A camera calibration device based on optical measurement

Abstract

The application provides a camera calibration device based on optical measurement, and the device housing is composed of six independent mounting plates; a control module is fixed in the device housing, including an STM32 control board, a Bluetooth module and a wireless module, which supports receiving control instructions through three modes of USB data line, Bluetooth connection and wireless handle; the camera calibration assembly includes a first steering engine, a second steering engine, a third steering engine, a connecting member and a calibration plate, the output shafts of the first steering engine, the second steering engine and the third steering engine are in a two-by-two orthogonal relationship in space, and the orthogonal intersection point of the three shafts is located at the end of the output shaft of the third steering engine; the calibration plate is detachably installed on the metal steering disc of the output shaft of the third steering engine; the STM32 control board is electrically connected with the three steering engines, used for analyzing the control instructions and driving the corresponding steering engines to rotate, and then driving the calibration plate to produce rotary motion around the three orthogonal directions. The application has good portability and simple and flexible operation.

Description

Technical Field

[0001] This invention relates to optical measurement technology, and more particularly to a camera calibration device based on optical measurement. Background Technology

[0002] In image measurement processes and machine learning vision applications, such as grating projection measurement and binocular camera measurement technology, camera calibration is required. Camera calibration is a key technology that aims to accurately determine the camera's intrinsic and extrinsic parameters.

[0003] The common design concept of frame-type camera calibration devices today is to fix the calibration plate on a specific frame and perform calibration operations by manually controlling the calibration plate. This type of calibration device is simple to operate, but it has disadvantages such as low automation and low accuracy. Therefore, a high-precision automated camera calibration device has become a demand. Summary of the Invention

[0004] The purpose of this invention is to provide a camera calibration device based on optical measurement.

[0005] The technical solution for achieving the objective of this invention is: a camera calibration device based on optical measurement, comprising:

[0006] The outer casing (1) of the device is composed of six independent mounting plates, including an upper side plate, a lower side plate, a left side plate, a right side plate, a front side plate and a rear side plate, and the mounting plates are fixedly connected by screws.

[0007] The control module is fixed inside the device housing (1) and includes an STM32 control board, a Bluetooth module and a wireless module. The STM32 control board integrates a Bluetooth module and a wireless module and is equipped with a USB interface for wired connection, so that the control module can simultaneously support receiving control commands through three methods: USB data cable, Bluetooth connection and wireless handle.

[0008] The camera calibration assembly (3) includes a first servo (32), a second servo (33), a third servo (34), a connecting member (31), and a calibration plate (36). The body of the first servo (32) is fixed to the lower surface of the upper side plate by screws, and its output shaft passes vertically upward through the servo mounting slot (105) opened on the upper side plate. The connecting member (31) includes a mounting bracket (311) and two L-shaped connectors (312). The two ends of the mounting bracket (311) are respectively connected to the first servo (32) by screws. 32) The metal servo disk (35) mounted on the output shaft of the second servo (33) is fixedly connected, and two L-shaped connectors (312) connect the output shaft of the second servo (33) and the third servo (34), so that the output shafts of the first servo (32), the second servo (33) and the third servo (34) are orthogonal to each other in space, and the orthogonal intersection point of the three shafts is located at the end of the output shaft of the third servo (34); the calibration plate (36) is detachably mounted on the metal servo disk (35) of the output shaft of the third servo (34);

[0009] The STM32 control board is electrically connected to three servos and is used to parse control commands and drive the corresponding servos to rotate, thereby causing the calibration board (36) to generate rotational motion around three orthogonal directions.

[0010] Furthermore, the front panel of the device housing (1) is provided with a fan mounting hole (101) and a plurality of heat dissipation holes (102), and the heat dissipation fan (11) is fixed at the fan mounting hole (101) by screws; the rear panel is provided with a first slot (103) and a second slot (104), the power switch and USB interface of the STM32 control board are exposed corresponding to the first slot (103), the second slot (104) is a round hole with threads on the inner wall, and the DC charging interface is installed in the second slot (104) by thread engagement.

[0011] Furthermore, the metal rudder disk (35) includes a first side and a second side opposite to each other. The first side is a cylindrical groove with internal gear teeth. The groove meshes with the gear teeth at the end of the servo output shaft and is locked and fixed by a screw passing through the threaded hole in the center of the metal rudder disk (35) and the threaded hole in the center of the servo output shaft. The second side is disc-shaped, with four other threaded holes evenly distributed on it with the central threaded hole as the center.

[0012] Furthermore, the calibration plate (36) has a mounting hole at its center that corresponds to the threaded hole on the metal rudder disk (35), and is fastened to the metal rudder disk (35) by screws; or, a circular magnet is embedded at the center of the calibration plate (36), and is detachably connected to the metal rudder disk (35) by magnetic attraction.

[0013] Furthermore, the working surface of the calibration plate (36) is printed with a calibration pattern, which is a black and white checkerboard pattern, a symmetrical dot pattern, or a Charuco pattern.

[0014] Furthermore, the lower side plate of the device housing (1) is provided with multiple positioning holes, and the lower ends of multiple mounting pillars (21) are fixed to the positioning holes by screws. The STM32 control board is mounted on the upper end of the mounting pillars (21) by screws, so that the STM32 control board is suspended above the lower side plate.

[0015] Furthermore, the STM32 control board has an initialization program pre-stored. When the device is powered on, it automatically controls the first servo motor (32), the second servo motor (33), and the third servo motor (34) to rotate, adjusting the calibration board (36) to the initial position facing the front of the device.

[0016] Furthermore, during the calibration process, the STM32 control board can record and store in real time the precise control commands that drive the three servos to generate each calibration posture, and generate a series of ordered control commands into an action command file that can be independently stored and called.

[0017] Furthermore, the motion instruction file can be read and executed again by the STM32 control board, thereby enabling the camera calibration device to automatically and accurately repeat a specific pose transformation sequence of the calibration board (36).

[0018] A method for comparing the accuracy of a calibration board using the aforementioned camera calibration device includes the following steps:

[0019] S1: Install the first calibration board on the metal servo disk (35) of the third servo (34), operate the control module to drive the calibration board to complete a set of N preset different pose transformations, and perform image acquisition in each pose. At the same time, save the complete control command sequence that drives these N pose transformations as the first action file.

[0020] S2: Keep the position and absolute orientation of the calibration device in space unchanged, remove the first calibration plate, replace it with the second calibration plate and install it securely;

[0021] S3: Call the first action file and control the module to automatically drive the second calibration board to reproduce N poses in sequence;

[0022] S4: Based on the images acquired by the first calibration board and the second calibration board in the same N poses, camera parameter calibration calculation is performed. By comparing the reprojection error or parameter standard deviation of the two calibration results, the accuracy difference between the two calibration boards is quantitatively evaluated.

[0023] Compared with existing technologies, the significant advantages of this invention are: 1) The calibration board is connected to the metal rudder by screws or magnetic attachment, enabling quick disassembly and replacement, allowing users to use different types of calibration boards (such as checkerboard patterns, symmetrical dots, etc.) according to their needs. Simultaneously, the device's outer shell adopts a modular splicing design, resulting in a compact internal structure and small overall size, overcoming the bulky and inconvenient-to-carry shortcomings of traditional calibration devices and possessing excellent portability. 2) It integrates an STM32 control board, Bluetooth module, and wireless module, creatively supporting three operation modes: wired client connection, wireless handle, and mobile phone Bluetooth. Users can choose the most convenient control terminal according to different experimental environments and usage habits, greatly enhancing the applicability and operational flexibility of the device. 3) This invention not only controls the calibration board's pose changes, but its control program can also record the pose parameters of each calibration board change and generate executable action instruction files. This function allows users to save verified high-precision pose combinations and directly call them in subsequent calibration work, achieving automation of the calibration process, avoiding errors introduced by manual operation, and ensuring the consistency and high precision of the calibration results. 4) Building upon the aforementioned functions, this invention also proposes a novel method for comparing the accuracy of different calibration plates using this device. By fixing the device's position and executing the same set of saved pose motion files, different calibration plates can be tested sequentially. This method effectively eliminates comparison errors caused by differences in pose, enabling a more scientific and accurate evaluation of the performance of different calibration plates. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the camera calibration device described in an embodiment of this application.

[0025] Figure 2 This is an exploded view of the camera calibration component described in an embodiment of this application.

[0026] Figure 3 This is a schematic diagram of the servo motor described in an embodiment of this application.

[0027] Figure 4 This is a schematic diagram of a portion of the mounting plate and mounting support structure of the device housing according to an embodiment of this disclosure.

[0028] Figure 5 This is a schematic diagram of the upper mounting plate structure of the device housing according to an embodiment of this disclosure.

[0029] Explanation of icon numbers:

[0030] 1: Device casing

[0031] 11: Cooling fan

[0032] 101: Fan mounting holes

[0033] 102: Ventilation holes

[0034] 103: First slot

[0035] 104: Second slot

[0036] 105: Servo mounting slot

[0037] 106: Through hole

[0038] 21: Install the support pillars

[0039] 31: Connecting components

[0040] 311: Mounting bracket

[0041] 312: L-shaped connector

[0042] 32: First Servo

[0043] 33: Second servo

[0044] 34: Third servo

[0045] 35: Metal steering wheel

[0046] 36: Calibration plate

[0047] 301: Servo mounting hole Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0049] Example 1

[0050] Reference Figure 1 The present invention provides a camera calibration device based on optical measurement, including a device housing 1, a control module 2 disposed inside the housing, and a camera calibration component 3.

[0051] (1) Device casing 1

[0052] like Figure 4 and Figure 5 As shown, the outer casing 1 of the device is composed of six independent mounting plates, specifically including an upper side plate, a lower side plate, a left side plate, a right side plate, a front side plate, and a rear side plate. The joints of the mounting plates are fixed with screws, forming a complete box structure.

[0053] Front panel: It has a fan mounting hole 101 and multiple heat dissipation holes 102 on its upper part. A cooling fan 11 is fixedly mounted at the fan mounting hole 101 by screws, which together with the heat dissipation holes 102 form a heat dissipation airflow channel.

[0054] Rear panel: It has a rectangular first slot 103 at the top and a circular second slot 104 at the bottom. The first slot 103 is used to expose the control switch and USB wired connection interface of the STM32 control board in the control module 2. The inner wall of the second slot 104 is threaded, and a power charging interface is installed in the hole by means of thread engagement.

[0055] Upper side panel: A servo mounting slot 105 is provided at its center, and a cable passage hole 106 is provided nearby. The servo mounting slot 105 is used to mount and fix the first servo 32 to the fuselage, and the cable passage hole 106 is used for the passage of cables.

[0056] Lower side plate: Multiple positioning holes are provided on its inner side. The lower ends of multiple mounting supports 21 are fixed to these positioning holes by screws to support and fix the STM32 control board, allowing it to be suspended in the air.

[0057] (2) Control Module 2

[0058] The control module 2 is the core control part of the device, including an STM32 control board, a Bluetooth module, and a wireless module integrated on it. This module supports three operation modes: wired connection to a computer terminal via USB data cable, connection to an Android mobile device via Bluetooth, and connection to a matching wireless gamepad via the wireless module. It supports wired computer terminal control, wireless gamepad control, and Android Bluetooth control, and can switch between different operation modes according to different usage scenarios.

[0059] The STM32 control board is mounted on the mounting bracket 21 with screws, located inside the device housing 1 and suspended above the lower side panel, which facilitates airflow and heat dissipation. The control module 2 is connected to three servos, the cooling fan 11, and the power module via cables. The power module supports power supply or charging via the charging interface on the rear side panel.

[0060] (3) Camera calibration component 3

[0061] like Figure 2 As shown, the camera calibration component 3 includes three servos (first servo 32, second servo 33, and third servo 34), a connecting member 31, and a calibration plate 36.

[0062] Servo motors and metal servo discs: such as Figure 3As shown, each servo motor's output shaft has teeth at its end. A metal servo disc 35 is mounted on each output shaft. One side of the metal servo disc 35 has a cylindrical groove with internal teeth, which meshes with the servo motor's output shaft through the teeth; the other side of the metal servo disc 35 is disc-shaped, with multiple threaded holes on its surface, one located in the center and the rest evenly distributed around it. The metal servo disc 35 can be fastened to the servo motor by a screw passing through the central threaded hole and engaging with the threaded hole at the center of the output shaft.

[0063] Connecting Components: The connecting component 31 includes a mounting bracket 311 and two L-shaped connectors 312. The mounting bracket 311 has mounting holes at both ends and is fixedly connected to the metal servo discs 35 of the first servo 32 and the second servo 33 respectively by screws, thereby connecting the two servos together. The two L-shaped connectors 312 are used to connect the second servo 33 and the third servo 34. Through this specific mechanical connection method, the output shafts of the first servo 32, the second servo 33, and the third servo 34 are spatially orthogonal to each other, and the intersection point of these three orthogonal axes is located at the end of the output shaft of the third servo 34.

[0064] Calibration plate: The calibration plate 36 is detachably mounted on the metal servo disk 35 of the third servo 34. In this embodiment, the calibration plate 36 is a black and white checkerboard pattern calibration plate. A mounting hole is provided at the center of the calibration plate 36, and a screw is used to engage with the threaded hole at the center of the metal servo disk 35 for a fixed connection. Alternatively, a circular magnet can be installed at the center of the calibration plate 36 to connect it to the metal servo disk 35 via magnetic attraction for quick replacement.

[0065] (4) Calibration process

[0066] The typical calibration process for this device is as follows:

[0067] Initialization: Turn on the device power, the STM32 control board runs the initialization program, automatically controls the three servos to rotate, and adjusts the calibration board 36 to the initial calibration position facing forward.

[0068] Pose control and image acquisition: The user sends commands via computer terminal, mobile phone, or wireless controller. After receiving the commands, the STM32 control board precisely drives the first servo 32, the second servo 33, and the third servo 34 to rotate. Since the output shafts of the three servos are orthogonally arranged, their rotation can control the calibration board 36 to perform independent or combined angular deflections around three mutually perpendicular axes (e.g., yaw, pitch, and roll). Under each set calibration board pose, the camera to be calibrated takes a picture of the calibration board 36 to acquire a calibration image.

[0069] Data recording and processing: The host computer software (such as a calibration program running on a computer) controls the above process and collects multiple calibration images in different poses. Using these images, feature points (such as checkerboard corner points) are extracted, and algorithms such as the Zhang Zhengyou calibration method are employed to calculate the camera's intrinsic parameters (focal length, principal point coordinates, distortion coefficients, etc.) and extrinsic parameters. At the end of the calibration process, the calibration board can also be reset via the terminal control program.

[0070] Automated Calibration and Reproduction: During a single calibration process, the STM32 control board can record the sequence of servo control commands that drive the calibration board to change its posture and save it as an executable action command file. When the same calibration posture sequence is needed subsequently, this file can be directly called, and the device can automatically and accurately reproduce the entire transformation process without manual intervention, thus improving calibration efficiency and consistency.

[0071] Calibration Board Accuracy Comparison: Using the aforementioned action file function, accuracy comparison tests can be performed between different calibration boards. The specific method is as follows: First, using calibration board A, execute a saved action file to complete calibration and data acquisition. Then, while maintaining the absolute constancy of the spatial position and orientation of the entire calibration device, replace calibration board A with calibration board B. Finally, call the same action file to drive calibration board B to reproduce the exact same pose sequence and acquire images. By comparing and analyzing the results obtained from the two calibration calculations (such as reprojection error), the performance advantages and disadvantages of the two calibration boards can be objectively evaluated, excluding the influence of pose differences.

[0072] Example 2

[0073] Building upon Example 1, this example focuses on the quick-change function of the calibration plate. A highly magnetic circular magnet is embedded in the center of the calibration plate 36. When it is necessary to change from one calibration pattern (such as a checkerboard) to another (such as symmetrical dots or a Charuco calibration plate), simply remove the current calibration plate from the metal servo disk 35 of the third servo 34 by hand, then bring the other calibration plate close to and align it with the metal servo disk; the magnetic force will automatically attract and fix it in place. This design eliminates the need to use tools to tighten screws, making it extremely convenient to switch calibration plates in experimental or teaching scenarios.

[0074] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0075] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A camera calibration device based on optical measurement, characterized in that, include: The outer casing (1) of the device is composed of six independent mounting plates, including an upper side plate, a lower side plate, a left side plate, a right side plate, a front side plate and a rear side plate, and the mounting plates are fixedly connected by screws. The control module (2) is fixed inside the device housing (1) and includes an STM32 control board, a Bluetooth module and a wireless module. The STM32 control board integrates a Bluetooth module and a wireless module and is provided with a USB interface for wired connection, so that the control module can simultaneously support receiving control commands through three methods: USB data cable, Bluetooth connection and wireless handle. The camera calibration assembly (3) includes a first servo (32), a second servo (33), a third servo (34), a connecting component (31), and a calibration plate (36). The body of the first servo (32) is fixed to the lower surface of the upper side plate by screws, and its output shaft passes vertically upward through the servo mounting slot (105) opened on the upper side plate. The connecting component (31) includes a mounting bracket (311) and two L-shaped connectors (312). The two ends of the mounting bracket (311) are fixedly connected to the metal servo disks (35) mounted on the output shafts of the first servo (32) and the second servo (33) by screws. The two L-shaped connectors (312) connect the output shafts of the second servo (33) and the third servo (34), so that the output shafts of the first servo (32), the second servo (33), and the third servo (34) are orthogonal in space, and the orthogonal intersection point of the three axes is located at The end of the output shaft of the third servo (34); the calibration plate (36) is detachably mounted on the metal servo disc (35) of the output shaft of the third servo (34); The STM32 control board is electrically connected to three servos and is used to parse control commands and drive the corresponding servos to rotate, thereby causing the calibration board (36) to generate rotational motion around three orthogonal directions.

2. The camera calibration device according to claim 1, characterized in that, The front panel of the device housing (1) has a fan mounting hole (101) and a plurality of heat dissipation holes (102). The cooling fan (11) is fixed to the fan mounting hole (101) with screws. The rear panel has a first slot (103) and a second slot (104). The power switch and USB interface of the STM32 control board are exposed corresponding to the first slot (103). The second slot (104) is a round hole with threads on the inner wall. The DC charging interface is installed in the second slot (104) by thread engagement.

3. The camera calibration device according to claim 1, characterized in that, The metal rudder disk (35) includes a first side and a second side opposite to each other. The first side is a cylindrical groove with internal gear teeth. The groove meshes with the gear teeth at the end of the servo output shaft and is locked and fixed by a screw passing through the threaded hole in the center of the metal rudder disk (35) and the threaded hole in the center of the servo output shaft. The second side is disc-shaped with four other threaded holes evenly distributed on it with the central threaded hole as the center.

4. The camera calibration device according to claim 3, characterized in that, The calibration plate (36) has a mounting hole at its center that corresponds to the threaded hole on the metal rudder disk (35), and is fastened to the metal rudder disk (35) by screws; or, a circular magnet is embedded at the center of the calibration plate (36), and is detachably connected to the metal rudder disk (35) by magnetic attraction.

5. The camera calibration device according to claim 1 or 4, characterized in that, The calibration plate (36) has a calibration pattern printed on its working surface. The calibration pattern is a black and white checkerboard pattern, a symmetrical dot pattern, or a Charuco pattern.

6. The camera calibration device according to claim 1, characterized in that, The lower side plate of the device housing (1) is provided with multiple positioning holes. The lower ends of multiple mounting pillars (21) are fixed to the positioning holes by screws. The STM32 control board is mounted on the upper end of the mounting pillars (21) by screws, so that the STM32 control board is suspended above the lower side plate.

7. The camera calibration device according to claim 1, characterized in that, The STM32 control board has an initialization program pre-stored in it. When the device is powered on, it automatically controls the first servo motor (32), the second servo motor (33), and the third servo motor (34) to rotate, adjusting the calibration board (36) to the initial position facing the front of the device.

8. The camera calibration device according to claim 1 or 7, characterized in that, During the calibration process, the STM32 control board can record and store in real time the precise control commands that drive the three servos to generate each calibration posture, and generate a series of ordered control commands into an action command file that can be independently stored and called.

9. The camera calibration device according to claim 8, characterized in that, The motion instruction file can be read and executed again by the STM32 control board, so that the camera calibration device can automatically and accurately repeat a specific pose transformation sequence of the calibration board (36).

10. A method for comparing the accuracy of a calibration board using the camera calibration device according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Install the first calibration board on the metal servo disk (35) of the third servo (34), operate the control module to drive the calibration board to complete a set of N preset different pose transformations, and perform image acquisition in each pose. At the same time, save the complete control command sequence that drives these N pose transformations as the first action file. S2: Keep the position and absolute orientation of the calibration device in space unchanged, remove the first calibration plate, replace it with the second calibration plate and install it securely; S3: Call the first action file and control the module to automatically drive the second calibration board to reproduce N poses in sequence; S4: Based on the images acquired by the first calibration board and the second calibration board in the same N poses, camera parameter calibration calculation is performed. By comparing the reprojection error or parameter standard deviation of the two calibration results, the accuracy difference between the two calibration boards is quantitatively evaluated.

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