任意的三维点。In the formula,A, B, C, and D are undetermined coefficients in the laser plane equation, andx, y, and z are arbitrary three-dimensional points on the plane.

由于清水置换装置能够消除水体浑浊对图像采集产生的影响，因此拍摄的激光线将不受水体环境对拍摄图像的影响。Since the clear water replacement device can eliminate the impact of water turbidity on image acquisition, the captured laser line will not be affected by the water environment on the captured image.

在本发明实施例中，由于光线在不同介质表面会产生折射现象，为此相机在空气中的成像模型不能准确的表达水下的真实成像情况，因此发明实施例中构建了用于水下成像的归一化模型，以消除折射畸变的影响，提升混凝土表观描精度。In the embodiment of the present invention, due to the refraction of light on the surface of different media, the imaging model of the camera in the air cannot accurately express the real imaging situation underwater. The normalized model is used to eliminate the influence of refraction distortion and improve the apparent drawing accuracy of concrete.

具体地，本发明实施的步骤S2采用snell定律建立光线在不同介质表面的光线追踪模型，利用光线追踪模型建立真实像点与相机成像点之间的多介质折射关系；其中，光线追踪模型的如图4所示，其表达式为：Specifically, step S2 implemented in the present invention adopts Snell's law to establish a ray tracing model of light on different medium surfaces, and uses the ray tracing model to establish the multi-media refraction relationship between the real image point and the camera imaging point; wherein, the ray tracing model is as follows: As shown in Figure 4, its expression is:

Figure SMS_58
Figure SMS_58

Figure SMS_59
Figure SMS_59

式中，

Figure SMS_62
为成像的像点位置，/>
Figure SMS_65
为有机玻璃的厚度，/>
Figure SMS_69
为成像目标位于水中经过第一次折射后光线与交界面的夹角，/>
Figure SMS_63
为相机与有机玻璃之间的夹角，/>
Figure SMS_67
为相机焦距，/>
Figure SMS_71
为水中折射角，/>
Figure SMS_74
为成像目标点的世界坐标，/>
Figure SMS_60
为成像目标点与相机的距离，/>
Figure SMS_64
为成像目标点入射光线与交界法线的夹角，/>
Figure SMS_68
为水中的折射率，/>
Figure SMS_72
为有机玻璃的折射率，/>
Figure SMS_61
为空气中的折射率，/>
Figure SMS_66
为真实的像点位置，/>
Figure SMS_70
为成像目标点位于空气中经过第一次折射后光线与交界法线的夹角，/>
Figure SMS_73
为物体位于空气时经过第二次折射后光线与折射面法线的夹角。In the formula,
Figure SMS_62
is the imaging point position, />
Figure SMS_65
is the thickness of plexiglass, />
Figure SMS_69
is the angle between the light and the interface after the first refraction of the imaging target in water, />
Figure SMS_63
is the angle between the camera and the plexiglass, />
Figure SMS_67
is the focal length of the camera, />
Figure SMS_71
is the angle of refraction in water, />
Figure SMS_74
is the world coordinate of the imaging target point, />
Figure SMS_60
is the distance between the imaging target point and the camera, />
Figure SMS_64
is the angle between the incident light at the imaging target point and the boundary normal, />
Figure SMS_68
is the refractive index in water, />
Figure SMS_72
is the refractive index of organic glass, />
Figure SMS_61
is the refractive index in air, />
Figure SMS_66
is the real image point position, />
Figure SMS_70
is the angle between the ray and the boundary normal after the first refraction of the imaging target point in the air, />
Figure SMS_73
It is the angle between the light and the normal line of the refraction surface after the second refraction when the object is in the air.

基于光线追踪模型构建的多介质折射模型的表达式为：The expression of the multi-medium refraction model based on the ray tracing model is:

Figure SMS_75
。
Figure SMS_75
.

在本实施例的步骤S3中，将多介质折射模型与相机成像模型融合，形成的水下成像的归一化模型；In step S3 of this embodiment, the multi-media refraction model is fused with the camera imaging model to form a normalized model for underwater imaging;

其中，对于没有介质折射时的相机成像模型为：Among them, the camera imaging model without medium refraction is:

Figure SMS_76
Figure SMS_76

式中，

Figure SMS_78
为目标点的相机坐标系的Z轴值，/>
Figure SMS_82
为像素坐标横坐标，/>
Figure SMS_86
为像素坐标纵坐标，/>
Figure SMS_79
为像素坐标系横坐标畸变，/>
Figure SMS_81
为像素坐标系纵坐标畸变，/>
Figure SMS_85
为成像面上对光轴的角度，/>
Figure SMS_89
为相机中心点横坐标，/>
Figure SMS_77
为相机中心点纵坐标，/>
Figure SMS_83
为目标点世界坐标x值，/>
Figure SMS_87
为目标点世界坐标y值，/>
Figure SMS_90
为目标点世界坐标z值，/>
Figure SMS_80
为3x3的旋转矩阵，/>
Figure SMS_84
为1x3的平移矩阵，/>
Figure SMS_88
为3x3的0矩阵。In the formula,
Figure SMS_78
is the Z-axis value of the camera coordinate system of the target point, />
Figure SMS_82
is the abscissa of pixel coordinates, />
Figure SMS_86
is the pixel coordinate ordinate, />
Figure SMS_79
is the abscissa distortion of the pixel coordinate system, />
Figure SMS_81
is the vertical coordinate distortion of the pixel coordinate system, />
Figure SMS_85
is the angle of the imaging plane to the optical axis, />
Figure SMS_89
The abscissa of the camera center point, />
Figure SMS_77
is the vertical coordinate of the camera center point, />
Figure SMS_83
is the world coordinate x value of the target point, />
Figure SMS_87
is the world coordinate y value of the target point, />
Figure SMS_90
is the world coordinate z value of the target point, />
Figure SMS_80
is a 3x3 rotation matrix, />
Figure SMS_84
is a 1x3 translation matrix, />
Figure SMS_88
It is a 3x3 matrix of 0.

多介质折射模型与相机成像模型融合的归一化模型的表达式为：The expression of the normalized model for the fusion of the multi-media refraction model and the camera imaging model is:

Figure SMS_91
Figure SMS_91

式中，

Figure SMS_96
为/>
Figure SMS_93
，/>
Figure SMS_99
为像素点对应的相机坐标系下Z轴的值，/>
Figure SMS_95
为像素坐标横坐标，
Figure SMS_102
为相机中心点横坐标，/>
Figure SMS_98
为像素坐标纵坐标，/>
Figure SMS_104
为相机中心点纵坐标，/>
Figure SMS_105
为使用像素来描述x轴方向焦距的长度，/>
Figure SMS_107
为使用像素来描述y轴方向焦距的长度，/>
Figure SMS_92
为3x3的旋转矩阵，G为1x3的平移矩阵，/>
Figure SMS_103
为世界坐标X轴的值，/>
Figure SMS_97
为世界坐标Y轴的值，/>
Figure SMS_101
为世界坐标Z轴的值；其中，/>
Figure SMS_100
，/>
Figure SMS_106
为空气折射率，/>
Figure SMS_94
为水的折射率；In the formula,
Figure SMS_96
for />
Figure SMS_93
, />
Figure SMS_99
is the value of the Z axis in the camera coordinate system corresponding to the pixel point, />
Figure SMS_95
is the pixel coordinate abscissa,
Figure SMS_102
The abscissa of the camera center point, />
Figure SMS_98
is the pixel coordinate ordinate, />
Figure SMS_104
is the vertical coordinate of the camera center point, />
Figure SMS_105
To use pixels to describe the length of the focal length in the x-axis direction, />
Figure SMS_107
To use pixels to describe the length of the focal length in the y-axis direction, />
Figure SMS_92
is a 3x3 rotation matrix,G is a 1x3 translation matrix, />
Figure SMS_103
is the value of the world coordinate X axis, />
Figure SMS_97
is the value of the world coordinate Y axis, />
Figure SMS_101
is the value of the world coordinate Z axis; where, />
Figure SMS_100
, />
Figure SMS_106
is the refractive index of air, />
Figure SMS_94
is the refractive index of water;

Figure SMS_108
，/>
Figure SMS_109
为玻璃折射率；
Figure SMS_108
, />
Figure SMS_109
is the glass refractive index;

Figure SMS_110
，/>
Figure SMS_111
为成像目标点的图像坐标系下的/>
Figure SMS_112
值；
Figure SMS_110
, />
Figure SMS_111
is the image coordinate system of the imaging target point />
Figure SMS_112
value;

Figure SMS_113
，/>
Figure SMS_117
，/>
Figure SMS_121
，T为玻璃厚度，/>
Figure SMS_114
、/>
Figure SMS_118
分别为光路在玻璃的折射角度沿x,y轴方向的角度，/>
Figure SMS_122
、/>
Figure SMS_124
分别为图像坐标系下x,y对应值，d为相机光心到玻璃的距离。在图4中，/>
Figure SMS_115
为目标位于空气中时经过第二次折射后光线与玻璃——空气交界面法线的夹角，/>
Figure SMS_120
表示目标点处于空气中时其成像点的相机坐标系，/>
Figure SMS_123
为空气中成像点成像面上像素点到相机光轴中心的距离，/>
Figure SMS_125
为表示目标处于水中时其成像点的相机坐标系坐标，/>
Figure SMS_116
为水中成像点成像面上像素点到相机光轴中心的距离，/>
Figure SMS_119
为表示目标点的世界坐标系坐标。
Figure SMS_113
, />
Figure SMS_117
, />
Figure SMS_121
,T is the glass thickness, />
Figure SMS_114
, />
Figure SMS_118
Respectively, the refraction angle of the optical path in the glass alongthe x and y axis directions, />
Figure SMS_122
, />
Figure SMS_124
are the corresponding values ofx and y in the image coordinate system,and d is the distance from the optical center of the camera to the glass. In Figure 4, />
Figure SMS_115
is the included angle between the light and the normal line of the glass-air interface after the second refraction when the target is in the air, />
Figure SMS_120
Indicates the camera coordinate system of the imaging point when the target point is in the air, />
Figure SMS_123
is the distance from the pixel point on the imaging surface of the imaging point in the air to the center of the optical axis of the camera, />
Figure SMS_125
To represent the camera coordinate system coordinates of the imaging point when the target is in water, />
Figure SMS_116
is the distance from the pixel on the imaging surface of the imaging point in water to the center of the optical axis of the camera, />
Figure SMS_119
is the world coordinate system coordinate representing the target point.

本发明实施例的步骤S4具体为：Step S4 of the embodiment of the present invention is specifically:

S41、利用完成参数标定的相机获取水下混凝土表观激光线图像；S41. Acquire the apparent laser line image of the underwater concrete by using the camera whose parameters have been calibrated;

S42、利用归一化模型对激光线图像中的像素坐标进行转换，获得消除畸变像素坐标的激光线图像；S42. Using the normalization model to convert the pixel coordinates in the laser line image to obtain the laser line image with the pixel coordinates of the distortion eliminated;

S43、对消除畸变像素坐标的激光线图像依次进行闭运算和骨架提取，获得无缺损激光线图像；S43. Perform closed operation and skeleton extraction on the laser line image with the pixel coordinates of the distortion eliminated in sequence to obtain a defect-free laser line image;

S44、利用灰度重心法对无缺损激光线图像提取激光线；S44. Using the gray-scale centroid method to extract laser lines from the defect-free laser line image;

S45、将提取的激光线中的像素点坐标带入激光平面方程，得到单列像素激光的三维坐标；S45. Bringing the pixel point coordinates in the extracted laser line into the laser plane equation to obtain the three-dimensional coordinates of the single-column pixel laser;

S46、将连续多帧激光线的三维坐标进行拼接，获得目标区域内水下混凝土的三维点云坐标，实现三维扫描测量。S46. Splicing the three-dimensional coordinates of the continuous multiple frames of laser lines to obtain the three-dimensional point cloud coordinates of the underwater concrete in the target area, so as to realize three-dimensional scanning measurement.

本发明中应用了具体实施例对本发明的原理及实施方式进行了阐述，以上实施例的说明只是用于帮助理解本发明的方法及其核心思想；同时，对于本领域的一般技术人员，依据本发明的思想，在具体实施方式及应用范围上均会有改变之处，综上所述，本说明书内容不应理解为对本发明的限制。In the present invention, specific examples have been applied to explain the principles and implementation methods of the present invention, and the descriptions of the above examples are only used to help understand the method of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to this The idea of the invention will have changes in the specific implementation and scope of application. To sum up, the contents of this specification should not be construed as limiting the present invention.

本领域的普通技术人员将会意识到，这里所述的实施例是为了帮助读者理解本发明的原理，应被理解为本发明的保护范围并不局限于这样的特别陈述和实施例。本领域的普通技术人员可以根据本发明公开的这些技术启示做出各种不脱离本发明实质的其它各种具体变形和组合，这些变形和组合仍然在本发明的保护范围内。Those skilled in the art will appreciate that the embodiments described here are to help readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical revelations disclosed in the present invention without departing from the essence of the present invention, and these modifications and combinations are still within the protection scope of the present invention.

Claims (8)

1. The three-dimensional scanning measurement method for the apparent laser line of the underwater concrete is characterized by comprising the following steps of
S1, performing laser line plane calibration on laser line scanning imaging equipment in a clear water replacement device, and constructing a laser plane equation;
s2, establishing a ray tracing model of rays on the surfaces of different media, and further establishing a multi-medium refraction model between a real image point and a camera imaging point;
s3, fusing the multi-medium refraction model with the camera imaging model to obtain a normalization model of underwater imaging;
s4, converting the obtained apparent laser line image of the underwater concrete into a laser line image in corresponding air by using a normalization model and a laser plane equation, and realizing three-dimensional scanning measurement of the apparent laser line of the underwater concrete.
2. The method for three-dimensional scanning measurement of the apparent laser line of the underwater concrete according to claim 1, wherein the step S1 is specifically:
s11, sealing the laser line scanning imaging equipment in a clear water replacement device;
the clear water replacement device is a sealing structure formed by glass blocks containing clear water and is used for placing laser scanning imaging equipment, and clear imaging of a measured object is obtained by replacing turbid water between a camera and the measured object in the laser scanning imaging equipment with clear water in the clear water replacement device when the water quality turbidity of a water area affects the imaging of the laser scanning imaging equipment;
s12, calibrating camera parameters by scanning acquired images by using laser line scanning imaging equipment;
s13, calibrating the laser plane equation by using a camera based on parameter calibration and utilizing cross ratio invariance to construct the laser plane equation.
3. The method according to claim 2, wherein in step S11, the laser line in the laser line scanning imaging device is imaged at the center of the field of view at the camera view.
4. The method according to claim 2, wherein in the step S13, the expression of the cross-ratio invariance is:
Figure QLYQS_1
in the formula ,
Figure QLYQS_2
as a cross-ratio function +.>
Figure QLYQS_3
For points in world coordinate system +.>
Figure QLYQS_4
Is thatQCorresponding to a point in the image coordinate system, subscriptiA sequence number of a point; wherein,Qcharacteristic points to be determined in order to perform laser line plane calibration;
in the step S13, the method for calibrating the laser plane equation includes:
determination of the intersection line of a laser line with the corner point of a calibration plateQCoordinates of points in an image coordinate system, determined using cross-ratio invarianceQCoordinates of the point in the world coordinate system are further used for determining three different angles by utilizing intersection lines of three different angle calibration plates and laser linesQThe points are further obtained to obtain a calibrated laser line plane equation;
Figure QLYQS_5
in the formula ,A,B,C,Dare all undetermined coefficients in the laser plane equation,x,y,zis an arbitrary three-dimensional point of the plane.
5. The method according to claim 1, wherein the expression of the ray tracing model in the step S2 is:
Figure QLYQS_6
Figure QLYQS_7
in the formula ,
Figure QLYQS_9
for the position of the imaged image point +.>
Figure QLYQS_15
Is the thickness of the organic glass->
Figure QLYQS_19
For imaging the object to be positioned in the water, the included angle between the light and the interface after the first refraction is +.>
Figure QLYQS_10
Is the included angle between the camera and the organic glass, < >>
Figure QLYQS_14
For the focal length of the camera +.>
Figure QLYQS_18
Is refraction angle in water>
Figure QLYQS_22
For imaging the world coordinates of the target point, +.>
Figure QLYQS_8
For imaging the distance of the target point from the camera, +.>
Figure QLYQS_12
For imaging the included angle between the incident light of the target point and the boundary normal, +.>
Figure QLYQS_16
Refractive index in water, +.>
Figure QLYQS_20
Refractive index of organic glass +.>
Figure QLYQS_11
Refractive index in air, +.>
Figure QLYQS_13
For the true position of the image point +.>
Figure QLYQS_17
For the imaging target point to be located in the air, the included angle between the light after first refraction and the boundary normal is +.>
Figure QLYQS_21
Is the included angle between the light ray and the normal line of the refracting surface after the second refraction when the object is positioned in the air.
6. The method for three-dimensional scanning measurement of apparent laser lines of underwater concrete according to claim 5, wherein the expression of the multi-medium refraction model in the step S2 is:
Figure QLYQS_23
。
7. the method for three-dimensional scanning measurement of an apparent laser line for underwater concrete according to claim 6, wherein in the step S3, the expression of the normalized model is:
Figure QLYQS_24
in the formula ,
Figure QLYQS_38
is->
Figure QLYQS_26
，/>
Figure QLYQS_35
Is the value of the Z axis under the camera coordinate system corresponding to the pixel point, < >>
Figure QLYQS_33
For pixel coordinate abscissa, +.>
Figure QLYQS_39
For the camera center point abscissa, +.>
Figure QLYQS_37
Is pixel coordinate ordinate, +.>
Figure QLYQS_40
Is the ordinate of the center point of the camera,/>
Figure QLYQS_27
To describe the length of the focal length in the x-axis direction using pixels, +.>
Figure QLYQS_32
To describe the length of the focal length in the y-axis direction using pixels, +.>
Figure QLYQS_25
For a rotation matrix of 3x3,Ga translation matrix of 1x3, +.>
Figure QLYQS_31
For the value of the world coordinate X-axis, +.>
Figure QLYQS_29
For the value of the world coordinate Y-axis, +.>
Figure QLYQS_34
Values for the world coordinate Z-axis; wherein (1)>
Figure QLYQS_30
，/>
Figure QLYQS_36
Refractive index of air>
Figure QLYQS_28
Is the refractive index of water;
Figure QLYQS_41
，/>
Figure QLYQS_42
is glass refractive index;
Figure QLYQS_43
，/>
Figure QLYQS_44
for imaging the target point +.>
Figure QLYQS_45
A value;
Figure QLYQS_46
，/>
Figure QLYQS_47
，/>
Figure QLYQS_48
，Tfor glass thickness->
Figure QLYQS_49
、/>
Figure QLYQS_50
Respectively the refractive angle edges of the light paths in the glassx,yAngle of axial direction, ++>
Figure QLYQS_51
、/>
Figure QLYQS_52
Respectively under the image coordinate systemx,yThe corresponding value is used to determine the value of the corresponding,dis the distance from the camera optical center to the glass.
8. The method for three-dimensional scanning measurement of the apparent laser line of the underwater concrete according to claim 7, wherein the step S4 is specifically:
s41, acquiring an apparent laser line image of the underwater concrete by using a camera with the completed parameter calibration;
s42, converting pixel coordinates in the laser line image by using the normalization model to obtain a laser line image with distorted pixel coordinates eliminated;
s43, sequentially performing closed operation and skeleton extraction on the laser line image of the pixel coordinates without distortion to obtain a non-defect laser line image;
s44, extracting laser lines from the non-defect laser line image by using a gray level gravity center method;
s45, bringing the coordinates of the pixel points in the extracted laser line into a laser plane equation to obtain the three-dimensional coordinates of single-column pixel lasers;
and S46, splicing the three-dimensional coordinates of the continuous multi-frame laser lines to obtain the three-dimensional point cloud coordinates of the underwater concrete in the target area, and realizing three-dimensional scanning measurement.
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