CN109087361B - Monocular camera-based method for calibrating transverse distance of forward object - Google Patents
Monocular camera-based method for calibrating transverse distance of forward object Download PDFInfo
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- CN109087361B CN109087361B CN201810799194.4A CN201810799194A CN109087361B CN 109087361 B CN109087361 B CN 109087361B CN 201810799194 A CN201810799194 A CN 201810799194A CN 109087361 B CN109087361 B CN 109087361B
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Abstract
The application discloses preceding object lateral distance calibration method based on monocular camera utilizes the monocular camera to carry out the calculation of lateral distance to all kinds of objects on the road surface in the place ahead, utilizes mathematical relation, carries out the function with corresponding lateral distance with the pixel coordinate on the image and corresponds, and the lateral vertical distance that can very easy calculation place ahead barrier distance apart from the camera dead ahead. The method has the advantages that the used equipment and instruments are simple, the transverse distances of the cameras of different types arranged at different positions can be calibrated, after the cameras are arranged at fixed positions and are measured, the obtained actual transverse distances are data output by a fixed fitting equation, and reference can be provided for calculating the transverse distance between the front vehicle and the vehicle by the monocular camera on the vehicle.
Description
Technical Field
The application relates to the field of intelligent terminals, in particular to a monocular camera-based method for calibrating the transverse distance of a forward object.
Background
With the continuous development of artificial intelligence, advanced functions such as driving assistance and the like begin to appear in the automobile field, especially, machine vision plays an indispensable role in the function of a driving assistance system, and meanwhile, the vertical distance between a forward obstacle and a camera in front can be calculated by using a visual image in the function of calculating the distance between the forward obstacle and the camera, namely, the calculation of the transverse distance between the forward obstacle and the camera can be realized.
Most of the existing forward object transverse distance calculation adopts radar to acquire corresponding obstacle transverse distance information, however, in the multi-sensor fusion algorithm under the complex weather condition, the information of visual ranging and various radar ranging needs to be utilized for fusion, so that a reasonable distance calculation value is given, and the machine judgment accuracy is ensured.
The method can utilize the monocular camera to calculate the transverse distance of various objects on the front road surface, utilizes the mathematical relationship to carry out function correspondence on the pixel coordinate on the image and the corresponding transverse distance, can easily know the transverse vertical distance between the front obstacle and the front of the camera, and is simple in calibration calculation and easy to operate.
Disclosure of Invention
The invention aims to provide a simple and easy-to-operate method, the method is used for calibrating based on the transverse distance of a monocular camera, the camera is fixed at a certain position, and the transverse distance of an image acquired by the camera can be calibrated and calculated by adjusting the pitch angle, and the calibration and measurement method is simple.
In order to achieve the above object, the present invention provides a method for calibrating a lateral distance of a forward object based on a monocular camera, comprising the following steps:
step 1: selecting a flat road surface with clear lane lines as an experimental field, fixing a camera on an installation frame, starting the camera to observe an acquired image, and adjusting a pitch angle of the camera to a proper position;
step 2: moving the position of the camera mounting rack, and aligning the optical axis of the camera to the lane line on one side to ensure that the lane line is superposed with the vertical center position of the image;
and step 3: the tape measures are pulled straight along the lane line from the installation position of the camera, the position which is at any proper distance away from the camera is selected, the other tape measure is vertically pulled, obvious markers are placed on the tape measures at equal distances, and the interval distance is recorded;
and 4, step 4: selecting two points at one side of the lane line, returning pixel coordinates of the two points through a program, and calculating straight lines of the two points, wherein the image coordinates of the vanishing point are a straight line parallel to the optical axis and a focus of the straight line of the optical axis, and the position coordinates of the vanishing point of the image are calculated;
and 5: clicking the positions of the obvious markers on the ground one by one at equal intervals, returning to image coordinates, and establishing a relation between an included angle between the straight line and the optical axis center line and an actual transverse distance;
step 6: and fitting an equation between an included angle between a straight line formed by the obvious marker and the vanishing point and the optical axis central line and the actual transverse distance, substituting the equation into a program, and clicking any point in the image to obtain the vertical distance between the point and the optical axis central line.
In step 1, the proper position is such that the vanishing point of the image is located about 1/3 above the image.
In step 6, the equation is fitted using matlab.
According to another aspect of the invention, the calibration system applying the calibration method comprises a bracket for fixing the camera, the camera for calibration, a transverse distance calibration measuring and calculating program, a measuring tape, an obvious marker required by transverse distance calibration and a flat road surface containing clear lane lines.
Has the advantages that: (1) the method is based on a monocular camera as hardware, the vertical distance between any point on the ground and the center line of an optical axis can be determined through calibration, and pixel coordinates can correspond to the actual transverse distance one by one.
(2) The method has the advantages that the used equipment and instruments are simple, the transverse distances of different cameras can be calibrated, the cameras are arranged at fixed positions for measurement, and the obtained actual transverse distance is the data output by the fixed fitting equation.
(3) The method can provide reference for a monocular camera on the vehicle to calculate the transverse distance between the front vehicle and the vehicle.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application.
FIG. 1 is a schematic diagram of a monocular camera-based lateral distance calibration method;
FIG. 2 is an experimental diagram of lateral distance calibration in actual operation.
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. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
Example 1
The embodiment of the invention provides a monocular camera-based method for calibrating the transverse distance of a forward object, which comprises the following specific implementation steps:
1) in order to calibrate the transverse distance conveniently, therefore, select the level road surface that contains clear lane line as the experimental ground, like fig. 2, fix the camera on the mounting bracket, open the camera and observe the image that obtains, adjust camera pitch angle to suitable position, make the disappearance point of image be located about 1/3 positions above the image, the position that the sky can refer to in the image is shown in fig. 1 to the proportion.
2) And moving the position of the camera mounting rack, and aligning the optical axis of the camera to the lane line on one side to ensure that the lane line is superposed with the vertical central position of the image.
3) The tape measure is pulled straight along the lane line from the installation position of the camera, a position with any proper distance away from the camera is selected, the other tape measure is vertically pulled, obvious markers are placed on the tape measures at equal distances, and the interval distance is recorded, as shown in figure 2.
4) Two points are arbitrarily selected on one lane line, pixel coordinates of the two points are returned by a program, and a straight line passing the two points is obtained, and image coordinates of a vanishing point are a straight line parallel to the optical axis and a focal point of the optical axis straight line, so that the vanishing point position coordinates of the image can be obtained, and the calculation method is as shown in fig. 1, and the pixel coordinates of the vanishing point P in the image are obtained by simultaneous solving of a left lane line and a straight line of the image center line, i.e., the optical axis.
5) Clicking the positions of the obvious markers on the ground one by one at equal intervals, such as the intersection points of the markers placed on the ground and the ground in the figure 2, and returning to the image coordinates, wherein the transverse distances from any point on a straight line passing through the point and the vanishing point to the center of the optical axis are equal, so that the relation can be established between the included angle between the straight line and the central line of the optical axis and the actual transverse distance.
6) And fitting an equation between an included angle between a straight line formed by the obvious marker and the vanishing point and the central line of the optical axis and the actual transverse distance by utilizing matlab, substituting the equation into a program, clicking any point in the image, establishing a linear equation by utilizing the coordinates of the point and the coordinates of the vanishing point to obtain the included angle between the point and the central line of the optical axis in the image, and substituting the linear equation into the fitting equation to obtain the vertical distance between the point and the central line of the optical axis.
Example 2
The embodiment of the invention also provides a calibration system applying the calibration method, which comprises a bracket for fixing the camera, the camera for calibration, a transverse distance calibration measuring and calculating program, a measuring tape, an obvious marker required by transverse distance calibration and a flat road surface containing clear lane lines.
The embodiment of the invention takes the monocular camera as a hardware basis, can determine the vertical distance between any point on the ground on the image and the central line of the optical axis through calibration, and can correspond the pixel coordinates to the actual transverse distance one by one. The method has the advantages that the used equipment and instruments are simple, the transverse distances of different cameras can be calibrated, the cameras are arranged at fixed positions for measurement, and the obtained actual transverse distance is the data output by the fixed fitting equation. The method can provide reference for a monocular camera on the vehicle to calculate the transverse distance between the front vehicle and the vehicle.
In the description of the present invention, it is to be understood that the orientation or positional relationship indicated by the orientation words such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal" and "top, bottom", etc. are usually based on the orientation or positional relationship shown in the drawings, and are only for convenience of description and simplicity of description, and in the case of not making a reverse description, these orientation words do not indicate and imply that the device or element being referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore, should not be considered as limiting the scope of the present invention; the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself.
Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and the terms have no special meanings unless otherwise stated, and therefore, the scope of the present invention should not be construed as being limited.
In addition, the above-mentioned serial numbers of the embodiments of the present application are merely for description, and do not represent the merits of the embodiments. In the above embodiments of the present application, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (2)
1. A method for calibrating the transverse distance of a forward object based on a monocular camera is characterized by comprising the following steps:
step 1: selecting a flat road surface with clear lane lines as an experimental field, fixing a camera on an installation frame, starting the camera to observe an acquired image, and adjusting a pitch angle of the camera to a proper position;
step 2: moving the position of the camera mounting rack, and aligning the optical axis of the camera to the lane line on one side to ensure that the lane line is superposed with the vertical center position of the image;
and step 3: the tape measures are pulled straight along the lane line from the installation position of the camera, the position which is at any proper distance away from the camera is selected, the other tape measure is vertically pulled, obvious markers are placed on the tape measures at equal distances, and the interval distance is recorded;
and 4, step 4: selecting two points randomly on a lane line on one side by taking the upper left corner of an image obtained by a camera as a coordinate origin, taking the horizontal right corner as an X-axis forward direction and the vertical downward corner as a Y-axis forward direction, returning pixel coordinates of the two points through a program, and calculating a straight line of the two points, wherein the image coordinate of a vanishing point is an intersection point of a straight line parallel to an optical axis and the straight line of the optical axis, so as to calculate the position coordinate of the vanishing point of the image;
and 5: clicking the positions of the obvious markers on the ground at equal intervals one by one, returning to image coordinates, and establishing a relation between the included angle between the straight line and the optical axis center line in the step 4 and the actual transverse distance;
step 6: fitting an equation between an included angle between a straight line formed by the obvious marker and the vanishing point and the optical axis central line and the actual transverse distance, substituting the equation into a program, and clicking any point in the image to obtain the vertical distance between the point and the optical axis central line;
in step 1, the proper position means that the vanishing point of the image is located at about 1/3 above the image;
in step 6, the equation is fitted using matlab.
2. A calibration system applying the calibration method as claimed in claim 1, characterized by comprising a bracket for fixing the camera, a camera for calibration, a transverse distance calibration calculation program, a tape measure, an obvious marker required for transverse distance calibration, and a flat road surface containing clear lane lines.
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| CN201810799194.4A CN109087361B (en) | 2018-07-19 | 2018-07-19 | Monocular camera-based method for calibrating transverse distance of forward object |
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| CN109583434B (en) * | 2019-01-18 | 2021-04-23 | 浙江吉利汽车研究院有限公司 | Vehicle overlapping degree obtaining method and device |
| CN110490936B (en) * | 2019-07-15 | 2021-09-07 | 杭州飞步科技有限公司 | Calibration method, device and equipment of vehicle camera and readable storage medium |
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