Surveillance camera external parameter calibration device and method

Abstract

The invention discloses a monitoring camera external parameter calibration device and method, and the device comprises calibration equipment which is disposed at a ground position which can be shot by a monitoring camera lens. And the measuring equipment is arranged relative to the calibration equipment. And the external parameter calibration calculation equipment is in wired or wireless connection with the monitoring camera. And an external parameter calibration calculation program is built in the external parameter calibration calculation equipment. The method for calibrating the external parameters by adopting the device comprises the following steps of: initializing the external parameter calibration device; measuring the world coordinates of the system establishing points; measuring image coordinates and world coordinates of the control points; measuring world coordinates of verification points; measuring the world coordinates of the system establishing points again; and resolving external parameters of the monitoring camera. According to the monitoring camera external parameter calibration device and method provided by the invention, aiming at a camera for monitoring a busy working place, the calibration of the monitoring camera external parameter is realized without depending on a landmark scene in a monitoring area as a control point, and the effectiveness and the precision of a calibration result are ensured.

Description

Technical Field

[0001] The present invention specifically relates to the field of camera extrinsic parameter calibration, and in particular to a surveillance camera extrinsic parameter calibration device and method. Background Art

[0002] A surveillance camera, also known as a camera or video camera, is an image acquisition device consisting of a lens, a photosensitive device, etc. Some surveillance cameras can change their direction and position, such as a surveillance ball camera, which can rotate along the horizontal or vertical plane to change its direction. Some video acquisition devices are composed of multiple surveillance cameras, such as a gun-ball all-in-one camera, which is composed of a fixed-focus surveillance camera and a zoom surveillance camera.

[0003] Since the camera surveillance area has a single scene and a large field of view, the size of a single pixel corresponding to the physical world is large, and it is impossible to find a sufficient number of feature points as control points in the surveillance area. The camera surveillance area is a busy workplace, and people and equipment will move or stay in the surveillance area, resulting in the inability to ensure that the total station has line of sight with the point to be measured; at the same time, the positions suitable for laying target plates or target blocks and the positions suitable for setting up total stations are often occupied, prohibited from entry or temporarily occupied. During the calibration process, the total station bracket may be accidentally touched, causing a slight change in the position of the total station; or due to external factors such as sunlight and temperature rise, the surveillance area may gradually undergo slight deformation, which will lead to invalid coordinates measured by the total station. Considering that external parameter calibration involves multiple people operating multiple devices in coordination, and the on-site situation is complicated, there may be unknown factors that make the solved external parameters invalid or have large errors. In summary, the external parameter calibration of cameras monitoring busy workplaces faces six key issues: 1) How to deploy a sufficient number of control points that are evenly distributed in the monitoring area and clearly visible in the monitoring image; 2) How to ensure that the total station deployment position is not occupied; 3) How to ensure that there is always line of sight between the total station and the points to be measured; 4) How to check the validity of the coordinates measured by the total station; 5) How to check the validity of the solved external parameters; 6) How to check the errors of the solved external parameters.

[0004] In the problem of airport assisted collision avoidance, in view of the difficulty of limited number of feature points in the airport environment, Zhao Zhe proposed a camera extrinsic parameter calibration method of "optical center + four control points" in "Research on video measurement technology in collision avoidance auxiliary facilities of airport transportation system". This method reduces the number of control points required, and the accuracy error of the calibrated extrinsic parameters is within the allowable range. However, it does not take into account the slight deformation of the monitored area due to temperature increase, the movement of workers or equipment in the monitored area affecting the total station layout and line of sight; at the same time, it does not consider how to check the validity of the coordinates measured by the total station, and the validity of the solved external parameters.

[0005] The invention patent with the publication number "CN109087360A" proposes a robot camera external parameter calibration method, which needs to combine the indoor map with the robot laser positioning system to determine the position of the feature object, and is more suitable for indoors or areas with known maps. However, when the surveillance camera is fixedly installed at a high place outdoors and the surveillance range is large, it is difficult to obtain a map of its surveillance area.

[0006] The invention patent with the publication number "CN105957096A" proposes a camera extrinsic calibration method for three-dimensional digital images. The goal of this method is to calibrate the relative extrinsic parameters of two cameras. The speckle or its natural texture on the surface of the test sample is the key to this method. However, considering that the camera monitoring area is large, the scene is single, and there is only partial overlap between adjacent cameras, it is difficult to find natural textures or artificially arranged speckles.

[0007] The invention patent with publication number "CN108805936A" proposes a camera extrinsic calibration method based on four control points, which is simple and efficient. However, in order to calibrate the extrinsic parameters of the camera monitoring a busy workplace, it is necessary to focus on how to deploy a sufficient number of control points that are evenly distributed in the monitoring area and clearly visible in the monitoring image, how to ensure that the deployment position of the total station is not occupied, how to ensure that the total station and the point to be measured always maintain line of sight, how to check the validity of the coordinates measured by the total station, how to check the validity of the solved extrinsic parameters and how to check the errors of the solved extrinsic parameters. This method does not involve solutions to the above problems. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a surveillance camera extrinsic parameter calibration device and method, which is aimed at cameras monitoring busy workplaces. It does not rely on landmark scenes in the monitoring area as control points, realizes the calibration of surveillance camera extrinsic parameters, and ensures the effectiveness and accuracy of the calibration results.

[0009] The object of the present invention is to provide a surveillance camera extrinsic parameter calibration device implemented by the following technical scheme, comprising:

[0010] The calibration equipment is set at a ground position that can be photographed by the surveillance camera lens.

[0011] Measuring equipment, set relative to the calibration equipment.

[0012] The external parameter calibration computing device is connected to the surveillance camera by wire or wirelessly.

[0013] The external parameter calibration calculation device has a built-in external parameter calibration calculation program.

[0014] Preferably, the calibration device includes a light source and a calibration component.

[0015] Preferably, the calibration assembly includes a calibration plate and a calibration block.

[0016] Preferably, the measuring device includes at least a total station and a light source.

[0017] Preferably, the measuring device and the calibration device can be connected to the external parameter calibration calculation device respectively by wire or wirelessly.

[0018] Preferably, the external parameter calibration computing device includes at least a computer.

[0019] In addition to providing a surveillance camera extrinsic parameter calibration device, the present invention further provides a surveillance camera extrinsic parameter calibration method using the calibration device, which specifically includes the following steps:

[0020] Step 1: Initializing the external parameter calibration device: at least including connecting the camera and making a control point distribution map;

[0021] Step 2: Measure the world coordinates of the system establishment point;

[0022] Step 3, measuring the image coordinates and world coordinates of the control points;

[0023] Step 4: Verify point world coordinate measurement;

[0024] Step 5: Measure the world coordinates of the system establishment point again;

[0025] Step 6: Calculate the external parameters of the surveillance camera.

[0026] Preferably, in step 1, the steps for making the control point distribution map are as follows: take a screenshot of the camera video screen, and evenly select at least M solution points and N test points in the monitoring area to mark them as a control point distribution map, where the number of M and N is at least 4.

[0027] Preferably, in step 2, the coordinates of the system establishment points are measured using a target block-based measurement method.

[0028] Preferably, step 6 at least includes the following steps:

[0029] Step 6.1: Check the validity of the world coordinates for each system establishment point;

[0030] Step 6.2, solve the external parameters to obtain the world coordinates of the imaging optical center of the surveillance camera;

[0031] Step 6.3: Check the validity of the extrinsic parameters calculated in step 6.2. If they meet the validity criteria, proceed to step 6.3. If they do not meet the validity criteria, recalibrate the camera extrinsic parameters.

[0032] Step 6.4: Calculate the error of the extrinsic parameter. If the error of the extrinsic parameter is within an acceptable range, the error is considered acceptable. Otherwise, if the error is too large, recalibrate the camera extrinsic parameter.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] The present invention provides a surveillance camera external parameter calibration device and method. The method first initializes the external parameter calibration device, including a commander making a control point distribution map of the camera, a surveyor laying out a total station and making measurement preparations, and an operator holding a target plate and a target block to a predetermined position; then measuring the world coordinates of the establishment point; then measuring the world coordinates and image coordinates of the control point, measuring the world coordinates of the verification point, and measuring the world coordinates of the establishment point; finally, solving the external parameters and calculating the error. The present invention is aimed at cameras monitoring busy workplaces. It does not rely on landmarks in the monitoring area as control points, avoids the influence of deformation of the monitoring area caused by sunlight heating, and can check the validity of the coordinates measured by the total station and the validity of the solved external parameters. The calibration process is more robust, and the validity and accuracy of the calibration results are more guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the composition of the external parameter calibration device of the surveillance camera in an embodiment of the present invention;

[0036] Figure 2 This is a flow chart of a method for calibrating external parameters of a surveillance camera in an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of control point distribution in an embodiment of the present invention;

[0038] Figure 4 This is a schematic diagram of target plate marking space points in an embodiment of the present invention;

[0039] Figure 5 Schematic diagram of target block identification space points in an embodiment of the present invention.

[0040] In the figure, 1 is the calibration equipment; 2 is the measuring equipment; 3 is the external parameter calibration computer; and 4 is the surveillance camera. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0042] The technical solution of the present invention provides a surveillance camera extrinsic parameter calibration device, comprising:

[0043] The calibration equipment is set at a ground position that can be photographed by the surveillance camera lens.

[0044] Measuring equipment, set relative to the calibration equipment.

[0045] The external parameter calibration computing device is connected to the surveillance camera by wire or wirelessly.

[0046] The external parameter calibration calculation device has a built-in external parameter calibration calculation program.

[0047] In one embodiment of the present invention, the calibration device includes a light source and a calibration component, wherein the calibration component includes a calibration plate and a calibration block, and the calibration device is connected to the external parameter calibration calculation device by wire or wirelessly, or may not be connected.

[0048] In one embodiment of the present invention, the measuring device includes at least a total station and a light source, and the measuring device is connected to the external parameter calibration calculation device by wire or wirelessly, or may not be connected.

[0049] In one embodiment of the present invention, the external parameter calibration calculation device at least includes a computer. There are two ways for the external parameter calibration computer to perform external parameter calculation. First, when the measuring device and the calibration device are respectively connected to the external parameter calibration computer by wire or wireless, the external parameter calibration computer collects the video images shot by the surveillance camera in real time on the one hand, and sends a control signal to the calibration device to control the movement of the calibration device on the other hand, and collects the world coordinates of the system establishment points, control points and verification points measured by the measuring device in real time, so as to facilitate the collection of the positions of each control point in the control point distribution map.

[0050] The second method is that when the measuring device and the calibration device are not connected to the external parameter calibration computer, the calibration device can be moved manually, and the world coordinates of the establishment points, control points and verification points measured by the measuring device can be manually recorded. Then the above information is entered into the external parameter calibration computer for external parameter calibration solution.

[0051] In addition to providing a surveillance camera extrinsic parameter calibration device, the technical solution of the present invention further provides a method for calibrating the extrinsic parameters of a surveillance camera using the calibration device, which specifically includes the following steps:

[0052] Step 1: Initializing the external parameter calibration device: at least including connecting the camera and making a control point distribution map;

[0053] Step 2: Measure the world coordinates of the system establishment point;

[0054] Step 3, measuring the image coordinates and world coordinates of the control points;

[0055] Step 4: Verify point world coordinate measurement;

[0056] Step 5: Measure the world coordinates of the system establishment point again;

[0057] Step 6: Calculate the external parameters of the surveillance camera.

[0058] In one embodiment of the present invention, in step 1, the steps for making a control point distribution map are as follows: take a screenshot of the camera video screen, and evenly select at least M solution points and N test points in the monitoring area to mark them as a control point distribution map, where the number of M and N is at least 4.

[0059] In one embodiment of the present invention, in step 2, the coordinates of the system establishment point are measured using a target block-based measurement method.

[0060] In one embodiment of the present invention, step 6 at least includes the following steps:

[0061] Step 6.1: Check the validity of the world coordinates for each system establishment point;

[0062] Step 6.2, solve the external parameters to obtain the world coordinates of the imaging optical center of the surveillance camera;

[0063] Step 6.3: Check the validity of the extrinsic parameters calculated in step 6.2. If they meet the validity criteria, proceed to step 6.3. If they do not meet the validity criteria, recalibrate the camera extrinsic parameters.

[0064] Step 6.4: Calculate the error of the external parameter. If the error of the external parameter is within the acceptable range, the error is considered acceptable. Otherwise, if the error is too large, recalibrate the camera external parameter.

[0065] The following is a further description of the external parameter calibration method for surveillance cameras provided in the technical solution of the present invention through an example. In this embodiment, the external parameter calibration device is as follows: Figure 1 As shown, manual operation is adopted:

[0066] It includes target plate, target block, control point distribution map, total station, measurement result record book, internal reference calibration computer, intercom (for communication) and flashlight (for light source); it is operated by 1 commander, 2 operators and 1 surveyor. Figure 1As shown, 1 is a calibration device, 2 is a measuring device, 3 is an external parameter calibration computer, and 4 is a surveillance camera. In this embodiment, the surveillance camera 4 is fixedly installed on a high-rise building. The external parameter calibration computer 3 is connected to the surveillance camera 4 through a network cable. The commander operates the external parameter calibration computer 3, obtains the real-time video shot by the surveillance camera 4, and communicates with the surveyor and the operator by holding a walkie-talkie. In this embodiment, the calibration device 1 is a target plate and a target block, and the measuring device 2 is a total station, which is fixedly mounted at a suitable position. The surveyor uses the total station to measure the world coordinates of the establishment point, control point and verification point and records them in the measurement result record book, and keeps in touch with the commander and the operator through the walkie-talkie. Under the command of the commander, two operators (operators A and B) move the target plate to the designated control point according to the position marked in the control point distribution map. Operator B keeps in touch with the commander and the surveyor by holding a walkie-talkie.

[0067] Since the external parameter calibration is mainly carried out outdoors, especially when it involves the use of a total station, there must be no bad weather such as rain, snow, fog, etc. Considering that the target plate needs to be placed vertically to measure the coordinates of the control points in the edge area of ​​the field of view, it is necessary to work under windless conditions to avoid the target plate from shaking. In order to ensure that the target plates are arranged at all control points, the total station has line of sight with the control points, and at the same time avoid deformation of the field of view area caused by heating due to sunlight, it is chosen to work at night. In addition, the camera intrinsic parameters are the input for solving the external parameters, and the camera intrinsic parameters are required to be known and remain unchanged throughout the external parameter calibration process. Finally, the camera extrinsic parameters are required to remain unchanged throughout the external parameter calibration process.

[0068] like Figure 2 As shown, the specific steps of using the above method to calibrate the external parameters of the surveillance camera are as follows:

[0069] Step 1: Initialize the external parameter calibration device:

[0070] Step 1.1, connect the camera: connect the external parameter calibration computer to the camera and obtain the camera's video image;

[0071] Step 1.2, make a control point distribution map: the commander takes a screenshot of the camera video screen, evenly selects at least M solution points and N test points in the monitoring area, and makes a control point distribution map, where the number of solution points and test points is at least 4;

[0072] Step 1.3, operator takes position: the operator arrives at the first control point with the control point distribution map, target board, target block, flashlight and walkie-talkie;

[0073] Step 1.4, Surveyor in place: The surveyor takes into account the distribution of control points, on-site conditions and other factors, selects a location where all control points, verification points and establishment points can be viewed, sets up the total station, sets the measurement parameters, and prepares for the measurement;

[0074] Step 1.5: Confirm that communication is normal: The commander, surveyor and operator confirm that communication is normal and report to each other that "preparation work has been completed."

[0075] Step 2: Measure the world coordinates of the system establishment point. The system establishment point is a point used to construct the world coordinate system. In this embodiment, the coordinates of the system establishment point are measured using a target block-based measurement method. The specific steps are as follows:

[0076] Step 2.1, target block in place: the operator places the target block on the ground so that the center point of the target block is directly above the system construction point A, and rotates the target block along the Z axis of the world coordinate system so that the center point of the target block faces the surveyor;

[0077] Step 2.2, notify the start of measurement: the operator illuminates the target block with a flashlight and informs the surveyor to start measuring the establishment point A;

[0078] Step 2.3, measure the world coordinates: the surveyor measures the coordinates of the system point A in the "reflector" mode and enters the results into the measurement result record book;

[0079] Step 2.4, measure the world coordinates of other system building points: Repeat steps 2.1 to 2.3 to measure the coordinates of other system building points in turn.

[0080] Step 3: Measure the image coordinates and world coordinates of the control points. In this embodiment, the control points include two types: one is the solution point, which is used to solve the camera extrinsic parameters; the other is the test point, which is used to calculate the extrinsic parameter error. Both types of control points need to measure the image coordinates and world coordinates, and no distinction is made between the two types of points during the coordinate measurement process. The steps for measuring the image coordinates and world coordinates of the control points are as follows:

[0081] Step 3.1, determine the measurement method: for control point 1, the operator, commander and surveyor coordinate to determine a measurement method (target plate-based measurement method or target block-based measurement method);

[0082] Step 3.2, target in place: the operator places the target plate (or target block) at the corresponding position, illuminates the target plate (or target block) with a flashlight, and informs the surveyor and commander to start measuring the coordinates;

[0083] Step 3.3, measuring image coordinates: The commander measures the image coordinates of control point 1 through the external parameter calibration computer, and notifies the surveyor and operator that "the image coordinate measurement of control point 1 is completed";

[0084] Step 3.4, measure world coordinates: The surveyor uses the total station to measure the world coordinates of control point 1, enters the measurement result into the record book, and informs the commander and operator that "the world coordinate measurement of control point 1 is completed";

[0085] Step 3.5, move to the next control point: After both the image coordinates and the world coordinates of control point 1 are measured, the operator moves to the position of the next control point;

[0086] Step 3.6, measure other control points: Repeat steps 3.1 to 3.5 to complete the measurement of the remaining control points.

[0087] Step 4: Verify the world coordinates of the point. The verification point is any point on the camera lens, which is used to verify the validity of the solved external parameters. The steps to measure the world coordinates of the verification point are as follows:

[0088] Step 4.1, start measuring: the commander issues a command to start measuring the camera verification point;

[0089] Step 4.2, illuminate the camera: The operator illuminates the camera with a flashlight to indicate the location of the target camera to the surveyor;

[0090] Step 4.3, measure world coordinates: The surveyor adjusts the total station to the "arbitrary object surface" mode, measures the world coordinates of the camera lens, enters them into the geodetic coordinate record book, and notifies the commander and operator that "verification point measurement is completed."

[0091] Step 5: Measure the world coordinates of the system establishment point again:

[0092] The coordinates of the establishment points measured for the first time are used to construct the world coordinate system. The coordinates of the establishment points measured again are used to check the validity of all coordinates measured by the total station. Measure the world coordinates of the establishment points again according to the above steps and enter them into the measurement result log. At this point, the measurement of all coordinates of all points in this external parameter calibration is completed.

[0093] Step 6: Calculate the external parameters of the surveillance camera. Take the image coordinates or world coordinates of each point measured by the camera internal parameters as input, use the external parameters to calibrate the computer, check the validity of the world coordinates of each point and calculate the external parameters and their errors. The main steps are as follows:

[0094] Step 6.1, world coordinate validity check: for each point, compare the difference between the two coordinates before and after. If the maximum difference is greater than d (generally d = 2cm), it means that the world coordinates of each point are based on different coordinate systems. The world coordinates measured this time are invalid and the camera extrinsics should be recalibrated.

[0095] Step 6.2, external parameter solution: If the world coordinates of each point are valid, solve the external parameters based on the solvePnP function of opencv to obtain the world coordinates of the camera imaging optical center;

[0096] Step 6.3, check the validity of external parameters: calculate the distance between the imaging optical center and the verification point. If the distance is greater than the length of the longest dimension of the minimum bounding box of the camera body, the solved external parameters are considered invalid and the camera external parameters should be recalibrated.

[0097] Step 6.4, check the error of external parameters: solve the image coordinates of the test point based on the projectPoints function of opencv, and calculate the error of the solved external parameters. If the error is less than p (generally set p = 5 pixels), it indicates that the error of the external parameters is within an acceptable range. Otherwise, the error is judged to be too large and the camera extrinsic parameters should be recalibrated.

[0098] In this embodiment, the input and output are:

[0099] Input: Camera intrinsic parameters;

[0100] 1. Initialization of the external parameter calibration system

[0101] 2. World coordinate measurement of system points

[0102] 3. Control point image coordinates and world coordinates measurement

[0103] 4. Verification point world coordinate measurement

[0104] 5. Re-measure the world coordinates of the system point

[0105] 6. External parameter calculation

[0106] Output: Camera extrinsics and their errors.

[0107] In this embodiment, the terms are explained as follows:

[0108] World coordinate system: used for calibrating external parameters of surveillance cameras. It is a three-dimensional right-handed coordinate system. Generally, the x-axis and y-axis are parallel to the earth, and the z-axis is vertically upward. The units of the three axes are meters.

[0109] Surveillance camera extrinsic parameters: are the coordinates of the surveillance camera imaging optical center in the world coordinate system, usually described by the rotation and translation of the world coordinate system origin to the surveillance camera coordinate system (a rotation matrix and a translation matrix). Once the direction or position of the surveillance camera changes, the extrinsic parameters will also change.

[0110] Surveillance camera extrinsic calibration: the process of solving the extrinsic parameters of a surveillance camera.

[0111] System construction points: A set of points used to construct the world coordinate system. Generally, at least 2 points are used to construct the x-axis, at least 2 points are used to construct the y-axis, and 1 point is used to construct the origin. Figure 1 shown.

[0112] Control point: A set of points in the field of view of a surveillance camera, divided into two categories: solution points and test points. In order to calibrate a surveillance camera, it is necessary to take a number of solution points and test points in its field of view, and measure the image coordinates and world coordinates of each control point.

[0113] Solution point: A type of control point used to solve the external parameters of the surveillance camera.

[0114] Test point: A type of control point used to calculate extrinsic parameter errors.

[0115] Control point distribution map: A screenshot of the surveillance camera video with the control point locations marked, such as Figure 3 As shown, the red points indicate the locations of the solution points, and the blue points indicate the locations of the test points.

[0116] Verification point: It is any point on the surveillance camera lens, which is used to check the validity of the solved external parameters.

[0117] Target board: It is a hard board with a target pattern drawn on its surface. The center of the target pattern (also called the center of the target board) is used to mark the position of the spatial point. Examples of target boards marking spatial points include Figure 4 As shown, a 2×2 black and white checkerboard pattern is sprayed on the surface of the target board, and a reflector is attached to the center of the pattern. The center of the reflector coincides with the center of the target pattern, which is used to mark the position of the spatial point.

[0118] The measurement method based on the target board is a method of measuring the world coordinates or image coordinates of a spatial point. The target board is used to mark the position of the spatial point, and the world coordinates of the center of the target board are measured by the total station as the world coordinates of the spatial point, and the image coordinates of the center of the target board are measured as the image coordinates of the spatial point. Special attention should be paid to the fact that the field of view of the surveillance camera is large, and the oblique angle of the surveillance camera's line of sight at the edge of the field of view is large, so it is impossible to measure the image coordinates of the target board placed flat on the ground. At this time, the target board needs to be placed vertically, such as Figure 4 shown.

[0119] Target block: It is a metal block with a target pattern drawn on its surface. The center of the target pattern (also called the target block center) is used to mark the position of the spatial point. Figure 5 The figure shows an example of a target block identifying a spatial point.

[0120] Target block-based measurement method: It is a method of measuring the world coordinates or image coordinates of a spatial point. The target block is used to mark the position of the spatial point. The world coordinates of the center of the target block are measured by a total station as the world coordinates of the spatial point, and the image coordinates of the center of the target block are measured as the image coordinates of the spatial point. Figure 5 shown.

[0121] The method for calibrating the external parameters of surveillance cameras provided in the technical solution of the present invention is suitable for nighttime operation, so as to solve the problem of calibrating the external parameters of cameras monitoring busy workplaces. Considering that the temperature decreases at night, the deformation of the monitored area gradually recovers, which can avoid the invalid world coordinates caused by regional deformation. Work stops at night, and there are no workers or equipment moving in the monitored area, so control points can be easily arranged in the monitored area. Therefore, it is chosen to perform external parameter calibration at night. In order to check the validity of the coordinates measured by the total station, the same batch of points are measured at the beginning and end of the calibration, and the validity of the measured coordinates is judged by checking the difference between the coordinates of the two batches of points. Considering that the camera external parameters are the world coordinates of the camera imaging optical center, the validity of the external parameters is judged by checking the distance between a certain point on the camera lens and the imaging optical center. In order to calculate the external parameter error, a part of the control points is used as test points, and the test points are back-projected to the image coordinate system based on the solved external parameters, and the pixel difference of the test points is used as the external parameter error.

[0122] Taking into account the safety of night operations and to facilitate commanders and measurements to find the approximate position of the target plate or target block, luminous tape is affixed to the outside of the operator's clothes.

[0123] When the calibration device and the measuring device are connected to the external parameter calibration calculation device by wire or wirelessly, except for the measurement data transmission method, the remaining steps are consistent with the steps in the above embodiment and will not be repeated here.

[0124] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A surveillance camera extrinsic parameter calibration device, characterized in that: The device comprises: The calibration equipment is set at a ground position that can be photographed by the surveillance camera lens. Measuring equipment, set relative to the calibration equipment. The external parameter calibration computing device is connected to the surveillance camera by wire or wirelessly. The external parameter calibration calculation device has a built-in external parameter calibration calculation program.

2. The surveillance camera extrinsic calibration device according to claim 1, characterized in that: The calibration device includes a light source and a calibration component.

3. The surveillance camera extrinsic calibration device according to claim 2, characterized in that: The calibration component includes a calibration plate and a calibration block.

4. The surveillance camera extrinsic calibration device according to claim 3, characterized in that: The measuring device comprises at least a total station and a light source.

5. The surveillance camera extrinsic parameter calibration device according to claim 4, characterized in that: The measuring device and the calibration device can be connected to the external parameter calibration calculation device respectively by wire or wirelessly.

6. The surveillance camera extrinsic calibration device according to claim 5, characterized in that: The external parameter calibration computing device at least includes a computer.

7. A surveillance camera extrinsic parameter calibration method, characterized in that: The calibration device according to any one of claims 1 to 6 is used to calibrate the external parameters of a surveillance camera, specifically comprising the following steps: Step 1: Initializing the external parameter calibration device: at least including connecting the camera and making a control point distribution map; Step 2: Measure the world coordinates of the system establishment point; Step 3, measuring the image coordinates and world coordinates of the control points; Step 4: Verify point world coordinate measurement; Step 5: Measure the world coordinates of the system establishment point again; Step 6: Calculate the external parameters of the surveillance camera.

8. A surveillance camera extrinsic parameter calibration method as claimed in claim 7, characterized in that: In step 1, the steps for making the control point distribution map are as follows: take a screenshot of the camera video screen, evenly select at least M solution points and N test points in the monitoring area to mark them as the control point distribution map, where the number of M and N is at least 4.

9. A surveillance camera extrinsic calibration method as claimed in claim 8, characterized in that: In the step 2, the coordinates of the system establishment points are measured using a target block-based measurement method.

10. A surveillance camera extrinsic calibration method as claimed in claim 9, characterized in that: The step 6 at least comprises the following steps: Step 6.1: Check the validity of the world coordinates for each system establishment point; Step 6.2, solve the external parameters to obtain the world coordinates of the imaging optical center of the surveillance camera; Step 6.3: Check the validity of the extrinsic parameters calculated in step 6.

2. If they meet the validity criteria, proceed to step 6.

3. If they do not meet the validity criteria, recalibrate the camera extrinsic parameters. Step 6.4: Calculate the error of the extrinsic parameter. If the error of the extrinsic parameter is within an acceptable range, the error is considered acceptable. Otherwise, if the error is too large, recalibrate the camera extrinsic parameter.

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