WO2019220907A1 - Magnetic field measurement unit and magnetic field measurement system - Google Patents

Magnetic field measurement unit and magnetic field measurement system Download PDF

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Publication number
WO2019220907A1
WO2019220907A1 PCT/JP2019/017557 JP2019017557W WO2019220907A1 WO 2019220907 A1 WO2019220907 A1 WO 2019220907A1 JP 2019017557 W JP2019017557 W JP 2019017557W WO 2019220907 A1 WO2019220907 A1 WO 2019220907A1
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magnetic field
measurement
sensor
environmental
magnetic
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PCT/JP2019/017557
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French (fr)
Japanese (ja)
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孝二郎 関根
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コニカミノルタ株式会社
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Priority to JP2020519551A priority Critical patent/JP7226717B2/en
Publication of WO2019220907A1 publication Critical patent/WO2019220907A1/en

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/025—Compensating stray fields
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/10—Plotting field distribution ; Measuring field distribution

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  • the present invention relates to magnetic field measurement.
  • Magnetic measurement devices particularly magnetic field distribution measurement devices that measure the two-dimensional or three-dimensional distribution of a magnetic field generated from a measurement object, are excellent in detectability of abnormal points, and have abnormalities in measurement objects in non-destructive inspection and medical fields. Useful for diagnosing the condition. In some cases, such as when the measurement object is a human or other living organism, movement of the measurement object during measurement is unavoidable. When the measurement object to which the magnetic sensor is fixed moves, the magnetic sensor itself also moves and changes the measurement point, so the magnetic field strength of the environmental magnetic field at the measurement point also changes. In addition, an induced magnetic field is generated by movement in the environmental magnetic field. Accordingly, since the environmental magnetic field and the induction magnetic field that can be changed by movement are measured by the magnetic sensor, the magnetic field component generated from the measurement target cannot be accurately evaluated.
  • the detection data of the geomagnetic sensor still includes the environmental magnetic field and the induction magnetic field that can be changed by the movement of the geomagnetic sensor.
  • the biomagnetic measurement device described in Patent Document 2 before and after the biomagnetic field measurement, the magnetic field from the oscillation coil attached to the subject is measured to detect the movement of the subject, and the subject moves. Discard the biomagnetic field data.
  • the environmental magnetic field and the induction magnetic field that can be changed by the movement of the magnetic sensor are not excluded from the measurement signal of the magnetic sensor.
  • the measurement signal includes an environmental magnetic field or an induction magnetic field that can be changed by the movement of the magnetic sensor
  • the magnetic field component generated from the measurement object cannot be accurately evaluated.
  • the measurement object is very weak and greatly affected. Therefore, when the measurement object can move, the measurement data when the measurement object moves as described in Patent Document 2 must be discarded.
  • the measurement object is restrained so as not to move, there is a problem that when the measurement object is a human or other organism, the burden on the organism is large and it is difficult to prevent the measurement object from moving completely.
  • the present invention has been made in view of the above problems in the prior art, and in a configuration in which a magnetic field generated from a measurement object is measured by a magnetic sensor fixed to the measurement object, the measurement object is not restrained. It is an object to accurately measure a magnetic field component generated from a measurement object, including measurement based on a measurement magnetic field signal by the magnetic sensor during movement of the measurement object and the magnetic sensor.
  • the invention according to claim 1 for solving the above-described problem is a magnetic field measurement unit that can be attached to a measurement object so that the position with respect to the measurement object is fixed, and measures a magnetic field from the measurement object. And a motion detection sensor that detects the motion of the magnetic field measurement unit.
  • the invention according to claim 2 is the magnetic field measurement unit according to claim 1, wherein the measurement magnetic sensor measures a magnetic field distribution from a measurement object.
  • the measurement magnetic sensor and the motion detection sensor are integrated on the same semiconductor substrate or mounted and integrated on the same circuit substrate. It is a magnetic field measurement unit as described in above.
  • the invention according to claim 4 is the magnetic field measurement unit according to any one of claims 1 to 3,
  • a magnetic field measurement system comprising: an environmental magnetic sensor that measures an environmental magnetic field in a space containing a measurement object on which the magnetic field measurement unit is mounted.
  • the invention according to claim 5 includes an arithmetic unit that calculates a measurement value based on a measurement magnetic field signal from the measurement magnetic sensor, a motion detection signal from the motion detection sensor, and an environmental magnetic field signal from the environmental magnetic sensor,
  • the arithmetic device estimates an environmental magnetic field and an induced magnetic field at the position according to the position and moving speed of the measurement magnetic sensor at the time of measurement of the measurement magnetic field signal based on the motion detection signal and the environmental magnetic field signal.
  • the magnetic field measurement system according to claim 4 wherein the environmental magnetic field and the induction magnetic field are subtracted from the measurement magnetic field signal to obtain a measurement value.
  • the invention according to claim 6 includes an arithmetic unit that calculates a measurement value based on a measurement magnetic field signal from the measurement magnetic sensor, a motion detection signal from the motion detection sensor, and an environmental magnetic field signal from the environmental magnetic sensor,
  • the arithmetic unit is: A first step of obtaining the measurement magnetic field signal from the measurement magnetic sensor; A second step of obtaining the motion detection signal from the motion detection sensor; A third step of acquiring the environmental magnetic field signal from the environmental magnetic sensor; Based on the environmental magnetic field signal acquired in the third step and the motion detection signal acquired in the second step, the measurement magnetic field signal acquired in the first step is corrected to be a measurement value.
  • the invention according to claim 7 is a fifth step of calculating a position of the measurement magnetic sensor at the time of acquisition of the measurement magnetic field signal in the first step based on the motion detection signal acquired in the second step; A sixth step of estimating the environmental magnetic field at the position calculated in the fifth step based on the environmental magnetic field signal acquired in the third step;
  • the eleventh step of subtracting the ambient magnetic field estimated in the ninth step and the induced magnetic field estimated in the tenth step from the measured magnetic field signal acquired in the first step is included in the fourth step.
  • Item 7. The magnetic field measurement system according to Item 6.
  • the measurement object and the magnetism during movement of the magnetic sensor are not restrained.
  • the magnetic field component generated from the measurement object can be accurately measured, including the measurement based on the measurement magnetic field signal from the sensor.
  • FIG. 1 is a perspective view showing a magnetic field distribution measurement system according to an embodiment of the present invention. It is a plane schematic diagram which shows the magnetic field distribution measurement system which concerns on one Embodiment of this invention.
  • FIG. 3 is a schematic plan view showing a magnetic field distribution measurement system according to an embodiment of the present invention, which differs from FIG. 2 in the number of installed environmental magnetic sensors.
  • FIG. 4 is a schematic plan view showing a magnetic field distribution measurement system according to an embodiment of the present invention, which is different from FIGS. 2 and 3 in the number of installed environmental magnetic sensors. It is a plane schematic diagram which shows the magnetic field distribution measurement system which concerns on one Embodiment of this invention.
  • FIG. 1 shows the configuration of the magnetic field distribution measurement system of this embodiment.
  • the magnetic field distribution measurement system 1 includes a magnetic field distribution measurement unit 10, an environmental magnetic sensor 20, and an arithmetic device 30.
  • the case where the measurement object is the head 2a of the human body (subject) 2 is taken as an example.
  • the vertical coordinate in the space 3 containing the measurement object is Z, and the two axes perpendicular to the Z axis and perpendicular to each other are X and Y.
  • FIG. 2 shows a schematic diagram of the XY plane.
  • the magnetic field distribution measurement unit 10 integrally includes a measurement magnetic sensor 11 that measures the magnetic field distribution from the head 2 a and a motion detection sensor 12 that detects the motion of the magnetic field measurement unit 10.
  • the measurement magnetic sensor 11 includes a sensor array module in which a plurality of sensor elements are arranged two-dimensionally or three-dimensionally, and is a two-dimensional configuration along the surface of the head 2a or a 3D axis that is perpendicular to the two-dimensional plane. Dimensional magnetic field distribution can be measured. For example, it can be implemented by applying a tunnel magnetoresistive element as the sensor element.
  • the measurement magnetic sensor 11 is simply shown, and each sensor element is arranged so as to face the surface of the adjacent head 2a, or the sensor array covers the measurement target region on the surface of the head 2a.
  • the arrangement to be arranged in this way is designed as appropriate.
  • Communication connection between the arithmetic unit 30 and the magnetic field distribution measurement unit 10 and the environmental magnetic sensor 20 is performed by wire or wirelessly.
  • the magnetic field distribution measurement unit 10 is preferably wirelessly connected.
  • the magnetic field distribution measurement unit 10 can be mounted on the head 2a so that the position with respect to the head 2a is fixed. As shown in FIG. 1, the magnetic field distribution measurement unit 10 is attached to the head 2a to measure the magnetic field generated from the head 2a.
  • the motion detection sensor 12 It is sufficient for the motion detection sensor 12 to be able to detect a factor capable of calculating the current position and the moving speed.
  • an acceleration sensor is applied. Since there is a possibility of movement in the triaxial direction, an acceleration sensor is provided so that acceleration in the triaxial direction can be detected.
  • the magnetic field distribution measurement unit 10 is arranged at a known coordinate, the coordinate is stored as the origin coordinate in the arithmetic unit 30, and each movement amount in the XYZ directions from the origin coordinate is set to zero.
  • the calculation device 30 calculates the current position and movement speed after movement based on the output signal of the acceleration sensor.
  • the motion detection sensor 12 is provided for recognizing the current position and the moving speed of the measurement magnetic sensor 11.
  • the motion detection sensor 12 is integrated with the measurement magnetic sensor 11 and is provided as close as possible.
  • the measurement magnetic sensor 11 and the motion detection sensor 12 may be implemented by constituting a monolithic semiconductor chip integrated on the same semiconductor substrate. Further, a configuration may be implemented in which the semiconductor chip constituting the measurement magnetic sensor 11 and the semiconductor chip constituting the motion detection sensor 12 are mounted close to each other on the same circuit board.
  • the environmental magnetic sensor 20 is for measuring the environmental magnetic field He in the space 3, and one or more are installed in the space 3.
  • the computing device 30 calculates a measurement value based on the measurement magnetic field signal from the measurement magnetic sensor 11, the motion detection signal from the motion detection sensor 12, and the environmental magnetic field signal from the environmental magnetic sensor 20. In this embodiment, magnetic field distribution data corresponding to the magnetoencephalogram is calculated.
  • Space 3 is a space in the room. This is to prevent the departure of the subject 2 from the space 3 and the intrusion of others and other objects into the space 3.
  • An environmental magnetic sensor 20 is installed at a corner or the like in the space 3, and the environmental magnetic sensor 20 measures an environmental magnetic field (mainly geomagnetism) in the space 3.
  • an environmental magnetic field mainly geomagnetism
  • one (Fig. 2), two (Fig. 3), and four (Fig. 4) environmental magnetic sensors 20 are arranged, and more than two in the Z direction. It is also possible to obtain the environment magnetic field in the space 3 as a distribution having the space coordinates XYZ.
  • the environmental magnetic sensor 20 is assumed to be the same as the magnetic field intensity measured by the environmental magnetic sensor 20 at any position in the space 3 (FIG. 2). There is no problem with processing.
  • the environmental magnetic field distribution between the two environmental magnetic sensors 20 can be estimated to be linearly changed and subjected to interpolation processing. Therefore, the accuracy increases as the number of environmental magnetic sensors 20 increases, but the cost also increases.
  • the number of environmental magnetic sensors 20 may be determined in consideration of the uniformity of the environmental magnetic field in the space 3.
  • the moving velocity vector, the head 2a biomagnetic field, the environmental magnetic field, and the induction magnetic field at two different measurement points S1 and S2 are respectively set as v1, Hm1, He1, Hi1, v2, Hm2, He2, and Hi2. .
  • the head 2a is obtained by subtracting the environmental magnetic field at the measurement points (S1, S2) estimated from the environmental magnetic field signal of the environmental magnetic sensor 20 from the measurement magnetic field signal output from the measurement magnetic sensor 11. It is possible to acquire the magnetic field distribution derived from the part 2a.
  • the situation where the head 2a is not moving is a situation where v1 is zero at the measurement point S1, for example.
  • the arithmetic unit 30 firstly obtains a measurement magnetic field signal from the measurement magnetic sensor 11, a second step S ⁇ b> 12 obtains a motion detection signal from the motion detection sensor 12, and The third step S13 for acquiring the environmental magnetic field signal from the environmental magnetic sensor 20 is executed simultaneously. Next, based on the environmental magnetic field signal acquired in the third step S13 and the motion detection signal acquired in the second step S12, the measurement magnetic field signal acquired in the first step S11 is corrected to be a measurement value. Step S14 is executed.
  • the position (measurement point (S1, S2)) of the measurement magnetic sensor 11 at the time of acquisition of the measurement magnetic field signal in the 1st step S11 was acquired in the 2nd step S12.
  • the fifth step S15 calculated based on the motion detection signal and the environmental magnetic field signal (He1, He2) at the position (measurement point (S1, S2)) calculated in the fifth step S15 are acquired in the third step S13.
  • the sixth step S16 estimated based on the above and the seventh step S17 for subtracting the environmental magnetic field estimated in the sixth step S16 from the measured magnetic field signal acquired in the first step S11 are executed.
  • the magnetic field distribution from the head 2a is acquired even while the head 2a is moving. Since the measurement magnetic sensor 11 is fixed to the head 2a, the movement of the head 2a and the movement of the measurement magnetic sensor 11 are substantially the same. As shown in FIG. 5, when the measurement magnetic sensor 11 moves with speed in the environmental magnetic field in the space 3 (when v1 and v2 are not zero), an induced current and an induced magnetic field are generated in the sensor, and the measurement magnetic sensor 11 It is superimposed on the output signal. The induced magnetic field can be converted from the “environmental magnetic field” and the “movement speed”.
  • the measurement magnetic sensor 11 Even if the head 2a moves, the measurement magnetic sensor 11 simultaneously moves to the same position at the same speed, so it can be assumed that the head 2a viewed from the measurement magnetic sensor does not move, and the magnetic field distribution from the head 2a deviates. It is measured without any change.
  • the measurement magnetic sensor 11 for example, a tunnel magnetoresistive element, etc., uses the magnetoresistive effect.
  • the environmental magnetic field (He1, He2) traversing the conductor of the electrical circuit) can change its direction, size, and relative direction as the spatial position changes.
  • the position and moving speed of the measurement magnetic sensor 11 can be known from the motion detection signal of the motion detection sensor 12.
  • the induced magnetic field (Hi1, Hi2) can be calculated from the movement amount of the environmental magnetic field accompanying the movement of the head 2a, and hence the movement of the measurement magnetic sensor 11 and the movement detection sensor 12, and the moving speed.
  • Measurement magnetic signal (Biomagnetic signal) + (Environmental magnetic field signal) + (Inductive magnetic field signal).
  • the arithmetic unit 30 firstly obtains a measurement magnetic field signal from the measurement magnetic sensor 11, and a second step S ⁇ b> 12 obtains a movement detection signal from the movement detection sensor 12.
  • the third step S13 for acquiring the environmental magnetic field signal from the environmental magnetic sensor 20 is executed with the synchronization.
  • the measurement magnetic field signal acquired in the first step S11 is corrected to be a measurement value.
  • Step S14 is executed.
  • the fourth step S14 as shown in FIG.
  • the position (measurement points (S1, S2)) and the moving speed (v1, v2) of the measurement magnetic sensor 11 when the measurement magnetic field signal is acquired in the first step S11 are obtained.
  • the induced magnetic field (Hi1, Hi2) at the position (measurement point (S1, S2)) calculated in the eighth step S18 and the ninth step S19 estimated based on the environmental magnetic field signal acquired in step S13 is obtained.
  • the tenth step S20 and the eleventh step S21 in which the environmental magnetic field estimated in the ninth step S19 and the induction magnetic field estimated in the tenth step S20 are subtracted from the measured magnetic field signal acquired in the first step S11 are executed. .
  • the passive magnetic shield has a configuration in which a soft magnetic plate 4 such as a permalloy plate is spread around the periphery, and can reduce an environmental magnetic field such as geomagnetism. Nevertheless, it is difficult to completely reduce the environmental magnetic field in the space 3, and it is difficult to reduce the induced magnetic field when the head 2a moves.
  • the active magnetic shield (FIG. 9C) is arranged around the space 3 according to the output of the environmental magnetic sensor for active magnetic shield (which may be installed separately from the environmental magnetic sensor 20 of the magnetic field distribution measurement system 1). Is configured to cancel and reduce the environmental magnetic field in the space 3 by driving a magnetic field generator (coil or the like) 5 disposed in the space. Again, it is difficult to completely reduce the environmental magnetic field in the space 3, and it is difficult to reduce the induced magnetic field when the head 2a moves. Therefore, by using this magnetic field distribution measurement system 1, both the environmental magnetic field and the induced magnetic field can be canceled by software.
  • the measurement object and the measurement object are not restrained.
  • the magnetic field component generated from the measurement object can be accurately measured, including the measurement based on the measurement magnetic field signal by the magnetic sensor during movement of the magnetic sensor.
  • a good magnetic field distribution signal can be obtained even if the measurement object is moving. Since the restraint that the subject 2 should not move during the measurement is eliminated, the burden on the person is greatly reduced. Further, even when an animal that is not bound is used as a measurement object, the burden on the measurement object is small, and a high-quality magnetic field distribution signal can be obtained.
  • the technology for canceling the environmental magnetic field and the induction magnetic field of the present invention is effective even in a configuration in which the magnetic field distribution is not measured and the magnetic field intensity at one point is measured regardless of the above embodiment.
  • the magnetic field distribution measurement unit 10 is arranged at known coordinates in order to set the origin coordinates.
  • the method for setting the origin coordinates is not limited to this, and other methods may be used. The following method can be mentioned as an example.
  • the magnetic field distribution measurement unit 10 not attached to the head 2a is placed at an arbitrary position in the space 3, and only the environmental magnetic field is detected by the measurement magnetic sensor 11.
  • a plurality of environmental magnetic sensors 20 are provided.
  • the position coordinates of the measurement magnetic sensor 11 in the space 3 are estimated. Since the environmental magnetic field distribution in the space 3 can be estimated based on the plurality of environmental magnetic sensors 20 as described above, the position of the measurement magnetic sensor 11 is determined from the environmental magnetic field measured by the measurement magnetic sensor 11 using the estimated environmental magnetic field distribution. (The reverse of the process of estimating the environmental magnetic field at the position from the position of the measurement magnetic sensor 11 is performed). The position coordinates in the space 3 of the measurement magnetic sensor 11 estimated as described above are set as the origin coordinates.
  • a plurality of position detecting magnetic field oscillators controlled by the arithmetic unit 30 are prepared and installed at locations separated from each other.
  • the arithmetic unit 30 causes the position detection magnetic field oscillator to transmit a predetermined position detection magnetic field signal at a certain timing, extracts the position detection magnetic field signal from the measurement magnetic field signal by the measurement magnetic sensor 11, and the space of the position detection magnetic field signal
  • the distance from each position detecting magnetic field oscillator to the measurement magnetic sensor 11 is estimated by analyzing the time difference and attenuation rate due to propagation. From the distance of the measurement magnetic sensor 11 to the plurality of position detection magnetic field oscillators as described above, the position coordinate in the space 3 of the measurement magnetic sensor 11 is specified, and the specified position coordinate is set as the origin coordinate. Further, the position magnetic field signal may be detected simultaneously by the measurement magnetic sensor 11 and the plurality of environmental magnetic sensors 20, so that the analysis may be performed at the relative position of the measurement magnetic sensor 11 with respect to the plurality of environmental magnetic sensors 20.
  • the present invention can be used for a magnetic field measurement unit and a magnetic field measurement system.
  • Magnetic field distribution measurement system Human body (subject) 2a head 3 space 10 magnetic field distribution measurement unit 11 measurement magnetic sensor 12 motion detection sensor 20 environmental magnetic sensor 30 arithmetic unit

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Abstract

A magnetic field measurement unit 10 mountable to a measurement object (2a) so that the position of the magnetic field measurement unit 10 with respect to the measurement object is fixed, wherein the magnetic field measurement unit has, as an integrated body, a measurement magnetic sensor 11 for measuring a magnetic field from the measurement object, and a motion detection sensor 12 for detecting motion of the magnetic field measurement unit. A magnetic field measurement system 1 is provided with an environment magnetic sensor 20 for measuring an environment magnetic field of a space 3 containing a measurement object to which the magnetic field measurement unit is mounted, and a computation device 30. The computation device calculates an environment magnetic field and an induced magnetic field at the position of the measurement magnetic sensor during measurement of a measurement magnetic field signal, the environment magnetic field and the induced magnetic field corresponding to the position and movement speed of the measurement magnetic sensor, and obtains a measurement value by subtracting the environment magnetic field and induced magnetic field pertaining to the calculation from the measurement magnetic field signal.

Description

磁場測定ユニット及び磁場測定システムMagnetic field measurement unit and magnetic field measurement system
　本発明は、磁場測定に関する。 The present invention relates to magnetic field measurement.
　磁気測定装置、特に測定対象物から発生する磁場の２次元又は３次元分布を測定する磁場分布測定装置は、異常箇所の検出性に優れ、非破壊検査や医学の分野において測定対象物の異常等の状態を診断することに役立つ。
　測定対象物が人その他の生物である場合など、測定中における測定対象物の移動が避けられない場合がある。磁気センサーが固定された測定対象物が移動すると、磁気センサー自体も移動して測定点が変化するからその測定点における環境磁場の磁場強度も変化する。また、環境磁場中の移動によって誘導磁場が発生する。したがって、移動により変化し得る環境磁場と誘導磁場が磁気センサーによって測定されるため、測定対象物から発生する磁場成分を正確に評価することができない。 Magnetic measurement devices, particularly magnetic field distribution measurement devices that measure the two-dimensional or three-dimensional distribution of a magnetic field generated from a measurement object, are excellent in detectability of abnormal points, and have abnormalities in measurement objects in non-destructive inspection and medical fields. Useful for diagnosing the condition.
In some cases, such as when the measurement object is a human or other living organism, movement of the measurement object during measurement is unavoidable. When the measurement object to which the magnetic sensor is fixed moves, the magnetic sensor itself also moves and changes the measurement point, so the magnetic field strength of the environmental magnetic field at the measurement point also changes. In addition, an induced magnetic field is generated by movement in the environmental magnetic field. Accordingly, since the environmental magnetic field and the induction magnetic field that can be changed by movement are measured by the magnetic sensor, the magnetic field component generated from the measurement target cannot be accurately evaluated.
　特許文献１に記載の発明は、地磁気を測定対象とした携帯端末において、地磁気センサーの検出データの変化が、端末移動によるものか外部ノイズによるものかを、加速度センサーの検出データ、ジャイロスコープの検出データに基づき判断する。同発明においては、所定値以上の移動が検出されたときも、地磁気センサーの検出データには、地磁気センサーの移動によって変化し得る環境磁場及び誘導磁場が含まれたままである。
　特許文献２に記載の生体磁気計測装置にあっては、生体磁場測定と前後して、被験体に付着される発振コイルからの磁場を測定して被験体の動きを検出し、被験体が動いたときの生体磁場データを破棄する。 In the invention described in Patent Document 1, in a portable terminal whose measurement target is geomagnetism, whether the change in detection data of the geomagnetic sensor is due to movement of the terminal or external noise, detection data of the acceleration sensor, detection of the gyroscope Judgment based on data. In the present invention, even when a movement of a predetermined value or more is detected, the detection data of the geomagnetic sensor still includes the environmental magnetic field and the induction magnetic field that can be changed by the movement of the geomagnetic sensor.
In the biomagnetic measurement device described in Patent Document 2, before and after the biomagnetic field measurement, the magnetic field from the oscillation coil attached to the subject is measured to detect the movement of the subject, and the subject moves. Discard the biomagnetic field data.
特開２０１５－２９２３６号公報Japanese Patent Laid-Open No. 2015-29236 特開平９－１７３３１３号公報JP-A-9-173313
　以上の従来技術にあっては、磁気センサーの移動によって変化し得る環境磁場や誘導磁場を、当該磁気センサーの測定信号から除くことはなかった。
　しかしながら、磁気センサーの移動によって変化し得る環境磁場や誘導磁場が測定信号に含まれていると、測定対象物から発生する磁場成分を正確に評価することはできない。特に生体磁気測定においては、測定対象物から発生する磁場成分は非常に微弱であり、影響が大きい。
　したがって、測定対象物が動き得る場合、特許文献２に記載のように測定対象物に動きがあった場合の測定データを破棄するほかなかった。
　測定対象物が動かないように拘束する場合、測定対象物が人その他の生物である場合は、その生物に対する負担が大きく、また完全に動かないようにすることは困難であるという問題がある。 In the above prior art, the environmental magnetic field and the induction magnetic field that can be changed by the movement of the magnetic sensor are not excluded from the measurement signal of the magnetic sensor.
However, if the measurement signal includes an environmental magnetic field or an induction magnetic field that can be changed by the movement of the magnetic sensor, the magnetic field component generated from the measurement object cannot be accurately evaluated. Particularly in biomagnetism measurement, the magnetic field component generated from the measurement object is very weak and greatly affected.
Therefore, when the measurement object can move, the measurement data when the measurement object moves as described in Patent Document 2 must be discarded.
When the measurement object is restrained so as not to move, there is a problem that when the measurement object is a human or other organism, the burden on the organism is large and it is difficult to prevent the measurement object from moving completely.
　本発明は以上の従来技術における問題に鑑みてなされたものであって、測定対象物に固定した磁気センサーにより当該測定対象物から発生する磁場を測定する構成において、測定対象物を拘束することなく、測定対象物及び磁気センサーの移動中の当該磁気センサーによる測定磁場信号に基づく測定も含めて、測定対象物から発生する磁場成分を精度よく測定することを課題とする。 The present invention has been made in view of the above problems in the prior art, and in a configuration in which a magnetic field generated from a measurement object is measured by a magnetic sensor fixed to the measurement object, the measurement object is not restrained. It is an object to accurately measure a magnetic field component generated from a measurement object, including measurement based on a measurement magnetic field signal by the magnetic sensor during movement of the measurement object and the magnetic sensor.
　以上の課題を解決するための請求項１記載の発明は、測定対象物に対する位置が固定されるように当該測定対象物に装着可能な磁場測定ユニットであって、測定対象物からの磁場を測定する測定磁気センサーと、当該磁場測定ユニットの運動を検出する運動検出センサーとを一体に有した磁場測定ユニットである。 The invention according to claim 1 for solving the above-described problem is a magnetic field measurement unit that can be attached to a measurement object so that the position with respect to the measurement object is fixed, and measures a magnetic field from the measurement object. And a motion detection sensor that detects the motion of the magnetic field measurement unit.
　請求項２記載の発明は、前記測定磁気センサーは、測定対象物からの磁場分布を測定する請求項１に記載の磁場測定ユニットである。 The invention according to claim 2 is the magnetic field measurement unit according to claim 1, wherein the measurement magnetic sensor measures a magnetic field distribution from a measurement object.
　請求項３記載の発明は、前記測定磁気センサーと、前記運動検出センサーとが、同一半導体基板上に集積されるか又は同一回路基板上に実装されて一体化された請求項１又は請求項２に記載の磁場測定ユニットである。 According to a third aspect of the present invention, the measurement magnetic sensor and the motion detection sensor are integrated on the same semiconductor substrate or mounted and integrated on the same circuit substrate. It is a magnetic field measurement unit as described in above.
　請求項４記載の発明は、請求項１から請求項３のうちいずれか一に記載の磁場測定ユニットと、
当該磁場測定ユニットが装着された測定対象物を含有する空間の環境磁場を測定する環境磁気センサーと、を備える磁場測定システムである。 The invention according to claim 4 is the magnetic field measurement unit according to any one of claims 1 to 3,
A magnetic field measurement system comprising: an environmental magnetic sensor that measures an environmental magnetic field in a space containing a measurement object on which the magnetic field measurement unit is mounted.
　請求項５記載の発明は、前記測定磁気センサーによる測定磁場信号と、前記運動検出センサーによる運動検出信号と、前記環境磁気センサーによる環境磁場信号とに基づき、測定値を算出する演算装置を備え、
前記演算装置は、前記測定磁場信号の測定時の前記測定磁気センサーの位置と移動速度に応じた当該位置における環境磁場と誘導磁場を前記運動検出信号及び前記環境磁場信号に基づき推算し、同推算に係る環境磁場と誘導磁場を当該測定磁場信号から差し引いて測定値とする請求項４に記載の磁場測定システムである。 The invention according to claim 5 includes an arithmetic unit that calculates a measurement value based on a measurement magnetic field signal from the measurement magnetic sensor, a motion detection signal from the motion detection sensor, and an environmental magnetic field signal from the environmental magnetic sensor,
The arithmetic device estimates an environmental magnetic field and an induced magnetic field at the position according to the position and moving speed of the measurement magnetic sensor at the time of measurement of the measurement magnetic field signal based on the motion detection signal and the environmental magnetic field signal. The magnetic field measurement system according to claim 4, wherein the environmental magnetic field and the induction magnetic field are subtracted from the measurement magnetic field signal to obtain a measurement value.
　請求項６記載の発明は、前記測定磁気センサーによる測定磁場信号と、前記運動検出センサーによる運動検出信号と、前記環境磁気センサーによる環境磁場信号とに基づき、測定値を算出する演算装置を備え、
前記演算装置は、
前記測定磁気センサーから前記測定磁場信号を取得する第１ステップと、
前記運動検出センサーから前記運動検出信号を取得する第２ステップと、
前記環境磁気センサーから前記環境磁場信号を取得する第３ステップと、
前記第３ステップにおいて取得した前記環境磁場信号と、前記第２ステップにおいて取得した前記運動検出信号とに基づいて、前記第１ステップにおいて取得した前記測定磁場信号を補正して測定値とする第４ステップと、を実行可能にされた請求項４に記載の磁場測定システムである。 The invention according to claim 6 includes an arithmetic unit that calculates a measurement value based on a measurement magnetic field signal from the measurement magnetic sensor, a motion detection signal from the motion detection sensor, and an environmental magnetic field signal from the environmental magnetic sensor,
The arithmetic unit is:
A first step of obtaining the measurement magnetic field signal from the measurement magnetic sensor;
A second step of obtaining the motion detection signal from the motion detection sensor;
A third step of acquiring the environmental magnetic field signal from the environmental magnetic sensor;
Based on the environmental magnetic field signal acquired in the third step and the motion detection signal acquired in the second step, the measurement magnetic field signal acquired in the first step is corrected to be a measurement value. 5. The magnetic field measurement system according to claim 4, wherein the step is executable.
　請求項７記載の発明は、前記第１ステップにおける前記測定磁場信号の取得時の前記測定磁気センサーの位置を、前記第２ステップにおいて取得した前記運動検出信号に基づき算出する第５ステップと、
前記第５ステップにおいて算出した位置における環境磁場を、前記第３ステップにおいて取得した前記環境磁場信号に基づき推算する第６ステップと、
前記第６ステップにおいて推算した環境磁場を、前記第１ステップにおいて取得した前記測定磁場信号から差し引く第７ステップと、が前記第４ステップに含まれる請求項６に記載の磁場測定システムである。 The invention according to claim 7 is a fifth step of calculating a position of the measurement magnetic sensor at the time of acquisition of the measurement magnetic field signal in the first step based on the motion detection signal acquired in the second step;
A sixth step of estimating the environmental magnetic field at the position calculated in the fifth step based on the environmental magnetic field signal acquired in the third step;
The magnetic field measurement system according to claim 6, wherein the fourth step includes a seventh step of subtracting the environmental magnetic field estimated in the sixth step from the measurement magnetic field signal acquired in the first step.
　請求項８記載の発明は、前記第１ステップにおける前記測定磁場信号の取得時の前記測定磁気センサーの位置及び移動速度を、前記第２ステップにおいて取得した前記運動検出信号に基づき算出する第８ステップと、
前記第８ステップにおいて算出した位置における環境磁場を、前記第３ステップにおいて取得した前記環境磁場信号に基づき推算する第９ステップと、
前記第８ステップにおいて算出した位置における誘導磁場を、前記第３ステップにおいて取得した前記環境磁場信号と、前記第８ステップにおいて算出した移動速度とに基づき推算する第１０ステップと、
前記第９ステップにおいて推算した環境磁場と、前記第１０ステップにおいて推算した誘導磁場とを、前記第１ステップにおいて取得した前記測定磁場信号から差し引く第１１ステップと、が前記第４ステップに含まれる請求項６に記載の磁場測定システムである。 According to an eighth aspect of the present invention, an eighth step of calculating a position and a moving speed of the measurement magnetic sensor at the time of acquisition of the measurement magnetic field signal in the first step based on the motion detection signal acquired in the second step. When,
A ninth step of estimating the environmental magnetic field at the position calculated in the eighth step based on the environmental magnetic field signal acquired in the third step;
A tenth step of estimating the induced magnetic field at the position calculated in the eighth step based on the environmental magnetic field signal acquired in the third step and the moving speed calculated in the eighth step;
The eleventh step of subtracting the ambient magnetic field estimated in the ninth step and the induced magnetic field estimated in the tenth step from the measured magnetic field signal acquired in the first step is included in the fourth step. Item 7. The magnetic field measurement system according to Item 6.
　本発明によれば、測定対象物に固定した磁気センサーにより当該測定対象物から発生する磁場を測定する構成において、測定対象物を拘束することなく、測定対象物及び磁気センサーの移動中の当該磁気センサーによる測定磁場信号に基づく測定も含めて、測定対象物から発生する磁場成分を精度よく測定することができる。 According to the present invention, in the configuration in which the magnetic field generated from the measurement object is measured by the magnetic sensor fixed to the measurement object, the measurement object and the magnetism during movement of the magnetic sensor are not restrained. The magnetic field component generated from the measurement object can be accurately measured, including the measurement based on the measurement magnetic field signal from the sensor.
本発明の一実施形態に係る磁場分布測定システムを示す斜視図である。1 is a perspective view showing a magnetic field distribution measurement system according to an embodiment of the present invention. 本発明の一実施形態に係る磁場分布測定システムを示す平面模式図である。It is a plane schematic diagram which shows the magnetic field distribution measurement system which concerns on one Embodiment of this invention. 本発明の一実施形態に係る磁場分布測定システムを示す平面模式図であり、図２とは環境磁気センサーの設置数が異なる。FIG. 3 is a schematic plan view showing a magnetic field distribution measurement system according to an embodiment of the present invention, which differs from FIG. 2 in the number of installed environmental magnetic sensors. 本発明の一実施形態に係る磁場分布測定システムを示す平面模式図であり、図２及び図３とは環境磁気センサーの設置数が異なる。FIG. 4 is a schematic plan view showing a magnetic field distribution measurement system according to an embodiment of the present invention, which is different from FIGS. 2 and 3 in the number of installed environmental magnetic sensors. 本発明の一実施形態に係る磁場分布測定システムを示す平面模式図である。It is a plane schematic diagram which shows the magnetic field distribution measurement system which concerns on one Embodiment of this invention. 本発明の一実施形態に係る磁場分布測定システムにおける演算内容を示すフローチャートである。It is a flowchart which shows the calculation content in the magnetic field distribution measurement system which concerns on one Embodiment of this invention. サブルーチン（第４ステップ）の内容を示すフローチャートであり、移動速度が無い場合を示す。It is a flowchart which shows the content of a subroutine (4th step), and shows the case where there is no moving speed. サブルーチン（第４ステップ）の内容を示すフローチャートであり、移動速度が有る場合を示す。It is a flowchart which shows the content of a subroutine (4th step), and shows the case where there exists a moving speed. 磁気シールド対策無しの測定空間を示す平面模式図である。It is a plane schematic diagram which shows the measurement space without a magnetic shield countermeasure. パッシブ磁気シールドを設けた測定空間を示す平面模式図である。It is a plane schematic diagram which shows the measurement space which provided the passive magnetic shield. アクティブ磁気シールドを設けた測定空間を示す平面模式図である。It is a plane schematic diagram which shows the measurement space which provided the active magnetic shield.
　以下に本発明の一実施形態につき図面を参照して説明する。以下は本発明の一実施形態であって本発明を限定するものではない。
　図１に本実施形態の磁場分布測定システムの構成を示す。本実施形態の磁場分布測定システム１は、磁場分布測定ユニット１０と、環境磁気センサー２０と、演算装置３０と備える。人体（被験者）２の頭部２ａを測定対象物とする場合を例とする。測定対象物を含有する空間３における上下方向の座標をＺとし、Ｚ軸に垂直で互いに垂直な２軸をＸ，Ｙとする。図２にＸＹ平面の模式図を示す。
　磁場分布測定ユニット１０は、頭部２ａからの磁場分布を測定する測定磁気センサー１１と、磁場測定ユニット１０の運動を検出する運動検出センサー１２とを一体に有する。測定磁気センサー１１は、複数のセンサー素子を２次元又は３次元に配列させたセンサーアレイモジュールを含み、頭部２ａの表面に沿った２次元、又は同２次元面に垂直な軸を加えた３次元の磁場分布を測定可能である。例えば、センサー素子としてトンネル磁気抵抗素子を適用することで実施可能である。なお、図面上は測定磁気センサー１１を簡素に示しており、近接する頭部２ａの表面に各センサー素子が対向するように配置したり、センサーアレイが頭部２ａの表面の測定対象領域を覆うように配置したりする構成が適宜に設計される。演算装置３０と、磁場分布測定ユニット１０及び環境磁気センサー２０との通信接続は、有線又は無線により行われる。被験者２の負担を軽減するために磁場分布測定ユニット１０は無線接続とすることが好ましい。 An embodiment of the present invention will be described below with reference to the drawings. The following is one embodiment of the present invention and does not limit the present invention.
FIG. 1 shows the configuration of the magnetic field distribution measurement system of this embodiment. The magnetic field distribution measurement system 1 according to this embodiment includes a magnetic field distribution measurement unit 10, an environmental magnetic sensor 20, and an arithmetic device 30. The case where the measurement object is the head 2a of the human body (subject) 2 is taken as an example. The vertical coordinate in the space 3 containing the measurement object is Z, and the two axes perpendicular to the Z axis and perpendicular to each other are X and Y. FIG. 2 shows a schematic diagram of the XY plane.
The magnetic field distribution measurement unit 10 integrally includes a measurement magnetic sensor 11 that measures the magnetic field distribution from the head 2 a and a motion detection sensor 12 that detects the motion of the magnetic field measurement unit 10. The measurement magnetic sensor 11 includes a sensor array module in which a plurality of sensor elements are arranged two-dimensionally or three-dimensionally, and is a two-dimensional configuration along the surface of the head 2a or a 3D axis that is perpendicular to the two-dimensional plane. Dimensional magnetic field distribution can be measured. For example, it can be implemented by applying a tunnel magnetoresistive element as the sensor element. In the drawing, the measurement magnetic sensor 11 is simply shown, and each sensor element is arranged so as to face the surface of the adjacent head 2a, or the sensor array covers the measurement target region on the surface of the head 2a. The arrangement to be arranged in this way is designed as appropriate. Communication connection between the arithmetic unit 30 and the magnetic field distribution measurement unit 10 and the environmental magnetic sensor 20 is performed by wire or wirelessly. In order to reduce the burden on the subject 2, the magnetic field distribution measurement unit 10 is preferably wirelessly connected.
　磁場分布測定ユニット１０は、頭部２ａに対する位置が固定されるように頭部２ａに装着可能である。図１に示すように、磁場分布測定ユニット１０を頭部２ａに装着して頭部２ａから発生する磁場を測定する。 The magnetic field distribution measurement unit 10 can be mounted on the head 2a so that the position with respect to the head 2a is fixed. As shown in FIG. 1, the magnetic field distribution measurement unit 10 is attached to the head 2a to measure the magnetic field generated from the head 2a.
　運動検出センサー１２としては、現在位置と移動速度が算出可能なファクターを検出可能であれば足りる。ここでは加速度センサーを適用する。３軸方向の移動があり得るので、３軸方向の加速度が検出できるように加速度センサーが設けられる。磁場分布測定ユニット１０を既知の座標に配置し、演算装置３０に対してその座標を原点座標として記憶させるとともに、原点座標からのＸＹＺ方向の各移動量をゼロにセットする。演算装置３０は、加速度センサーの出力信号に基づき、移動後の現在位置と移動速度を演算する。
　運動検出センサー１２は、測定磁気センサー１１の現在位置と移動速度を認識するために設けられる。そのため、運動検出センサー１２は、測定磁気センサー１１と一体にされ、できるだけ両者を近接して設けることが好ましい。測定磁気センサー１１と、運動検出センサー１２とが、同一半導体基板上に集積されたモノシリック半導体チップを構成して実施するとよい。また、測定磁気センサー１１を構成した半導体チップと、運動検出センサー１２を構成した半導体チップとを、同一回路基板上に互いに近接させて実装した構成を実施してもよい。 It is sufficient for the motion detection sensor 12 to be able to detect a factor capable of calculating the current position and the moving speed. Here, an acceleration sensor is applied. Since there is a possibility of movement in the triaxial direction, an acceleration sensor is provided so that acceleration in the triaxial direction can be detected. The magnetic field distribution measurement unit 10 is arranged at a known coordinate, the coordinate is stored as the origin coordinate in the arithmetic unit 30, and each movement amount in the XYZ directions from the origin coordinate is set to zero. The calculation device 30 calculates the current position and movement speed after movement based on the output signal of the acceleration sensor.
The motion detection sensor 12 is provided for recognizing the current position and the moving speed of the measurement magnetic sensor 11. Therefore, it is preferable that the motion detection sensor 12 is integrated with the measurement magnetic sensor 11 and is provided as close as possible. The measurement magnetic sensor 11 and the motion detection sensor 12 may be implemented by constituting a monolithic semiconductor chip integrated on the same semiconductor substrate. Further, a configuration may be implemented in which the semiconductor chip constituting the measurement magnetic sensor 11 and the semiconductor chip constituting the motion detection sensor 12 are mounted close to each other on the same circuit board.
　環境磁気センサー２０は、空間３の環境磁場Ｈｅを測定するためのものであり、空間３内に一つ又は複数が設置される。演算装置３０は、測定磁気センサー１１による測定磁場信号と、運動検出センサー１２による運動検出信号と、環境磁気センサー２０による環境磁場信号とに基づき、測定値を算出する。本実施形態では、脳磁図に相当する磁場分布データを算出する。 The environmental magnetic sensor 20 is for measuring the environmental magnetic field He in the space 3, and one or more are installed in the space 3. The computing device 30 calculates a measurement value based on the measurement magnetic field signal from the measurement magnetic sensor 11, the motion detection signal from the motion detection sensor 12, and the environmental magnetic field signal from the environmental magnetic sensor 20. In this embodiment, magnetic field distribution data corresponding to the magnetoencephalogram is calculated.
　空間３は、部屋内の空間とされる。空間３からの被験者２の逸脱、空間３への他者及び他の物の侵入を防ぐためである。空間３内の隅などに環境磁気センサー２０が設置され、環境磁気センサー２０は空間３の環境磁場（主には地磁気）を測定する。空間３の環境磁場分布を精度良く測定するために、環境磁気センサー２０を１個（図２）、２個（図３）、４個（図４）と配置し、さらにＺ方向にも２以上配置し、空間３の環境磁場を空間座標ＸＹＺを有した分布として取得することも可能である。環境磁場の均一性が高い空間３を確保できれば、環境磁気センサー２０を１個（図２）とし、空間３内のいずれの位置でも環境磁気センサー２０が測定した磁場強度と同じであると推定して処理して問題ない。環境磁気センサー２０を複数設ける場合、２つの環境磁気センサー２０間の環境磁場分布は線形的に変化すると推定して補間処理することができる。したがって、環境磁気センサー２０の数を増やすほど精度は上がるが、コストも上がる。空間３の環境磁場の均一性を考慮して環境磁気センサー２０の設置数を決定するとよい。 Space 3 is a space in the room. This is to prevent the departure of the subject 2 from the space 3 and the intrusion of others and other objects into the space 3. An environmental magnetic sensor 20 is installed at a corner or the like in the space 3, and the environmental magnetic sensor 20 measures an environmental magnetic field (mainly geomagnetism) in the space 3. In order to measure the environmental magnetic field distribution in the space 3 with high accuracy, one (Fig. 2), two (Fig. 3), and four (Fig. 4) environmental magnetic sensors 20 are arranged, and more than two in the Z direction. It is also possible to obtain the environment magnetic field in the space 3 as a distribution having the space coordinates XYZ. If the space 3 with high uniformity of the environmental magnetic field can be secured, the environmental magnetic sensor 20 is assumed to be the same as the magnetic field intensity measured by the environmental magnetic sensor 20 at any position in the space 3 (FIG. 2). There is no problem with processing. When a plurality of environmental magnetic sensors 20 are provided, the environmental magnetic field distribution between the two environmental magnetic sensors 20 can be estimated to be linearly changed and subjected to interpolation processing. Therefore, the accuracy increases as the number of environmental magnetic sensors 20 increases, but the cost also increases. The number of environmental magnetic sensors 20 may be determined in consideration of the uniformity of the environmental magnetic field in the space 3.
　図５において、異なる２つの測定点Ｓ１，Ｓ２における、移動速度ベクトル、頭部２ａ生体磁場、環境磁場、誘導磁場を、それぞれ順にｖ１，Ｈｍ１，Ｈｅ１，Ｈｉ１，ｖ２，Ｈｍ２，Ｈｅ２，Ｈｉ２とする。
　もし頭部２ａが動いていなければ、環境磁気センサー２０の環境磁場信号から推定される測定点（Ｓ１，Ｓ２）での環境磁場を、測定磁気センサー１１が出力する測定磁場信号から差し引くことで頭部２ａに由来する磁場分布を取得することが可能である。頭部２ａが動いていない状況は、例えば測定点Ｓ１においてｖ１がゼロである状況である。この場合、ｖ１がゼロであるため、誘導磁場Ｈｉ１もゼロとなり測定点Ｓ１での環境磁場Ｈｅ１を測定磁気センサー１１が出力する測定磁場信号から差し引けばよいからである。
　この場合、演算装置３０は図６に示すように、まず、測定磁気センサー１１から測定磁場信号を取得する第１ステップＳ１１と、運動検出センサー１２から運動検出信号を取得する第２ステップＳ１２と、環境磁気センサー２０から環境磁場信号を取得する第３ステップＳ１３とを同時性を以って実行する。
　次に、第３ステップＳ１３において取得した環境磁場信号と、第２ステップＳ１２において取得した運動検出信号とに基づいて、第１ステップＳ１１において取得した測定磁場信号を補正して測定値とする第４ステップＳ１４を実行する。
　この第４ステップＳ１４としては図７に示すように、第１ステップＳ１１における測定磁場信号の取得時の測定磁気センサー１１の位置（測定点（Ｓ１，Ｓ２））を、第２ステップＳ１２において取得した運動検出信号に基づき算出する第５ステップＳ１５と、第５ステップＳ１５において算出した位置（測定点（Ｓ１，Ｓ２））における環境磁場（Ｈｅ１，Ｈｅ２）を、第３ステップＳ１３において取得した環境磁場信号に基づき推算する第６ステップＳ１６と、第６ステップＳ１６において推算した環境磁場を、第１ステップＳ１１において取得した測定磁場信号から差し引く第７ステップＳ１７と、を実行する。 In FIG. 5, the moving velocity vector, the head 2a biomagnetic field, the environmental magnetic field, and the induction magnetic field at two different measurement points S1 and S2 are respectively set as v1, Hm1, He1, Hi1, v2, Hm2, He2, and Hi2. .
If the head 2a is not moving, the head is obtained by subtracting the environmental magnetic field at the measurement points (S1, S2) estimated from the environmental magnetic field signal of the environmental magnetic sensor 20 from the measurement magnetic field signal output from the measurement magnetic sensor 11. It is possible to acquire the magnetic field distribution derived from the part 2a. The situation where the head 2a is not moving is a situation where v1 is zero at the measurement point S1, for example. In this case, since v1 is zero, the induction magnetic field Hi1 is also zero, and the environmental magnetic field He1 at the measurement point S1 may be subtracted from the measurement magnetic field signal output from the measurement magnetic sensor 11.
In this case, as shown in FIG. 6, the arithmetic unit 30 firstly obtains a measurement magnetic field signal from the measurement magnetic sensor 11, a second step S <b> 12 obtains a motion detection signal from the motion detection sensor 12, and The third step S13 for acquiring the environmental magnetic field signal from the environmental magnetic sensor 20 is executed simultaneously.
Next, based on the environmental magnetic field signal acquired in the third step S13 and the motion detection signal acquired in the second step S12, the measurement magnetic field signal acquired in the first step S11 is corrected to be a measurement value. Step S14 is executed.
As this 4th step S14, as shown in FIG. 7, the position (measurement point (S1, S2)) of the measurement magnetic sensor 11 at the time of acquisition of the measurement magnetic field signal in the 1st step S11 was acquired in the 2nd step S12. The fifth step S15 calculated based on the motion detection signal and the environmental magnetic field signal (He1, He2) at the position (measurement point (S1, S2)) calculated in the fifth step S15 are acquired in the third step S13. The sixth step S16 estimated based on the above and the seventh step S17 for subtracting the environmental magnetic field estimated in the sixth step S16 from the measured magnetic field signal acquired in the first step S11 are executed.
　ただし、本実施形態では頭部２ａが動いている間も頭部２ａからの磁場の分布を取得することを想定している。測定磁気センサー１１は頭部２ａと固定されているので頭部２ａの動きと測定磁気センサー１１の動きはほぼ同一となる。図５に示すように空間３内の環境磁場中に測定磁気センサー１１が速度をもって動く場合（ｖ１，ｖ２がゼロでない場合）、センサー内に誘導電流、誘導磁場が発生し、測定磁気センサー１１の出力信号に重畳される。その誘導磁場は「環境磁場」と「移動速度」から換算することが可能である。
　なお、頭部２ａが動いたとしても同時に測定磁気センサー１１も同じ位置に同じ速度で動くため測定磁気センサーから見た頭部２ａは動いていないものと想定でき、頭部２ａからの磁場分布はずれることなくそのまま測定される。
　頭部２ａが右下の位置（測定点Ｓ１）に初期にいて左上（測定点Ｓ２）へ移動した場合、測定磁気センサー１１（例えばトンネル磁気抵抗素子などであり、磁気抵抗効果を使っているので１つの電気回路と考えることができる。）の導体を横切る環境磁場（Ｈｅ１，Ｈｅ２）は空間位置が変化することでその方向、大きさ、相対的な方向が変わる。測定磁気センサー１１の位置と移動速度は運動検出センサー１２の運動検出信号からわかる。頭部２ａの移動、従って測定磁気センサー１１及び運動検出センサー１２の移動に伴う環境磁場の変化量と移動速度とより誘導磁場（Ｈｉ１，Ｈｉ２）を計算することができる。
（測定磁気信号）＝（生体磁気信号）＋（環境磁場信号）＋（誘導磁場信号）となり、環境磁場と誘導磁場を測定磁気信号から引くことで頭部２ａからの生体磁場信号（Ｈｍ１，Ｈｍ２）のみを取り出すことができる。 However, in this embodiment, it is assumed that the magnetic field distribution from the head 2a is acquired even while the head 2a is moving. Since the measurement magnetic sensor 11 is fixed to the head 2a, the movement of the head 2a and the movement of the measurement magnetic sensor 11 are substantially the same. As shown in FIG. 5, when the measurement magnetic sensor 11 moves with speed in the environmental magnetic field in the space 3 (when v1 and v2 are not zero), an induced current and an induced magnetic field are generated in the sensor, and the measurement magnetic sensor 11 It is superimposed on the output signal. The induced magnetic field can be converted from the “environmental magnetic field” and the “movement speed”.
Even if the head 2a moves, the measurement magnetic sensor 11 simultaneously moves to the same position at the same speed, so it can be assumed that the head 2a viewed from the measurement magnetic sensor does not move, and the magnetic field distribution from the head 2a deviates. It is measured without any change.
When the head 2a initially moves to the lower right position (measurement point S1) and moves to the upper left (measurement point S2), the measurement magnetic sensor 11 (for example, a tunnel magnetoresistive element, etc., uses the magnetoresistive effect). The environmental magnetic field (He1, He2) traversing the conductor of the electrical circuit) can change its direction, size, and relative direction as the spatial position changes. The position and moving speed of the measurement magnetic sensor 11 can be known from the motion detection signal of the motion detection sensor 12. The induced magnetic field (Hi1, Hi2) can be calculated from the movement amount of the environmental magnetic field accompanying the movement of the head 2a, and hence the movement of the measurement magnetic sensor 11 and the movement detection sensor 12, and the moving speed.
(Measurement magnetic signal) = (Biomagnetic signal) + (Environmental magnetic field signal) + (Inductive magnetic field signal). By subtracting the environmental magnetic field and the induction magnetic field from the measurement magnetic signal, the biomagnetic field signals (Hm1, Hm2) from the head 2a are obtained. ) Only.
　以上の思想に基づき演算装置３０は図６に示すように、まず、測定磁気センサー１１から測定磁場信号を取得する第１ステップＳ１１と、運動検出センサー１２から運動検出信号を取得する第２ステップＳ１２と、環境磁気センサー２０から環境磁場信号を取得する第３ステップＳ１３とを同時性を以って実行する。
　次に、第３ステップＳ１３において取得した環境磁場信号と、第２ステップＳ１２において取得した運動検出信号とに基づいて、第１ステップＳ１１において取得した測定磁場信号を補正して測定値とする第４ステップＳ１４を実行する。
　この第４ステップＳ１４としては図８に示すように、第１ステップＳ１１における測定磁場信号の取得時の測定磁気センサー１１の位置（測定点（Ｓ１，Ｓ２））及び移動速度（ｖ１、ｖ２）を、第２ステップＳ１２において取得した運動検出信号に基づき算出する第８ステップＳ１８と、第８ステップＳ１８において算出した位置（測定点（Ｓ１，Ｓ２））における環境磁場（Ｈｅ１，Ｈｅ２）を、第３ステップＳ１３において取得した環境磁場信号に基づき推算する第９ステップＳ１９と、第８ステップＳ１８において算出した位置（測定点（Ｓ１，Ｓ２））における誘導磁場（Ｈｉ１，Ｈｉ２）を、第３ステップＳ１３において取得した環境磁場信号と、第８ステップＳ１８において算出した移動速度（ｖ１、ｖ２）とに基づき推算する第１０ステップＳ２０と、第９ステップＳ１９において推算した環境磁場と、第１０ステップＳ２０において推算した誘導磁場とを、第１ステップＳ１１において取得した測定磁場信号から差し引く第１１ステップＳ２１と、を実行する。 Based on the above idea, as shown in FIG. 6, the arithmetic unit 30 firstly obtains a measurement magnetic field signal from the measurement magnetic sensor 11, and a second step S <b> 12 obtains a movement detection signal from the movement detection sensor 12. And the third step S13 for acquiring the environmental magnetic field signal from the environmental magnetic sensor 20 is executed with the synchronization.
Next, based on the environmental magnetic field signal acquired in the third step S13 and the motion detection signal acquired in the second step S12, the measurement magnetic field signal acquired in the first step S11 is corrected to be a measurement value. Step S14 is executed.
As the fourth step S14, as shown in FIG. 8, the position (measurement points (S1, S2)) and the moving speed (v1, v2) of the measurement magnetic sensor 11 when the measurement magnetic field signal is acquired in the first step S11 are obtained. The eighth step S18 calculated based on the motion detection signal acquired in the second step S12, and the environmental magnetic field (He1, He2) at the position (measurement point (S1, S2)) calculated in the eighth step S18, In the third step S13, the induced magnetic field (Hi1, Hi2) at the position (measurement point (S1, S2)) calculated in the eighth step S18 and the ninth step S19 estimated based on the environmental magnetic field signal acquired in step S13 is obtained. Estimate based on the acquired environmental magnetic field signal and the moving speed (v1, v2) calculated in the eighth step S18. The tenth step S20 and the eleventh step S21 in which the environmental magnetic field estimated in the ninth step S19 and the induction magnetic field estimated in the tenth step S20 are subtracted from the measured magnetic field signal acquired in the first step S11 are executed. .
　頭部２ａが動くことにより発生する誘導磁場（Ｈｉ１，Ｈｉ２）は環境磁場（Ｈｅ１，Ｈｅ２）の強さと正の相関があるため、最初から環境磁場を低減することと組み合わせる又は組み合わせないことができる。その種類として、何もしない（図９Ａ）、パッシブ磁気シールド（図９Ｂ）、アクティブ磁気シールド（図９Ｃ）が考えられる。
　パッシブ磁気シールド（図９Ｂ）は、パーマロイ板のような軟磁性体の板４を周囲に敷き詰めた構成であり、地磁気などの環境磁場を低減できる。それでも完全に空間３内の環境磁場をゼロにすることは難しく、頭部２ａが動いた場合の誘導磁場もゼロにすることは難しい。そのため、本磁場分布測定システム１を使うことで環境磁場も誘導磁場もソフトウエア的に打ち消すことができる。
　アクティブ磁気シールド（図９Ｃ）は、アクティブ磁気シールド用の環境磁気センサー（本磁場分布測定システム１の環境磁気センサー２０と別に設置しても兼ねてもよい）の出力に応じて、空間３の周囲に配置した磁場発生装置（コイルなど）５を駆動することにより空間３の環境磁場を打ち消し低減する構成である。こちらも完全に空間３内の環境磁場をゼロにすること難しく、頭部２ａが動いた場合の誘導磁場もゼロにすることは難しい。そのため、本磁場分布測定システム１を使うことで環境磁場も誘導磁場もソフトウエア的に打ち消すことができる。 Since the induction magnetic field (Hi1, Hi2) generated by the movement of the head 2a has a positive correlation with the strength of the environmental magnetic field (He1, He2), it can be combined with or not combined with reducing the environmental magnetic field from the beginning. . As the types, nothing is done (FIG. 9A), passive magnetic shield (FIG. 9B), and active magnetic shield (FIG. 9C).
The passive magnetic shield (FIG. 9B) has a configuration in which a soft magnetic plate 4 such as a permalloy plate is spread around the periphery, and can reduce an environmental magnetic field such as geomagnetism. Nevertheless, it is difficult to completely reduce the environmental magnetic field in the space 3, and it is difficult to reduce the induced magnetic field when the head 2a moves. Therefore, by using this magnetic field distribution measurement system 1, both the environmental magnetic field and the induced magnetic field can be canceled by software.
The active magnetic shield (FIG. 9C) is arranged around the space 3 according to the output of the environmental magnetic sensor for active magnetic shield (which may be installed separately from the environmental magnetic sensor 20 of the magnetic field distribution measurement system 1). Is configured to cancel and reduce the environmental magnetic field in the space 3 by driving a magnetic field generator (coil or the like) 5 disposed in the space. Again, it is difficult to completely reduce the environmental magnetic field in the space 3, and it is difficult to reduce the induced magnetic field when the head 2a moves. Therefore, by using this magnetic field distribution measurement system 1, both the environmental magnetic field and the induced magnetic field can be canceled by software.
　以上の実施形態によれば、測定対象物（２ａ）に固定した磁気センサー（１１）により当該測定対象物から発生する磁場を測定する構成において、測定対象物を拘束することなく、測定対象物及び磁気センサーの移動中の当該磁気センサーによる測定磁場信号に基づく測定も含めて、測定対象物から発生する磁場成分を精度よく測定することができる。
　リアルタイムで算出し打ち消すことで測定対象物が動いていても良質な磁場分布信号を得ることができる。
　被験者２に対して測定中に動いてはいけないという束縛がなくなるので人物に対する負担が格段に減少する。また、束縛が聞かない動物などを測定対象とする場合にも測定対象に対する負担が少なく、良質な磁場分布信号を得ることができる。
　環境磁場を打ち消す技術（パッシブ磁気シールド、アクティブ磁気シールド）と組み合わせた場合でも測定位置の環境磁場を完全に除去することは難しく、本実施形態によれば残った環境磁場及び同環境磁場を起因とした誘導磁場を打ち消すことができるため、磁気測定の精度をさらに向上させることができる。 According to the above embodiment, in the configuration for measuring the magnetic field generated from the measurement object by the magnetic sensor (11) fixed to the measurement object (2a), the measurement object and the measurement object are not restrained. The magnetic field component generated from the measurement object can be accurately measured, including the measurement based on the measurement magnetic field signal by the magnetic sensor during movement of the magnetic sensor.
By calculating and canceling in real time, a good magnetic field distribution signal can be obtained even if the measurement object is moving.
Since the restraint that the subject 2 should not move during the measurement is eliminated, the burden on the person is greatly reduced. Further, even when an animal that is not bound is used as a measurement object, the burden on the measurement object is small, and a high-quality magnetic field distribution signal can be obtained.
Even when combined with a technology for canceling the environmental magnetic field (passive magnetic shield, active magnetic shield), it is difficult to completely remove the environmental magnetic field at the measurement position. According to the present embodiment, the remaining environmental magnetic field and the same environmental magnetic field are caused. Since the induced magnetic field can be canceled, the accuracy of magnetic measurement can be further improved.
　以上の実施形態に拘わらず、磁場分布を測定せず、１点における磁場強度を測定する構成においても、本発明の環境磁場及び誘導磁場を打ち消す技術が有効であることは言うまでもない。
　以上の実施形態にあっては、原点座標をセットするために磁場分布測定ユニット１０を既知の座標に配置した。原点座標をセットする方法は、これに限らず他の方法でもよい。例として次の方法を挙げることができる。
　頭部２ａに非装着の磁場分布測定ユニット１０を空間３内の任意の位置に置き、測定磁気センサー１１により環境磁場のみを検出する状態とする。環境磁気センサー２０は複数設けておく。かかる状態にて測定される測定磁気センサー１１及び複数の環境磁気センサー２０の磁場信号に基づき、測定磁気センサー１１の空間３内における位置座標を推定する。上述したように複数の環境磁気センサー２０に基づき空間３内の環境磁場分布を推定できるから、この推定した環境磁場分布を用いて、測定磁気センサー１１が測定する環境磁場から測定磁気センサー１１の位置を推定する（測定磁気センサー１１の位置からその位置の環境磁場を推定する過程と逆を行う。）。以上により推定した測定磁気センサー１１の空間３内における位置座標を原点座標とする。
　また他の方法としては、演算装置３０によって制御される位置検出用磁場発振器を複数用意し互いに離れた箇所に設置しておく。演算装置３０が、あるタイミングで位置検出用磁場発振器に所定の位置検出用磁場信号を発信させ、測定磁気センサー１１による測定磁場信号から位置検出用磁場信号を抽出し、位置検出用磁場信号の空間伝搬による時差や減衰率等を解析することで、各位置検出用磁場発振器から測定磁気センサー１１までの距離を推定する。以上による複数の位置検出用磁場発振器に対する測定磁気センサー１１の距離から、測定磁気センサー１１の空間３内における位置座標を特定し、特定した位置座標を原点座標とする。また、測定磁気センサー１１及び複数の環境磁気センサー２０によって同時に位置検出用磁場信号を検出させることによって、複数の環境磁気センサー２０に対する測定磁気センサー１１の相対位置で解析してもよい。 It goes without saying that the technology for canceling the environmental magnetic field and the induction magnetic field of the present invention is effective even in a configuration in which the magnetic field distribution is not measured and the magnetic field intensity at one point is measured regardless of the above embodiment.
In the above embodiment, the magnetic field distribution measurement unit 10 is arranged at known coordinates in order to set the origin coordinates. The method for setting the origin coordinates is not limited to this, and other methods may be used. The following method can be mentioned as an example.
The magnetic field distribution measurement unit 10 not attached to the head 2a is placed at an arbitrary position in the space 3, and only the environmental magnetic field is detected by the measurement magnetic sensor 11. A plurality of environmental magnetic sensors 20 are provided. Based on the magnetic field signals of the measurement magnetic sensor 11 and the plurality of environmental magnetic sensors 20 measured in this state, the position coordinates of the measurement magnetic sensor 11 in the space 3 are estimated. Since the environmental magnetic field distribution in the space 3 can be estimated based on the plurality of environmental magnetic sensors 20 as described above, the position of the measurement magnetic sensor 11 is determined from the environmental magnetic field measured by the measurement magnetic sensor 11 using the estimated environmental magnetic field distribution. (The reverse of the process of estimating the environmental magnetic field at the position from the position of the measurement magnetic sensor 11 is performed). The position coordinates in the space 3 of the measurement magnetic sensor 11 estimated as described above are set as the origin coordinates.
As another method, a plurality of position detecting magnetic field oscillators controlled by the arithmetic unit 30 are prepared and installed at locations separated from each other. The arithmetic unit 30 causes the position detection magnetic field oscillator to transmit a predetermined position detection magnetic field signal at a certain timing, extracts the position detection magnetic field signal from the measurement magnetic field signal by the measurement magnetic sensor 11, and the space of the position detection magnetic field signal The distance from each position detecting magnetic field oscillator to the measurement magnetic sensor 11 is estimated by analyzing the time difference and attenuation rate due to propagation. From the distance of the measurement magnetic sensor 11 to the plurality of position detection magnetic field oscillators as described above, the position coordinate in the space 3 of the measurement magnetic sensor 11 is specified, and the specified position coordinate is set as the origin coordinate. Further, the position magnetic field signal may be detected simultaneously by the measurement magnetic sensor 11 and the plurality of environmental magnetic sensors 20, so that the analysis may be performed at the relative position of the measurement magnetic sensor 11 with respect to the plurality of environmental magnetic sensors 20.
　本発明は、磁場測定ユニット及び磁場測定システムに利用することができる。 The present invention can be used for a magnetic field measurement unit and a magnetic field measurement system.
１     磁場分布測定システム
２     人体（被験者）
２ａ   頭部
３     空間
１０   磁場分布測定ユニット
１１   測定磁気センサー
１２   運動検出センサー
２０   環境磁気センサー
３０   演算装置 1 Magnetic field distribution measurement system 2 Human body (subject)
2a head 3 space 10 magnetic field distribution measurement unit 11 measurement magnetic sensor 12 motion detection sensor 20 environmental magnetic sensor 30 arithmetic unit

Claims (8)

  1. 測定対象物に対する位置が固定されるように当該測定対象物に装着可能な磁場測定ユニットであって、測定対象物からの磁場を測定する測定磁気センサーと、当該磁場測定ユニットの運動を検出する運動検出センサーとを一体に有した磁場測定ユニット。 A magnetic field measurement unit that can be attached to the measurement object so that the position with respect to the measurement object is fixed, a measurement magnetic sensor that measures the magnetic field from the measurement object, and a movement that detects the movement of the magnetic field measurement unit Magnetic field measurement unit with a detection sensor.
  2. 前記測定磁気センサーは、測定対象物からの磁場分布を測定する請求項１に記載の磁場測定ユニット。 The magnetic field measurement unit according to claim 1, wherein the measurement magnetic sensor measures a magnetic field distribution from a measurement object.
  3. 前記測定磁気センサーと、前記運動検出センサーとが、同一半導体基板上に集積されるか又は同一回路基板上に実装されて一体化された請求項１又は請求項２に記載の磁場測定ユニット。 The magnetic field measurement unit according to claim 1, wherein the measurement magnetic sensor and the motion detection sensor are integrated on the same semiconductor substrate or mounted and integrated on the same circuit board.
  4. 請求項１から請求項３のうちいずれか一に記載の磁場測定ユニットと、
    当該磁場測定ユニットが装着された測定対象物を含有する空間の環境磁場を測定する環境磁気センサーと、を備える磁場測定システム。     The magnetic field measurement unit according to any one of claims 1 to 3,
    A magnetic field measurement system comprising: an environmental magnetic sensor that measures an environmental magnetic field in a space containing a measurement object on which the magnetic field measurement unit is mounted.
  5. 前記測定磁気センサーによる測定磁場信号と、前記運動検出センサーによる運動検出信号と、前記環境磁気センサーによる環境磁場信号とに基づき、測定値を算出する演算装置を備え、
    前記演算装置は、前記測定磁場信号の測定時の前記測定磁気センサーの位置と移動速度に応じた当該位置における環境磁場と誘導磁場を前記運動検出信号及び前記環境磁場信号に基づき推算し、同推算に係る環境磁場と誘導磁場を当該測定磁場信号から差し引いて測定値とする請求項４に記載の磁場測定システム。     Based on the measurement magnetic field signal from the measurement magnetic sensor, the motion detection signal from the motion detection sensor, and the environmental magnetic field signal from the environmental magnetic sensor, an arithmetic unit that calculates a measurement value,
    The arithmetic device estimates an environmental magnetic field and an induced magnetic field at the position according to the position and moving speed of the measurement magnetic sensor at the time of measurement of the measurement magnetic field signal based on the motion detection signal and the environmental magnetic field signal. The magnetic field measurement system according to claim 4, wherein an environmental magnetic field and an induction magnetic field are subtracted from the measurement magnetic field signal to obtain a measurement value.
  6. 前記測定磁気センサーによる測定磁場信号と、前記運動検出センサーによる運動検出信号と、前記環境磁気センサーによる環境磁場信号とに基づき、測定値を算出する演算装置を備え、
    前記演算装置は、
    前記測定磁気センサーから前記測定磁場信号を取得する第１ステップと、
    前記運動検出センサーから前記運動検出信号を取得する第２ステップと、
    前記環境磁気センサーから前記環境磁場信号を取得する第３ステップと、
    前記第３ステップにおいて取得した前記環境磁場信号と、前記第２ステップにおいて取得した前記運動検出信号とに基づいて、前記第１ステップにおいて取得した前記測定磁場信号を補正して測定値とする第４ステップと、を実行可能にされた請求項４に記載の磁場測定システム。     Based on the measurement magnetic field signal from the measurement magnetic sensor, the motion detection signal from the motion detection sensor, and the environmental magnetic field signal from the environmental magnetic sensor, an arithmetic unit that calculates a measurement value,
    The arithmetic unit is:
    A first step of obtaining the measurement magnetic field signal from the measurement magnetic sensor;
    A second step of obtaining the motion detection signal from the motion detection sensor;
    A third step of acquiring the environmental magnetic field signal from the environmental magnetic sensor;
    Based on the environmental magnetic field signal acquired in the third step and the motion detection signal acquired in the second step, the measurement magnetic field signal acquired in the first step is corrected to be a measurement value. The magnetic field measurement system according to claim 4, wherein the step is executable.
  7. 前記第１ステップにおける前記測定磁場信号の取得時の前記測定磁気センサーの位置を、前記第２ステップにおいて取得した前記運動検出信号に基づき算出する第５ステップと、前記第５ステップにおいて算出した位置における環境磁場を、前記第３ステップにおいて取得した前記環境磁場信号に基づき推算する第６ステップと、
    前記第６ステップにおいて推算した環境磁場を、前記第１ステップにおいて取得した前記測定磁場信号から差し引く第７ステップと、が前記第４ステップに含まれる請求項６に記載の磁場測定システム。     A fifth step of calculating the position of the measurement magnetic sensor at the time of acquisition of the measurement magnetic field signal in the first step based on the motion detection signal acquired in the second step, and a position calculated in the fifth step A sixth step of estimating an environmental magnetic field based on the environmental magnetic field signal acquired in the third step;
    The magnetic field measurement system according to claim 6, wherein the fourth step includes a seventh step of subtracting the environmental magnetic field estimated in the sixth step from the measurement magnetic field signal acquired in the first step.
  8. 前記第１ステップにおける前記測定磁場信号の取得時の前記測定磁気センサーの位置及び移動速度を、前記第２ステップにおいて取得した前記運動検出信号に基づき算出する第８ステップと、
    前記第８ステップにおいて算出した位置における環境磁場を、前記第３ステップにおいて取得した前記環境磁場信号に基づき推算する第９ステップと、
    前記第８ステップにおいて算出した位置における誘導磁場を、前記第３ステップにおいて取得した前記環境磁場信号と、前記第８ステップにおいて算出した移動速度とに基づき推算する第１０ステップと、
    前記第９ステップにおいて推算した環境磁場と、前記第１０ステップにおいて推算した誘導磁場とを、前記第１ステップにおいて取得した前記測定磁場信号から差し引く第１１ステップと、が前記第４ステップに含まれる請求項６に記載の磁場測定システム。     An eighth step of calculating the position and moving speed of the measurement magnetic sensor at the time of acquisition of the measurement magnetic field signal in the first step based on the motion detection signal acquired in the second step;
    A ninth step of estimating the environmental magnetic field at the position calculated in the eighth step based on the environmental magnetic field signal acquired in the third step;
    A tenth step of estimating the induced magnetic field at the position calculated in the eighth step based on the environmental magnetic field signal acquired in the third step and the moving speed calculated in the eighth step;
    The eleventh step of subtracting the ambient magnetic field estimated in the ninth step and the induced magnetic field estimated in the tenth step from the measured magnetic field signal acquired in the first step is included in the fourth step. Item 7. The magnetic field measurement system according to Item 6.
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