CN114964316A - Position and attitude calibration method and device, and method and system for measuring target to be measured - Google Patents
Position and attitude calibration method and device, and method and system for measuring target to be measured Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C25/00—Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
- G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
- G01B21/04—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness by measuring coordinates of points
- G01B21/042—Calibration or calibration artifacts
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/70—Determining position or orientation of objects or cameras
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
- H04N13/20—Image signal generators
- H04N13/204—Image signal generators using stereoscopic image cameras
- H04N13/246—Calibration of cameras
Abstract
The invention relates to the technical field of vision measurement and image detection, and provides a position and posture calibration method and device, and a method and system for measuring a target to be measured. The calibration method comprises the following steps: the stereoscopic vision measurement system comprises a first camera and a second camera, n bright spots are projected to a target to be measured, the stereoscopic vision camera shoots a target image to be measured with the n bright spots, image points corresponding to the n bright spots in the target image to be measured are extracted, and image points of the second camera and image points of the first camera are matched with each other; calculating the normalized image coordinates of the image points of the stereoscopic vision camera; and respectively solving the relative position posture of each second camera and the first camera according to the image points with the same name and the normalized image coordinates of the image points of the first camera and the second camera. The scheme can ensure the accuracy of the measured relative position and posture and is not limited to various application occasions.
Description
Technical Field
The invention relates to the technical field of vision measurement and image detection, in particular to a method and a device for calibrating the relative position and attitude of a stereoscopic vision measurement system, a method for measuring a target to be measured and a self-calibrated measurement system.
Background
The vision measurement is an advanced system which takes computer vision as a theory, adopts an advanced image sensor with high density, low noise and small distortion, and effectively processes binary or gray level images through a high-speed real-time image acquisition system, a special image hardware processing system and a high-performance computer. Usually, a plurality of cameras are used to shoot the target to be measured, so as to measure the target to be measured.
The accuracy of the relative position and orientation between the cameras of a stereo vision measurement system is critical to the accuracy of the stereo vision measurement results. Small relative attitude errors between the cameras can cause large stereo vision measurement errors.
In order to reduce the error of the relative position and attitude, the prior art generally has the following steps: firstly, accurately calibrating the relative position and posture of each camera in advance, and ensuring that the system is stable and the parameters are unchanged when the system is used; in this way, when the use environment conditions are severe (such as impact vibration, etc.), it is difficult to ensure the stability of the measurement system structure and the stability and invariability of the camera parameters. Secondly, each camera is fixedly connected with an attitude sensor, and the pose variation of the device is read in real time in the using process so as to compensate; by adopting the mode, the sensors fixedly connected are additionally arranged, the high-precision pose sensor is high in cost, and the attitude sensor represented by inertial navigation generally has the problems of time accumulation error and low long-time application precision. Thirdly, control point targets with accurately known coordinates are distributed in a measurement view field, and real-time parameters of each camera are calibrated during measurement; and (3) the condition that the control point is not arranged in the measurement visual field is possible, such as the condition that the target to be measured in the small measurement visual field occupies the full visual field, or the condition that the measurement visual field is continuously changed when the measurement platform is moved. Therefore, the prior art has limited application occasions.
Therefore, it is necessary to develop a method and an apparatus for calibrating the relative position and orientation of a stereoscopic vision measurement system, a method for measuring an object to be measured, and a self-calibrated measurement system, which are not limited to various applications while ensuring the accuracy of the measurement of the relative position and orientation.
Disclosure of Invention
The invention aims to provide a method and a device for calibrating the relative position and the attitude of a stereoscopic vision measuring system, a method for measuring a target to be measured and a self-calibrated measuring system, which can ensure the accuracy of the measured relative position and the attitude and are not limited to various application occasions.
In order to solve the above technical problem, as an aspect of the present invention, there is provided a method for calibrating a relative position and orientation of a stereoscopic vision measurement system, including the steps of:
s1: the stereovision measurement system is used for shooing the target that awaits measuring, and the stereovision measurement system includes m stereovision cameras, and m is the natural number more than or equal to 2, and m stereovision cameras include: a first camera and m-1 second cameras; shooting a target to be detected from different angles by m stereoscopic vision cameras; projecting n bright spots to a target to be detected, wherein the n bright spots are all in the shooting range of the stereoscopic vision camera; n is a natural number greater than or equal to 3;
s2: all stereoscopic vision cameras shoot a target image to be detected with n bright spots, image points corresponding to the n bright spots in the target image to be detected are extracted, and image points of a second camera and image points of a first camera are matched with image points of the second camera in a same name mode;
s3: calculating the normalized image coordinates of the image points of the stereoscopic vision camera;
s4: and respectively solving the relative position posture of each second camera and the first camera according to the image points with the same name and the normalized image coordinates of the image points of the first camera and the second camera.
According to an exemplary embodiment of the present invention, in step S3, the method for calculating the normalized image coordinates of the image point of the stereoscopic vision camera includes:
calculating the normalized image coordinates of the image points according to the internal parameters of the stereoscopic vision camera;
the internal parameters of the stereoscopic vision camera comprise principal point coordinates and equivalent focal length;
the image point normalized image coordinates of the first camera are:
the image point normalized image coordinates of the second camera are:
wherein the principal point coordinate of the first camera is (C) x0 , C y0 ) The equivalent focal length of the first camera is (Fx) 0 , Fy 0 ) The principal point coordinate of the second camera is (C) xj , C yj ) The equivalent focal length of the second camera is (F) xj , F yj )，j=1,2，...，m-1；i=0,1，...，n-1。
According to an exemplary embodiment of the present invention, in step S4, the method for separately solving the relative position and orientation between each second camera and the first camera according to the image point with the same name and the normalized image coordinates of the image points of the first camera and the second camera includes:
setting an initial value of the relative position posture of the camera;
establishing a relative position attitude equation according to the relation between the first camera and the second camera;
listing a relative position attitude equation according to all the image points with the same name;
and solving a relative attitude equation according to the initial value and the listed relative position attitude equation to obtain a corrected value.
According to an exemplary embodiment of the present invention, the method for separately solving the relative position and orientation of each second camera and the first camera according to the image point with the same name and the normalized image coordinates of the image points of the first camera and the second camera further includes: after the correction value is obtained, the correction value is used as a new initial value to continuously solve a new correction value; and repeating the iteration initial value and solving a new correction value until the iteration initial value is repeated until the specified times and/or the error of the initial value calculation of the two times of updating is less than the specified threshold value or the measurement of the target to be measured is finished.
According to an example embodiment of the present invention, the relative attitude equation is:
the second camera and the first camera relative position pose comprises a translation vector and/or a rotation angle;
wherein the translation vector is
The rotation matrix is
At a rotation angle of
The rotation matrix is a trigonometric combination of rotation angles; x, y, z are mutually perpendicular axes, t xj 、t yj 、t zj Representing the length of movement of the camera in three axes, a zj 、a yj 、a xj The angle of the camera rotating around the three axes of z, y and x in turn, r 0j =cosa yj ×cosa zj 、r 1j =sina xj ×sina yj ×cosa zj -cosa xj ×sina zj 、r 2j =cosa xj ×sina yj ×cosa zj +sina xj ×sina xzj 、r 3j =cosa yj ×sina zj 、r 4j =sina xj ×sina yj ×sina zj +cosa xj ×cosa zj 、r 5j =cosa xj ×sina yj ×sina zj -sina xj ×cosa zj 、r 6j =-sina yj 、r 7j =sina xj ×cosa yj 、r 8j =cosa xj ×cosa yj 。
According to an exemplary embodiment of the present invention, the method for solving the relative attitude equation according to the initial value and the listed relative position attitude equation comprises:
adopting a nonlinear optimization method to obtain the final product at the initial value
Calculating a deviation of the translation vector and/or the rotation angle;
to pair
Performing Taylor expansion to obtain a linear equation set of correction quantity related to the translation vector and/or the rotation angle;
performing least square solution on the linear equation set to obtain a correction quantity;
and correcting the translation vector and/or the rotation angle according to the correction amount to obtain a correction value.
The nonlinear optimization method includes a newton iteration method.
As a second aspect of the present invention, a method for measuring an object to be measured is provided, wherein a stereoscopic vision camera of a vision measuring system is calibrated by using the calibration method for the relative position and posture of the stereoscopic vision measuring system;
and measuring the object to be measured by using a stereoscopic vision camera.
As a third aspect of the present invention, there is provided a relative position and orientation calibration apparatus for a stereo vision measurement system, comprising:
a scattered bright spot irradiator capable of irradiating n bright spots to a target to be measured, wherein n is a natural number greater than or equal to 3;
the homonymous image point matching module is used for extracting image points corresponding to the n bright points in the target image to be detected and respectively matching the image points of the second camera with the image points of the first camera;
the image coordinate calculation module is used for calculating the normalized image coordinates of the image points of the stereoscopic vision camera;
the relative position and posture calculation module is used for respectively solving the relative position and posture of each second camera and the first camera according to the image points with the same name and the normalized image coordinates of the image points of the first camera and the second camera;
wherein, the stereovision measurement system is used for shooing the target that awaits measuring, and the stereovision measurement system includes m stereovision cameras, and m is the natural number more than or equal to 2, and m stereovision cameras include: a first camera and m-1 second cameras; the m stereoscopic vision cameras shoot the target to be measured from different angles.
According to an exemplary embodiment of the present invention, the scattered bright spot irradiator is a laser.
As a fourth aspect of the present invention, there is provided a self-calibrating measurement system comprising:
the device for calibrating the relative position and posture of the stereoscopic vision measuring system and the stereoscopic vision measuring system are provided.
According to an example embodiment of the present invention, the stereo vision measurement system calibrates the first camera and the second camera according to the relative position pose.
The invention has the beneficial effects that:
the scheme adopts a mode of illuminating bright spots on the target to be detected to calibrate the stereoscopic vision camera, can adapt to the conditions that the surface of the target to be detected has no stable texture and the environmental illumination condition is poor, has simple equipment for spreading the bright spots, has no structural stability and precision requirements in the processes of preparation, installation and use, and has wide application range; the method can calibrate the attitude parameters of the relative position of the stereo vision camera in real time, ensures the precision of stereo vision measurement under the conditions of parameter disturbance, change and the like of a stereo vision measurement system, and adapts to the conditions that the motion of a measurement scene changes, the region of the target to be measured cannot be provided with a calibrated target point and the like because bright spots are arranged on the target to be measured and a mode of actively irradiating the region of the target to be measured along with the stereo vision measurement system to obtain characteristic points is adopted.
Drawings
Fig. 1 is a schematic diagram showing a configuration of a relative position and orientation calibration apparatus of a stereo vision measurement system.
Fig. 2 schematically shows a positional relationship diagram when the relative position and orientation of the stereo vision measurement system are calibrated.
Fig. 3 schematically shows an imaging schematic of a stereoscopic vision camera.
Wherein 1-the target to be measured, 2-the scattered light spot irradiator, C 0 First camera, C j -a second camera.
Detailed Description
The following detailed description of embodiments of the invention, but the invention can be practiced in many different ways, as defined and covered by the claims.
As a first embodiment of the present invention, there is provided a relative position and orientation calibration device for a stereo vision measurement system, as shown in fig. 1, including: the device comprises a distributed bright spot irradiator, a same-name image point matching module, an image coordinate calculation module and a relative position and posture calculation module.
The scattered bright spot irradiator can irradiate n bright spots to the target to be measured, wherein n is a natural number which is more than or equal to 3. The scattered light spot irradiator uses a laser.
Homonymous image point matching module and first camera C 0 And a second camera C j And the connection is used for extracting image points corresponding to the n bright points in the target image to be detected, and respectively matching the image points of the second camera with the image points of the first camera by means of the same name.
Image coordinate calculation module and first camera C 0 Second camera C j And the connection is used for calculating the normalized image coordinates of the image points of the stereoscopic vision camera.
The relative position and posture calculation module is connected with the homonymous image point matching module and the image coordinate calculation module and is used for respectively solving the relative position and posture of each second camera and each first camera according to the homonymous image points and the normalized image coordinates of the image points of the first camera and the second camera.
Wherein, stereovision measurement system is used for shooing the target that awaits measuring, and stereovision measurement system includes m stereovision cameras, and m is the natural number more than or equal to 2, and m stereovision cameras include: a first camera and m-1 second cameras; the m stereoscopic vision cameras shoot the target to be measured from different angles.
The device of this scheme of adoption can solve the relative position gesture of each second camera and first camera in real time, and the accuracy is high.
As a second embodiment of the present invention, there is provided a method for calibrating a relative position and orientation of a stereo vision measurement system, which is implemented by the apparatus of the first embodiment. As shown in fig. 2, the stereoscopic vision measuring system is used for shooting an object 1 to be measured, and includes m stereoscopic vision cameras, where m is a natural number greater than or equal to 2, and the m stereoscopic vision cameras include: a first camera C 0 And m-1 second cameras C j J =1, 2.., m-1. The m stereoscopic vision cameras shoot the object 1 to be measured from different angles. M in FIG. 2 is 2, with a first camera C 0 For reference, the second camera C is calculated separately j And a first camera C 0 In a relative position posture of the camera, adding a second camera C j Calculates one more second camera C j And a first camera C 0 The relative position and posture of the invention do not influence the scheme to be protected. Second camera C j Indicating the jth second camera.
Before calibration, the internal parameters of the stereo vision camera have been calibrated since they are unchanged. The internal parameters of the stereoscopic vision camera include principal point coordinates and an equivalent focal length. As shown in FIG. 3, the real geographic position coordinate of the optical center of the stereoscopic vision camera is (X) 0 ，Y 0 ，Z 0 ) The coordinates of the optical center, i.e., the principal point, imaged by the camera are (x) c ，y c ). The image surface of the camera image has a pixel size of (d) x ，d y ) Focal length of camera is f, equivalent focal length f in x direction x =f/d x Equivalent focal length f in the y-direction y =f/d y The equivalent focal length is the normalized focal length on the x-axis and the y-axis. In fig. 3, the coordinates of the true geographic location of the bright point are (X, Y, Z), the optical center and the bright point are connected into a straight line, and the image point (X, Y) is displayed on the image plane of the camera.
The calibration method comprises the following steps:
s1: the scattered bright spot irradiator 2 projects n bright spots to the target 1 to be measured, wherein the n bright spots are all in the shooting range (measurement field) of the stereoscopic vision camera; n is a natural number of 3 or more. The number of n is determined according to the number of parameters of the relative position posture which needs to be solved finally, and the equation can be solved only if the number of n is more than or equal to the number of parameters of the relative position posture. The n bright spots are distributed uniformly as much as possible.
S2: all stereoscopic vision cameras shoot an image of a target 1 to be detected with n bright spots, the image point matching module extracts image points corresponding to the n bright spots in the image of the target 1 to be detected, and the second cameras C are respectively used j Image point and the first camera C 0 The image points of the image are matched with the image points of the same name.
The scattered bright spot irradiator 2 irradiates n bright spots, namely a bright spot 0, a bright spot 1, a bright spot 2, a bright spot. The image points of the n bright points in the image of the target 1 to be detected are the image point 0, the image point 1, the image point 2, the image point n-1 respectively. A second camera C j Image point 0 and the first camera C 0 Is matched with the second camera C j Image point 1 and the first camera C 0 The image point 1 of (a) is matched, and so on, the second camera C is used j Image point n-1 and the first camera C 0 Is matched to the image point n-1. First camera C 0 Image point i and the second camera C j The image point i of (2) is the image point of the same name. First camera C 0 Has the coordinate of (x) 0,i , y 0,i ) Second camera C j Has the coordinate of (x) j,i , y j,i )，i=0,1，...，n-1。
S3: the normalized image coordinates of the image points of the stereoscopic vision camera are calculated.
And calculating the normalized image coordinates of the image points according to the internal parameters of the stereoscopic vision camera.
First camera C 0 The normalized image coordinates of the image point i are:
second camera C j The normalized image coordinates of the image point i are:
wherein the first camera C 0 Has a principal point coordinate of (C) x0 , C y0 ) First camera C 0 Has an equivalent focal length of (F) x0 , F y0 ) Second camera C j Has a principal point coordinate of (C) xj , C yj ) Second camera C j Has an equivalent focal length of (F) xj , F yj )，j=1,2，...，m-1；i=0,1，...，n-1。
The coordinates of the image point on the image plane can be obtained as the x and y coordinates, as shown in fig. 3, the image point is on the connecting line of the bright point and the optical center, and as long as the bright point is on the connecting line, the image point at the same position is present on the image, so the z coordinate of the image point is unknown, and it is necessary to set the z coordinate of the image point to 1, and normalize the coordinates of the image point. The coordinate values of the normalized image represent the values after x, y, z normalization from top to bottom.
S4: according to the same name image point and the first camera C 0 And a second camera C j Respectively solving the normalized image coordinates of the image points to obtain each second camera C j And a first camera C 0 Relative position attitude.
Each second camera C j And a first camera C 0 The calculation method of the relative position and posture is the same, and a second camera C is used j And a first camera C 0 Calculation of the relative position posture is taken as an example.
Second camera Cj and first camera C 0 The relative position posture includes translationVector and/or rotation angle.
The translation vector is
The rotation matrix is
At a rotation angle of
The rotation matrix is a trigonometric combination of rotation angles. Each element of the rotation matrix being a second camera C j Relative to the first camera C 0 Angle of rotation a xj ，a yj ，a zj The trigonometric function combination of (1); x, y, z are mutually perpendicular axes, t xj 、t yj 、t zj Representing the length of movement of the camera in three axes, a zj 、a yj 、a xj The angle of the camera rotating around the three axes of z, y and x in turn, r 0j =cosa yj ×cosa zj 、r 1j =sina xj ×sina yj ×cosa zj -cosa xj ×sina zj 、r 2j =cosa xj ×sina yj ×cosa zj +sina xj ×sina xzj 、r 3j =cosa yj ×sina zj 、r 4j =sina xj ×sina yj ×sina zj +cosa xj ×cosa zj 、r 5j =cosa xj ×sina yj ×sina zj -sina xj ×cosa zj 、r 6j =-sina yj 、r 7j =sina xj ×cosa yj 、r 8j =cosa xj ×cosa yj 。
The translation vector is three parameters, t xj ，t yj ，t zj (ii) a The angle of rotation is three parameters, a xj ，a yj ，a zj . If the translation vector is known, only three parameters of the rotation angle need to be solved, and the number of the bright spots n is more than or equal to 3; if the rotation angle is known, only three parameters of the translation vector, of the bright point n, need to be solvedIf the number is 3 or more, it is difficult to acquire high-precision attitude data, and therefore the rotation angle is rarely known. If the translation vector and the rotation angle are unknown, six parameters need to be solved, and the number of the bright points n is larger than or equal to 6. The more the bright points n are, the more the equation system is solved, the more accurate the obtained numerical value is, but the more the calculation amount is, generally the bright points are required to be uniformly distributed in the field of view, and the number of the bright points is dozens or hundreds. Therefore, the number of the bright spots n is preferably 20 to 999.
S401: and setting an initial value of the relative position posture of the camera. The initial value of the position may be set to 0 or to data close to the actual relative position value. The initial value of the pose is a 3 x 3 identity matrix.
S402: according to the first camera C 0 And a second camera C j The relationship of (a) establishes a relative position attitude equation.
According to the stereoscopic vision imaging relationship:
the formula is related to t xj ，t yj ，t zj ，a xj ，a yj ，a zj The equation of (2) is converted into a relative attitude equation.
Jth second camera C j And a first camera C 0 The relative attitude equation of (a) is:
s403: and listing the relative position and attitude equation according to all the image points with the same name.
Listing the relative position attitude equation of the image point 0 with the same name, listing the relative position attitude equation of the image point 1 with the same name, and so on, listing the relative position attitude equation of the image point n-1 with the same name.
S404: and solving a relative attitude equation according to the initial value and the listed relative position attitude equation to obtain a corrected value.
The method for solving the relative attitude equation according to the initial value and the listed relative position attitude equation comprises the following steps:
adopting a nonlinear optimization method to carry out the operation at an initial value
Calculating a deviation of the translation vector and/or the rotation angle;
to pair
Performing Taylor expansion to obtain a linear equation set of correction quantity related to the translation vector and/or the rotation angle;
solving the linear equation set by a least square method to obtain a correction quantity;
and correcting the translation vector and/or the rotation angle according to the correction amount to obtain a correction value.
The nonlinear optimization method comprises a gradient descent method, a Newton iteration method, a Gaussian Newton method, a Levenberg-Marquardt method, a Dog-leg method and the like. Newton's iterative method is preferred.
The gradient descent method adopts a method of performing first-order taylor approximation on an objective function.
The Newton iteration method is approximate to the second-order Taylor of the objective function, and a Hessain matrix needs to be calculated.
Gauss Newton method using J T J approximates the Hessain matrix.
Levenberg-Marquardt method combines gradient descent method and Gauss Newton method, in order to ensure approximate Hessain matrix positive, at J T And adding a damping term to J.
There are specifically the following three cases:
in the first case, if the translation vector and the rotation angle are corrected, t xj ，t yj ，t zj ，a xj ，a yj ，a zj Are unknown:
adopting a nonlinear optimization method to obtain the final product at the initial value
For translation vector t xj ，t yj ，t zj And a rotation angle a xj ，a yj ，a zj Calculating a deviation derivative;
for is to
Taylor expansion is carried out to obtain a vector t related to translation xj ，t yj ，t zj And a rotation angle a xj ，a yj ，a zj Correction amount dt of xj ，dt yj ，dt zj ，da xj ，da yj ，da zj A system of linear equations of;
the linear equation set is solved by a least square method to obtain the correction dt xj ，dt yj ，dt zj ，da xj ，da yj ，da zj ；
According to the correction dt xj ，dt yj ，dt zj ，da xj ，da yj ，da zj For translation vector t xj ，t yj ，t zj And a rotation angle a xj ，a yj ，a zj And (5) correcting:
and obtaining a correction value.
Second case, if only the translation vector is corrected, t xj ，t yj ，t zj Is unknown, a xj ，a yj ，a zj To be known:
adopting a nonlinear optimization method to obtain the final product at the initial value
For translation vector t xj ，t yj ，t zj Calculating a deviation derivative;
to pair
Taylor expansion is carried out to obtain a vector t related to translation xj ，t yj ，t zj Correction amount dt of xj ，dt yj ，dt zj A system of linear equations of;
performing least square method on the linear equation setSolving to obtain the correction dt xj ，dt yj ，dt zj ；
According to the correction dt xj ，dt yj ，dt zj For translation vector t xj ，t yj ，t zj And (5) correcting:
Third, if only the rotation angle is corrected, a xj ，a yj ，a zj Is unknown, t xj ，t yj ，t zj To be known:
adopting a nonlinear optimization method to obtain the final product at the initial value
For the rotation angle a xj ，a yj ，a zj Calculating a deviation derivative;
for is to
Taylor expansion is performed to obtain the angle of rotation a xj ，a yj ，a zj Correction amount da xj ，da yj ，da zj A system of linear equations of;
solving the linear equation set by a least square method to obtain a correction da xj ，da yj ，da zj ；
According to the correction amount da xj ，da yj ，da zj For the rotation angle a xj ，a yj ，a zj And (5) correcting:
The first case and the third case occur more frequently, and the second case is less frequent because it is difficult to acquire attitude data (rotation angle) with high accuracy.
S405: after the correction value is obtained, the correction value is madeAs a new translation vector t xj ，t yj ，t zj And/or angle of rotation a xj ，a yj ，a zj Continuously solving a new correction value according to the initial value; and repeating the iteration initial value and solving a new correction value until the iteration initial value is repeated to the specified times and/or the error of the initial value calculation of the two times of updating is less than the specified threshold value. The initial value and the correction value can be continuously updated in the measuring process according to the requirement until the measurement is finished.
The designated times are 50-100 times. The threshold is specified to be 0.001-0.01.
By adopting the scheme, the relative position and posture of each camera do not need to be accurately calibrated in advance, and the stability and the constant parameters of the system are ensured during use; the attitude sensor is not required to be fixedly connected with each camera, the control point target with accurately known coordinates is not required to be arranged in a measurement view field, the relative position attitude parameters among the cameras of the stereoscopic vision measurement system can be calibrated in real time only by simply scattering the bright spot irradiator, the irradiation angle of each bright spot, the relationship between the scattered bright spot irradiator and the stereoscopic vision camera and the like are not required to be known or calibrated, the stability of the scattered bright spot irradiator is not required to be maintained in the use process, the mutual relationship among the irradiation angles of the bright spots is not required to be maintained, and the relative relationship between the scattered bright spot irradiator and the stereoscopic vision camera is not required to be maintained, under the conditions of disturbance, change and the like of the parameters of the stereoscopic vision measurement system, the precision of the stereoscopic vision measurement is ensured, meanwhile, the method can adapt to the conditions that the surface has no stable texture, the environmental illumination condition is poor, the motion change of a measurement scene is caused, and the calibrated target points cannot be arranged in the region of the target to be measured.
As a third embodiment of the present invention, there is provided a self-calibrating measurement system comprising the apparatus of the first embodiment and a stereo vision measurement system. The stereo vision measurement system calibrates the first camera C according to the relative position attitude 0 And a second camera C j 。
As a fourth embodiment of the present invention, a method for measuring an object to be measured is provided, which employs the self-calibrated measurement system of the third embodiment.
The method comprises the following steps:
calibrating a stereoscopic vision camera of the vision measuring system by using the method of the second embodiment; the object 1 to be measured is measured using a stereo vision camera.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A calibration method for the relative position and attitude of a stereo vision measurement system is characterized by comprising the following steps:
s1: the stereovision measurement system is used for shooing the target that awaits measuring, and the stereovision measurement system includes m stereovision cameras, and m is the natural number more than or equal to 2, and m stereovision cameras include: a first camera and m-1 second cameras; shooting a target to be detected from different angles by m stereoscopic vision cameras; projecting n bright spots to a target to be detected, wherein the n bright spots are all in the shooting range of the stereoscopic vision camera; n is a natural number greater than or equal to 3;
s2: all stereoscopic vision cameras shoot a target image to be detected with n bright spots, image points corresponding to the n bright spots in the target image to be detected are extracted, and image points of a second camera and image points of a first camera are matched with image points of the second camera in a same name mode;
s3: calculating the normalized image coordinates of the image points of the stereoscopic vision camera;
s4: and respectively solving the relative position posture of each second camera and the first camera according to the image points with the same name and the normalized image coordinates of the image points of the first camera and the second camera.
2. The calibration method for the relative position and orientation of the stereo vision measurement system according to claim 1, wherein in step S3, the method for calculating the normalized image coordinates of the image point of the stereo vision camera comprises:
calculating the normalized image coordinates of the image points according to the internal parameters of the stereoscopic vision camera;
the internal parameters of the stereoscopic vision camera comprise principal point coordinates and equivalent focal length;
the image point normalized image coordinates of the first camera are:
the image point normalized image coordinates of the second camera are:
wherein the principal point coordinate of the first camera is (C x0 , C y0 ) The equivalent focal length of the first camera is (F x0 , F y0 ) The principal point coordinate of the second camera is (C xj , C yj ) The equivalent focal length of the second camera is: (F xj , F yj )，j=1,2,...,m-1；i=0,1，...，n-1。
3. The method for calibrating the relative position and orientation of the stereo vision measurement system of claim 1, wherein in step S4, the method for separately solving the relative position and orientation of each second camera with respect to the first camera according to the normalized image coordinates of the image point of the same name and the image points of the first camera and the second camera comprises:
setting an initial value of the relative position posture of the camera;
establishing a relative position attitude equation according to the relation between the first camera and the second camera;
listing a relative position attitude equation according to all the image points with the same name;
and solving a relative position attitude equation according to the initial value and the listed relative position attitude equation to obtain a corrected value.
4. The stereo vision measurement system relative position and orientation calibration method of claim 3, wherein the method for separately solving each second camera relative position and orientation with respect to the first camera based on the image coordinates of the same name image point and the normalized image coordinates of the image points of the first camera and the second camera further comprises: after the correction value is obtained, the correction value is used as a new initial value to continuously solve a new correction value; and repeating the iteration initial value and solving a new correction value until the iteration initial value is repeated to the specified times and/or the error of the initial value calculation of the two times of updating is less than the specified threshold value, or the measurement of the target to be measured is finished.
5. The stereo vision measurement system relative position and orientation calibration method according to claim 3, wherein the relative position and orientation equation is as follows:
the second camera and the first camera relative position pose comprises a translation vector and/or a rotation angle;
wherein the translation vector is
The rotation matrix is
At a rotation angle of
The rotation matrix is a trigonometric combination of rotation angles; x, y, z are mutually perpendicular axes, t xj 、t yj 、t zj Representing the length of movement of the camera in three axes, a zj 、a yj 、a xj The angle of the camera rotating around the three axes of z, y and x in turn, r 0j =cosa yj ×cosa zj 、r 1j =sina xj ×sina yj ×cosa zj -cosa xj ×sina zj 、r 2j =cosa xj ×sina yj ×cosa zj +sina xj ×sina xzj 、r 3j =cosa yj ×sina zj 、r 4j =sina xj ×sina yj ×sina zj +cosa xj ×cosa zj 、r 5j =cosa xj ×sina yj ×sina zj -sina xj ×cosa zj 、r 6j =-sina yj 、r 7j =sina xj ×cosa yj 、r 8j =cosa xj ×cosa yj 。
6. The stereo vision measurement system relative position and orientation calibration method of claim 5, wherein the method for solving the relative position and orientation equation according to the initial value and the listed relative position and orientation equation comprises:
adopting a nonlinear optimization method to obtain the final product at the initial value
Calculating a deviation of the translation vector and/or the rotation angle;
for is to
Performing Taylor expansion to obtain a linear equation set of correction quantity related to the translation vector and/or the rotation angle;
solving the linear equation set by a least square method to obtain a correction quantity;
and correcting the translation vector and/or the rotation angle according to the correction amount to obtain a correction value.
7. A method of measuring an object to be measured, characterized by calibrating a stereo vision camera of a stereo vision measurement system using the method of any one of claims 1-6;
and measuring the object to be measured by using a stereoscopic vision camera.
8. A relative position and posture calibration device for a stereo vision measurement system is characterized by comprising:
a scattered bright spot irradiator capable of irradiating n bright spots to a target to be measured, wherein n is a natural number greater than or equal to 3;
the homonymous image point matching module is used for extracting image points corresponding to the n bright points in the target image to be detected and respectively matching the image points of the second camera with the image points of the first camera;
the image coordinate calculation module is used for calculating the normalized image coordinate of the image point of the stereoscopic vision camera;
the relative position and posture calculation module is used for respectively solving the relative position and posture of each second camera and the first camera according to the image points with the same name and the normalized image coordinates of the image points of the first camera and the second camera;
wherein, the stereovision measurement system is used for shooing the target that awaits measuring, and the stereovision measurement system includes m stereovision cameras, and m is the natural number more than or equal to 2, and m stereovision cameras include: a first camera and m-1 second cameras; the m stereoscopic vision cameras shoot the target to be measured from different angles.
9. The stereo vision measurement system relative position and orientation calibration device of claim 8, wherein the dispersed bright spot irradiator is a laser.
10. A self-calibrating measurement system, comprising:
the apparatus of claim 8 or 9 and the stereo vision measurement system.
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