JP2021124288A - Magnetic field measurement device, magnetic field measurement method, and magnetic field measurement program - Google Patents

Abstract

To more accurately measure a magnetic field.SOLUTION: A magnetic field measurement device includes: a magnetic sensor array which is constituted by three dimensionally arraying a plurality of magnetic sensor cells each having a magnetic sensor, an output unit, and a magnetic field generation unit, and capable of detecting input magnetic fields in three axes directions; a measurement data acquisition unit which acquires measurement data measured by the magnetic sensor array; a signal space separation unit which performs signal separation to a vector signal as a basic vector containing, as each signal component, a signal output by each of the magnetic sensors, when a magnetic field having a space distribution of an orthogonal function is detected by the magnetic sensor array, the space distribution of the input magnetic field being indicated by the measurement data; and a correction unit which corrects a sensor error of the magnetic sensor on the basis of a separation error at the signal separation of the space distribution of a calibration magnetic field generated by the magnetic field generation unit contained in at least one magnetic sensor cell in the plurality of magnetic sensor cells.SELECTED DRAWING: Figure 11

Description

The present invention relates to a magnetic field measuring device, a magnetic field measuring method, and a magnetic field measuring program.

Conventionally, a magnetic field measuring device for measuring a magnetic field emitted from a subject's head or chest using a sensor platform board in which a plurality of tunnel magneto-resistance (TMR) elements are arranged in an array is known ( For example, see Patent Document 1).
[Prior art literature]
[Patent Document]
[Patent Document 1] Japanese Unexamined Patent Publication No. 2012-152514

In the conventional magnetic field measuring device, a pair of magnetic detection elements are laminated in the magnetic field detection direction, and the magnitude of the measurement result between the pair of magnetic detection elements is the same for the disturbance magnetic field, while the measurement target magnetic field. On the other hand, the disturbance magnetic field was suppressed and the measurement target magnetic field was measured based on the principle that the magnitudes of the measurement results differed between the pair of magnetic detector elements. However, it is possible to measure the magnetic field with higher accuracy, for example, by measuring a weak biomagnetic field (referred to as "magnetocardiography") generated by the electrical activity of the heart to examine the state of the heart more precisely. desired.

In order to solve the above problems, in the first aspect of the present invention, a magnetic field measuring device is provided. The magnetic field measuring device has a curved surface shape curved in at least one direction, and each has a magnetic sensor, an output unit that outputs an output signal, and an input magnetic field detected by the magnetic sensor with a size corresponding to the output signal. A plurality of magnetic sensor cells having a magnetic field generator for generating a feedback magnetic field are arranged three-dimensionally so as to be arranged at lattice points included in a curved surface shape, and an input magnetic field in three axial directions can be detected. Magnetic sensor array may be provided. The magnetic field measuring device may include a measurement data acquisition unit that acquires measurement data measured by the magnetic sensor array. The magnetic field measuring device is a vector having signals output by each of the magnetic sensors as signal components when the spatial distribution of the input magnetic field indicated by the measurement data is detected by the magnetic sensor array when the magnetic field having the spatial distribution of the normal orthogonal function is detected. A signal space separation unit that separates signals using the signal as a base vector may be provided. The magnetic field measuring device determines the sensor error in the magnetic sensor based on the separation error when the spatial distribution of the calibration magnetic field generated from the magnetic field generator of at least one magnetic sensor cell among the plurality of magnetic sensor cells is signal-separated. It may be provided with a calibrator to calibrate.

The output unit may output an output signal corresponding to the feedback current that the magnetic field generation unit flows to generate the feedback magnetic field.

Each of the magnetic sensors includes a magnetoresistive element and two magnetoresistive plates arranged at both ends of the magnetoresistive element, and the magnetoresistive element may be arranged at a position sandwiched between the two magnetoresistive plates.

The magnetic field generator may include a magnetoresistive element and a feedback coil wound along the axial direction of the magnetic field to be detected by the magnetic sensor so as to surround the two magnetic focusing plates.

The calibrator may calibrate the sensor error in the magnetic sensor based on the respective separation errors when at least one magnetic sensor cell is sequentially switched.

The magnetic sensor array is configured by arranging a plurality of magnetic sensor cells three-dimensionally in a cross-sectional view arc shape, and the calibration unit sequentially switches at least one magnetic sensor cell over a plurality of magnetic sensor cells forming an inner arc. The sensor error in the magnetic sensor may be calibrated based on each separation error in.

The at least one magnetic sensor cell may further have a switching unit for switching whether the magnetic field generation unit generates a feedback magnetic field or a calibration magnetic field.

The signal space separation unit may use the position where the magnetic field generation unit of at least one magnetic sensor cell is arranged as the origin of the coordinates in the calculation when the spatial distribution of the calibration magnetic field is signal-separated.

The calibrator may calibrate the sensor error by changing the basis vector.

The calibrator may optimize the basis vector to minimize separation error.

The magnetic field measuring device may further include a synchronous detection unit that detects a calibration magnetic field, which is an AC magnetic field, using a signal having a frequency of the AC magnetic field.

The frequency of the AC magnetic field may be higher than the frequency band of the magnetic field to be measured.

In the second aspect of the present invention, a magnetic field measurement method is provided. The magnetic field measurement method has a curved surface shape that is curved in at least one direction, and each has a magnetic sensor, an output unit that outputs an output signal, and an input magnetic field detected by the magnetic sensor with a size corresponding to the output signal. A plurality of magnetic sensor cells having a magnetic field generator for generating a feedback magnetic field to be reduced are arranged three-dimensionally so as to be arranged at lattice points included in a curved surface shape, and an input magnetic field in three axial directions can be detected. It may be provided to acquire the measurement data measured by the magnetic sensor array. The magnetic field measurement method is a vector having signals output by each of the magnetic sensors as signal components when the spatial distribution of the input magnetic field indicated by the measurement data is detected by the magnetic sensor array when the magnetic field having the spatial distribution of the normal orthogonal function is detected. It may be provided to separate the signal with the signal as the base vector. The magnetic field measurement method may include generating a calibration magnetic field from a magnetic field generation unit included in at least one magnetic sensor cell among the plurality of magnetic sensor cells. The magnetic field measurement method may include calibrating the sensor error in the magnetic sensor based on the separation error when the spatial distribution of the calibration magnetic field is signal separated.

In the third aspect of the present invention, a magnetic field measurement program is provided. The magnetic field measurement program may be executed by a computer. The magnetic field measurement program has a curved surface shape in which the computer is curved in at least one direction, and each of them detects a magnetic sensor, an output unit that outputs an output signal, and a size corresponding to the output signal. A plurality of magnetic sensor cells having a magnetic field generator that generates a feedback magnetic field that reduces the input magnetic field are arranged three-dimensionally so as to be arranged at lattice points included in the curved shape, and the input magnetic field in the three axial directions is generated. It may function as a measurement data acquisition unit that acquires measurement data measured by a detectable magnetic sensor array. The magnetic field measurement program outputs each signal component of the magnetic sensor when the computer detects the spatial distribution of the input magnetic field indicated by the measurement data and the magnetic field having the spatial distribution of the normal orthogonal function with the magnetic sensor array. It may function as a signal space separation unit that separates the vector signal having as a base vector as a base vector. The magnetic field measurement program is based on the separation error when the computer signals the spatial distribution of the calibration magnetic field generated from the magnetic field generator of at least one magnetic sensor cell among the plurality of magnetic sensor cells. It may function as a calibrator to calibrate the sensor error.

In the fourth aspect of the present invention, a magnetic field measuring device is provided. Each magnetic field measuring device has a magnetic sensor, an output unit that outputs an output signal, and a magnetic field generator that generates a feedback magnetic field that reduces the input magnetic field detected by the magnetic sensor with a size corresponding to the output signal. A magnetic sensor array that is configured by arranging a plurality of magnetic sensor cells having a plurality of magnetic sensor cells in a three-dimensional manner and capable of detecting an input magnetic field in three axial directions may be provided. The magnetic field measuring device may include a measurement data acquisition unit that acquires measurement data measured by the magnetic sensor array. The magnetic field measuring device is a vector having signals output by each of the magnetic sensors as signal components when the spatial distribution of the input magnetic field indicated by the measurement data is detected by the magnetic sensor array when the magnetic field having the spatial distribution of the normal orthogonal function is detected. A signal space separation unit that separates signals using the signal as a base vector may be provided. The magnetic field measuring device determines the sensor error in the magnetic sensor based on the separation error when the spatial distribution of the calibration magnetic field generated from the magnetic field generator of at least one magnetic sensor cell among the plurality of magnetic sensor cells is signal-separated. It may be provided with a calibrator to calibrate.

The outline of the above invention does not list all the necessary features of the present invention. Sub-combinations of these feature groups can also be inventions.

The configuration of the magnetic field measuring device 10 according to this embodiment is shown. The configuration of the magnetic sensor unit 110 according to this embodiment is shown. The configuration of the magnetic sensor cell 220 in the magnetic sensor array 210 according to the present embodiment is shown. An example of the input / output characteristics of the magnetic sensor having the magnetoresistive element according to the present embodiment is shown. A configuration example of the sensor unit 300 according to this embodiment is shown. An example of the input / output characteristics of the sensor unit 300 according to the present embodiment is shown. A configuration example of the magnetic sensor 520 according to this embodiment is shown. The magnetic flux distribution when a feedback magnetic field is generated in the magnetic sensor 520 according to the present embodiment is shown. An arrangement example of a plurality of magnetic sensor cells 220 in the magnetic sensor array 210 according to the present embodiment is shown. The configuration of the sensor unit 300inside included in the inner magnetic sensor cell 220 in the magnetic sensor array 210 according to the present embodiment is shown. The configuration of the magnetic sensor array 210, the sensor data collection unit 230, and the sensor data processing unit 1100 according to the present embodiment is shown. The flow in which the magnetic field measuring device 10 according to this embodiment signals separates the spatial distribution of the magnetic field is shown. When the magnetic sensor array 210 is ideally constructed, the signal space separation operation using _{the ideal basis vector [AB] Ideal is geometrically shown.} When the magnetic sensor array 210 is made with sensor error, the signal space separation operation using _{the ideal basis vector [AB] Ideal is geometrically shown.} The flow in which the magnetic field measuring apparatus 10 according to this embodiment acquires the sensor array signal Φ (i, j, 1) for calibration is shown. The flow in which the magnetic field measuring apparatus 10 according to this embodiment calibrates is shown. When the magnetic sensor array 210 is made with sensor error, the signal space separation operation using _{the calibrated basis vector [AB] Calib is geometrically shown.} An example of a computer 2200 in which a plurality of aspects of the present invention may be embodied in whole or in part is shown.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the inventions that fall within the scope of the claims. Also, not all combinations of features described in the embodiments are essential to the means of solving the invention.

FIG. 1 shows the configuration of the magnetic field measuring device 10 according to the present embodiment. When measuring a target magnetic field using a magnetic sensor, the magnetic field measuring device 10 generates a calibration magnetic field from a magnetic field generating unit of at least one of a plurality of magnetic sensor cells in the magnetic sensor array, and the magnetic field measuring device 10 generates a calibration magnetic field. Calibration The error in the magnetic sensor is calibrated (calibrated) based on the measurement result of the magnetic field. In the present embodiment, a case where the magnetic field measuring device 10 is a magnetocardiographic measuring device for measuring a magnetocardiogram, which is a magnetic field generated by the electrical activity of the human heart, will be described as an example. However, it is not limited to this. The magnetic field measuring device 10 may be used for measuring the magnetocardiography of a living body other than a human being, or may be used for measuring a biomagnetic field other than the magnetocardiography such as a cerebral magnetic field. Further, the magnetic field measuring device 10 may be used for a magnetic particle inspection for detecting scratches on the surface and surface of a steel material or a welded portion.

The magnetic field measuring device 10 includes a main body 100 and an information processing unit 150. The main body 100 is a component for sensing the magnetocardiography of the subject, and has a magnetic sensor unit 110, a head 120, a drive unit 125, a base unit 130, and a pole unit 140.

The magnetic sensor unit 110 is arranged at a position toward the heart in the chest of the subject at the time of magnetocardiography measurement, and senses the magnetocardiography of the subject. The head 120 supports the magnetic sensor unit 110 and makes the magnetic sensor unit 110 face the subject when measuring the magnetocardiography. The drive unit 125 is provided between the magnetic sensor unit 110 and the head 120, and changes the orientation of the magnetic sensor unit 110 with respect to the head 120 when performing calibration. The drive unit 125 according to the present embodiment has a first actuator capable of rotating the magnetic sensor unit 110 360 degrees around the Z axis in the drawing, and an axis perpendicular to the Z axis (X axis in the state in the drawing). ) Is included, and the second actuator that rotates the magnetic sensor unit 110 is included, and the azimuth angle and the zenith angle of the magnetic sensor unit 110 are changed by using these. As shown as the drive unit 125 in the figure, the drive unit 125 has a Y-shape when viewed from the Y-axis direction in the figure, and the second actuator has the magnetic sensor unit 110 360 degrees centered on the X-axis in the figure. Can be rotated.

The base portion 130 is a base that supports other parts, and in the present embodiment, is a base on which the subject rides during magnetocardiography measurement. The pole portion 140 supports the head 120 at the height of the subject's chest. The pole portion 140 may be stretchable in the vertical direction so as to adjust the height of the magnetic sensor unit 110 to the height of the chest of the subject.

The information processing unit 150 is a component for processing the data measured by the main body 100 and outputting it by display, printing, or the like. The information processing unit 150 may be a computer such as a PC (personal computer), a tablet computer, a smartphone, a workstation, a server computer, or a general-purpose computer, or may be a computer system to which a plurality of computers are connected. Instead, the information processing unit 150 may be a dedicated computer designed for information processing of magnetic field measurement, or dedicated hardware realized by a dedicated circuit.

FIG. 2 shows the configuration of the magnetic sensor unit 110 according to the present embodiment. The magnetic sensor unit 110 includes a magnetic sensor array 210 and a sensor data acquisition unit 230. The magnetic sensor array 210 has a plurality of magnetic sensor cells 220 and can detect an input magnetic field in three axial directions. In this figure, in the magnetic sensor array 210, a plurality of magnetic sensor cells 220 (for example, 8 in the X direction, 8 in the Y direction, and 2 in the Z direction) in each of the X direction, the Y direction, and the Z direction, for a total of 128 The case where the magnetic sensor cells 220) are arranged is shown.

The sensor data collection unit 230 is electrically connected to a plurality of magnetic sensor cells 220 included in the magnetic sensor array 210 (not shown), and collects sensor data (detection signals) from the plurality of magnetic sensor cells 220 to provide information. It is supplied to the processing unit 150.

FIG. 3 shows the configuration of the magnetic sensor cell 220 in the magnetic sensor array 210 according to the present embodiment. Each of the plurality of magnetic sensor cells 220 has at least one sensor unit 300, each of which has a magnetoresistive element. In this figure, an example is a case where each of the plurality of magnetic sensor cells 220 has three sensor units 300x to z (collectively referred to as “sensor unit 300”) and the input magnetic field can be detected in the three axial directions. Shown as. However, none of the plurality of magnetic sensor cells 220 is limited to having three sensor units 300x to z, and if at least a part of the magnetic sensor array 210 can detect an input magnetic field in the three axial directions. good. At this time, as will be described later, when each spherical harmonic is spatially sampled by the magnetic sensor array 210, it is necessary to detect the dependence on the spatial frequency related to the angular momentum in the magnetic field. Therefore, it is preferable that the positions of the sensor units 300 in the magnetic sensor array 210 are arranged as evenly as possible at least in the azimuth angle direction and the zenith angle direction. For the same reason, it is preferable that the magnetic sensing axes of the sensors in the magnetic sensor array 210 are arranged at least as evenly as possible in the azimuth direction and the zenith angle direction. The sensor unit 300x is arranged along the X-axis direction and can detect the magnetic field in the X-axis direction. Further, the sensor unit 300y is arranged along the Y-axis direction and can detect the magnetic field in the Y-axis direction. Further, the sensor unit 300z is arranged along the Z-axis direction and can detect the magnetic field in the Z-axis direction. As shown by the enlarged view shown by the alternate long and short dash line in this figure, in the present embodiment, each sensor unit 300 has magnetic convergence plates arranged at both ends of the magnetoresistive element. Therefore, each sensor unit 300 clarifies the sampling points in space in each axial direction by sampling the spatial distribution of the magnetic field using the magnetoresistive element arranged at a narrow position sandwiched between the magnetic focusing plates. be able to. Details of the configuration of each sensor unit 300 will be described later.

The plurality of magnetic sensor cells 220 are arranged at equal intervals of Δx along the X-axis direction, Δy along the Y-axis direction, and Δz along the Z-axis direction. The position of each magnetic sensor cell 220 in the magnetic sensor array 210 is represented by a set [i, j, k] of a position i in the X direction, a position j in the Y direction, and a position k in the Z direction. Here, i is an integer satisfying 1 ≦ i ≦ Nx (Nx indicates the number of magnetic sensor cells 220 arranged in the X direction), and j is an integer satisfying 1 ≦ j ≦ Ny (Ny is the Y direction). (Indicates the number of magnetic sensor cells 220 arranged in), k is an integer satisfying 1 ≦ k ≦ Nz (Nz indicates the number of magnetic sensor cells 220 arranged in the Z direction). In the above description, a case where a plurality of magnetic sensor cells 220 are arranged at equal intervals along each axial direction is shown as an example. However, it is not limited to this. The plurality of magnetic sensor cells 220 may be arranged at different intervals in at least one of the X-axis direction, the Y-axis direction, and the Z-axis direction, for example.

In this figure, the three-axis directions of the magnetic fields detected by the sensor units 300x, 300y, and 300z and the three-dimensional directions in which the magnetic sensor cells 220 are arranged are the same directions. This makes it easy to grasp each component of the distribution of the measured magnetic field. Further, the three sensor units 300x, 300y, and 300z do not overlap each other when viewed from each of the three-dimensional directions in which the magnetic sensor cells 220 are arranged in each magnetic sensor cell 220, and are provided between the three sensor units 300. It is preferable that one end is provided on the gap side and the other end is extended in each of the three axial directions so as to be separated from the gap. As an example, in this figure, a gap is provided in the lower left corner of the magnetic sensor cell 220 when viewed from the front, and the sensor portions 300x, 300y, and 300z are provided so that one end is in contact with the gap and the other end is in contact with the gap. An example is shown in which the components are stretched in each of the X-axis, Y-axis, and Z-axis directions so as to be separated from the gap. In this figure, the sensor portions 300x, 300y, and 300z are arranged along three sides perpendicular to each other from one corner of the cubic magnetic sensor cell 220, and a gap is provided in the corner. However, the three-axis direction of the magnetic field to be detected and the three-dimensional direction in which the magnetic sensor cells 220 are arranged may be different. For example, instead of the X-axis, Y-axis, and Z-axis, the r-axis, θ-axis, and φ-axis of the polar coordinate system may be used as the three-axis directions of the magnetic field to be detected. Further, as the three-dimensional direction in which the magnetic sensor cells 220 are arranged, the r-axis, θ-axis, and φ-axis of the polar coordinate system may be used instead of the X-axis, Y-axis, and Z-axis. When the three-axis direction of the magnetic field to be detected and the three-dimensional direction in which the magnetic sensor cells 220 are arranged are different, the magnetism is not restricted by the arrangement of the sensor unit 300 in the magnetic sensor cell 220 or the arrangement direction of the magnetic sensor cells 220. The degree of freedom in designing the sensor array 210 can be increased. Further, the sensor units 300x, 300y, and 300z may be provided without providing a gap at the corner portion of the magnetic sensor cell 220. In this case, the magnetic sensor cell 220 can be made smaller, and therefore, the magnetic sensor array 210 having such a plurality of magnetic sensor cells 220 can be made smaller.

FIG. 4 shows an example of the input / output characteristics of the magnetic sensor having the magnetoresistive element according to the present embodiment. In this figure, the horizontal axis shows the magnitude B of the input magnetic field input to the magnetic sensor, and the vertical axis shows the magnitude V_xMR0 of the detection signal of the magnetic sensor. The magnetic sensor has, for example, a giant magneto-resistance (GMR) element or a tunnel magneto-resistance (TMR) element, and detects the magnitude of a predetermined uniaxial magnetic field. ..

Such a magnetic sensor has high magnetic sensitivity, which is the gradient of the detection signal V_xMR0 with respect to the input magnetic field B, and can detect a minute magnetic field of about 10 pT. On the other hand, in the magnetic sensor, for example, when the absolute value of the input magnetic field B is about 1 μT, the detection signal V_xMR0 is saturated, and the range in which the linearity of the input / output characteristics is good is narrow. Therefore, by adding a closed loop that generates a feedback magnetic field to such a magnetic sensor, the linearity of the magnetic sensor can be improved. Such a magnetic sensor will be described below.

FIG. 5 shows a configuration example of the sensor unit 300 according to the present embodiment. The sensor unit 300 is provided inside each of the plurality of magnetic sensor cells 220, and includes a magnetic sensor 520, a magnetic field generation unit 530, and an output unit 540. A part of the sensor unit 300, for example, an amplifier circuit 532 or the like may be provided on the sensor data collection unit 230 side instead of the magnetic sensor cell 220 side.

The magnetic sensor 520 has a magnetoresistive element such as a GMR element or a TMR element, similar to the magnetic sensor described with reference to FIG. Further, each of the magnetic sensors 520 includes a magnetoresistive element and two magnetoresistive plates arranged at both ends of the magnetoresistive element, and the magnetoresistive element is arranged at a position sandwiched between the two magnetoresistive plates. .. The magnetoresistive element of the magnetic sensor 520 increases the resistance value when a magnetic field in the + X direction is input, and decreases when a magnetic field in the -X direction is input, when the positive direction of the magnetic sensing axis is the + X direction. It may be formed to do so. That is, by observing the change in the resistance value of the magnetoresistive element possessed by the magnetic sensor 520, the magnitude of the magnetic field B input to the magnetic sensor 520 can be detected. For example, assuming that the magnetic sensitivity of the magnetic sensor 520 is S, the detection result of the magnetic sensor 520 with respect to the input magnetic field B can be calculated as S × B. As an example, the magnetic sensor 520 is connected to a power source or the like, and outputs a voltage drop according to a change in resistance value as a detection result of an input magnetic field. Details of the configuration of the magnetic sensor 520 will be described later.

The magnetic field generation unit 530 generates a feedback magnetic field having a size corresponding to the output signal output by the output unit 540 and reduces the input magnetic field detected by the magnetic sensor 520, and gives the feedback magnetic field to the magnetic sensor 520. For example, the magnetic field generation unit 530 generates a feedback magnetic field B_FB whose absolute value is substantially the same as the input magnetic field in the direction opposite to the magnetic field B input to the magnetic sensor 520, and operates so as to cancel the input magnetic field. The magnetic field generation unit 530 includes an amplifier circuit 532 and a feedback coil 534.

The amplifier circuit 532 outputs a current corresponding to the detection result of the input magnetic field of the magnetic sensor 520 as the feedback current I_FB. When the magnetoresistive element included in the magnetic sensor 520 is composed of a bridge circuit including at least one magnetoresistive element, the output of the bridge circuit is connected to the input terminal pair of the amplifier circuit 532, respectively. Then, the amplifier circuit 532 outputs a current corresponding to the output of the bridge circuit as a feedback current I_FB. The amplifier circuit 532 includes, for example, a transconductance amplifier, and outputs a feedback current I_FB corresponding to the output voltage of the magnetic sensor 520. For example, assuming that the voltage / current conversion coefficient of the amplifier circuit 532 is G, the feedback current I_FB can be calculated as G × S × B.

The feedback coil 534 generates a feedback magnetic field B_FB corresponding to the feedback current I_FB. The feedback coil 534 is wound along the axial direction of the magnetic field to be detected by the magnetic sensor 520 so as to surround the magnetoresistive element of the magnetic sensor 520 and the two magnetic focusing plates arranged at both ends of the magnetoresistive element. ing. It is desirable that the feedback coil 534 generate a uniform feedback magnetic field B_FB throughout the magnetic sensor 520. For example, assuming that the coil coefficient of the feedback coil 534 is β, the feedback magnetic field B_FB can be calculated as β × I_FB. Here, since the feedback magnetic field B_FB is generated in a direction that cancels the input magnetic field B, the magnetic field input to the magnetic sensor 520 is reduced to BB_FB. Therefore, the feedback current I_FB is expressed by the following equation.

When the equation (Equation 1) is solved for the feedback current I_FB, the value of the feedback current I_FB in the steady state of the sensor unit 300 can be calculated. Assuming that the magnetic sensitivity S of the magnetic sensor 520 and the voltage / current conversion coefficient G of the amplifier circuit 532 are sufficiently large, the following equation is calculated from the equation (Equation 1).

The output unit 540 outputs an output signal V_xMR corresponding to the feedback current I_FB that the magnetic field generation unit 530 flows to generate the feedback magnetic field B_FB. The output unit 540 has, for example, a resistance element having a resistance value R, and outputs a voltage drop caused by a feedback current I_FB flowing through the resistance element as an output signal V_xMR. In this case, the output signal V_xMR is calculated from the equation (Equation 2) as follows.

As described above, since the sensor unit 300 generates a feedback magnetic field that reduces the magnetic field input from the outside, the magnetic field that is substantially input to the magnetic sensor 520 is reduced. As a result, the sensor unit 300 uses, for example, a magnetoresistive element having the non-linearity shown in FIG. 4 as the magnetic sensor 520 and having a narrow operating magnetic field range, even if the absolute value of the input magnetic field B exceeds 1 μT. , It is possible to prevent the detection signal V_xMR from being saturated. The input / output characteristics of such a sensor unit 300 will be described below.

FIG. 6 shows an example of the input / output characteristics of the sensor unit 300 according to the present embodiment. In this figure, the horizontal axis shows the magnitude B of the input magnetic field input to the sensor unit 300, and the vertical axis shows the magnitude V_xMR of the detection signal of the sensor unit 300. The sensor unit 300 has high magnetic sensitivity and can detect a minute magnetic field of about 10 pT. Further, the sensor unit 300 can maintain good linearity of the detection signal V_xMR even if the absolute value of the input magnetic field B exceeds 100 μT, for example.

That is, in the sensor unit 300 according to the present embodiment, the detection result for the input magnetic field B has linearity in a predetermined range of the input magnetic field B, for example, the absolute value of the input magnetic field B is several hundred μT or less. It is configured as follows. By using such a sensor unit 300, a weak magnetic signal such as a magnetocardiographic signal can be easily detected.

FIG. 7 shows a configuration example of the magnetic sensor 520 according to the present embodiment. In this figure, the magnetic sensor 520 has a magnetoresistive element 710 and magnetic focusing plates 720 and 730 arranged at both ends of the magnetoresistive element 710. The magnetic focusing plates 720 and 730 are arranged at both ends of the magnetoresistive element 710 so as to sandwich the magnetoresistive element 710. In this figure, the magnetic convergence plate 720 is provided on the negative side of the magnetoresistive element 710 along the magnetic sensing axis, and the magnetic convergence plate 730 is provided on the positive side of the magnetoresistive element 710 along the magnetic sensing axis. There is. Here, the magnetically sensitive axis may be along the direction of magnetization fixed in the magnetization fixing layer forming the magnetoresistive element 710. Further, when a magnetic field is input from the negative side to the positive side of the magnetic sensing shaft, the resistance of the magnetoresistive element 710 may increase or decrease. The magnetic focusing plates 720 and 730 are formed of a material having a high magnetic permeability such as permalloy. When the magnetic sensor 520 is configured as shown in this figure, the feedback coil 534 surrounds the cross section of the magnetoresistive element 710 and the magnetic focusing plates 720 and 730 arranged at both ends of the magnetoresistive element 710. The magnetic sensor 520 is wound along the axial direction of the magnetic field to be detected. Further, when the magnetic sensor 520 has a plurality of magnetoresistive elements 710 in one magnetic sensor 520, the magnetic sensor 520 may have a plurality of sets including the magnetoresistive element and the magnetic focusing plates arranged at both ends thereof. In that case, the feedback coil 534 may be wound so as to surround the set including the magnetoresistive element and the magnetic focusing plates arranged at both ends thereof with one coil.

In such a magnetic sensor 520, when a magnetic field is input from the negative side to the positive side of the magnetic field axis, the magnetic focusing plates 720 and 730 made of a material having high magnetic permeability are magnetized, so that in this figure, A magnetic flux distribution as shown by the broken line occurs. Then, the magnetic flux generated by magnetizing the magnetic focusing plates 720 and 730 passes through the position of the magnetoresistive element 710 sandwiched between the two magnetic focusing plates 720 and 730. Therefore, the magnetic flux density at the position of the magnetoresistive element 710 can be significantly increased by arranging the magnetic focusing plates 720 and 730. Further, as shown in this figure, the sampling points in space are clarified by sampling the spatial distribution of the magnetic field using the magnetoresistive element 710 arranged at a narrow position sandwiched between the magnetic focusing plates 720 and 730. Can be done.

FIG. 8 shows the magnetic flux distribution when a feedback magnetic field is generated in the magnetic sensor 520 according to the present embodiment. In FIG. 8, members having the same functions and configurations as those in FIG. 7 are designated by the same reference numerals, and the description thereof will be omitted except for the following differences. In the magnetic sensor 520 according to the present embodiment, when a feedback current is supplied to the feedback coil 534, the feedback coil 534 generates a feedback magnetic field, so that a magnetic flux distribution as shown by a single point chain line in this figure is generated. The magnetic flux generated by this feedback magnetic field is spatially distributed so as to cancel the spatial distribution of the magnetic field that is input to the magnetoresistive element 710 and magnetically amplified by the magnetic focusing plates 720 and 730. Therefore, when the magnetic focusing plates 720 and 730 are arranged at both ends of the magnetoresistive element 710 as shown in this figure, the magnetic sensor 520 accurately determines the magnetic field distribution at the position of the magnetoresistive element 710 by the feedback magnetic field. Since it can be canceled, a sensor with high linearity between the input magnetic field and the output voltage can be realized.

FIG. 9 shows an arrangement example of a plurality of magnetic sensor cells 220 in the magnetic sensor array 210 according to the present embodiment. In FIGS. 2 and 3, a case where the magnetic sensor array 210 is planar is shown as an example. However, as shown in this figure, the magnetic sensor array 210 may have a curved surface shape that is curved in at least one direction. Then, a plurality of magnetic sensor cells 220 may be arranged three-dimensionally so as to be arranged at lattice points included in the curved surface shape. As an example, the magnetic sensor array 210 may be configured by arranging a plurality of magnetic sensor cells 220 three-dimensionally in a cross-sectional view arc shape. The case where the magnetic sensor array 210 has a curved surface shape will be described as an example, but the present invention is not limited to this. The magnetic sensor array 210 does not have to have a curved surface shape as shown in this figure, and may be, for example, a planar shape as shown in FIGS. 2 and 3.

The plurality of magnetic sensor cells 220 may be arranged in an arc shape in a cross-sectional view so as to be centered on the center of gravity of the body to be measured and along the chest of the body to be measured. At this time, each magnetic sensor cell 220 is arranged at each lattice point included in the curved surface shape in the three-dimensional lattice space. Here, the grid points are grid-like points provided at equal intervals in the X direction, the Y direction, and the Z direction at predetermined intervals. As an example, each magnetic sensor cell 220 is arranged along a curved surface having a protrusion in a direction orthogonal to one direction when viewed from any one of the X direction, the Y direction, and the Z direction. In this figure, an example is shown in which each magnetic sensor cell 220 is arranged along a curved surface having a protrusion in the positive direction of the Z axis when viewed from the Y direction. Then, for example, the magnetic sensor array 210 is arranged in the negative direction of the Z axis as much as possible within a range in which each apex of each magnetic sensor cell 220 does not exceed a predetermined curved surface having a convex in the positive direction of the Z axis. As described above, by arranging each magnetic sensor cell 220 at each lattice point in the three-dimensional lattice space, a curved surface shape having a convex shape in the positive direction of the Z axis may be formed.

More specifically, in the cross-sectional view of this figure, a plurality of inner (Z-axis minus side) magnetic sensor cells 220, that is, magnetic sensor cells 220 [1, j, 1] to 220 [8, j, 1] are designated by reference numeral 910. They are arranged along the arc indicated by the alternate long and short dash line of reference numeral 915 so as to form a part of the inscribed circle of the magnetic sensor array 210 indicated by. Further, a plurality of magnetic sensor cells 220 on the outside (Z-axis plus side), that is, magnetic sensor cells 220 [1, j, 2] to 220 [8, j, 2] are circumscribed of the magnetic sensor array 210 indicated by reference numeral 920. They are arranged along the arc indicated by the alternate long and short dash line of reference numeral 925 so as to form a part of a circle.

As a result, the magnetic sensor array 210 can arrange the sensor unit not only in one direction facing the heart but also in multiple directions, and can sense the magnetism from multiple directions. Further, in the magnetic sensor array 210 according to the present embodiment, since the magnetic sensor cell 220 is formed in a rectangular parallelepiped shape as an example, the shape of the magnetic sensor array 210 can be easily changed. That is, the magnetic sensor array 210 according to the present embodiment can take various shapes that can be configured by arranging the magnetic sensor cells 220 at lattice points, and has a high degree of freedom in design. Therefore, as shown in this figure, the magnetic sensor array 210 easily forms a curved surface shape in a three-dimensional space by arranging a plurality of magnetic sensor cells 220 at lattice points included in the curved surface shape in the three-dimensional space. can do. Then, the magnetic field measuring device 10 arranges the magnetic sensor array 210 so that the chest of the object to be measured is located on the center side of the curved surface, that is, the heart, which is the magnetic field source to be measured, is located on the center side of the curved surface. And measure the magnetic field. As a result, the magnetic field measuring device 10 separates the measurement target magnetic field and the disturbance magnetic field with high accuracy by separating the signal space using the measurement data measured at a position close to the heart, which is the measurement target magnetic field source (described later). can do. At this time, it is preferable that the curvature of the curved surface of the magnetic sensor array 210 is substantially equal to the curvature around the chest of the object to be measured because the magnetic field can be measured at a position closer to the heart, which is the magnetic field source to be measured.

FIG. 10 shows the configuration of the sensor unit 300 inches included in the inner magnetic sensor cell 220 in the magnetic sensor array 210 according to the present embodiment. In FIG. 10, members having the same functions and configurations as those in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted except for the following differences. As shown in this figure, a plurality of magnetic sensor cells 220 [1, j, 1] to 220 [8, j] forming an inner magnetic sensor cell 220 in the magnetic sensor array 210, that is, an arc 915 inside the magnetic sensor array 210. , 1] has a sensor unit 300inside, which further includes a switching unit 1010.

The switching unit 1010 switches whether the magnetic field generation unit 530 generates a feedback magnetic field or a calibration magnetic field. That is, at least one of the plurality of magnetic sensor cells 220 in the magnetic sensor array 210, the magnetic sensor cell 220 further has a switching unit 1010 for switching whether the magnetic field generation unit 530 generates a feedback magnetic field or a calibration magnetic field. .. More specifically, the switching unit 1010 is composed of a switch, and one end of the switch is connected to one end of the feedback coil 534. Then, the switching unit 1010 switches whether to input the output of the amplifier circuit 532 to one end of the feedback coil 534 or to input an alternating current according to the frequency of the clock signal for calibration described later. When the switching unit 1010 switches so that one end of the feedback coil 534 inputs an alternating current corresponding to the frequency of the clock signal for calibration, the magnetic field generation unit 530 generates a calibration magnetic field from the feedback coil 534. ..

Such a calibration magnetic field may be an AC magnetic field. As an example, the calibration magnetic field may be a sine wave of frequency f0, or a sine wave of multiple frequencies (eg, frequency f0, frequency f1 (> frequency f0), frequency f2 (> frequency f1), etc.). It may be the sum of waves. Magnetocardiography, which is one of the magnetic fields to be measured by the magnetic field measuring device 10, has no DC component. Therefore, the magnetic field measuring device 10 only calibrates the magnetic sensor using the calibration magnetic field which is an AC magnetic field, and is subject to the DC offset of the magnetic sensor and the offset drift of a very low frequency (for example, 0.1 Hz or less). There is no need to calibrate the magnetic sensor.

Here, in general, the environmental magnetic field is smaller at higher frequencies. For example, the environmental magnetic field is on the order of several tens of pT in a band higher than 50 Hz, which is the same as the peak of magnetocardiography, which is one of the magnetic fields to be measured by the magnetic field measuring device 10 according to the present embodiment. It is a level. Therefore, the magnetic field generation unit 530 may generate an AC magnetic field having a frequency higher than 50 Hz (frequency f0> 50 Hz) as the calibration magnetic field. That is, since the signal frequency of the core magnetism is mostly lower than 20 Hz, the frequency of the AC magnetic field as the calibration magnetic field may be higher than the frequency band of the magnetic field to be measured.

Further, in general, as the frequency of the commercial power supply, for example, 50 Hz or 60 Hz is used. Therefore, power supply noise exists in the multiplication of the frequencies of these commercial power supplies. Therefore, the magnetic field generation unit 530 may use a frequency higher than the frequency of the magnetic field to be measured and avoiding multiplication of the frequency of the commercial power supply as the frequency of the AC magnetic field. As an example, the magnetic field generation unit 530 may use a frequency higher than 50 Hz as the frequency of the calibration magnetic field, avoiding an integral multiple of 50 Hz or 60 Hz. As a result, the environmental magnetic field can be suppressed to the order of several tens of pT, so that the magnetic field generation unit 530 only needs to generate a weak calibration magnetic field of about several tens of nT, for example, to the extent that environmental noise can be ignored. That is, by using such a frequency as the frequency of the AC magnetic field, the magnetic field measuring device 10 does not need to generate a strong magnetic field as the calibration magnetic field.

Further, when calibration is performed using such an AC magnetic field, it is necessary to suppress the generation of eddy current. Therefore, the housing of the feedback coil 534 that generates the calibration magnetic field is preferably formed of a resin material having low electrical conductivity or the like. Similarly, the housing for accommodating the magnetic sensor array 210 for measuring the calibration magnetic field may also be formed of a resin material having low electrical conductivity or the like.

FIG. 11 shows the configurations of the magnetic sensor array 210, the sensor data collection unit 230, and the sensor data processing unit 1100 according to the present embodiment.

The magnetic sensor array 210 is composed of a plurality of magnetic sensor cells 220 each having at least one sensor unit 300, and the magnetic sensor array 210 as a whole can detect an input magnetic field in three axial directions. In this figure, the case where the magnetic sensor array 210 has M sensor units 300 [1] to 300 [M] is shown as an example.

When the magnetic sensor array 210 is calibrated, the magnetic sensor array 210 receives an AC current according to the frequency of the clock signal for calibration, and the magnetic sensor cell 220 is at least one of the plurality of magnetic sensor cells 220 in the magnetic sensor array 210. A calibration magnetic field is generated from the magnetic field generation unit 530 of the magnet. More specifically, the magnetic sensor array 210 includes at least one magnetic sensor cell 220 that generates a calibration magnetic field from the magnetic field generator 530, and a plurality of magnetic sensor cells 220 [1, j, 1] to form an inner arc 915. The feedback coil is sequentially switched over 220 [8, j, 1] one by one, and an AC current corresponding to the frequency of the clock signal for calibration is added to the feedback coil 534 of the sensor unit 300inside of the corresponding magnetic sensor cell 220. From 534, an AC magnetic field corresponding to the frequency of the clock signal is sequentially generated. That is, the calibration magnetic field is generated from the magnetic field generation unit 530 of at least one sensor unit 300 of the plurality of sensor units 300 in the magnetic sensor array 210.

The sensor data acquisition unit 230 has a plurality of AD converters 232 and a clock generator 234. The plurality of AD converters 232 are provided corresponding to each of the plurality of sensor units 300 [1] to 300 [M], and the analog detection signal output by the corresponding sensor unit 300 (V_xMR in FIG. 6). Is converted into digital measurement data V [1] to V [M], respectively.

The clock generator 234 generates a sampling clock and supplies a common sampling clock to each of the plurality of AD converters 232. Then, each of the plurality of AD converters 232 performs AD conversion according to the common sampling clock supplied from the clock generator 234. Therefore, all of the plurality of AD converters 232 for AD-converting the outputs of the plurality of sensor units 300 [1] to 300 [M] provided at different positions perform synchronous operation. As a result, the plurality of AD converters 232 can simultaneously sample the detection results of the plurality of sensor units 300 [1] to 300 [M] provided in different spaces.

The sensor data processing unit 1100 includes a plurality of measurement data acquisition units 1120, a plurality of synchronous detection units 1130, and a plurality of data output units 1140 provided corresponding to each of the plurality of sensor units 300 [1] to 300 [M]. It also has a base vector storage unit 1150, a signal space separation unit 1160, a calibration clock generation unit 1170, an error calculation unit 1180, and a calibration unit 1190.

The measurement data acquisition unit 1120 is connected to each of the plurality of AD converters 232 connected to the corresponding sensor unit 300, and is measured by the plurality of sensor units 300 [1] to 300 [M] included in the magnetic sensor array 210. The measured measurement data V [1] to V [M] are acquired respectively. Specifically, the measurement data acquisition unit 1120 may be configured by using a flip-flop or the like that latches and acquires the digital measurement data V converted to digital by the AD converter 232 at a predetermined timing T. The measurement data acquisition unit 1120 supplies the acquired measurement data V to the synchronous detection unit 1130.

When measuring the measurement target magnetic field, the synchronous detection unit 1130 supplies the measurement data V supplied from the measurement data acquisition unit 1120 to the data output unit 1140 as it is. On the other hand, when performing calibration, the synchronous detection unit 1130 detects the calibration magnetic field, which is an AC magnetic field, using a signal having a frequency of the AC magnetic field. As an example, the synchronous detection unit 1130 synchronously detects the calibration magnetic field according to the clock signal for calibration. In the synchronous detection, for example, the synchronous detection unit 1130 determines the measurement data V [1] to V [M] based on the relationship between the phase of the clock signal for calibration and the phase of the measurement data V [1] to V [M]. The sign of may be determined as positive or negative. Then, the synchronous detection unit 1130 takes out a frequency component (including a signal strength and a code) synchronized with the calibration magnetic field which is an AC magnetic field from the measurement data V supplied from the measurement data acquisition unit 1120, and takes out the frequency component (including the signal strength and the code). The measurement data V related to the frequency component is supplied to the data output unit 1140. Here, such synchronous detection may be performed on software or hardware. Further, in the above description, the case where the synchronous detection unit 1130 performs synchronous detection and extracts the frequency component synchronized with the calibration magnetic field is shown as an example, but the frequency separation by FFT (the frequency component synchronized with the calibration magnetic field is used as an example. A frequency component synchronized with the calibration magnetic field may be extracted by a bandpass filter) or the like.

The data output unit 1140 sets the measurement data V [1] to V [M] supplied from each of the plurality of synchronous detection units 1130 as the sensor signal components Φ [1] to Φ [M], and sets the sensor array signal. Φ is supplied to the signal space separation unit 1160.

The basis vector storage unit 1150 stores the basis vector required for the signal space separation unit 1160 to signal-separate the sensor array signal Φ, and supplies this to the signal space separation unit 1160. The basis vector storage unit 1150 sequentially updates the stored basis vector to the basis vector changed by the calibration unit 1190. This will be described later.

The signal space separation unit 1160 sets the spatial distribution of the input magnetic field indicated by the measurement data V [1] to V [M] supplied as each component of the sensor array signal Φ from the data output unit 1140 to the spatial distribution of the normal orthogonal function. When a magnetic field having a magnetic field is detected by the magnetic sensor array 210, a vector signal having a signal output from each of the plurality of magnetic sensors 520 as each signal component is used as a base vector for signal separation. At this time, the signal space separation unit 1160 acquires the basis vector required for signal separation from the basis vector storage unit 1150. Then, the signal space separation unit 1160 uses the base vector acquired from the base vector storage unit 1150 to measure the spatial distribution of the magnetic field indicated by the measurement data V [1] to V [M], and obtains the measurement target magnetic field (signal source space). The signal is separated into a disturbance magnetic field (disturbance space signal), the disturbance magnetic field is suppressed, the measurement target magnetic field is calculated, and this is output. This will also be described later.

When performing calibration, the calibration clock generation unit 1170 generates a clock signal for generating an AC calibration magnetic field and an AC current corresponding to the frequency thereof. Then, the calibration clock generation unit 1170 supplies the generated clock signal to each of the magnetic sensor array 210 and the plurality of synchronous detection units 1130. In response to this, the magnetic sensor array 210 has at least one magnetic sensor cell 220 that generates a calibration magnetic field from the magnetic field generation unit 530, and a plurality of magnetic sensor cells 220 [1, j, 1] to form an inner arc 915. It is sequentially switched one by one over 220 [8, j, 1], and an AC magnetic field corresponding to the frequency of the clock signal is sequentially generated from the feedback coil 534 of the sensor unit 300inside of the corresponding magnetic sensor cell 220. Further, the plurality of synchronous detection units 1130 each detect an alternating current calibration magnetic field generated by the magnetic field generation unit 530 of at least one magnetic sensor cell according to the clock signal. In the above description, the case where the calibration clock generation unit 1170 is provided inside the sensor data processing unit 1100 is shown as an example, but the calibration clock generation unit 1170 is, for example, the sensor data collection unit. It may be configured inside the 230.

When the error calculation unit 1180 performs calibration, the signal space separation unit 1160 determines the spatial distribution of the calibration magnetic field generated from the magnetic field generation unit 530 of at least one of the plurality of magnetic sensor cells 220. Calculate the separation error when the signals are separated. Then, the error calculation unit 1180 supplies the calculated separation error to the calibration unit 1190.

The calibration unit 1190 uses the magnetic sensor 520 based on the separation error when the spatial distribution of the calibration magnetic field generated from the magnetic field generation unit 530 of at least one of the plurality of magnetic sensor cells 220 is signal-separated. Calibrate the sensor error in. More specifically, the calibration unit 1190 uses at least one magnetic sensor cell 220 that generates a calibration magnetic field from the magnetic field generation unit 530, and a plurality of magnetic sensor cells 220 [1, j, 1] to 220 that form an inner arc 915. The sensor error in the magnetic sensor 520 is calibrated based on each separation error in the case of sequentially switching over [8, j, 1]. At this time, the calibration unit 1190 calibrates the sensor error by changing the basis vector used by the signal space separation unit 1160. Then, the calibration unit 1190 supplies the information regarding the changed basis vector to the basis vector storage unit 1150. In response to this, the basis vector storage unit 1150 updates the basal vector to be stored. This will be described in detail using mathematical formulas.

FIG. 12 shows a flow in which the magnetic field measuring device 10 according to the present embodiment signals separates the spatial distribution of the magnetic field. In step 1210, the basis vector storage unit 1150 stores the basis vector. As an example, the basis vector storage unit 1150 uses a signal vector predetermined by the result of simulation assuming that the magnetic sensor array 210 is ideally created without any error of each sensor as an initial basis vector. You may remember. Further, as will be described later, the basis vector storage unit 1150 may store the changed and updated basis vector when the sensor error is calibrated by the calibration unit 1190.

Next, in step 1220, the signal space separation unit 1160 acquires the sensor array signal Φ measured by the magnetic sensor array 210, that is, the measurement data V [1] to V [M] from the data output unit 1140.

Further, in step 1230, the signal space separation unit 1160 acquires the signal vector stored as the basis vector by the basis vector storage unit 1150 in step 1210 from the basis vector storage unit 1150. In this flow, either step 1220 or step 1230 may be performed first.

In step 1240, the signal space separation unit 1160 uses the spatial distribution of the magnetic field indicated by the measurement data V [1] to V [M] acquired in step 1220 as the base vector using the signal vector acquired in step 1230. Expand the series. Then, the signal space separation unit 1160 separates the spatial distribution of the magnetic field into the measurement target magnetic field and the disturbance magnetic field from the vector obtained by the series expansion. That is, the signal space separation unit 1160 is magnetic when the magnetic field having the spatial distribution of the normal orthogonal function is detected by the magnetic sensor array 210 for the spatial distribution of the input magnetic field indicated by the measurement data V [1] to V [M]. A vector signal having a signal output by each of the sensors 520 as each signal component is used as a base vector for signal separation. Here, the orthonormal function may be a spherical harmonic. Further, the signal space separation unit 1160 calculates the coefficient of the basis vector by the method of least squares when separating signals.

Then, in step 1250, the signal space separation unit 1160 suppresses the disturbance magnetic field, calculates and outputs only the measurement target magnetic field based on the result of signal separation in step 1240, and ends the process. This will be described in detail below.

When the current i (r) = 0 at the position of the position vector r representing the position from the coordinate origin with respect to the position where each sensor constituting the magnetic sensor array 210 is arranged, the static magnetic field B (r) is Laplace. Using the potential V (r) satisfying the equation Δ · V (r) = 0, it can be obtained as a magnetic gradient of the potential V (r) as shown in the following equation. Here, Δ is the Laplacian, μ is the magnetic permeability, and ∇ is an operator representing a vector differential operation.

Since the solution of Laplace's equation generally _{has a solution in the form of series expansion using the spherical harmonics Y l, m} (θ, φ), which is a normal orthogonal function system, the potential V (r) is given by the following equation. Can be represented by. Here, | r | is the absolute value of the position vector r (distance from the coordinate origin), θ and φ are two deviation angles in spherical coordinates, l is the azimuthal quantum number, and m is the magnetic quantum number. Α and β are multipolar moments, and Lin and Lout are the number of coordinates for the space in front of the magnetic sensor array 210 and the space in the back, respectively, when viewed from the object to be measured. The azimuthal quantum number l takes a positive integer, and the magnetic quantum number m takes an integer from −l to + l. That is, for example, when l is 1, m is -1, 0, and 1, and when l is 2, for example, m is -2, -1, 0, 1, and 2. Since there is no monopole in the magnetic field, the azimuthal quantum number l starts from 1 instead of 0 in (Equation 5). The first term in (Equation 5) is a term that is inversely proportional to the distance from the coordinate origin, and indicates the potential existing in the space in front of the magnetic sensor array 210 when viewed from the object to be measured. The second term in (Equation 5) is a term proportional to the distance from the coordinate origin, and indicates the potential existing in the space behind the magnetic sensor array 210 when viewed from the object to be measured.

Therefore, according to (Equation 4) and (Equation 5), the static magnetic field B (r) can be expressed by the following equation. Here, the first term in (Equation 6) is a magnetic field source existing in the space in front of the magnetic sensor array 210 when viewed from the object to be measured, that is, for example, a magnetocardiography created by the electrical activity of the heart (magnetic field to be measured). Is shown. Further, the second term in (Equation 6) indicates a disturbance magnetic field created by a magnetic field source existing in the space behind the magnetic sensor array 210 when viewed from the object to be measured.

When the solution of the Laplace equation is expressed in the form of a series expansion using spherical harmonics, the general solution is an infinite series, but the SNR (signal noise ratio, that is, the disturbance magnetic field and It suffices to obtain the ratio of the magnetic field signal to be measured to the sensor noise), and it is said that it is actually sufficient to express it in a series of about 10 terms. Further, it is said that the series of signal space separation in the magnetoencephalograph may be about Lin = 8 and Lout = 3. Therefore, also in this embodiment, the case of Lin = 8 and Lout = 3 will be described as an example. However, the values of Lin and Lout are not limited to this, and may be any numerical value sufficient to sufficiently suppress the disturbance magnetic field and calculate only the magnetic field to be measured.

Here, the sensor array signal Φ is composed of an M-dimensional vector, and each signal component of the vector is a magnetic field vector B (r [m]) in the position vector r [m] in which the magnetic sensor 520 of each sensor unit 300 is arranged. ) And the inner product of the magnetic sensitivity vector S [m] of each magnetic sensor 520. Therefore, for each magnetic sensor 520, the magnetic sensitivity vector S _Ideal [m] = (S _Ideal [m], x, S _Ideal [m], y, S _Ideal [m], z) as designed for each magnetic sensor 520. When held and placed in the designed position, the ideal sensor array signal Φ _Ideal is expressed by:

That is, each ideal sensor has no sensor error (magnetic sensitivity error due to other axis sensitivity or spindle sensitivity of each sensor, position error due to displacement of each sensor during assembly of the magnetic sensor array 210, etc.). The signal component Φ _Ideal [m] is expressed by the following equation.

Therefore, in the ideal case where there is no sensor error in each magnetic sensor 520, the basis vectors a _{Ideal l, m} and b _{Ideal l, m} are defined by the following equations.

Here, in an ideal case where there is no sensor error in each magnetic sensor 520, A _Ideal , B _Ideal , Xin, and Xout are defined as follows, respectively. That _is, the _{A Ideal,} from l = 1 to L = Lin, each vector _{a Ideal} when taking integer from m = -l to l in each l were sequentially arranged in columns, a total of Lin · (Lin + 2) column Defined as a vector of. _Further, the _{B Ideal,} from l = 1 to L = Lout, each vector _{b Ideal} when taking integer from m = -l to l in each l were sequentially arranged in columns, a total of Lout · (Lout + 2) column Defined as a vector of. Further, Xin is transposed from a vector in which each multipolar moment α when an integer from m = −l to l is taken in each l from l = 1 to l = Lin is transposed. It is defined as a vector of (Lin + 2) rows. Further, Xout is transposed from a vector in which each multipolar moment β when an integer from m = −l to l is taken in each l from l = 1 to l = Lout is transposed, for a total of Lout · (Lout + 2). ) Defined as a row vector.

Then, the sensor array signal Φ _Ideal of the ideal magnetic sensor array 210 can be expressed in the form of the inner product of the ideal basis vector matrix [ _{AB] Ideal and the vertical vector X as shown in the following equation.} Here, the ideal basis vector matrix [ _AB ] Ideal indicates a basis vector, for example, which is acquired by the signal space separation unit 1160 from the basis vector storage unit 1150 in step 1230. Further, the vertical vector X indicates a coefficient related to the basis vector.

_{In step 1240, the signal space separation unit 1160 satisfies Φ Ideal} = [ _{AB] Ideal} X with a minimum square approximation using the following equation based on the model equation obtained in this (Equation 11). Determine the vector ^ X _Ideal (where "^ X _ideal " indicates the left-hand side of (Equation 12) and means the hat (estimated value) of _{X Ideal).}

_{Therefore, the signal space separation unit 1160 can express the hat ^ Φ Ideal} of the sensor array signal of the ideal magnetic sensor array 210 as an M-dimensional vector of the minimum squared solution by the following equation. As a result, the signal space separation unit 1160 can solve the spatial distribution of the magnetic field in step 1240.

Then, in step 1250, the signal space separation unit 1160 _{reduces the ^ Xout · B Ideal} by using the vertical vector determined in step 1240 to reduce the disturbance magnetic field component, that is, the component of the second term in (Equation 6). Output the suppressed result. The signal space separation unit 1160 _{suppresses the disturbance magnetic field component by outputting only ^ Xin · A Ideal} as a result, and outputs only the measurement target magnetic field component, that is, the component of the first term in (Equation 6). You may. That is, the signal space separation unit 1160 separates the signal space into the disturbance magnetic field component and the measurement target magnetic field component.

As a result, according to the magnetic field measuring device 10 according to the present embodiment, the measurement data V [1] measured using the magnetic sensor array 210 having a plurality of magnetic sensor cells 220 and capable of detecting the input magnetic field in the three axial directions. ] ~ V [M], the spatial distribution of the magnetic field can be signal-separated into the measurement target magnetic field and the disturbance magnetic field. Further, since the magnetic field measuring device 10 suppresses the disturbance magnetic field component and outputs only the measurement target magnetic field component, the measurement target magnetic field can be measured with higher accuracy. Further, since each of the plurality of sensor units 300 has a magnetic focusing plate, the magnetic sensitivity of the sensor unit 300 can be enhanced, the spatial sampling point can be clarified, and the affinity with the signal space separation technology can be further enhanced. can.

FIG. 13 geometrically shows a signal space separation operation using _{the ideal basis vector [AB} ] Ideal when the magnetic sensor array 210 is ideally constructed. Reference numeral 1310 indicates the sensor array signal Φ _Ideal of the ideal magnetic sensor array 210. Reference numeral 1320 indicates a linear subspace Span {A _Ideal } stretched by the ideal basis vector A _Ideal. Reference numeral 1330 indicates a linear subspace Span {B _Ideal } stretched by the ideal basis vector B _Ideal. Reference numeral 1340 indicates a linear subspace stretched by _{an ideal basis vector [AB} ] ideal that is a linear sum of the linear _{subspace Span {A Ideal} } and the linear subspace Span {B _Ideal}. Reference numeral 1350 indicates an M-dimensional vector of a minimum squared solution. As shown in this figure, if the magnetic sensor array 210 is ideally made, i.e. without sensor error, the sensor array signal Φ _Ideal of the ideal magnetic sensor array 210 is ideal. It exists in a linear subspace stretched by the basis vector [ _{AB] Ideal.} That is, the equation (Equation 11) is established with high accuracy, and the signal space separation unit 1160 accurately separates the signal space into the target magnetic field component and the disturbance magnetic field component with respect to the magnetic field detected by the magnetic sensor array 210. Can be done.

However, the actual sensor signal component Φ _{Uncalib [m] from each sensor unit 300 is a magnetic sensitivity vector S Uncalib} [m] = (S _Uncalib [m], x, S) including the magnetic sensitivity error of each magnetic sensor 520. _{It is expressed using Uncalib} [m], y, S _Uncalib [m], z). That is, the magnetic sensor array 210 _{assumes a magnetic sensitivity vector S Ideal} [m] = (S _Ideal [m], x, S _Ideal [m], y, S _Ideal [m], z) for each magnetic sensor 520. Although to being made, the actual unknown magnetic sensitivity offset therefrom to the vector _{S Uncalib [m] = (S} Uncalib [m], x, S Uncalib [m], y, S Uncalib [m], z ) Is completed.

That is, each sensor signal component Φ _Uncalib [m] having a magnetic sensitivity error is expressed by the following equation.

_{In this way, for the sensor array signal Φ Uncalib} measured by the magnetic sensor array 210 created with the magnetic sensitivity error, the equation of the following equation is used using the assumed ideal base vector [ _{AB] Ideal.} Suppose you want to set up.

_{Then, even if the vertical vector ^ X Uncalib} is determined by the following equation based on the model equation obtained in (Equation 15), the solution of the equation is inaccurate.

In this case, as the M-dimensional vector of the least squares solution, the hat ^ Φ _Uncalib of the sensor array signal of the magnetic sensor array 210 having a magnetic sensitivity error is expressed by the following equation.

FIG. 14 geometrically shows a signal space separation operation using _{the ideal basis vector [AB} ] Ideal when the magnetic sensor array 210 is made with sensor error. In FIG. 14, members having the same functions and configurations as those in FIG. 13 are designated by the same reference numerals, and the description thereof will be omitted except for the following differences. _Reference numeral 1410 indicates a sensor array signal Φ Uncalib of the magnetic sensor array 210 having a sensor error. Reference numeral 1450 indicates an M-dimensional vector of a minimum squared solution. As shown in this figure, when the magnetic sensor array 210 has a sensor error, the sensor array signal Φ _Uncalib does not exist in the linear subspace stretched by the ideal basis vector [ _{AB] Ideal.} ..

At this time, the separation error, that is, the error vector ε represented by the reference numeral 1460, is between the _{sensor array signal Φ Uncalib} indicated by the reference numeral 1410 and the M-dimensional vector ^ Φ _{Uncalib of the minimum squared solution indicated by the reference numeral 1450.} And the error angle γ indicated by reference numeral 1470 occurs. Here, the error vector ε and the error angle γ are expressed by the following equations.

As described above, the error vector ε in the signal space separation calculation is generated as a finite vector (not a zero vector) due to the sensor error of the actual magnetic sensor array 210. Therefore, the equation of (Equation 15) is not established with high accuracy, and the solution of the equation shown in (Equation 16) is inaccurate. That is, the signal space separation unit 1160 cannot accurately perform signal space separation between the target magnetic field component and the disturbance magnetic field component with respect to the magnetic field detected by the magnetic sensor array 210.

Therefore, the magnetic field measuring device 10 according to the present embodiment calibrates the sensor error in the magnetic sensor 520 so as to reduce the separation error when such a signal space separation calculation is performed.

FIG. 15 shows a flow in which the magnetic field measuring device 10 according to the present embodiment acquires the sensor array signal Φ (i, j, 1) for calibration. Here, i indicates the position of the magnetic sensor cell 220 in the magnetic sensor array 210 in the X direction, and is an integer satisfying 1 ≦ i ≦ Nx (where Nx indicates the number of magnetic sensor cells 220 arranged in the X direction). Is. Further, j indicates the position of the magnetic sensor cell 220 in the magnetic sensor array 210 in the Y direction, and is an integer satisfying 1 ≦ j ≦ Ny (where Ny indicates the number of magnetic sensor cells 220 arranged in the Y direction). be. Further, k indicates the position of the magnetic sensor cell 220 in the magnetic sensor array 210 in the Z direction, and z is fixed to 1 in this flow. Further, in the description of this flow and the flow of FIG. 16 described later, the M / 2 sensor units 300 included in the plurality of magnetic sensor cells 220 forming the inner arc 915 of the M sensor units 300 are sequentially calibrated. An example of measuring with the remaining M-1 sensor units 300 that generate a magnetic field and do not generate a magnetic field is shown. However, the number of the sensor units 300 that generate the calibration magnetic field is not limited to this number, and can be realized from one depending on the parameter to be calibrated (for example, calibration of one component of the position coordinates). In addition, the number of sensors that measure the magnetic field can be changed according to the calibration parameters and the dimensions of the basis vector, and M-1 sensors that do not generate a magnetic field from several sensors required to form the basis vector. Can be a number. Further, even if the measurement is performed by the M-1 sensor units 300 that do not generate a magnetic field, the number of the sensor units 300 to be calibrated for the sensor error may be smaller than that of the M-1 sensor units 300. For example, the sensor error may be calibrated for the M / 2 sensor units 300 that do not generate a calibration magnetic field.

In step 1510, the magnetic field measuring device 10 initializes the cell address. As an example, the magnetic field measuring device 10 substitutes 1 for i, 1 for j, and 1 for k. That is, the magnetic field measuring device 10 designates the magnetic sensor cell 220 [1,1,1] as the first magnetic sensor cell 220 that generates the calibration magnetic field.

In step 1520, the magnetic field measuring device 10 is transmitted from the magnetic field generation unit 530 included in the magnetic sensor cell 220 [i, j, 1], for example, in step 1520 following step 1510, the magnetic sensor cell [1,1,1]. Generate a calibration magnetic field. That is, the magnetic field measuring device 10 switches the switching unit 1010 in the sensor unit 300 of the magnetic sensor cell 220 [i, j, 1] to the calibration mode, and is supplied to one end of the feedback coil 534 from the calibration clock generating unit 1170. The alternating current corresponding to the frequency of the clock signal for calibration is input. Then, the magnetic field measuring device 10 generates an AC magnetic field according to the frequency of the clock signal from the feedback coil 534 of the magnetic sensor cell 220 [i, j, 1]. At this time, the calibration magnetic field generated by the feedback coil 534 of the magnetic sensor cell 220 [i, j, 1] is close to the magnetic field generated from the magnetic dipole. The calibration magnetic field generated by the feedback coil 534 of the magnetic sensor cell 220 [i, j, 1] corresponds to the component of the first term in (Equation 6). At this time, by generating an AC magnetic field having a relatively strong strength from the feedback coil 534, the influence of the second term component in (Equation 6), that is, the disturbance magnetic field can be ignored at the time of calibration.

In step 1530, the magnetic field measuring device 10 acquires the sensor array signal Φ (i, j, 1) when the calibration magnetic field is generated from the feedback coil 534 of the magnetic sensor cell 220 [i, j, 1]. .. More specifically, when a calibration magnetic field is generated from the feedback coil 534 of the magnetic sensor cell 220 [i, j, 1], the measurement data acquisition unit 1120 has a plurality of sensor units 300 of the magnetic sensor array 210 [i, j, 1]. 1] to 300 [M], except for the sensor unit 300 [P] (where P is an integer where 1 ≦ P ≦ M) that generated the calibration magnetic field, (M-1). The measurement data V [1] to V [M] measured by the sensor unit 300 are acquired respectively. Then, the synchronous detection unit 1130 receives the clock signal for calibration supplied from the clock generation unit 1170 for calibration, and synchronously detects the calibration magnetic field according to the clock signal. Then, the synchronous detection unit 1130 extracts a frequency component synchronized with the calibration magnetic field, which is an AC magnetic field, from the measurement data V [1] to V [M], and measures data V [1] related to the extracted frequency component. ] To V [M] are supplied to the data output unit 1140, respectively. Then, the data output unit 1140 generates a calibration magnetic field from the feedback coil 534 of the magnetic sensor cell 220 [i, j, 1] for the measurement data V [1] to V [M] supplied from the synchronous detection unit 1130. Each sensor signal component Φ [1] from a plurality of (that is, M-1) sensor units 300 [1] to 300 [M] excluding the sensor unit 300 [P] that generated the calibration magnetic field in the case of ] To Φ [M] (excluding Φ [P]), the sensor array signal Φ (i, j, 1) for calibration is supplied to the signal space separation unit 1160. As a result, the signal space separation unit 1160 uses the sensor array signal Φ (i, j, 1) for calibration when the calibration magnetic field is generated from the feedback coil 534 of the magnetic sensor cell 220 [i, j, 1]. To get.

In step 1540, the magnetic field measuring device 10 determines whether i is equal to Nx. That is, the magnetic field measuring device 10 determines whether or not the calibration magnetic field is generated from the magnetic field generating unit 530 of all the magnetic sensor cells 220 arranged in the X direction. When it is determined that i is equal to Nx, that is, when it is determined that the calibration magnetic field is generated from the magnetic field generation unit 530 of all the magnetic sensor cells 220 arranged in the X direction, the magnetic field measuring device 10 processes. To step 1560.

On the other hand, in step 1540, when it is determined that i is not equal to Nx, that is, it is determined that the calibration magnetic field is not generated from the magnetic field generation unit 530 of all the magnetic sensor cells 220 arranged in the X direction. In the case, the magnetic field measuring device 10 increments i to set i = i + 1 in step 1550, returns the process to step 1520, and continues the flow.

In step 1560, the magnetic field measuring device 10 determines whether j is equal to Ny. That is, the magnetic field measuring device 10 determines whether or not the calibration magnetic field is generated from the magnetic field generation unit 530 of all the magnetic sensor cells 220 arranged in the Y direction. When it is determined that j is equal to Ny, that is, when it is determined that the calibration magnetic field is generated from the magnetic field generation unit 530 of all the magnetic sensor cells 220 arranged in the Y direction, the magnetic field measuring device 10 calibrates. The flow for acquiring the sensor array signal Φ (i, j, 1) for the operation is terminated.

On the other hand, in step 1560, when it is determined that j is not equal to Ny, that is, it is determined that the calibration magnetic field is not generated from the magnetic field generation unit 530 of all the magnetic sensor cells 220 arranged in the Y direction. In the case, the magnetic field measuring device 10 increments j to j = j + 1 in step 1570, returns the process to step 1520, and continues the flow.

As a result, the magnetic field measuring device 10 is included in a plurality of magnetic sensor cells 220 forming k = 1, that is, an inner arc 915 from i = 1 to i = Nx and from j = 1 to j = Ny. The array signals Φ (i, j, 1) for calibration when the calibration magnetic field is generated from the magnetic field generation unit 530 of the M / 2 sensor units 300 are acquired respectively.

FIG. 16 shows a flow in which the magnetic field measuring device 10 according to the present embodiment calibrates. In this flow, an example of calibrating the sensor error for M / 2 sensor units 300 that do not generate a calibration magnetic field is shown. In step 1610, the magnetic field measuring device 10 substitutes 1 for C. Here, C means the number of times the calibration is executed, and indicates an integer from 1 to MAX_COUNT, which is the upper limit of the number of times the calibration is executed.

In step 1620, the magnetic field measuring device 10 calculates the separation error. More specifically, the signal space separation unit 1160 performs signal space separation for the sensor array signal Φ (i, j, 1) for calibration for 1 ≦ i ≦ Nx and 1 ≦ j ≦ Ny, respectively. conduct. At this time, in step 1620 following step 1610, the signal space separation unit 1160 determines the solution of the equation shown in (Equation 16) from the equation shown in (Equation 15). At this time, the signal space separation unit 1160 is at a position where the magnetic field generation unit 530 of at least one magnetic sensor cell 220 that generates the calibration magnetic field from the magnetic field generation unit 530 is arranged when the spatial distribution of the calibration magnetic field is signal-separated. Is the origin of the coordinates in the calculation. That is, the signal space separation unit 1160 calculates the position where the magnetic field generation unit 530 of the magnetic sensor cell 220 [1,1,1] is arranged when the sensor array signal Φ (1,1,1) is signal-separated. Let it be the origin of the coordinates in. Similarly, the signal space separation unit 1160 sets the position where the magnetic field generation unit 530 of the magnetic sensor cell 220 [i, j, 1] is arranged when the sensor array signal Φ (i, j, 1) is separated. For example, the center position of the feedback coil 534 of the magnetic field generation unit 530 is set as the origin of the coordinates in the calculation. In this way, when the calibration magnetic field is generated from the magnetic field generation unit 530 (n) of the nth magnetic sensor cell 220 (n is an integer from 1 to M / 2), the signal space separation unit 1160 generates the magnetic field. It is equal to the sensor array signal Φ (n) (Φ (i, j, 1)) when the calibration magnetic field is generated from the part 530 (n). After that, the magnetic field from the nth magnetic field generation part 530 (n) is measured. In performing the signal space separation calculation and the calculation of the error ε for the sensor array signal Φ (abbreviated as Φ (n)), the coordinates in the signal space separation calculation are located at the position where the magnetic field generator 530 (n) is arranged. The calculation is performed while sequentially matching the origins. As a result, the magnetic field measuring device 10 can greatly simplify the calibration of each magnetic sensor 520 in the sensor unit 300 included in the magnetic sensor array 210, and accelerate the convergence of the calibration parameters. Then, based on (Equation 18), the error calculation unit 1180 forms k = 1, that is, an inner arc 915 from i = 1 to i = Nx and from j = 1 to j = Ny. When the calibration magnetic field is generated from the magnetic field generation unit 530 of the M / 2 sensor units 300 included in the magnetic sensor cell 220 of the above, the error vector ε (n) and the error angle γ (n) are the separation errors. ) At least one of them is calculated.

In step 1630, the magnetic field measuring device 10 determines whether or not the separation error exceeds a predetermined threshold value. For example, the magnetic field measuring device 10 determines whether or not the sum of squares of M / 2 separation errors exceeds a predetermined threshold value. That is, the magnetic field measuring device 10 includes M included in a plurality of magnetic sensor cells 220 forming an inner arc 915, that is, k = 1 from i = 1 to i = Nx and from j = 1 to j = Ny. / At least one of the sum of squares of the error vector ε (n) and the sum of squares of the error angle γ (n) when the calibration magnetic field is generated from the magnetic field generation unit 530 of the two sensor units 300. It is determined whether or not one of them exceeds a predetermined threshold value. If it is determined that the separation error does not exceed the threshold value, the magnetic field measuring device 10 terminates the process assuming that the calibration is completed.

On the other hand, if it is determined in step 1630 that the separation error exceeds a predetermined threshold value, the magnetic field measuring device 10 calibrates the sensor error in step 1640. That is, for example, when the calibration magnetic field is generated from the magnetic field generation unit 530 of the first to M / second sensor units 300, the magnetic field measuring device 10 uses the sensor unit 300 in the first magnetic sensor cell 220. The sensor error is calibrated for the M / 2 sensor unit 300 using the M / 2 sensor array signals Φ (1) to Φ (M / 2) excluding the sensor signal component from. For example, the calibration unit 1190 sets M / 2 + 1 ≦ m ≦ M so that at least one of the separation error as the objective function, that is, the error vector ε (n) and the error angle γ (n) is set to zero. The magnetic sensitivity vector S _Calib [m] is optimized for. At this time, the calibration unit 1190 may use, for example, a computer science method such as stochastic annealing. Here, the basis vector after calibration is expressed as the following equation (for convenience, it is described as an M-dimensional vector). In this way, the calibration unit 1190 changes the basis vector so as to minimize the separation error by optimizing _{the magnetic sensitivity vector S Calib [m].}

In step 1650, the magnetic field measuring device 10 determines whether C is equal to MAX_COUNT. That is, the magnetic field measuring device 10 determines whether or not the number of times the calibration is executed is the upper limit number of times.

When C is equal to MAX_COUNT, that is, when the number of calibration executions is the upper limit, the magnetic field measuring device 10 times out the calibration execution in step 1660 and ends the process. At this time, the magnetic field measuring device 10 may notify, for example, that the calibration has timed out.

On the other hand, when C is not equal to MAX_COUNT, the magnetic field measuring device 10 increments C to C = C + 1 in step 1670, initializes n to n = 1, returns the process to step 1620, and continues the flow. do. In step 1620 following step 1670, the signal space separation unit 1160 may determine the solution of the equation by the following equation instead of (Equation 16).

Further, the signal space separation unit 1160 may determine _{the hat ^ Φ Calib} of the sensor array signal of the magnetic sensor array 210 having a sensor error as the minimum squared solution vector by the following equation.

Then, the signal space separation unit 1160 may calculate the separation error between the _{sensor array signal Φ Calib} and the minimum squared solution vector ^ Φ _{Calib by the same method as in (Equation 18).}

As described above, according to the magnetic field measuring device 10 according to the present embodiment, when calibrating the magnetic sensor array 210, the magnetic field generated by at least one of the plurality of magnetic sensor cells 220 in the magnetic sensor array 210 is generated. A calibration magnetic field is generated from unit 530. That is, the calibration magnetic field is generated from the magnetic field generation unit 530 of at least one sensor unit 300 of the plurality of sensor units 300 in the magnetic sensor array 210. Therefore, the magnetic field measuring device 10 does not need to separately provide a device (coil or the like) for generating a calibration magnetic field in addition to the magnetic sensor array 210. Further, according to the magnetic field measuring device 10 according to the present embodiment, at least one magnetic sensor cell 220 that generates a calibration magnetic field from the magnetic field generation unit 530 is used as a plurality of magnetic sensor cells 220 [1, j] that form an inner arc 915. , 1] to 220 [8, j, 1] are sequentially switched, and the magnetic sensor array 210 is calibrated based on each separation error. Therefore, the magnetic field measuring device 10 can reduce the distance between the coil that generates the calibration magnetic field and the magnetic sensor 520 to be calibrated, and makes the calibration magnetic field input to the magnetic sensor 520 relative to each other. Can be made stronger. As a result, the magnetic field measuring device 10 can improve the SNR in the calibration calculation. Further, since the magnetic field measuring device 10 generates a calibration magnetic field from each of the magnetic field generating units 530 of all the plurality of magnetic sensor cells 220 forming the inner arc 915, it is used for calibrating the magnetic sensor array 210. As the calibration magnetic field, a magnetic dipole magnetic field with little bias with respect to the position and the direction of the magnetic field in the magnetic sensor array 210 can be generated.

In the above description, the magnetic field measuring device 10 sequentially creates a magnetic field generating unit 530 of M / 2 sensor units 300 included in a plurality of magnetic sensor cells 220 forming an arc 915 inside the magnetic sensor array 210. The case where the calibration magnetic field is generated by switching is shown as an example, but the present invention is not limited to this. The magnetic field measuring device 10 sequentially switches the M / 2 sensor units 300 included in the magnetic sensor cell 220 located outside in addition to the magnetic sensor cell 220 located inside the magnetic sensor array 210 to generate a calibration magnetic field. You may. That is, the magnetic field measuring device 10 may sequentially switch the magnetic field generation unit 530 included in all the magnetic sensor cells 220 in the magnetic sensor array 210 to generate a calibration magnetic field. When the magnetic field generation unit 530 of the magnetic sensor cell 220 located inside the magnetic sensor array 210 is sequentially switched to generate a calibration magnetic field, as described above, the component of the second term in (Equation 6) at the time of calibration is used. Can be ignored. On the other hand, when a plurality of magnetic sensor cells 220 forming the outer arc 925 of the magnetic sensor array 210 are sequentially switched to generate a calibration magnetic field, the component of the first term in (Equation 6) can be ignored at the time of calibration. ..

In that case, the magnetic field measuring device 10 generates a calibration magnetic field according to the number of calibration parameters and the number of dimensions of the base vector, as described above, while sequentially switching the magnetic field generation unit 530 of all the magnetic sensor cells 220. The sensor errors may be calibrated for all of the M sensor units 300 by sequentially calibrating the sensor errors for the (M-1) sensor units 300 excluding the sensor units 300 [P].

Instead of this, the magnetic field measuring device 10 calibrates while sequentially switching the magnetic sensor cells 220 [1, j, 1] to 220 [8, j, 1] having M / 2 sensor units 300 located inside. Even if a magnetic field is generated and the sensor error is sequentially calibrated only for the sensor unit 300 of the M / 2 magnetic sensor cells 220 [1, j, 2] to 220 [8, j, 2] located on the outside. good. Similarly, the magnetic field measuring device 10 shifts the calibration magnetic field while sequentially switching the magnetic sensor cells 220 [1, j, 2] to 220 [8, j, 2] having M / 2 sensor units 300 located on the outside. The sensor error may be sequentially calibrated for only the sensor unit 300 of the M / 2 magnetic sensor cells 220 [1, j, 1] to 220 [8, j, 1] located inside. That is, all the sensor errors of both the sensor unit 300 of the M / 2 magnetic sensor cells 220 located inside and the sensor unit 300 of the M / 2 magnetic sensor cells 220 located outside may be calibrated separately.

Further, in the above description, the case where the magnetic field measuring device 10 controls a plurality of magnetic sensor cells 220 in the magnetic sensor array 210 by classifying them into an inner magnetic sensor cell 220 group and an outer magnetic sensor cell 220 group is shown as an example. However, it is not limited to this. For example, the magnetic field measuring device 10 arranges a plurality of magnetic sensor cells 220 in the magnetic sensor array 210 on the left side of the magnetic sensor cells 220 [1, j, 1] to 220 [4, j, 2] group and the right side when viewed from the object to be measured. The magnetic sensor cells 220 [5, j, 1] to 220 [8, j, 2] may be divided into groups and controlled in the same manner as described above. That is, the magnetic field measuring device 10 generates a calibration magnetic field while sequentially switching the magnetic sensor cells 220 [1, j, 1] to 220 [4, j, 2] having M / 2 sensor units 300 located on the left side. Then, the sensor error may be sequentially calibrated only for the sensor unit 300 of the M / 2 magnetic sensor cells 220 [5, j, 1] to 220 [8, j, 2] located on the right side. Similarly, the magnetic field measuring device 10 shifts the calibration magnetic field while sequentially switching the magnetic sensor cells 220 [5, j, 1] to 220 [8, j, 2] having M / 2 sensor units 300 located on the right side. The sensor error may be sequentially calibrated for only the sensor unit 300 of the M / 2 magnetic sensor cells 220 [1, j, 1] to 220 [4, j, 2] located on the left side.

As described above, the magnetic field measuring device 10 classifies the plurality of magnetic sensor cells 220 in the magnetic sensor array 210 into a first magnetic sensor cell 220 group and a second magnetic sensor cell 220 group, and the first magnetic sensor cell 220 group. A calibration magnetic field is generated while sequentially switching the magnetic sensor cells 220, the sensor error is sequentially calibrated for the sensor unit 300 in the second magnetic sensor cell 220 group, and the magnetic sensor cells 220 of the second magnetic sensor cell 220 group are sequentially switched. While generating a calibration magnetic field, the sensor error may be sequentially calibrated for the sensor unit 300 in the first magnetic sensor cell 220 group.

The magnetic field measuring device 10 generates a calibration magnetic field while sequentially switching the magnetic sensor cells 220 of one magnetic sensor cell 220 group, and sequentially calibrates the sensor error for the sensor unit 300 of the other magnetic sensor cell 220 group. , It is not necessary to generate a calibration magnetic field from all the magnetic sensor cells 220 in one magnetic sensor cell 220 group. That is, the magnetic field measuring device 10 generates a calibration magnetic field while sequentially switching a part of the magnetic sensor cells 220 in the first magnetic sensor cell 220 group, and targets the sensor unit 300 in the second magnetic sensor cell 220 group to have a sensor error. May be calibrated sequentially. Similarly, the magnetic field measuring device 10 generates a calibration magnetic field while sequentially switching a part of the magnetic sensor cells 220 in the second magnetic sensor cell 220 group, and targets the sensor unit 300 in the first magnetic sensor cell 220 group as a sensor. The errors may be calibrated sequentially.

Further, in the above description, the case where the magnetic field measuring device 10 classifies the plurality of magnetic sensor cells 220 in the magnetic sensor array 210 into two groups is shown as an example, but the present invention is not limited to this. The magnetic field measuring device 10 may classify the plurality of magnetic sensor cells 220 in the magnetic sensor array 210 into three groups, for example. For example, the magnetic field measuring device 10 has a plurality of magnetic sensor cells 220 in the magnetic sensor array 210, the first magnetic sensor cell 220 group located on the left side when viewed from the measured object, and the second magnetic sensor cell 220 located on the right side when viewed from the measured object. The magnetic sensor cell 220 group may be classified into a third magnetic sensor cell 220 group located between the first magnetic sensor cell 220 group and the second magnetic sensor cell 220 group. Then, the magnetic field measuring device 10 generates a calibration magnetic field while sequentially switching the magnetic sensor cells 220 of the first magnetic sensor cell 220 group, and the sensor unit 300 in the second magnetic sensor cell 220 group and the third magnetic sensor cell 220 group. The sensor error may be calibrated sequentially. Similarly, the magnetic field measuring device 10 generates a calibration magnetic field while sequentially switching the magnetic sensor cells 220 of the second magnetic sensor cell 220 group, and the sensor unit in the first magnetic sensor cell 220 group and the third magnetic sensor cell 220 group. The sensor error may be sequentially calibrated for 300. That is, the magnetic field measuring device 10 generates a calibration magnetic field while sequentially switching the sensor unit 300 in the third magnetic sensor cell 220 group and the magnetic sensor cell 220 in the first magnetic sensor cell 220 group, and the second magnetism. In both the case where the magnetic sensor cell 220 of the sensor cell 220 group is sequentially switched and the calibration magnetic field is generated, it may be an overlapping calibration target.

FIG. 17 geometrically shows a signal space separation operation using _{the calibrated basis vector [AB} ] Calib when the magnetic sensor array 210 is made with sensor error. In FIG. 17, members having the same functions and configurations as those in FIG. 14 are designated by the same reference numerals, and the description thereof will be omitted except for the following differences. According to the flow of FIG. 16, the magnetic field measuring device 10 updates the basis vector. Here, reference numeral 1720 indicates a linear subspace Span {A _Calib } _{stretched by the calibrated basis vector A Calib. Reference} numeral 1730 indicates a linear subspace Span {B _Calib } stretched by the calibrated basis vector B Calib. _Reference numeral 1740 indicates a linear subspace stretched by a _{basis vector [AB] Calib which} is a linear sum of the linear subspace Span {A Calib} and the linear subspace Span {B _Calib}. Reference numeral 1750 indicates an M-dimensional vector of a minimum squared solution. As shown in this figure, the sensor array signal Φ _Uncalib of the magnetic sensor array 210 with sensor error exists in a linear subspace stretched by the calibrated basis vector [ _{AB] Calib.} That is, the signal space separation unit 1160 optimizes the base vector so as to minimize the separation error, so that the signal space distribution is applied to the target magnetic field component and the disturbance magnetic field component with respect to the magnetic field detected by the magnetic sensor array 210. Can be done accurately.

In the above description, an example is obtained in which the magnetic field measuring device 10 changes the basis vector so as to minimize the separation error by optimizing _{the magnetic sensitivity vector S Calib [m] as a calibration parameter.} Shown as. However, as described above, as the sensor error, in addition to the magnetic sensitivity error of each sensor, a position error due to a deviation of the arrangement position of each sensor at the time of assembling the magnetic sensor array 210 may occur. Therefore, the magnetic field measuring device 10 _{replaces or in addition to the magnetic sensitivity vector S Calib} [m] as a calibration parameter, and position information in the magnetic sensors 520 of the M sensor units 300, in this case, signal space separation. The base vector may be changed so as to minimize the separation error by optimizing the position information in the calculated coordinate system of, that is, the radius r, the zenith angle θ, and the azimuth angle φ, respectively. That is, the basis vector may be changed with r, θ, and φ in (Equation 19) as calibration parameters. The magnetic field measuring device 10 can also realize such calibration of the position error by the same method as the calibration of the magnetic sensitivity error. Further, the magnetic field measuring device 10 may perform an operation so as to optimize the calibration of the magnetic sensitivity error and the calibration of the position error at the same time.

Further, in the above description, the case where the magnetic field measuring device 10 measures the magnetic field to be measured after performing the calibration is shown as an example. However, for example, when the frequency of the AC magnetic field as the calibration magnetic field is higher than the frequency band of the magnetic field to be measured, the magnetic field measuring device 10 may execute the calibration and the measurement of the magnetic field to be measured at the same time. good. In this case, the magnetic field measuring device 10 may frequency-separate the calibration magnetic field signal and the measurement target magnetic field signal by using LPF, HPF, or the like.

Various embodiments of the present invention may be described with reference to flowcharts and block diagrams, wherein the block is (1) a stage of the process in which the operation is performed or (2) a device responsible for performing the operation. May represent a section of. Specific stages and sections are implemented by dedicated circuits, programmable circuits supplied with computer-readable instructions stored on computer-readable media, and / or processors supplied with computer-readable instructions stored on computer-readable media. You can. Dedicated circuits may include digital and / or analog hardware circuits, and may include integrated circuits (ICs) and / or discrete circuits. Programmable circuits are memory elements such as logical AND, logical OR, logical XOR, logical NAND, logical NOR, and other logical operations, flip-flops, registers, field programmable gate arrays (FPGA), programmable logic arrays (PLA), etc. May include reconfigurable hardware circuits, including, etc.

The computer readable medium may include any tangible device capable of storing instructions executed by the appropriate device, so that the computer readable medium having the instructions stored therein is specified in a flowchart or block diagram. It will be equipped with a product that contains instructions that can be executed to create means for performing the operation. Examples of computer-readable media may include electronic storage media, magnetic storage media, optical storage media, electromagnetic storage media, semiconductor storage media, and the like. More specific examples of computer-readable media include floppy (registered trademark) disks, diskettes, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), Electrically erasable programmable read-only memory (EEPROM), static random access memory (SRAM), compact disc read-only memory (CD-ROM), digital versatile disc (DVD), Blu-ray (RTM) disc, memory stick, integrated A circuit card or the like may be included.

Computer-readable instructions are assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state-setting data, or object-oriented programming such as Smalltalk, JAVA®, C ++, etc. Contains either source code or object code written in any combination of one or more programming languages, including languages and traditional procedural programming languages such as the "C" programming language or similar programming languages. good.

Computer-readable instructions are applied locally to a general purpose computer, a special purpose computer, or the processor or programmable circuit of another programmable data processor, or a wide area network (WAN) such as a local area network (LAN), the Internet, etc. ) May be executed to create a means for performing the operation specified in the flowchart or block diagram. Examples of processors include computer processors, processing units, microprocessors, digital signal processors, controllers, microcontrollers and the like.

FIG. 18 shows an example of a computer 2200 in which a plurality of aspects of the present invention may be embodied in whole or in part. The program installed on the computer 2200 can cause the computer 2200 to function as an operation associated with the device according to an embodiment of the present invention or as one or more sections of the device, or the operation or the one or more. Sections can be run and / or the computer 2200 can be run a process according to an embodiment of the invention or a stage of such process. Such a program may be run by the CPU 2212 to cause the computer 2200 to perform certain operations associated with some or all of the blocks in the flowcharts and block diagrams described herein.

The computer 2200 according to this embodiment includes a CPU 2212, a RAM 2214, a graphic controller 2216, and a display device 2218, which are interconnected by a host controller 2210. The computer 2200 also includes input / output units such as a communication interface 2222, a hard disk drive 2224, a DVD-ROM drive 2226, and an IC card drive, which are connected to the host controller 2210 via the input / output controller 2220. There is. The computer also includes legacy input / output units such as the ROM 2230 and keyboard 2242, which are connected to the input / output controller 2220 via an input / output chip 2240.

The CPU 2212 operates according to the programs stored in the ROM 2230 and the RAM 2214, thereby controlling each unit. The graphic controller 2216 acquires the image data generated by the CPU 2212 in a frame buffer or the like provided in the RAM 2214 or itself so that the image data is displayed on the display device 2218.

The communication interface 2222 communicates with other electronic devices via the network. The hard disk drive 2224 stores programs and data used by the CPU 2212 in the computer 2200. The DVD-ROM drive 2226 reads the program or data from the DVD-ROM 2201 and provides the program or data to the hard disk drive 2224 via the RAM 2214. The IC card drive reads programs and data from the IC card and / or writes programs and data to the IC card.

The ROM 2230 contains a boot program or the like executed by the computer 2200 at the time of activation, and / or a program depending on the hardware of the computer 2200. The input / output chip 2240 may also connect various input / output units to the input / output controller 2220 via a parallel port, serial port, keyboard port, mouse port, and the like.

The program is provided by a computer-readable medium such as a DVD-ROM2201 or an IC card. The program is read from a computer-readable medium, installed on a hard disk drive 2224, RAM 2214, or ROM 2230, which is also an example of a computer-readable medium, and executed by the CPU 2212. The information processing described in these programs is read by the computer 2200 and provides a link between the program and the various types of hardware resources described above. The device or method may be configured to perform manipulation or processing of information in accordance with the use of computer 2200.

For example, when communication is executed between the computer 2200 and an external device, the CPU 2212 executes a communication program loaded in the RAM 2214, and performs communication processing on the communication interface 2222 based on the processing described in the communication program. You may order. Under the control of the CPU 2212, the communication interface 2222 reads and reads transmission data stored in a transmission buffer processing area provided in a recording medium such as a RAM 2214, a hard disk drive 2224, a DVD-ROM 2201, or an IC card. The data is transmitted to the network, or the received data received from the network is written to the reception buffer processing area or the like provided on the recording medium.

Further, the CPU 2212 causes the RAM 2214 to read all or necessary parts of a file or database stored in an external recording medium such as a hard disk drive 2224, a DVD-ROM drive 2226 (DVD-ROM2201), or an IC card. Various types of processing may be performed on the data on the RAM 2214. The CPU 2212 then writes back the processed data to an external recording medium.

Various types of information, such as various types of programs, data, tables, and databases, may be stored on the recording medium and processed. The CPU 2212 describes various types of operations, information processing, conditional judgment, conditional branching, unconditional branching, and information retrieval described in various parts of the present disclosure with respect to the data read from the RAM 2214. Various types of processing may be performed, including / replacement, etc., and the results are written back to RAM 2214. Further, the CPU 2212 may search for information in a file, a database, or the like in the recording medium. For example, when a plurality of entries each having an attribute value of the first attribute associated with the attribute value of the second attribute are stored in the recording medium, the CPU 2212 specifies the attribute value of the first attribute. Search for an entry that matches the condition from the plurality of entries, read the attribute value of the second attribute stored in the entry, and associate it with the first attribute that satisfies the predetermined condition. The attribute value of the second attribute obtained may be acquired.

The program or software module described above may be stored on or near computer 2200 on a computer-readable medium. Also, a recording medium such as a hard disk or RAM provided in a dedicated communication network or a server system connected to the Internet can be used as a computer readable medium, thereby providing the program to the computer 2200 over the network. do.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various changes or improvements can be made to the above embodiments. It is clear from the description of the claims that such modified or improved forms may also be included in the technical scope of the present invention.

The order of execution of operations, procedures, steps, steps, etc. in the devices, systems, programs, and methods shown in the claims, specification, and drawings is particularly "before" and "prior to". It should be noted that it can be realized in any order unless the output of the previous process is used in the subsequent process. Even if the scope of claims, the specification, and the operation flow in the drawings are explained using "first", "next", etc. for convenience, it means that it is essential to carry out in this order. It's not a thing.

10 Magnetic field measuring device 100 Main body 110 Magnetic sensor unit 120 Head 125 Drive unit 130 Base unit 140 Pole unit 150 Information processing unit 210 Magnetic sensor array 220 Magnetic sensor cell 230 Sensor data collection unit 232 AD converter 234 Clock generator 300 Sensor unit 520 Magnetic sensor 530 Magnetic field generator 532 Amplification circuit 534 Feedback coil 540 Output unit 710 Magnetic resistance element 720, 730 Magnetic convergence plate 1010 Switching unit 1100 Sensor data processing unit 1120 Measurement data acquisition unit 1130 Synchronous detection unit 1140 Data output unit 1150 Base vector storage Part 1160 Signal space separation part 1170 Calibration clock generation part 1180 Error calculation part 1190 Calibration part 2200 Computer 2201 DVD-ROM
2210 Host controller 2212 CPU
2214 RAM
2216 Graphic controller 2218 Display device 2220 Input / output controller 2222 Communication interface 2224 Hard disk drive 2226 DVD-ROM drive 2230 ROM
2240 Input / Output Chip 2242 Keyboard

Claims (15)

It has a curved surface shape that is curved in at least one direction, and each reduces the input magnetic field detected by the magnetic sensor with a magnetic sensor, an output unit that outputs an output signal, and a size corresponding to the output signal. A plurality of magnetic sensor cells having a magnetic field generator for generating a feedback magnetic field are arranged three-dimensionally so as to be arranged at lattice points included in the curved surface shape, and magnetism capable of detecting an input magnetic field in three axial directions. With the sensor array
A measurement data acquisition unit that acquires measurement data measured by the magnetic sensor array,
A vector signal having signals output by each of the magnetic sensors as signal components when the spatial distribution of the input magnetic field indicated by the measurement data is detected by the magnetic sensor array when a magnetic field having a spatial distribution of a normal orthogonal function is detected by the magnetic sensor array. A signal space separator that separates signals using
The sensor error in the magnetic sensor is calibrated based on the separation error when the spatial distribution of the calibration magnetic field generated from the magnetic field generation unit of at least one of the plurality of magnetic sensor cells is signal-separated. A magnetic field measuring device equipped with a calibration unit. The magnetic field measuring device according to claim 1, wherein the output unit outputs the output signal according to the feedback current that the magnetic field generating unit flows to generate the feedback magnetic field. Each of the magnetic sensors includes a magnetoresistive element and two magneto-convergent plates arranged at both ends of the magnetoresistive element, and the magnetoresistive element is arranged at a position sandwiched between the two magnetic converging plates. The magnetic field measuring device according to claim 2. 3. The magnetic field generating unit includes a feedback coil wound along the axial direction of the magnetic field to be detected by the magnetic sensor so as to surround the magnetoresistive element and the two magnetic focusing plates. The magnetic field measuring device described. The magnetic field according to any one of claims 1 to 4, wherein the calibration unit calibrates the sensor error in the magnetic sensor based on the separation error when the at least one magnetic sensor cell is sequentially switched. Measuring device. The magnetic sensor array is configured by arranging the plurality of magnetic sensor cells three-dimensionally in a cross-sectional view arc shape.
The calibration unit calibrates the sensor error in the magnetic sensor based on the separation error when the at least one magnetic sensor cell is sequentially switched over a plurality of magnetic sensor cells forming an inner arc. 5. The magnetic field measuring device according to 5. The method according to any one of claims 1 to 6, wherein the at least one magnetic sensor cell further includes a switching unit for switching whether the magnetic field generation unit generates the feedback magnetic field or the calibration magnetic field. Magnetic field measuring device. The signal space separation unit uses the position where the magnetic field generation unit of at least one magnetic sensor cell is arranged as the origin of coordinates in the calculation when the spatial distribution of the calibration magnetic field is signal-separated. 7. The magnetic field measuring device according to any one of 7. The magnetic field measuring device according to any one of claims 1 to 8, wherein the calibration unit calibrates the sensor error by changing the basis vector. The magnetic field measuring device according to claim 9, wherein the calibration unit optimizes the basis vector so as to minimize the separation error. The magnetic field measuring device according to any one of claims 1 to 10, further comprising a synchronous detection unit that detects the calibration magnetic field, which is an AC magnetic field, using a signal having a frequency of the AC magnetic field. The magnetic field measuring device according to claim 11, wherein the frequency of the AC magnetic field is higher than the frequency band of the magnetic field to be measured. It has a curved shape curved in at least one direction, and each has a magnetic sensor, an output unit that outputs an output signal, and feedback that reduces the input magnetic field detected by the magnetic sensor with a size corresponding to the output signal. A magnetic sensor capable of detecting an input magnetic field in three axes, which is configured by arranging a plurality of magnetic sensor cells having a magnetic field generator for generating a magnetic field in three dimensions so as to be arranged at lattice points included in the curved surface shape. Acquiring the measurement data measured by the array and
A vector signal having signals output by each of the magnetic sensors as signal components when the spatial distribution of the input magnetic field indicated by the measurement data is detected by the magnetic sensor array with a magnetic field having a spatial distribution of a normal orthogonal function. To separate signals using
To generate a calibration magnetic field from the magnetic field generation unit of at least one of the plurality of magnetic sensor cells.
A magnetic field measurement method comprising calibrating a sensor error in the magnetic sensor based on a separation error when the spatial distribution of the calibration magnetic field is signal-separated. Performed by a computer, said computer,
It has a curved shape curved in at least one direction, and each has a magnetic sensor, an output unit that outputs an output signal, and feedback that reduces the input magnetic field detected by the magnetic sensor with a size corresponding to the output signal. A magnetic sensor capable of detecting an input magnetic field in three axes, which is configured by arranging a plurality of magnetic sensor cells having a magnetic field generator for generating a magnetic field in three dimensions so as to be arranged at lattice points included in the curved surface shape. A measurement data acquisition unit that acquires measurement data measured by an array,
A vector signal having signals output by each of the magnetic sensors as signal components when the spatial distribution of the input magnetic field indicated by the measurement data is detected by the magnetic sensor array when a magnetic field having a spatial distribution of a normal orthogonal function is detected by the magnetic sensor array. A signal space separator that separates signals using
The sensor error in the magnetic sensor is calibrated based on the separation error when the spatial distribution of the calibration magnetic field generated from the magnetic field generation unit of at least one of the plurality of magnetic sensor cells is signal-separated. A magnetic field measurement program that functions as a calibrator. Each has a magnetic sensor, an output unit that outputs an output signal, and a magnetic field generator that generates a feedback magnetic field that reduces the input magnetic field detected by the magnetic sensor with a size corresponding to the output signal. A magnetic sensor array that is configured by arranging magnetic sensor cells in three dimensions and can detect an input magnetic field in three axial directions.
A measurement data acquisition unit that acquires measurement data measured by the magnetic sensor array,
A vector signal having signals output by each of the magnetic sensors as signal components when the spatial distribution of the input magnetic field indicated by the measurement data is detected by the magnetic sensor array when a magnetic field having a spatial distribution of a normal orthogonal function is detected by the magnetic sensor array. A signal space separator that separates signals using
The sensor error in the magnetic sensor is calibrated based on the separation error when the spatial distribution of the calibration magnetic field generated from the magnetic field generation unit of at least one of the plurality of magnetic sensor cells is signal-separated. A magnetic field measuring device equipped with a calibration unit.

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