Magnetic field measuring apparatus, magnetic field measuring method, and recording medium storing magnetic field measuring program
A magnetic field measuring apparatus is provided including: a magnetic sensor array configured so that a plurality of magnetic sensor cells including a plurality of magnetic sensors each having a magnetoresistive element and magnetic flux concentrators arranged on both ends of the magnetoresistive element are three-dimensionally arranged and capable of detecting a magnetic field in three axial directions; a magnetic field acquiring section configured to acquire measurement data measured by the magnetic sensor array; and a signal space separating section configured to perform signal separation on a spatial distribution of a magnetic field indicated by the measurement data, based on basis vectors calculated from orthonormal functions and a position and magnetic sensitivity of each magnetic sensor of the magnetic sensor array.
1. A magnetic field measuring apparatus comprising:
a magnetic sensor array configured with a plurality of magnetic sensor cells being three-dimensionally arranged, wherein each of the plurality of magnetic sensor cells is capable of detecting a magnetic field in three axial directions, and each of the plurality of magnetic sensor cells includes a plurality of magnetic sensors each having a magnetoresistive element;
at least one processor;
a magnetic field acquiring section configured to acquire measurement data measured by the magnetic sensor array; and
a signal space separating section configured to perform, using the at least one processor, signal separation on a spatial distribution of the magnetic field indicated by the measurement data, based on basis vectors calculated from orthonormal functions and a position and magnetic sensitivity of each magnetic sensor of the magnetic sensor array, wherein
each of the magnetic sensor cells comprises:
a magnetic field generating section configured to generate a feedback magnetic field to reduce an input magnetic field detected by each of the magnetic sensors; and
an output section configured to output an output signal corresponding to a feedback current that is to flow in order for the magnetic field generating section to generate the feedback magnetic field.
2. The magnetic field measuring apparatus according to claim 1 , wherein the signal space separating section performs, using the at least one processor, the signal separation to separate the spatial distribution of the magnetic field into a to-be-measured magnetic field and a disturbance magnetic field.
3. The magnetic field measuring apparatus according to claim 2 , wherein the signal space separating section suppresses, using the at least one processor, the disturbance magnetic field to calculate the to-be-measured magnetic field.
4. The magnetic field measuring apparatus according to claim 1 , wherein the signal space separating section performs, using the at least one processor, the signal separation on the spatial distribution of the magnetic field, through series expansion of the basis vectors.
5. The magnetic field measuring apparatus according to claim 2 , wherein the signal space separating section performs, using the at least one processor, the signal separation on the spatial distribution of the magnetic field, through series expansion of the basis vectors.
6. The magnetic field measuring apparatus according to claim 3 , wherein the signal space separating section performs, using the at least one processor, the signal separation on the spatial distribution of the magnetic field, through series expansion of the basis vectors.
7. The magnetic field measuring apparatus according to claim 4 , wherein the signal space separating section calculates, using the at least one processor, expansion coefficients of the basis vectors using a least-squares method.
8. The magnetic field measuring apparatus according to claim 1 , wherein the orthonormal functions are expressed with spherical harmonics.
9. The magnetic field measuring apparatus according to claim 2 , wherein the orthonormal functions are expressed with spherical harmonics.
10. The magnetic field measuring apparatus according to claim 1 , wherein the magnetic sensors each further include magnetic flux concentrators arranged on both one end and the other end of the magnetoresistive element.
11. The magnetic field measuring apparatus according to claim 2 , wherein the magnetic sensors each further include magnetic flux concentrators arranged on both one end and the other end of the magnetoresistive element.
12. The magnetic field measuring apparatus according to claim 1 , further comprising a calibration calculating section configured to calibrate, using the at least one processor, the measurement data acquired by the magnetic field acquiring section.
13. The magnetic field measuring apparatus according to claim 2 , further comprising a calibration calculating section configured to calibrate, using the at least one processor, the measurement data acquired by the magnetic field acquiring section.
14. The magnetic field measuring apparatus according to claim 1 , wherein the magnetic sensor array is formed in two stages.
15. The magnetic field measuring apparatus according to claim 2 , wherein the magnetic sensor array is formed in two stages.
16. The magnetic field measuring apparatus according to claim 1 , wherein in the magnetic sensor array, the magnetic sensor cells are three-dimensionally arranged to be positioned at grid points between two curved surfaces curved in one direction.
17. The magnetic field measuring apparatus according to claim 2 , wherein in the magnetic sensor array, the magnetic sensor cells are three-dimensionally arranged to be positioned at grid points between two curved surfaces curved in one direction.
18. The magnetic field measuring apparatus according to claim 16 , wherein the curved surfaces are formed to be substantially parabolic.