A binocular line structured light scanning system

Abstract

The present application provides a binocular line structured light scanning system, including a binocular line structured light system, a stepper motor displacement platform, a computer and a display; the binocular line structured light system is used to project line structured light on the surface of the object to be measured, and to collect the light stripe image of the object to be measured; the stepper motor displacement platform is used to accurately translate the object to be measured; the computer is used to output control signals for the binocular line structured light system and the stepper motor displacement platform, and to process the collected light stripe image of the object to be measured to obtain a reconstructed image of the object to be measured; the display is used to display the light stripe image and the reconstructed image of the object to be measured. The system has a simple structure and is easy to calibrate, which is beneficial to reducing the error of the three-dimensional reconstructed image. In addition, it can also obtain the color information of the surface of the object to be measured, which is easy to observe.

Description

Technical Field

[0001] The present application belongs to the field of three-dimensional reconstruction technology, and in particular, relates to a binocular line structured light scanning system. Background Art

[0002] Three-dimensional detection technology is the technology of obtaining the three-dimensional spatial coordinates of each point on the surface of an object using various measurement methods. The measurement methods can be mainly divided into two categories: contact and non-contact. The contact measurement method is mainly the traditional mechanical measurement method, such as a three-coordinate measuring machine. This measuring machine uses a probe to contact the surface of the object to be measured, and obtains the three-dimensional information of the object by moving three probes on the surface of the object. This method is not suitable for measuring large objects due to its slow measurement speed, and it is easy to be damaged when measuring hard surfaces. On this basis, a new type of force-displacement sensor was developed to solve the problem of not being able to slide finely on the measurement surface. This measurement method can achieve micron-level accuracy, but there are still many problems such as cumbersome measurement process, inability to measure soft materials and high cost, which prevents it from being widely used.

[0003] In comparison, non-contact measurement methods have developed rapidly with the continuous improvement of optical technology, image processing technology, and sensor technology. Optical detection technology is a detection method that obtains optical information on the surface of an object through electronic equipment and uses image processing technology to reproduce the three-dimensional shape of the object. It mainly includes: shape restoration method, time of flight method, laser radar imaging method, laser triangulation method, structured light scanning method, and moiré fringe method. Among them, the structured light scanning method relies on active light sources and image acquisition equipment to project structured light of different shapes onto the object. The three-dimensional information of the object surface can be obtained by collecting the surface optical information through the camera and processing it, thereby realizing multi-parameter measurement of the object.

[0004] At present, when using a monocular line structured light scanning system to scan objects with mutually occluded or uneven curvature on the measurement surface, blind spots will be generated, resulting in varying degrees of information loss. When using a line structured light scanning system based on a rotating platform for scanning, although it can effectively collect all information on the surface of the object, it requires high accuracy in platform sliding and rotation, and requires the translation and rotation transformations to be unified into the same coordinate system. The calibration process is complicated, and if there are errors in multiple transformations, it will lead to large cumulative errors when solving three-dimensional data. Summary of the invention

[0005] In view of this, the purpose of the present application is to provide a binocular line structured light scanning system, which has a simple structure and is easy to calibrate, which is beneficial to reducing the error of three-dimensional reconstructed images. In addition, it can also obtain the color information of the surface of the object being measured, which is easy to observe.

[0006] The present application provides a binocular line structured light scanning system, including a binocular line structured light system, a stepper motor displacement platform, a computer and a display;

[0007] The binocular line structured light system is used to project line structured light on the surface of the object to be measured, and to collect a light stripe image of the object to be measured;

[0008] The stepper motor displacement platform is used to perform precise translation control on the object to be measured;

[0009] The computer is used to output control signals for the binocular line structured light system and the stepper motor displacement platform, and to process the collected light stripe image of the object to be measured to obtain a reconstructed image of the object to be measured;

[0010] The display is used to display the light bar image and the reconstructed image of the object under test.

[0011] Furthermore, the binocular line structured light system comprises: a line structured light projector, two cameras and a fixing device;

[0012] The line structured light projector is used to project line structured light on the surface of the object to be measured;

[0013] The two cameras are used to receive the first control signal output by the computer to synchronously capture the light stripe images of the object to be measured from different viewing angles;

[0014] The fixing device is used to fix the two cameras at specific positions on both sides of the line structured light projector respectively.

[0015] Furthermore, the line structured light projector and the two cameras have the following postures:

[0016] Establishing a world coordinate system on the structured light plane vertically projected by the line structured light projector, so that the OX axis of the world coordinate system coincides with the structured light plane and the OY axis is perpendicular to the structured light plane;

[0017] Coordinate systems are constructed for the two cameras respectively, and the OZ axes of the two camera coordinate systems point to the center of the structured light plane. The connecting line of the optical centers of the two cameras is parallel to the structured light plane. The main optical axes of the two cameras are coplanar and intersect with the structured light plane.

[0018] Furthermore, the stepper motor displacement platform includes: a stepper motor controller, a stepper motor, a guide rail slide and a base;

[0019] The stepper motor controller is used to receive the second control signal output by the computer and transmit the second control signal to the stepper motor;

[0020] The stepper motor is used for controlling the base on which the object to be measured is fixed to translate on the guide rail slide according to the second control signal.

[0021] Further, the computer includes a video acquisition module;

[0022] The video acquisition module is used to output a first control signal that enables two cameras to synchronously acquire the light stripe image on the surface of the object to be measured;

[0023] The video acquisition module is also used to perform visualization processing on the acquired light stripe image on the surface of the measured object so as to display it through the display.

[0024] Furthermore, the computer also includes a stepper motor control module;

[0025] The stepper motor control module is used to output the second control signal including translation parameters, so that the object under test is translated with a fixed step length; wherein the translation parameters include: moving step length and rotation direction.

[0026] Furthermore, the computer also includes a camera calibration module;

[0027] The camera calibration module is used to obtain the internal and external parameters of the binocular structured light system through images of the calibration plate in different postures captured by two cameras;

[0028] The internal and external parameters of the binocular structured light system are used to generate a conversion matrix from two-dimensional coordinates to three-dimensional coordinates.

[0029] Furthermore, the computer also includes a color image processing module;

[0030] The color image processing module is used to perform light stripe extraction and color recognition on the collected light stripe image on the surface of the measured object, and to convert the two-dimensional coordinates of the light stripe image into three-dimensional coordinates in the world coordinate system through a conversion matrix.

[0031] Furthermore, the computer also includes a point cloud data processing module;

[0032] The point cloud data processing module is used to sequentially perform point cloud denoising, sparseness and splicing processing on the converted three-dimensional coordinates in the world coordinate system to obtain a reconstructed image of the measured object;

[0033] The point cloud data processing module is also used to perform visualization processing on the obtained reconstructed image of the measured object so as to display it through the display.

[0034] The binocular line structured light scanning system provided in the present application has a simple structure and is easy to calibrate, which is beneficial for reducing the error of three-dimensional reconstructed images. In addition, it can also obtain the color information of the surface of the measured object, which is easy to observe. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the line structured light measurement principle provided by an embodiment of the present application is shown;

[0036] Figure 2 A simplified mathematical model schematic diagram of monocular line structured light provided in an embodiment of the present application is shown;

[0037] Figure 3 The invention shows a line structured light scanning system based on a rotating platform provided in an embodiment of the present application;

[0038] Figure 4 A schematic diagram of the structure of a binocular line structured light scanning system provided in an embodiment of the present application is shown;

[0039] Figure 5 Shown is a schematic diagram of a mathematical model of a binocular line structured light system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the technical solution more clear, the technical solution is further described in detail below in conjunction with specific implementation methods. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the technical solution.

[0041] First, the measurement principle of line structured light is introduced:

[0042] Please refer to Figure 1 The schematic diagram of the line structured light measurement principle provided by the embodiment of the present application is shown in FIG. Figure 1 As shown, the light beam emitted by the laser is diffused into a straight line through a special prism, thereby projecting a light plane, which intersects with the surface of the object to be measured to produce a bright light strip, so that the camera line of sight and the light plane intersect at the light strip on the object to be measured. By calibrating the conversion relationship between the camera image plane and the light plane, the spatial position of the point on the image plane corresponding to the point on the laser plane can be determined. At the same time, the offset degree and intermittent gap of the light strip on the surface of the object to be measured can reflect the concave and convex degree and physical gap of the surface of the object to be measured. This method can reduce the scanning time of the surface of the object to be measured, while increasing the amount of information obtained, and does not increase the complexity compared to the point structured light method.

[0043] Secondly, the mathematical model of monocular line structured light is explained:

[0044] The line structured light and the object to be measured need to move relative to each other, and the transformation relationship between the known image coordinate system and the world coordinate system contains 9 rotation parameters and 3 translation parameters. If it is assumed that the posture relationship between the structured light projector and the camera remains unchanged, no matter how the posture of the line structured light plane changes in the world coordinate system, the measurement value in the world coordinate system can be obtained through the rotation and translation matrix between the coordinate systems. Therefore, in order to simplify the measurement model, it is assumed that the line structured light plane is located on the O-yz plane of the world coordinate system, and the relative movement between the object and the structured light is realized with the help of a one-dimensional linear displacement platform.

[0045] Please refer to Figure 2 The mathematical model diagram of the monocular line structured light provided by the embodiment of the present application is shown in FIG. Figure 2 As shown, the plane where the structured light is located is perpendicular to the base, and the measurement coordinate system O is established. W -x w y w z w , world coordinate system O c -x c y c z c , where O W -x w y w The plane is parallel to the linear displacement platform, O W -x w y w The plane coincides with the structured light plane, O W y w The axis is perpendicular to the structured light plane and points to the positive moving direction of the displacement platform. w ,y w ,z w ) is located on the light plane, so y w = 0, further, we can get the two-dimensional coordinates of the stripes P'(u,ν) and P(x w ,0,z w ) is as follows:

[0046]

[0047] During the scanning process, after extracting the two-dimensional coordinates of the stripes in the image, the corresponding three-dimensional coordinates (x w , z w ), and y w It is determined by the compensation of each movement of the displacement platform.

[0048] Next, let's introduce the line structured light scanning system based on the rotating platform:

[0049] When the surfaces of the objects being tested are mutually blocked or the curvature changes unevenly, the use of the above-mentioned monocular line structured light scanning system for detection will lead to the generation of shooting blind spots, which will lead to different degrees of information loss. Therefore, the following is designed: Figure 3 The embodiment of the present application shown in the figure provides a line structured light scanning system based on a rotating platform. Figure 3 As shown in the figure, the system mainly realizes complete and continuous scanning of the surface of the object to be measured by rotating, translating or multi-axis motion of the loading platform. Specifically, the object to be measured is placed on the rotating platform, which drives the object to rotate around the axis. The camera shoots the light strips projected on the surface of the object by line structured light to realize rotational scanning of the object. The system can effectively collect all information on the surface of the object, but it has high requirements on the accuracy of platform sliding and rotation, and it is necessary to transform the translation and rotation and unify them into the same coordinate system. The calibration process is complicated. If there are errors in multiple transformations, it will eventually lead to large cumulative errors when solving three-dimensional data.

[0050] In view of this, the present application embodiment provides a binocular line structured light scanning system. Figure 4 The schematic diagram of the structure of the binocular line structured light scanning system provided by the embodiment of the present application is shown in FIG. Figure 4 As shown, the system includes a binocular line structured light system, a stepper motor displacement platform, a computer and a display;

[0051] The binocular line structured light system is used to project line structured light on the surface of the object to be measured, and to collect the light stripe image of the object to be measured; the stepper motor displacement platform is used to perform precise translation control on the object to be measured; the computer is used to output control signals for the binocular line structured light system and the stepper motor displacement platform, and to process the collected light stripe image of the object to be measured to obtain a reconstructed image of the object to be measured; the display is used to display the light stripe image and the reconstructed image of the object to be measured.

[0052] Furthermore, the binocular line structured light system includes: a line structured light projector, two cameras and a fixing device; the line structured light projector is used to project line structured light on the surface of the object to be measured; the two cameras are used to receive the first control signal output by the computer to synchronously capture the light stripe image of the object to be measured from different perspectives; the fixing device is used to fix the two cameras at specific positions on both sides of the line structured light projector.

[0053] Furthermore, the line structured light projector and the two cameras have the following postures:

[0054] A world coordinate system is established on the structured light plane vertically projected by the line structured light projector, so that the OX axis of the world coordinate system coincides with the structured light plane, and the OY axis is perpendicular to the structured light plane; coordinate systems are constructed for the two cameras respectively, and the OZ axes of the two camera coordinate systems point to the center position of the structured light plane, the connecting line of the optical centers of the two cameras is parallel to the structured light plane, and the main optical axes of the two cameras are coplanar and intersect with the structured light plane.

[0055] As an example, see Figure 5 The mathematical model diagram of the binocular line structured light system provided by the embodiment of the present application is shown in FIG. Figure 5 As shown, the world coordinate system O is established respectively. W -x w y w z w 、Camera 1 coordinate system O c1 -x c1 y c1 z c1 、Camera 2 coordinate system O c2 -x c2 y c2 z c2 , where the two-dimensional coordinates of the light stripe image captured by camera 1 follow the image plane 1 coordinate system O1-u1v1, and the two-dimensional coordinates of the light stripe image captured by camera 2 follow the image plane 2 coordinate system O2-u2v2, that is, the two-dimensional coordinates of the captured light stripe images are (u1, v1) and (u2, v2) respectively.

[0056] Furthermore, the stepper motor displacement platform includes: a stepper motor controller, a stepper motor, a guide rail slide and a base; the stepper motor controller is used to receive a second control signal output by the computer and transmit the second control signal to the stepper motor; the stepper motor is used to control the base to which the object to be measured is fixed to translate on the guide rail slide according to the second control signal.

[0057] Further, the computer includes a video acquisition module;

[0058] The video acquisition module is used to output a first control signal that enables two cameras to synchronously acquire the light stripe image on the surface of the object to be measured; the video acquisition module is also used to visualize the acquired light stripe image on the surface of the object to be measured so as to display it through the display.

[0059] Furthermore, the computer also includes a stepper motor control module;

[0060] The stepper motor control module is used to output the second control signal including translation parameters, so that the object under test is translated with a fixed step length; wherein the translation parameters include: moving step length and rotation direction.

[0061] Furthermore, the computer also includes a camera calibration module;

[0062] The camera calibration module is used to obtain the internal and external parameters of the binocular structured light system through images of the calibration plate in different postures captured by two cameras; wherein the internal and external parameters of the binocular structured light system are used to generate a conversion matrix from two-dimensional coordinates to three-dimensional coordinates.

[0063] Furthermore, the computer also includes a color image processing module;

[0064] The color image processing module is used to perform light stripe extraction and color recognition on the collected light stripe image on the surface of the measured object, and to convert the two-dimensional coordinates of the light stripe image into three-dimensional coordinates in the world coordinate system through a conversion matrix.

[0065] Furthermore, the computer also includes a point cloud data processing module;

[0066] The point cloud data processing module is used to perform point cloud denoising, sparseness and splicing processing on the three-dimensional coordinates in the converted world coordinate system in sequence to obtain a reconstructed image of the object under test; the point cloud data processing module is also used to perform visualization processing on the obtained reconstructed image of the object under test so as to display it through the display.

[0067] The above contents are only preferred embodiments of the present invention. For ordinary technicians in this field, many changes can be made in the specific implementation methods and application scopes based on the ideas of the present technical content. As long as these changes do not deviate from the concept of the present invention, they all fall within the scope of protection of this patent.

Claims

1. A binocular line structured light scanning system, characterized in that: The scanning system includes a binocular line structured light system, a stepper motor displacement platform, a computer and a display; The binocular line structured light system is used to project line structured light on the surface of the object to be measured, and to collect a light stripe image of the object to be measured; The stepper motor displacement platform is used to perform precise translation control on the object to be measured; The computer is used to output control signals for the binocular line structured light system and the stepper motor displacement platform, and to process the collected light stripe image of the object to be measured to obtain a reconstructed image of the object to be measured; The display is used to display the light bar image and the reconstructed image of the object under test.

2. The binocular line structured light scanning system according to claim 1, characterized in that: The binocular line structured light system comprises: a line structured light projector, two cameras and a fixing device; The line structured light projector is used to project line structured light on the surface of the object to be measured; The two cameras are used to receive the first control signal output by the computer to synchronously capture the light stripe images of the object to be measured from different viewing angles; The fixing device is used to fix the two cameras at specific positions on both sides of the line structured light projector respectively.

3. The binocular line structured light scanning system according to claim 2, characterized in that: The line structured light projector and the two cameras have the following positions: Establishing a world coordinate system on the structured light plane vertically projected by the line structured light projector, so that the OX axis of the world coordinate system coincides with the structured light plane and the OY axis is perpendicular to the structured light plane; Coordinate systems are constructed for the two cameras respectively, and the OZ axes of the two camera coordinate systems point to the center of the structured light plane. The connecting line of the optical centers of the two cameras is parallel to the structured light plane. The main optical axes of the two cameras are coplanar and intersect with the structured light plane.

4. The binocular line structured light scanning system according to claim 1, characterized in that: The stepper motor displacement platform comprises: a stepper motor controller, a stepper motor, a guide rail slide and a base; The stepper motor controller is used to receive the second control signal output by the computer and transmit the second control signal to the stepper motor; The stepper motor is used for controlling the base on which the object to be measured is fixed to translate on the guide rail slide according to the second control signal.

5. The binocular line structured light scanning system according to claim 3, characterized in that: The computer includes a video acquisition module; The video acquisition module is used to output a first control signal that enables two cameras to synchronously acquire the light stripe image on the surface of the object to be measured; The video acquisition module is also used to perform visualization processing on the acquired light stripe image on the surface of the measured object so as to display it through the display.

6. The binocular line structured light scanning system according to claim 4, characterized in that: The computer also includes a stepper motor control module; The stepper motor control module is used to output the second control signal including translation parameters, so that the object under test is translated with a fixed step length; wherein the translation parameters include: moving step length and rotation direction.

7. The binocular line structured light scanning system according to claim 5, characterized in that: The computer also includes a camera calibration module; The camera calibration module is used to obtain the internal and external parameters of the binocular structured light system through images of the calibration plate in different postures captured by two cameras; The internal and external parameters of the binocular structured light system are used to generate a conversion matrix from two-dimensional coordinates to three-dimensional coordinates.

8. The binocular line structured light scanning system according to claim 7, characterized in that: The computer also includes a color image processing module; The color image processing module is used to perform light stripe extraction and color recognition on the collected light stripe image on the surface of the measured object, and to convert the two-dimensional coordinates of the light stripe image into three-dimensional coordinates in the world coordinate system through a conversion matrix.

9. The binocular line structured light scanning system according to claim 1, characterized in that: The computer also includes a point cloud data processing module; The point cloud data processing module is used to perform point cloud denoising, sparseness and splicing processing on the converted three-dimensional coordinates in the world coordinate system in sequence to obtain a reconstructed image of the measured object; The point cloud data processing module is also used to perform visualization processing on the obtained reconstructed image of the measured object so as to display it through the display.

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