CN112672127B - Automatic calibration method for projection reflection picture - Google Patents
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- CN112672127B CN112672127B CN202011599206.2A CN202011599206A CN112672127B CN 112672127 B CN112672127 B CN 112672127B CN 202011599206 A CN202011599206 A CN 202011599206A CN 112672127 B CN112672127 B CN 112672127B
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Abstract
The invention provides a projection reflection picture automatic calibration method, which comprises the steps of obtaining three-dimensional point cloud data; creating a three-dimensional model to be projected according to the three-dimensional point cloud data; performing light path conversion on the three-dimensional model to obtain incident mirror image light; and carrying out image correction according to a correction strategy on the incident mirror image light. The invention can complete the correction by utilizing the reflected light rays at first, and then convert the light path conversion process into the direct light to complete the correction, has small data amount needing to be processed and calculated, can realize automatic calibration, is easy to operate and convenient to correct, is suitable for content production of any scene, does not need to consider the problems of image distortion and image size, does not need to consume a large amount of time for adjusting the image distortion by an operator, saves the correction time and is convenient to correct.
Description
Technical Field
The invention relates to the technical field of machine vision, in particular to an automatic calibration method for a projection reflection picture.
Background
In order to realize large projection coverage of a single projector, the current solution is to use a track mirror technology. The method for realizing the track mirror reflects light of a projector out through a mirror surface, and realizes movement of light shadow through driving the mirror surface to rotate horizontally and vertically through a motor.
Because the lens of the orbit mirror is not perspective imaging in an ideal state but has distortion of different degrees, theoretically, the distortion of the lens comprises radial distortion and tangential distortion, and the influence caused by the tangential distortion is small, only the radial distortion is usually considered in practical application, and only the first two coefficients of the dominant binary Taylor series expansion are considered in the solving process of the radial distortion. In actual use, it takes a lot of time to adjust the image distortion. The manual calibration method is complicated to operate. After the content is replaced, the re-pointing and calibration are required, and the content production cannot be realized under the condition of uncertain large scene distance and space.
Disclosure of Invention
In view of the above, the present invention provides an automatic calibration method for a projection reflection image.
In order to solve the technical problems, the invention adopts the technical scheme that: a projection reflection picture automatic calibration method comprises the steps of obtaining three-dimensional point cloud data;
creating a three-dimensional model to be projected according to the three-dimensional point cloud data;
performing light path conversion on the three-dimensional model to obtain incident mirror image light;
and carrying out image correction according to a correction strategy on the incident mirror image light.
In the present invention, preferably, the optical path conversion specifically includes the following steps:
obtaining incident mirror image light according to the incident light according to a mirror image principle;
and taking rays emitted by the projector as incident mirror image rays in a three-dimensional space, wherein the incident mirror image rays irradiate on a calibration plane to obtain a model intersection point.
In the present invention, preferably, the modification strategy specifically includes the following steps:
calculating to obtain a projection distance according to the intersection point of the incident mirror image ray and the model;
calculating according to the projection distance to obtain the size of the projection image and the intersection point of the actual model;
and obtaining a correction straight line for the actual model intersection point according to a forward projection strategy and determining a correction point.
In the present invention, preferably, the orthographic projection strategy specifically includes the following steps:
establishing an orthographic projection surface in a virtual space according to the incident mirror image light;
constructing a connecting line between the intersection point of the actual model and the position of the projector and obtaining a correction straight line;
the intersection point of the correction straight line and the orthographic projection surface is a correction point.
In the invention, preferably, the process of acquiring the three-dimensional point cloud data is to irradiate the mirror surface where the track mirror is located by using a laser radar and acquire the three-dimensional point cloud data by rotating the mirror surface.
In the present invention, it is preferable that the lidar is installed at a position where the projector is located, and the lidar is configured as a multiline lidar for use in the self-sustaining measurement.
In the present invention, it is preferable that the three-dimensional model to be projected is in the same scale as the actual usage scene.
In the present invention, it is preferable that the projector is provided as an orbital mirror after performing a calibration operation.
In the present invention, preferably, the performing of the calibration operation specifically includes the following steps:
shooting from different angles to obtain a plurality of template images;
detecting and obtaining characteristic points of the template image;
obtaining ideal internal reference and ideal external reference of the orbit mirror according to the corresponding relation between the image coordinate and the world coordinate by the characteristic point of the template image;
calculating a distortion coefficient by adopting a least square method;
and obtaining the actual internal parameter, the actual external parameter and the actual distortion coefficient of the orbit mirror according to a maximum likelihood estimation algorithm.
In the present invention, preferably, the step of obtaining the ideal internal reference and the ideal external reference of the orbit mirror specifically comprises the following steps:
obtaining a homography matrix according to homographies from the calibration plane to the image plane;
solving an internal reference matrix by using a constraint condition;
and deriving an external parameter matrix according to the internal parameter matrix.
The invention has the advantages and positive effects that: the invention completes the correction by utilizing the reflected light rays at first, converts the light path conversion process into the direct light path conversion process, completes the correction, has smaller data amount needing to be processed and calculated, can realize automatic calibration, is easy to operate and convenient to correct, is suitable for content production of any scene, does not need to consider the problems of image distortion and image size, does not need to consume a large amount of time for operators to adjust the image distortion, saves the correction time and is convenient to correct.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic diagram of the optical path conversion of an automatic calibration method for a projection reflection frame according to the present invention;
FIG. 2 is a schematic diagram of an automatic calibration method for a projection reflection image according to the present invention, which obtains a calibration straight line and determines a calibration point according to a forward projection strategy for an intersection point of an actual model;
FIG. 3 is a schematic diagram of a three-dimensional model to be projected for a projected reflection picture auto-calibration method of the present invention;
FIG. 4 is a flowchart illustrating an automatic calibration method for a projection reflection frame according to the present invention;
FIG. 5 is a schematic diagram of an execution calibration process of the automatic calibration method for a projection reflection frame according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When a component is referred to as being "connected" to another component, it can be directly connected to the other component or intervening components may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
As shown in fig. 1 to 5, the present invention provides an automatic calibration method for a projection reflection image, which includes acquiring three-dimensional point cloud data;
creating a three-dimensional model to be projected according to the three-dimensional point cloud data;
performing light path conversion on the three-dimensional model to obtain incident mirror image light;
and carrying out image correction according to a correction strategy on the incident mirror image light.
The optical path conversion is to convert the reflection into more direct incidence by the mirror image principle, so that the operation is that when the mirror surface (i.e. the calibration plane) rotates, the incident light emitted by the projector providing the incident light I is fixed and unchanged, N is the surface normal of the calibration plane, and the incident mirror image light I 'can be obtained by calculation according to the actual rotation angle of the calibration plane, so that the image correction is performed according to the incident mirror image light I'.
In this embodiment, further, the optical path conversion specifically includes the following steps:
obtaining incident mirror image light according to the incident light according to a mirror image principle;
and taking rays emitted by the projector as incident mirror image rays in the three-dimensional space, wherein the incident mirror image rays irradiate the calibration plane to obtain intersection point coordinates of the model intersection points.
The incident light is provided and emitted by the track mirror, the incident point and the incident angle are known, the linear equation of the incident light is obtained through calculation, the linear equation of the incident mirror image light can be obtained according to the linear equation of the incident light and the linear equation of the calibration plane according to the mirror image principle as the incident light and the incident mirror image light are symmetrically distributed about the calibration plane, and the coordinate of the intersection point of the incident mirror image light and the calibration plane is obtained at the same time, wherein the intersection point is the model intersection point.
In this embodiment, further, the modification strategy specifically includes the following steps:
calculating to obtain a projection distance according to the intersection point of the incident mirror image ray and the model;
calculating according to the projection distance to obtain the size of the projection image and the intersection point of the actual model;
and obtaining a correction straight line for the actual model intersection point according to a forward projection strategy and determining a correction point.
And calculating to obtain a projection distance according to the coordinates of the model intersection point, the incident angle and a linear equation where the incident mirror image light is located, and calculating to obtain the size of the projection image and the coordinates of the actual model intersection point P according to the projection distance, as shown in fig. 2.
In this embodiment, further, the orthographic projection strategy specifically includes the following steps:
establishing an orthographic projection surface in a virtual space according to the incident mirror image light;
constructing a connecting line between the intersection point of the actual model and the position of the projector and obtaining a correction straight line;
the intersection point of the correction straight line and the orthographic projection surface is a correction point. Establishing an orthographic projection surface in a virtual space to obtain a linear equation where the orthographic projection surface is located, determining a linear equation where the intersection point P of the actual model and the projector are located according to two points because the coordinates of the intersection point P of the actual model and the coordinates of the projector are known, obtaining the linear equation where the connection line of the intersection point P of the actual model and the projector is located, obtaining the coordinates of the intersection point of the linear equation and the linear equation where the orthographic projection surface is located, wherein the coordinates are the coordinates of the correction point, and then rotating and translating a coordinate system where the laser radar is located according to a rotation matrix and a translation vector to enable the coordinate system to be overlapped with a coordinate system of the track mirror, so that calibration between the laser radar and the track mirror is completed. The method has the advantages that the initial correction is completed by utilizing the reflected light, the light path conversion process is converted into the direct light to complete the correction, the data amount needing to be processed and calculated is small, the method is easy to operate and convenient to correct, the method is suitable for content production of any scene, the problems of image distortion and image size do not need to be considered, operators do not need to spend a large amount of time to adjust the image distortion, the correction time is saved, and the correction is convenient.
In this embodiment, further, the process of obtaining the three-dimensional point cloud data is to irradiate the mirror surface where the orbit mirror is located through a laser radar, obtain the three-dimensional point cloud data through mirror surface rotation, and create a three-dimensional model to be projected through the three-dimensional point cloud.
In this embodiment, further, the lidar is installed at a position where the projector is located, and the lidar is configured as a multiline lidar for self-supported measurement.
In this embodiment, further, the three-dimensional model to be projected has the same scale as the actual usage scene.
The model of 1:1 is constructed in the three-dimensional space for the measured data, and the laser radar is installed at the position of the projector to ensure that the position of the projector in the three-dimensional space is coincident and the same with the position of the projector in the actual space, and the distance and the relative position between the laser radar and the projector are fixed and do not change any more. The laser radar is set as a multi-line laser radar for self-supporting measurement, in particular to a laser rotary ranging radar which simultaneously emits and receives a plurality of laser beams.
In this embodiment, further, the projector is configured as an orbit mirror after performing the calibration operation. The internal reference matrix of the orbital mirror is known and the problems of image distortion and size are eliminated.
In this embodiment, further, the executing the calibration operation specifically includes the following steps:
shooting from different angles to obtain a plurality of template images;
detecting and obtaining characteristic points of the template image;
obtaining ideal internal reference and ideal external reference of the orbit mirror according to the corresponding relation between the image coordinate and the world coordinate by the characteristic point of the template image;
calculating a distortion coefficient by adopting a least square method;
and obtaining the actual internal parameter, the actual external parameter and the actual distortion coefficient of the orbit mirror according to a maximum likelihood estimation algorithm.
In this embodiment, further, the step of obtaining the ideal internal reference and the ideal external reference of the orbit mirror specifically includes the following steps:
obtaining a homography matrix according to homographies from the calibration plane to the image plane;
solving an internal reference matrix by using a constraint condition;
and deriving an external parameter matrix according to the internal parameter matrix.
Homography refers to the projection mapping of one plane to another, obtained from an orbital mirror model
Where M's homogeneous coordinates represent the pixel coordinates (u, v, 1) of the image plane, M's homogeneous coordinates represent the coordinates (X, Y, Z, 1) of the world coordinate system, A [ R T ]]Point P, R represents a rotation matrix, T represents a translation matrix, S represents a scale factor, A represents an internal parameter of the orbital mirror,
α = f/dx, β = f/dy, γ represents the dimension deviation of the pixel point in the x, y directions, the coordinate value is not changed for the homogeneous coordinate scale factor, since the calibration object is a plane, the world coordinate system is constructed on the plane of Z =0, and then homography operation is performed,
let the homography matrix H = A [ r ] 1 r 2 t]Then, then
Calibration object coordinates (x, y) as known quantities, pixel coordinates (u, v) obtained by an orbital mirror, homography matrix H = [ H ], [ 1 h 2 h 3 ]。
Let [ h) 1 h 2 h 3 ]＝λA[r 1 r 2 t]Two constraint conditions are obtained: r1, r2 are orthogonal, resulting in r1 x r2=0; the modulus of the rotation vector is 1, then | r 1 |＝|r 2 L =1. Result in r1= h1A -1 ，r2＝h2A -1 And the following formula is obtained according to the constraint condition
Order to
Get solved, v ij ＝[h i1 h j1 ，h i1 h j2 +h i2 h j1 ，h i2 h j2 ，h i3 h j1 +h i1 h j3 ，h i3 h j2 +h i2 h j3 ，h i3 h j3 ] T To obtain the following equation system
Different template images are obtained by changing the relative position between the orbit mirror and the calibration plate, and then B is obtained by estimation, and then six degrees of freedom of the internal reference matrix A of the orbit mirror are obtained by cholesky decomposition. Due to [ h ] 1 h 2 h 3 ]＝λA[r 1 r 2 t]By simplifying the above formula
Wherein the content of the first and second substances,
the problems of image distortion and image size are solved, operators do not need to spend a large amount of time to adjust the image distortion, correction time is saved, and correction is convenient. The invention completes the correction by utilizing the reflected light rays at first, converts the light path conversion process into the direct light path conversion process to complete the correction, has small data amount needing to be processed and calculated, can realize automatic calibration, is easy to operate and convenient to correct, and is suitable for content production of any scene.
The embodiments of the present invention have been described in detail, but the description is only for the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention should be covered by this patent.
Claims (7)
1. A method for automatically calibrating a projection reflection picture is characterized by comprising
Acquiring three-dimensional point cloud data;
creating a three-dimensional model to be projected according to the three-dimensional point cloud data;
performing light path conversion on the three-dimensional model to obtain incident mirror image light;
realizing image correction according to a correction strategy for incident mirror image light;
obtaining incident mirror image light according to the incident light according to a mirror image principle;
taking rays emitted by a projector as incident mirror image rays in a three-dimensional space, wherein the incident mirror image rays irradiate a calibration plane to obtain intersection point coordinates of model intersection points;
the incident light is provided and emitted by the track mirror, the incident point and the incident angle are known, the linear equation of the incident light is obtained through calculation, the linear equation of the incident mirror image light can be obtained according to the linear equation of the incident light and the linear equation of the calibration plane according to the mirror image principle as the incident light and the incident mirror image light are symmetrically distributed about the calibration plane, and the coordinate of the intersection point of the incident mirror image light and the calibration plane is obtained at the same time, wherein the intersection point is the model intersection point;
calculating to obtain a projection distance according to the intersection point of the incident mirror image ray and the model;
calculating according to the projection distance to obtain the size of the projection image and the intersection point of the actual model;
obtaining a correction straight line for the actual model intersection point according to a forward projection strategy and determining a correction point;
the orthographic projection strategy specifically comprises the following steps:
establishing an orthographic projection surface in a virtual space according to the incident mirror image light;
constructing a connecting line between the intersection point of the actual model and the position of the projector and obtaining a correction straight line;
the intersection point of the correction straight line and the orthographic projection surface is a correction point.
2. The method as claimed in claim 1, wherein the step of obtaining the three-dimensional point cloud data is to irradiate a mirror surface of the orbit mirror with a laser radar, and obtain the three-dimensional point cloud data by rotating the mirror surface.
3. The method according to claim 2, wherein the lidar is mounted at a position where the projector is located, and the lidar is configured as a multiline lidar for self-supported measurement.
4. The method according to claim 1, wherein the three-dimensional model to be projected has the same scale as the actual scene.
5. The method according to claim 3, wherein the projector is configured as an orbital mirror after performing the calibration operation.
6. The method according to claim 5, wherein the performing calibration specifically comprises the following steps:
shooting from different angles to obtain a plurality of template images;
detecting and obtaining characteristic points of the template image;
obtaining ideal internal reference and ideal external reference of the orbit mirror according to the corresponding relation between the image coordinate and the world coordinate by the characteristic point of the template image;
calculating a distortion coefficient by adopting a least square method;
and obtaining the actual internal parameter, the actual external parameter and the actual distortion coefficient of the orbit mirror according to a maximum likelihood estimation algorithm.
7. The method according to claim 6, wherein the step of obtaining the ideal internal reference and the ideal external reference of the orbital mirror comprises the steps of:
obtaining a homography matrix according to homographies from the calibration plane to the image plane;
solving an internal reference matrix by using a constraint condition;
and deriving an external parameter matrix according to the internal parameter matrix.
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