Capsule type endoscope control method and system

Abstract

The invention discloses a capsule type endoscope control method and system.The method comprises the steps that in the process that an external magnet moves and drives an endoscope to move, whether an object exists within a first preset distance range of the outer end face of the external magnet or not is detected, and if the object exists within the first preset distance range of the outer end face of the external magnet, the capsule type endoscope is controlled; and if yes, controlling the external magnet to execute preset action. In the process that the external magnet moves and drives the endoscope to move, when the external magnet is close to the examinee, the external magnet is controlled to execute the preset action to prevent the external magnet from continuously moving and colliding with the examinee, so that the situation that the external magnet collides with the examinee can be reduced; and an operator is prevented from always keeping concentrated energy to prevent an external magnet from colliding with the examinee, so that the labor intensity of the operator can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of electrical technology, and in particular to a capsule endoscope control method and system. Background Art

[0002] One working mode of a capsule endoscope is that the subject takes the capsule endoscope orally. The capsule endoscope carries a magnet (hereinafter referred to as the "internal magnet"). The control system is provided with an external magnet. By moving the external magnet and relying on the magnetic effect between the external magnet and the internal magnet of the capsule endoscope, the capsule endoscope is controlled to perform movements such as translation, rotation, and tumbling in the subject's body cavity, thereby achieving a controllable examination of the subject, such as examination of the human stomach.

[0003] In order to prevent the mechanical equipment from touching the body of the subject during operation and causing harm to the subject, in the prior art, the operator needs to operate the handle to control the movement of the external magnet while observing the distance between the external magnet and the subject. The operator needs to concentrate all the time and carefully observe the movement of the external magnet to prevent the external magnet from colliding with the subject. Therefore, the operator is prone to fatigue and needs a lot of training to operate the equipment proficiently. There is also a risk of collision with the subject's body due to operator error. Summary of the invention

[0004] The object of the present invention is to provide a capsule endoscope control method and system, which can reduce the situation where an external magnet collides with a subject and can reduce the labor intensity of an operator.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A capsule endoscope control method, comprising:

[0007] When the external magnet moves and drives the endoscope to move, detecting whether there is an object within a first preset distance range of the outer end surface of the external magnet;

[0008] If there is an object within the first preset distance range of the outer end surface of the external magnet, the external magnet is controlled to perform a preset action.

[0009] Optionally, detecting whether there is an object within a first preset distance range of the outer end surface of the external magnet includes:

[0010] The distance from an object on one side of the outer end surface of the external magnet to the external magnet is measured to determine whether the distance is within the first preset distance range. If so, it is determined that there is an object within the first preset distance range of the outer end surface of the external magnet.

[0011] Optionally, detecting whether there is an object within a first preset distance range of the outer end surface of the external magnet includes:

[0012] A modulation signal is sent to one side of the outer end surface of the external magnet, and an echo signal of the modulation signal reflected by the object is received. The time elapsed from the sending of the modulation signal to the receiving of the echo signal is obtained according to the phase delay of the echo signal, and the distance from the object on the outer end surface of the external magnet to the external magnet is obtained according to the time length.

[0013] Optionally, a plurality of sensors are provided on the outer end surface of the external magnet, and the sensors are used to detect whether there is an object within a first preset distance range of the outer end surface of the external magnet;

[0014] If there is an object within the first preset distance range of the outer end surface of the external magnet, controlling the external magnet to perform a preset action includes:

[0015] If at least one of the sensors detects that there is an object within a first preset distance range of the outer end surface of the external magnet, the external magnet is controlled to perform a preset action.

[0016] Optionally, if there is an object within the first preset distance range of the outer end surface of the external magnet, controlling the external magnet to perform a preset action includes:

[0017] Output SC= S1 && S2 && S3…&& Sn. If the output SC is a low level, the external magnet is controlled to perform a preset action, wherein n sensors are arranged on the outer end surface of the external magnet, S1, S2, S3,…, Sn respectively represent the output of the first sensor, the output of the second sensor, the output of the third sensor,… and the output of the nth sensor, n is a positive integer greater than 1, and any of the sensors is used to output a low level when detecting that there is an object within a first preset distance range of the outer end surface of the external magnet, otherwise it outputs a high level.

[0018] Optionally, controlling the external magnet to perform a preset action includes:

[0019] The external magnet is controlled to stop moving, or the moving speed of the external magnet is controlled to decrease.

[0020] A capsule endoscope control system, comprising:

[0021] A sensor, disposed on an outer end surface of the external magnet, for detecting whether there is an object within a first preset distance range of the outer end surface of the external magnet during the movement of the external magnet and the movement of the endoscope;

[0022] A control device is connected to the sensor and is used to control the external magnet to perform a preset action if there is an object within the first preset distance range of the outer end surface of the external magnet.

[0023] Optionally, a plurality of the sensors are provided on the outer end surface of the external magnet, and the plurality of the sensors are evenly arranged.

[0024] Optionally, the control device includes a mechanical arm, at the end of which the external magnet is disposed, and the external magnet is driven to move by the mechanical arm.

[0025] Optionally, the sensor includes a transmitting part and a receiving part, the transmitting part is used to emit a modulated signal, and the receiving part is used to receive an echo signal reflected by the object when the modulated signal is reflected, so as to obtain the distance from the object on one side of the outer end surface of the external magnet to the external magnet based on the echo signal and the modulated signal.

[0026] It can be seen from the above technical solution that the capsule endoscope control method and system provided by the present invention include: in the process of the external magnet moving and driving the endoscope to move, detecting whether there is an object within the first preset distance range of the outer end face of the external magnet, and if there is an object within the first preset distance range of the outer end face of the external magnet, controlling the external magnet to perform a preset action. In the process of the external magnet moving and driving the endoscope to move, when the distance between the external magnet and the subject is relatively close and about to collide with the subject, the external magnet can be controlled to perform a preset action to avoid the external magnet from colliding with the subject, thereby reducing the situation where the external magnet collides with the subject, and avoiding the need for the operator to stay focused all the time to prevent the external magnet from colliding with the subject, which can reduce the labor intensity of the operator. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] FIG1 is a schematic diagram of the arrangement of an external magnet of a capsule endoscope control system provided by an embodiment;

[0029] FIG2 is a schematic diagram of a sensor measuring distance of a capsule endoscope control system provided by an embodiment;

[0030] FIG3 is a schematic diagram showing the connection between a sensor and a control device of a capsule endoscope control system provided by an embodiment;

[0031] FIG4 is a schematic diagram of a capsule endoscope control system provided by an embodiment for inspecting an endoscope in a subject's body cavity.

[0032] The reference numerals in the drawings of the specification include:

[0033] 100 - object, 101 - robot arm, 102 - external magnet, 103 - housing, 104 - sensor, 105 - transmitter, 106 - receiver, 107 - subject. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0035] This embodiment provides a capsule endoscope control method, including the following process:

[0036] When the external magnet moves and drives the endoscope to move, it is detected whether there is an object within a first preset distance range of the outer end surface of the external magnet. If there is an object within the first preset distance range of the outer end surface of the external magnet, the external magnet is controlled to perform a preset action.

[0037] The endoscope is provided with a magnet, namely, an internal magnet. Based on the magnetic interaction between the external magnet and the internal magnet, the external magnet is moved, and the internal magnet can be driven to move through the external magnet, thereby driving the endoscope to move, for example, the endoscope can be driven to translate, rotate or roll. The endoscope is a capsule endoscope, which can enter the body cavity of the subject to examine the subject's body cavity.

[0038] The outer end face of the external magnet is an end face of the external magnet close to the endoscope. The external magnet is outside the body of the subject. When the endoscope enters the body cavity of the subject, it is detected whether there is an object within a first preset distance range of the outer end face of the external magnet, and whether the distance from the subject's body to the external magnet is within the first preset distance range can be detected.

[0039] The capsule endoscope control method of the present embodiment can control the external magnet to perform a preset action to prevent the external magnet from continuing to move and colliding with the subject when the external magnet is close to the subject and is about to collide with the subject during the process of the external magnet moving and driving the endoscope to move. This can reduce the situation where the external magnet collides with the subject and makes it unnecessary for the operator to continuously concentrate on observing the movement of the external magnet to prevent the external magnet from colliding with the subject, thereby reducing the operator's labor intensity to a certain extent.

[0040] In some embodiments, detecting whether there is an object within a first preset distance range of the outer end face of the external magnet includes: measuring the distance from an object existing on one side of the outer end face of the external magnet to the external magnet, determining whether the distance is within the first preset distance range, and if so, determining that there is an object within the first preset distance range of the outer end face of the external magnet. For one side of the outer end face of the external magnet, the distance from the object existing in the area to the external magnet is measured, and based on the distance from the object to the external magnet, it is determined whether the object is within the first preset distance range, thereby detecting whether there is an object within the first preset distance range of the outer end face of the external magnet. In this embodiment, the method for measuring the distance from an object existing on one side of the outer end face of the external magnet to the external magnet is not limited.

[0041] In some embodiments, detecting whether there is an object within a first preset distance range of the outer end face of the external magnet includes: sending a modulation signal to one side of the outer end face of the external magnet and receiving an echo signal reflected by the modulation signal from the object, obtaining the time elapsed from sending the modulation signal to receiving the echo signal according to the phase delay of the echo signal, and obtaining the distance from the object on one side of the outer end face of the external magnet to the external magnet according to the time length. In this embodiment, a non-contact measurement method is adopted, and the measurement is performed by sending a modulation signal and receiving the reflected echo signal. By comparing the phase of the echo signal with the phase of the sent modulation signal, the phase delay amount generated after the signal goes back and forth once is obtained. The time elapsed from sending the modulation signal to receiving the echo signal, that is, the time elapsed for the signal to go back and forth once, can be obtained according to the phase delay amount and the angular frequency of the modulation signal, and then the distance can be obtained according to the time length and the signal propagation speed. For example, assuming that the propagation speed of the modulation signal is c, the angular frequency is ω, and the phase delay of a round trip on the measurement path is φ, then the corresponding duration t=φ / ω, and it can be concluded that d=1 / 2 * (c*t)=1 / 2 * (c*φ / ω). The modulation signal can be, but is not limited to, a sinusoidal modulation signal. The modulation signal can be a light wave signal or an ultrasonic signal.

[0042] In some embodiments, detecting whether there is an object within a first preset distance range of the outer end face of the external magnet includes: sending a modulation signal to one side of the outer end face of the external magnet and receiving an echo signal of the modulation signal reflected by the object, and obtaining the distance from the object on one side of the outer end face of the external magnet to the external magnet according to the time elapsed from the moment the modulation signal is sent to the moment the echo signal is received. Exemplarily, assuming that the propagation speed of the modulation signal is c, the moment the modulation signal is sent is t1, and the moment the echo signal is received is t2, then the time t=t2-t1 corresponding to the round-trip propagation of the signal, and the distance d can be obtained according to the propagation speed c and the time t. The modulation signal can be a light wave signal, and this embodiment adopts a time-of-flight ranging method.

[0043] In some embodiments, a plurality of sensors are provided on the outer end surface of the external magnet, and the sensors are used to detect whether there is an object within a first preset distance range of the outer end surface of the external magnet. If there is an object within the first preset distance range of the outer end surface of the external magnet, controlling the external magnet to perform a preset action includes: if at least one of the sensors detects that there is an object within the first preset distance range of the outer end surface of the external magnet, controlling the external magnet to perform a preset action. By providing a plurality of sensors on the outer end surface of the external magnet and controlling the external magnet according to the detection results of the plurality of sensors, it is possible to avoid the situation that the sensor fails to accurately detect the object when only one sensor is provided, and the situation of missed detection or wrong detection can be avoided. The setting of a plurality of sensors can improve the detection accuracy, thereby effectively avoiding the external magnet from colliding with the subject. For example, reference can be made to FIG. 1, which is a schematic diagram of the setting of an external magnet of a capsule endoscope control system provided in an embodiment. As shown in the figure, an external magnet 102 is provided at the end of a mechanical arm 101, and a plurality of sensors 104 are provided on the outer end surface of the external magnet 102, and each sensor 104 detects the distance respectively.

[0044] In some embodiments, if an object is detected within the first preset distance range of the outer end surface of the external magnet 102, a low level is output, otherwise a high level is output. In some embodiments, if an object is detected within the first preset distance range of the outer end surface of the external magnet 102, controlling the external magnet 102 to perform a preset action may include: outputting SC=S1 && S2 && S3…&& Sn, and if the output SC is a low level, controlling the external magnet 102 to perform a preset action, wherein n sensors are provided on the outer end surface of the external magnet 102, S1, S2, S3,…, Sn represent the output of the first sensor, the output of the second sensor, the output of the third sensor,… and the output of the nth sensor, respectively, and n is a positive integer greater than 1, and any of the sensors is used to output a low level when an object is detected within the first preset distance range of the outer end surface of the external magnet 102, otherwise a high level is output. Output SC = S1 && S2 && S3…&& Sn, then, if at least one of the n sensors outputs a low level, the output SC is a low level; if all n sensors output a high level, the output SC is a high level.

[0045] In this embodiment, the first preset distance range is not limited and can be set accordingly in practical applications. In some embodiments, the first preset distance range can be less than or equal to the preset distance, that is, detecting whether there is an object within a range less than or equal to the preset distance of the outer end surface of the external magnet 102.

[0046] Exemplarily, n sensors are arranged on the outer end surface of the external magnet 102, and the output of each sensor is represented as S1, S2, S3, ..., Sn in sequence. For the output S of any sensor, if d≥d0, S=1, indicating a high output level, and if d<d0, S=0, indicating a low output level. Among them, d represents the distance of the object measured by the sensor, and d0 represents the preset distance. The output is represented as SC=S1 && S2 && S3...&& Sn, and the outputs of multiple sensors 104 are output through Boolean logic calculation. Therefore, as long as any sensor 104 detects the presence of an obstacle, the output after logical calculation will send a low-level signal to control the external magnet 102 to perform a preset action to avoid collision with the subject 107. In a specific example, the value range of the preset distance d0 is 5~20cm.

[0047] In some embodiments, controlling the external magnet 102 to perform a preset action includes: controlling the external magnet 102 to stop moving, or controlling the external magnet 102 to reduce its moving speed. During the process of the external magnet 102 moving and driving the endoscope to move, if an object is detected within the first preset distance range of the outer end surface of the external magnet 102, the external magnet 102 is controlled to stop moving to prevent the external magnet 102 from continuing to move and colliding with the subject. Alternatively, during the process of the external magnet 102 moving and driving the endoscope to move, if an object is detected within the first preset distance range of the outer end surface of the external magnet 102, the external magnet 102 can be controlled to slow down its moving speed to prevent the external magnet 102 from moving too fast and continuing to move and colliding with the subject 107, which helps to reduce the risk of the external magnet 102 colliding with the subject 107. In other embodiments, the external magnet 102 can also be controlled to perform other actions to prevent the external magnet 102 from colliding with the subject 107.

[0048] This embodiment also provides a capsule endoscope control system, including:

[0049] The sensor 104 is disposed on the outer end surface of the external magnet 102 and is used to detect whether there is an object within a first preset distance range of the outer end surface of the external magnet 102 when the external magnet 102 moves and drives the endoscope to move;

[0050] The control device is connected to the sensor 104 and is used to control the external magnet 102 to perform a preset action if there is an object within the first preset distance range of the outer end surface of the external magnet 102.

[0051] The endoscope is provided with a magnet, namely, an internal magnet. Based on the magnetic interaction between the external magnet 102 and the internal magnet, the external magnet 102 is moved, and the internal magnet can be driven to move through the external magnet 102, thereby driving the endoscope to move, for example, the endoscope can be driven to translate, rotate or roll. The endoscope is a capsule endoscope, which can enter the body cavity of the subject 107 to examine the body cavity of the subject 107.

[0052] The outer end face of the external magnet 102 is an end face of the external magnet 102 close to the endoscope. The external magnet 102 is outside the body of the subject 107. When the endoscope enters the body cavity of the subject 107, it is detected whether there is an object within a first preset distance range of the outer end face of the external magnet 102, and whether the distance from the subject 107 to the external magnet 102 is within the first preset distance range can be detected.

[0053] The capsule endoscope control system of the present embodiment can control the external magnet to perform a preset action to avoid the external magnet from colliding with the subject when the external magnet is close to the subject and is about to collide with the subject during the process of the external magnet moving and driving the endoscope to move. This can reduce the chances of the external magnet colliding with the subject and makes it unnecessary for the operator to continuously concentrate on observing the movement of the external magnet to prevent the external magnet from colliding with the subject, thereby reducing the operator's labor intensity to a certain extent.

[0054] In some embodiments, a plurality of sensors 104 are provided on the outer end surface of the external magnet 102. The external magnet 102 is controlled according to the detection results of the plurality of sensors 104, so that when only one sensor 104 is provided, the sensor may fail to accurately detect the object, resulting in missed detection or misdetection. The plurality of sensors 104 may be provided to improve the detection accuracy, thereby effectively preventing the external magnet 102 from colliding with the subject 107. The plurality of sensors 104 may be arranged evenly, so as to more evenly detect the distance of the object on one side of the outer end surface of the external magnet 102. For example, reference may be made to FIG1, as shown in the figure, the external magnet 102 is cylindrical, and a sensor 104 at a central position and a plurality of sensors 104 arranged around the central position are provided on the outer end surface of the external magnet 102, so that each sensor 104 is evenly arranged.

[0055] In some embodiments, the sensor 104 includes a transmitter and a receiver, the transmitter is used to send a modulated signal, and the receiver is used to receive an echo signal reflected by the object, so as to obtain the distance from the object on the outer end surface of the external magnet 102 to the external magnet 102 according to the echo signal and the modulated signal. For example, reference may be made to FIG2, which is a schematic diagram of a sensor measuring distance of a capsule endoscope control system provided by an embodiment, as shown in the figure, the transmitter 105 sends a modulated signal, and the receiver 106 receives an echo signal reflected by the object 100. The sensor 104 may be, but is not limited to, a photoelectric sensor that sends a light wave signal or an ultrasonic sensor that sends an ultrasonic signal.

[0056] In some embodiments, the control device may include a computing module, a control module, and a motor. For example, reference may be made to FIG3, which is a schematic diagram of the connection between a sensor and a control device of a capsule endoscope control system provided in an embodiment. A plurality of sensors 104 may be provided on the outer end surface of the external magnet 102, including sensors 1 to n, and the outputs are sequentially represented as S1, S2, S3, ..., Sn. The computing module performs logical calculations based on the outputs of sensors 1 to n, and outputs SC to the control module. The control module issues instructions based on the output SC to control the external magnet 102 through the motor. The control device may include but is not limited to a programmable logic controller (PLC). According to the outputs of the plurality of sensors 104, a low-level signal is sent to the programmable logic controller when an object is detected within a first preset distance range of the external magnet 102. After the programmable logic controller detects the signal, it issues an instruction to suspend the machine movement to avoid collision with the subject 107.

[0057] In some embodiments, the control device includes a mechanical arm, at the end of which the external magnet 102 is provided, and the external magnet 102 is driven to move by the mechanical arm. For example, reference can be made to FIG. 1 and FIG. 4, which is a schematic diagram of a capsule endoscope control system provided by an embodiment for controlling and inspecting an endoscope in a body cavity of a subject. The external magnet 102 is provided at the end of the mechanical arm 101, provided in a housing 103, and installed through the housing 103. The subject 107 is on the inspection table, and the external magnet 102 moves outside the body of the subject 107, which can drive the endoscope in the body cavity of the subject 107 to move. The external magnet 102 is driven to move by the mechanical arm 101, and the magnetic action between the external magnet 102 and the internal magnet of the endoscope is relied on to control the endoscope to perform translation, rotation, tumbling and other movements in the body cavity of the subject 107, thereby realizing a controllable inspection of the subject 107, such as an inspection of the human stomach.

[0058] The capsule endoscope control method and system of this embodiment can detect the distance between the external magnet and the subject in real time. When the distance between the magnet and the subject is within a corresponding range, the external magnet can be automatically controlled to stop moving, which greatly reduces the burden on the operator, avoids collision injuries caused by misoperation, and makes automatic operation of the external magnet possible.

[0059] The above is a detailed introduction to a capsule endoscope control method and system provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A capsule endoscope control method, characterized in that: include: When the external magnet moves and drives the endoscope to move, detecting whether there is an object within a first preset distance range of the outer end surface of the external magnet; If there is an object within the first preset distance range of the outer end surface of the external magnet, the external magnet is controlled to perform a preset action.

2. The capsule endoscope control method according to claim 1, characterized in that: Detecting whether there is an object within a first preset distance range of the outer end surface of the external magnet includes: The distance from an object on one side of the outer end surface of the external magnet to the external magnet is measured to determine whether the distance is within the first preset distance range. If so, it is determined that there is an object within the first preset distance range of the outer end surface of the external magnet.

3. The capsule endoscope control method according to claim 1, characterized in that: Detecting whether there is an object within a first preset distance range of the outer end surface of the external magnet includes: A modulation signal is sent to one side of the outer end surface of the external magnet, and an echo signal of the modulation signal reflected by the object is received. The time elapsed from the sending of the modulation signal to the receiving of the echo signal is obtained according to the phase delay of the echo signal, and the distance from the object on the outer end surface of the external magnet to the external magnet is obtained according to the time length.

4. The capsule endoscope control method according to claim 1, characterized in that: A plurality of sensors are arranged on the outer end surface of the external magnet, and the sensors are used to detect whether there is an object within a first preset distance range of the outer end surface of the external magnet; If there is an object within the first preset distance range of the outer end surface of the external magnet, controlling the external magnet to perform a preset action includes: If at least one of the sensors detects that there is an object within a first preset distance range of the outer end surface of the external magnet, the external magnet is controlled to perform a preset action.

5. The capsule endoscope control method according to claim 4, characterized in that: If there is an object within the first preset distance range of the outer end surface of the external magnet, controlling the external magnet to perform a preset action includes: Output SC= S1 && S2 && S3…&& Sn. If the output SC is a low level, the external magnet is controlled to perform a preset action, wherein n sensors are arranged on the outer end surface of the external magnet, S1, S2, S3,…, Sn respectively represent the output of the first sensor, the output of the second sensor, the output of the third sensor,… and the output of the nth sensor, n is a positive integer greater than 1, and any of the sensors is used to output a low level when detecting that there is an object within a first preset distance range of the outer end surface of the external magnet, otherwise it outputs a high level.

6. The capsule endoscope control method according to any one of claims 1 to 5, characterized in that: Controlling the external magnet to perform a preset action includes: The external magnet is controlled to stop moving, or the moving speed of the external magnet is controlled to decrease.

7. A capsule endoscope control system, characterized in that: include: A sensor, disposed on an outer end surface of the external magnet, for detecting whether there is an object within a first preset distance range of the outer end surface of the external magnet during the movement of the external magnet and the movement of the endoscope; A control device is connected to the sensor and is used to control the external magnet to perform a preset action if there is an object within the first preset distance range of the outer end surface of the external magnet.

8. The capsule endoscope control system according to claim 7, characterized in that: A plurality of the sensors are arranged on the outer end surface of the external magnet, and the plurality of the sensors are evenly arranged.

9. The capsule endoscope control system according to claim 7, characterized in that: The control device comprises a mechanical arm, at the end of which the external magnet is arranged, and the external magnet is driven to move by the mechanical arm.

10. The capsule endoscope control system according to claim 7, characterized in that: The sensor includes a transmitting part and a receiving part, the transmitting part is used to send a modulated signal, and the receiving part is used to receive an echo signal reflected by the object when the modulated signal is reflected, so as to obtain the distance from the object on one side of the outer end surface of the external magnet to the external magnet based on the echo signal and the modulated signal.

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