High-precision Surgical Tool Positioning Method and System Based on TOF Sensor

Abstract

The present invention discloses a high-precision surgical tool positioning method and system based on a TOF sensor, belonging to the technical field of visual positioning. The method includes: during intraoperative surgical navigation, a single TOF sensor is used to simultaneously achieve point cloud measurement of the object shape and high-precision positioning of the surgical tool; the single TOF sensor collects images of a plurality of retroreflective spheres arranged on the surgical tool to obtain the intensity image and depth image of the retroreflective spheres; according to the intensity image, the retroreflective spheres are detected to obtain the two-dimensional centroid coordinates of the retroreflective spheres; according to the depth image, the retroreflective spheres are identified to obtain the one-to-one correspondence of the retroreflective spheres; a preset algorithm is used to accurately calculate the attitude of each retroreflective sphere according to the two-dimensional coordinates and the three-dimensional position relationship of the light spheres. Through the processing solution disclosed in the present invention, the cost and complexity of the system are greatly reduced, making the device small, convenient and easy to use, so it is very suitable for handheld devices for short-distance positioning.

Description

Technical Field

[0001] The present disclosure relates to the technical field of visual positioning, and particularly to a high-precision surgical tool positioning method and system based on a TOF sensor. Background Art

[0002] TOF is the abbreviation of Time of Flight technology, which has been widely used in the fields of three-dimensional vision, unmanned aerial vehicles, three-dimensional face recognition, robots, etc. Since TOF sensors can obtain a large amount of three-dimensional point cloud data, they are generally used to measure and locate the shape of an object. Therefore, during surgery, a TOF sensor can be used only for the three-dimensional positioning of a single organ. However, for very small surgical tools such as probes, it is difficult to be detected by the point cloud sensor. The currently common method is to install a reflective sphere on the surgical tool and use a multi-camera infrared camera to locate the position of the surgical tool by detecting the three-dimensional position of the light sphere. Although the principle of the multi-camera infrared camera is simple, its volume is large. Usually, during the intraoperative surgical navigation process, it is often necessary to simultaneously locate the position of the patient's organ and the surgical tool, so multi-modal sensors need to be used. Some solutions use TOF / structured light to locate the organ and a multi-camera infrared optical camera to locate the surgical tool at the same time. However, when these two sensors are used simultaneously, many problems will arise: 1) Interference problem: The light sources of different sensors are prone to interference, causing the signals of the two sensors to interfere with each other; 2) External parameter calibration problem: When determining the relative position of the two, the relative positions of different sensors need to be calibrated. If any one of the sensors moves, it will be impossible to accurately calculate the error of the surgical instrument relative to the organ; 3) It also increases the complexity of the system.

[0003] To solve the above problems, the present invention proposes a composite positioning system based on a TOF sensor. This system uses only one TOF sensor and can simultaneously perform point cloud measurement of the object's shape and positioning of the surgical tool. The technical solution of the present invention can achieve high-precision calibration of the organ and the surgical tool while reducing the cost and complexity of the system. Summary of the Invention

[0004] In view of this, embodiments of the present disclosure provide a high-precision surgical tool positioning method and system based on a TOF sensor to at least partially solve the problems existing in the prior art.

[0005] In a first aspect, embodiments of the present disclosure provide a high-precision surgical tool positioning method based on a TOF sensor, including:

[0006] During intraoperative surgical navigation, use a single TOF sensor to simultaneously perform point cloud measurement of the object's shape and high-precision positioning of the surgical tool;

[0007] Image acquisition is performed on multiple reflective balls set on a surgical tool through a single TOF sensor to obtain an intensity image and a depth image of the reflective balls;

[0008] According to the intensity image, the reflective balls are detected to obtain the two-dimensional centroid coordinates of the reflective balls, so as to extract the depth information at the corresponding positions from the depth image according to the center points of the reflective balls, and perform inverse projection based on the internal and external parameter information calibrated by the previous camera to extract the three-dimensional coordinates of the reflective balls;

[0009] According to the depth image, the reflective balls are identified to obtain the one-to-one correspondence of the reflective balls;

[0010] Using a preset algorithm, the postures of the reflective balls are accurately calculated according to the two-dimensional coordinates and the three-dimensional position relationship of the light balls.

[0011] According to a specific implementation manner of the embodiment of the present disclosure, the detecting the reflective balls according to the intensity image to obtain the two-dimensional centroid coordinates of the reflective balls includes:

[0012] After denoising and preprocessing the intensity image obtained by the TOF sensor using median filtering and mean filtering, the intensity image is then binarized;

[0013] For the binarized intensity image, the image contour is found through an edge detection algorithm, and then the moments of each contour shape are found;

[0014] The centroid positions of each contour are found through the moments, and then the two-dimensional centroid coordinates of the reflective balls are determined based on the centroid positions, and the centroid is used as the center point of the reflective ball.

[0015] According to a specific implementation manner of the embodiment of the present disclosure, the identifying the reflective balls according to the depth image to obtain the one-to-one correspondence of the reflective balls includes:

[0016] Taking the three-dimensional coordinates of any reflective ball A in the surgical tool as the center, iteratively calculating the distances d a1 、d a2 and d a3 ;

[0017] Aligning the relative distances of d a1 、d a2 and d a3 with the actual relative distances in terms of sorting size, and calculating the loss value after scaling the data to the same value according to the maximum or minimum value;

[0018] Switching the central light ball B, respectively obtaining the distances d calculated iteratively from the three-dimensional coordinates of a reflective ball B as the center to several other reflective ballsb1 , d b2 , d b3 ; With the three-dimensional coordinates of a reflective sphere C as the center, iteratively calculate the distances d from this point to several other reflective spheres c1 , d c2 , d c3 ; With the three-dimensional coordinates of a reflective sphere D as the center, iteratively calculate the distances d from this point to several other reflective spheres d1 , d d2 , d d3 , and the loss value (loss) in each case.

[0019] Select the case with the minimum loss value, and locate the specific reflective spheres through the ordered relative distances and make one-to-one correspondences.

[0020] According to a specific implementation manner of the embodiment of the present disclosure, the method of accurately calculating the postures of each reflective sphere according to the two-dimensional coordinates and the three-dimensional position relationship of the light spheres by using a preset algorithm includes:

[0021] Using a preset algorithm, solve the pose of the target surgical tool in the world coordinate system according to the pixel positions of each reflective sphere in the image and the three-dimensional coordinates of the centers of their corresponding reflective spheres;

[0022] The preset algorithm is the PNP algorithm.

[0023] According to a specific implementation manner of the embodiment of the present disclosure, reflective spheres are installed on the surgical tool for real-time online calibration. Among them, the relative position information of the reflective spheres as landmark points is known, the distances between the reflective spheres are different, and the distance between the reflective spheres is much greater than the radius of the reflective spheres.

[0024] In a second aspect, the embodiment of the present disclosure provides a high-precision surgical tool positioning system based on a TOF sensor, including:

[0025] A surgical tool, on which reflective spheres are installed for real-time online calibration. The relative position information of the reflective spheres as landmark points is known, the distances between the reflective spheres are different, and the distance between the reflective spheres is much greater than the radius of the reflective spheres;

[0026] A TOF sensor, by using only one TOF sensor, perform image acquisition on multiple reflective spheres arranged on the surgical tool to obtain the depth image and intensity image of the reflective spheres;

[0027] A controller, the controller is used to receive the depth image and intensity image obtained by the TOF sensor, so as to execute the method described in the foregoing first aspect or any implementation manner of the first aspect based on the depth image and intensity image.

[0028] In a third aspect, an embodiment of the present disclosure further provides a non-transitory computer-readable storage medium storing computer instructions for causing the computer to execute the high-precision surgical tool positioning method based on a TOF sensor in the foregoing first aspect or any implementation manner of the first aspect.

[0029] In a fourth aspect, an embodiment of the present disclosure further provides a computer program product, which includes a computing program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions that, when executed by a computer, cause the computer to execute the high-precision surgical tool positioning method based on a TOF sensor in the foregoing first aspect or any implementation manner of the first aspect.

[0030] The high-precision surgical tool positioning solution based on a TOF sensor in the embodiments of the present disclosure includes, during intraoperative surgical navigation, simultaneously achieving point cloud measurement of the object shape and high-precision positioning of the surgical tool through a single TOF sensor; collecting images of a plurality of retroreflective spheres provided on the surgical tool through a single TOF sensor to obtain the intensity image and depth image of the retroreflective spheres; detecting the retroreflective spheres according to the intensity image to obtain the two-dimensional centroid coordinates of the retroreflective spheres, so as to extract the depth information at the corresponding position from the depth image according to the center points of the retroreflective spheres, and perform inverse projection according to the internal and external parameter information calibrated by the previous camera to extract the three-dimensional coordinates of the retroreflective spheres; identifying the retroreflective spheres according to the depth image to obtain the one-to-one correspondence of the retroreflective spheres; and using a preset algorithm to accurately calculate the postures of the retroreflective spheres according to the two-dimensional coordinates and the three-dimensional position relationship of the light spheres. Through the processing solution of the present disclosure, the cost and complexity of the system are greatly reduced, making the device small, convenient, and easy to use, and thus very suitable for application in handheld devices for short-range positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 It is a structural diagram of a high-precision surgical tool positioning system based on a TOF sensor provided by an embodiment of the present disclosure;

[0033] Figure 2 It is a schematic flowchart of a high-precision surgical tool positioning based on a TOF sensor provided by an embodiment of the present disclosure;

[0034] Figure 3Another structural diagram of the high-precision surgical tool positioning system based on the TOF sensor provided by the embodiments of the present disclosure. Detailed implementation manners

[0035] The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0036] The following uses specific specific examples to illustrate the implementation manners of the present disclosure. Those skilled in the art can easily understand other advantages and effects of the present disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. The present disclosure can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts belong to the scope of protection of the present disclosure.

[0037] It should be noted that the following describes various aspects of the embodiments within the scope of the appended claims. It should be obvious that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is illustrative only. Based on the present disclosure, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, this device and / or this method can be implemented using other structures and / or functions in addition to one or more of the aspects described herein.

[0038] It should also be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present disclosure schematically. Only the components related to the present disclosure are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0039] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0040] Embodiments of the present disclosure provide a high-precision surgical tool positioning method based on a TOF sensor. The high-precision surgical tool positioning method provided in this embodiment can be executed by a computing device, which can be implemented as software, or as a combination of software and hardware. The computing device can be integrally disposed in a server, a client, etc.

[0041] In an embodiment of the present disclosure, a high-precision surgical tool positioning method based on a TOF sensor can, during intraoperative surgical navigation, simultaneously achieve point cloud measurement of an object shape and high-precision positioning of a surgical tool through a single TOF sensor.

[0042] The currently commonly used method is to install a reflective sphere on the surgical tool and use a multi-view infrared camera to locate the position of the surgical tool by detecting the three-dimensional position of the light sphere. Although the principle of the multi-view infrared camera is simple, its volume is relatively large. Usually, during intraoperative surgical navigation, it is often necessary to simultaneously locate the positions of the patient's organs and the surgical tool. Therefore, multi-modal sensors need to be used. Some solutions use TOF / structured light to locate the organs and use a multi-view infrared optical camera to locate the surgical tool at the same time. However, when these two sensors are used simultaneously, many problems will arise: 1) Interference problem: The light sources of different sensors are prone to interference, causing the signals of the two sensors to interfere with each other; 2) Extrinsic parameter calibration problem: When determining the relative position between the two, the relative positions of different sensors need to be calibrated. If any one of the sensors moves, it will be impossible to accurately calculate the error of the surgical instrument relative to the organ; 3) It increases the complexity of the system at the same time.

[0043] To solve the above problems, the present invention proposes a composite positioning system based on a TOF sensor. This system only uses one TOF sensor and can simultaneously achieve point cloud measurement of the object shape and positioning of the surgical tool. The technical solution of the present invention can achieve high-precision calibration of the organ and the surgical tool while reducing the cost and complexity of the system.

[0044] See Figure 1 、 Figure 2 and Figure 3 , the process of estimating with a single TOF sensor includes:

[0045] S101, perform image acquisition on multiple reflective spheres set on the surgical tool through a single TOF sensor to obtain the intensity image and depth image of the reflective spheres.

[0046] S102, detect the reflective spheres according to the intensity image, obtain the two-dimensional centroid coordinates of each reflective sphere, so as to extract the depth information at the corresponding position from the depth image according to the center point of the reflective sphere, and perform inverse projection according to the internal and external parameter information calibrated by the previous camera to extract the three-dimensional coordinates of the reflective sphere.

[0047] The intensity image is similar to the infrared optical tracking image. Therefore, conventional image processing methods are used to detect the reflective spheres. The specific steps are as follows:

[0048] 1) After preprocessing the image denoising by using median filtering, mean filtering, etc., the image is then binarized.

[0049] 2) The image contours are found through an edge detection algorithm, and then the moments of each contour shape are found.

[0050] 3) Then, the centroid positions of each contour are found through the moments, that is, the two-dimensional centroid coordinates of each light sphere. The centroid can be used as the center point.

[0051] S103. According to the depth image, identify the reflective spheres and obtain the one-to-one correspondence of each reflective sphere.

[0052] See Figure 3 , step S103 may specifically include the following steps:

[0053] 1) Taking the three-dimensional coordinates of one of the reflective spheres A as the center, iteratively calculate the distances d a1 , d a2 , d a3 from this point to several other reflective spheres.

[0054] 2) Align the order of magnitudes of these relative distances with the actual relative distances. After scaling the data to the same value according to the maximum or minimum value, calculate the loss value.

[0055] 3) Switch the central light sphere and repeat steps 1) and 2) to respectively obtain the distances d b1 , d b2 , d b3 iteratively calculated from the three-dimensional coordinates of one of the reflective spheres B as the center to several other reflective spheres; the distances d c1 , d c2 , d c3 iteratively calculated from the three-dimensional coordinates of one of the reflective spheres C as the center to several other reflective spheres; the distances d d1 , d d2 , d d3 iteratively calculated from the three-dimensional coordinates of one of the reflective spheres D as the center to several other reflective spheres, and the loss values in each case.

[0056] 4) Take the case when the loss value is the smallest, and locate the specific reflective spheres through the ordered relative distances and establish a one-to-one correspondence.

[0057] S104. Use a preset algorithm to accurately calculate the poses of each reflective sphere according to the two-dimensional coordinates and the three-dimensional position relationship of the light sphere.

[0058] Use a preset algorithm to solve the pose of the target surgical tool in the world coordinate system according to the pixel positions of each reflective sphere in the image and the three-dimensional coordinates of the centers of their corresponding reflective spheres.

[0059] For example, the PNP algorithm can be used to solve the pose of the target surgical tool in the world coordinate system according to the pixel positions of each reflective sphere in the image and the three-dimensional world coordinates of the centers of their corresponding reflective spheres. The PNP algorithm is an existing algorithm and will not be elaborated here.

[0060] The present invention proposes a composite positioning system based on a TOF sensor. This system uses only one TOF sensor and can simultaneously measure the shape of an object by point cloud and locate the surgical tool. The technical solution of the present invention can achieve high-precision calibration of organs and surgical tools while reducing the cost and complexity of the system.

[0061] According to a specific implementation manner of an embodiment of the present disclosure, the detecting the reflective spheres according to the intensity image and obtaining the two-dimensional centroid coordinates of each reflective sphere includes:

[0062] After preprocessing the denoising of the intensity image obtained by the TOF sensor by using median filtering and mean filtering, then perform binary processing on the intensity image;

[0063] For the intensity image after binary processing, find the image contour through an edge detection algorithm, and then find the moments of the shapes of each contour;

[0064] Find the centroid positions of each contour through the moments, and then determine the two-dimensional centroid coordinates of each reflective sphere based on the centroid positions. The centroid is used as the center point of the reflective sphere.

[0065] According to a specific implementation manner of an embodiment of the present disclosure, the identifying the reflective spheres according to the depth image and obtaining the one-to-one correspondence of each reflective sphere includes:

[0066] Take the three-dimensional coordinates of any one reflective sphere A in the surgical tool as the center, and iteratively calculate the distances d a1 d a2 and d a3 from this center point to the other several reflective spheres on the surgical tool;

[0067] Align the relative distances of d a1 d a2 and d a3 with the actual relative distances in terms of sorting size. After scaling the data to the same value according to the maximum or minimum value, calculate the loss value;

[0068] Switch the central light sphere B, and respectively obtain the distances d from a three-dimensional coordinate of one reflective sphere B as the center to several other reflective spheres through iterative calculation b1 、d b2 、d b3 ; Take the three-dimensional coordinate of one reflective sphere C as the center, and iteratively calculate the distances d from this point to several other reflective spheres c1 、d c2 、d c3 ; Take the three-dimensional coordinate of one reflective sphere D as the center, and iteratively calculate the distances d from this point to several other reflective spheres d1 、d d2 、d d3 , and the loss value (loss) in each case.

[0069] Select the case when the loss value is the smallest, and locate the specific reflective spheres through the ordered relative distances and correspond one by one.

[0070] According to a specific implementation manner of the embodiment of the present disclosure, the preset algorithm is the PNP algorithm.

[0071] According to a specific implementation manner of the embodiment of the present disclosure, reflective spheres are installed on the surgical tool for real-time online calibration. Among them, the relative position information of the reflective spheres as the marker points is known, the distances between the reflective spheres are different, and the distance between the reflective spheres is much larger than the radius of the reflective spheres.

[0072] Corresponding to the above method embodiment, see Figure 1 , the present disclosure also provides a high-precision surgical tool positioning system based on a TOF sensor, including:

[0073] A surgical tool, on which reflective spheres are installed for real-time online calibration. The relative position information of the reflective spheres as the marker points is known, the distances between the reflective spheres are different, and the distance is much larger than the radius of the reflective spheres;

[0074] A TOF sensor, by using only one TOF sensor, image acquisition is performed on a plurality of reflective spheres arranged on the surgical tool to obtain the depth image and intensity image of the reflective spheres;

[0075] A controller, which is used to receive the depth image and intensity image obtained by the TOF sensor, so as to execute the method described in the foregoing embodiment based on the depth image and intensity image.

[0076] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram may represent a module, a segment of a program, or a part of code that contains one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than that marked in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and combinations of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system that performs the specified functions or operations, or can be implemented by a combination of dedicated hardware and computer instructions.

[0077] The units described in the embodiments of the present disclosure can be implemented in software or in hardware. Among them, the name of the unit does not constitute a limitation on the unit itself in some cases. For example, the first acquisition unit can also be described as "the unit for acquiring at least two Internet protocol addresses".

[0078] It should be understood that the various parts of the present disclosure can be implemented by hardware, software, firmware, or a combination thereof.

[0079] As described above, the above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present disclosure should be covered by the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. A high-precision surgical tool positioning system based on a TOF sensor, characterized in that, Including: A surgical tool with a reflective sphere installed thereon for real-time online calibration. The relative position information of the reflective spheres serving as landmark points is known. The distances between the reflective spheres are different and much larger than the radius of the reflective spheres. A TOF sensor. By using only one TOF sensor, image acquisition is performed on multiple reflective spheres set on the surgical tool to obtain the depth image and intensity image of the reflective spheres. A controller. The controller is used to receive the depth image and intensity image obtained by the TOF sensor, so as to execute the following method based on the depth image and intensity image: During intraoperative surgical navigation, the shape of the object is measured by point cloud and the high-precision positioning of the surgical tool is achieved simultaneously through a single TOF sensor. Image acquisition is performed on multiple reflective spheres set on the surgical tool through a single TOF sensor to obtain the intensity image and depth image of the reflective spheres. Based on the intensity image, the reflective spheres are detected to obtain the two-dimensional centroid coordinates of the reflective spheres, so as to extract the depth information at the corresponding positions from the depth image according to the center points of the reflective spheres, and perform inverse projection according to the internal and external parameter information calibrated by the previous camera to extract the three-dimensional coordinates of the reflective spheres. Based on the depth image, the reflective spheres are identified to obtain the one-to-one correspondence of the reflective spheres. A preset algorithm is adopted to accurately calculate the postures of the reflective spheres according to the two-dimensional coordinates and the three-dimensional position relationship of the light spheres.

2. The system according to claim 1, wherein The detecting the reflective spheres based on the intensity image to obtain the two-dimensional centroid coordinates of the reflective spheres includes: After denoising and preprocessing the intensity image obtained by the TOF sensor by using median filtering and mean filtering, the intensity image is then binarized. For the binarized intensity image, the image contour is found through an edge detection algorithm, and then the moments of each contour shape are found. The centroid positions of each contour are found through the moments, and then the two-dimensional centroid coordinates of the reflective spheres are determined based on the centroid positions. The centroid serves as the center point of the reflective sphere.

3. The system according to claim 2, wherein The identifying the reflective spheres based on the depth image to obtain the one-to-one correspondence of the reflective spheres includes: Taking the three-dimensional coordinates of any one of the reflective spheres A in the surgical tool as the center, iteratively calculate the distances d from this center point to several other reflective spheres on the surgical tool a1 , d a2 and d a3 ; Align the relative distances of d a1 , d a2 and d a3 with the sorted magnitudes of the actual relative distances. After scaling the data to the same value based on the maximum or minimum value, calculate the loss value; Switch the central light sphere B, and respectively obtain the distances d obtained by iteratively calculating the distances from a three-dimensional coordinate of one reflective sphere B to several other reflective spheres b1 , d b2 , d b3 ; Take the three-dimensional coordinate of one reflective sphere C as the center, and iteratively calculate the distances d from this point to several other reflective spheres c1 , d c2 , d c3 ; Take the three-dimensional coordinate of one reflective sphere D as the center, and iteratively calculate the distances d from this point to several other reflective spheres d1 , d d2 , d d3 , and the loss values in each case; Taking the situation when the loss value is the smallest, the specific reflective spheres are located through the ordered relative distances and are in one-to-one correspondence.

4. The system according to claim 3, characterized in that, The accurately calculating the postures of the reflective spheres according to the two-dimensional coordinates and the three-dimensional position relationship of the light spheres by adopting a preset algorithm includes: A preset algorithm is adopted to solve the pose of the target surgical tool in the world coordinate system according to the pixel positions of the reflective spheres in the image and the three-dimensional coordinates of the corresponding reflective sphere centers. The preset algorithm is the PNP algorithm.

5. The system according to claim 1, wherein: A reflective sphere is installed on the surgical tool for real-time online calibration. Among them, the relative position information of the reflective spheres serving as landmark points is known. The distances between the reflective spheres are different, and the distance between the reflective spheres is much larger than the radius of the reflective spheres.

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