CN107492126A - Calibration method, device, system, medium and the equipment of camera central shaft - Google Patents
Calibration method, device, system, medium and the equipment of camera central shaft Download PDFInfo
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- CN107492126A CN107492126A CN201710656599.8A CN201710656599A CN107492126A CN 107492126 A CN107492126 A CN 107492126A CN 201710656599 A CN201710656599 A CN 201710656599A CN 107492126 A CN107492126 A CN 107492126A
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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
Abstract
The application is related to technical field of information processing, discloses calibration method, device, system, medium and the equipment of camera central shaft.This method includes：The image of the scaling board is obtained by scaling board of the camera shooting containing multiple reference points；Obtain the image coordinate of each reference point in image；And, according to the default mathematics transformation model for being used to characterize the mapping relations of world coordinates and image coordinate, determine image coordinate corresponding to the reference point on scaling board, based on non-linear optimization method and mathematics transformation model, the coordinate of central shaft is as calibration value when the result of goal-selling function is optimal, according to the central shaft of calibration value calibration camera.The embodiment of the present application does not require that shooting angle without the capture apparatus of specialty, what it is due to goal-selling function sign is calibration accuracy, so the calibration value determined is more accurate.Calibration result meets to require.So the embodiment of the present application provides a kind of low cost, easy implementation and the high scheme of calibration accuracy.
Description
Technical field
The application is related to technical field of information processing, more particularly to the calibration method of camera central shaft, device, system,
Medium and equipment.
Background technology
Camera is indispensable part in wisdom life.It provides various facilities for security protection.Safety is people
It is basic to pursue, as the improvement of people's living standards, awareness of safety also more and more higher.It is higher level, wider scope safety into
Constantly pursued for people.
For example, in field of automobile safety, many users are provided with more from traffic safety to safe, parking safety etc. of parking
The awareness of safety of aspect.With the development of Chinese Automobile Industry ', the gradual maturation in auto navigation market, user also increasingly pursues
Conveniently, safely, use.Nowadays panoramic looking-around system has turned into the standard configuration on automobile gradually.Panoramic looking-around system passes through
Multichannel ultra wide-angle imaging head image is gathered, vehicle periphery full-view image is formed and understands motor vehicle environment situation all over user.
In the prior art, it is necessary to distortion correction be carried out to ultra wide-angle imaging head, if camera central shaft inaccuracy will be led
Cause panoramic looking-around image can not accurately by the image mosaic of collection together.Therefore panoramic looking-around system is to ultra wide-angle imaging head
Central shaft requirement it is stricter, camera produce during, it is necessary to strictly control camera central shaft.
Prior art calibration method generally comprises following two：
1) go to detect the central shaft of camera to be measured using the central shaft detecting instrument of specialty.Due to the center repacking of specialty
It is expensive to survey instrument price, this will increase production cost.
2) camera to be tested is fixed, the vertical target of fixed placement immediately ahead of camera, calculates camera to be measured
Picture centre and the range difference at target surface center, so as to calculate the position of camera central shaft.If the angle that camera to be measured is put
Degree slightly deviation, then influenceed on the testing result of central shaft huge.
3), such as in number of patent application 201410181871.8 " camera distortion central point test device and recognition methods ",
It is required that the optical axis of camera to be measured must be less than 5 degree with the deviation angle of demarcation target surface.But by mounting process when producing camera
Influenceing deviation angle can not be effectively controlled and can not meet the condition, so realizing difficult.
In summary, it is necessary to a kind of central shaft calibration program of camera inexpensive, easily implementing, precision is higher.
The content of the invention
The embodiment of the present application provides calibration method, device, system, medium and the equipment of camera central shaft, to solve
The problem of center axis calibration being in the prior art present either cost be high, be either difficult to carry out or precision is low etc..
The embodiment of the present application provides a kind of calibration method of camera central shaft, including：
The image of the scaling board is obtained by scaling board of the camera shooting containing multiple reference points；
Described image is detected, obtains the image coordinate of each reference point in image；And
According to world coordinate system and the transformational relation of camera coordinate system, each reference point on scaling board is sat in the world
World coordinates in mark system is converted to the shooting coordinate in camera coordinate system, and, it is used to characterize world coordinates according to default
With the mathematics transformation model of the mapping relations of image coordinate, image coordinate corresponding to the reference point on scaling board is determined, wherein, institute
State the shooting coordinate of the image coordinate of the central shaft comprising camera and the reference point of scaling board in mathematics transformation model；
Based on non-linear optimization method and the mathematics transformation model, by the result of goal-selling function it is optimal when described in
The coordinate of central shaft as calibration value, wherein, goal-selling function be used for phenogram picture in reference point and scaling board reference
The image coordinate gap of point, described image coordinate difference is away from minimum, or described image when the result of the goal-selling function is optimal
Coordinate difference is away from less than preset value；
According to the central shaft of camera described in the calibration value calibration.
On the other hand, the embodiment of the present application provides a kind of calibrating installation of camera central shaft, and the device includes：
Image collection module, for obtaining the scaling board by scaling board of the camera shooting containing multiple reference points
Image；
First image coordinate determining module, for detecting described image, obtain the image coordinate of each reference point in image；
Second image coordinate determining module, for the transformational relation according to world coordinate system and camera coordinate system, it will mark
World coordinates of each reference point in world coordinate system on fixed board is converted to the shooting coordinate in camera coordinate system, and,
According to the default mathematics transformation model for being used to characterize the mapping relations of world coordinates and image coordinate, the ginseng on scaling board is determined
Image coordinate corresponding to examination point, wherein, the image coordinate and mark of the central shaft comprising camera in the mathematics transformation model
The shooting coordinate of the reference point of fixed board；
Calibration value determining module, for based on non-linear optimization method and the mathematics transformation model, by goal-selling
The coordinate of the central shaft is as calibration value when the result of function is optimal, wherein, goal-selling function is used for phenogram as in
The image coordinate gap of reference point and the reference point of scaling board, described image coordinate when the result of the goal-selling function is optimal
Gap is minimum, or described image coordinate difference is away from less than preset value；
Calibration module, the central shaft for the camera according to the calibration value calibration.
Another further aspect, the embodiment of the present application provide a kind of calibration system of camera central shaft, and the system includes：
Scaling board, include multiple reference points；
Camera, the image of the scaling board is obtained for shooting the scaling board containing multiple reference points, and be sent to processing
Device；
Fixing device, for fixing the scaling board and camera；
Processor, for detecting described image, obtain the image coordinate of each reference point in image；And sat according to the world
Mark system and the transformational relation of camera coordinate system, world coordinates of each reference point in world coordinate system on scaling board is turned
The shooting coordinate being changed in camera coordinate system, and, closed according to the default mapping for being used to characterize world coordinates and image coordinate
The mathematics transformation model of system, determines image coordinate corresponding to the reference point on scaling board, wherein, wrapped in the mathematics transformation model
The shooting coordinate of the image coordinate of central shaft containing camera and the reference point of scaling board；Based on non-linear optimization method and
The mathematics transformation model, when the result of goal-selling function is optimal the coordinate of the central shaft as calibration value, wherein, in advance
If reference point and the image coordinate gap of the reference point of scaling board that object function is used in phenogram picture, the goal-selling letter
Described image coordinate difference is away from minimum when several results is optimal, or described image coordinate difference is away from less than preset value；According to the calibration
The central shaft of camera described in value calibration.
Another aspect, the embodiment of the present application provide a kind of computing device, including memory, processor and are stored in described
In memory and the computer program that can run on the processor, it is characterised in that calculating described in the computing device
The step of the embodiment of the present application methods described is realized during machine program.
In addition, the embodiment of the present application also provides a kind of computer-readable recording medium, the computer-readable recording medium
It is stored with computer program, it is characterised in that realized when the computer program is executed by processor such as the embodiment of the present application institute
The step of stating method.
In the embodiment of the present application, by goal-selling function it is constraints in the application, scaling board is shot i.e.
Calibration value can be obtained to be calibrated.The embodiment of the present application do not required shooting angle, without the capture apparatus of specialty, due to
What goal-selling function characterized is calibration accuracy, so the calibration value determined is more accurate.Calibration result meets to require.So
The embodiment of the present application provides a kind of low cost, easy implementation and the high scheme of calibration accuracy.
Brief description of the drawings
Fig. 1 is the structural representation for the scaling board that the embodiment of the present application provides；
Fig. 2 is the calibration method flow chart for the camera central shaft that the embodiment of the present application one provides；
Fig. 3 is the structural representation of the calibration system for the camera central shaft that the embodiment of the present application two provides；
Fig. 4 is the structural representation of the calibrating installation for the camera central shaft that the embodiment of the present application three provides；
Fig. 5 is the structural representation for the computing device that the embodiment of the present application three provides.
Embodiment
In the embodiment of the present application, the image of scaling board acquisition scaling board is shot by camera first, is had on the scaling board
There are multiple reference points to be used for the central shaft for calibrating camera.Such as shown in Fig. 1, for the schematic diagram of the scaling board.Wherein, four squares
The public angle point of shape is reference point.Then, by detecting reference point, and world coordinate system, camera coordinate system and image
Relation between coordinate system, obtains the reference point of the scaling board of reference point, and the reference point of the scaling board is used on theory of representation join
The image coordinate of examination point.Then, based on non-linear optimization method and the mathematics transformation model, by the knot of goal-selling function
The coordinate of the central shaft is calibration value when fruit is optimal, is calibrated.Wherein, goal-selling function is used to characterize reference point and its
The image coordinate gap of the reference point of scaling board, described image coordinate difference is away from most when the result of the goal-selling function is optimal
It is small, or described image coordinate difference is away from less than preset value.
So, it is constraints by goal-selling function in the application, calibration can be obtained by carrying out shooting to scaling board
Value is calibrated.The embodiment of the present application is not required shooting angle, without the capture apparatus of specialty, due to goal-selling letter
What number characterized is calibration accuracy, so the calibration value determined is more accurate.Calibration result meets to require.So the application is implemented
Example provides a kind of low cost, easy implementation and the high scheme of calibration accuracy.
The embodiment of the present application is described in further detail with reference to Figure of description.
Embodiment one
As shown in Fig. 2 the flow chart of the calibration method of the camera central shaft provided for the embodiment of the present application one, including with
Lower step：
Step 201：The image of the scaling board is obtained by scaling board of the camera shooting containing multiple reference points.
When it is implemented, as shown in figure 1, the scaling board for etc. big dark rectangular and light rectangle be alternately arranged composition
Chessboard；The reference point is the public angle point of four adjacent rectangles.Certainly, it is necessary to which explanation, Fig. 1 are merely to illustrate mark
Fixed board is not used to limit.The scaling board of so chequered with black and white lineament, it is easy to detect when detecting reference point.Pass through bat
Take the photograph a scaling board and can determine that calibration value, simple to operate, processing facilitates quickly, and stability and practicality are also higher.
Step 201：The image of the scaling board is obtained by scaling board of the camera shooting containing multiple reference points.
Step 202：Described image is detected, obtains the image coordinate of each reference point in image.
Step 203：According to world coordinate system and the transformational relation of camera coordinate system, by each reference point on scaling board
World coordinates in world coordinate system is converted to the shooting coordinate in camera coordinate system, and, it is used to characterize according to default
The mathematics transformation model of the mapping relations of world coordinates and image coordinate, determine that image corresponding to the reference point on scaling board is sat
Mark, wherein, the image coordinate of the central shaft comprising camera and the reference point of scaling board are taken the photograph in the mathematics transformation model
As coordinate.
Wherein, the execution sequencing of step 202 and step 203 is unrestricted.
Step 204：Based on non-linear optimization method and the mathematics transformation model, by the result of goal-selling function most
The coordinate of the central shaft is as calibration value when excellent, wherein, the reference point and demarcation that goal-selling function is used in phenogram picture
The image coordinate gap of the reference point of plate, when the result of the goal-selling function is optimal described image coordinate difference away from minimum, or
Described image coordinate difference is away from less than preset value.
Step 205：According to the central shaft of camera described in the calibration value calibration.
Wherein, in one embodiment, the mathematics transformation model be the radial distortion based on camera, tangential distortion,
What the coordinate of prismatic distortion and central shaft was established.
When it is implemented, the transformational relation of the world coordinate system and camera coordinate system such as formula (1)：
P=MO；M=[R | T],(1)
In formula (1), P is shooting coordinate；O is world coordinates；M is projection matrix；R is spin matrix；T is to be translated towards
Amount；Refer to matrix.
The mathematics transformation model such as formula (2) is：
xc=XC/ZC；yc=TC/ZC
Wherein, u, v are the image coordinate of the reference point of scaling board；k1、k2、k3、k4、k5、k6It is radial distortion parameter；
p1、p2It is tangential distortion parameter；s1、s2、s3、s4It is prismatic distortion parameter；fx、fy、u0、v0For camera inner parameter, its
Middle fxFor camera focal length in the direction of the x axis and the ratio of imaging sensor size, fyFor the Jiao of camera in the y-axis direction
Away from the ratio with imaging sensor size, u0And v0Centered on axle image coordinate；XC、YC、ZCTaken the photograph for the reference point of scaling board
As coordinate；R be scaling board reference point world coordinates be converted to shooting coordinate after, reference point to camera coordinate system origin
Distance.
Further, the preset target function such as formula (3) is shown：
In formula (4), ε is preset target function；djSat to preset the image for the reference point that call number is j in image
Mark；d′jTo preset the image coordinate for the reference point that call number is j in scaling board；M is reference point sum.That is, m is scaling board
Or in image reference point sum.
Wherein, in one embodiment, for ease of realizing and obtain the higher calibration value of accuracy, the non-linear optimizing
Method is light velocity adjustment method.When it is implemented, in order to obtain the high calibration value of reliability as soon as possible, it is described to be sought based on non-linear
Excellent method and the mathematics transformation model, it is calibration by the coordinate of the result of goal-selling function central shaft when optimal
Value, may particularly include：
Step A1：Initialize mathematics transformation model in camera lens inner parameter, projection matrix, distortion parameter and step-length across
L is spent, wherein, distortion parameter includes tangential distortion parameter, radial distortion parameter, prismatic distortion parameter；
Step A2：The image coordinate of each reference point in scaling board is calculated to central shaft and the partial derivative matrix of projection matrix
J；
Wherein, shown in partial derivative matrix equation below (4)：Wherein, m is reference point sum.
Step A3：According to formula H=JTH is calculated in J, and determines step-length λ according to formula λ=max (diag (H)), its
In, the element on diag representing matrix diagonal；
Step A4：Scaling board is calculated according to mathematics transformation model, and camera lens inner parameter, projection matrix, distortion parameter
Reference point image coordinate, and calculate the functional value ε of goal-selling function；
Step A5：According to formula (JTJ+ λ I) σ=- JTε determines that σ values are used as current σ values, wherein, I is unit matrix；
Step A6：According to current σ values, the image coordinate of the central shaft in mathematics transformation model is updated to last determination
The image coordinate of central shaft add σ, and update each parameter in projection matrix and add σ for current each parameter in the matrix；
When it is implemented, σ, v is added to add σ u in the image coordinate of central shaft.Each parameter adds σ similarly to will not be repeated here.
Wherein, when step A6 is performed first, last center axial coordinate is the result initialized in step A1.
Step A7：It is determined that the magnitude relationship of current σ values and the σ values of last computation；
If both are equal, it is determined that the image coordinate of the central shaft of last computation is calibration value；
If current σ values are less than the σ values of last computation, return and perform step A6；
If current σ values are more than the σ values of last computation, renewal step-length is L* λ, and returns and perform step A4.
Embodiment two
Based on same inventive concept, the embodiment of the present application also provides a kind of calibration system of camera central shaft, due to this
The principle that system solves problem is similar to the calibration method of the camera central shaft described in the embodiment of the present application, therefore the system
Implementation may refer to the implementation of method, repeat part and repeat no more.As shown in figure 3, the system includes：
Scaling board 301, include multiple reference points；
Camera 302, the image of the scaling board is obtained for shooting the scaling board containing multiple reference points, and be sent to place
Manage device；
Fixing device 303, for fixing the scaling board and camera；
Processor 304, for detecting described image, obtain the image coordinate of each reference point in image；And according to the world
The transformational relation of coordinate system and camera coordinate system, by world coordinates of each reference point in world coordinate system on scaling board
The shooting coordinate in camera coordinate system is converted to, and, according to the default mapping for being used to characterize world coordinates and image coordinate
The mathematics transformation model of relation, determines image coordinate corresponding to the reference point on scaling board, wherein, in the mathematics transformation model
The shooting coordinate of the image coordinate of central shaft comprising camera and the reference point of scaling board；Based on non-linear optimization method with
And the mathematics transformation model, when the result of goal-selling function is optimal the coordinate of the central shaft as calibration value, wherein,
The reference point and the image coordinate gap of the reference point of scaling board that goal-selling function is used in phenogram picture, the goal-selling
Described image coordinate difference is away from minimum when the result of function is optimal, or described image coordinate difference is away from less than preset value；According to the school
The central shaft of camera described in quasi- value calibration.
Wherein, can be communicated between processor and camera by wirelessly or non-wirelessly communication mode.
Embodiment three
Similarly, based on same inventive concept, a kind of calibration cartridge of camera central shaft is additionally provided in the embodiment of the present application
Put, because the principle of device solution problem is similar to the calibration method of the camera central shaft described in the embodiment of the present application,
Therefore the implementation of the device may refer to the implementation of method, repeats part and repeats no more.
As shown in figure 4, the structure drawing of device provided for the embodiment of the present application three, including：
Image collection module 401, for obtaining the mark by scaling board of the camera shooting containing multiple reference points
The image of fixed board；
First image coordinate determining module 402, for detecting described image, the image for obtaining each reference point in image is sat
Mark；
Second image coordinate determining module 403, will for the transformational relation according to world coordinate system and camera coordinate system
World coordinates of each reference point in world coordinate system on scaling board is converted to the shooting coordinate in camera coordinate system,
And according to the default mathematics transformation model for being used to characterize the mapping relations of world coordinates and image coordinate, determine on scaling board
Reference point corresponding to image coordinate, wherein, in the mathematics transformation model comprising camera central shaft image coordinate with
And the shooting coordinate of the reference point of scaling board；
Calibration value determining module 404, for based on non-linear optimization method and the mathematics transformation model, by default mesh
The coordinate of the central shaft is as calibration value when the result of scalar functions is optimal, wherein, goal-selling function is used in phenogram picture
Reference point and scaling board reference point image coordinate gap, when the result of the goal-selling function is optimal described image sit
It is minimum to mark gap, or described image coordinate difference is away from less than preset value；
Calibration module 405, the central shaft for the camera according to the calibration value calibration.
Further, the non-linear optimization method is light velocity adjustment method.
Further, the transformational relation of the world coordinate system and camera coordinate system is：
P=MO；M=[R | T],
Wherein, P is shooting coordinate；O is world coordinates；M is projection matrix；R is spin matrix；T is translation vector；Table
Show matrix；
The mathematics transformation model is：
xc=XC/ZC；yc=YC/ZC
Wherein, u, v are the image coordinate of the reference point of scaling board；k1、k2、k3、k4、k5、k6It is radial distortion parameter；
p1、p2It is tangential distortion parameter；s1、s2、s3、s4It is prismatic distortion parameter；fx、fy、u0、v0For camera inner parameter, its
Middle fxFor camera focal length in the direction of the x axis and the ratio of imaging sensor size, fyFor the Jiao of camera in the y-axis direction
Away from the ratio with imaging sensor size, u0And v0Centered on axle image coordinate；XC、YC、ZCTaken the photograph for the reference point of scaling board
As coordinate；R be scaling board reference point world coordinates be converted to shooting coordinate after, reference point to camera coordinate system origin
Distance.
Further, it is described to be based on non-linear optimization method and the mathematics transformation model, by goal-selling function
As a result the coordinate of the central shaft specifically includes as calibration value when optimal：
Camera lens inner parameter, projection matrix, distortion parameter and the step-length span L in mathematics transformation model are initialized, its
In, distortion parameter includes tangential distortion parameter, radial distortion parameter, prismatic distortion parameter；
The image coordinate of each reference point in scaling board is calculated to central shaft and the partial derivative matrix J of projection matrix；
According to formula H=JTH is calculated in J, and determines step-length λ according to formula λ=max (diag (H)), wherein, diag
Element on representing matrix diagonal；
The reference point of scaling board is calculated according to mathematics transformation model, and camera lens inner parameter, projection matrix, distortion parameter
Image coordinate, and calculate the functional value ε of goal-selling function；
According to formula (JTJ+ λ I) σ=- JTε determines that σ values are used as current σ values, wherein, I is unit matrix；
According to current σ values, the image coordinate of the central shaft in mathematics transformation model is updated to the last center determined
The image coordinate of axle adds σ, and updates each parameter in projection matrix and add σ for current each parameter in the matrix；
It is determined that the magnitude relationship of current σ values and the σ values of last computation；
If both are equal, it is determined that the image coordinate of the central shaft of last computation is calibration value；
If current σ values are less than the σ values of last computation, return and perform according to current σ values, in mathematics transformation model
The image coordinate that the image coordinate of mandrel is updated to the central shaft of last determination adds σ, and updates each parameter in projection matrix
The step of adding σ for current each parameter in the matrix；
If current σ values are more than the σ values of last computation, the functional value ε of renewal goal-selling function is the letter of last computation
Numerical value, renewal step-length are L* λ, and return to execution according to mathematics transformation model, and camera lens inner parameter, projection matrix, distortion
Parameter calculates the image coordinate of the reference point of scaling board, and the step of calculate the functional value ε of goal-selling function.
Further, the preset target function is：
Wherein, ε is preset target function；djTo preset the image coordinate for the reference point that call number is j in image；d′jFor mark
The image coordinate for the reference point that call number is j is preset in fixed board；M is reference point sum.
Further, the scaling board for etc. big dark rectangular and light rectangle be alternately arranged the chessboard of composition；It is described
Reference point is the public angle point of four adjacent rectangles.
Example IV
The embodiment of the present application three additionally provides a kind of computing device, and the computing device is specifically as follows desktop computer, just
Take formula computer, smart mobile phone, tablet personal computer, personal digital assistant (Personal Digital Assistant, PDA) etc..
As shown in figure 5, the computing device can include central processing unit (Center Processing Unit, CPU) 501, memory
502nd, input equipment 503, output equipment 504 etc., input equipment can include keyboard, mouse, touch-screen etc., and output equipment can be with
Including display device, such as liquid crystal display (Liquid Crystal Display, LCD), cathode-ray tube (Cathode Ray
Tube, CRT) etc..
Memory can include read-only storage (ROM) and random access memory (RAM), and provide storage to processor
The programmed instruction and data stored in device.In the embodiment of the present application, memory can be used for the displaying side for storing info web
The programmed instruction of method.For processor by calling the programmed instruction of memory storage, processor is used for the programmed instruction according to acquisition
Perform：The image of the scaling board is obtained by scaling board of the camera shooting containing multiple reference points；
Described image is detected, obtains the image coordinate of each reference point in image；And
According to world coordinate system and the transformational relation of camera coordinate system, each reference point on scaling board is sat in the world
World coordinates in mark system is converted to the shooting coordinate in camera coordinate system, and, it is used to characterize world coordinates according to default
With the mathematics transformation model of the mapping relations of image coordinate, image coordinate corresponding to the reference point on scaling board is determined, wherein, institute
State the shooting coordinate of the image coordinate of the central shaft comprising camera and the reference point of scaling board in mathematics transformation model；
Based on non-linear optimization method and the mathematics transformation model, by the result of goal-selling function it is optimal when described in
The coordinate of central shaft as calibration value, wherein, goal-selling function be used for phenogram picture in reference point and scaling board reference
The image coordinate gap of point, described image coordinate difference is away from minimum, or described image when the result of the goal-selling function is optimal
Coordinate difference is away from less than preset value；
According to the central shaft of camera described in the calibration value calibration.
Embodiment five
The embodiment of the present application five provides a kind of computer-readable storage medium, by saving as based on used in above-mentioned computing device
Calculation machine programmed instruction, it includes the program for the methods of exhibiting for being used to perform above-mentioned info web.
The computer-readable storage medium can be any usable medium or data storage device that computer can access, bag
Include but be not limited to magnetic storage (such as floppy disk, hard disk, tape, magneto-optic disk (MO) etc.), optical memory (such as CD, DVD,
BD, HVD etc.) and semiconductor memory (such as it is ROM, EPROM, EEPROM, nonvolatile memory (NAND FLASH), solid
State hard disk (SSD)) etc..
Finally it should be noted that：Above example is only to illustrate the technical scheme of the application, rather than its limitations；Although
The application is described in detail with reference to the foregoing embodiments, it will be understood by those within the art that：It still may be used
To be modified to the technical scheme described in foregoing embodiments, or equivalent substitution is carried out to which part technical characteristic；
And these modification or replace, do not make appropriate technical solution essence depart from each embodiment technical scheme of the application spirit and
Scope.
Claims (10)
1. a kind of calibration method of camera central shaft, it is characterised in that this method includes：
The image of the scaling board is obtained by scaling board of the camera shooting containing multiple reference points；
Described image is detected, obtains the image coordinate of each reference point in image；And
According to world coordinate system and the transformational relation of camera coordinate system, by each reference point on scaling board in world coordinate system
In world coordinates be converted to shooting coordinate in camera coordinate system, and, be used to characterize world coordinates and figure according to default
As the mathematics transformation model of the mapping relations of coordinate, image coordinate corresponding to the reference point on scaling board is determined, wherein, the number
Learn the shooting coordinate of the image coordinate of the central shaft comprising camera and the reference point of scaling board in transformation model；
Based on non-linear optimization method and the mathematics transformation model, by the result of goal-selling function it is optimal when the center
The coordinate of axle as calibration value, wherein, the reference point and the reference point of scaling board that goal-selling function is used in phenogram picture
Image coordinate gap, described image coordinate difference is away from minimum, or described image coordinate when the result of the goal-selling function is optimal
Gap is less than preset value；
According to the central shaft of camera described in the calibration value calibration.
2. according to the method for claim 1, it is characterised in that the non-linear optimization method is light velocity adjustment method.
3. method according to claim 1 or 2, it is characterised in that
The transformational relation of the world coordinate system and camera coordinate system is：
Wherein, P is shooting coordinate；O is world coordinates；M is projection matrix；R is spin matrix；T is translation vector；Represent square
Battle array；
The mathematics transformation model is：
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xc=XC/ZC；yc=YC/ZC
Wherein, u, v are the image coordinate of the reference point of scaling board；k1、k2、k3、k4、k5、k6It is radial distortion parameter；p1、p2
For tangential distortion parameter；s1、s2、s3、s4It is prismatic distortion parameter；fx、fy、u0、v0For camera inner parameter, wherein fxFor
The ratio of camera focal length in the direction of the x axis and imaging sensor size, fyFor the focal length of camera in the y-axis direction with into
As the ratio of size sensor, u0And v0Centered on axle image coordinate；XC、YC、ZCFor the shooting coordinate of the reference point of scaling board；
R be scaling board reference point world coordinates be converted to shooting coordinate after, the distance of reference point to camera coordinate system origin.
4. according to the method for claim 3, it is characterised in that described to be turned based on non-linear optimization method and the mathematics
Mold changing type, the coordinate of the central shaft specifically includes as calibration value when the result of goal-selling function is optimal：
Camera lens inner parameter, projection matrix, distortion parameter and the step-length span L in mathematics transformation model are initialized, wherein, it is abnormal
Variable element includes tangential distortion parameter, radial distortion parameter, prismatic distortion parameter；
The image coordinate of each reference point in scaling board is calculated to central shaft and the partial derivative matrix J of projection matrix；
According to formula H=JTH is calculated in J, and determines step-length λ according to formula λ=max (diag (H)), wherein, diag represents square
Element on battle array diagonal；
The figure of the reference point of scaling board is calculated according to mathematics transformation model, and camera lens inner parameter, projection matrix, distortion parameter
As coordinate, and calculate the functional value ε of goal-selling function；
According to formula (JTJ+ λ I) σ=- JTε determines that σ values are used as current σ values, wherein, I is unit matrix；
According to current σ values, the image coordinate of the central shaft in mathematics transformation model is updated to the central shaft of last determination
Image coordinate adds σ, and updates each parameter in projection matrix and add σ for current each parameter in the matrix；
It is determined that the magnitude relationship of current σ values and the σ values of last computation；
If both are equal, it is determined that the image coordinate of the central shaft of last computation is calibration value；
If current σ values are less than the σ values of last computation, return and perform according to current σ values, by the central shaft in mathematics transformation model
The image coordinate of the image coordinate central shaft that is updated to last determination add σ, and update each parameter in projection matrix for should
The step of current each parameter in matrix adds σ；
If current σ values are more than the σ values of last computation, the functional value ε of renewal goal-selling function is the functional value of last computation,
Renewal step-length is L* λ, and returns to execution according to mathematics transformation model, and camera lens inner parameter, projection matrix, distortion parameter meter
The step of calculating the image coordinate of the reference point of scaling board, and calculating the functional value ε of goal-selling function.
5. according to the method for claim 1, it is characterised in that the preset target function is：
<mrow>
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<mrow>
<mi>j</mi>
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<mo>&prime;</mo>
</msubsup>
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<mo>|</mo>
<mn>2</mn>
</msup>
</mrow>
Wherein, ε is preset target function；djTo preset the image coordinate for the reference point that call number is j in image；dj' it is scaling board
In preset call number be j reference point image coordinate；M is reference point sum.
6. according to the method for claim 1, it is characterised in that
The scaling board for etc. big dark rectangular and light rectangle be alternately arranged the chessboard of composition；The reference point is adjacent
The public angle point of four rectangles.
7. a kind of calibrating installation of camera central shaft, it is characterised in that the device includes：
Image collection module, for obtaining the figure of the scaling board by scaling board of the camera shooting containing multiple reference points
Picture；
First image coordinate determining module, for detecting described image, obtain the image coordinate of each reference point in image；
Second image coordinate determining module, for the transformational relation according to world coordinate system and camera coordinate system, by scaling board
On world coordinates of each reference point in world coordinate system be converted to shooting coordinate in camera coordinate system, and, according to
The default mathematics transformation model for being used to characterize the mapping relations of world coordinates and image coordinate, determines the reference point on scaling board
Corresponding image coordinate, wherein, the image coordinate and scaling board of the central shaft comprising camera in the mathematics transformation model
Reference point shooting coordinate；
Calibration value determining module, for based on non-linear optimization method and the mathematics transformation model, by goal-selling function
Result it is optimal when the central shaft coordinate as calibration value, wherein, goal-selling function be used for phenogram picture in reference
Point and scaling board reference point image coordinate gap, when the result of the goal-selling function is optimal described image coordinate difference away from
Minimum, or described image coordinate difference is away from less than preset value；
Calibration module, the central shaft for the camera according to the calibration value calibration.
8. a kind of calibration system of camera central shaft, it is characterised in that the system includes：
Scaling board, include multiple reference points；
Camera, the image of the scaling board is obtained for shooting the scaling board containing multiple reference points, and be sent to processor；
Fixing device, for fixing the scaling board and camera；
Processor, for detecting described image, obtain the image coordinate of each reference point in image；And according to world coordinate system
With the transformational relation of camera coordinate system, world coordinates of each reference point in world coordinate system on scaling board is converted to
Shooting coordinate in camera coordinate system, and, according to the default mapping relations for being used to characterize world coordinates and image coordinate
Mathematics transformation model, image coordinate corresponding to the reference point on scaling board is determined, wherein, include and take the photograph in the mathematics transformation model
As the central shaft of head image coordinate and scaling board reference point shooting coordinate；Based on non-linear optimization method and described
Mathematics transformation model, when the result of goal-selling function is optimal the coordinate of the central shaft as calibration value, wherein, preset mesh
The reference point and the image coordinate gap of the reference point of scaling board that scalar functions are used in phenogram picture, the goal-selling function
As a result described image coordinate difference is away from minimum when optimal, or described image coordinate difference is away from less than preset value；According to the calibration value school
The central shaft of the accurate camera.
9. a kind of computing device, including memory, processor and it is stored in the memory and can be on the processor
The computer program of operation, it is characterised in that realize that claim 1-6 such as appoints described in the computing device during computer program
The step of one methods described.
10. a kind of computer-readable recording medium, the computer-readable recording medium storage has computer program, and its feature exists
In being realized when the computer program is executed by processor such as the step of claim 1-6 any methods describeds.
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