CN114322840B - 3D scanning system calibration method, device and data processing method - Google Patents
3D scanning system calibration method, device and data processing method Download PDFInfo
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Abstract
The invention relates to a 3D scanning system calibration method, a device and a data processing method, which comprise the following steps: s1, setting a calibration object, wherein the transverse section of the calibration object is annular and parallel to the surface of a fixed platform of the object to be measured; s2, enabling the calibration object and the scanning device to rotate relatively, and acquiring a plurality of profile scanning data in the rotating process; s3, acquiring the center of a circular ring of the calibration object based on the laser line emission direction and the contour scanning data of the scanning system; s4, coordinate conversion is carried out on the centers of all the circular rings to enable the centers to coincide, and a scanning line corresponding to the rotation position and a first intersection point of two adjacent scanning lines are obtained based on the coordinate conversion and the contour scanning data; s5, fitting the first intersection point to obtain a rotation center of the scanning system, and obtaining an included angle between the scanning line and a reference scanning line as a rotation angle of the scanning system; and S6, establishing a corresponding relation among the rotation center, the rotation angle and the rotation process to obtain calibration parameters of the scanning system. By the method and the device, the 3D imaging precision of the round object can be improved.
Description
Technical Field
The present invention relates to the field of 3D scanning technologies, and in particular, to a 3D scanning system calibration method, apparatus, and data processing method.
Background
The 3D line laser scanning profiler is commonly used for high-precision reconstruction of the profile surface of an industrial product, so that the shape information and the size information of the product are obtained, and quick, stable and nondestructive non-contact measurement is realized. Along with the intelligent development of the industrial manufacturing field, the application scene of the high-precision detection mode is wider and wider. The 3D line laser scanning profiler mainly comprises a laser and a photosensitive component, the laser projects laser to the surface of the measured object, the laser enters a lens to image on the photosensitive component through diffuse reflection, the imaging position changes along with the change of the distance of a target, and the relative height of the measured object can be obtained by resolving the imaging relative position. In one acquisition, only one profile section of the object surface can be obtained, and for measuring the whole object, the 3D profiler and the object need to have relative translational motion or rotational motion so as to combine and reconstruct the 3D data of the object, as shown in fig. 5, the Y-direction distance between the two profile lines is usually ensured by a motion mechanism.
For measuring and detecting a circular object, such as a watch, a ring, a wheel or a tire, relative rotation is required between the detected object and the profiler so that different parts can obtain optimal imaging effects, and therefore the influence of shape changes of all parts of the object on imaging quality is avoided. As shown in fig. 6, the 3D data of the object needs to be reconstructed by using the angle information of the rotation motion, and the contour line obtained by the contour instrument is mapped to the corresponding position on the object, so that the accurate 3D data can be obtained.
However, in a practical scenario, the speed of the rotational movement may not be uniform (especially during acceleration and deceleration phases). The angle of motion is known from the encoder count of the motion mechanism, but if the encoder count read from the motion mechanism is used directly, the angle of motion data between adjacent section profile data will be inaccurate. Second, the center of rotation of the motion is unknown in the coordinates of the 3D profiler coordinate system, so the reconstruction using only the motion angle between adjacent acquisitions is not accurate.
Disclosure of Invention
The invention aims to solve the technical problems of the prior art and provides a 3D scanning system calibration method, a device and a data processing method.
The technical scheme adopted for solving the technical problems is as follows: a 3D scanning system calibration method is constructed, comprising the steps of:
s1, setting a calibration object on a tested object fixing platform of a scanning system, wherein the transverse section of the calibration object is annular and parallel to the surface of the tested object fixing platform;
s2, enabling the calibration object and the scanning device of the scanning system to relatively rotate according to a preset rule through the moving device of the scanning system, and acquiring a plurality of profile scanning data of the longitudinal section of the calibration object, which correspond to the rotating position, in the rotating process;
s3, acquiring the center of the circular ring of the calibration object, which corresponds to the rotating position, based on the laser line emitting direction of the scanning system and the contour scanning data;
s4, coordinate conversion is carried out on the centers of all the circular rings to enable the centers to coincide, scanning lines corresponding to the rotation positions are obtained based on the coordinate conversion and the contour scanning data, and first intersection points of two adjacent scanning lines are obtained to obtain a plurality of first intersection points;
s5, fitting the first intersection points to obtain the centers of all the first intersection points as the rotation centers of the scanning system, and obtaining the included angle between the scanning line and a reference scanning line as the rotation angle of the scanning system;
and S6, establishing a corresponding relation among the rotation center, the rotation angle and the rotation process to obtain calibration parameters of the scanning system.
In the 3D scanning system calibration method of the present invention, in the step S3, the circle center of the calibration object corresponding to the rotation position is obtained based on the laser line emission direction of the scanning system and the profile scanning data; comprising the following steps:
s31, the contour scanning data comprise gray data corresponding to the longitudinal section of the calibration object, and a plurality of second intersection points of the working laser line emitting direction and the concentric ring of the calibration object are obtained based on the gray data;
s32, respectively taking the radiuses of the concentric rings of the calibration objects corresponding to the second intersection points as circle centers to obtain a plurality of circumferences parallel to the surface of the object to be measured, wherein the radiuses of the calibration objects comprise the inner diameter and the outer diameter of the calibration objects;
s33, obtaining third intersection points of the circumferences to serve as the center of the circular ring, corresponding to the rotation position, of the calibration object.
Preferably, the 3D scanning system calibration method of the present invention further includes:
s01, estimating the ring center of the calibration object to obtain an estimated ring center of the calibration object, and estimating the rotation center of the tested object fixing platform relative to the scanning device to obtain an estimated rotation center, so that the estimated ring center of the calibration object deviates from the estimated rotation center when the calibration object is fixed on the tested object fixing platform.
Preferably, in the 3D scanning system calibration method of the present invention, S02, adjusting the position of the calibration object multiple times to fix the calibration object on the measured object fixing platform of the scanning system again, and executing the steps S2 to S5 based on the adjusted calibration object, so as to obtain multiple sets of rotation center positions correspondingly;
or (b)
In the step S1, setting the calibration object on the object fixing platform of the scanning system includes setting a plurality of calibration objects at different positions of the object fixing platform;
the method further comprises the steps of: executing the step S2 to the step S5 based on each calibration object so as to correspondingly acquire a plurality of groups of rotation center positions;
s03, fitting the multiple groups of rotation center positions, obtaining a final rotation center position according to a fitting result, and executing the step S6;
preferably, in the 3D scanning system calibration method of the present invention, in the step S03, the fitting the plurality of sets of rotation center positions and obtaining a final rotation center position according to a fitting result includes:
and acquiring center points corresponding to the multiple groups of rotation center positions to serve as final rotation center positions.
Preferably, in the 3D scanning system calibration method of the present invention, in the step S32, the third intersection points of the several circumferences are obtained as a center of a circle of the calibration object, the center corresponding to the rotation position; comprising the following steps:
fitting the third intersection points of the circles to obtain center points of the third intersection points, wherein the center points of the third intersection points are used as the centers of the circular rings of the calibration object, which correspond to the rotating positions.
Preferably, in the step S5, fitting the first intersection points to obtain centers of all the first intersection points as rotation centers of the scanning system includes:
and performing circle fitting on the first intersection point, wherein the center of the fitted circle is taken as the center of the first intersection point.
Preferably, in the 3D scanning system calibration method of the present invention, the transverse cross-sectional area of the calibration object is greater than half of the planar area of the object fixing platform.
In addition, the invention also constructs a data processing method of the 3D scanning system, which comprises the following steps:
setting a measured object on a measured object fixing platform, and enabling the measured object and a scanning device of the scanning system to relatively rotate according to a preset rule through a moving device of the scanning system so as to acquire initial point cloud data of the measured object;
performing point cloud reconstruction on the point cloud data through calibration parameters acquired by the 3D scanning system calibration method according to any one of the above; wherein the calibration parameters include a matrix:
wherein (cx, cy, cz) is the rotational center position, θ n-1 The angle between the nth acquisition line and the first acquisition line is (a, b, c) the original coordinates corresponding to the nth acquisition line, and (x, y, z) the transformed coordinates corresponding to the nth acquisition line.
The invention also constructs a 3D scanning system calibration device, comprising: the calibration object is arranged on a measured object fixing platform of the scanning system; the processor may be configured to receive a signal from a host computer,
the transverse section of the calibration object is annular and is parallel to the surface of the object to be measured fixing platform;
the processor is configured to perform a 3D scanning system calibration method as claimed in any one of the preceding claims.
The 3D scanning system calibration method, the device and the data processing method have the following beneficial effects: the 3D imaging accuracy of the circular object can be improved.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a flowchart illustrating a 3D scan calibration method according to an embodiment of the present invention;
FIG. 2 is a program flow diagram of another embodiment of the 3D scan calibration method of the present invention;
FIG. 3 is a schematic diagram of a process for acquiring the center of a circle of a calibration object in the 3D scanning calibration method of the present invention;
FIG. 4 is a schematic diagram of an optional center acquisition process in the 3D scan calibration method of the present invention;
FIG. 5 is a schematic diagram of a generic object 3D scanning process;
fig. 6 is a schematic diagram of a 3D scanning process of a circular object.
Detailed Description
For a clearer understanding of technical features, objects and effects of the present invention, a detailed description of embodiments of the present invention will be made with reference to the accompanying drawings.
As shown in fig. 1, in a first embodiment of a 3D scanning system calibration method of the present invention, the method includes the following steps:
s1, setting a calibration object on a tested object fixing platform of a scanning system, wherein the transverse section of the calibration object is annular and parallel to the surface of the tested object fixing platform; specifically, a calibration object with a transverse section in a ring shape is arranged on a tested platform. The position of the fixed calibration object is the same as the position of the fixed object to be measured, and the transverse section of the fixed calibration object is parallel to the fixed platform of the object to be measured. When the laser scans, the laser scans the annular section. In the setting process, the positions of the 3D profiler and the rotary motion platform can be adjusted, so that the XY plane of the 3D profiler is parallel to the surface of the platform as much as possible. When the three-dimensional profile meter cannot be completely parallel, the inclined angle can be further corrected through a built-in algorithm of the three-dimensional profile meter, so that the imaging of the platform surface on the three-dimensional profile meter is ensured to be positioned at the same height distance. That is, if there is a tilt between the plane of the motion stage and the XY plane of the 3D profiler, a line can be fitted in the coordinate system of the 3D profiler using the 3D data points on the rotational stage output by the profiler. The direction of the line represents the angle of inclination and can be used to construct a representation of the rotation plane in the 3D profiler coordinate system, so that the calibration step can be performed on this rotation plane instead of on the XY plane of the 3D profiler.
S2, enabling the calibration object and the scanning device of the scanning system to relatively rotate according to a preset rule through the moving device of the scanning system, and acquiring a plurality of profile scanning data of the longitudinal section of the calibration object, which correspond to the rotating position, in the rotating process; specifically, the moving device of the scanning system rotates to enable the object to be measured fixing platform to move relatively to the scanning device of the scanning system, and in the moving process, the scanning system starts to scan the longitudinal section of the calibration object. The preset rules may include setting the direction or speed of rotation of the rotating platform. It can be understood that in the process that the calibration object rotates along with the rotating platform, the scanning device can scan the calibration object every time the calibration object rotates to a position so as to obtain the profile scanning data of the longitudinal section of the calibration object corresponding to the rotating position. The rotating process of the rotating platform can be controlled through the encoder information of the rotating device, the encoder information is updated once, the corresponding rotating device rotates one step, and corresponding profile scanning data are correspondingly obtained. After the calibration object and the scanning device relatively rotate for one circle, the scanning device can obtain a plurality of profile scanning data of the longitudinal section of the scanning device relative to each rotation position of the calibration object in the process of rotating for one circle. The rotation may be one or more or less than one revolution, for example, only a partial region of the ring is scanned, and finally a plurality of data are processed.
S3, acquiring the center of the circular ring of the calibration object, which corresponds to the rotating position, based on the laser line emitting direction and the contour scanning data of the scanning system; specifically, in the rotation process of the rotary platform, profile scanning data can be obtained at each rotary position, and the intersection point of each profile scanning data and the laser line can be obtained respectively. Since the radius of the calibration object is known, and the intersection point is also a point on the circumference of the calibration object, the coordinates corresponding to the center of the ring of the calibration object can be obtained based on the currently obtained profile scanning data according to the known radius and the intersection point.
S4, coordinate conversion is carried out on the centers of all the circular rings to enable the centers to coincide, scanning lines corresponding to the rotation positions are obtained based on the coordinate conversion and the contour scanning data, and first intersection points of two adjacent scanning lines are obtained to obtain a plurality of first intersection points; specifically, when contour scanning data are obtained through each scanning, the center of the ring corresponding to the calibration object is obtained, and finally, when the calibration object rotates for one circle, the centers of the rings of the calibration object at all positions can be obtained. Because the circle center of the calibration object is actually one, the positions of the circle centers are unified, for example, coordinate conversion is performed, all the circle centers are converted to a fixed point, at the moment, the contour scanning data corresponding to the circle centers are also subjected to the same coordinate conversion, converted scanning lines are obtained, and therefore the relative position relation among the scanning lines can be obtained. In an embodiment, the fixed point may be selected as any one of the ring centers, or may be another point, and generally, the ring center corresponding to the first contour scan data acquired according to the time relationship may be selected as the fixed point. And acquiring the intersection points of two adjacent scanning lines as first intersection points according to the rotation position relation of the scanning lines obtained after coordinate conversion, so that one first intersection point can be obtained for every two adjacent scanning lines, and a plurality of first intersection points can be obtained for a plurality of scanning lines. In one embodiment, as shown in FIG. 4, for each cross-sectional profile of a marker region, its depth coordinate information, the corresponding marker center coordinate information, and the encoder count value are known. Setting the 1 st section contour line as L1, setting the corresponding calibration center as C1, and setting the encoder count value as E1; the 2 nd section contour line is L2, the corresponding calibration center is C2, the encoder count value is E2, … …, the n th section contour line is Ln, the corresponding calibration center is Cn, and the encoder count value is En. And converting the 2 nd section contour line into a coordinate system where the 1 st section contour line is positioned by taking the 1 st section contour line as a reference. The conversion process is as follows: c1 and C2 correspond to the same point of the physical space, so L2 and C2 are translated first, so that C2 and C1 coincide; the angle between L1 and L2 is determined by the encoder count difference Δe=e2-E1, and so far the relative positional relationship of L1 and L2 has been determined.
S5, fitting the first intersection points to obtain the centers of all the first intersection points as the rotation centers of the scanning system, and obtaining the included angle between the scanning line and a reference scanning line as the rotation angle of the scanning system; specifically, all the obtained first intersection points are fitted to obtain a center point of the first intersection points, and the center point is the rotation center of the scanning system. And meanwhile, the scanning line acquired above is used as a reference scanning line to acquire an angle, namely the rotation angle of the scanning system corresponding to the scanning line can be understood. It can be understood that each time the scanning system rotates, one scanning line is obtained, and the included angle between the scanning line and the reference scanning line is generated by the rotation angle of the scanning system, so that the rotation angle corresponds to the scanning line one by one.
In an embodiment, fitting the first intersection points such that the center of all the first intersection points is the rotation center of the scanning system includes: and performing circle fitting on the first intersection point, wherein the center of the fitted circle is the center of the first intersection point. Specifically, referring to fig. 4, the intersection of L1 and L2 is denoted as I12. Similarly, intersection points I23, I34 and … … can be obtained, after all the intersection points are obtained, circle fitting is carried out, and the circle center obtained by fitting is the coordinate of the rotation center in the 3D profiler coordinate system. Before coordinate conversion, the positions of all the cross-sectional contour lines are actually coincident, that is, the positions of laser scanning, and in the drawing, the cross-sectional contour lines are scan lines obtained by overlapping the center positions of the calibration objects for coordinate conversion.
And S6, establishing a corresponding relation among the rotation center, the rotation angle and the rotation process to obtain calibration parameters of the scanning system. Specifically, after the rotation center of the scanning system and the rotation angle in the rotation process are obtained, the calibration parameters of the scanning system in the scanning process can be obtained, and the calibration of the scanning process is performed according to the calibration parameters.
Optionally, as shown in fig. 2, in step S3, based on the laser line emission direction and the profile scanning data of the scanning system, the center of the ring of the calibration object corresponding to the rotation position is obtained; comprising the following steps: s31, the contour scanning data comprise gray data corresponding to the longitudinal section of the calibration object, and a plurality of second intersection points of the working laser line transmitting direction and the concentric ring of the calibration object are obtained based on the gray data; s32, respectively taking the radiuses of the concentric rings of the calibration objects corresponding to the second intersection points as the circle centers to obtain a plurality of circumferences parallel to the surface of the object to be measured, wherein the radiuses of the calibration objects comprise the inner diameter and the outer diameter of the calibration objects; s33, acquiring third intersection points of a plurality of circumferences to serve as the centers of the circular rings of the calibration object, wherein the centers correspond to the rotation positions. Specifically, as shown in fig. 3, when the circular calibration object rotates on the rotary motion platform and performs data acquisition, in each acquisition, the 3D profiler outputs gray data and height point cloud data of a section profile, the gray data and the height data are corresponding to each other, and the calibration of the corresponding relationship is set by the 3D profiler device itself. And storing the gray data, the height point cloud data and the encoder information of the motion platform which are acquired each time. And extracting the intersection point between the laser plane and the concentric ring on the calibration object based on the gray data acquired each time. Because of obvious color difference between the edge of the circular ring and the background, the reflectivity of the circular ring to the incident laser is also obviously different, the reflection is reflected to the 3D profiler, the gray level of the background area corresponding to the highlight is higher, and the gray level of the edge of the circular ring is lower. Therefore, the second intersections A1, A2, A3, which are the intersections between the laser plane and the ring, can be extracted from the gradation value differences of the section profile gradation data. Since the gray scale data and the height point cloud data are corresponding, the coordinates of the second intersection point in the 3D profiler coordinate system are known. And (3) for each image grabbing, calculating the coordinates of the circle center of the circle of the calibration object in the 3D profiler coordinate system. Because the radius of the circular rings on the calibration object is known and the circular rings are concentric, a plurality of circles with the specified circular ring radius can be constructed on a plane parallel to the XY plane of the 3D profiler by taking the second intersection point extracted in the steps as the center, the intersection point of the circles, namely the third intersection point B, is the common circle center of the circular rings, namely the center of the circular rings of the calibration object, and the Z coordinate of the circle center is kept consistent with the Z coordinate of the intersection point. It should be noted that there are two possible positions of the center of the ring, but the user can easily find out which is the correct position by looking at the laser line on the calibration object. Also, because of symmetry, it is not critical which intersection point is chosen as the center point of the circle, and the reconstructed 3D point cloud data is identical.
Optionally, the 3D scanning system calibration method of the present application further includes: s01, estimating the ring center of the calibration object to obtain an estimated ring center of the calibration object, and estimating the rotation center of the fixed platform of the measured object relative to the scanning device to obtain an estimated rotation center, so that the estimated ring center of the calibration object deviates from the estimated rotation center when the calibration object is fixed on the fixed platform of the measured object. Specifically, in order to improve accuracy of acquiring the rotation center, the center of the concentric ring should deviate from the rotation center of the platform, and it is also understood that the center of the calibration object and the center of the rotation platform are prevented from overlapping as much as possible. The method can predict the structures of the calibration object and the measured object fixing platform, so that the center positions of the calibration object and the measured object have larger deviation as much as possible, and the method is very easy to achieve in actual operation.
Optionally, the 3D scanning system calibration method of the present application further includes: s02, adjusting the positions of the calibration objects for multiple times to fix the calibration objects on a tested object fixing platform of the scanning system again, and executing the steps S2 to S5 based on the adjusted calibration objects so as to correspondingly obtain a plurality of groups of rotation center positions; s03, fitting a plurality of groups of rotation center positions, obtaining a final rotation center position according to a fitting result, and executing a step S6; specifically, the calibration object may be placed at different positions on the object fixing platform, the steps S2 to S5 are executed respectively, the scanning and the acquisition of the rotation center are performed, after a plurality of rotation centers are obtained, the fitting is performed on the plurality of rotation center positions to obtain a final rotation center position, and the setting of the calibration parameter is performed according to the final rotation center position.
Optionally, in the 3D scanning system calibration method of the present application: in step S1, setting a calibration object on a measured object fixing platform of a scanning system includes setting different positions of a plurality of calibration objects and the measured object fixing platform; the method further comprises the steps of: executing the steps S2 to S5 based on each calibration object to correspondingly acquire a plurality of groups of rotation center positions; s03, fitting a plurality of groups of rotation center positions, obtaining a final rotation center position according to a fitting result, and executing a step S6; specifically, a plurality of calibration objects can be placed at different positions on the object fixing platform, the steps S2 to S5 are executed for each calibration object respectively, scanning and acquisition of rotation centers are performed, after a plurality of rotation centers are obtained, fitting is performed on the plurality of rotation center positions to obtain a final rotation center position, and setting of calibration parameters is performed according to the final rotation center position.
Optionally, in step S03, fitting a plurality of sets of rotation center positions and obtaining a final rotation center position according to the fitting result includes: and acquiring center points corresponding to the plurality of groups of rotation center positions to serve as final rotation center positions. Specifically, when fitting is performed on the plurality of rotation center positions obtained above, it may perform circumference fitting to obtain a center point of the plurality of rotation center positions, and the center point is used as a final rotation center position.
Optionally, in step S32, a third intersection point of a plurality of circumferences is obtained as a center of the ring of the calibration object corresponding to the rotation position; comprising the following steps: fitting the third intersection points of the circles to obtain center points of the third intersection points, and taking the center points of the third intersection points as the centers of the circles of the calibration objects, which correspond to the rotation positions. Specifically, when obtaining a plurality of circumferences, the third intersection point obtained by the method is not just one point due to measurement deviation, the plurality of intersection points are fitted, and finally the center of the third intersection point is the center of the ring of the calibration object, which corresponds to the rotation position. When fitting the third intersection point, circumference fitting can be adopted to obtain a fitting center, and the fitting center is used as the center of a circular ring of the calibration object, which corresponds to the rotation position.
Optionally, the transverse cross-sectional area of the calibration object is greater than half the planar area of the object-under-test fixing platform. Specifically, when the number of the calibration objects is one, the transverse cross-sectional area of the calibration objects can be set to occupy a larger rotary table surface relative to the plane area of the fixed platform of the measured object.
Alternatively, the calibration object may have 3 concentric rings of known radius, which may be etched rings or printed rings, in various forms, as long as the ring edge has a high contrast with the background color. There is no specific requirement for radius, and there is no mutual interference in imaging between rings.
The invention discloses a data processing method of a 3D scanning system, which comprises the following steps: setting a measured object on a measured object fixing platform, and enabling the measured object and a scanning device of a scanning system to relatively rotate according to a preset rule through a moving device of the scanning system so as to acquire initial point cloud data of the measured object; performing point cloud reconstruction on the point cloud data through the calibration parameters acquired by the 3D scanning system calibration method according to any one of the above; wherein the calibration parameters include a matrix:
wherein, (cx, cy, cz) is the rotation center position, θn-1 is the angle between the nth acquisition line and the first acquisition line, (a, b, c) is the original coordinate corresponding to the nth acquisition line, and (x, y, z) is the transformed coordinate corresponding to the nth acquisition line. Specifically, the 3D profiler may reconstruct 3D point cloud data of the real object using the calibration results. Acquiring the coordinates of the rotation center in a 3D profiler coordinate system as cx, cy and cz, wherein the angle between the second contour line correspondingly acquired at one rotation position and the first contour line at the reference position is theta in the rotation scanning process of the scanning system 1 The angle between the third contour line of the other rotation position and the first contour line of the reference position is theta 2 … … the angle between the nth contour line and the first contour line is θ n-1 . The conversion of the nth contour line into the coordinate system in which the first contour line is located with reference to the first contour line can be accomplished by the above mapping. And finally, obtaining the positions, namely the 3D coordinates, of the contour lines acquired at all the rotation positions relative to the reference positions, and finally obtaining the 3D image reconstruction of the measured object according to the positions. The rotation process of the measured object is consistent with the rotation process of the calibration object, namely the rotation speed is kept consistent.
The invention provides a 3D scanning system calibration device, which comprises: the calibration object is arranged on a measured object fixing platform of the scanning system; the transverse section of the calibration object is annular and is parallel to the surface of the object to be measured fixing platform; the processor is configured to perform the 3D scanning system calibration method as above. Specifically, in the calibration device, the processor controls the scanning system to perform various data processing, and finally calibration parameters of the scanning system are obtained.
It is to be understood that the above examples only represent preferred embodiments of the present invention, which are described in more detail and are not to be construed as limiting the scope of the invention; it should be noted that, for a person skilled in the art, the above technical features can be freely combined, and several variations and modifications can be made without departing from the scope of the invention; therefore, all changes and modifications that come within the meaning and range of equivalency of the claims are to be embraced within their scope.
Claims (10)
1. A method for calibrating a 3D scanning system, comprising the steps of:
s1, setting a calibration object on a tested object fixing platform of a scanning system, wherein the transverse section of the calibration object is annular and parallel to the surface of the tested object fixing platform; if the transverse section is not parallel to the surface of the measured object fixing platform, the positions of the 3D profiler and the rotary motion platform are adjusted so that the XY plane of the 3D profiler is close to be parallel to the surface of the platform, or the inclination angle is corrected through an internal algorithm of the 3D profiler;
s2, enabling the calibration object and the scanning device of the scanning system to relatively rotate according to a preset rule through the moving device of the scanning system, and acquiring a plurality of profile scanning data of the longitudinal section of the calibration object, which correspond to the rotating position, in the rotating process;
s3, a laser in the 3D profiler projects laser to the surface of the measured object, and the center of the circular ring of the calibration object corresponding to the rotating position is obtained based on the laser line emitting direction of the scanning system and the profile scanning data;
s4, coordinate conversion is carried out on the centers of all the circular rings to enable the centers to coincide, scanning lines corresponding to the rotation positions are obtained based on the coordinate conversion and the contour scanning data, and first intersection points of two adjacent scanning lines are obtained to obtain a plurality of first intersection points;
s5, fitting all the first intersection points to obtain the center of the first intersection point as the rotation center of the scanning system, and obtaining the included angle between the scanning line and a reference scanning line as the rotation angle of the scanning system;
and S6, establishing a corresponding relation among the rotation center, the rotation angle and the rotation process to obtain calibration parameters of the scanning system.
2. The method according to claim 1, wherein in the step S3, the circle center of the calibration object corresponding to the rotation position is obtained based on the laser line emission direction of the scanning system and the profile scanning data; comprising the following steps:
s31, the profile scanning data comprise gray data corresponding to the longitudinal section of the calibration object, and a plurality of second intersection points of the laser line emitting direction and the concentric ring of the calibration object are obtained based on the gray data;
s32, respectively taking the radiuses of the concentric rings of the calibration objects corresponding to the second intersection points as circle centers to obtain a plurality of circumferences parallel to the surface of the object to be measured, wherein the radiuses of the calibration objects comprise the inner diameter and the outer diameter of the calibration objects;
s33, obtaining third intersection points of the circumferences to serve as the center of the circular ring, corresponding to the rotation position, of the calibration object.
3. The 3D scanning system calibration method of claim 1, further comprising:
s01, estimating the ring center of the calibration object to obtain an estimated ring center of the calibration object, and estimating the rotation center of the tested object fixing platform relative to the scanning device to obtain an estimated rotation center, so that the estimated ring center of the calibration object deviates from the estimated rotation center when the calibration object is fixed on the tested object fixing platform.
4. The 3D scanning system calibration method of claim 1, further comprising:
s02, adjusting the position of the calibration object for multiple times to fix the calibration object on a tested object fixing platform of the scanning system again, and executing the steps S2 to S5 based on the adjusted calibration object so as to correspondingly obtain multiple groups of rotation center positions;
or (b)
In the step S1, setting the calibration object on the object fixing platform of the scanning system includes setting a plurality of calibration objects at different positions of the object fixing platform;
the method further comprises the steps of: executing the step S2 to the step S5 based on each calibration object so as to correspondingly acquire a plurality of groups of rotation center positions;
and S03, fitting the multiple groups of rotation center positions, obtaining a final rotation center position according to a fitting result, and executing the step S6.
5. The method according to claim 4, wherein in the step S03, the fitting the plurality of sets of rotation center positions and obtaining a final rotation center position according to a fitting result includes:
and acquiring center points corresponding to the multiple groups of rotation center positions to serve as final rotation center positions.
6. The method for calibrating a 3D scanning system according to claim 2, wherein,
in the step S32, the third intersection points of the plurality of circumferences are obtained as a center of a ring of the calibration object, where the center corresponds to the rotation position; comprising the following steps:
fitting the third intersection points of the circles to obtain center points of the third intersection points, wherein the center points of the third intersection points are used as the centers of the circular rings of the calibration object, which correspond to the rotating positions.
7. The 3D scanning system calibration method according to claim 1, wherein in the step S5, fitting all the first intersection points to obtain the center of the first intersection point as the rotation center of the scanning system comprises:
and performing circle fitting on the first intersection point, wherein the center of the fitted circle is the center of the first intersection point.
8. The method of claim 1, wherein the cross-sectional area of the marker is greater than half the planar area of the subject-holding platform.
9. A method for processing data in a 3D scanning system, comprising:
setting a measured object on a measured object fixing platform, and enabling the measured object and a scanning device of the scanning system to relatively rotate according to a preset rule through a moving device of the scanning system so as to acquire initial point cloud data of the measured object;
performing point cloud reconstruction on the point cloud data by using calibration parameters obtained by the 3D scanning system calibration method according to any one of claims 1 to 8; wherein the calibration parameters include a matrix:
wherein (cx, cy, cz) is the rotational center position, θ n-1 The angle between the nth acquisition line and the first acquisition line is (a, b, c) the original coordinates corresponding to the nth acquisition line, and (x, y, z) the transformed coordinates corresponding to the nth acquisition line.
10. A 3D scanning system calibration device, comprising: the calibration object is arranged on a measured object fixing platform of the scanning system; the processor may be configured to receive a signal from a host computer,
the transverse section of the calibration object is annular and is parallel to the surface of the object to be measured fixing platform;
the processor is configured to perform the 3D scanning system calibration method according to any one of claims 1 to 8.
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