CN110827359A - Checkerboard trihedron-based camera and laser external reference checking and correcting method and device - Google Patents
Checkerboard trihedron-based camera and laser external reference checking and correcting method and device Download PDFInfo
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Abstract
The invention discloses a checkerboard trihedron-based camera and laser external reference checking method and device, belongs to the field of mobile measurement, and aims to find a proper posture by continuously shaking the checkerboard trihedron in front of a measuring device. Under the condition, the trihedron is placed in front of the camera and the laser once, and meanwhile, the checkerboard images and the laser point data are obtained, so that the laser checkerboard scanning device is convenient and flexible. Firstly, solving and obtaining the position and the posture of a laser relative to the trihedron by using a three-point perspective method according to three intersecting lines of a laser scanning surface and the trihedron by taking the trihedron as a moving reference control field; then, according to the collinear rule between the checkerboard angular points of the trihedron and the corresponding image points of the trihedron, the position and the posture of the camera in the control field of the trihedron are calculated by utilizing space rear intersection; finally, in combination with the two steps described above, rotation and translation between the camera and the laser is obtained. Compared with the traditional method, the method has the advantages of simplicity in operation, high calibration precision, good robustness and the like.
Description
Technical Field
The invention belongs to the field of mobile measurement, and particularly relates to a checkerboard trihedron-based camera and laser external reference checking method and device.
Background
The combined use of cameras and single line lasers is widely used in many practical fields, such as robotics, mobile surveying and real-time construction of maps. The combination is low in cost, and meanwhile, visual information such as color textures and geometric structure information such as coordinates and distances in a scene can be acquired. However, because the internal structure of the device is different from the factors such as the working mode, the installation position, the reference coordinate system and the like, difficulty is brought to the fusion and alignment of the two data, and the first problem is to perform external reference calibration between the two devices, namely to obtain the rotation and translation relationship between the two different device coordinate systems of the camera and the laser.
Given that the laser is outside the visible spectral range, it is not easy to find the corresponding point in the image that corresponds to the characteristic point laser data. Therefore, partial scholars adopt the infrared camera to acquire visible laser spots to establish the corresponding relation between the image point and the laser spot, the method is direct, but most of needed equipment is expensive, and redundant relative relations among the infrared camera, the area-array camera and the laser are introduced, so that the calibration precision of the camera and the laser is reduced.
Therefore, the most common method at present is to perform external reference calibration by using a single-sided checkerboard as a calibration target and by constraint relation of points, lines and surfaces, but the method has the following problems: firstly, theoretically, 3 or 5 groups of images and laser data with different postures of the checkerboard need to be acquired, but in actual situations, more than 20 groups of experimental data need to be acquired in order to acquire a calibration result with higher precision, and the operation is complicated; and secondly, the initial value of the calibration result needs to be optimized by an L-M algorithm, the optimization needs a more accurate initial value, otherwise, the local minimum is involved, and an accurate and stable calibration result cannot be obtained.
At present, a calibration method based on three mutually perpendicular planes such as a corner is provided, but the method requires that the size of a calibration target is known, and if the measurement of the side length of the corner is not accurate enough, the intersecting line of the corner in an image is generally fuzzy, and the calibration precision is finally influenced.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides a checkerboard trihedron-based camera and laser external reference checking and correcting method and device, so that the technical problems of complexity and low precision of the existing checking and correcting method are solved.
In order to achieve the above object, according to one aspect of the present invention, there is provided a checkerboard trihedron-based camera and laser external reference calibration method applied to a data acquisition device combined by the camera and the laser, wherein the camera and the laser are placed in a constant positional relationship, the checkerboard trihedron is located in front of the data acquisition device, and the camera can completely photograph three faces of the checkerboard trihedron while the laser can scan three orthogonal checkerboard faces, the method includes:
s1: obtaining the position and the posture of the laser relative to the checkerboard trihedron by using a three-point perspective method according to three intersecting lines of a laser scanning surface and the checkerboard trihedron;
s2: obtaining the position and the posture of the camera relative to the tessellated trihedron by utilizing space rear intersection according to the collinear rule between the angular points of the tessellated trihedron and the image points corresponding to the angular points;
s3: and obtaining the rotation and translation between the camera and the laser according to the position and the posture of the laser relative to the checkered trihedron and the position and the posture of the camera relative to the checkered trihedron.
Preferably, before step S1, the method further comprises:
and constructing a coordinate system of the checkerboard trihedron, the camera and the laser, wherein the coordinate system of the checkerboard trihedron takes one vertex of the trihedron as an origin of the coordinate system, the intersecting lines of three vertical surfaces are respectively coordinate axes to establish the coordinate system, the coordinate system of the camera takes an optical center of the camera as the origin and is parallel to an imaging plane as an XOY plane, the direction in which the optical center points to the front is taken as a Z axis according to a right-hand coordinate system rule, the coordinate system of the laser takes a scanning center of the laser as the origin, the scanning plane is the XOZ plane, and the Y axis is determined by the right-hand coordinate system rule.
Preferably, step S1 includes:
s1.1: acquiring two-dimensional coordinates of points on three intersecting lines of a laser scanning surface and the checkerboard trihedron in a laser coordinate system;
s1.2: connecting intersection points of the three intersection lines or the extension lines of the three intersection lines pairwise to form an orthogonal triangular pyramid, and obtaining the side length of a triangular edge of the triangular pyramid according to a two-dimensional coordinate of points on the three intersection lines in a laser coordinate system, so as to obtain a three-dimensional coordinate of each intersection point in a world coordinate system;
s1.3: and establishing a 2D-3D corresponding relation by utilizing three pairs of laser intersection points and corresponding object space points according to the coordinates of the intersection points in the laser coordinate system and the coordinates of the intersection points in the world coordinate system to obtain the position and the posture of the laser relative to the checkerboard trihedron.
Preferably, step S2 includes:
s2.1: acquiring a collinear equation between the angular points of the checkerboard trihedron and the image points corresponding to the angular points;
s2.2: and developing the nonlinear collinear equation into a linear equation, and utilizing a least square method through a plurality of known points which are uniformly distributed on the tessellated trihedron to minimize the sum of squares of linearly estimated residuals, thereby finally obtaining the position and the posture of the camera relative to the tessellated trihedron.
Preferably, step S3 includes:
from RCL＝RcRL -1And TCL＝TC-RCRL -1TLObtaining rotation and translation between the camera and the laser, wherein RCLRepresenting a rotation between the camera and the laser, RcRepresenting the position of the camera relative to the tessellated trihedron, RLRepresenting the position of the laser with respect to the tessellated trihedron, TCLRepresenting a translation between the camera and the laser, TCRepresenting the pose of the camera with respect to the tessellated trihedron, TLRepresenting the pose of the laser relative to the tessellated trihedron.
According to another aspect of the present invention, there is provided a checkerboard trihedron-based camera and laser external reference calibration apparatus, applied to a data acquisition device combining the camera and the laser, wherein the camera and the laser are placed in a constant positional relationship, the checkerboard trihedron is located in front of the data acquisition device, and the camera can completely photograph three faces of the checkerboard trihedron, and the laser can scan three orthogonal checkerboard faces, the apparatus includes:
the first posture determining module is used for obtaining the position and the posture of the laser relative to the checkered trihedron by using a three-point perspective method according to three intersecting lines of a laser scanning surface and the checkered trihedron;
the second pose determining module is used for obtaining the position and the pose of the camera relative to the checkerboard trihedron by utilizing space rear intersection according to a collinear rule between the angular points of the checkerboard trihedron and the image points corresponding to the angular points;
and the external reference calibration module is used for obtaining the rotation and translation between the camera and the laser according to the position and the posture of the laser relative to the checkered trihedron and the position and the posture of the camera relative to the checkered trihedron.
Preferably, the apparatus further comprises:
the coordinate system construction module is used for constructing a coordinate system of the checkerboard trihedron, the camera and the laser, wherein the coordinate system of the checkerboard trihedron takes one vertex of the trihedron as an origin of the coordinate system, the intersecting lines of three vertical planes are respectively taken as coordinate systems established by coordinate axes, the coordinate system of the camera takes a camera optical center as the origin and is parallel to an imaging plane as an XOY plane, the direction in which the optical center points to the front is taken as a Z axis according to a right-hand coordinate system rule, the coordinate system of the laser takes a scanning center of the laser as the origin, the scanning plane is the XOZ plane, and the Y axis is determined by the right-hand coordinate system rule.
Preferably, the first posture determination module includes:
the first coordinate determination module is used for acquiring two-dimensional coordinates of points on three intersecting lines of the laser scanning surface and the checkerboard trihedron in a laser coordinate system;
the second coordinate determination module is used for forming an orthogonal triangular pyramid by pairwise connecting intersection points of the three intersection lines or extension lines of the three intersection lines, obtaining the side length of a triangular edge of the triangular pyramid according to two-dimensional coordinates of points on the three intersection lines in a laser coordinate system, and further obtaining three-dimensional coordinates of the intersection points in a world coordinate system;
and the first posture determining submodule is used for establishing a 2D-3D corresponding relation between three pairs of laser intersection points and corresponding object space points according to the coordinates of the intersection points in the laser coordinate system and the coordinates of the intersection points in the world coordinate system to obtain the position and the posture of the laser relative to the checkerboard trihedron.
Preferably, the second posture determination module includes:
the acquisition module is used for acquiring a collinear equation between the angular points of the checkerboard trihedron and the image points corresponding to the angular points;
and the second posture determining submodule is used for developing the nonlinear collinear equation into a linear equation, minimizing the sum of squares of linear estimation residuals by using a least square method through a plurality of known points which are uniformly distributed on the checkerboard trihedron, and finally obtaining the position and the posture of the camera relative to the checkerboard trihedron.
Preferably, the external reference calibration module is used for calibrating the calibration module by RCL＝RcRL -1And TCL＝TC-RCRL -1TLObtaining rotation and translation between the camera and the laser, wherein RCLRepresenting a rotation between the camera and the laser, RcRepresenting the position of the camera relative to the tessellated trihedron, RLRepresenting the position of the laser with respect to the tessellated trihedron, TCLRepresenting a translation between the camera and the laser, TCRepresenting the pose of the camera with respect to the tessellated trihedron, TLRepresents the laserAttitude with respect to the tessellated trihedron.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
the invention designs an orthogonal trihedron which is simple and easy to manufacture, and a checkerboard with known size is attached to the surface. The checkerboard trihedron is used as a calibration object, and a convenient and flexible camera and laser external reference calibration method is provided. The invention uses the checkerboard trihedron as the reference datum 'medium' of the camera and the laser, and solves the postures and positions of the line laser and the area array camera relative to the checkerboard trihedron by continuously changing the postures of the checkerboard of the trihedron in the acquisition equipment and respectively using a three-point perspective method and a method of combining the collinear rule between the checkerboard trihedron angular points and the corresponding image points thereof with the space rear intersection. The method is flexible to operate, simple to use, capable of reducing the experiment times, capable of obtaining a large amount of observation data, capable of rapidly and accurately obtaining the calibration result of the camera and the laser compared with the existing method, and high in feasibility in engineering projects.
Drawings
FIG. 1 is a schematic flow chart of a method provided by an embodiment of the present invention;
FIG. 2 is a schematic diagram of a device coordinate system transformation relationship provided in an embodiment of the present invention;
FIG. 3 is a schematic diagram of a tessellated trihedron arrangement according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a calibration process of a single-line laser according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an optical camera calibration process according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides an external reference checking and correcting method for an area-array camera and a line laser based on a checkerboard trihedron, which is flexible to use and easy to operate, only needs to acquire one group of observation data, is uniform in angular point distribution and easy to extract, and has known coordinates, and the checking and correcting result has the advantages of high precision and good robustness.
The data acquisition equipment of the invention is a camera-laser integrated device, which is provided with a table array camera and a line laser. The camera and laser are first mounted in a fixed position, with the positional relationship between the two being maintained unchanged. The checkerboard trihedron is arranged in front of the device, and the posture of the checkerboard of the trihedron is adjusted, so that the camera can completely shoot three surfaces of the checkerboard trihedron, and meanwhile, the laser can scan three orthogonal checkerboard surfaces. And acquiring a group of image and laser data, calculating the postures and positions of the camera and the laser relative to the checkerboard trihedron by using the group of image and laser data, and solving the external parameters between the camera and the laser by using the checkerboard trihedron as a medium.
Fig. 1 is a schematic flow chart of a method provided in an embodiment of the present invention, which specifically includes the following steps:
(1) a camera and a laser are configured. The camera and the laser are installed on the fixing device, and the camera and the laser are kept in a static state during observation. The checkerboard trihedron is placed in front of the device and is continuously shaken to change the posture of the checkerboard trihedron, so that the laser can scan three orthogonal surfaces simultaneously, and the camera can completely shoot all the trihedrons. Fig. 3 shows a checkerboard trihedron layout.
(2) The coordinate system of each device is determined. Fig. 2 shows a coordinate system conversion relationship between respective devices. Checkerboard three-dimensional coordinate system, namely world coordinate system (O)w-XwYwZw) One vertex of the trihedron is taken as the origin of a coordinate system, and the intersecting lines of the three vertical planes are X respectivelyw，Yw，ZwA coordinate system established by the axes; camera coordinate system (O)c-XcYcZc) Based on the principle of pinhole imaging model, i.e. using the optical center of the camera as the origin and making it parallel to the imaging plane as Xc-OC-YcPlane, with the optical center pointing in the forward direction as Z according to the rule of the right-hand coordinate systemcA shaft. Laser coordinate system (O)L-XLYLZL) The scanning center of the laser is used as the origin, and the scanning plane is XL-OL-ZLPlane, determining Y by right-hand coordinate system ruleLA shaft.
(3) And acquiring camera and laser data. The camera-laser integrated device is opened, the checkered trihedron is continuously shaken in front of the device to change the posture of the checkered trihedron, the laser data can be ensured to be simultaneously scanned to three orthogonal surfaces, the camera can simultaneously shoot the complete trihedron, the checkered trihedron is kept in the stable state, and a group of image data and laser data are collected.
(4) As shown in FIG. 4, when the line laser works, the scanning surface emitting laser light intersects with the three surfaces of the checkerboard trihedron to obtain three intersecting lines, which are l1,l2,l3. The two-dimensional coordinates of the points on these intersecting lines in the laser coordinate system are known. In addition, because three surfaces of the trihedron are orthogonal to each other, the intersection points of three intersection lines or the extension lines thereof are necessarily positioned on three orthogonal edges of the checkerboard trihedron, two intersection points are connected with each other to form an orthogonal triangular pyramid, and the three edges O of the triangular pyramid can be calculated according to laser coordinateswP1，OwP2，OwP3And then obtaining the three-dimensional coordinates of the intersection point of the scanning lines in the world coordinate system. Because the coordinates of the intersection points of the three laser lines in the laser and world coordinate systems are known, the position and posture of the laser are solved by establishing a 2D-3D corresponding relation between three pairs of laser points and object points, and the problem can be regarded as a simplified P3P (three-point perspective).
The scanning plane of the laser can be set to Y by the configuration of the line laserL0, so points in the laser coordinate system can be represented as
Note I'iIs IiAt YLProjection of 0 plane, denoted
First of all with pi1，π2，π3Representing three faces of a trihedral checkerboard, the points scanned by the laser on each face being fitted with three straight lines and projected onto YL0 plane, denoted L1，L2And L3. Intersection point P of three scanning linesi(i ═ 1,2,3) in YL0 projection point Pi' is calculated as follows:
projected point P obtained by calculationiThe coordinates of' can be found to be P in the laser coordinate systemiThe coordinates of (a). Origin O of coordinate systemwAnd three points of intersection P1，P2，P3Can form a triangular pyramid with three perpendicular sides, wherein OwBeing the apex of a triangular pyramid, it is clear that this is a P3P problem. The side length of the triangle at the base of the triangular pyramid is calculated as follows:
because three faces are mutually vertical to form a right triangle, the edge length of the triangular pyramid can be calculated by the pythagorean theorem, and I O is setwP1||＝λ1，||OwP2||＝λ2，||OwP3||＝λ3Then, there are:
compared with the traditional P3P problem, the Pythagorean theorem avoids using more side length cross terms generated in the cosine theorem, and greatly simplifies the P3P problem. The method solves the problem that the condition that 8 solutions exist in the formula is solved by using positive numbers of three edges of the trihedron as a precondition, and the side lengths of the three edges are obtained as follows:
thus, the coordinates of the intersection of the three scanning lines in the three-dimensional coordinate system, respectively denoted as Q, can be easily obtained1＝(λ1,0,0)T，Q2＝(0,λ2,0)T，Q3＝(0,0,-λ3)TRespectively correspond to P1，P2，P3. Therefore, the relation between the laser coordinate system and the three-dimensional coordinate system is equivalent to PiAnd Qi(i is 1,2,3), the rotation and translation matrix [ R ] between the two coordinate systems can be solved according to the P3P principleC,TC]。
(5) And (5) checking the external reference of the camera. By using a checkerboard three-dimensional coordinate system as a 'conversion tool' between the calibration laser and the camera. The imaging mode of the camera is a pinhole imaging mode, and the point on the shot image, the point in the object space and the optical center of the camera are positioned on the same straight line, namely, the collinear equation is satisfied. And developing the nonlinear collinear equation into a linear equation according to the Taylor technology, solving the problem of an overdetermined equation set by using a least square method through a large number of uniformly distributed known points on the checkerboard trihedron, so that the sum of squares of linearly estimated residuals is minimum, and finally obtaining the external parameters of the camera.
As shown in FIG. 5, the camera is configured to image in a pinhole manner, where a point a on the captured image is located with a point A in the object space and an optical center O of the cameraCOn the same straight line, i.e. the collinearity equation is satisfied:
wherein the camera inner orientation element is (x)0,y0,f)，(x0,y0) The coordinate of the image principal point is represented, f represents the main distance of the camera, and the coordinate of the image principal point and the f can be calibrated in advanceAnd (4) obtaining. The high-precision coordinates of the control points are A ═ X, Y and Z, and the corresponding coordinates of the image points are a ═ X, Y, which can be picked up from the image manually. a isi，bi，ci(i ═ 1,2,3) is the attitude parameter of the camera in the three-dimensional coordinate systemω, κ and position parameter Xs,Ys,ZsIs obtained by non-linear combination of (a). Therefore, the coordinates of the image points corresponding to the control points obtained by the above equation (5) are nonlinear functions of the set Φ of the pose parameters and the position parameters to be obtained.
Given an initial parameter Φ0The initial approximation (x), (y) of the image point coordinates x, y can be obtained by introducing collinearity equations. Near the image point approximate value, a Taylor series expansion is utilized, high-order terms above two degrees are ignored, and a collinear equation is converted into the following linear form:
wherein the content of the first and second substances,
the coefficient of the first order of Taylor expansion for the position parameter and the attitude parameter of the collinearity equation is given by the initial parameter phi0The above coefficients are known values. dXs,dYs,dZs,
d omega and d kappa are variation of the position parameter and the attitude parameter, and since the attitude parameter and the position parameter are unknown numbers, the variation is also unknown parameter,is an estimated value calculated using the above equation (6) for the initial approximate values (x), (y). The collinear equation in which the unknowns are the attitude parameter and the position parameter is thus converted into the above equation (6) in which the amounts of change in the attitude parameter and the position parameter are unknowns, that is, becomes an equation regarding the change parameter d Φ.
From equation (6), it can be found that the equation set has 6 unknowns, but each control point and its corresponding image point can only list 2 equations, so at least 3 points are needed to obtain a solution of 6 unknowns, and the result calculated by using only 3 control points is very occasional and not accurate enough. Therefore, in order to further improve the accuracy of the experiment, n control points which are uniformly distributed on the checkerboard trihedron need to be selected on the image, and the influence of the occurring accidental errors on the result is reduced by using a large number of control points, so as to obtain a more accurate result. n (n is more than or equal to 3) control points can form 2n equations, the unknown parameters are only 6, and the problem of the over-determined equation set is solved by using a least square method, so that the sum of squares of linear estimation residuals is minimum, namely:
wherein the content of the first and second substances,and
representing an observation of the coordinates of the image point. According to a free extreme value method in mathematics, (7) a minimum value is obtained when partial derivative of the d phi is zero, and the optimal pose parameter variation d phi can be obtained. Because the taylor expansion term is only truncated at one term in the linearization process, the subsequent multiple expansion terms are omitted, and the initial value of the unknown number is rough, the last calculation result needs to be corrected, namely, iterative calculation is carried out. The variable quantity d phi of the unknown parameter and the initial value phi of the unknown parameter which is calculated in an iterative way0Adding the three attitude parameters to be used as approximate values of the pose parameters of the next iteration, and repeating the calculation process until the variation of the three attitude parameters
Omega and kappa are both less than 0.1′Stopping iteration, and obtaining an external parameter (R) of the camera coordinate system relative to the three-dimensional coordinate systemc，Tc]。
Tc＝[Xs,Ys,Zs]T
(6) The external parameters between the camera and the laser are related by a checkerboard trihedral control field coordinate system. Therefore, external parameters of the camera and the laser which are respectively positioned in the coordinate system of the trihedral control field are solved, and then the external parameters are simultaneously solved. As shown in FIG. 2, the coordinates of any point P in the space under the checkerboard three-dimensional coordinate system, the camera coordinate system and the laser coordinate system can be respectively expressed as Pw＝(Xw,Yw,Zw)T，Pc＝(Xc,Yc,Zc)TAnd PL＝(XL,YL,ZL)TWhile the homogeneous coordinate of the image point of the P point on the image is qc＝(u,v,1)T. The internal reference of the camera is K, and the external reference of the camera and the laser relative to the three-dimensional coordinate system is Rc，TcAnd { R }and { R }L，TLThe external parameter between the camera and the laser is RCL，TCLAnd satisfies the following formula:
the expression between camera and laser can therefore be expressed as:
RCL＝RcRL -1
TCL＝TC-RCRL -1TL
in another embodiment of the present invention, there is further provided a checkerboard trihedron-based camera and laser external reference calibration apparatus, including:
the first posture determining module is used for obtaining the position and the posture of the laser relative to the checkered trihedron by using a three-point perspective method according to three intersecting lines of a laser scanning surface and the checkered trihedron;
the second pose determining module is used for obtaining the position and the pose of the camera relative to the checkerboard trihedron by utilizing space rear intersection according to a collinear rule between the angular points of the checkerboard trihedron and the image points corresponding to the angular points;
and the external reference calibration module is used for obtaining the rotation and translation between the camera and the laser according to the position and the posture of the laser relative to the checkered trihedron and the position and the posture of the camera relative to the checkered trihedron.
The specific implementation of each module may refer to the description in the method embodiment, and the embodiment of the present invention will not be repeated.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A camera and laser external reference checking and correcting method based on a checkerboard trihedron is applied to a data acquisition device combined by the camera and the laser, wherein the position relation placed between the camera and the laser is unchanged, the checkerboard trihedron is positioned in front of the data acquisition device, the camera can completely shoot three faces of the checkerboard trihedron, and meanwhile, the laser can scan three orthogonal checkerboard faces, and the method comprises the following steps:
s1: obtaining the position and the posture of the laser relative to the checkerboard trihedron by using a three-point perspective method according to three intersecting lines of a laser scanning surface and the checkerboard trihedron;
s2: obtaining the position and the posture of the camera relative to the tessellated trihedron by utilizing space rear intersection according to the collinear rule between the angular points of the tessellated trihedron and the image points corresponding to the angular points;
s3: and obtaining the rotation and translation between the camera and the laser according to the position and the posture of the laser relative to the checkered trihedron and the position and the posture of the camera relative to the checkered trihedron.
2. The method according to claim 1, wherein before step S1, the method further comprises:
and constructing a coordinate system of the checkerboard trihedron, the camera and the laser, wherein the coordinate system of the checkerboard trihedron takes one vertex of the trihedron as an origin of the coordinate system, the intersecting lines of three vertical surfaces are respectively coordinate axes to establish the coordinate system, the coordinate system of the camera takes an optical center of the camera as the origin and is parallel to an imaging plane as an XOY plane, the direction in which the optical center points to the front is taken as a Z axis according to a right-hand coordinate system rule, the coordinate system of the laser takes a scanning center of the laser as the origin, the scanning plane is the XOZ plane, and the Y axis is determined by the right-hand coordinate system rule.
3. The method according to claim 2, wherein step S1 includes:
s1.1: acquiring two-dimensional coordinates of points on three intersecting lines of a laser scanning surface and the checkerboard trihedron in a laser coordinate system;
s1.2: connecting intersection points of the three intersection lines or the extension lines of the three intersection lines pairwise to form an orthogonal triangular pyramid, and obtaining the side length of a triangular edge of the triangular pyramid according to a two-dimensional coordinate of points on the three intersection lines in a laser coordinate system, so as to obtain a three-dimensional coordinate of each intersection point in a world coordinate system;
s1.3: and establishing a 2D-3D corresponding relation by utilizing three pairs of laser intersection points and corresponding object space points according to the coordinates of the intersection points in the laser coordinate system and the coordinates of the intersection points in the world coordinate system to obtain the position and the posture of the laser relative to the checkerboard trihedron.
4. The method according to claim 3, wherein step S2 includes:
s2.1: acquiring a collinear equation between the angular points of the checkerboard trihedron and the image points corresponding to the angular points;
s2.2: and developing the nonlinear collinear equation into a linear equation, and utilizing a least square method through a plurality of known points which are uniformly distributed on the tessellated trihedron to minimize the sum of squares of linearly estimated residuals, thereby finally obtaining the position and the posture of the camera relative to the tessellated trihedron.
5. The method according to claim 4, wherein step S3 includes:
from RCL＝RcRL -1And TCL＝TC-RCRL -1TLObtaining rotation and translation between the camera and the laser, wherein RCLRepresenting a rotation between the camera and the laser, RcRepresenting the position of the camera relative to the tessellated trihedron, RLRepresenting the position of the laser with respect to the tessellated trihedron, TCLRepresenting a translation between the camera and the laser, TCRepresenting the pose of the camera with respect to the tessellated trihedron, TLRepresenting the pose of the laser relative to the tessellated trihedron.
6. The utility model provides a school device is examined with outer reference of laser instrument to camera based on checkerboard trihedron which characterized in that is applied to the camera with the data acquisition equipment of laser instrument combination, wherein, the camera with the positional relationship who places between the laser instrument is unchangeable, checkerboard trihedron is located data acquisition equipment the place ahead, just the camera can be complete shoot three faces of checkerboard trihedron, simultaneously the laser instrument can scan three orthogonal checkerboard faces, the device includes:
the first posture determining module is used for obtaining the position and the posture of the laser relative to the checkered trihedron by using a three-point perspective method according to three intersecting lines of a laser scanning surface and the checkered trihedron;
the second pose determining module is used for obtaining the position and the pose of the camera relative to the checkerboard trihedron by utilizing space rear intersection according to a collinear rule between the angular points of the checkerboard trihedron and the image points corresponding to the angular points;
and the external reference calibration module is used for obtaining the rotation and translation between the camera and the laser according to the position and the posture of the laser relative to the checkered trihedron and the position and the posture of the camera relative to the checkered trihedron.
7. The apparatus of claim 6, further comprising:
the coordinate system construction module is used for constructing a coordinate system of the checkerboard trihedron, the camera and the laser, wherein the coordinate system of the checkerboard trihedron takes one vertex of the trihedron as an origin of the coordinate system, the intersecting lines of three vertical planes are respectively taken as coordinate systems established by coordinate axes, the coordinate system of the camera takes a camera optical center as the origin and is parallel to an imaging plane as an XOY plane, the direction in which the optical center points to the front is taken as a Z axis according to a right-hand coordinate system rule, the coordinate system of the laser takes a scanning center of the laser as the origin, the scanning plane is the XOZ plane, and the Y axis is determined by the right-hand coordinate system rule.
8. The apparatus of claim 7, wherein the first position determination module comprises:
the first coordinate determination module is used for acquiring two-dimensional coordinates of points on three intersecting lines of the laser scanning surface and the checkerboard trihedron in a laser coordinate system;
the second coordinate determination module is used for forming an orthogonal triangular pyramid by pairwise connecting intersection points of the three intersection lines or extension lines of the three intersection lines, obtaining the side length of a triangular edge of the triangular pyramid according to two-dimensional coordinates of points on the three intersection lines in a laser coordinate system, and further obtaining three-dimensional coordinates of the intersection points in a world coordinate system;
and the first posture determining submodule is used for establishing a 2D-3D corresponding relation between three pairs of laser intersection points and corresponding object space points according to the coordinates of the intersection points in the laser coordinate system and the coordinates of the intersection points in the world coordinate system to obtain the position and the posture of the laser relative to the checkerboard trihedron.
9. The apparatus of claim 8, wherein the second position determination module comprises:
the acquisition module is used for acquiring a collinear equation between the angular points of the checkerboard trihedron and the image points corresponding to the angular points;
and the second posture determining submodule is used for developing the nonlinear collinear equation into a linear equation, minimizing the sum of squares of linear estimation residuals by using a least square method through a plurality of known points which are uniformly distributed on the checkerboard trihedron, and finally obtaining the position and the posture of the camera relative to the checkerboard trihedron.
10. Device according to claim 9, characterized in that the external reference calibration module is specifically adapted to be calibrated by RCL＝RcRL -1And TCL＝TC-RCRL -1TLObtaining rotation and translation between the camera and the laser, wherein RCLRepresenting a rotation between the camera and the laser, RcRepresenting the position of the camera relative to the tessellated trihedron, RLRepresenting the position of the laser with respect to the tessellated trihedron, TCLRepresenting a translation between the camera and the laser, TCRepresenting the pose of the camera with respect to the tessellated trihedron, TLRepresenting the pose of the laser relative to the tessellated trihedron.
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