JP2020148760A - measuring device - Google Patents

Abstract

To compose a device simply at low cost that detects a weak magnetic field with good accuracy.SOLUTION: Provided is a measuring device comprising: a magnetic sensor array constituted by three-dimensionally arranging a plurality of magnetic sensor cells, each including a magnetic sensor, and capable of detecting an input magnetic field in three axis directions; a measured data acquisition unit for acquiring a plurality of measured values based on the input magnetic field detected by the magnetic sensor array; a magnetic field calculation unit for calculating an input magnetic field on the basis of the plurality of measured values; an error calculation unit for calculating a magnetic field detection error on the basis of the plurality of measured values and the calculation result of input magnetic field calculation; and a measured data selection unit for selecting, on the basis of the detection error, a plurality of measured values, from among the plurality of measured values, that are used by the magnetic field calculation unit to calculate an input magnetic field.SELECTED DRAWING: Figure 9

Description

The present invention relates to a measuring device.

Conventionally, a sensor that detects a weak magnetic field of about 10 pT has been known, and has been used in a magnetocardiograph or the like that measures a magnetocardiographic signal caused by electrical polarization of an organ such as the heart (for example, Patent Document 1). See ~ 4). It has also been known that in a current sensor using a magnetoresistive element, a feedback coil is used to cancel the influence of an environmental magnetic field (see, for example, Patent Document 5).
[Prior art literature]
[Patent Document]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2000-217798 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-152515 [Patent Document 3] US Pat. No. 5,642,045 [Patent Document 4] Japanese Patent Application Laid-Open No. 2000-284032 [Patent Document 4] Document 5] U.S. Patent Application Publication No. 2015/0253412

For example, a SQUID sensor using the Josephson effect can detect a weak magnetic field, but it requires expensive liquid helium and a large-scale magnetic shield room, so it is not possible to install a device equipped with the sensor. It wasn't easy. Further, the current sensor using the magnetoresistive element is small and has high magnetic sensitivity, but the linearity of the input / output characteristics is poor. In addition, it has been difficult to accurately detect a weak magnetic field using such a current sensor due to sensitivity errors and fluctuations in sensor characteristics.

In order to solve the above problems, in the first aspect of the present invention, a measuring device is provided. The measuring device may include a magnetic sensor array capable of detecting an input magnetic field in three axial directions, each of which is configured by arranging a plurality of magnetic sensor cells including a magnetic sensor in three dimensions. The measuring device may include a measurement data acquisition unit that acquires a plurality of measured values based on the input magnetic field detected by the magnetic sensor array. The measuring device may include a magnetic field calculation unit that calculates an input magnetic field based on a plurality of measured values. The measuring device may include an error calculation unit that calculates a magnetic field detection error based on a plurality of measured values and calculation results for calculating an input magnetic field. The measuring device may include a measurement data selection unit that selects a plurality of measurement values used for calculating an input magnetic field by the magnetic field calculation unit from a plurality of measurement values based on a detection error.

The error calculation unit calculates the detection error for each of a plurality of measured values, and the measurement data selection unit may select a plurality of measured values by excluding the measured values whose detection error exceeds a predetermined range. ..

The magnetic field calculation unit may recalculate the input magnetic field after excluding the measured values whose detection error exceeds a predetermined range.

The magnetic field calculation unit recalculates the input magnetic field at the location where the plurality of measurement values are measured based on the plurality of measurement values selected by the measurement data selection unit, and the error calculation unit uses the plurality of measurement values. The detection error may be calculated based on the detection result of the input magnetic field at the measured location.

The magnetic field calculation unit calculates the input magnetic field at the point where the excluded measurement value is measured, based on the coefficient related to the calculation result of the input magnetic field calculated from the plurality of measurement values selected by the measurement data selection unit. Good.

Each of the plurality of magnetic sensor cells outputs a magnetic field generator that gives the magnetic sensor a feedback magnetic field that reduces the input magnetic field detected by the magnetic sensor, and an output signal that corresponds to the current that the magnetic field generator flows to generate the feedback magnetic field. It may further include an output unit to be used.

In the second aspect of the present invention, a measuring device is provided. The measuring device may be configured by arranging a plurality of magnetic sensor cells in three dimensions, and may include a magnetic sensor array capable of detecting an input magnetic field in three axial directions. The measuring device may include a measurement data acquisition unit that acquires a plurality of measured values based on the input magnetic field detected by the magnetic sensor array. The measuring device may include a magnetic field calculation unit that calculates an input magnetic field based on a plurality of measured values. The measuring device may include an error calculation unit that calculates a magnetic field detection error based on a plurality of measured values and calculation results for calculating an input magnetic field. The measuring device may include a determination unit that determines whether to reset at least one of the plurality of magnetic sensor cells based on the detection error. Each of the plurality of magnetic sensor cells corresponds to a magnetic sensor, a magnetic field generator that gives the magnetic sensor a feedback magnetic field that reduces the input magnetic field detected by the magnetic sensor, and a current that the magnetic field generator flows to generate the feedback magnetic field. It may include an output unit that outputs an output signal and a magnetic reset unit that applies a reset magnetic field that magnetically saturates the magnetic sensor to the magnetic sensor when the magnetic sensor cell is reset.

The error calculation unit calculates the detection error for each of a plurality of measured values, and the determination unit determines to reset the magnetic sensor cell including the magnetic sensor used to acquire the measured value whose detection error exceeds a predetermined range. You can do it.

The magnetic field calculation unit may recalculate the input magnetic field after the magnetic sensor used for acquiring the measured value whose detection error exceeds a predetermined range is magnetically reset.

The magnetic reset unit includes a switching unit that switches whether or not to supply a feedback current that generates a feedback magnetic field to the magnetic field generation unit, and supplies a reset current to the magnetic field generation unit in a state where the feedback current is not supplied to the magnetic field generation unit. It may be supplied to generate a reset magnetic field in the magnetic field generator.

The magnetic field calculation unit may calculate the input magnetic field so that the square of the detection error is minimized.

The magnetic field calculation unit is a signal whose component is a signal output by each of the magnetic sensors when the spatial distribution of the input magnetic field indicated by a plurality of measured values is detected by the magnetic sensor array when the magnetic field having the spatial distribution of the normal orthogonal function is detected. The signal may be separated using the vector as the base vector, and the error calculation unit may calculate the detection error based on the result of the signal separation by the magnetic field calculation unit.

A basis vector update unit that updates the basis vector based on the detection error may be further provided.

The magnetic sensor may have a magnetoresistive element.

Each of the magnetic sensors further has 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.

A coil for generating a feedback magnetic field may be wound around a magnetoresistive element and two magnetic focusing plates.

A plurality of AD converters that convert the outputs of a plurality of magnetic sensor cells from analog to digital and output a plurality of measured values may be further provided, and the plurality of AD converters may perform AD conversion according to a common sampling clock. ..

The magnetocardiography generated by the electrical activity of the heart of an animal may be measured, and the magnetocardiography may be measured based on the calculation result of the magnetic field calculation unit.

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

The configuration of the 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 and arrangement of the magnetic sensor cells 220 in the magnetic sensor array 210 according to the present embodiment are 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. The configuration of the magnetic sensor array 210, the sensor data collection unit 230, and the sensor data processing unit 900 according to the present embodiment is shown. An example of a flow in which the measurement device 10 according to the present embodiment excludes the measurement value by the defective sensor as the preprocessing for detecting the magnetic field to be measured is shown. The configuration of the sensor unit 300 according to the modified example of this embodiment is shown. An example of the magnetic reset flow in the reset phase by the sensor unit 300 according to this modification is shown. The magnetization curve of a general magnetic material is shown. The characteristics of the voltage Vopen with respect to the input magnetic field Bin to the magnetic sensor 520 in the sensor unit 300 according to this modification are shown. The configuration of the magnetic sensor array 210, the sensor data collection unit 230, and the sensor data processing unit 900 when each of the plurality of magnetic sensor cells 220 has the sensor unit 300 according to this modification is shown. An example of a flow in which a measuring device 10 having a sensor unit 300 according to this modification in each of the plurality of magnetic sensor cells 220 resets a defective sensor as a preprocessing for detecting a magnetic field to be measured is 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 claimed in 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 measuring device 10 according to the present embodiment. The measuring device 10 measures the magnetic field using the magnetoresistive element. The measuring device 10 is an example of a magnetocardiographic measuring device, and measures a magnetic field (referred to as “magnetocardiography”) generated by the electrical activity of the human heart. Instead, the measuring device 10 may be used to measure the magnetocardiography of a living body other than a human being, or may be used to measure a biomagnetic field other than the magnetocardiography such as a brain magnetic field. Further, the measuring device 10 may be used for a magnetic particle inspection for detecting scratches on the surface and under the surface of a steel material or a welded portion.

The measuring device 10 includes a main body unit 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. 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 around the X-axis center 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 measurement data 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 in which a plurality of computers are connected. Instead of this, the information processing unit 150 may be a dedicated computer designed for information processing of magnetocardiographic measurement, or may be 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 has a magnetic sensor array 210 and a sensor data collection unit 230. The magnetic sensor array 210 is configured by arranging a plurality of magnetic sensor cells 220 in three dimensions, and can detect an input magnetic field in three axial directions. In this figure, the magnetic sensor array 210 has a plurality of magnetic sensor cells 220 in each of the X direction, the Y direction, and the Z direction (for example, eight in the X direction, eight in the Y direction, and two in the Z direction, for a total of 128). The magnetic sensor cells 220) are arranged in a plane.

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 and arrangement of the magnetic sensor cells 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 having 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 three axial directions. Good. 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 effect element. Therefore, each sensor unit 300 clearly determines the sampling points in space in each axial direction by sampling the spatial distribution of the magnetic field using the magnetoresistive effect element arranged at a narrow position sandwiched between the magnetic focusing plates. can do. Details of the configuration of each sensor unit 300 will be described later.

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 axial direction in the three axial directions so as to be separated from the gap. 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, 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 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.

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) effect element or a tunnel magneto-resistance (TMR) effect element, and has a predetermined magnitude of a magnetic field in a uniaxial direction. To detect.

Such a magnetic sensor has a high magnetic sensitivity, which is the slope 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, the first amplifier circuit 532 and the output unit 540 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 sensor 520 includes a magnetoresistive element and two magnetic focusing plates arranged at both ends of the magnetic resistance effect element, and the magnetoresistive element is located at a position sandwiched between the two magnetic focusing plates. Be placed. The magnetoresistive sensor of the magnetic sensor 520 has a resistance value that increases when a magnetic field in the + X direction is input, and a resistance value 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 decrease. That is, the magnitude of the magnetic field B input to the magnetic sensor 520 can be detected by observing the change in the resistance value of the magnetoresistive element of the magnetic sensor 520. 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 it to the magnetic sensor 520. The magnetic field generation unit 530, for example, generates a feedback magnetic field B_FB whose absolute value is substantially the same as that of 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 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 sensor 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 each input terminal pair of the amplifier circuit 532. 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 coil 534 generates a feedback magnetic field B_FB corresponding to the feedback current I_FB. The 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 and the two magnetic focusing plates arranged at both ends of the magnetoresistive element. It has been done. It is desirable that the coil 534 generate a uniform feedback magnetic field B_FB throughout the magnetic sensor 520. For example, assuming that the coil coefficient of the 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 first 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 sensor having the non-linearity shown in FIG. 4 as the magnetic sensor 520 and having a narrow operating magnetic field range, and the absolute value of the input magnetic field B exceeds 1 μT. Also, 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 core magnetic 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 magnetoresistive 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 magnetoresistive axis. Has been done. 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 of the magnetically sensitive shaft toward the positive side, 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 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. As described above, 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 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 point in the space is clarified by sampling the spatial distribution of the magnetic field using the magnetic resistance effect element 710 arranged at a narrow position sandwiched between the magnetic focusing plates 720 and 730. be able to.

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, the 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 coil 534, the 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 magnetic resistance effect element 710 and magnetically amplified by the magnetic focusing plates 720 and 730. Therefore, as shown in this figure, the magnetic sensor 520 has magnetic convergence plates 720 and 730 arranged at both ends of the magnetic resistance effect element 710, and includes the magnetic resistance effect element and the magnetic convergence plates arranged at both ends thereof. When the coil 534 is wound so as to surround the set with one coil, the magnetic field distribution at the position of the magnetic resistance effect element 710 can be accurately canceled by the feedback magnetic field, so that the input magnetic field and the output voltage It is possible to realize a sensor with high linearity between them.

FIG. 9 shows the configurations of the magnetic sensor array 210, the sensor data collection unit 230, and the sensor data processing unit 900 according to the present embodiment.

The magnetic sensor array 210 has a plurality of magnetic sensor cells 220. Each of the plurality of magnetic sensor cells 220 may have a plurality of sensor units 300x to z as described above. In this figure, among the plurality of magnetic sensor cells 220 that the magnetic sensor array 210 has in each dimensional direction, the positions [i, j, k], [i + 1, j, k], [i, j + 1, k], and The part related to [i, j, k + 1] is shown.

The sensor data collection 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 300x to z of the magnetic sensor cell 220, and an analog detection signal (sensor output signal V_xMR in FIG. 6) output by the corresponding sensor unit 300 is provided. ) Is converted into digital measured values V (Vx, Vy, Vz) and a plurality of measured values are output. Here, Vx, Vy, and Vz are measured values (for example, digital voltage values) obtained by converting the detection signals from the sensor units 300x, 300y, and 300z into digital, 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 300x to z provided at different positions all perform the synchronous operation. As a result, the plurality of AD converters 232 can simultaneously sample the detection results of the plurality of sensor units 300x to z provided in different spaces.

The sensor data processing unit 900 includes a measurement data acquisition unit 910, a measurement data selection unit 920, a magnetic field calculation unit 930, a basis vector storage unit 940, and an error calculation unit 950.

The measurement data acquisition unit 910 acquires a plurality of measured values based on the input magnetic field detected by the magnetic sensor array 210. The measurement data acquisition unit 910 is connected to a plurality of AD converters 232 and acquires a plurality of measured values measured by the sensor units 300x to z in the plurality of magnetic sensor cells 220 constituting the magnetic sensor array 210. Specifically, the measurement data acquisition unit 910 is configured by using a flip-flop or the like that latches the measured values V (Vx, Vy, Vz) digitally converted by the plurality of AD converters 232 at a predetermined timing T. Good. The measurement data acquisition unit 910 supplies the acquired plurality of measurement values to the measurement data selection unit 920 as measurement data Φ _All .

The measurement data selection unit 920 uses a plurality of measurements used by the magnetic field calculation unit 930 to calculate an input magnetic field from a plurality of measurement values supplied from the measurement data acquisition unit 910 based on a magnetic field detection error described later. Select a value. Then, the measurement data selection unit 920 supplies the selected plurality of measurement values to the magnetic field calculation unit 930 as measurement data Φ _Select .

The magnetic field calculation unit 930 calculates the input magnetic field based on a plurality of measured values selected as the measurement data Φ _Select by the measurement data selection unit 920. When the magnetocardiography generated by the electrical activity of the heart of an animal is to be measured, the magnetocardiography may be measured based on the calculation result of the magnetic field calculation unit 930. At this time, the magnetic field calculation unit 930 may calculate the input magnetic field so that the square of the detection error of the magnetic field is minimized. Further, the magnetic field calculation unit 930 outputs a signal output by each of the magnetic sensors 520 when the magnetic field sensor array 210 detects a magnetic field having a spatial distribution of a normal orthogonal function with respect to the spatial distribution of the input magnetic field indicated by a plurality of measured values. The signal vector having the above as a component may be used as the base vector for signal separation. This will be described later. The magnetic field calculation unit 930 supplies the calculation result of calculating the input magnetic field to the error calculation unit 950 together with a plurality of measured values.

The basis vector storage unit 940 stores the basis vector used by the magnetic field calculation unit 930 for signal separation of the spatial distribution of the input magnetic field, and supplies the stored basis vector to the magnetic field calculation unit 930. The magnetic field calculation unit 930 may use the basis vector supplied from the basis vector storage unit 940 when signal-separating the spatial distribution of the input magnetic field.

The error calculation unit 950 calculates the magnetic field detection error ε based on the calculation results obtained by calculating the plurality of measured values and the input magnetic fields supplied from the magnetic field calculation unit 930. This will also be described later. The error calculation unit 950 supplies the calculated magnetic field detection error ε to the measurement data selection unit 920. Then, as described above, the measurement data selection unit 920 uses the magnetic field calculation unit 920 to select the magnetic field from the plurality of measurement values supplied from the measurement data acquisition unit 910 based on the detection error ε of the magnetic field supplied from the error calculation unit 950. A plurality of measured values used to calculate the input magnetic field by 930 are selected.

FIG. 10 shows an example of a flow in which the measuring device 10 according to the present embodiment excludes the measured value by the defective sensor as a preprocessing for calculating the magnetic field to be measured.

In step 1010, the measuring device 10 makes initial settings. For example, N is the total number of the plurality of sensor units 300x to z in the plurality of magnetic sensor cells 220 constituting the magnetic sensor array 210, that is, the total number of the plurality of measurement values included in the measurement data Φ _All , and M is the measurement data Φ. Assuming that the total number of the plurality of measured values included in _Select is the total number, the measuring device 10 sets M = N. That is, the measuring device 10 is initially set so that all of the plurality of measured values are the measured data Φ _Select .

Next, in step 1020, the measuring device 10 calculates the input magnetic field. For example, the measurement data acquisition unit 910 acquires a plurality of measurement values (measurement data Φ _All ) based on the input magnetic field measured by the sensor units 300x to z in the plurality of magnetic sensor cells 220 constituting the magnetic sensor array 210. Then, the measurement data selection unit 920 selects all of the plurality of measured values as the measurement data Φ _Select in the step 1020 following the step 1010. (Φ _Select = Φ _All ). Then, the magnetic field calculation unit 930 calculates the input magnetic field based on a plurality of measured values selected as the measurement data Φ _Select .

In calculating the input magnetic field, the magnetic field calculation unit 930 detects, for example, the spatial distribution of the input magnetic field indicated by a plurality of measured values by the magnetic sensor array 210 when the magnetic field having the spatial distribution of the normal orthogonal function is detected. Signal separation is performed using a signal vector whose component is a signal output by each of the 520s as a base vector. The orthonormal function may be, for example, a spherical harmonics. As an example, the base vector storage unit 940 uses a magnetic field signal vector obtained by spatially sampling a spherical harmonic when a predetermined point in space is specified as a coordinate origin before measuring the magnetic field to be measured as a base vector. Remember. Here, the spherical harmonics are functions obtained by limiting the homogeneous polynomial that is the solution of the n-dimensional Laplace equation to the unit sphere, and have normal orthogonality on the sphere. The basis vector storage unit 940 may store a signal vector predetermined based on a simulation result or the like as a basis vector.

The magnetic field calculation unit 930 acquires the signal vector stored as the basis vector by the basis vector storage unit 940 from the basis vector storage unit 940. Then, the magnetic field calculation unit 930 series-expands the spatial distribution of the input magnetic field indicated by the plurality of measured values by using the signal vector as the basis vector. Then, the magnetic field calculation unit 930 signals 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.

Then, the magnetic field calculation unit 930 suppresses the disturbance magnetic field and calculates and outputs only the measurement target magnetic field as a result of signal separation. Hereinafter, this will be described in detail using mathematical formulas.

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

Since the solution of Laplace's equation generally has a solution in the form of series expansion using spherical harmonics Yl, m (θ, φ), which is an orthonormal function system, the potential V (r) is given by the following equation. Can be represented. 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 azimuth quantum number, and m is the magnetic quantum number. Α and β are multipolar moments, and Lin and Lout are the quantum numbers for the space in front of the magnetic sensor array 210 and the space behind the magnetic sensor array 210 as viewed from the coordinate origin and the measurement target, respectively. The azimuth quantum number l takes a positive integer, and the magnetic quantum number m takes an integer from -1 to +1. 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 single magnetic pole in the magnetic field, the azimuth 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 coordinate origin and the measurement target. 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 coordinate origin and the measurement target.

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 coordinate origin and the measurement target, for example, a magnetic field created by the electrical activity of the heart (measurement target magnetic field). 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 coordinate origin and the measurement target.

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 for example, SNR (signal-to-noise ratio, that is, disturbance) sufficient to measure the biomagnetic field. It suffices if the ratio of the magnetic field signal to be measured to the magnetic field and the sensor noise) can be obtained, 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, in the measuring device 10 of the present embodiment, which may be used as a magnetocardiogram, for example, 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, al, m and bl, m are defined as the following equations, where K is a calibration coefficient matrix representing the error of each sensor included in the magnetic sensor array 210. That is, for an M-dimensional vector having M components equal to the number of sensors included in the magnetic sensor array 210 obtained from the gradient of the spherical harmonic function Yl, m (θ, φ) with al, m and bl, m. , The calibration coefficient matrix K for correcting the magnetic sensitivity error of the magnetic sensor 520 included in the magnetic sensor array 210 is multiplied to obtain a base vector for which the magnetic sensitivity error of the magnetic sensor array 210 is corrected.

Then, the measurement data Φ _{Select at} a certain time can be expressed by the following equation.

Further, Sin, Sout, Xin, and Xout are defined as follows. That is, the vectors of the total Lin · (Lin + 2) columns in which the vectors a when Sin is taken as an integer from l = 1 to l = Lin and m = −l to l in each l are arranged in order. Is defined as. Further, the vectors of the total Lout · (Lout + 2) columns in which the vectors b when Sout is taken as an integer from m = −l to l in each l from l = 1 to L = Lout are arranged in order. Is defined as. 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 = -1 to l is taken in order from l = 1 to l = Lin, and each l is transposed. It is defined as a vector of (Lout + 2) rows.

Then, the valid measurement data Φ _Select can be expressed in the form of the inner product of the matrix S and the vertical vector X as shown in the following equation. Here, the matrix S shows a matrix obtained by arranging a total of Lin · (Lin + 2) + Lout · (Lout + 2) basis vectors in the horizontal direction. For example, the magnetic field calculation unit 930 acquired the basis vector storage unit 940. It is a thing. Further, the (Lin · (Lin + 2) + Lout · (Lout + 2)) dimensional vertical vector X indicates the coefficient of the linear combination related to the basis vector.

Based on the model formula of the measurement data Φ _Select obtained in this (Equation 10), the magnetic field calculation unit 930 uses the following equation to use the vertical vector ^ X (where “^ X” is the left side in (Equation 11). , Which means the hat (estimated value) of X.).

At this time, the magnetic field calculation unit 930 uses the least squares method to determine the vertical vector ^ X so as to minimize the cost function F shown in the following equation. As a result, the magnetic field calculation unit 930 can solve the spatial distribution of the magnetic field.

Here, with respect to the vertical vector ^ X determined by the magnetic field calculation unit 930 using (Equation 11) and (Equation 12), ^ Xin / Sin represents the magnetic field component (magnetocardiography) to be measured, and ^ Xout / Sout is disturbance. Represents the magnetic field component. Therefore, in order to eliminate the disturbance magnetic field component and extract only the magnetic field component to be measured, only ^ Xin / Sin of the magnetic field detection results ^ X / S may be extracted.

As a result, the magnetic field calculation unit 930 is configured by arranging a plurality of magnetic sensor cells 220 in three dimensions, and is indicated by measurement data Φ _Select measured using a magnetic sensor array 210 capable of detecting an input magnetic field in three axial directions. The spatial distribution of the magnetic field to be measured can be signal-separated into the magnetic field to be measured and the disturbance magnetic field. In this way, the measuring device 10 can suppress the disturbance magnetic field component and extract only the measurement target magnetic field component, so that 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. it can. The magnetic field calculation unit 930 supplies the calculation result of calculating the input magnetic field to the error calculation unit 950 together with a plurality of measured values.

In step 1030, the error calculation unit 950 calculates the magnetic field detection error ε based on the calculation results obtained by calculating the plurality of measured values and the input magnetic fields supplied from the magnetic field calculation unit 930. The error calculation unit 950 may calculate the detection error ε by subtracting the inner product of the matrix S and the vertical vector ^ X from the measurement data Φ _Select , for example, as shown in the following equation. As a result, the error calculation unit 950 maps the error when the measurement data Φ _Select at a certain time is mapped to the subspace stretched by the basis vector S = [Sin, Sout] using the least squares method, for each component of the vector. And let this be the detection error ε. Therefore, the error calculation unit 950 calculates the detection error ε for each of the plurality of measured values. Then, the error calculation unit 950 supplies the calculated magnetic field detection error ε to the measurement data selection unit 920. Since the number of measured values is M, the detection error ε is a vertical vector of M rows.

In step 1040, the measurement data selection unit 920 determines whether or not the average value of the detection error ε in the entire magnetic sensor array 210, that is, the average value of the detection error ε for each of the plurality of measurement values is equal to or less than a predetermined threshold value. To judge. For example, the measurement data selection unit 920 calculates the average value avg (ε) of the detection error ε by the following equation, and whether or not the average value avg (ε) of the detection error ε is equal to or less than a predetermined threshold value Avg_E_Th. May be determined.

When it is determined in step 1040 that the average value of the detection error ε is equal to or less than a predetermined threshold value, the measuring device 10 ends the process of the flow excluding the measured value by the defective sensor.

On the other hand, when it is determined in step 1040 that the average value of the detection error ε exceeds a predetermined threshold value, in step 1050, the measurement data selection unit 920 determines the detection error ε from a plurality of measured values in advance. Select as a measurement value that excludes measurement values that exceed the above range. As an example, the measurement data selection unit 920 may select the measurement value i excluding the measurement value i that maximizes the absolute value of the detection error ε in the magnetic sensor array 210.

Next, in step 1060, the measurement data selection unit 920 selects a plurality of measured values by excluding the measured values i whose detection error ε exceeds a predetermined range. That is, the measurement data selection unit 920 reconstructs a plurality of measurement values excluding the measurement value i as measurement data Φ _Select .

Then, in step 1070, the measurement data selection unit 920 decrements one dimension of M as a result of excluding the measurement value i, and returns the process to step 1020. Then, the magnetic field calculation unit 930 recalculates the input magnetic field in step 1020 after excluding the measured value i whose detection error ε exceeds a predetermined range. At this time, the magnetic field calculation unit 930 may newly acquire the measured value by using the magnetic sensor array 210, or may reuse the already acquired measured value. The measuring device 10 repeats the process until it is determined in step 1040 that the average value of the detection error ε is equal to or less than a predetermined threshold value.

In the above description, when the measuring device 10 determines that the average value of the detection error ε exceeds a predetermined threshold value, one measured value i having a relatively largest absolute value of the detection error ε is used. The case of excluding and repeating the flow has been described as an example. However, it is not limited to this. The measuring device 10 first selects one measured value i having a relatively largest absolute value of the detection error ε, and the detection error ε in the measured value i, that is, the maximum value of the absolute value of the detection error ε is set in advance. When it is determined that the predetermined threshold is exceeded, the measured value i may be excluded and the flow may be repeated. Further, the measuring device 10 may select a plurality of valid measured values by excluding one or a plurality of measured values i whose absolute value of the detection error ε exceeds a predetermined threshold value.

In this way, before calculating the magnetic field to be measured, the measuring device 10 excludes the measured value i having a large absolute value of the detection error ε, and the magnetic field calculation unit 930 uses the measurement data Φ to calculate the input magnetic field. Update _Select . The measured value i having a large absolute value of the detection error ε corresponds to the sensor in which a large noise is generated. According to the measuring device 10 of the present embodiment, since such a defective sensor having a large noise is excluded before the detection of the magnetic field to be measured, the detection accuracy of the magnetic field to be measured can be improved.

FIG. 11 shows the configuration of the sensor unit 300 according to the modified example of the present embodiment. In this figure, 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.

In this modification, the magnetic sensor 520 has at least one magnetoresistive element. In this figure, as an example, the magnetic sensor 520 includes a first magnetoresistive element 710a and a second magnetoresistive element 710b, and a power supply voltage Vcc, which are connected in series between the power supply voltage Vcc and the ground GND. It has a third magnetoresistive element 710c and a fourth magnetoresistive element 710d connected in series with the ground GND. Although not shown in this figure, the first to fourth magnetoresistive elements 710a to 710d (collectively referred to as “magnetoresistive element 710”) are each magnetic as shown in FIG. It may have magnetoresistive plates 720 and 730 arranged at both ends of the resistance effect element 710. The magnetoresistive element 710 and the magnetic focusing plate may be positioned so as to be included in the coil 534. The magnetic sensor 520 outputs a voltage between the first magnetoresistive element 710a and the second magnetoresistive element 710b and a voltage between the third magnetoresistive element 710c and the fourth magnetoresistive element 710d, respectively. .. In this figure, a bridge circuit is composed of a first magnetoresistive element 710a, a second magnetoresistive element 710b, a third magnetoresistive element 710c, and a fourth magnetoresistive element 710d. However, instead of this, the magnetic sensor 520 is, for example, at least one of the first magnetoresistive element 710a, the second magnetoresistive element 710b, the third magnetoresistive element 710c, and the fourth magnetoresistive element 710d. Is composed of fixed resistors, or one of the first magnetoresistive element 710a and the second magnetoresistive element 710b, and the third magnetoresistive element 710c and the fourth magnetoresistive element 710d is fixed. It may be composed of a voltage source or the like, and includes various aspects of outputting a voltage corresponding to a magnetic field input to at least one magnetoresistive sensor.

The magnetic sensor 520 has at least a first magnetoresistive sensor 710a and a second magnetoresistive element 710b connected in series and having opposite polarities, and the first magnetoresistive element 710a and the second magnetoresistive element 710b. If the configuration is such that the voltage between them is output, the effect of reducing characteristic fluctuations such as offset and sensitivity due to temperature can be obtained. Here, the opposite polarity means that the increasing / decreasing direction of the resistance of the magnetoresistive element is opposite to the input magnetic field in the same direction. In this figure, the third magnetoresistive element 710c has the opposite polarity to the first magnetoresistive element 710a, and the fourth magnetoresistive element 710d has the opposite polarity to the second magnetoresistive element 710b. In addition to the magnetoresistive sensor 710a and the second magnetoresistive element 710b, the third magnetoresistive element 710c and the fourth magnetoresistive element 710d are also shown as having opposite polarities.

In this modification, the amplifier circuit 532 connects the output terminals of the magnetic sensor 520 to the two differential input terminals, respectively. Then, the amplifier circuit 532 generates a feedback current corresponding to the difference in the output voltage of the magnetic sensor 520, and supplies this to the coil 534. Here, the difference between the output voltages of the magnetic sensors 520 is defined as Vopen.

In this modification, the output unit 540 has a current-voltage conversion resistor 542 and an operational amplifier 544.

The current-voltage conversion resistor 542 has one end connected to the coil 534 and the other end connected to a fixed voltage, converts a feedback current into a voltage, and has a voltage based on the feedback current (feedback current × current-voltage conversion resistance) at both ends. 542 resistance value) is generated. Here, the voltage based on the feedback current generated by the current-voltage conversion resistor 542 is defined as Vclosed.

The operational amplifier 544 connects both ends of the current-voltage conversion resistor 542 to the differential input terminal, and outputs the voltage across the current-voltage conversion resistor 542, that is, the voltage corresponding to the voltage Vclosed.

Further, in this modification, the sensor unit 300 further includes a magnetic reset unit 1110. The magnetic reset unit 1110 gives the magnetic sensor 520 a reset magnetic field that magnetically saturates the magnetic sensor 520 in the reset phase. The magnetic reset unit 1110 includes a reset current supply unit 1120 and a switching unit 1130.

In the reset phase, the reset current supply unit 1120 supplies a reset current to the coil 534 to generate a reset magnetic field in the coil 534 that magnetically saturates each magnetoresistive element of the magnetic sensor 520. Note that magnetic saturation means that a certain amount of magnetic field is input to the magnetoresistive sensor and the output of the magnetoresistive sensor does not fluctuate with respect to the magnetic field. A magnetic field to which the magnetic resistance effect element is magnetically saturated is defined as a reset magnetic field, and a current that generates a reset magnetic field is defined as a reset current.

The switching unit 1130 switches whether or not to supply the feedback current for generating the feedback magnetic field to the magnetic field generation unit 530. Then, the reset current supply unit 1120 supplies the reset current to the magnetic field generation unit 530 to generate the reset magnetic field in the magnetic field generation unit 530 in a state where the feedback current is not supplied to the magnetic field generation unit 530. For example, the switching unit 1130 is provided between the amplifier circuit 532 and the coil 534, and connects the coil 534 to the reset current supply unit 1120 when the feedback current generated by the amplifier circuit 532 is not supplied to the coil 534. Then, the reset current supply unit 1120 may supply the reset current to the coil 534 to generate the reset magnetic field in the coil 534 in a state where the feedback current is not supplied to the coil 534.

As described above, in the present modification, when the input magnetic field to the sensor unit 300 is input to the magnetic sensor 520, the amplification circuit 532 receives the output voltage of each of the magnetic sensor 520 according to the input magnetic field. A feedback current corresponding to the difference (that is, voltage field) is generated and supplied to the coil 534. Then, the coil 534 generates a feedback magnetic field that cancels the input magnetic field input to the magnetic sensor 520 according to the supplied feedback current. Then, in the measurement phase, the output unit 540 outputs a measured value corresponding to the feedback current generated with respect to the input magnetic field, specifically, a voltage value corresponding to the voltage Vclosed. Here, this series of controls is defined as closed loop control. Under closed-loop control, the value of the voltage Vopen is controlled to be 0, that is, a feedback magnetic field that cancels the input magnetic field is generated.

In the above description, the case where the coil 534 is shared as a coil for generating a feedback magnetic field and a reset magnetic field is shown as an example, but the present invention is not limited to this. The sensor unit 300 may include a coil different from the coil 534 for generating the feedback magnetic field as the coil for generating the reset magnetic field. Further, in the above description, the case where the sensor unit 300 includes all of the magnetic reset units 1110 is shown as an example, but the present invention is not limited to this. A part of the magnetic reset unit 1110, for example, the reset current supply unit 1120 may not be provided in the sensor unit 300, or may be provided in the sensor data collection unit 230, for example.

FIG. 12 shows an example of the flow of magnetic reset in the reset phase by the sensor unit 300 according to this modified example. Here, the state in which closed loop control is not performed is defined as an open loop. In step 1210, the switching unit 1130 switches from the closed loop control to a state in which the feedback current is not supplied to the coil 534, that is, to an open loop. Further, the switching unit 1130 connects the coil 534 to the reset current supply unit 1120.

Next, in step 1220, the reset current supply unit 1120 supplies a reset current to the coil 534 to generate a reset magnetic field in the coil 534. Here, even if the reset current supply unit 1120 supplies a current of a sufficiently large size predetermined for magnetic saturation of each magnetoresistive sensor included in the magnetic sensor 520 to generate a reset magnetic field in the coil 534. Good. Instead, the reset current supply unit 1120 monitors the output voltage of the magnetic sensor 520 and supplies the reset current until the output voltage of the magnetic sensor 520 reaches a value indicating that each magnetic resistance effect element is magnetically saturated. The strength may be gradually increased to generate a reset magnetic field in the coil 534. The reset magnetic field is, for example, in a state where the magnetic field is 0 so that the magnetic resistance effect element can be magnetically saturated regardless of the orientation in which the sensor unit 300 is arranged, that is, regardless of the orientation in which the geomagnetism is applied. The magnitude of the magnetic field that magnetically saturates the magnetic resistance effect element may be greater than or equal to the magnitude obtained by adding the geomagnetic component.

Next, in step 1230, the reset current supply unit 1120 stops supplying the reset current to the coil 534. Here, the reset current supply unit 1120 generates a reset magnetic field in the coil 534 to magnetically saturate each magnetoresistive effect element, and then gradually reduces the magnitude of the reset current supplied to the coil 534 to reduce the magnitude of the reset current to the coil 534. The strength of the reset magnetic field generated in may be gradually reduced. In general, when a magnetic field is applied to a magnetoresistive sensor, the domain wall (the boundary between the magnetic domain and the magnetic domain) moves, and then the magnetization rotates in the magnetic domain, and eventually the whole magnetic domain becomes one. It becomes a single magnetic domain covered with. This corresponds to magnetic saturation. Then, when the magnetic field of the magnetoresistive sensor is reduced from the state of magnetic saturation, a domain wall having various magnetization directions is generated so as to minimize the energy of the magnetoresistive sensor, and the domain wall is generated as the magnetic field is reduced. I will move. According to the reset current supply unit 1120 of the sensor unit 300 according to this modification, in step 1230 after magnetically saturating each magnetoresistive sensor, the reset magnetic field supplied to the coil 534 is gradually reduced to cause magnetism. The resistance effect element can always be brought close to the same magnetization state. As a result, the magnetoresistive sensor is in the same state for each magnetic reset, so that the variation in the magnetization state of the magnetoresistive element after each magnetic reset can be relatively small.

Then, in step 1240, the switching unit 1130 connects the coil 534 to the amplifier circuit 532, switches from the open loop to the feedback control, and ends the magnetic reset process. After that, in the measurement phase, the output unit 540 outputs a measured value according to the feedback current generated with respect to the input magnetic field under closed loop control.

FIG. 13 shows a magnetization curve of a general magnetic material. In the initial magnetization state, the magnetic material has a magnetization of 0 when the magnetic field is 0, as shown at point 1310. When the magnetic field is increased to the positive side from this state, the magnetization increases following the curve 1350 and reaches the point 1312. This curve 1350 is called the initial magnetization curve. When the point 1312 is reached, the magnetization does not change even if the magnetic field is further increased to the positive side. At this time, the magnetic material is in a magnetically saturated state. After that, when the magnetic field is reduced, the magnetization is reduced by following the curve 1360 instead of the curve 1350, and reaches the point 1314. At point 1314, the magnetization remains even if the magnetic field is 0, and this is called residual magnetization. Further, as the magnetic field is increased to the negative side, the magnetization decreases following the curve 1360 and reaches the point 1316. When the point 1316 is reached, the magnetization does not change even if the magnetic field is further increased to the negative side. At this time, the magnetic material becomes magnetically saturated again. After that, when the magnetic field is increased to the positive side again, the magnetization increases by following the curve 1370 instead of the curve 1360, and reaches the point 1312 via the point 1318. The magnetic material generally has such a magnetic hysteresis characteristic. Here, the maximum loop including the curve 1360 and the curve 1370 passing through the points 1312 and 1316 in which the magnetic material is magnetically saturated is referred to as a major loop.

On the other hand, for example, when the magnetic field is increased to the negative side from the state of point 1318, the magnetization decreases following the curve 1380. From this state, when the magnetic field is increased to the positive side again at the point 1320 before the magnetic material is magnetically saturated, the magnetization increases by following the curve 1390 instead of the curve 1380, and reaches the point 1318. A loop composed of, for example, a curve 1380 and a curve 1390, which does not pass through the points 1312 and 1316 in which the magnetic material is magnetically saturated is referred to as a minor loop.

FIG. 14 shows the characteristics of the voltage Vopen with respect to the input magnetic field Bin to the magnetic sensor 520 in the sensor unit 300 according to this modification. In this modification, the characteristics of the voltage Vopen with respect to the input magnetic field Bin to the magnetic sensor 520 are the first magnetoresistive sensor 710a, the second magnetoresistive element 710b, the third magnetoresistive element 710c, and the magnetic sensor 520. It has the characteristics shown in this figure according to the magnetic hysteresis characteristics of the No. 4 magnetoresistive element 710d. Reference numeral 1410 indicates a minor loop, and reference numeral 1420 indicates a major loop.

When the magnetic field is measured under closed loop control in the state before the magnetic reset is performed, the magnetic operating point of each magnetoresistive element of the magnetic sensor 520 is on the minor loop 1410. The magnetic field will be measured at the point 1430. However, as a general phenomenon of a magnetic material, each magnetoresistive sensor possessed by the magnetic sensor 520 has a higher magnetic sensitivity (Bin) when operated on a minor loop than when operated on a major loop. The rate of change of the voltage Vopen with respect to the voltage) cannot be obtained, and the weak magnetic field to be measured cannot be detected. Therefore, in the measuring device 10 each of the plurality of magnetic sensor cells 220 having the sensor unit 300 according to the present modification, the magnetic sensor 520 detected as a defective sensor due to a large noise is magnetically reset before detecting the magnetic field to be measured.

FIG. 15 shows the configurations of the magnetic sensor array 210, the sensor data collection unit 230, and the sensor data processing unit 900 when each of the plurality of magnetic sensor cells 220 has the sensor unit 300 according to the present modification. In this figure, members having the same functions and configurations as those in FIG. 9 are designated by the same reference numerals, and the description thereof will be omitted except for the following differences. In this modification, the plurality of magnetic sensor cells 220 included in the magnetic sensor array 210 include, for example, the sensor unit 300 shown in FIG. That is, each of the sensor units 300 included in the plurality of magnetic sensor cells 220 is configured to be able to magnetically reset the magnetic sensor 520 in the reset phase. Further, in this modification, the sensor data processing unit 900 further includes a determination unit 1510 and a basis vector update unit 1520.

The determination unit 1510 determines whether to reset at least one of the plurality of magnetic sensor cells 220 based on the detection error ε of the magnetic field supplied from the error calculation unit 950. More specifically, the determination unit 1510 determines to reset the magnetic sensor cell 220 including the magnetic sensor 520 used to acquire the measured value where the magnetic field detection error ε exceeds a predetermined range. In this case, the determination unit 1510 may decide to reset only the magnetic sensor 520 used for acquiring the measured value whose detection error ε exceeds a predetermined range, or the magnetic sensor cell including the magnetic sensor 520. It may be decided to reset all the magnetic sensors 520 of 220.

The basis vector update unit 1520 updates the basis vector based on the detection error ε. Then, the magnetic field calculation unit 930 recalculates the input magnetic field after the magnetic sensor 520 used for acquiring the measured value whose detection error ε exceeds a predetermined range is magnetically reset. At this time, the magnetic field calculation unit 930 uses the basis vector updated by the basis vector update unit 1520. This will be described in detail.

FIG. 16 shows an example of a flow in which the measuring device 10 having the sensor unit 300 according to the present modification of each of the plurality of magnetic sensor cells 220 resets the defective sensor as a preprocessing for calculating the measurement target magnetic field. In step 1610, the measuring device 10 acquires measurement data. For example, the measurement data acquisition unit 910 acquires a plurality of measurement values (measurement data Φ _All ) based on the input magnetic field measured by the sensor units 300x to z in the plurality of magnetic sensor cells 220 constituting the magnetic sensor array 210.

In step 1620, the measuring device 10 calculates the input magnetic field. In this flow, the measurement data selection unit 920 selects all of the plurality of measured values as the measurement data Φ _Select . (Φ _Select = Φ _All ). Then, the magnetic field calculation unit 930 calculates the input magnetic field based on the measurement data Φ _All by the same method as in step 1020.

In step 1630, the measuring device 10 calculates the detection error ε. For example, the error calculation unit 950 calculates the detection error ε by the same method as in step 1030.

Then, in step 1640, the measuring device 10 updates the basis vector. For example, the basis vector update unit 1520 updates the basis vector using the least squares method so as to minimize the detection error ε calculated in step 1630. Specifically, for example, the basis vector is obtained by updating the calibration coefficient matrix K in (Equation 7) by executing an algorithm that minimizes ε defined by (Equation 13) based on the optimization theory. Update. The calibration coefficient matrix K includes vectors representing the magnetic sensitivity axis direction and the magnetic sensitivity in the sensor units 300x, y, and z of the plurality of magnetic sensor cells 220. Therefore, the basis vector updating unit 1520 can correct the magnetic sensitivity (spindle sensitivity and other axis sensitivity) of each magnetic sensor cell 220 by updating the calibration coefficient matrix K.

In step 1650, the measuring device 10 calculates the input magnetic field using the updated basis vector updated in step 1640. For example, the magnetic field calculation unit 930 calculates the input magnetic field by the same method as in step 1020 using the updated basis vector.

In step 1660, the measuring device 10 calculates the detection error ε. For example, the error calculation unit 950 calculates the detection error ε by the same method as in step 1030.

In step 1670, the measuring device 10 selects the maximum error sensor in which the absolute value of the detection error ε is the maximum (maximum error). For example, the determination unit 1510 identifies the measurement value that maximizes the absolute value of the detection error ε based on the detection error ε for each measurement value supplied from the error calculation unit 950, and is used to acquire the measurement value. The magnetic sensor 520 is selected as the maximum error sensor.

In step 1680, the measuring device determines whether the maximum error is less than or equal to a predetermined threshold. For example, the determination unit 1510 may determine whether or not the absolute value of the detection error ε in the maximum error sensor selected in step 1670 is equal to or less than a predetermined threshold value Max_E_Th.

If it is determined in step 1680 that the maximum error is equal to or less than a predetermined threshold value, the measuring device 10 ends the process of the flow for resetting the defective sensor.

On the other hand, if it is determined in step 1680 that the maximum error exceeds a predetermined threshold value, in step 1690, the determination unit 1510 determines to reset the magnetic sensor 520 selected as the maximum error sensor in step 1670. In this case, the determination unit 1510 may decide to reset only the magnetic sensor 520 used for acquiring the measured value whose detection error ε exceeds a predetermined range, or the magnetic sensor cell including the magnetic sensor 520. It may be decided to reset all the magnetic sensors 520 of 220. Then, the determination unit 1510 instructs the magnetic sensor cell 220 including the magnetic sensor 520 determined to be reset to reset. The magnetic sensor cell 220 instructed to reset switches the magnetic sensor 520 to be reset from closed loop control to open loop according to the flow of FIG. 12, transitions to the reset phase, and magnetically resets.

In step 1690, after the magnetic sensor 520 used for acquiring the measured value in which the detection error ε exceeds a predetermined range is magnetically reset, the process is returned to step 1610, and the magnetic field calculation unit 930 newly acquires. The input magnetic field is recalculated using the measured measurement data. The measuring device 10 repeats the process until it is determined in step 1680 that the maximum error is equal to or less than a predetermined threshold value. At this time, the measuring device 10 repeats the process (under closed loop control) without cutting the feedback current for the magnetic sensor other than the magnetic sensor that executes the magnetic reset.

In this way, the determination unit 1510 determines whether to reset at least one of the plurality of magnetic sensor cells 220 based on the detection error ε of the magnetic field supplied from the error calculation unit 950. More specifically, the determination unit 1510 determines to reset the magnetic sensor cell 220 including the magnetic sensor 520 used to acquire the measured value where the magnetic field detection error ε exceeds a predetermined range.

In the above description, when the measuring device 10 first selects one maximum error sensor having the relatively largest detection error ε and determines that the maximum error exceeds a predetermined threshold value, the maximum is the maximum. The case where the error sensor is magnetically reset has been described as an example. However, it is not limited to this. The measuring device 10 may magnetically reset one or more magnetic sensors 520 in which the absolute value of the detection error ε exceeds a predetermined threshold value.

If the absolute value of the detection error ε does not fall below the predetermined threshold value even after magnetic resetting more than a predetermined number of times, the magnetic sensor 520 used to acquire the measured value is used for the magnetic field to be measured. The process may be terminated by deciding not to use it for detection.

In this way, the measuring device 10 magnetically resets the magnetic sensor 520 used for acquiring the measured value having a large absolute value of the detection error ε, and re-detects the input magnetic field. The magnetic sensor 520 used to acquire the measured value having a large absolute value of the detection error ε may be a defective sensor in which the magnetic sensitivity is lowered or the noise is increased due to the magnetic history. According to the measuring device 10 of this modified example, the defective sensor whose magnetic sensitivity is lowered or whose noise is increased is magnetically reset before the detection of the magnetic field to be measured to increase the magnetic sensitivity, so that the magnetic field to be measured is calculated. The accuracy can be improved.

The above-described embodiment and another embodiment may function independently, or both embodiments may be combined to function. That is, for example, as a pretreatment before the detection of the magnetic field to be measured, a flow for resetting the defective sensor according to FIG. 16 may be executed, and then a flow for excluding the defective sensor according to FIG. 10 may be executed. By combining both embodiments, the detection accuracy of the magnetic field to be measured can be further improved.

Further, in the above-described embodiment, a case where the measuring device 10 calculates the input magnetic field while excluding the measured value i having a large absolute value of the detection error ε is shown as an example. However, it is not limited to this.

For example, the magnetic field calculation unit 930 solves the spatial distribution of the magnetic field by (Equation 11), and based on the plurality of measurement values selected by the measurement data selection unit 920, the location where the plurality of measurement values are measured. The input magnetic field can be recalculated. In that case, the error calculation unit 950 may calculate the detection error based on the detection result of the input magnetic field at the place where the recalculated plurality of measured values are measured.

As an example, the magnetic field calculation unit 930 uses the coefficients related to the calculation result of the input magnetic field, that is, ^ Xin and ^ Xout in (Equation 11) by solving the spatial distribution of the magnetic field by (Equation 11), and uses the signal space. The magnetic field vector B (r) at the coordinates of the sensor that measured the measured value i excluded from the separation calculation (position vector = r, coordinates displayed in polar coordinates = (r, θ, φ)) can be expressed by the following equation. it can.

That is, the magnetic field calculation unit 930 inputs the excluded measured value i at the measured location based on the coefficient related to the calculation result of the input magnetic field calculated from the plurality of measured values selected by the measurement data selection unit 920. The magnetic field can be calculated. As a result, since the measuring device 10 reconstructs the magnetic field in the defective sensor by (Equation 15), it is possible to suppress a decrease in magnetic field measurement accuracy due to the lack of the measured value at the position of the defective sensor. Therefore, the measuring device 10 can perform highly accurate magnetic field detection.

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 a computer-readable medium, and / or processors supplied with computer-readable instructions stored on a computer-readable medium. 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.

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 disk 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 or to a processor or programmable circuit of a general purpose computer, special purpose computer, or other programmable data processing device, or to a wide area network (WAN) such as the 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. 17 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 or one or more sections of the device according to an embodiment of the invention, 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 of 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. Computer 2200 also includes input / output units such as communication interface 2222, hard disk drive 2224, DVD-ROM drive 2226, and IC card drive, which are connected to host controller 2210 via input / output controller 2220. There is. The computer also includes legacy input / output units such as 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-ROM 2201 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 the transmission data stored in the transmission buffer processing area provided in the recording medium such as the RAM 2214, the hard disk drive 2224, the DVD-ROM 2201, or the 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 recording media 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, and is specified by the instruction sequence of the program. 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 a computer 2200 or on a computer readable medium near the computer 2200. Also, a recording medium such as a hard disk or RAM provided within 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. To 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 the form with such modifications or improvements may be included in the technical scope of the present invention.

The order of execution of each process such as operation, procedure, step, and step in the device, system, program, and method 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 Measuring device 100 Main body 110 Magnetic sensor unit 120 Head 130 Base 140 Pole 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 Coil 540 Output 542 Current-voltage conversion resistance 544 Magneto-resistive sensor 720, 730 Magneto-convergent plate 900 Sensor data processing unit 910 Measurement data acquisition unit 920 Measurement data selection unit 930 Magnetic field calculation unit 940 Vector storage unit 950 Error calculation unit 1110 Magnetic reset unit 1120 Reset current supply unit 1130 Switching unit 1510 Determination unit 1520 Base vector update unit 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 (18)

A magnetic sensor array, each of which is configured by arranging a plurality of magnetic sensor cells including a magnetic sensor in three dimensions and capable of detecting an input magnetic field in three axial directions.
A measurement data acquisition unit that acquires a plurality of measurement values based on the input magnetic field detected by the magnetic sensor array, and a measurement data acquisition unit.
A magnetic field calculation unit that calculates the input magnetic field based on the plurality of measured values,
An error calculation unit that calculates the detection error of the magnetic field based on the plurality of measured values and the calculation result of calculating the input magnetic field.
A measurement data selection unit that selects a plurality of measurement values to be used for calculating the input magnetic field by the magnetic field calculation unit from the plurality of measurement values based on the detection error.
A measuring device. The error calculation unit calculates the detection error for each of the plurality of measured values.
The measuring device according to claim 1, wherein the measurement data selection unit selects the plurality of measured values by excluding the measured values whose detection error exceeds a predetermined range. The measuring device according to claim 2, wherein the magnetic field calculation unit recalculates the input magnetic field after excluding a measured value in which the detection error exceeds a predetermined range. The magnetic field calculation unit recalculates the input magnetic field at the location where the plurality of measured values are measured, based on the plurality of measured values selected by the measurement data selection unit.
The measuring device according to claim 3, wherein the error calculating unit calculates the detection error based on the detection result of the input magnetic field at the place where the plurality of measured values are measured. The magnetic field calculation unit is the location where the excluded measurement value is measured based on the coefficient related to the calculation result of the input magnetic field calculated from the plurality of measurement values selected by the measurement data selection unit. The measuring device according to claim 3 or 4, which calculates an input magnetic field. Each of the plurality of magnetic sensor cells responds to a magnetic field generator that applies a feedback magnetic field that reduces the input magnetic field detected by the magnetic sensor to the magnetic sensor, and a current that the magnetic field generator flows to generate the feedback magnetic field. The measuring device according to any one of claims 1 to 5, further comprising an output unit for outputting the output signal. A magnetic sensor array that is configured by arranging a plurality of magnetic sensor cells in three dimensions and can detect an input magnetic field in three axial directions.
A measurement data acquisition unit that acquires a plurality of measurement values based on the input magnetic field detected by the magnetic sensor array, and a measurement data acquisition unit.
A magnetic field calculation unit that calculates the input magnetic field based on the plurality of measured values,
An error calculation unit that calculates the detection error of the magnetic field based on the plurality of measured values and the calculation result of calculating the input magnetic field.
A determination unit that determines whether to reset at least one of the plurality of magnetic sensor cells based on the detection error.
With
Each of the plurality of magnetic sensor cells
With a magnetic sensor
A magnetic field generator that applies a feedback magnetic field that reduces the input magnetic field detected by the magnetic sensor to the magnetic sensor,
An output unit that outputs an output signal according to the current that the magnetic field generation unit flows to generate the feedback magnetic field, and an output unit.
When resetting the magnetic sensor cell, a magnetic reset unit that applies a reset magnetic field that magnetically saturates the magnetic sensor to the magnetic sensor, and
Including measuring equipment. The error calculation unit calculates the detection error for each of the plurality of measured values.
The measuring device according to claim 7, wherein the determination unit determines to reset the magnetic sensor cell including the magnetic sensor used for acquiring the measured value whose detection error exceeds a predetermined range. The magnetic field calculation unit according to claim 8, wherein the magnetic field calculation unit recalculates the input magnetic field after the magnetic sensor used for acquiring the measured value whose detection error exceeds a predetermined range is magnetically reset. measuring device. The magnetic reset unit includes a switching unit for switching whether or not to supply a feedback current for generating the feedback magnetic field to the magnetic field generation unit, and the magnetic field is in a state where the feedback current is not supplied to the magnetic field generation unit. The measuring device according to any one of claims 7 to 9, wherein a reset current is supplied to the generation unit to generate the reset magnetic field in the magnetic field generation unit. The measuring device according to any one of claims 1 to 10, wherein the magnetic field calculation unit calculates the input magnetic field so that the square of the detection error is minimized. The magnetic field calculation unit outputs a signal output by each of the magnetic sensors when the magnetic sensor array detects a magnetic field having a spatial distribution of a normal orthogonal function with respect to the spatial distribution of the input magnetic field indicated by the plurality of measured values. Signals are separated using the signal vector whose component is
The measuring device according to any one of claims 1 to 11, wherein the error calculation unit calculates the detection error based on the result of signal separation by the magnetic field calculation unit. The measuring device according to claim 12, further comprising a basis vector updating unit that updates the basis vector based on the detection error. The measuring device according to any one of claims 6 to 10, wherein the magnetic sensor has a magnetoresistive element. Each of the magnetic sensors further has 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 measuring device according to claim 14. The measuring device according to claim 15, wherein a coil for generating the feedback magnetic field is wound so as to surround the magnetoresistive sensor and the two magnetic focusing plates. A plurality of AD converters that convert the outputs of the plurality of magnetic sensor cells from analog to digital and output the plurality of measured values are further provided.
The measuring device according to any one of claims 1 to 16, wherein the plurality of AD converters perform AD conversion according to a common sampling clock. The magnetocardiography generated by the electrical activity of the animal's heart is measured.
The measuring device according to any one of claims 1 to 17, which measures the magnetocardiography based on the calculation result of the magnetic field calculation unit.

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