Photomagnetic cascade combined navigation system and coordinate unification method

Abstract

The invention discloses an optomagnetic cascade combined navigation system and a coordinate unification method. The method comprises the following steps: taking an optical positioning system as a global coordinate system; according to the Y-shaped optical mark on the optical to-be-measured target, the pose of the optical to-be-measured target is obtained; establishing a local coordinate system based on the X-shaped optical mark on the magnetic field generator; establishing and calibrating a coordinate transformation matrix between the local coordinate system and the electromagnetic positioning coordinate system, and recording the coordinate transformation matrix as a to-be-calibrated matrix; measuring the X-shaped optical mark by using an optical positioning system, and establishing a transformation matrix of a global coordinate system and a local coordinate system; measuring the pose of the to-be-measured electromagnetic target in the magnetic field space based on an electromagnetic positioning system; and in combination with the to-be-calibrated matrix, obtaining an electromagnetic to-be-measured target pose under the global coordinate system. According to the method, the optical positioning working space and the electromagnetic positioning working space can be cascaded, the electromagnetic positioning working space can be flexibly adjusted in the working process, and mutual complementation of optical positioning and magnetic field positioning of the to-be-measured target in the working space is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical and magnetic hybrid navigation, and more specifically to an optical and magnetic cascade combined navigation system and a coordinate unification method. Background Art

[0002] The optical and magnetic hybrid navigation technology has the ability to measure the pose of the target without contact and perform surgical navigation, and is mostly used for measuring and tracking the poses of the affected parts of patients and surgical instruments in specific surgeries and medical robot-assisted surgeries. However, the existing optical and magnetic hybrid navigation technologies have disadvantages such as limited working space, interference of surgical instruments with electromagnetic positioning, and easy occlusion of surgical instruments to be tracked.

[0003] To avoid interfering with the surgical operation, it is necessary to adjust the position of the tracking device according to the surgical site to achieve a more accurate positioning effect; to unify the optical and magnetic coordinate systems with the computer CT or MR coordinate systems, it is necessary to use a probe to take points around the affected area and use a computer to run surface registration to obtain a transformation matrix to achieve the conversion and unification of the coordinate systems.

[0004] To unify the optical navigation coordinate system, the electromagnetic navigation coordinate system with the patient's CT or MR coordinates, there are mainly the following methods currently:

[0005] (1) For example, in the invention patent application with the publication number CN110101452A and the name of an optical and magnetic integrated positioning navigation method for surgical operations, an optical and magnetic integrated marker is fixedly connected to the patient, and an optical and magnetic integrated probe is used to extract physiological feature points around the affected area of the patient for point cloud registration to achieve the unification of the three coordinate systems in the optical and magnetic hybrid navigation system. However, it is necessary to install both optical markers and electromagnetic sensors on the probe and all surgical tools at the same time, and surgical tools made of metal materials in surgical operations have a great influence on the accuracy of electromagnetic positioning.

[0006] (2) For example, in the invention patent application with the publication number CN110584781A and the name of an optical and magnetic integrated intervertebral foramen mirror navigation platform, an optical marker and an electromagnetic probe are respectively used to register the optical coordinate system with the patient's CT or MR coordinates and the electromagnetic coordinate system with the patient's CT or MR coordinates to obtain an optical transformation matrix and an electromagnetic transformation matrix. The optical space coordinates are respectively converted into optical virtual reference coordinates, and the electromagnetic space coordinates are converted into electromagnetic virtual reference coordinates to achieve hybrid navigation. However, this system is limited by the fact that the optical and electromagnetic positioning systems must be kept fixed during the working process. Otherwise, if the relative pose changes, the system will fail, and the surgical space is limited within the smaller working range of electromagnetic positioning.

[0007] (3) For example, in the patent application of an optical and magnetic integrated surgical navigation system and a composite positioning marker with the publication number CN118285916 A and the name of "An Optical and Magnetic Integrated Surgical Navigation System and a Composite Positioning Marker", the coordinate transformation matrix between the optical navigation module and the electromagnetic navigation module is pre-calibrated to unify the coordinate systems of the two. However, it does not actually describe the calibration method and process, and the implementation method is not rigorous.

[0008] Therefore, how to cascade the optical positioning workspace and the electromagnetic positioning workspace, expand the electromagnetic positioning workspace, and simultaneously achieve decoupled measurement of optical positioning and magnetic field positioning is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0009] In view of the above problems, the present invention provides an optical and magnetic cascaded combined navigation system and a coordinate unification method, which are used to cascade the optical positioning workspace and the electromagnetic positioning workspace, expand the electromagnetic positioning workspace, and simultaneously achieve decoupled measurement of optical positioning and magnetic field positioning, so as to at least solve some of the technical problems mentioned in the above background technology.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] The present invention provides an optical and magnetic cascaded combined navigation system and a coordinate unification method, including the following steps:

[0012] Fix the optical positioning system, and use the optical positioning coordinate system corresponding to the optical positioning system as the global reference coordinate system; measure the pose of the optical target to be measured in the global reference coordinate system according to the Y-shaped optical marker on the optical target to be measured.

[0013] Fix the X-shaped optical marker on the magnetic field generator, and establish a local coordinate system based on the X-shaped optical marker.

[0014] There is a pose relationship between the local coordinate system and the electromagnetic positioning coordinate system corresponding to the magnetic field generator, and establish a matrix to be calibrated for the pose relationship.

[0015] Fix the magnetic field generator, and adjust the working position and viewing direction of the electromagnetic positioning system based on the magnetic field generator by force traction, so that the X-shaped optical marker is visible within the effective working space of the optical positioning system, and at the same time, the electromagnetic target to be measured is visible within the effective working space of the electromagnetic positioning system.

[0016] Use the optical positioning system to measure the X-shaped optical marker, and establish a transformation matrix between the global reference coordinate system and the local coordinate system; measure the pose of the electromagnetic target to be measured within the effective working space of the electromagnetic positioning system based on the electromagnetic positioning coordinate system; combine the matrix to be calibrated to realize the conversion of the pose of the electromagnetic target to be measured from the electromagnetic positioning coordinate system to the global reference coordinate system, and obtain the pose of the electromagnetic target to be measured in the global reference coordinate system.

[0017] Further, the fixation of the optical positioning system specifically includes:

[0018] Fix the optical positioning system to the bracket, determine the working position and viewing direction of the optical positioning system and fix them, and keep them unchanged throughout the working process.

[0019] Further, the origin of the local coordinate system is the center of the X-shaped optical marker; the XOY plane of the local coordinate system is the plane of the X-shaped optical marker.

[0020] Further, the calibration matrix to establish the pose relationship specifically includes:

[0021] Step 1: Place the magnetic field generator at position i within the effective working space of the optical positioning system, where i = 1,..., M, and M represents the total number of positions within the effective working space of the optical positioning system; place the marker board within the optimal working space of the electromagnetic positioning system.

[0022] Step 2: Use the optical probe and the electromagnetic probe respectively to obtain the coordinates of N marker points on the marker board in the space of the optical positioning system and the coordinates in the space of the electromagnetic positioning system when the magnetic field generator is at position i within the effective working space of the optical positioning system; and obtain the pose matrix of the X-shaped optical marker under the optical positioning system.

[0023] Step 3: Repeat Step 1 to Step 2 until all the magnetic field coordinate data and optical coordinate data of the N marker points are obtained when the magnetic field generator is at M positions within the effective working space of the optical positioning system.

[0024] Step 4: Based on the magnetic field coordinate data and optical coordinate data of the N marker points corresponding to the magnetic field generator at M positions, combined with the pose matrix of the X-shaped optical marker under the optical positioning system, establish a system of linear equations to obtain the calibration matrix; expressed as:

[0025]

[0026] Wherein, represents the pose matrix of the X-shaped optical marker under the optical positioning system when the magnetic field generator is at position i within the effective working space of the optical positioning system; represents the homogeneous coordinate data matrix of N marker points in the optical coordinate system when the magnetic field generator is at position i within the effective working space of the optical positioning system; represents the homogeneous coordinate data matrix of N marker points in the magnetic field coordinate system when the magnetic field generator is at position i within the effective working space of the optical positioning system; T {EM}→{LM} represents the calibration matrix.

[0027] Further, the transformation of the pose of the electromagnetic target to be measured from the electromagnetic positioning coordinate system to the global reference coordinate system is expressed as:

[0028]

[0029] Wherein, represents the homogeneous coordinates of the electromagnetic target to be measured in the global reference coordinate system, that is, the pose of the electromagnetic target to be measured in the global reference coordinate system; T {LM}→{W} represents the transformation matrix between the global reference coordinate system and the local coordinate system; T {EM}→{LM} represents the matrix to be calibrated; represents the homogeneous coordinates of the electromagnetic target to be measured in the electromagnetic coordinate system.

[0030] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a photomagnetic cascaded combined navigation system and a coordinate unification method, which have the following beneficial effects:

[0031] In the present invention, the optical positioning system in the photomagnetic hybrid navigation is used as the global coordinate system and fixed, and the electromagnetic navigation system can move its position arbitrarily and finely adjust the working area according to needs during the working process, so as to adapt to the precise navigation needs of different parts of the patient during the operation, effectively expand the working area of electromagnetic positioning in the operation, and improve the overall flexibility of the system. Since the working range of the optical positioning system is larger than that of the electromagnetic positioning system, in the larger working range of the global optical coordinate system, for the parts outside the working area of the electromagnetic positioning, the working area of the electromagnetic positioning is changed by moving the magnetic field generator, and the pose of the electromagnetic positioning coordinate system in the global reference coordinate system of the optical positioning is updated in real time, and then the pose of the target to be detected is determined, overcoming the limitations that the electromagnetic positioning system in the traditional photomagnetic hybrid navigation cannot move and the target to be tracked cannot be magnetically conductive, which helps to make the application of the photomagnetic hybrid navigation in surgical operations more extensive.

[0032] Next, through the drawings and embodiments, the technical solutions of the present invention will be further described in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only the embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0034] Figure 1 It is a schematic flow chart of the photomagnetic cascaded combined navigation system and the coordinate unification method provided by the embodiment of the present invention.

[0035] Figure 2Schematic diagram of the coordinate systems related to the optical positioning system and the electromagnetic positioning system provided by the embodiments of the present invention

[0036] Figure 3 Schematic diagram of the calibration board provided by the embodiments of the present invention

[0037] In the figure: 1 - optical positioning system; 2 - electromagnetic positioning system; 3 - X-shaped optical marker; 4 - global optical positioning system support; 5 - self-locking traction robotic arm; 6 - overweight movable base Specific embodiments

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention

[0039] The embodiments of the present invention disclose an optical-magnetic cascade combined navigation system and a coordinate unification method. Refer to Figure 1 as shown, and include the following steps

[0040] S1. Fix the optical positioning system and use the optical positioning coordinate system corresponding to the optical positioning system as the global reference coordinate system; measure the pose of the optical target to be measured in the global reference coordinate system according to the Y-shaped optical marker on the optical target to be measured

[0041] S2. Fix the X-shaped optical marker on the magnetic field generator and establish a local coordinate system based on the X-shaped optical marker

[0042] S3. There is a pose relationship between the local coordinate system and the electromagnetic positioning coordinate system corresponding to the magnetic field generator, and establish a calibration matrix of the pose relationship

[0043] S4. Fix the magnetic field generator, and adjust the working position and viewing direction of the electromagnetic positioning system based on the magnetic field generator by force traction, so that the X-shaped optical marker is visible within the effective working space of the optical positioning system, and at the same time, the electromagnetic target to be measured is visible within the effective working space of the electromagnetic positioning system

[0044] S5. Use the optical positioning system to measure the X-shaped optical marker and establish a transformation matrix between the global reference coordinate system and the local coordinate system; measure the pose of the electromagnetic target to be measured within the effective working space of the electromagnetic positioning system based on the electromagnetic positioning coordinate system; combine the calibration matrix to realize the transformation of the pose of the electromagnetic target to be measured from the electromagnetic positioning coordinate system to the global reference coordinate system, and obtain the pose of the electromagnetic target to be measured in the global reference coordinate system

[0045] The above-mentioned marks S1 - S5 are only for facilitating subsequent descriptions and do not limit the operation sequence between steps. Next, each of the above steps will be described separately.

[0046] In the above step S1, it specifically includes:

[0047] (1) Fix the optical positioning system 1:

[0048] Fix the optical positioning system 1 to the bracket. After determining the working position and viewing direction of the optical positioning system 1, fix it and keep it unchanged throughout the working process. Specifically, refer to Figure 2 As shown, select the NDIPolaris infrared binocular pose sensing system for the optical positioning system 1. Fix the optical positioning system 1 to the global optical positioning system bracket 4 on the edge of the operating table according to the surgical needs, select a suitable working position and viewing direction, and lock the bracket. The bracket can use a three-joint hydraulic locking and adjusting robotic arm. The form of the bracket is not limited here, but it is necessary to ensure that the optical positioning system 1 can be kept stable;

[0049] (2) Use the optical positioning coordinate system corresponding to the optical positioning system 1 as the global reference coordinate system {W}:

[0050] Take the left-eye camera coordinate system O0 - X0Y0Z0 in the optical positioning system 1 as the global reference coordinate system in the physical world, and denote it as {W};

[0051] (3) According to the Y-shaped optical mark on the optical target to be measured X OPT Measure the pose of the optical target to be measured X in the global reference coordinate system, and denote it as the pose of the optical target to be measured OPT

[0052] In the above step S2, fix the X-shaped optical mark 3 to the magnetic field generator, and establish a local coordinate system based on the X-shaped optical mark 3; denote the X-shaped optical mark 3 as Marker EM ; In the embodiment of the present invention, the X-shaped optical marker is composed of passive reflective marker balls;

[0053] The schematic diagram of the local coordinate system is as shown in Figure 2 Take the center of the X-shaped optical mark Marker EM as the origin of the local coordinate system, and take the plane of the X-shaped optical mark Marker EM as the XOY plane of the local coordinate system, so as to establish the local coordinate system O LM -X LM Y LM Z LM ; For the convenience of description, denote the local coordinate system as {LM};

[0054] Among them, the X-shaped optical marker Marker EM is a model composed of multiple non-collinear passive reflective spheres on a plane, which has uniqueness, that is, the X-shaped optical marker Marker fixedly connected to the magnetic field generator EM is different from the reflective marker models on the probe and the surgical tool, and is used to distinguish in optical positioning;

[0055] In the above step S3, there is a pose relationship between the local coordinate system {LM} and the electromagnetic positioning coordinate system {EM} corresponding to the magnetic field generator, and a calibration matrix to establish this pose relationship; specifically including:

[0056] Step 1: Place the magnetic field generator at position i within the effective working space of the optical positioning system, where i = 1,..., M, and M represents that there are M positions in the effective working space of the optical positioning system; place the marker board within the optimal working space of the electromagnetic positioning system 2; the schematic diagram of the marker board is as Figure 3 shown, and there are N marker points on the marker board that are adapted to the positions of the optical probe and the electromagnetic probe, denoted as P1,..., P N , where P n represents the nth (n = 1,..., N) marker point; in the embodiment of the present invention, the NDI Aurora electromagnetic positioning system is selected;

[0057] Step 2: Respectively use the optical probe and the electromagnetic probe to obtain the coordinates of the N marker points on the marker board in the space of the optical positioning system and the coordinates in the space of the electromagnetic positioning system when the magnetic field generator is at position i within the effective working space of the optical positioning system; and obtain the pose matrix of the X-shaped optical marker Marker EM under the optical positioning system 1;

[0058] When the above magnetic field generator is at position i within the effective working space of the optical positioning system, the magnetic field coordinate data corresponding to the N marker points is expressed as: Among them, represents the magnetic field coordinate data of the nth (n = 1,..., N) marker point corresponding to the magnetic field generator at position i within the effective working space of the optical positioning system;

[0059] When the above magnetic field generator is at position i within the effective working space of the optical positioning system, the optical coordinate data corresponding to the N marker points is expressed as: Among them, represents the optical coordinate data of the nth (n = 1,..., N) marker point corresponding to the magnetic field generator at position i within the effective working space of the optical positioning system;

[0060] The above X-shaped optical marker EM The pose matrix of the X-shaped optical marker under the optical positioning system 1 is denoted as

[0061] Step 3: Repeat steps S3.1 - S3.2 until all the magnetic field coordinate data and optical coordinate data of the N marker points are obtained at M positions of the magnetic field generator within the effective working space of the optical positioning system;

[0062] Step 4: Based on the magnetic field coordinate data and optical coordinate data of the N marker points corresponding to the magnetic field generator at M positions, combined with the pose matrix of the X-shaped optical marker under the optical positioning system 1, substitute into the following formula to construct a system of linear equations, and use quaternions or SVD to solve for the matrix T to be calibrated {EM}→{LM} ;

[0063]

[0064] Among them, represents the pose matrix of the X-shaped optical marker under the optical positioning system when the magnetic field generator is at position i within the effective working space of the optical positioning system; represents the homogeneous coordinate data matrix of the N marker points in the optical coordinate system when the magnetic field generator is at position i within the effective working space of the optical positioning system; represents the homogeneous coordinate data matrix of the N marker points in the magnetic field coordinate system when the magnetic field generator is at position i within the effective working space of the optical positioning system; T {EM}→{LM} represents the matrix to be calibrated.

[0065] In the above step S4, it specifically includes:

[0066] (1) Fix the magnetic field generator:

[0067] Fix the magnetic field generator to the movable base 6 through a bracket, which is convenient for moving and adjusting the working range; the form of the bracket can be set according to actual needs, for example, a self-locking traction robotic arm 5 can be selected; the weight of the movable base needs to reach a preset value to ensure the stability of the bracket.

[0068] (2) Adjust the working position and viewing direction of the electromagnetic positioning system 2 based on the magnetic field generator through force traction, so that the X-shaped optical marker EM is visible within the effective working space of the optical positioning system 1, and at the same time, the electromagnetic target X to be measured is visible within the effective working space of the electromagnetic positioning system.

[0069] In the above step S5, it specifically includes:

[0070] (1) Use the optical positioning system 1 to measure the X-shaped optical marker EMAt its position, obtain its position and orientation in the global reference coordinate system {W}, and obtain the transformation matrix between the global reference coordinate system {W} and the local coordinate system {LM}, denoted as T {LM}→{W} 。

[0071] (2) Based on the electromagnetic positioning coordinate system {EM}, measure the position of the electromagnetic target to be measured X within the effective working space of the electromagnetic positioning system, denoted as X {EM} ;

[0072] (3) Based on the transformation matrix T {LM}→{W} and the position X of the electromagnetic target to be measured within the effective working space of the electromagnetic positioning system {EM} , combined with the calibration matrix T {EM}→{LM} obtained above, realize the transformation of the position and orientation of the electromagnetic target to be measured from the electromagnetic positioning coordinate system to the global reference coordinate system; specifically expressed as:

[0073]

[0074] wherein, represents the homogeneous coordinates of the electromagnetic target to be measured X in the global reference coordinate system {W}, that is, the position and orientation of the electromagnetic target to be measured in the global reference coordinate system; represents the homogeneous coordinates of the electromagnetic target to be measured X in the electromagnetic coordinate system {EM}; is the homogeneous coordinate of X = [x y z] T (x, y, z) represents the coordinates of the electromagnetic target to be measured X in the electromagnetic three-dimensional space coordinate system.

[0075] In summary, the embodiment of the present invention provides an optical-magnetic cascade combined navigation system and a coordinate unification method. The optical navigation system with a larger working range is used as the global vision system and fixed, and the electromagnetic navigation system with a smaller working range can be moved and adjusted according to needs during the operation, so as to effectively expand the working space of the electromagnetic positioning system and improve the flexibility of the optical-magnetic hybrid navigation system. When a large range of electromagnetic positioning is required during the operation, the working range can be adjusted by moving the magnetic field generator, overcoming the limitation that the optical-magnetic coordinate system cannot adjust the position and orientation during the operation in the traditional optical-magnetic hybrid navigation, making the application range of the system wider; for surgical instruments made of metal, the optical positioning and electromagnetic positioning are cascaded and the electromagnetic target to be measured is decoupled, and its position in the global coordinate system and the computer CT or MR coordinates can be obtained through optical positioning, preventing the influence of metal instruments on electromagnetic positioning. Applying the present invention to the navigation of operating room instruments has the advantages of low cost, flexible working space and high positioning accuracy.

[0076] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference may be made to each other.

[0077] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A photomagnetic cascade combined navigation system and coordinate unification method, characterized in that It includes the following steps: Fix the optical positioning system and use the optical positioning coordinate system corresponding to the optical positioning system as the global reference coordinate system; measure the pose of the optical target to be measured in the global reference coordinate system according to the Y-shaped optical mark on the optical target to be measured. Fix the X-shaped optical mark on the magnetic field generator and establish a local coordinate system based on the X-shaped optical mark. There is a pose relationship between the local coordinate system and the electromagnetic positioning coordinate system corresponding to the magnetic field generator, and establish a calibration matrix for the pose relationship. Fix the magnetic field generator, and adjust the working position and viewing direction of the electromagnetic positioning system based on the magnetic field generator by force traction, so that the X-shaped optical mark is visible within the effective working space of the optical positioning system, and at the same time the electromagnetic target to be measured is visible within the effective working space of the electromagnetic positioning system. Use the optical positioning system to measure the X-shaped optical mark and establish a transformation matrix between the global reference coordinate system and the local coordinate system; measure the pose of the electromagnetic target to be measured within the effective working space of the electromagnetic positioning system based on the electromagnetic positioning coordinate system; combine the calibration matrix to realize the conversion of the pose of the electromagnetic target to be measured from the electromagnetic positioning coordinate system to the global reference coordinate system, and obtain the pose of the electromagnetic target to be measured in the global reference coordinate system.

2. The optical magnetic cascade combined navigation system and coordinate unification method according to claim 1, characterized in that The fixing of the optical positioning system specifically includes: Fix the optical positioning system to the bracket, determine and fix the working position and viewing direction of the optical positioning system, and keep it unchanged throughout the working process.

3. A photomagnetic cascade integrated navigation system and coordinate unification method according to claim 1, characterized in that The origin of the local coordinate system is the center of the X-shaped optical mark; the XOY plane of the local coordinate system is the plane of the X-shaped optical mark.

4. A photomagnetic cascade integrated navigation system and coordinate unification method according to claim 1, characterized in that The establishment of the calibration matrix for the pose relationship specifically includes: Step 1: Place the magnetic field generator at position i within the effective working space of the optical positioning system, where i = 1,..., M, and M represents that there are M positions in the effective working space of the optical positioning system; place the marker plate within the optimal working space of the electromagnetic positioning system. Step 2: Use the optical probe and the electromagnetic probe respectively to obtain the coordinates of N marker points on the marker plate in the space of the optical positioning system and the coordinates in the space of the electromagnetic positioning system when the magnetic field generator is at position i within the effective working space of the optical positioning system; and obtain the pose matrix of the X-shaped optical mark under the optical positioning system. Step 3: Repeat Step 1 to Step 2 until all the magnetic field coordinate data and optical coordinate data of the N marker points are obtained when the magnetic field generator is at M positions within the effective working space of the optical positioning system. Step 4: Based on the magnetic field coordinate data and optical coordinate data of the N marker points corresponding to the magnetic field generator at M positions, combined with the pose matrix of the X-shaped optical mark under the optical positioning system, establish a linear equation system to obtain the calibration matrix; expressed as: Among them, represents the pose matrix of the X-shaped optical marker under the optical positioning system when the magnetic field generator is at position i within the effective working space of the optical positioning system; represents the homogeneous coordinate data matrix of N marker points in the optical coordinate system when the magnetic field generator is at position i within the effective working space of the optical positioning system; represents the homogeneous coordinate data matrix of N marker points in the magnetic field coordinate system when the magnetic field generator is at position i within the effective working space of the optical positioning system; T {EM}→{LM} represents the matrix to be calibrated.

5. A photomagnetic cascade combined navigation system and coordinate unification method according to claim 1, characterized in that, The conversion of the pose of the electromagnetic target to be measured from the electromagnetic positioning coordinate system to the global reference coordinate system is expressed as: Among them, represents the homogeneous coordinates of the electromagnetic target to be measured in the global reference coordinate system, that is, the pose of the electromagnetic target to be measured in the global reference coordinate system; T {LM}→{W} represents the transformation matrix between the global reference coordinate system and the local coordinate system; T {EM}→{LM} represents the matrix to be calibrated; represents the homogeneous coordinates of the electromagnetic target to be measured in the electromagnetic coordinate system.

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