System and method for magnetometer spatial positioning

Abstract

A system and method for spatial positioning of a magnetometer, the system comprising: a magnetometer, a magnetometer bracket, a first positioning marker, a photogrammetry system, and a controller, wherein the magnetometer bracket is fixedly arranged relative to the head or other body part of a subject and includes at least one mounting portion with an orientation, allowing the magnetometer to be respectively arranged on the mounting portion at a first depth along a specific direction; the first positioning marker is a non-rotationally symmetric pattern; the photogrammetry system includes a photographic device configured to capture first image data of the first positioning marker at at least two of a plurality of capturing locations through one or more of the photographic devices; the controller is configured to receive the first image data captured by the photographic device and calculate the spatial position of the first positioning marker based on pre-acquired system parameters and the first image data, thereby calculating the spatial position and spatial orientation of the magnetometer.

Description

Technical Field

[0001] The present invention relates to a system and method for magnetometer spatial positioning. Background Art

[0002] In the field of electroencephalography (EGG) testing, it is usually necessary to install EEG detectors, such as patch electrodes, around the patient's head. The detectors are usually located using manual markings or a camera array.

[0003] The magnetic detector in the existing MEG technology uses a superconducting quantum interference device (SQUID) as its core device, which has a high sensitivity (about 1fT / Hz). 1 / 2 ), but it requires liquid helium to maintain superconducting working conditions, resulting in very high equipment and operating costs. A new type of magnetic detector, the Optical-Pumping Magnetometer (OPM), uses a light beam to polarize atomic gases and exploits the magnetic effect of atomic spin to measure weak magnetic fields. Its measurement accuracy reaches or even exceeds that of the SQUID magnetometer. It also operates at room temperature, does not require liquid helium cooling, is compact and lightweight, and can be mass-produced at low cost using semiconductor processes.

[0004] Furthermore, in actual OPM applications, magnetometers are typically inserted into a helmet worn by the patient to fix their position. To further measure three-dimensional magnetic field vector information, it is necessary to obtain the insertion depth and orientation information of the magnetometer. However, the positioning method of the EEG system can only be used to detect detectors such as patch electrodes, which are very thin and can be considered as a single point in space. Magnetometers are typically large in size, and using a camera array to capture images will prevent the complete image from being captured due to mutual occlusion between the magnetometers. This makes it difficult to locate the magnetometer's position and obtain its spatial orientation information. Summary of the Invention

[0005] An embodiment of the present invention provides a system for spatial positioning of a magnetometer, the system comprising: a magnetometer configured to obtain magnetic field data related to brain magnetism or other parts of the biomagnetic field; a magnetometer bracket fixedly arranged relative to the subject's head or other parts of the body and comprising at least one mounting portion with an orientation, allowing the magnetometer to be respectively arranged on the mounting portion at a first depth along a specific direction; a first positioning marker, the first positioning marker being a non-rotationally symmetric pattern, the first positioning marker being respectively arranged in association with the magnetometer; a photogrammetry system, the photogrammetry system comprising a photographic device configured to capture first image data of the first positioning marker at at least two of a plurality of capturing locations through one or more of the photographic devices; and a controller configured to receive the first image data captured by the photographic device, and calculate the spatial position and spatial orientation of the first positioning marker based on pre-acquired system parameters and the first image data, thereby calculating the spatial position and spatial orientation of the magnetometer.

[0006] An embodiment of the present invention provides a method for spatial positioning of a magnetometer in a system as described above, the method comprising the following steps: receiving a subject in a photogrammetry system, the subject wearing a magnetometer bracket on which at least one magnetometer is provided; capturing first image data of first positioning marks respectively associated with the magnetometers at at least two of a plurality of capturing locations using one or more photographic devices, the first positioning marks being non-rotationally symmetric patterns; receiving the first image data captured by the photographic devices via a controller, and identifying the first positioning mark via the controller; and calculating the spatial position and spatial orientation of the first positioning mark based on system parameters and the first image data, thereby calculating the spatial position and spatial orientation of the magnetometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention. The drawings are only used to illustrate some embodiments of the present invention, but not to limit all embodiments of the present invention thereto.

[0008] Figure 1 FIG2 shows a schematic diagram of installing a magnetometer bracket according to an embodiment of the present invention;

[0009] Figure 2 A diagram showing a set of coded markings according to an embodiment of the present invention;

[0010] Figure 3 shows a coding mark diagram according to another embodiment of the present invention;

[0011] Figure 4 shows a coding mark diagram according to another embodiment of the present invention;

[0012] Figure 5A and Figure 5B A schematic diagram of a coding method for coding a coding mark according to an embodiment of the present invention is shown;

[0013] Figure 6 FIG2 shows a schematic diagram of a system for magnetometer spatial positioning according to an embodiment of the present invention;

[0014] Figure 7 Shown Figure 6 A schematic diagram of the photographic apparatus of the system shown;

[0015] Figure 8 FIG2 shows a schematic diagram of a system for magnetometer spatial positioning according to another embodiment of the present invention;

[0016] Figure 9 The schematic diagram of the three-dimensional coordinate measurement principle based on the dual-photograph device is shown;

[0017] Figure 10 Schematic diagram showing images of coded markers at different shooting locations;

[0018] Figure 11 A flow chart of a method for magnetometer spatial positioning according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the technical solution of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of specific embodiments of the present invention. The same figure marks in the drawings represent the same components. It should be noted that the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by persons of ordinary skill in the field to which the invention belongs. The words "first", "second" and similar terms used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "a" or "an" do not necessarily indicate a quantity limitation. Words such as "include" or "comprising" mean that the elements or objects preceding the word include the elements or objects listed after the word and equivalents, without excluding other elements or objects. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0021] In the field of electroencephalography (EGG) or magnetoencephalography (MEG) detection, it is usually necessary to install detectors around the subject's head to detect EEG or brain magnetism. However, since the detectors are usually installed on the surface of the subject's scalp, it is difficult to detect signals inside the brain, and therefore the signals are difficult to associate with the anatomical space, and it is also difficult to locate the brain magnetism source. To solve this problem, researchers have proposed combining detector spatial positioning with magnetic resonance imaging (MRI) to simultaneously obtain the subject's brain anatomical structure and the detector spatial orientation. This solution requires co-registration of the detector spatial data with MRI.

[0022] In EEG, there are four common methods for spatial positioning of detectors:

[0023] 1. Direct manual measurement: This involves using a caliper to measure the position between each detector and a fixed marker and calculating the Cartesian coordinates of each detector. This method requires no special materials or equipment and is low-cost, but it requires significant time and labor. Furthermore, due to significant human error, measurement accuracy is low.

[0024] Electromagnetic digitizers, such as the Fastrack system (Polhemus, Colchester, United States), calculate the position and orientation of a receiver as it moves within an electromagnetic field, achieving a detection accuracy of up to 3.6 mm. However, electromagnetic digitizers are highly sensitive to their environment. Metal objects in the environment can alter and distort the electromagnetic field, affecting its integrity and significantly impacting detection accuracy. Furthermore, electromagnetic digitizer systems are expensive and costly.

[0025] Ultrasonic digitizers measure distance by measuring the time it takes for an ultrasonic pulse to travel from a generator to a receiver, thereby calculating three-dimensional spatial position. However, ultrasonic digitizers are also highly sensitive to environmental factors, affected by temperature and humidity. Furthermore, similar to electromagnetic digitizers, ultrasonic digitizers require measurement at each measurement point, which is time-consuming.

[0026] 4. Photogrammetry systems, such as the Geodesic photogrammetry system (Electrical Geodesics Inc, United States), use a photogrammetry network to measure the spatial position of objects. Each of the 11 nodes in the photogrammetry sensor network is equipped with a camera that can simultaneously capture a single photo. The system's software then uses triangulation to convert the position of each detector in the two-dimensional photo into three-dimensional spatial coordinates. This method is fast and the subject can be moved. However, this method can only locate the three-dimensional spatial position points of circular / annular EEG electrodes and cannot mark the three-dimensional spatial orientation of each detector. In addition, the label of each detection channel can only be determined by the relative position relationship between the detection channels. If the electrode position is changed or replaced, the detector in the photo needs to be manually marked, which can easily lead to operational errors. This system is located in the preparation room and uses a visible light illumination system. It can only be used for electrode position calibration during the test preparation phase and cannot perform continuous position tracking during the experiment.

[0027] The magnetic detector in the existing MEG technology uses a superconducting quantum interference device (SQUID) as its core device, which has a high sensitivity (about 1fT / Hz). 1 / 2 ), but it requires liquid helium to maintain superconducting working conditions, resulting in very expensive equipment and operating costs. A new type of magnetic detector, the Optical-Pumping Magnetometer (OPM), uses a light beam to polarize atomic gas and utilizes the magnetic effect of atomic spin to measure weak magnetic fields. The optical-pumping magnetometer, based on the spin-exchange relaxation effect (SERF), has a measurement accuracy that reaches or even exceeds that of the SQUID magnetometer. It can also operate at room temperature, does not require liquid helium cooling, is small and light, and can be mass-produced at low cost using semiconductor processes.

[0028] Furthermore, because SERF-based magnetometers are single-axis or multi-axis vector detectors, in the field of MEG detection, in order to further measure three-dimensional magnetic field vector information and accurately trace the source, it is necessary to obtain the spatial position and three-dimensional spatial orientation information of the detector (magnetometer). However, existing technologies, especially EEG technology, mainly focus on the spatial positioning of the detector, but lack the positioning of the detector's orientation. Based on this, the present invention proposes a system and method for magnetometer spatial positioning. Specifically, the present invention proposes a photogrammetry system and method based on coded markers.

[0029] It should be noted that "spatial positioning" as used in this invention refers to both spatial position and spatial orientation. Furthermore, "spatial position" as used in this invention refers to one or both of an object's three-dimensional coordinates in space and its relative position to another object. "Spatial orientation" as used in this invention refers to the vector direction of an object in space, with its longitudinal axis as the axis, and the angle of rotation of the object along that longitudinal axis.

[0030] It should be noted that the "non-rotationally symmetric pattern" described in the present invention refers to a pattern that cannot overlap with itself after being rotated at any angle (less than 360 degrees) around any center point in a plane.

[0031] An embodiment of the present invention provides a system for spatial positioning of a magnetometer, comprising: a magnetometer configured to obtain magnetic field data related to brain magnetism or other parts of the biomagnetic field; a magnetometer bracket fixedly arranged relative to the subject's head or other parts of the body, and comprising at least one mounting portion with an orientation, allowing the magnetometer to be respectively arranged on the mounting portion at a first depth along a specific direction; a first positioning marker, the first positioning marker being a non-rotationally symmetric pattern, the first positioning marker being respectively arranged in association with the magnetometer; a photogrammetry system, the photogrammetry system comprising a photographic device configured to capture first image data of the first positioning marker at at least two of a plurality of capturing locations through one or more of the photographic devices; and a controller configured to receive the first image data captured by the photographic device, and calculate the spatial position and spatial orientation of the first positioning marker based on pre-acquired system parameters and the first image data, and thereby calculate the spatial position and spatial orientation of the magnetometer.

[0032] Exemplarily, the first positioning mark is fixedly disposed on an outer surface (e.g., end and / or side) of the magnetometer, on an extension structure rigidly connected to the magnetometer, or on an auxiliary structure of a magnetometer support fixed relative to the magnetometer. Preferably, the first positioning mark is disposed on the outermost end surface of the magnetometer, as this location is most easily captured by the imaging system. Figure 1 FIG. 1 shows a schematic diagram of installing a magnetometer bracket according to an embodiment of the present invention. Figure 2 A diagram showing a set of coded markings according to an embodiment of the present invention, Figure 3 shows a coding mark diagram according to another embodiment of the present invention, Figure 4 shows a coding mark diagram according to another embodiment of the present invention, Figure 5A and Figure 5B FIG. 1 shows a schematic diagram of a coding method for coding a coding mark according to an embodiment of the present invention. Figure 6 FIG. 1 shows a schematic diagram of a system for magnetometer spatial positioning according to an embodiment of the present invention. Figure 7 A schematic diagram showing a photographing device of the system shown in FIG5 is shown.

[0033] The system includes a magnetometer 1, a magnetometer bracket 2, a first positioning marker 3 and a photogrammetry system 4. The magnetometer 1 is used to obtain information related to brain magnetism. In addition, the magnetometer 1 can also be used to obtain information related to the biomagnetic field of other parts, depending on the location of the magnetometer 1. Figure 1 As shown, for example, the magnetometer bracket 2 is in the form of a helmet, which is fixed relative to the subject's head and includes at least one mounting portion (not shown) having an orientation, allowing the magnetometer 1 to be respectively arranged in the mounting portion at a first depth along a specific direction.

[0034] Illustratively, the mounting portion is a mounting hole, and the magnetometer 1 is fixedly mounted on the magnetometer bracket 2 , so once the installation is completed, the relative position between the magnetometer 1 and the mounting hole can be fixed and determined.

[0035] It should be noted that the detector 11 of the magnetometer 1 is a vector detector and the magnetic field information detected is vector information, which is different from the traditional EEG detection which only detects electrode scalar signals. Therefore, it is necessary to measure the magnetic field vector information detected by the detector 11.

[0036] Optionally, the magnetometer bracket 2 can be rigid or flexible. In this embodiment, the magnetometer bracket 2 is rigid, meaning that once worn on the subject's head, the relative positions of the various magnetometers 1 on the magnetometer bracket 2 do not readily change. The magnetometer bracket 2 can be made of a non-magnetic material, such as a photosensitive toughened resin or nano-ceramic material.

[0037] Preferably, the first positioning mark 3 is a first coded mark, fixedly disposed with respect to each magnetometer in a unique relationship. The first positioning mark is a planar or three-dimensional structure, and exhibits invariance to rotation and scaling, thereby maintaining geometric stability and uniqueness at different distances and angles. That is, each first positioning mark 3 carries coded information, and this coded information corresponds one-to-one with the magnetometer 1 to which it is fixed.

[0038] Exemplarily, the system may further include one or more second positioning markers 6, which are fixedly disposed on the subject's head or other body parts, or on an extension structure rigidly connected to the subject's head or other body parts.

[0039] In this embodiment, the first positioning mark 3 is fixedly provided at the end of the detector 11 of the magnetometer 1. Specifically, the first positioning mark 3 is fixedly provided on the surface of the end of the detector 11 of the magnetometer 1, and the second positioning mark 6 is fixedly provided at the center of the eyebrows and in front of the left and right ears of the subject's head. Thus, the position of the detector 11 of the magnetometer 1 and the position of the subject's head can be marked respectively, so as to facilitate the subsequent registration of the anatomical points of the body part with the magnetometer bracket.

[0040] Alternatively, the first positioning mark 3 may be fixedly disposed in other locations, such as on the side of the detector 11 of the magnetometer 1, on an extension structure rigidly connected to the magnetometer 1, or on an auxiliary structure of the magnetometer bracket 2 fixed relative to the magnetometer 1, depending on the requirements of the actual application, and the present invention is not limited thereto. As long as the coding marks do not obstruct each other, it is best to arrange larger and more numerous coding marks to achieve better positioning accuracy.

[0041] Alternatively, the second positioning mark 6 may not be provided, and the above registration may be performed by scanning a three-dimensional image of the body part through MRI and implementing the registration through matching software.

[0042] The first positioning mark 3 can be a planar or three-dimensional structure, exhibiting stability under rotation and scaling. Furthermore, the first positioning mark 3 can be a non-rotationally symmetric and / or non-axisymmetric pattern to maintain geometric structural stability and uniqueness at varying distances and angles. The first positioning mark 3 is a man-made mark with digitally encoded information, possessing unique identity information and enabling automatic identification through methods such as image processing. In this embodiment, the first positioning mark 3 is a planar structure.

[0043] The first positioning mark 3 can be at least one of a ring-shaped coding mark (also known as a "Schneider coding mark"), a dot-shaped coding mark, a square coding mark or a digital coding mark. Figures 2 to 4 The first positioning mark 3 of the present invention is shown as an example. For example, the first positioning mark 3 can be as follows Figure 2 The circular coding mark shown in the mark AD can also be as shown in FIG. Figure 3 The dot coding mark shown in the mark EG, or Figure 4 The block code mark shown by mark J in FIG. Figure 4 In addition, the first positioning mark 3 can also be a digital code mark as shown in the mark K. Figure 4Other coding marks without obvious geometric features are shown in the mark HI. It should be noted that the above is only exemplary, and those skilled in the art can propose other shapes of coding marks based on the inspiration of the above examples. In this embodiment, the first positioning mark 3 is a ring-shaped coding mark.

[0044] The following will be combined Figure 5A and Figure 5B Describe the coding principle of ring coded marking. Figure 2 As shown by the mark AD in the middle, the circular coding mark mainly consists of a central positioning mark and the coding bits surrounding it. These coding bits can be strip-shaped or dot-shaped. The coding bits are distributed on concentric circles with the center of the positioning mark as the center. The coding capacity can be increased by increasing the number of concentric circles or increasing the number of coding bits on the same circumference. The circular coding mark needs to reserve a part of the area as the code reading reference, for example Figure 2 The lower left area of ​​the circular coding mark shown by the mark AD in the middle. The circular coding mark adopts the binary coding principle, that is, it uses 0 and 1 to encode. Each coding mark has a unique number corresponding to it.

[0045] like Figure 5A As shown in the figure, the center positioning mark is surrounded by a ring with a unique code. The code ring is divided into n equal parts at equal angles (called n-bit code). Each equal part is called a code bit. Each code bit can be regarded as a binary bit. Black represents 0 and white represents 1. Each bit can be 0 or 1. Figure 5B As shown in . Here, represents an 8-bit code, so each code mark consists of 8 binary digits. According to the rotational invariance requirement of the code, each code bit can be used as the first bit of an 8-bit binary number. For each specific mark, the 8-bit code has a total of 8 binary digits corresponding to it. Since each code mark can only have a unique numerical identity, the minimum value of the corresponding decimal number is used as the code number of the code mark.

[0046] In order to determine the starting position of reading the coded information, the fast Hough transform can be used to obtain the position of the center O and the radius R of the circle. With O as the center and 2.5R as the radius, the grayscale value is read in a clockwise or counterclockwise direction and converted into binary code.

[0047] Now combine the code bits in a clockwise direction, then Figure 5B The 8 binary numbers corresponding to the codes shown are: 00100101, 01001010, 10010100, 00101001, 01010010, 10100100, 01001001, 10010010. Among these 8 binary numbers, the decimal number corresponding to 00100101 is the smallest (001001012=3710 ), therefore, the code number corresponding to this coding mark is 37. The present invention is not limited to this. The coding rule can take the maximum value, or the coding bits can be combined in a counterclockwise direction. The value of n can also be selected based on the actual coding capacity. Suitable coding marks can be selected to accommodate a coding capacity of more than 256 channels while having reasonable precision positioning reference marks. Through this set of coding mark system, the photogrammetry system 4 can not only identify the coding marks and calibrate the position of the magnetometer 1, but also calibrate the spatial three-dimensional orientation of the magnetometer 1 through perspective projection transformation.

[0048] In addition, the first positioning mark 3 may include a reflective material or a stimulated luminescent material to provide sufficient contrast under the illumination light source or excitation light source of the photogrammetry system 4. Examples of the reflective material include glass microbead reflective material and microprism reflective material. Examples of the stimulated luminescent material include fluorescent material, upconversion luminescent material, phosphorescent material, rare earth luminescent material, etc.

[0049] Optionally, the first positioning mark 3 may include an active luminescent material, such as a light emitting diode (LED).

[0050] The material of the first positioning mark 3 can be selected based on the illumination or excitation light source of the photogrammetry system 4. For example, when the photogrammetry system 4 uses an infrared illumination source, the material of the first positioning mark 3 can include a material that reflects infrared light. When the photogrammetry system 4 uses an excitation light source, the material of the first positioning mark 3 can include a fluorescent material. When the photogrammetry system 4 does not use an illumination device, the material of the first positioning mark 3 can include an active luminescent material. Coded marks made using a special illumination source (such as infrared) and a corresponding specifically reflective material can achieve continuous recording before and during the recording of the mark, even under special conditions such as requiring a dark environment.

[0051] For example, the second positioning mark 6 may have the same graphic characteristics as the first positioning mark 3 and / or be made of the same material as the first positioning mark 3 .

[0052] like Figure 6 As shown, the photogrammetry system 4 can receive the magnetometer bracket 2 therein so as to photograph the magnetometer bracket 2, the magnetometer 1 mounted thereon and the first positioning mark 3. The photogrammetry system 4 includes a photographic device 41, which is configured to photograph the first image data of the first positioning mark 3 at at least two of the multiple photographic locations 43 through one or more of the photographic devices 41 and send the obtained first image data to the controller.

[0053] Exemplarily, the photographing device 41 may also be configured to photograph the second image data of the second positioning mark 6 at at least two photographing locations among the plurality of photographing locations 43 through one or more photographing devices 41 and send the obtained second image data to the controller.

[0054] The photogrammetry system 4 includes a structural support system 42 for mounting a photographic device 41, such as Figure 6 The structural support system 42 can be a frame structure formed into a semi-polygonal or hemispherical shape. Multiple imaging locations 43 are provided within the hemispherical or other shaped surface. Each imaging location 43 is secured with at least one imaging device 41. Alternatively, at least one imaging device can be manually or automatically moved between different imaging locations. Alternatively, at least one imaging device can be secured between adjacent imaging locations. This allows for rapid, multi-angle imaging of features including coded markers and head / body shapes. In this embodiment, the structural support system 42 is provided with multiple imaging locations 43 within a hemispherical surface. Each imaging location 43 is secured with a imaging device 41, and a imaging device 41′ can also be secured between adjacent imaging locations 43.

[0055] For example, Figure 6 As shown, the structural support system 42 can be frame-shaped, including multiple nodes and connectors connecting two adjacent nodes, and the shooting location 43 is set at each node. The connector can be fixed or movable with a photography device, or not.

[0056] The photographing device 41 can be a camera or a video camera. Figure 7 As shown, the photographing device 41 may include a lighting device 411 and a lens 412 .

[0057] Optionally, the structural support system 42 may further include a position adjustment device 44, which is configured to adjust the position of the photogrammetric system 4 or the structural support system 42. For example, by adjusting the position of the structural support device 42 relative to the magnetometer bracket 2, the lens 412 of the photographic device 41 can be moved closer to or further away from the photographed object as needed. Alternatively, the position adjustment device 44 can move the entire photogrammetric system 4 away from or closer to the subject, so that after the subject is ready, the photogrammetric system 4 can be placed in a position where the subject can be photographed, and away from the subject after the photographing is completed, so that the subject can leave. The position adjustment device 44 may include a hinge so that the entire photogrammetric system 4 can pivot, or may include a track so as to drive the entire photogrammetric system 4 to rise and fall and / or move in other directions.

[0058] Optionally, the photogrammetry system 4 may include a reference device (not shown) for calibrating the initial position of the structural support system 42 .

[0059] Optionally, the photogrammetry system 4 includes a calibration device (not shown) for calibrating the initial position and shooting angle of the photographic device to provide system parameters, thereby further improving the calibration accuracy of the system.

[0060] The photographic device 41 and its lighting device 411 can provide sufficient contrast for the first positioning mark 3 to distinguish it from background objects. By photographing the contours of the subject's head, face or other parts, the magnetometer bracket 2 and the magnetometer 1 at different angles, a three-dimensional model based on the same coordinate system space is established, including the three. Additional coding marks (second positioning marks 6) can be added to parts other than the magnetometer 1, such as specific anatomical sites on the subject's head, or fixed structures connected to these sites, to improve the positioning accuracy of the model reference points. Based on this model, the coding features and perspective features of the coding marks connected to the magnetometer 1 are further identified to obtain the spatial position and orientation information of each magnetometer 1 relative to the aforementioned three-dimensional model. Thereafter, the three-dimensional model and information can be further used to align and calculate the contours obtained by MRI, etc., so as to obtain the position and orientation information of the magnetometer 1 in the coordinate system based on the anatomical image and the relative position and orientation relationship with the internal structure of the subject's body.

[0061] In addition, the system according to an embodiment of the present invention may further include a controller (not shown), which stores pre-acquired system parameters. The system parameters may preferably include the focal length of the photographic device 41, the shooting angle of the photographic device 41, the spatial position coordinates of the photographic device 41, the geometric size parameters of the magnetometer and / or the encoding information of the first positioning mark 3, etc. However, this is not restrictive and these parameters may also be input by the operator during each measurement. The controller is configured to receive the first image data captured by the photographic device 41 and calculate the spatial position and spatial orientation of the first positioning mark 3 based on the system parameters and the first image data, thereby calculating the spatial position and spatial orientation of the magnetometer 1.

[0062] Exemplarily, the controller receives the second image data 6 and calculates the spatial positioning of the subject's head or other body parts based on the system parameters and the second image data 6 to achieve alignment of the anatomical points of the subject's head or other body parts with the magnetometer bracket 2.

[0063] Exemplarily, the controller can be a microcontroller unit (MCU), a field programmable gate array (FPGA) or a digital signal processor, a CPU, a desktop computer, a workstation, or other controller commonly used in the art with data receiving and processing capabilities.

[0064] Figure 8A schematic diagram of a system for magnetometer spatial positioning according to another embodiment of the present invention is shown. Figure 8 The system of this embodiment will be described.

[0065] The following is only about this embodiment and Figure 6 The differences between the illustrated embodiments are described, while the similarities or identicalities are not repeated here.

[0066] In this embodiment, the structural support system is fixedly mounted within a shielded room 5. Shielded room 5 isolates the magnetometer 1 from external magnetic fields, electromagnetic fields, or other interference sources, thereby ensuring that the magnetometer 1 is not disturbed by changes in the external magnetic field during measurement. The subject, wearing a rigid or flexible magnetometer bracket 2, sits within the shielded room 5.

[0067] The structural support system, for example, includes a support frame 42 fixedly mounted on the top of the shielded room 5 and a support frame 42′ fixedly mounted on the side of the shielded room 5, and the photographic device 41 can be configured to be manually or automatically moved between different photographic locations, thereby achieving multi-angle adjustable photography. Therefore, during the recording process, some or all of the photographic devices of the system can continuously track the position of the first positioning mark 3 of the magnetometer 1 and / or the second positioning mark 6 on the subject's body part, thereby continuously recording possible changes in the relative position / orientation between the magnetometers, the relative position / orientation between the magnetometer and the subject, and the relative position / orientation between the magnetometer and the shielded room.

[0068] This information can be used for a range of purposes, including calculating the pointing field of the magnetometer bracket 2, calibrating the position of the magnetometer 11 and the subject's head, and reducing background magnetic field signals. Using a special illumination source (such as infrared) and a coding marker made of a corresponding specific reflective material, continuous recording can be achieved before and during recording of the marker, even under special conditions such as a dark environment.

[0069] The purpose of decoding and recognizing coded marks is to determine the digital information of the center positioning mark, that is, the number information of the point, so that the image points with the same name can be found in different images in subsequent calculations, and other non-coded marks can be automatically matched based on the image coordinate information and digital information of the center positioning mark.

[0070] Figure 9 The figure shows a schematic diagram of a three-dimensional coordinate measurement principle based on a dual-photography device and dual-photographs as an example of the present invention. Figure 9 The measurement shown is based on first image data of two first positioning markers captured by two imaging devices at two of a plurality of imaging locations. The three-dimensional coordinates of the image points in the photographs, i.e., the first and / or second positioning markers, are calculated using collinearity or coplanarity equations. This measurement principle is widely used in the field of computer vision.

[0071] Optionally, based on this principle, the first image data of the first positioning mark may be captured by multiple photographing devices at more than two photographing positions for calculation.

[0072] In this embodiment, the three-dimensional coordinates of the image points in the photo, i.e., the first and / or second positioning marks, are calculated using the collinear equation. Figure 9 As shown, assume that the image space coordinate system O-xyz of the left camera coincides with the object coordinate system, the image plane coordinate system is O1-X1Y1, the effective focal length is f1, and the image space coordinate system O of the right camera is r -x r y r z r , the image plane coordinate system is O r -X r Y r , the effective focal length is f r Assume that the coordinates of the object point P in O-xyz are (X, Y, Z), the coordinates of the corresponding image point p in the left photo are (x, y, -f1), and the coordinates of the corresponding image point pr in O-xyz are (x, y, -f1). r -X r Y r The coordinates in (x r ,y r ,-f r ). Through the collinear or coplanar equation (a common equation used in digital close-range industrial photogrammetry), we can obtain:

[0073]

[0074]

[0075]

[0076]

[0077] in,

[0078] They are O-xyz coordinate system and O r -X r Y r The rotation and translation matrices between coordinate systems.

[0079] When the parameters of the photographic device (including focal length), the image coordinates of the spatial point to be measured in the left and right photos, the rotation matrix R and the translation matrix T are known, the three-dimensional coordinates of the spatial point to be measured can be obtained by combining the above four equations.

[0080] Figure 10 Schematic diagram showing images of coded marks at different shooting locations. Figure 10An example method for computing the spatial orientation of a coding marker is described. Figure 10 As shown, the first positioning marks 31, 32, 33 are images captured by photographing devices 41, 41', 41" from different angles.

[0081] For example, the affine parameters of the first and / or second positioning marks can be calculated by the affine transformation method. In this embodiment, the first and second positioning marks are both coded marks. After the coded mark is imaged by the camera lens, a projection image is generated on the imaging plane. If the imaging plane is not parallel to the plane where the coded mark is located, the projection image will be deformed, such as Figure 10 As shown in the first positioning mark 31 and the first positioning mark 33, standardization is to reconstruct the elliptical image after projection deformation into a standard circular image, for example Figure 10 The first positioning mark 32 in the image is normalized. The annular code mark area is normalized by performing an affine transformation on a certain range around the identified positioning mark using the five ellipse parameters obtained by ellipse fitting. This affine transformation reconstructs the projected elliptical mark image into a circular image with a radius of r. Standardization of the code mark area is key to subsequent code recognition and is accomplished using the following formula:

[0082]

[0083] Where x′ and y′ are the pixel coordinates within a certain range of the ellipse center; x0 and y0 are the center coordinates of the standardized circle; P1, P 2 is the major and minor semi-axis of the ellipse; x and y are the normalized pixel coordinates; r is the radius of the normalized positioning marker, and θ is the angle between the encoding marker plane and the imaging plane. Figure 10 The first positioning mark 32 shows the normalized image.

[0084] The decoding of the coding mark is to convert the different coding bit distributions of the coding band into binary digital codes, thereby determining a specific magnetometer number. Since the lens orientation (imaging plane orientation) of the photographic device 41 is known (calibrated), the orientation of the coding mark plane (shooting angle), that is, the orientation of the magnetometer end face, can be calculated through the above-mentioned angle θ (affine parameter), the orientation of the lens of the photographic device 41, and the angle between the major axis of the ellipse and the viewfinder of the photographic device. By comparing the rotation angle between the imaged image and the standardized image, that is, the angle between the position of the coding stripe after image standardization in the mark and the position of the stripe in the baseline reference image, the rotation angle of the magnetometer along its longitudinal axis can be calculated, and then the three-axis spatial orientation of the magnetometer can be calculated.

[0085] In summary, the basic steps for calculating the spatial position and spatial orientation of a magnetometer based on coded markers include:

[0086] Extract the outline of the coding mark. Generally speaking, after the coding mark pattern is photographed by a photographic device, its center positioning mark is an ellipse. According to the image feature extraction algorithm, such as the ellipse fitting method or the grayscale weighted centroid method, the image coordinates of the ellipse center are determined, and the elliptical target image that meets the coding mark feature points is extracted from the image. Next, an image segmentation algorithm (such as the Canny operator) is used to segment the image, and the outline information representing different areas is extracted from the image. Then, the size, shape, grayscale change and position distribution features of the coding mark are combined to extract the elliptical outline that meets the conditions.

[0087] The decoding steps of the coding mark have been described in detail in the description of the above embodiment and will not be repeated here.

[0088] The unique identity of the magnetometer is determined based on the information on the coded tag, thereby classifying and numbering each magnetometer.

[0089] The code mark numbers are used to establish a corresponding matching relationship between the code marks in multiple images captured by one or more photographic devices. An image matching algorithm based on code marks can employ a relaxed labeling matching algorithm, which requires determining the similarity and compatibility of corresponding code marks. Methods for calculating similarity and compatibility are commonly used in the art.

[0090] After the initial matching is completed, false matches are eliminated. This can be based on the following criteria: similarity criterion, ambiguity criterion, or distance constraint error criterion.

[0091] After identification is complete, the spatial position of each coded marker can be calculated based on the collinearity equation or the coplanarity equation, and the spatial orientation of each coded marker can be calculated based on the affine transformation (ellipse fitting) and the rotation angle. And because the geometric shape and size parameters and insertion position of the magnetometer (i.e., the position relative to the coded marker) are known, the spatial position and spatial orientation of the magnetometer can be calculated.

[0092] In other embodiments, when the first positioning mark is a non-rotationally symmetric mark without coding information, the above steps can omit the steps of identifying and decoding the coding mark, and the calculation methods of the remaining spatial positions and spatial orientations are similar.

[0093] Figure 11 A flow chart of a method for magnetometer spatial positioning according to an embodiment of the present invention is shown. The method uses the system for magnetometer spatial positioning according to the aforementioned embodiment, and the method includes the following steps:

[0094] S101. A subject is received in the photogrammetry system 4, wherein the subject wears a magnetometer bracket 2, and at least one magnetometer 1 is provided on the magnetometer bracket 2;

[0095] S102. Capture first image data of first positioning marks 3 associated with magnetometer 1 at at least two of the plurality of capturing locations 43 using one or more imaging devices 41, where the first positioning marks 3 are rotationally asymmetric patterns.

[0096] S103. The controller receives the first image data captured by the photographic device 41 and identifies the first positioning mark 3 through the controller; and

[0097] S104 . Calculate the spatial position and spatial orientation of the first positioning marker 3 based on the system parameters and the first image data, and then calculate the spatial position and spatial orientation of the magnetometer 1 .

[0098] In step S101, the subject wears the magnetometer bracket 2 on the head or other parts of the body and receives it in the photogrammetry system 4. The magnetometer bracket 2 can be inserted in advance with the magnetometer 1 installed, or the magnetometer 1 can be inserted after the subject has finished wearing it. The magnetometer 1 is inserted into the mounting portion or other alternative mounting portion of the magnetometer bracket 2 along the insertion direction at a first insertion depth to be installed in place. In the case where the magnetometer bracket 2 is a helmet, the subject can wear the helmet and insert the magnetometer 1 into the mounting portion on the helmet and insert it to a predetermined distance from the subject's scalp. Optionally, the predetermined distance is zero. Then, the position adjustment device 44 can be adjusted so that the subject wearing the helmet is located in the photogrammetry system 4.

[0099] In step S102, one or more imaging devices 41 capture first image data of the first positioning marker 3 at at least two of the plurality of imaging locations 43. This step can be performed only once or in real time during the magnetometer 1 detection process. When step S103 is performed only once, the image data obtained is a static image. When step S103 is performed in real time, continuous recording and tracking can be achieved during the detection process.

[0100] In step S103, the controller receives the first image data captured by the imaging device 41 and identifies the first positioning mark through the controller. The method for identifying and decoding the coded mark is as described above and will not be repeated here. Because different first positioning marks have different coded information, after identifying a first positioning mark, the magnetometer 1 corresponding to the first positioning mark can be identified, thereby completing the identification and decoding of different magnetometers 1.

[0101] In step S104, the spatial position and spatial orientation of the first positioning mark are calculated based on the system parameters and the first image data, and the spatial position and spatial orientation of the magnetometer are then calculated. Specifically, for the identified first positioning mark 3, based on the initial position and shooting angle of the photographic device 41, a three-dimensional projection algorithm is used to calculate the three-dimensional coordinates of the first positioning mark 3 and the plane orientation of the encoding mark. The rotational orientation of the first positioning mark is calculated based on the recognition result, thereby calculating the spatial position and spatial orientation of the first positioning mark, and then calculating the spatial position and three-axis direction of the magnetometer. At the same time, three-dimensional magnetic field vector information is calculated based on the received magnetic field data of the magnetometer.

[0102] Optionally, the method also includes calibrating and / or inputting system parameters, and the calibrating system parameters mainly include calibrating the focal length, spatial position and shooting angle of the photographic device 41, and inputting the coded information of the first positioning mark 3 and the geometric size parameters of the magnetometer. For example, when the system includes a second positioning mark 6, calibrating the system parameters also includes inputting the coded information of the second positioning mark 6. The calibration and / or inputting system parameters can be performed before each subject receives a measurement, or can be performed at a certain time interval, such as during the daily, weekly or monthly routine maintenance of the system. The coded information of the first positioning mark 3 and the second positioning mark 6 includes the original image of the first positioning mark 3 and the second positioning mark 6 fixedly set, for example, on the end surface of the detector 11 of the magnetometer 1 or on the subject's head, and the image is an orthographic projection image that has not been deformed and rotated, that is, an image when photographed from the front.

[0103] Specifically, the calibration photography device 41 is implemented using a calibration plate, which is a commonly used device for calibrating a multi-camera industrial photogrammetry system.

[0104] Optionally, the method further includes capturing second image data of a second positioning marker 6 at at least two of the plurality of capturing locations 43 using one or more imaging devices 41. The second positioning marker 6 may have the same graphical characteristics and / or be made of the same material as the first positioning marker 3. Therefore, the identification and decoding methods for the second positioning marker 6 are the same as those for the first positioning marker 3. The controller receives the second image data and calculates the spatial location of the subject's head or other body part based on system parameters and the second image data, thereby achieving registration of the anatomical locations of the subject's head or other body part with the magnetometer support.

[0105] Optionally, the method further includes fixing a structural support system 42 in the shielded room 5 and accommodating the subject in the shielded room 5 .

[0106] Optionally, the method further includes continuously receiving image data from the photogrammetry system via a controller during the magnetometer measurement process to calculate, record, or track changes in the magnetometer's position / orientation in real time. The data continuously received during the magnetometer measurement process can be used to calculate, record, or track possible changes in the magnetometer's position / orientation during the recording process caused by the flexible magnetometer support in real time, thereby establishing more accurate three-dimensional information about the dynamic magnetic field process. Furthermore, this data can also be used for a range of other post-processing operations, such as background noise reduction and motion artifact correction.

[0107] In summary, the system and method for magnetometer spatial positioning based on coded marker photogrammetry proposed in the present invention have the advantage that only one system is needed to simultaneously calibrate the positions, pointing directions, and positional relationships of any number of magnetometers relative to human anatomical features. There is no need to add an active calibration device to each detector, eliminating the risk of electromagnetic interference caused by the calibration device to the magnetometer and significantly saving costs.

[0108] Furthermore, compared to active measurement devices based on built-in gyroscopes or electromagnetic digitizers, the present invention's system based on coded marker photogrammetry is a passive system. This eliminates the need to consider potential electromagnetic interference with the magnetometer, resulting in lower manufacturing costs for each magnetometer and faster and easier replacement of magnetometers or measurement devices. It also boasts higher spatial and angular resolutions, lower calibration errors, and allows for continuous recording while the magnetometer is operating. Compared to other passive calibration methods, the multi-camera photogrammetric optical system measurement device offers a fast calibration time of just a few seconds or less, significantly exceeding other passive calibration techniques, such as manual measurement, external electromagnetic digitizers, or ultrasonic digitizers.

[0109] Compared with markerless optical passive calibration methods such as depth cameras and handheld / multi-camera structured light, the system and method provided by the present invention have higher spatial / orientation measurement accuracy, and can automatically identify the corresponding channel number of each magnetometer based on the coded mark, and automatically identify the spatial relative position of the magnetometer. There is no need to arrange the magnetometers according to specific position correspondences, which reduces the possibility of misoperation and greatly improves the efficiency of installing and replacing magnetometers.

[0110] The exemplary embodiments of the system and method for spatial positioning of a magnetometer proposed in the present invention are described in detail above with reference to preferred embodiments. However, it will be understood by those skilled in the art that, without departing from the concept of the present invention, various modifications and variations can be made to the above-mentioned specific embodiments. For example, although an algorithm for calculating the spatial position and orientation of a magnetometer by positioning marks is described in detail above, the present invention is not limited thereto. Instead, any advantageous algorithm or simplified method can be adopted as long as the algorithm can achieve the required calculation accuracy. In addition, various technical features and structures proposed in various aspects of the present invention can also be combined in various ways without exceeding the scope of protection of the present invention, which is determined by the appended claims.

Claims

1. A system for magnetometer spatial positioning, comprising: a magnetometer configured to obtain magnetic field data related to brain magnetism or biomagnetic fields of other parts; a magnetometer support fixedly disposed relative to the subject's head or other body part and comprising at least one mounting portion having an orientation allowing the magnetometers to be disposed at a first depth along a specific direction, respectively, on the mounting portion; a first positioning mark, wherein the first positioning mark is a non-rotationally symmetric pattern and the first positioning mark is respectively associated with the magnetometer; a photogrammetry system, the photogrammetry system comprising a photographing device configured to photograph first image data of the first positioning mark at at least two photographing locations among a plurality of photographing locations by one or more of the photographing devices; as well as A controller is configured to receive first image data captured by the photographic device, and calculate the spatial position and spatial orientation of the first positioning mark based on pre-acquired system parameters and the first image data, and further calculate the spatial position and spatial orientation of the magnetometer.

2. The system according to claim 1, wherein: The system parameters include the focal length of the photographic device, the shooting angle of the photographic device, the spatial position coordinates of the photographic device, the coding information of the first positioning mark and / or the geometric size parameters of the magnetometer.

3. The system according to claim 2, wherein: The first positioning mark is fixedly arranged on the outer surface of the magnetometer, on an extension structure rigidly connected to the magnetometer, or on an auxiliary structure of the magnetometer bracket fixed relative to the magnetometer.

4. The system according to claim 3, wherein: The first positioning mark is a first coding mark, which is fixed relative to each magnetometer in a unique relationship. The first positioning mark is a planar or three-dimensional structure, and has the property of being non-deformable in rotation and scaling, so as to maintain geometric structure stability and uniqueness at different distances and angles.

5. The system according to claim 4, wherein: The first positioning mark is at least one of a ring-shaped coding mark, a dot-shaped coding mark, a square coding mark or a digital coding mark.

6. The system according to claim 4, wherein: The first positioning mark comprises a reflective material or an excited luminescent material to provide sufficient contrast under an illumination light source or an excitation light source.

7. The system according to claim 4, wherein: The first positioning mark includes an actively luminescent material.

8. The system according to any one of claims 1 to 7, further comprising: One or more second positioning markers, each of which is a non-rotationally symmetrical pattern and is fixedly disposed on the subject's head or other body part, or on an extended structure rigidly connected to the subject's head or other body part, wherein: The photographic device is configured to capture second image data of the second positioning mark at at least two of a plurality of photographic sites through one or more of the photographic devices, and the controller receives the second image data and calculates the spatial positioning of the subject's head or other body parts based on the system parameters and the second image data to achieve alignment of the anatomical points of the subject's head or other body parts with the magnetometer bracket.

9. The system according to claim 8, wherein: The second positioning mark is a second coding mark, which is fixedly arranged relative to the subject's head or other body parts in a unique relationship.

10. The system according to claim 9, wherein: The second positioning mark has the same graphic characteristics as the first positioning mark and / or is made of the same material as the first positioning mark.

11. The system according to claim 2, wherein: The photogrammetry system further comprises: The calibration device is used to calibrate the initial position and shooting angle of the photographic device.

12. The system according to claim 1, wherein: The photogrammetry system further comprises: A structural support system is provided with multiple photographing sites within a hemisphere or other shaped surface, wherein each photographing site is fixed with at least one photographing device, and / or at least one photographing device can be manually or automatically moved between different photographing sites, and / or at least one photographing device is fixed between adjacent photographing sites.

13. The system according to claim 12, wherein: The structural support system includes a position adjustment device configured to move or adjust a position of the photogrammetry system.

14. The system according to claim 12, wherein: The structural support system is fixedly arranged in the shielding room.

15. The system according to claim 14, wherein: The controller is configured to continuously receive image data from the photogrammetry system during the magnetometer measurement process to calculate, record or track the position and / or orientation changes of the magnetometer in real time.

16. The system of claim 12, wherein: The photogrammetry system further comprises a reference device for calibrating an initial position of the structural support system.

17. The system of claim 1, wherein: The photographic device is a camera or a video camera.

18. The system of claim 1, wherein: The magnetometer bracket is rigid or flexible.

19. The system according to any one of claims 1 to 18, wherein: The magnetometer bracket is a helmet.

20. The system according to any one of claims 2 to 19, wherein: The controller is configured to calculate the three-dimensional coordinates of the first positioning markers respectively by using collinear or coplanar equations, and calculate the spatial position of each magnetometer according to the calculated three-dimensional coordinates of the first positioning markers and the geometric parameters of the magnetometers.

21. The system of claim 20, wherein: The controller is configured to: Calculating the affine parameters of the first positioning mark by an affine transformation method; Calculate the spatial orientation of the plane where the first positioning mark is located by using the affine parameters, the system parameters and the first image data; By comparing the rotation angles of the first image data and the baseline reference image, the rotation angle of the first positioning mark in the plane in which the first positioning mark is located is calculated, thereby calculating the spatial orientation of the first positioning mark; as well as The spatial orientation of the magnetometer is calculated based on the geometric parameters of the magnetometer and the spatial orientation of the first positioning marker.

22. A method for spatial positioning using a magnetometer, comprising the following steps: receiving a subject in the photogrammetry system, the subject wearing a magnetometer bracket, and the magnetometer bracket being provided with at least one magnetometer; capturing, at at least two of the plurality of capturing locations, first image data of first positioning marks respectively associated with the magnetometer using one or more photographic devices, wherein the first positioning marks are rotationally asymmetric patterns; receiving, through the controller, first image data captured by the photographic device, and identifying, through the controller, a first positioning mark; as well as The spatial position and spatial orientation of the first positioning marker are calculated based on the system parameters and the first image data, and the spatial position and spatial orientation of the magnetometer are further calculated.

23. The method according to claim 22, wherein Calculating the spatial position of the first positioning mark includes calculating the three-dimensional coordinates of the first positioning mark respectively by using a collinear or coplanar equation; and Calculating the spatial position of the magnetometer includes calculating the spatial position of the magnetometer according to geometric parameters of the magnetometer and the three-dimensional coordinates of the first positioning mark.

24. The method according to claim 22, wherein Calculating the spatial orientation of the first positioning marker includes: Calculating the affine parameters of the first positioning mark by an affine transformation method; Calculate the spatial orientation of the plane where the first positioning mark is located by using the affine parameters, the system parameters and the first image data; Calculating the rotation angle of the first positioning mark within the plane in which it is located by comparing the rotation angle of the first image data with that of the baseline reference image, thereby calculating the spatial orientation of the first positioning mark; and The spatial orientation of the magnetometer is calculated based on the geometric parameters of the magnetometer and the spatial orientation of the first positioning marker.

25. The method according to claim 22, wherein The first positioning mark is fixedly arranged on the outer surface of the magnetometer, on an extension structure rigidly connected to the magnetometer, or on an auxiliary structure of the magnetometer bracket fixed relative to the magnetometer.

26. The method according to claim 25, wherein The first positioning mark is a first coding mark, which is fixed relative to each magnetometer in a unique relationship. The first positioning mark is a planar or three-dimensional structure, and has the property of being non-deformable in rotation and scaling, so as to maintain geometric structure stability and uniqueness at different distances and angles.

27. The method of claim 22, further comprising: capturing second image data of the second positioning mark at at least two of the plurality of capturing locations using one or more of the capturing devices; The second image data is received by the controller and the spatial positioning of the subject's head or other body parts is calculated according to the system parameters and the second image data to achieve alignment of the anatomical points of the subject's head or other body parts with the magnetometer bracket.

28. The method according to claim 27, wherein The second positioning mark is a second coded mark, which is fixedly arranged relative to the subject's head or other body parts in a unique relationship. The second positioning mark has the same graphic characteristics and / or is made of the same material as the first positioning mark, and the method for calculating the spatial position and spatial orientation of the second positioning mark is the same as the method for calculating the first positioning mark.

29. The method of claim 22, further comprising: The magnetometer controller continuously receives image data from the photogrammetry system to calculate, record or track the position and / or orientation changes of the magnetometer in real time.

30. The method according to claim 22 further includes calibrating system parameters, wherein the calibration system parameters include calibrating the shooting angle of the photographic device, the spatial position coordinates of the photographic device, the coding information of the first positioning mark and / or the geometric size parameters of the magnetometer.

31. The method of claim 22, further comprising: Calibrate and / or input system parameters, wherein the system parameters include the focal length of the photographic device, the shooting angle of the photographic device, the spatial position coordinates of the photographic device, the coding information of the first positioning mark and / or the geometric size parameters of the magnetometer.

32. The method according to claim 31, wherein The calibration and / or input of system parameters are performed at certain time intervals, or before each test on a subject.

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