A camera calibration system and calibration method for road surface detection

Abstract

The present invention provides a camera calibration system and a calibration method for road surface detection. The camera calibration system for road surface detection includes: a ranging sensor module for measuring the distance between the ranging sensor module and the ground; a two-dimensional attitude sensor module for detecting the tilt angle of the imaging chip of the camera relative to the ground; and a calculation module, wherein both the ranging sensor module and the two-dimensional attitude sensor module are electrically connected to the calculation module. The camera calibration system for road surface detection of the present invention can adjust the camera according to the actual needs of road surface detection, perform real-time calibration, has a fast calibration speed, is simple to operate, has a wide application range, and has high engineering application value.

Description

Technical Field

[0001] The present invention relates to the technical field of road surface detection, and in particular, to a camera calibration system and a calibration method for road surface detection. Background Art

[0002] Road surface detection refers to a series of operations of using an area array camera to capture road surface images for observing and measuring road surface disease data. Before road surface detection, it is necessary to calibrate the area array camera, which includes internal parameter and external parameter calibration. The internal parameter is the internal parameter of the area array camera and can be set by itself, while the external parameter needs to be calibrated using a calibration device.

[0003] Currently, generally, a checkerboard is used to take several pictures for calibration. However, with the gradual development of road surface detection, the area array camera is gradually developing towards a non-fixed type. When the area array camera is moved each time, it is necessary to use a checkerboard to take several pictures for calibration, making the operation very cumbersome and resulting in a reduction in the efficiency of road surface detection.

[0004] Through the above technical analysis, there are defects in the prior art that the operation is very cumbersome, resulting in a reduction in the efficiency of road surface detection. Summary of the Invention

[0005] Embodiments of the present invention provide a camera calibration system and a calibration method for road surface detection to solve the defects in the prior art that the operation is very cumbersome, resulting in a reduction in the efficiency of road surface detection.

[0006] Embodiments of the present invention provide a camera calibration system for road surface detection, including:

[0007] A ranging sensor module, which is used to measure the distance between the ranging sensor module and the ground;

[0008] A two-dimensional attitude sensor module, which is used to detect the tilt angle of the imaging chip of the camera relative to the ground;

[0009] A calculation module, and both the ranging sensor module and the two-dimensional attitude sensor module are electrically connected to the calculation module.

[0010] The beneficial effect of the camera calibration system for road surface detection of the present invention is that when the ranging sensor module and the two-dimensional attitude sensor module can change with the installation position of the camera, real-time measurement can be performed, and then the external parameter matrix can be calculated quickly in real time through the calculation module, so as to facilitate single calibration and real-time calibration of the external parameters of the camera, without the need for manual complex multiple photo-taking calculations for calibration, reducing the workload of manual operation. The camera calibration system for road surface detection of the present invention can adjust the camera according to the actual needs of road surface detection and perform real-time calibration, with a wide range of applications and high engineering application value.

[0011] Based on the above technical solutions, the present invention can also be improved as follows.

[0012] Further, the ranging sensor module is a laser ranging sensor or an infrared ranging sensor.

[0013] The beneficial effect of adopting the above further solution is: it is convenient to measure the distance from the ground.

[0014] Further, the camera calibration system for road surface detection further includes a communication module, the communication module is used for electrical signal connection with the controller of the camera, and the ranging sensor module, the two-dimensional attitude sensor module and the calculation module are all electrically connected to the communication module.

[0015] The beneficial effect of adopting the above further solution is: it is beneficial for the controller of the camera to send instructions for external parameter calibration, so that manual operation only needs to be performed on the camera.

[0016] Further, the communication module is a Bluetooth module or a WIFI wireless communication module.

[0017] The beneficial effect of adopting the above further solution is: it is beneficial for communication connection.

[0018] Another aspect of the present disclosure provides a calibration method applied to the above camera calibration system for road surface detection, including the following steps:

[0019] The ranging sensor module measures the distance L between the ranging sensor module and the ground;

[0020] The two-dimensional attitude sensor module detects the inclination angle of the imaging chip of the camera relative to the ground;

[0021] According to the distance between the ranging sensor module and the ground and the inclination angle of the imaging chip of the camera relative to the ground, the external parameter matrix M is calculated.

[0022] Further, before the step where the ranging sensor module measures the distance between the ranging sensor module and the ground, it further includes:

[0023] Establish a camera coordinate system and establish a world coordinate system;

[0024] The origin O1 of the camera coordinate system is the focal point in the pinhole imaging model of the camera, the Z1 axis of the camera coordinate system is the optical axis of the camera, and the X1 axis and Y1 axis of the camera coordinate system are parallel to two adjacent sides of the camera imaging chip;

[0025] The origin O2 of the world coordinate system is the intersection point of the camera optical axis and the road surface. The Z2 axis of the world coordinate system is the projection of the camera optical axis on the road surface. The X2 axis of the world coordinate system is perpendicular to the projection of the camera optical axis on the road surface. The Y2 axis of the world coordinate system is parallel to the road surface normal.

[0026] The beneficial effect of adopting the above further scheme is: it is conducive to calculating the coordinate transformation relationship between the camera coordinate system and the world coordinate system, and thus the external parameter calibration of the camera can be obtained.

[0027] Further, the two-dimensional attitude sensor module detects the tilt angle of the imaging chip of the camera relative to the ground, including:

[0028] The two-dimensional attitude sensor module measures the angle P between the Z1 axis of the camera coordinate system and the Y2 axis of the world coordinate system;

[0029] The two-dimensional attitude sensor module measures the angle H between the X1 axis of the camera coordinate system and the X2 axis of the world coordinate system.

[0030] The beneficial effect of adopting the above further scheme is: the tilt angle of the camera installation can be corrected.

[0031] Further, calculating the external parameter matrix M according to the distance between the ranging sensor module and the ground and the tilt angle of the imaging chip of the camera relative to the ground, includes:

[0032] Obtain the first rotation matrix Rx according to the angle P;

[0033] Obtain the second rotation matrix Rz according to the angle H;

[0034] Calculate the rotation matrix R according to the first rotation matrix Rx and the second rotation matrix Rz;

[0035] Obtain the translation matrix t according to the distance L between the ranging sensor module and the ground;

[0036] Determine the coordinate T of the origin O1 of the camera coordinate system in the world coordinate system;

[0037] Obtain the external parameter matrix M according to the rotation matrix R and the translation matrix t.

[0038] The beneficial effect of adopting the above further scheme is: it is conducive to calculating the external parameter matrix.

[0039] Further, the first rotation matrix Rx is

[0040]

[0041] The second rotation matrix Rz is

[0042]

[0043] The rotation matrix R is R = R x R z ;

[0044] The translation matrix t is t = [0 -L×sin P -L×cos P];

[0045] The external parameter matrix M is

[0046] The beneficial effect of adopting the above further solution is: The external parameter matrix can be directly calculated.

[0047] Further, before establishing the camera coordinate system and the world coordinate system, it further includes:

[0048] Receiving a calibration instruction sent by the controller of the camera;

[0049] Sending the calibration instruction to the ranging sensor module, the two-dimensional attitude sensor module and the calculation module.

[0050] The beneficial effect of adopting the above further solution is: It is convenient to directly perform external parameter calibration on the camera, and the operation is more simple and convenient. Description of the Drawings

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0052] Figure 1 Schematic diagram of the positional relationship between the camera coordinate system and the world coordinate system of the present invention;

[0053] Figure 2 Flowchart of the calibration method of the present invention;

[0054] Figure 3 Schematic diagram of the connection relationship of the camera calibration system for road surface detection of the present invention.

[0055] In the drawings, the list of components represented by each label is as follows:

[0056] 1. Camera. Detailed Embodiments

[0057] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0058] As Figure 1 and Figure 3 shown, one aspect of the present disclosure provides a camera calibration system for road surface detection, including: a ranging sensor module, a two-dimensional attitude sensor module, and a calculation module.

[0059] The ranging sensor module is used to measure the distance between the ranging sensor module and the ground. The two-dimensional attitude sensor module is used to detect the tilt angle of the imaging chip of the camera relative to the ground. Both the ranging sensor module and the two-dimensional attitude sensor module are electrically connected to the calculation module.

[0060] Among them, in this embodiment, the ranging sensor module can measure the distance between the ranging sensor module and the ground, and the ranging sensor module is installed at the axis center of the shooting end of the camera, so that the measurement axis of the ranging sensor is parallel or coincident with the optical axis of the camera. Among them, the two-dimensional attitude sensor module has two measurement axes, the two measurement axes are perpendicular to each other, and the two measurement axes are parallel to two adjacent sides of the imaging chip, so that the two measurement axes can measure the tilt angles of two adjacent sides of the imaging chip relative to the ground. The calculation module is used to calculate the external parameter matrix M from the data measured by the ranging sensor module and the data measured by the two-dimensional attitude sensor module, and calibrate the camera through the external parameter matrix M, which is convenient for detecting and analyzing the road surface conditions. Among them, the ranging sensor module, the two-dimensional attitude sensor module, and the calculation module are all used to be installed on the camera.

[0061] In the above technical solution, when the installation position of the camera changes, the ranging sensor module and the two-dimensional attitude sensor module can perform real-time measurement, and then the calculation module can quickly calculate the external parameter matrix in real time, so as to facilitate single calibration and real-time calibration of the external parameters of the camera, without the need for manual complex multiple photo-taking calculations using a checkerboard, reducing the workload of manual operation. This camera calibration system for road surface detection can adjust the camera according to the actual needs of road surface detection and perform real-time calibration, with a wide range of applications and high engineering application value.

[0062] Optionally, in an embodiment of the present disclosure, the ranging sensor module is a laser ranging sensor or an infrared ranging sensor.

[0063] Among them, in this embodiment, the laser ranging sensor uses laser for ranging, and the measuring end of the laser ranging sensor faces the ground. The infrared ranging sensor uses infrared light for ranging, and the measuring end of the infrared ranging sensor also faces the ground. Of course, in some other embodiments, the ranging sensor module can also be other sensors that can achieve ranging.

[0064] Optionally, in an embodiment of the present disclosure, the two-dimensional attitude sensor module is a two-axis tilt angle sensor, which measures the tilt angles between two adjacent sides of the imaging chip and the ground through two measurement axes respectively. Of course, optionally, in other embodiments, the two-dimensional attitude sensor module can also be other sensors that can measure the tilt angles between two adjacent sides of the imaging chip and the ground.

[0065] Optionally, in an embodiment of the present disclosure, the calculation module is a microprocessor, and the microprocessor can perform data calculation.

[0066] Optionally, in an embodiment of the present disclosure, the camera calibration system for road surface detection further includes a communication module, and the communication module is used for electrically connecting with the controller of the camera. The ranging sensor module, the two-dimensional attitude sensor module, and the calculation module are all electrically connected to the communication module.

[0067] Among them, in this embodiment, the communication module is used to transmit control signals. The communication module can establish a communication connection with the controller of the camera, so that the controller of the camera can send signals to the ranging sensor module, the two-dimensional attitude sensor module, and the calculation module, and the ranging sensor module, the two-dimensional attitude sensor module, and the calculation module can perform corresponding operations after receiving the signals. In addition, the external parameter matrix M calculated by the calculation module can also be transmitted back to the controller of the camera through the communication module to realize the external parameter calibration of the camera.

[0068] Optionally, in an embodiment of the present disclosure, the communication module is a Bluetooth module or a WIFI wireless communication module.

[0069] Among them, in this embodiment, when the communication module is a Bluetooth module, the controller of the camera can be Bluetooth-connected to the communication module and can transmit signals in real time. When the communication module is a WIFI wireless communication module, the controller of the camera can establish a WIFI wireless communication connection with the communication module and can send signals conveniently and quickly.

[0070] On the other hand, the present disclosure also provides a calibration method applied to the above-mentioned camera calibration system for road surface detection, including the following steps:

[0071] The ranging sensor module measures the distance L between the ranging sensor module and the ground;

[0072] The two-dimensional attitude sensor module detects the tilt angle of the imaging chip of the camera relative to the ground;

[0073] According to the distance between the ranging sensor module and the ground and the tilt angle of the imaging chip of the camera relative to the ground, the external parameter matrix M is calculated.

[0074] Among them, the distance L is the straight-line distance between the measurement end of the ranging sensor module and the ground. Among them, the two-dimensional attitude sensor module has two measurement axes, the two measurement axes are perpendicular to each other, and the two measurement axes are parallel to two adjacent sides of the imaging chip, so that the two measurement axes can measure the tilt angles of two adjacent sides of the imaging chip relative to the ground.

[0075] Optionally, before the step of the ranging sensor module measuring the distance between the ranging sensor module and the ground, it further includes:

[0076] Establish a camera coordinate system and establish a world coordinate system;

[0077] The origin O1 of the camera coordinate system is the focal point in the pinhole imaging model of the camera, the Z1 axis of the camera coordinate system is the optical axis of the camera, and the X1 axis and Y1 axis of the camera coordinate system are parallel to two adjacent sides of the camera imaging chip;

[0078] The origin O2 of the world coordinate system is the intersection point of the optical axis of the camera and the road surface, the Z2 axis of the world coordinate system is the projection of the optical axis of the camera on the road surface, the X2 axis of the world coordinate system is perpendicular to the projection of the optical axis of the camera on the road surface, and the Y2 axis of the world coordinate system is parallel to the road surface normal.

[0079] Among them, the calibration of the camera external parameters is the conversion relationship between the camera coordinate system and the world coordinate system, that is, by calculating the external parameter matrix M to facilitate the conversion between the camera coordinate system and the world coordinate system. Among them, the camera coordinate system is located on the camera, and the world coordinate system is located on the ground.

[0080] Optionally, in an implementation manner of the present disclosure, the two-dimensional attitude sensor module detecting the tilt angle of the imaging chip of the camera relative to the ground includes:

[0081] The two-dimensional attitude sensor module measures the included angle P between the Z1 axis of the camera coordinate system and the Y2 axis of the world coordinate system;

[0082] The two-dimensional attitude sensor module measures the included angle H between the X1 axis of the camera coordinate system and the X2 axis of the world coordinate system.

[0083] Among them, in this embodiment, due to the installation of the camera, the camera has a certain rotation angle relative to the ground. As a result, there is a certain included angle between the adjacent two sides of the imaging chip of the camera relative to the ground. The included angle P between the Z1 axis of the camera coordinate system and the Y2 axis of the world coordinate system, and the included angle H between the X1 axis of the camera coordinate system and the X2 axis of the world coordinate system can be obtained through the established camera coordinate system and world coordinate system. The rotation angle of the camera is corrected by measuring the included angles P and H, so as to facilitate the calibration of the external parameters of the camera.

[0084] Optionally, in an embodiment of the present disclosure, calculating the external parameter matrix M according to the distance between the ranging sensor module and the ground and the inclination angle of the imaging chip of the camera relative to the ground includes:

[0085] Obtaining a first rotation matrix Rx according to the included angle P;

[0086] Obtaining a second rotation matrix Rz according to the included angle H;

[0087] Calculating a rotation matrix R according to the first rotation matrix Rx and the second rotation matrix Rz;

[0088] Obtaining a translation matrix t according to the distance L between the ranging sensor module and the ground;

[0089] Determining the coordinates T of the origin O1 of the camera coordinate system in the world coordinate system;

[0090] Obtaining the external parameter matrix M according to the rotation matrix R and the translation matrix t.

[0091] Optionally, in an embodiment of the present disclosure, the first rotation matrix Rx is

[0092]

[0093] The second rotation matrix Rz is

[0094]

[0095] The rotation matrix R is R = R x R z ;

[0096] The translation matrix t is t = [0 -L×sin P -L×cos P];

[0097] The external parameter matrix M is

[0098] Optionally, in an embodiment of the present disclosure, before establishing the camera coordinate system and the world coordinate system, it further includes:

[0099] The communication module receives a calibration instruction issued by the controller of the camera;

[0100] The communication module sends the calibration instruction to the ranging sensor module, the two-dimensional attitude sensor module, and the calculation module.

[0101] Among them, in this embodiment, after the camera is installed, the communication module is electrically connected to the controller of the camera. The operator can operate the camera to enter the external parameter calibration mode. At this time, the controller of the camera sends a calibration instruction to the communication module, and the communication module distributes the instruction to the ranging sensor module, the two-dimensional attitude sensor module, and the calculation module for external parameter calibration.

[0102] As Figure 2 shown, the calibration method of the camera calibration system for road surface detection includes the following steps:

[0103] S201. The communication module receives a calibration instruction issued by the controller of the camera.

[0104] S202. The communication module sends the calibration instruction to the ranging sensor module, the two-dimensional attitude sensor module, and the calculation module.

[0105] S203. Establish a camera coordinate system and establish a world coordinate system.

[0106] S204. The ranging sensor module measures the distance L between the ranging sensor module and the ground.

[0107] S2051. Measure the angle P between the Z1 axis of the camera coordinate system and the Y2 axis of the world coordinate system.

[0108] S2052. Measure the angle H between the X1 axis of the camera coordinate system and the X2 axis of the world coordinate system.

[0109] S206. Calculate the external parameter matrix M.

[0110] S2061. Obtain the first rotation matrix Rx according to the angle P,

[0111]

[0112] S2062. Obtain the second rotation matrix Rz according to the angle H,

[0113]

[0114] S2063. Calculate the rotation matrix R according to the first rotation matrix Rx and the second rotation matrix Rz,

[0115] R = R x Rz 。

[0116] S2064. Obtain the translation matrix t based on the distance L between the ranging sensor module and the ground.

[0117] t = [0 -L×sin P -L×cos P];

[0118] S2065. Determine the coordinates T of the origin O1 of the camera coordinate system in the world coordinate system.

[0119] S2066. Obtain the external parameter matrix M based on the rotation matrix R and the translation matrix t.

[0120]

[0121] S207. After the calculation module calculates the external parameter matrix M, it sends it to the communication module, and the communication module sends it to the controller of the camera to complete the calibration of the external parameters of the camera.

[0122] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A camera calibration system for road surface detection, characterized in that, Including: A ranging sensor module for measuring the distance L between the ranging sensor module and the ground; A two-dimensional attitude sensor module for detecting the tilt angle of the imaging chip of the camera relative to the ground; A calculation module, where both the ranging sensor module and the two-dimensional attitude sensor module are electrically connected to the calculation module. According to the distance between the ranging sensor module and the ground and the tilt angle of the imaging chip of the camera relative to the ground, an external parameter matrix M is calculated; Establishing a camera coordinate system and a world coordinate system; The origin O1 of the camera coordinate system is the focal point in the pinhole imaging model of the camera. The Z1 axis of the camera coordinate system is the optical axis of the camera. The X1 axis and Y1 axis of the camera coordinate system are parallel to two adjacent sides of the camera imaging chip; The origin O2 of the world coordinate system is the intersection point of the camera optical axis and the road surface. The Z2 axis of the world coordinate system is the projection of the camera optical axis on the road surface. The X2 axis of the world coordinate system is perpendicular to the projection of the camera optical axis on the road surface. The Y2 axis of the world coordinate system is parallel to the road surface normal; The two-dimensional attitude sensor module detects the tilt angle of the imaging chip of the camera relative to the ground, including: The two-dimensional attitude sensor module measures the angle P between the Z1 axis of the camera coordinate system and the Y2 axis of the world coordinate system; The two-dimensional attitude sensor module measures the angle H between the X1 axis of the camera coordinate system and the X2 axis of the world coordinate system; Calculating the external parameter matrix M according to the distance between the ranging sensor module and the ground and the tilt angle of the imaging chip of the camera relative to the ground, including: Obtaining a first rotation matrix Rx according to the angle P; Obtaining a second rotation matrix Rz according to the angle H; Calculating a rotation matrix R according to the first rotation matrix Rx and the second rotation matrix Rz; Obtaining a translation matrix t according to the distance L between the ranging sensor module and the ground; Determining the coordinates T of the origin O1 of the camera coordinate system in the world coordinate system; Obtaining the external parameter matrix M according to the rotation matrix R and the translation matrix t; The first rotation matrix Rx is ； The second rotation matrix Rz is ； The rotation matrix R is ; The translation matrix t is ; The external parameter matrix M is .

2. The camera calibration system for road surface detection according to claim 1, characterized in that, The ranging sensor module is a laser ranging sensor or an infrared ranging sensor.

3. The camera calibration system for road surface detection according to claim 1, characterized in that, The camera calibration system for road surface detection further includes a communication module for electrically connecting to the controller of the camera. The ranging sensor module, the two-dimensional attitude sensor module, and the calculation module are all electrically connected to the communication module.

4. The camera calibration system for road surface detection according to claim 3, characterized in that, The communication module is a Bluetooth module or a WIFI wireless communication module.

5. A calibration method applied to the camera calibration system for road surface detection according to any one of claims 1-4, characterized in that, Including the following steps: The ranging sensor module measures the distance L between the ranging sensor module and the ground; The two-dimensional attitude sensor module detects the tilt angle of the imaging chip of the camera relative to the ground; Calculating the external parameter matrix M according to the distance between the ranging sensor module and the ground and the tilt angle of the imaging chip of the camera relative to the ground; Before the step where the ranging sensor module measures the distance between the ranging sensor module and the ground, it further includes: Establishing a camera coordinate system and a world coordinate system; The origin O1 of the camera coordinate system is the focal point in the pinhole imaging model of the camera. The Z1 axis of the camera coordinate system is the optical axis of the camera, and the X1 axis and Y1 axis of the camera coordinate system are parallel to two adjacent sides of the camera imaging chip; The origin O2 of the world coordinate system is the intersection point of the camera optical axis and the road surface. The Z2 axis of the world coordinate system is the projection of the camera optical axis on the road surface. The X2 axis of the world coordinate system is perpendicular to the projection of the camera optical axis on the road surface, and the Y2 axis of the world coordinate system is parallel to the road surface normal; The two-dimensional attitude sensor module detects the tilt angle of the camera imaging chip relative to the ground, including: The two-dimensional attitude sensor module measures the angle P between the Z1 axis of the camera coordinate system and the Y2 axis of the world coordinate system; The two-dimensional attitude sensor module measures the angle H between the X1 axis of the camera coordinate system and the X2 axis of the world coordinate system; According to the distance between the ranging sensor module and the ground and the tilt angle of the camera imaging chip relative to the ground, the external parameter matrix M is calculated, including: Obtaining the first rotation matrix Rx according to the angle P; Obtaining the second rotation matrix Rz according to the angle H; Calculating the rotation matrix R according to the first rotation matrix Rx and the second rotation matrix Rz; Obtaining the translation matrix t according to the distance L between the ranging sensor module and the ground; Determining the coordinates T of the origin O1 of the camera coordinate system in the world coordinate system; Obtaining the external parameter matrix M according to the rotation matrix R and the translation matrix t; The first rotation matrix Rx is ； The second rotation matrix Rz is ； The rotation matrix R is ; The translation matrix t is ; The external parameter matrix M is .

6. According to the calibration method described in claim 5, characterized in that, Before establishing the camera coordinate system and the world coordinate system, it further includes: Receiving a calibration instruction sent by the controller of the camera; Sending the calibration instruction to the ranging sensor module, the two-dimensional attitude sensor module, and the calculation module.

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