CN112697112A - Method and device for measuring horizontal plane inclination angle of camera - Google Patents
Method and device for measuring horizontal plane inclination angle of camera Download PDFInfo
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Abstract
A method and a device for measuring the horizontal plane inclination angle of a camera belong to the field of precision measurement and image processing. The invention controls the movement of the working platform through the motor, so that the calibration board graph enters the visual field of the camera, simultaneously adjusts the proper position of the calibration board graph in the visual field of the camera, shoots an image of one calibration board graph, then keeps the Y axis of the motor still, moves a certain step length along the X axis of the motor, shoots an image of the other calibration board graph, and because the camera is arranged on the horizontal plane, the coordinate values of the common area points in the two calibration board graph images are different, and the two shot images are processed, so that the inclination angle of the camera on the horizontal plane can be obtained. The method has the advantages that the pattern manufacturing precision of the calibration plate is high, the control precision of the motion of the working platform is also high, the calibration precision of the horizontal plane inclination angle of the camera is high, the step size can be changed according to the calibration of different camera views and different motion ranges, and the method has strong adaptability.
Description
Technical Field
The invention belongs to the field of precision measurement and image processing, and relates to a method and a device for measuring a horizontal plane inclination angle of a camera.
Background
In industrial production application, assembly accuracy is an important index for measuring an automatic assembly technology, and calibration of a visual unit in an automatic assembly system has very important significance on the assembly accuracy and is of great importance on accurate positioning of products and reduction of assembly errors.
At present, the calibration of a visual unit in an automatic assembly system mainly comprises monocular and monocular calibration of a camera and pose calibration of the camera and a manipulator. The monocular and monocular calibration of the camera is mainly used for acquiring internal and external parameters of the camera, so that the parameters are used for size measurement, three-dimensional reconstruction and the like of an object, and the pose calibration of the camera and the manipulator is mainly used for establishing a relation between a terminal coordinate system of a camera motion mechanism and a terminal coordinate system of the manipulator, so that the pose calibration is used for identification, positioning and the like of the object.
However, after the camera is installed, the installation process of the camera may cause the camera to incline in a vertical plane and a horizontal plane, and when the camera has an inclined angle in the vertical plane, due to the limited depth of field of the camera, the acquired image may have a situation of being partly clear and partly blurred, which may greatly affect the accuracy of the result. The method comprises the steps of manufacturing a high-precision camera calibration plate, moving a camera driving mechanism to enable a calibration graph on the calibration plate to enter a camera visual field, moving a camera with a certain step length along an axis of camera motion, and shooting the calibration graph on the calibration plate, wherein due to the fact that an inclination angle exists in the vertical plane of the camera, the definition of graphs at the upper left corner, the upper right corner, the lower right corner and the lower left corner in the camera visual field is different, and the shot images are processed to obtain the vertical plane inclination angle of the camera [ a method for measuring the inclination angle of the camera, 2019, application number 201910004492.4 ].
When the camera has an inclination angle on the horizontal plane, especially for positioning and measuring a large-sized object, image stitching or coordinate transformation is generally required, and the inclination angle on the horizontal plane of the camera causes stitching or transformation errors, so that an accurate result cannot be obtained. There is currently no effective method for measuring and calibrating the tilt angle of the camera's horizontal plane.
Disclosure of Invention
In order to solve the existing problems, the invention provides a method for measuring the horizontal plane inclination angle of a camera, which realizes the system angle measurement of two different planes of different planes, and obtains the horizontal plane inclination angle of the camera by calculating the coordinate difference of the common area point of a calibration plate in the images of the two calibration plates.
The technical scheme of the invention is as follows:
a device for measuring the horizontal plane inclination angle of a camera comprises a working platform, a motor Y axis, a calibration plate, a motor X axis, a calibration plate carrying platform, a light source, a lens, a camera, a support base and a camera support;
the camera comprises a light source, a camera support, a support base and a camera, wherein the light source is arranged on the camera, the camera is fixedly arranged on the camera support, and the camera support is fixedly connected with the support base; the calibration device comprises a light source, a calibration board carrying platform, a motor Y shaft, a motor X shaft, a motor Y shaft, a calibration board carrying platform and a motor Y shaft, wherein the light source is arranged below the calibration board carrying platform.
A method for measuring the horizontal plane inclination angle of a camera comprises the following steps:
Preferably, the pattern on the calibration board is circular, the radius of the standard circle is r1, two positioning circles with the radius of r2 exist on the calibration board, the positioning circles are in different columns, the area between the columns where the positioning circles are located is a common area of the calibration board, the point of the common area is the center of a circle in the common area, and r2> r 1.
Preferably, in the step 1, the public area of the calibration plate is moved to the right side of the camera view field, and the shot calibration plate image is marked as a Left image; and (3) keeping the Y axis of the motor still in the step (2), moving the working platform by delta d step length along the negative direction of the X axis of the motor or leftwards, so that the public area of the calibration plate is moved to the left side of the visual field of the camera, and recording the shot image of the calibration plate as a Right image.
Further preferably, in the Left image, the center a of the circle in the common area is (U)l,Vl) (ii) a When the working platform moves delta d step length along the negative direction of the X axis of the motor, the circle center A in the original public area is A' in the Right image (U)r,Vr) And converting the circle center A' in the Right image into a Left image coordinate system, namely:
Further preferably, the method for calculating the horizontal tilt angle of the camera by processing the two captured images of the calibration board in step 3 is as follows:
step 3.1, calculating all circle parameters C (r, U and V) in the two images by using a circle Hough transformation method according to the Left image obtained in the step 1 and the Right image obtained in the step 2; wherein r represents the radius of the circle;
step 3.2, sorting the circle parameters in each image from small to large according to the radius, wherein the first two circles with the largest radius are positioning circles, dividing a common area according to the two positioning circles in each image, and calculating all circles in the common areaThe center of a circle in the Left image is recorded asThe center of a circle in the Right image isWherein k is a subscript of the circle center, and N represents all circle centers in the public area;
step 3.3, calculating the horizontal plane inclination angle of the camera according to the corresponding coordinates of the circle center in the Left image and the Right image in the public area
Step 3.4 θ obtained according to step 3.3kThe average value of the camera horizontal plane tilt angle can be calculated as:
advantageous effects
The graphic manufacturing precision of the calibration plate can reach 1 micron, and the moving precision of the working platform can be less than 1 micron, so that the calibration precision is high; aiming at the calibration of different camera views and different motion ranges, the step size can be changed, and the method has strong adaptability; the invention is non-contact measurement, and has no damage to the calibration plate; the horizontal plane inclination angle obtained after calibration plays an important role in establishing an error model of a high-precision assembly system, positioning a large-size object, splicing images and transforming coordinates; the method has the advantages of simple and easy operation of the measuring process, simple and easy use of the design of the calibration plate, high precision of the measuring result and capability of meeting the requirement of calculating the planning coordinate of the image acquisition path.
Drawings
FIG. 1 is a schematic view of an apparatus for measuring a tilt angle of a camera in a horizontal plane according to the present invention;
FIG. 2 is a graphical illustration of a calibration plate according to the present invention;
FIG. 3 is a schematic diagram of calibration plate graphic image acquisition in accordance with the present invention;
FIG. 4 is a schematic diagram of the common area point calculated camera horizontal tilt angle of the present invention.
Fig. 5 shows the Left and Right images of the calibration board of the present embodiment.
In the figure, 1 work platform, 2 motor Y-axis, 3 calibration plate, 4 motor X-axis, 5 calibration plate carrier, 6 light source, 7 lens, 8 camera, 9 support base and 10 camera support.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
the invention provides a method for measuring the horizontal plane inclination angle of a camera, which controls a working platform to move through a motor, so that a calibration board graph enters the field of view of the camera, simultaneously adjusts the proper position of the calibration board graph in the field of view of the camera, shoots an image of the calibration board graph, then keeps a Y axis of the motor still, moves for a certain step length along an X axis of the motor, shoots an image of the other calibration board graph, and because the camera is installed on a horizontal plane, the coordinate values of common area points in the two calibration board graph images are different, and the two shot images are processed, so that the inclination angle of the camera on the horizontal plane can be obtained.
As shown in fig. 1, a device for measuring the horizontal inclination angle of a camera includes a working platform 1, a motor Y-axis 2, a calibration plate 3, a motor X-axis 4, a calibration plate carrier 5, a light source 6, a lens 7, a camera 8, a support base 9 and a camera support 10;
the light source 6 is mounted on a lens 7, the lens 7 is mounted on a camera 8, the camera 8 is fixedly mounted on a camera support 10, and the camera support 10 is fixedly connected with a support base 9; the calibration device is characterized in that a working platform 1 is arranged below the light source 6, a motor X shaft 4 is fixedly connected to the middle of the working platform 1, the motor X shaft 4 is in sliding connection with a motor Y shaft 2, and the calibration board carrying platform 5 is in sliding connection with the motor Y shaft 2.
Example (b):
a method for measuring the horizontal plane inclination angle of a camera comprises the following steps:
As shown in fig. 2, the pattern on the calibration plate is circular, the calibration plate is made of glass material, the pattern on the calibration plate is made by an electron beam lithography method, the size deviation of the pattern is less than ± 0.5 micrometer, the thickness of the calibration plate is 1.6mm, the rectangular width and length of the calibration plate are 10mm × 20mm, the radius of the standard Circle is r1 ═ 0.5mm, the Circle distance is 1.5mm, two positioning circles with radius r2 ═ 1mm are also present on the calibration plate, the common area of the calibration plate in the row where the positioning circles are located and the area between the positioning circles is 4x4, and the common area is used for calculating the inclination angle of the horizontal plane of the camera.
As shown in fig. 3, the Public area Public Region of the calibration board is first moved to the Right side of the camera view, the captured calibration board image is recorded as a Left image, then the motor Y-axis 2 is kept still, and the Public area Public Region of the calibration board is moved to the Left side of the camera view by a distance Δ d of 5mm in the negative direction of the motor X-axis 4 or in the Left direction (which is equivalent to the distance Δ d in the positive direction of the calibration board or in the Right direction of the camera by a distance Δ d of 5 mm), so that the captured calibration board image is recorded as a Right image.
Wherein, as shown in FIG. 4, suppose θ is counterclockwise (θ)>0) In the Left image, the center a of the circle in the common area is (U)l,Vl) (ii) a When the working platform 1 moves along the negative direction of the X axis 4 of the motor by delta d which is 5mm step length, the circle center A in the original public area is A' in the Right image (U)r,Vr) And converting the circle center A' in the Right image into a Left image coordinate system, namely:
When theta is clockwise (theta)<0) In the Left image, the center of a circle A in the common area is (U)l,Vl) (ii) a When the working platform 1 moves along the negative direction of the X axis 4 of the motor by delta d which is 5mm step length, the circle center A in the original public area is A' in the Right image (U)r,Vr) And converting the circle center A' in the Right image into a Left image coordinate system, namely:
The method for calculating the horizontal tilt angle of the camera by processing the two captured calibration plate images in step 3 is as follows, as shown in fig. 5:
step 3.1, calculating all circle parameters C (r, U and V) in the two images by using a circle Hough transformation method according to the Left image obtained in the step 1 and the Right image obtained in the step 2; wherein r represents the radius of the circle;
step 3.2, setting the common area point in the Left image asi and j respectively represent the row and the column of the common area, C is sorted from large to small according to the radius, and the first two elements are taken as the circle parameters of the two positioning circlesAndif it is notThenIf not, then,m and n are subscripts of the two positioning circles respectively;
step 3.3, remove ClL in (1)21And L34If, if(TpA coordinate difference threshold for a circle parameter), then ifThen L is obtained11If, ifThen L is obtained31And L41Likewise, L can be obtained14、L24And L44;
Step 3.4, remove ClL in (1)11、L31、L41、L14、L24And L44If, ifThen ifThen according toCan be given L12And L13Likewise, L can be obtained22、L23、L32、L33、L42And L43;
Step 3.5, similarly, the common area point in the Right image corresponding to the Left image one by one can be obtained from steps 3.2, 3.3 and 3.4
Step 3.6, which can be obtained from step 3.5, the horizontal plane inclination angle of the camera is:
the above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, but any modifications or equivalent variations made according to the technical spirit of the present invention are within the scope of the present invention as claimed.
Claims (6)
1. The device for measuring the horizontal plane inclination angle of the camera is characterized by comprising a working platform, a motor Y axis, a calibration plate, a motor X axis, a calibration plate carrying platform, a light source, a lens, a camera, a support base and a camera support;
the camera comprises a light source, a camera support, a support base and a camera, wherein the light source is arranged on the camera, the camera is fixedly arranged on the camera support, and the camera support is fixedly connected with the support base; the calibration device comprises a light source, a calibration board carrying platform, a motor Y shaft, a motor X shaft, a motor Y shaft, a calibration board carrying platform and a motor Y shaft, wherein the light source is arranged below the calibration board carrying platform.
2. A method for measuring the horizontal plane inclination angle of a camera is characterized by comprising the following steps:
step 1, placing a calibration plate on a calibration plate carrying platform, setting a part of the calibration plate as a public area, controlling the movement of a working platform through a moving motor, enabling the calibration plate to enter the visual field of a camera, and shooting an image of the calibration plate, wherein the image comprises the public area of a fixed plate;
step 2, keeping the Y axis of the motor still, moving the working platform by a step length delta d along the X axis of the motor, and shooting an image of another calibration plate, wherein the image comprises a public area of the calibration plate; wherein, the images of the two calibration plates have the same public area;
step 3, processing the two shot calibration plate images, wherein the horizontal plane inclination angle of the camera is determined according to the imageAnd calculating, wherein Δ V is the difference of the V coordinate values of the common area points, and Δ U is the difference of the U coordinate values of the common area points.
3. The method of measuring the tilt angle of the horizontal plane of a camera according to claim 2, wherein: the pattern on the calibration plate is circular, the radius of the standard circle is r1, two positioning circles with the radius of r2 exist on the calibration plate, the positioning circles are located in different rows, the area between the row where the positioning circles are located and the row is the common area of the calibration plate, the point of the common area is the center of a circle in the common area, and r2 is greater than r 1.
4. The method for measuring the horizontal plane inclination angle of the camera according to claim 2, wherein in the step 1, the common area of the calibration plate is moved to the right side of the camera view, and the taken calibration plate image is recorded as a Left image; and (3) keeping the Y axis of the motor still in the step (2), moving the working platform by delta d step length along the negative direction of the X axis of the motor or leftwards, so that the public area of the calibration plate is moved to the left side of the visual field of the camera, and recording the shot image of the calibration plate as a Right image.
5. The method of claim 4, wherein the center of circle A in the common area in the Left image is (U)l,Vl) (ii) a When the working platform moves delta d step length along the negative direction of the X axis of the motor, the circle center A in the original public area is A' in the Right image (U)r,Vr) And converting the circle center A' in the Right image into a Left image coordinate system, namely:
6. The method for measuring the tilt angle of the horizontal plane of the camera according to claim 5, wherein the step 3 is performed by processing the two images of the calibration plate to calculate the tilt angle of the horizontal plane of the camera as follows:
step 3.1, calculating all circle parameters C (r, U and V) in the two images by using a circle Hough transformation method according to the Left image obtained in the step 1 and the Right image obtained in the step 2; wherein r represents the radius of the circle;
3.2, sorting the circle parameters in each image from small to large according to the radius, wherein the first two circles with the largest radius are positioning circles, dividing a common area according to the two positioning circles in each image, calculating the coordinates of the circle centers of all circles in the common area, and recording the circle center in the Left image as the circle centerThe center of a circle in the Right image isWherein k is a subscript of the circle center, and N represents all circle centers in the public area;
step 3.3, calculating the horizontal plane inclination angle of the camera according to the corresponding coordinates of the circle center in the Left image and the Right image in the public area
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CN117268342A (en) * | 2023-09-22 | 2023-12-22 | 合肥筑创空间建筑设计有限公司 | Auxiliary mapping device for scene simulation distance |
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