Control device, endoscope system, and position detection method

Abstract

The control device (26) is provided with a processor (26a). The processor (26a) selects candidate coordinates of the magnetic field generating element (22), calculates a candidate vector (Gk) and a vector norm error (e1) on the basis of coordinates of the magnetic field detecting element (23), the candidate coordinates, and the detection signal, updates the maximum likelihood coordinates to the current candidate coordinates when the vector norm error (e1) is less than a past minimum value, and outputs the updated maximum likelihood coordinates to the current candidate coordinates. Whether the vector norm error (e1) is within the first range is determined, and a new candidate coordinate is selected if the vector norm error (e1) is not within the first range.

Description

TECHNICAL FIELD

[0001] The present application relates to a control device that detects a position of an endoscope using a magnetic field, an endoscope system, and a position detection method. BACKGROUND

[0002] An endoscope device has been used in various fields such as a medical field, an industrial field, an academic field, and the like. An endoscope is used in such a manner that an insertion portion is inserted into a subject to observe the inside of the subject.

[0003] For example, in the medical field, the demand for examination using a colonoscope is increasing. The difficulty of an insertion procedure in colonoscopy is high. Therefore, a technique has been proposed in which the shape of an insertion portion of an endoscope is grasped by using an endoscope insertion shape detection device (UPD), and the insertion procedure can be smoothly performed.

[0004] The endoscope insertion shape detection device, for example, arranges a plurality of transmission coils in the insertion portion of the endoscope, and arranges a plurality of reception coils at an antenna outside a body cavity. Then, a magnetic field is generated by the transmission coil, and a voltage generated in the reception coil by the generated magnetic field is detected, whereby the position and direction of the transmission coil are estimated. If the positions and directions of the plurality of transmission coils arranged in the insertion portion can be estimated respectively, the shape of the insertion portion of the endoscope can be estimated.

[0005] For example, in Japanese Patent No. 5231681, an example of a shape detection device using a magnetic field is described. The shape detection device calculates a candidate vector indicating the direction of the transmission coil on the basis of a search coordinate set (virtual three-dimensional coordinates) of the transmission coil and a measured voltage of a certain reception coil group. Then, the shape detection device sets a coordinate set that minimizes the sum of errors between an estimated electromotive force of other reception coil groups calculated on the basis of the search coordinate set and the candidate vector and a measured voltage measured by the other reception coil groups as a solution (estimated coordinates). If this method is used, the amount of calculation and the amount of search can be reduced, and the estimation result (the position and direction of the transmission coil) can be obtained quickly.

[0006] However, in the technique described in Japanese Patent No. 5231681, if the calculation result of the candidate vector is greatly different from the true value, the solution sometimes falls into a local minimum value (a minimum value of an evaluation function different from the true value) and converges to a point completely different from the true value. The convergence of the solution to a point completely different from the true value sometimes occurs, for example, when the transmission coil is arranged at a close point of the reception coil. Therefore, the technique described in Japanese Patent No. 5231681 is not suitable for a case where the antenna in which the reception coil is arranged is arranged at a close point of the endoscope.

[0007] On the other hand, in principle, the farther the distance between the transmission coil as the magnetic field generating element and the reception coil as the magnetic field detecting element, the greater the influence of noise and the lower the detection accuracy.

[0008] Thus, a technique is sought in which even if the distance between the magnetic field generating element and the magnetic field detecting element is made close, the solution does not converge to a point different from the true value, and the detection accuracy can be improved.

[0009] The present application was achieved in view of the above-described circumstances, and aims to provide a control device, an endoscope system, and a position detection method capable of quickly estimating the relative position and direction of a magnetic field generating element and a magnetic field detecting element within a wide range including a near point of the magnetic field detecting element with a small amount of calculation. SUMMARY

[0010] Solution to Problem

[0011] A control device of one embodiment of the present application includes a processor that performs processing of selecting a candidate coordinate of a magnetic field generating element, calculating a candidate vector on the basis of a coordinate of a magnetic field detecting element, the candidate coordinate, and a detection signal that the magnetic field detecting element detects and transmits from the magnetic field generating element, calculating a vector norm error on the basis of the candidate vector, updating a maximum likelihood coordinate to the current candidate coordinate in a case where the calculated vector norm error is smaller than a minimum value of the vector norm error calculated in the past, determining whether the vector norm error is within a first range, and selecting a new candidate coordinate in a case where the vector norm error is not within the first range.

[0012] An endoscope system of one embodiment of the present application includes an endoscope, a magnetic field generating element that generates a magnetic field, a magnetic field detecting element that detects the magnetic field and transmits a detection signal, and a processor that processes the detection signal, in which the processor performs processing of selecting a candidate coordinate of the magnetic field generating element, calculating a candidate vector on the basis of a coordinate of the magnetic field detecting element, the candidate coordinate, and the detection signal, calculating a vector norm error on the basis of the candidate vector, updating a maximum likelihood coordinate to the current candidate coordinate in a case where the calculated vector norm error is smaller than a minimum value of the vector norm error calculated in the past, determining whether the vector norm error is within a first range, and selecting a new candidate coordinate in a case where the vector norm error is not within the first range.

[0013] In a position detection method of one embodiment of the present application, a magnetic field is generated by a magnetic field generating element, the magnetic field is detected by a magnetic field detecting element and a detection signal is transmitted, a candidate coordinate of the magnetic field generating element is selected, a candidate vector is calculated on the basis of a coordinate of the magnetic field detecting element, the candidate coordinate, and the detection signal, a vector norm error is calculated on the basis of the candidate vector, in the case where the calculated vector norm error is smaller than a minimum value of past calculated vector norm errors, a maximum likelihood coordinate is updated to the current candidate coordinate, it is determined whether the vector norm error is within a first range, and in the case where the vector norm error is not within the first range, a new candidate coordinate is selected. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 FIG. 1 is a diagram illustrating a structure of an endoscope system of a first embodiment of the present application.

[0015] Figure 2 FIG. 2 is a diagram illustrating a structure example in which a magnetic field generating element is provided to an endoscope and a magnetic field detecting element is provided to an antenna outside the endoscope in the above first embodiment.

[0016] Figure 3 FIG. 3 is a diagram illustrating a structure example of the magnetic field detecting element in the above first embodiment.

[0017] Figure 4 FIG. 4 is a diagram illustrating a structure example in which a signal detected by a reception coil included in the magnetic field detecting element is amplified and converted into a digital signal and then transmitted to a magnetic field detecting unit in the above first embodiment.

[0018] Figure 5 FIG. 5 is a diagram illustrating a structure of a position detection system in the above first embodiment.

[0019] Figure 6 FIG. 6 is a diagram illustrating an example in which one of a plurality of grid point coordinates within a predetermined spatial range centered on a search center coordinate is selected as a candidate coordinate in the above first embodiment.

[0020] Figure 7 FIG. 7 is a flow chart illustrating a part of a transmission coil coordinate estimation process in the above first embodiment.

[0021] Figure 8 FIG. 8 is a flow chart illustrating a stage 1 process which is a part of the transmission coil coordinate estimation process in the above first embodiment.

[0022] Figure 9 FIG. 9 is a flow chart illustrating a stage 2 process which is a part of the transmission coil coordinate estimation process in the above first embodiment.

[0023] Figure 10 is a view showing a configuration example in which a magnetic field detection element is provided to an endoscope and a magnetic field generation element is provided to an antenna outside the endoscope in the second embodiment of the present application.

[0024] Figure 11 is a view showing a configuration example in which a signal detected by a reception coil possessed by a magnetic field detection element is amplified in a manner that an amplification rate can be changed, then converted into a digital signal, and transmitted to a magnetic field detection unit in the third embodiment of the present application.

[0025] Figure 12 is a view showing a configuration of a position detection system in the fourth embodiment of the present application.

[0026] Figure 13 is a flowchart showing stage 1 processing that is a part of transmission coil coordinate estimation processing in the fourth embodiment of the present application.

[0027] Figure 14 is a flowchart showing stage 2 processing that is a part of transmission coil coordinate estimation processing in the fourth embodiment of the present application. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. However, the present application is not limited to the embodiments described below.

[0029] Further, in the description of the drawings, the same reference numerals are applied to the same or corresponding elements as appropriate. In addition, it should be noted that the drawings are schematic, and the relationship of the lengths of the respective elements, the ratio of the lengths of the respective elements, the number of the respective elements, and the like within one drawing are sometimes different from reality in order to make the description simple. Also, sometimes, a plurality of drawings include parts different from each other in the relationship of the lengths, the ratio, the number, and the like.

[0030] [First Embodiment]

[0031] Figures 1 to 9 is a view showing the first embodiment of the present application. Figure 1 is a view showing a configuration of an endoscope system 1 of the first embodiment.

[0032] As shown in Figure 1 , the endoscope system 1 includes a position detection system 2, an endoscope 3, a light source device 4, a video processor 5, and a monitor 6.

[0033] The endoscope 3 includes an insertion portion 11 inserted into a subject and an operation portion 12 provided to a base end of the insertion portion 11.

[0034] The insertion section 11 is assumed to be of a type having a flexible tube section and a bending section, i.e., a shape-changing type. An objective lens 15 and an imaging element 16 are provided at a front end section 14 of the insertion section 11.

[0035] Also, a magnetic field generating element 22 is provided at the insertion section 11 including the front end section 14. The magnetic field generating element 22 generates a magnetic field MF (refer to Figure 2 and the like). The magnetic field generating element 22 has, for example, a plurality of transmission coils C1 to Cn. The plurality of transmission coils C1 to Cn are arranged in a prescribed interval in the longitudinal direction of the insertion section 11 from the front end side.

[0036] Various switches 12a for operating the endoscope 3 are provided at the operation section 12.

[0037] Also, a memory 17 is provided in the endoscope 3, for example, in the operation section 12 (where, if inside the endoscope 3, it can also be a portion other than the operation section 12). The memory 17 non-volatile stores various information related to the endoscope 3. Examples of the information stored in the memory 17 are the model of the endoscope 3, the manufacturing number, parameters unique to the endoscope 3, and the like. The memory 17 is connected to the video processor 5, and transmits various information related to the endoscope 3 to the video processor 5.

[0038] In addition, a bending operation knob or the like for performing a bending operation on the bending section is also provided at the operation section 12.

[0039] The endoscope 3 is provided with a light guide 13 in the longitudinal direction from the front end section 14 of the insertion section 11. The base end of the light guide 13 is connected to the light source device 4. The light guide 13 is used to transmit illumination light supplied from the light source device 4, and irradiate the illumination light from the front end section 14 toward the subject.

[0040] The objective lens 15 images the optical image of the subject irradiated with the illumination light on the imaging element 16. The imaging element 16 photographs the optical image of the subject, and transmits an imaging signal to the video processor 5.

[0041] The video processor 5 receives the imaging signal from the imaging element 16, and performs image processing on the imaging signal based on various information related to the endoscope 3 received from the memory 17, thereby generating a video signal. The video processor 5 transmits the video signal to the monitor 6.

[0042] The monitor 6 receives the video signal transmitted from the video processor 5, and thereby displays an endoscopic image of the subject.

[0043] The position detection system 2 includes a position detection device 21, a magnetic field generating element 22, and a magnetic field detection element 23. That is, the magnetic field generating element 22 is provided, for example, in the endoscope 3, but constitutes a part of the position detection system 2.

[0044] The position detection apparatus 21 includes a drive signal transmission section 24, a magnetic field detection section 25, and a control section 26.

[0045] The drive signal transmission section 24 transmits a drive signal (for example, an alternating current signal for generating an alternating magnetic field) for generating the magnetic field MF to the magnetic field generating element 22 based on the control of the control section 26.

[0046] The drive signal transmission section 24, for example, simultaneously transmits alternating current signals of different frequencies to the transmission coils C1 to Cn. Then, the transmission coils C1 to Cn generate alternating magnetic fields of different frequencies. In this case, it is possible to distinguish the magnetic field MF generated from which transmission coil C1 to Cn according to the frequency of the alternating magnetic field.

[0047] In addition, the drive signal transmission section 24 can also sequentially transmit an alternating current signal to any one of the transmission coils C1 to Cn while switching the transmission coil C1 to Cn to which the alternating current signal is to be transmitted. In this case, it is possible to distinguish the magnetic field MF generated from which transmission coil C1 to Cn according to the timing of generation of the alternating magnetic field.

[0048] Figure 2 is a diagram showing a configuration example in which the magnetic field generating element 22 is provided to the endoscope 3 and the magnetic field detection element 23 is provided to the antenna 28 outside the endoscope 3 in the first embodiment.

[0049] The magnetic field detection element 23 detects the magnetic field MF and transmits a detection signal. As shown in Figure 2 , the magnetic field detection element 23 is configured as, for example, an antenna 28 (a receiving antenna in the example of Figure 2 ) that can move the position by a caster or the like. The antenna 28 is disposed in the periphery of, for example, an examination table for placing a subject in an examination room (outside the body cavity). Furthermore, the coordinates of the magnetic field detection element 23 after the antenna 28 is disposed are known.

[0050] The magnetic field detection element 23 includes a plurality of reception coil groups, and in the present embodiment, an example in which four reception coil groups 23g1 to 23g4 are provided is shown. The four reception coil groups 23g1 to 23g4 are disposed on the antenna 28 in a manner such that the positions are different.

[0051] Figure 3 is a diagram showing a configuration example of the magnetic field detection element 23 in the first embodiment. In Figure 3 , an xyz coordinate system is a three-dimensional orthogonal coordinate system. The xyz coordinate system is referred to as a global coordinate system or a world coordinate system.

[0052] The reception coil group 23gl includes, as a group, an x-direction reception coil SCxl whose central axis is parallel to the x-axis direction, a y-direction reception coil SCyl whose central axis is parallel to the y-axis direction, and a z-direction reception coil SCzl whose central axis is parallel to the z-axis direction. The x-direction reception coil SCxl, the y-direction reception coil SCyl, and the z-direction reception coil SCzl detect magnetic field components in the orthogonal xyz-axis directions, respectively.

[0053] That is, the x-direction reception coil SCxl generates an electromotive force corresponding to an x-axis direction magnetic field component of the magnetic field MF generated by the transmission coils Cl to Cn at the position of the x-direction reception coil SCxl. The y-direction reception coil SCyl generates an electromotive force corresponding to a y-axis direction magnetic field component of the magnetic field MF generated by the transmission coils Cl to Cn at the position of the y-direction reception coil SCyl. The z-direction reception coil SCzl generates an electromotive force corresponding to a z-axis direction magnetic field component of the magnetic field MF generated by the transmission coils Cl to Cn at the position of the z-direction reception coil SCzl.

[0054] The reception coil group 23g2 also includes, as a group, an x-direction reception coil SCx2, a y-direction reception coil SCy2, and a z-direction reception coil SCz2, which generate electromotive forces corresponding to the magnetic field components in the respective directions.

[0055] The reception coil group 23g3 also includes, as a group, an x-direction reception coil SCx3, a y-direction reception coil SCy3, and a z-direction reception coil SCz3, which generate electromotive forces corresponding to the magnetic field components in the respective directions.

[0056] The reception coil group 23g4 also includes, as a group, an x-direction reception coil SCx4, a y-direction reception coil SCy4, and a z-direction reception coil SCz4, which generate electromotive forces corresponding to the magnetic field components in the respective directions.

[0057] Further, any of the reception coils SCxl to SCz4 will be simply referred to as a reception coil SC hereinafter.

[0058] Figure 4 is a diagram showing a configuration example in which a signal detected by the reception coil SC possessed by the magnetic field detection element 23 is amplified and converted into a digital signal and transmitted to the magnetic field detection unit 25 in the first embodiment.

[0059] When the magnetic field MF that penetrates the reception coil SC changes over time, an electromotive force that changes over time is generated at both ends of the reception coil SC, and thus a current (alternating current) flows.

[0060] The electromotive force generated at both ends of the reception coil SC is detected and amplified by the amplifier 38, converted into a digital signal by the analog-digital converter (ADC) 39, and transmitted to the magnetic field detection section 25 as a detection signal.

[0061] At least one of the amplifier 38 and the ADC 39 can be provided in the position detection device 21 (for example, in the magnetic field detection section 25) or in the antenna 28. For example, if the amplifier 38 and the ADC 39 are provided in the position detection device 21, the antenna 28 can be made simple and inexpensive.

[0062] In addition, the farther the distance from the transmission coils C1 to Cn to the reception coil SC, the smaller the electromotive force generated in the reception coil SC. Therefore, if the amplifier 38 and the ADC 39 are provided in the antenna 28, for example, it is possible to reduce distortion of the signal, mixing of noise, and the like of the signal generated by the reception coil SC when the signal is transmitted from the antenna 28 to the position detection device 21.

[0063] The magnetic field detection section 25 separates the detection signal (average reception voltage amplitude of a certain time obtained by Fourier conversion of voltage) transmitted from the reception coil SC via the amplifier 38 and the ADC 39, for example, by frequency separation (or separation according to time), and transmits the signals of the reception coil groups 23g1, 23g2, 23g3, and 23g4 to the control section 26.

[0064] The control section 26 is a control device, for example, having a processor 26a and a memory 26b. That is, the control section 26 has a structure in which the functions of the respective sections described later are realized by reading and executing a processing program stored in a storage device (or a recording medium) such as the memory 26b by the processor 26a such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or the like. However, the structure of the control section 26 is not limited thereto, and each section can be configured as a dedicated electronic circuit that realizes the functions of each section.

[0065] The processor 26a processes the detection signal received from the magnetic field detection section 25. The processor 26a performs processing of detecting the positions and directions of the transmission coils C1 to Cn based on the detection signal, as described later.

[0066] The arrangement of the transmitting coils C1 to Cn within the insertion section 11 along its long side is known. Therefore, if the position and orientation of each of the transmitting coils C1 to Cn are known, the processor 26a can detect the shape of the insertion section 11.

[0067] The position detection device 21 is connected to the video processor 5. Based on the detected shape of the insertion part 11, the position detection device 21 generates, for example, an image representing the shape of the insertion part 11, insertion assistance information, etc., and sends the generated information to the video processor 5. The video processor 5 displays the information received from the position detection device 21 together with the endoscopic image on the monitor 6, thereby performing insertion assistance, etc.

[0068] Figure 5 This is a diagram showing the structure of the position detection system 2 in the first embodiment.

[0069] like Figure 5 As shown, the control unit 26 includes a candidate coordinate selection unit 31, a candidate vector calculation unit 32, a candidate vector norm error calculation unit 33, an estimated electromotive force calculation unit 34, a standardized voltage error calculation unit 35, and an estimated coordinate acquisition unit 36 ​​as functional units.

[0070] The candidate coordinate selection unit 31 selects the candidate coordinates of the magnetic field generating element 22.

[0071] The candidate vector calculation unit 32 calculates the candidate vector G based on the coordinates of the magnetic field detection element 23, the candidate coordinates of the magnetic field generating element 22, and the detection signal received from the magnetic field detection unit 25. k .

[0072] Candidate vector norm error calculation unit 33 based on candidate vector G k We calculate the candidate vector norm error e1 (also called vector norm error for simplicity) (the first evaluation function).

[0073] The electromotive force estimation calculation unit 34 is based on the candidate vector G k To calculate the estimated electromotive force (EMF) generated in the magnetic field detection element 23.

[0074] The standardized voltage error calculation unit 35 calculates the error between the estimated electromotive force and the measured voltage obtained from the detection signal, i.e., the electromotive force error. Furthermore, the standardized voltage error calculation unit 35 standardizes the electromotive force error based on the measured voltage and calculates the standardized electromotive force error e2 (second evaluation function).

[0075] When the standardized electromotive force error e2 is within the second range, the estimated coordinate acquisition unit 36 ​​acquires the current maximum likelihood coordinates as the estimated coordinates of the magnetic field generating element 22.

[0076] On the one hand, refer toFigure 6 while following Figures 7 to 9 The flowchart for Figure 5 The functions of each part of the control unit 26 shown will be explained in more detail.

[0077] Figure 6 This diagram illustrates an example in the first embodiment of selecting one of the grid point coordinates p1 to p26 within a specified spatial range centered on the search center coordinate p0 as the candidate coordinate. Figure 7 This is a flowchart illustrating a portion of the transmitting coil coordinate estimation process in the first embodiment. Figure 8 This is a flowchart illustrating stage 1 of the process in the first embodiment, which is part of the transmission coil coordinate estimation process. Figure 9 This is a flowchart illustrating stage 2 of the process in the first embodiment, which is part of the transmission coil coordinate estimation process.

[0078] It is mainly operated by the processor 26a according to the computer program stored in the memory 26b. Figure 5 Each of the functional parts shown will perform an action to... Figures 7 to 9 The transmitting coil coordinate estimation process is shown.

[0079] In the main processing unit (not shown), processor 26a executes the following whenever it receives a detection signal from magnetic field detection unit 25: Figure 7 The processing shown.

[0080] When it begins Figure 7 During the processing shown, processor 26a initializes each parameter (step S1).

[0081] exist Figures 7 to 9 The coordinate estimation process for the transmitting coil shown mainly involves two stages: Stage 1 and Stage 2. In Stage 1, candidate vector G representing the direction of the magnetic field generating element 22 (hereinafter appropriately referred to as transmitting coil C) is estimated. k In this second stage of processing, the candidate vector G estimated in the first stage is used... k To estimate the position of the transmitting coil C.

[0082] In the initialization of step S1, processor 26a adds the value ST1, representing stage 1, to the parameter ST, which represents the current stage. Processor 26a also increments counter j by 0, which increments the counter by the coordinates of grid points within a specified spatial range (refer to...). Figure 6 The processor 26a counts the number of times the search center coordinates p0 have been selected (as described later), and increments the counter i by 0. The counter i represents the number of times the grid point coordinates centered at search center coordinates p0 have been selected (i.e., the grid point coordinates centered at search center coordinates p0 are set, as described later). Figure 6counting the number of times of the occurrence of the condition (e1 > e1max). The processor 26a adds a maximum value e1max of e1 that is desirable to the candidate vector norm error e1 1max The processor 26a adds a maximum value e2max of e2 that is desirable to the standardization electromotive force error e2 2max .

[0083] Then, the processor 26a detects the electromotive force (measured voltage) generated in the magnetic field detection element 23 from the detection signal transmitted from the magnetic field detection section 25 (step S2).

[0084] The information of the range (the entire range) of the space in which the position detection is possible by the magnetic field detection element 23 is stored in the memory 26b in advance. Specifically, the memory 26b stores, for example, the maximum value and the minimum value of each of the x, y, z coordinates of the entire range.

[0085] The processor 26a selects any of the coordinates of the three-dimensional coordinates of the points included in the entire range stored in the memory 26b as the search center coordinate p0 (step S3).

[0086] The processor 26a sets a plurality of grid point coordinates in the prescribed spatial range centered on the search center coordinate p0. In setting the grid point coordinates, the processor 26a sets a grid point interval and rotates the grid point coordinate system (step S4).

[0087] In the case where the processing of step S4 is performed for the first time after starting the processing of Figure 7 In the case where the processing of step S4 is performed for the first time after starting the processing of

[0088] Figure 6 is a diagram showing an example of the grid point coordinates set by the processor 26a. In the example shown in Figure 6 In the example shown in FIG. 8, an example in which 3 x 3 x 3 grid point coordinates are set in the x' axis direction, the y' axis direction, and the z' axis direction in the x'y'z' coordinate system that is a local three-dimensional orthogonal coordinate system, centered on the search center coordinate p0 is shown.

[0089] Further, the grid point coordinates are not limited to 3 x 3 x 3, and can be, for example, 5 x 5 x 5, or the like, but in order to quickly obtain the estimated coordinates of the magnetic field generating element 22 with a small amount of calculation, it is preferable that the number of grid point coordinates not be increased.

[0090] The grid point coordinates pi to p26 and the search center coordinate po are arranged together in a total of 27 grid point coordinates within a prescribed spatial range. Further, the x'y'z' coordinate system as the local coordinate system and the xyz coordinate system as the global coordinate system are associated using a rotation matrix of a three-dimensional space.

[0091] The processor 26a (candidate coordinate selection section 31) selects, for example, any of the grid point coordinates shown in FIG. 6 as a candidate coordinate (step S5). In the case where the process of step S5 is performed for the first time after starting the process of step S4, the search center coordinate po can be selected as the candidate coordinate, or any of the grid point coordinates pi to p26 can be selected as the candidate coordinate. Further, in the case where the process of step S5 is performed for the second time or later, the search center coordinate po has already been selected as the candidate coordinate, and therefore any of the grid point coordinates pi to p26 is selected as the candidate coordinate. Figure 6 Figure 7

[0092] The processor 26a (candidate vector operation section 32) calculates a candidate vector G k from the selected candidate coordinate (step S6).

[0093] The above describes an example in which there are four groups of reception coils up to the reception coil groups 23gl to 23g4, but the following describes a more general case in which there are l (l is an integer of 2 or more) groups of reception coils. Further, k (k = 1, 2,..., l) represents an arbitrary group number from 1 to l. In the example shown in FIG. 7 and FIG. 8, l = 4. Figure 2 Figure 3

[0094] The direction vector g (unit vector) of the transmission coil C, the matrix B k , and the constant ξ are used to express, in principle, the electromotive force vector v k made from the electromotive force generated in the magnetic field detection element 23 of the group k due to the magnetic field MF generated from the transmission coil C by (Formula 1).

[0095] (Formula 1)

[0096]

[0097] Here, the electromotive force v xk ​​​​, the electromotive force v generated in the y-direction receiving coil SCyk of the group k yk , and the electromotive force v generated in the z-direction receiving coil SCzk of the group k zk The electromotive force vector v is represented by (Formula 2) k .

[0098] (Formula 2)

[0099]

[0100] The x-direction component g x , the y-direction component g y , and the z-direction component g z The direction vector g of the transmitting coil C is represented by (Formula 3)

[0101] (Formula 3)

[0102]

[0103] In addition, the value of the constant ξ is determined by the gain of the entire transmitting-receiving system including the transmitting system (the magnetic field generating element 22 and the drive signal transmitting section 24, etc.) that transmits the magnetic field MF and the receiving system (the magnetic field detecting element 23 and the magnetic field detecting section 25, etc.) that receives the magnetic field MF transmitted from the transmitting system. The value of the constant ξ is determined, for example, in accordance with the characteristics of the transmitting coil C and the characteristics of the receiving coil, etc. The constant ξ is stored in advance in the memory 26b.

[0104] The matrix A k and the matrix R k The matrix B k is represented by (Formula 4).

[0105] (Formula 4)

[0106]

[0107] The matrix R k in (Formula 4) is represented by (Formula 5).

[0108] (Formula 5)

[0109]

[0110] The matrix components r xk , r yk , and r zk in (Formula 5) are represented by (Formula 6).

[0111] (Formula 6)

[0112]

[0113] The xRk y Rk z Rk Let x, y, and x-coordinates of the receiving coil SCk of group k be represented respectively. T y T z T Let x, y, and x represent the x, y, and x coordinates of the transmitting coil C, respectively. Therefore, r xk r yk r zk These represent the x-direction distance, y-direction distance, and z-direction distance between the receiving coil SCk and the transmitting coil C, respectively.

[0114] In addition, matrix A in (Equation 4) k This is expressed by (Equation 7).

[0115] (Equation 7)

[0116]

[0117] The matrix components of (Equation 7) are represented by (Equation 8).

[0118] (Equation 8)

[0119]

[0120] In other words, matrix A is determined based on the xyz coordinates of the receiving coil SCk and the xyz coordinates of the transmitting coil C. k .

[0121] Therefore, using matrix A k And matrix R k Matrix B calculated using Equation 4 k It is calculated based on the xyz coordinates (coordinates of the magnetic field detection element 23) and candidate coordinates (candidate coordinates of the magnetic field generating element 22) of the receiving coil SCk of group k (xyz coordinates of each transmitting coil C).

[0122] In the above principle, candidate coordinates are used as the coordinates of transmitting coil C to calculate matrix B. k The measured value is used as the electromotive force vector v k Thus, the candidate vector G expressed by (Equation 9) is obtained. k Candidate vector G k For candidate vector G k It is obtained by multiplying the direction vector g (which represents a candidate direction of the transmitting coil C) by a constant ξ.

[0123] (Equation 9)

[0124]

[0125] Next, the processor 26a determines whether the value of the parameter ST is ST1, that is, whether the current stage is stage 1 (step S7).

[0126] In this case, when the value of the parameter ST is ST1, the stage 1 processing of the Figure 8 is entered (step S8).

[0127] When the stage 1 processing of the Figure 8 is entered, the processor 26a (candidate vector norm error operation section 33) calculates the candidate vector norm error el as represented by (Formula 10) on the basis of the candidate vector G k (step Sll). Further, in (Formula 10) (as well as (Formula 11) and (Formula 12) described later), the two lines surrounding the vector represent the norm (specifically, the length of the vector (Euclidean norm)).

[0128] (Formula 10)

[0129]

[0130] The processor 26a compares the newly calculated candidate vector norm error el with the minimum value of the candidate vector norm errors el calculated in the past each time the new candidate vector norm error el is calculated (step S12).

[0131] That is, the processor 26a stores the minimum value of the candidate vector norm errors el calculated after the processing shown in Figure 7 is started, for example, in the memory 26b in advance. Then, the processor 26a compares the minimum value of the candidate vector norm errors el stored in the memory 26b with the newly calculated candidate vector norm error el.

[0132] In this case, when the newly calculated candidate vector norm error el is smaller than the minimum value of the candidate vector norm errors el calculated in the past, the processor 26a updates the maximum likelihood coordinates (coordinates estimated as the closest to the true values (the true coordinates of the magnetic field generating element 22) at the current time point) to the current candidate coordinates (step S13). The memory 26b stores the maximum likelihood coordinates.

[0133] The processor 26a determines whether the candidate vector norm error el is smaller than a prescribed threshold value e 1th (the first range) (step S14). In this case, the memory 26b stores the prescribed threshold value e 1th . The processor 26a reads out the prescribed threshold value e 1th from the memory 26b to perform the determination of step S14.

[0134] Furthermore, as shown in Equation 10, the candidate vector norm error e1 takes values ​​greater than or equal to 0. Therefore, the first range is greater than or equal to 0 and less than e1. 1th The range.

[0135] Here, the candidate vector norm error e1 is not less than the specified threshold e 1th In the case where the counter j has reached the specified value p (step S15), the processor 26a determines whether the counter j has reached the specified value p. The specified value p is the total number of candidate coordinates within a specified spatial range centered on the search center coordinate p0.

[0136] For example, in Figure 6 In the example shown, except at the beginning Figure 7 In the process shown, except for the case where the search center coordinates p0 were initially selected, the grid point coordinates p1 to p26 became candidate coordinates (as mentioned above, since the search center coordinates p0 selected after the second time became the coordinates of the candidate vector norm error e1 (or the standardized electromotive force error e2 described later)). Therefore, in step S15, the processor 26a determines whether to end the process of setting all grid point coordinates p1 to p26 as candidate coordinates based on whether the counter j has reached the predetermined value p=26.

[0137] If counter j does not reach the predetermined value p in step S15, processor 26a increments counter j (step S16) and proceeds to step S15. Figure 7 The processing in step S5. In step S5, processor 26a selects the unselected grid point coordinates from grid point coordinates p1 to p26 as new candidate coordinates and performs the above processing. Therefore, processor 26a selects new candidate coordinates when the candidate vector norm error e1 is not within the first range.

[0138] Furthermore, if counter j reaches a predetermined value p in step S15, processor 26a determines whether counter i has reached a predetermined value m1 (step S15A). Here, the predetermined value m1 is greater than 0 and less than the predetermined value m described later (see reference). Figure 9 The value of step S28). The memory 26b stores the specified value m1. The processor 26a reads the specified value m1 from the memory 26b to perform the determination in step S15A.

[0139] Here, when the counter i reaches the specified value m1, the processor 26a proceeds to the processing of step S18, which will be described later.

[0140] If counter i does not reach the specified value m1 in step S15A, processor 26a increments counter i and resets counter j to 0 (step S17), then proceeds to step S18. Figure 7The processing in step S3. In step S3, the processor 26a selects the three-dimensional coordinates of other points within the entire range stored in the memory 26b as the search center coordinates p0, and performs the above processing.

[0141] That is, processor 26a selects a new search center coordinate p0 even though it has selected all the grid point coordinates p1 to p26 as candidate coordinates, but the candidate vector norm error e1 is not within the first range.

[0142] On the other hand, in step S14, the candidate vector norm error e1 is less than the specified threshold e 1th In the case of this, processor 26a adds the value ST2, representing stage 2, to the parameter ST, which represents the current stage (step S18).

[0143] Then, processor 26a updates the search center coordinates p0 to the current maximum likelihood coordinates (step S19), and proceeds to... Figure 7 The processing of step S4 continues until step S6.

[0144] Therefore, in step S14, if the candidate vector norm error e1 is within the first range, the processor 26a selects the current maximum likelihood coordinate as the new search center coordinate p0 in step S19, and selects one of the grid point coordinates p1 to p26 within the specified spatial range centered on the search center coordinate p0 as the candidate coordinate in step S5.

[0145] Since the value ST2 was added to parameter ST in step S18, in the subsequent step S7, processor 26a determines that the value of parameter ST is not ST1, and proceeds to... Figure 9 Phase 2 processing (step S9).

[0146] When entering Figure 9 During stage 2 processing, processor 26a (estimation electromotive force calculation unit 34) is based on matrix B. k and candidate vector G k+1 To calculate and estimate the electromotive force B k G k+1 (Refer to the second term in the norm of the molecule within the sigma on the right side of (Equation 11)) (Step S21).

[0147] Furthermore, the processor 26a (normalized voltage error calculation unit 35) calculates and estimates the electromotive force B. k G k+1 The electromotive force vector v obtained from the detected signal k The error in (measuring voltage) is the electromotive force error (refer to the norm of the molecule within the sigma on the right side of (Equation 11), based on the electromotive force vector v kThe electromotive force error is standardized by measuring the voltage, thereby calculating the standardized electromotive force error e2 expressed by (Equation 11) (step S22).

[0148] (Equation 11)

[0149]

[0150] Furthermore, on the right-hand side of (Equation 11), sigma is the sum of k=1~l, but the candidate vector G k+1 The subscript (k+1) takes the value "1" when k=l.

[0151] Each time the processor 26a calculates a new standardized electromotive force error e2, it compares it with the minimum value of the previously calculated standardized electromotive force error e2 (step S23).

[0152] That is, processor 26a will begin... Figure 7 The minimum value of the standardized electromotive force error e2 calculated after the processing shown is stored, for example, in memory 26b. Then, the minimum value of the standardized electromotive force error e2 stored in memory 26b is compared with the newly calculated standardized electromotive force error e2.

[0153] Here, if the newly calculated normalized electromotive force error e2 is less than the minimum value of the previously calculated normalized electromotive force error e2, the processor 26a updates the maximum likelihood coordinates to the current candidate coordinates (step S24). The memory 26b stores the maximum likelihood coordinates.

[0154] Processor 26a determines whether the standardized electromotive force error e2 is less than the specified threshold e 2th (Second range) (Step S25). Here, memory 26b stores the specified threshold e. 2th Processor 26a reads the specified threshold e from memory 26b. 2th Then proceed to the determination in step S25.

[0155] Furthermore, as shown in Equation 11, the standardized electromotive force error e2 takes values ​​greater than or equal to 0. Therefore, the second range is greater than or equal to 0 and less than e. 2th The range.

[0156] Here, the standardized electromotive force error e2 is not less than the specified threshold e 2th In the case of this, processor 26a determines whether counter j has reached the specified value p (step S26).

[0157] If counter j does not reach the specified value p in step S26, processor 26a increments counter j (step S27) and proceeds to step S28. Figure 7the process of step S5. In step S5, the processor 26a selects a grid point coordinate that has not been selected among the grid point coordinates pi to p26 as a new candidate coordinate, and performs the above-described process. Thus, the processor 26a selects a new candidate coordinate in a case where the normalized electromotive force error e2 is not in the second range.

[0158] In addition, in a case where the counter j reaches the prescribed value p in step S26, the processor 26a determines whether the counter i reaches the prescribed value m (step S28). Here, the prescribed value m is stored in the memory 26b. The processor 26a reads out the prescribed value m from the memory 26b to perform the determination of step S28.

[0159] In a case where the counter i does not reach the prescribed value m in step S28, the processor 26a increments the counter i, and resets the counter j to 0 (step S29).

[0160] Further, the processor 26a updates the search center coordinate po to the current maximum likelihood coordinate (step S30), and proceeds to the process of step S4 of FIG. 4, and further proceeds to the process of step S5. Figure 7

[0161] Thus, the processor 26a selects the current maximum likelihood coordinate as a new search center coordinate po in a case where the normalized electromotive force error e2 is not in the second range despite that all of the plurality of grid point coordinates pi to p26 are selected as candidate coordinates, and selects one grid point coordinate among the plurality of grid point coordinates pi to p26 that is within the prescribed spatial range centered on the search center coordinate po as a candidate coordinate.

[0162] Further, as described above, the processor 26a narrows the prescribed spatial range to shorten the grid point interval in a case where the new search center coordinate po is selected.

[0163] On the other hand, in a case where the normalized electromotive force error e2 is smaller than the prescribed threshold value e 2th in step S25, or in a case where the counter i reaches the prescribed value m in step S28, the processor 26a (estimated coordinate acquisition unit 36) acquires the current maximum likelihood coordinate as an estimated coordinate (step S31).

[0164] That is, the processor 26a acquires the current maximum likelihood coordinate as an estimated coordinate of the magnetic field generating element 22 in a case where the normalized electromotive force error e2 is in the second range.

[0165] In addition, in the present embodiment, if the normalized electromotive force error e2 is not smaller than the prescribed threshold value e 2th but the counter i reaches the prescribed value m, the processor 26a acquires the current maximum likelihood coordinate as an estimated coordinate.​

[0166] In addition, a direction vector g indicating the direction of the magnetic field generating element 22 (the direction of the transmission coil C) in which the estimated coordinates are acquired is expressed as a unit vector after normalizing the vector sum of the candidate vectors G k of the group of the l reception coils SCk by the following (Formula 12).

[0167] (Formula 12)

[0168]

[0169] Here, the estimated coordinates acquired in step S31 are substituted into the x, y, and z coordinates x Rk , y Rk , and z Rk of the reception coil SCk of the group k, and the candidate vector G k used in (Formula 12) is recalculated by (Formula 4) to (Formula 9).

[0170] Thus, the direction vector g (estimated vector) expressed by (Formula 12) becomes a maximum likelihood vector corresponding to the maximum likelihood coordinates that are the basis of the estimated coordinates.

[0171] If the processing of step S31 is performed, the process returns to the main process, which is not illustrated.

[0172] According to the first embodiment, the candidate vector G k is approximated to the maximum likelihood vector in phase 1, and when the candidate vector norm error el becomes smaller than a prescribed threshold value e 1th , the process of approximating the candidate coordinates to the maximum likelihood coordinates is performed in phase 2. Thus, the candidate vector G k does not greatly differ from the true value, and it is possible to avoid the estimated coordinates from falling into a local minimum value without being approximated to the true value.

[0173] For example, at a near point, the candidate vector G k is likely to greatly differ from the true value. Here, the near point is a point closest to the magnetic field detecting element 23 within the range (the entire range) of the space in which position detection is possible by the magnetic field detecting element 23. In contrast, in the present embodiment, as indicated by (Formula 10), the candidate vector norm error el based on the norm of the vector obtained by dividing the candidate vector G k by a constant ξ (i.e., the norm of the approximate value 1 of the norm of the unit vector) is used to evaluate the likelihood of the candidate vector G k . Thus, in the present embodiment, it is possible to accurately determine the candidate vector norm error el and approximate the candidate vector G k to the true value even at the near point.

[0174] In addition, at the close point, the electromotive force becomes large, so even if there is a small coordinate error, the voltage error of the estimated electromotive force and the measured voltage is likely to become large. In contrast, in the present embodiment, as shown in (Formula 11), the electromotive force error is normalized based on the measured voltage, and it is determined whether the normalized electromotive force error e2 is smaller than a prescribed threshold value e 2th Thus, in the present embodiment, even at the close point, the error rate of the estimated electromotive force and the measured voltage can be accurately determined, and the estimated coordinates can be brought close to the true values.

[0175] In Figure 9 Stage 2 shown in FIG. 6, even if the process returns to Step S4 or Step S5 of Figure 7 , the process of Step S3 of Figure 7 is not returned to. That is, in Stage 2, the other point included in the entire range stored in the memory 26b is not selected as the search center coordinates p0. In this way, in Stage 2, only the mesh point coordinates p1 to p26 for which the maximum likelihood coordinates obtained in Stage 1 are set as the search center coordinates p0 are searched, so the estimated coordinates can be quickly obtained with a small number of search points (i.e., with a small amount of calculation).

[0176] In this way, the relative position and direction of the magnetic field generating element 22 and the magnetic field detecting element 23 in a large range including the close point of the magnetic field detecting element 23 can be quickly estimated with a small amount of calculation.

[0177] Further, when the search center coordinates p0 and the mesh point coordinates are reset, the mesh point interval is further shortened, so the estimated coordinates can be accurately obtained.

[0178] In addition, the magnetic field generating element 22 is disposed inside the endoscope 3, and the magnetic field detecting element 23 is disposed outside the endoscope 3 as the antenna 28. Therefore, the degree of freedom of the arrangement of the reception coil groups 23gl to 23g4 in the magnetic field detecting element 23 is high. Thus, as shown in FIG. 7, the reception coil groups 23gl to 23g4 can be arranged, for example, so as to isolate noise sources, and the accuracy of the detection signal can be improved. Figure 2

[0179] [Second Embodiment]

[0180] Figure 10 is a diagram showing a structure example in which the magnetic field detecting element 23 is disposed in the endoscope 3, and the magnetic field generating element 22 is disposed outside the endoscope 3 as the antenna 28 in the second embodiment of the present application. In the second embodiment, the same parts as those of the first embodiment are denoted by the same reference numerals, and appropriate description is omitted. In the second embodiment, points different from those of the first embodiment are mainly described.

[0181] ​In the first embodiment, a magnetic field generating element 22 is disposed inside the endoscope 3, and a magnetic field detecting element 23 is disposed outside the endoscope 3 via an antenna 28 (in...). Figure 2 In the example, it is a receiving antenna). In contrast, in the second embodiment, the magnetic field generating element 22 is disposed outside the endoscope 3 on the antenna 28 (in Figure 10 In the example, the transmitting antenna is used, and the magnetic field detection element 23 is placed inside the endoscope 3.

[0182] Thus, the configuration of the magnetic field generating element 22 (specifically, transmitting coils C1 to Cn) and the magnetic field detecting element 23 (specifically, receiving coil group 23g1 to 23g4) can also be the opposite of the structure shown in the first embodiment.

[0183] According to the second embodiment, it achieves roughly the same effect as the first embodiment described above.

[0184] Furthermore, generally speaking, the current value of the detection signal sent by the magnetic field detection element 23 to detect the magnetic field MF is smaller than the current value of the drive signal sent by the drive signal transmitting unit 24 to the magnetic field generating element 22. Therefore, according to the second embodiment, compared with the first embodiment, the heat generated by the coil inside the endoscope 3 can be reduced, and the temperature rise of the endoscope 3 can be suppressed. As a result, for example, the generation of thermal noise of the imaging element 16 caused by the temperature rise can be reduced. In addition, the burden on the patient caused by the temperature rise of the endoscope 3 can also be reduced.

[0185] [Third Implementation Method]

[0186] Figure 11 This diagram illustrates a structural example in the third embodiment of the present invention where the signal detected by the receiving coil SC of the magnetic field detection element 23 is amplified in a manner that allows for changing the amplification rate, converted into a digital signal, and transmitted to the magnetic field detection unit 25. In the third embodiment, the same reference numerals are used for parts that are the same as in the first and second embodiments, and descriptions are omitted where appropriate. In the third embodiment, the differences from the first and second embodiments will be mainly explained.

[0187] The position detection system 2 also includes first to nth amplifiers 38-1 to 38-n that amplify and transmit the signal generated by the magnetic field MF detected by the magnetic field detection element 23.

[0188] Multiple (n) amplifiers 38-1, 38-2, ..., 38-n are connected in parallel across the two ends of the receiving coil SC. The n amplifiers 38-1, 38-2, ..., 38-n detect the electromotive force across the two ends of the receiving coil SC and amplify it through their respective gains.

[0189] If the gain of the first amplifier 38-1 is set to G1, the gain of the second amplifier 38-2 is set to G2,..., and the gain of the nth amplifier 38-n is set to Gn, the amplifiers are configured, for example, in such a manner that G1 < G2 <... < Gn is satisfied.

[0190] The first amplifier 38-1 is connected to the ADC 39-1. The ADC 39-1 transmits a digital detection signal containing information of the voltage V1 amplified by the first amplifier 38-1 with the gain G1 to the magnetic field detection section 25.

[0191] The second amplifier 38-2 is connected to the ADC 39-2. The ADC 39-2 transmits a digital detection signal containing information of the voltage V2 amplified by the second amplifier 38-2 with the gain G2 to the magnetic field detection section 25.

[0192] The nth amplifier 38-n is connected to the ADC 39-n in the same manner as the other amplifiers. The ADC 39-n transmits a digital detection signal containing information of the voltage Vn amplified by the nth amplifier 38-n with the gain Gn to the magnetic field detection section 25.

[0193] The magnetic field detection section 25 receives detection signals containing information of the voltages V1 to Vn from the n ADCs 39-1 to 39-n, respectively. As described above, the gains have the relationship of G1 < G2 <... < Gn, and therefore, in general, the voltages have the relationship of V1 < V2 <... < Vn.

[0194] The magnetic field detection section 25 uses the threshold voltages V1 th to Vn th with respect to the voltages V1 to Vn, respectively. th th The threshold voltages V1 th to Vn th may be installed as hardware in the magnetic field detection section 25, or can be stored in a not-shown memory in the magnetic field detection section 25 or in the memory 26b in the control section 26.

[0195] The magnetic field detection section 25 first compares the voltage V1 with the threshold voltage V1 th , and in the case of V1 > V1 th , the electromotive force V is calculated by V = V1 / G1.

[0196] In addition, in the case of V1 ≤ V1 th , the magnetic field detection section 25 compares the voltage V2 with the threshold voltage V2 th , and in the case of V2 > V2 th , the electromotive force V is calculated by V = V2 / G2.

[0197] In the case of V2 ≤ V2 thIn the case where the magnetic field detection unit 25 performs the same processing on voltages after voltage V3, until V(n-1) ≤ V(n-1). th In this case, the voltage Vn is compared with the threshold voltage Vn th Comparison, in Vn>Vn th When V is used, the electromotive force V is calculated using V=Vn / Gn.

[0198] Furthermore, in Vn≤Vn th In some cases, the magnetic field detection unit 25 may also send an error signal to the control unit 26. In this case, the control unit 26 is set to stop execution because the magnetic field MF has not been detected by the magnetic field detection unit 25. Figure 7 The process shown continues until a detection signal is received from the magnetic field detection unit 25.

[0199] Or, even if Vn≤Vn th In this case, the magnetic field detection unit 25 can also calculate the electromotive force V by V=Vn / Gn.

[0200] As mentioned above, the reason for confirming the voltage in the order of V1→V2→…→Vn is that if the amplification is too large relative to the signal size, the voltage value will exceed the upper limit of the detectable range of the ADC, and the voltage cannot be detected correctly.

[0201] Thus, the first to nth amplifiers 38-1 to 38-n function as amplification units that can change the amplification rate according to the voltage of the signal.

[0202] In addition, Figure 11 The illustration shows an example of multiple amplifiers 38 with different gains and multiple ADCs 39 connected to the multiple amplifiers 38 respectively, but is not limited to this structure. For example, it is also possible to provide an amplifier 38 with variable gain and an ADC 39 connected to the amplifier 38, wherein the gain of the amplifier 38 is changed according to the voltage of the signal transmitted from the receiving coil SC.

[0203] Alternatively, the current value of the drive signal sent by the drive signal transmitting unit 24 to the magnetic field generating element 22 can be changed (and the strength of the magnetic field MF generated by the magnetic field generating element 22 can be changed) so that the voltage of the signal sent from the receiving coil SC converges within a certain voltage range.

[0204] According to the third embodiment, it achieves substantially the same effects as the first and second embodiments described above. The third embodiment also has the following effects.

[0205] exist Figure 4In the illustrated ADC 39, there are constraints on the voltage detectable range (dynamic range) and resolution. Therefore, even if the algorithm is improved, sometimes the position of the magnetic field generating element 22 located in a wide range from the near point to the far point cannot be detected. Here, the far point is a point farthest from the magnetic field detection element 23 in the spatial range (entire range) in which the position detection by the magnetic field detection element 23 is possible.

[0206] On the contrary, according to the third embodiment, it is possible to change the amplification of the amplifier according to the voltage of the signal generated by the magnetic field detection element 23 detecting the magnetic field MF, and therefore the voltage range that can be detected is expanded. Alternatively, it is possible to change the current value of the drive signal so that the voltage of the signal generated by detecting the magnetic field MF converges within a certain voltage range, and therefore the magnetic field MF can be detected at all times. Thus, it is possible to detect the position of the magnetic field generating element 22 located in a wide range from the near point to the far point with high precision.

[0207] [Fourth Embodiment]

[0208] Figures 12 to 14 Fig. 14 is a view showing a fourth embodiment of the present application. In the fourth embodiment, the same parts as those of the first to third embodiments are denoted by the same reference numerals and appropriate description will be omitted. In the fourth embodiment, points different from those of the first to third embodiments will be mainly described.

[0209] Figure 12 Fig. 15 is a view showing the structure of the position detection system 2 in the fourth embodiment.

[0210] Figure 12 The position detection device 21 shown in Fig. 14 has, in addition to the structure shown in Fig. 1, Figure 5 The position detection device 21 shown in Fig. 14 has, in addition to the structure shown in Fig. 1,

[0211] The estimation coordinate using section 41 receives the estimation coordinates transmitted from the estimation coordinate acquisition section 36 (and also the estimation vectors as needed, the same hereinafter). The estimation coordinate using section 41 generates, for example, a shape detection image showing the shape of the insertion section 11 based on the received estimation coordinates of the transmission coils Cl to Cn. In addition, the estimation coordinate using section 41 can generate insertion assistance information based on the received estimation coordinates.

[0212] The shape detection image, the insertion assistance information, and the like generated by the estimation coordinate using section 41 are transmitted to the video processor 5 connected to the position detection device 21 and displayed on the monitor 6 together with the endoscope image.

[0213] Further, although not shown, the position detection system 2 of the first to third embodiments described above can also be provided with the estimation coordinate use section 41.

[0214] Figure 13 is a flowchart showing the stage 1 processing that is part of the transmission coil coordinate estimation processing in the fourth embodiment.

[0215] Figure 13 The stage 1 processing shown in Figure 8 is basically the same as the stage 1 processing shown in , but after the processing of step S17 is performed, the processor 26a further determines whether the counter i has reached a prescribed value m (step S41).

[0216] Figure 7 Here, in the case where the counter i has not reached the prescribed value m, the processor 26a proceeds to the processing of step S3 of

[0217] On the other hand, in the case where the counter i has reached the prescribed value m in step S41, the processor 26a proceeds to the processing of step S42 of Figure 14 described later.

[0218] Figure 14 is a flowchart showing the stage 2 processing that is part of the transmission coil coordinate estimation processing in the fourth embodiment.

[0219] Figure 14 The stage 2 processing shown in Figure 9 is basically the same as the stage 2 processing shown in , but in the case where the counter i has reached the prescribed value m in step S28, the processor 26a does not update the estimation coordinate (step S42). Also, as described above, in the case where the counter i has reached the prescribed value m in step S41 of the stage 1 processing, the processor 26a also does not update the estimation coordinate by step S42.

[0220] In this way, the processor 26a counts the number of times the search center coordinate p0 is selected using the counter i, and does not acquire the estimation coordinate of the magnetic field generating element 22 in the case where, despite the count value becoming the prescribed value m, the candidate vector norm error el is not within the first range or the normalized electromotive force error e2 is not within the second range.

[0221] Thus, the estimation coordinate is acquired (updated) by the processing of step S31 in the case where, after the transmission coil coordinate estimation processing of Figure 7 is called in the main processing, the candidate vector norm error el is less than the prescribed threshold value e 1th in step S14 of the stage 1 processing of Figure 13 , and the normalized electromotive force error e2 is less than the prescribed threshold value e 2th in step S25 of the stage 2 processing of Figure 14 ..

[0222] While the endoscope 3 is being moved, e1 may be momentarily unavailable. <e 1th And e2 <e 2th This can lead to a state where the position and orientation are difficult to estimate. Furthermore, situations involving electromagnetic noise, or individual deviations in the coils or constants ξ of the transmitting and receiving magnetic field MF in the transmitting and receiving system, can also result in a state where the position and orientation are difficult to estimate.

[0223] Therefore, in this embodiment, even if the estimated coordinates are searched a predetermined number of times (until counter i reaches a predetermined value m), e1 cannot be satisfied. <e 1th And e2 <e 2th In this case, the estimated coordinates are not updated. Instead, the coordinates used in the last call to the main processing function are retained. Figure 7 The estimated coordinates obtained during the coordinate estimation process of the transmitting coil.

[0224] According to the fourth embodiment, it achieves roughly the same effect as the first to third embodiments described above.

[0225] Furthermore, according to the fourth embodiment, if the estimated coordinates that are estimated to be correct cannot be obtained, the estimated coordinates are not updated, thus preventing the estimated coordinates usage unit 41 from generating incorrect shape detection images or incorrect insertion auxiliary information.

[0226] [Fifth Implementation]

[0227] Reference Figure 1 The fifth embodiment of the present invention will now be described. In the fifth embodiment, the same reference numerals are used to refer to the same parts as in the first to fourth embodiments, and descriptions are omitted where appropriate. In the fifth embodiment, the differences from the first to fourth embodiments will be mainly described.

[0228] As described above, the value of the constant ξ used in calculating the candidate vector norm error e1 is determined by the overall gain of the transmitting and receiving systems, including the transmitting system that transmits the magnetic field MF and the receiving system that receives the magnetic field MF. Therefore, the value of the constant ξ may sometimes be deviated due to individual differences on the endoscope 3 side where the magnetic field generating element 22 (or magnetic field detection element 23) is installed, and the value of the constant ξ may sometimes be deviated due to individual differences on the position detection system 2 side where the magnetic field detection element 23 (or magnetic field generating element 22) is installed.

[0229] Therefore, the first correction value (individual adjustment value) for the constant ξ, which is used to correct the effect of individual deviation on the endoscope 3 side on the candidate vector norm error e1, is stored in the memory 17 provided in the endoscope 3.

[0230] And, a second correction value (individual adjustment value) for the constant ξ for correcting the influence of the individual deviation of the position detection system 2 side on the candidate vector norm error el is stored in, for example, the memory 26b provided to the position detection device 21.

[0231] The processor 26a of the position detection device 21 corrects the constant ξ based on the first correction value read out from the memory 17 of the endoscope 3 and the second correction value read out from the memory 26b of the position detection device 21, and calculates the candidate vector norm error el using the corrected constant ξ.

[0232] According to the fifth embodiment, substantially the same effects as the above first to fourth embodiments are exerted.

[0233] Further, according to the fifth embodiment, the individual adjustment values of the constant ξ to be used in the process of calculating the candidate vector norm error el are stored in the memory of the side that transmits the magnetic field MF and the memory of the side that receives the magnetic field MF, respectively. Therefore, even in the case of a large individual deviation, the estimated position can be acquired stably and with high precision.

[0234] And, in the case where different kinds of endoscopes 3 are combined in the position detection system 2 (or, in the case where endoscopes 3 are combined in different kinds of position detection systems 2), the estimated position can be acquired stably and with high precision.

[0235] Further, the above mainly describes the case where the present application is a control device and an endoscope system, but is not limited thereto. For example, the present application can also be a position detection method that performs the same processing as the control device. Further, the present application can also be a computer program for causing a computer to perform the same processing as the control device. And, the present application can also be a non-transitory computer-readable recording medium or the like that records the computer program.

[0236] Here, examples of the recording medium storing the computer program product are a floppy disk, a CD-ROM (Compact Disc Read only memory), a DVD (Digital Versatile Disc), a USB (Universal Serial Bus) memory, and the like, which are removable recording media, or an HDD (Hard Disk Drive), an SSD (Solid State Drive), and the like, which are recording media. The program stored in the recording medium is not limited to the entire computer program, but can be a part of the computer program. In addition, the entire or a part of the computer program can be distributed or provided via a communication network. The user installs the computer program from the recording medium to the computer, or downloads the computer program via the communication network and installs it to the computer, whereby the computer can read the computer program and execute the entire or a part of the action to execute the action of the control device described above.

[0237] Also, the present application is not limited to the above-described embodiments. The present application can be embodied by being modified in the range not departing from the gist of the present application in the implementation stage. In addition, the plurality of components disclosed in the above-described embodiments can be appropriately combined to form various applications. For example, several components can be deleted from all the components disclosed in the embodiments. Also, the components of different embodiments can be appropriately combined. Thus, various modifications and applications in the range not departing from the gist of the present application are self-evident.

Claims

1. A control device, characterized in that, Equipped with a processor The processor performs the following processing: Select candidate coordinates for the magnetic field generating element; Candidate vectors are calculated based on the coordinates of the magnetic field detection element, the candidate coordinates, and the detection signal sent by the magnetic field detection element after detecting the magnetic field generated by the magnetic field generating element. The vector norm error is calculated based on the candidate vectors; If the calculated vector norm error is less than the minimum value of the previously calculated vector norm error, the maximum likelihood coordinates are updated to the current candidate coordinates; Determine whether the vector norm error is within the first range; as well as If the vector norm error is not within the first range, a new candidate coordinate is selected.

2. The control device according to claim 1, characterized in that, The processor selects one grid point coordinate from a set of grid point coordinates within a specified spatial range centered on the search center coordinates as the candidate coordinates.

3. The control device according to claim 2, characterized in that, The processor selects new search center coordinates even when all of the multiple grid point coordinates are selected as candidate coordinates, but the vector norm error is not within the first range.

4. The control device according to claim 2, characterized in that, The processor performs the following processing when the vector norm error is within the first range: Select the current maximum likelihood coordinates as the new search center coordinates; as well as Select one of the grid point coordinates within the specified spatial range centered on the search center coordinates as the candidate coordinates.

5. The control device according to claim 4, characterized in that, When the processor selects the new search center coordinates, it narrows the specified spatial range and shortens the grid point interval.

6. The control device according to claim 4, characterized in that, The processor performs the following processing when the vector norm error is within the first range: The standardized electromotive force error is calculated based on the candidate vectors. If the calculated standardized electromotive force error is less than the minimum value of the previously calculated standardized electromotive force error, the maximum likelihood coordinates are updated to the current candidate coordinates. Determine whether the standardized electromotive force error is within the second range; as well as If the standardized electromotive force error is not within the second range, a new candidate coordinate is selected.

7. The control device according to claim 6, characterized in that, The processor performs the following processing: The estimated electromotive force is calculated based on the candidate vectors; The error between the estimated electromotive force and the measured voltage obtained from the detection signal is calculated, i.e., the electromotive force error. as well as The electromotive force error is standardized based on the measured voltage to calculate the standardized electromotive force error.

8. The control device according to claim 6, characterized in that, The processor performs the following processing even when all the coordinates of the plurality of grid points are selected as candidate coordinates, but the standardized electromotive force error is not within the second range: Select the current maximum likelihood coordinates as the new search center coordinates; as well as Select one of the grid point coordinates within the specified spatial range centered on the search center coordinates as the candidate coordinates.

9. The control device according to claim 8, characterized in that, When the processor selects the new search center coordinates, it narrows the specified spatial range and shortens the grid point interval.

10. The control device according to claim 6, characterized in that, When the standardized electromotive force error is within the second range, the processor obtains the current maximum likelihood coordinates as the estimated coordinates of the magnetic field generating element.

11. The control device according to claim 8, characterized in that, The processor counts the number of times the search center coordinates are selected. If the count value becomes a predetermined value, but the vector norm error is not within the first range or the standardized electromotive force error is not within the second range, the estimated coordinates of the magnetic field generating element are not acquired.

12. An endoscope system, characterized in that, have: Endoscope; A magnetic field generating element that generates a magnetic field; A magnetic field detection element that detects the magnetic field and sends a detection signal; and A processor that processes the detection signal. The processor performs the following processing: Select candidate coordinates for the magnetic field generating element; Candidate vectors are calculated based on the coordinates of the magnetic field detection element, the candidate coordinates, and the detection signal; The vector norm error is calculated based on the candidate vectors; If the calculated vector norm error is less than the minimum value of the previously calculated vector norm error, the maximum likelihood coordinates are updated to the current candidate coordinates; Determine whether the vector norm error is within a first range; and If the vector norm error is not within the first range, a new candidate coordinate is selected.

13. The endoscope system according to claim 12, characterized in that, The endoscope system also includes an amplifier that amplifies and transmits the signal generated by the magnetic field detection element when it detects the magnetic field. The amplifier can change its amplification rate according to the voltage of the signal.

14. The endoscope system according to claim 12, characterized in that, The magnetic field generating element is disposed inside the endoscope. The magnetic field detection element is positioned outside the endoscope.

15. The endoscope system according to claim 12, characterized in that, The magnetic field generating element is disposed outside the endoscope. The magnetic field detection element is disposed inside the endoscope.

16. The endoscope system according to claim 12, characterized in that, The endoscope includes a memory that stores a first correction value for correcting the effect of individual deviations of the endoscope on the vector norm error.

17. The endoscope system according to claim 12, characterized in that, The magnetic field generating element, the magnetic field detecting element, and the processor are disposed in the position detection system. The position detection system includes a memory that stores a second correction value for correcting the effect of individual deviations of the position detection system on the vector norm error.

18. A position detection method, characterized in that, A magnetic field is generated by a magnetic field generating element. The magnetic field is detected by a magnetic field detection element, which then sends a detection signal. Select candidate coordinates for the magnetic field generating element. Candidate vectors are calculated based on the coordinates of the magnetic field detection element, the candidate coordinates, and the detection signal. The vector norm error is calculated based on the candidate vectors. If the calculated vector norm error is less than the minimum value of the previously calculated vector norm error, the maximum likelihood coordinates are updated to the current candidate coordinates. Determine whether the vector norm error is within the first range. If the vector norm error is not within the first range, a new candidate coordinate is selected.

19. The position detection method according to claim 18, characterized in that, Select one grid point coordinate from a set of grid point coordinates within a specified spatial range centered on the search center coordinates as the candidate coordinates.

20. The position detection method according to claim 19, characterized in that, If the vector norm error is not within the first range, even though all the coordinates of the plurality of grid points are selected as candidate coordinates, a new search center coordinate is selected.

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