JP2007170976A - Detection system of position, direction, and equivalent magnetic moment of high accuracy lc resonance type magnetic marker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detection system of the position, the direction, and the equivalent magnetic moment of a high accuracy LC resonance type magnetic marker for improving position accuracy by using not only an amplitude but also a phase as a measuring object. <P>SOLUTION: This system is equipped with an excitation coil, a plurality of detection coils facing to the excitation coil, an LC resonance type magnetic marker arranged between the excitation coil and the detection coils, a means for measuring an induction field from the LC resonance type magnetic marker by each detection coil of the plurality of detection coils when the excitation coil generates an alternating-current magnetic field synchronized with a resonance frequency of the LC resonance type magnetic marker, a means for measuring the first induced voltage by the detection coil in the state where the LC resonance type magnetic marker is set, a means for measuring the second induced voltage by the detection coil in the state where the LC resonance type magnetic marker is not set, a means for determining a phase difference θ between the first induced voltage and the second induced voltage, and a means for determining a contribution voltage of the LC resonance type magnetic marker based on the phase difference. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a position detection system for an LC resonance type magnetic marker, and in particular, detects the position, direction and equivalent magnetic moment (proportional to the amount of magnetic flux interlinked with a marker coil) of a plurality of LC resonance type magnetic markers by phase measurement. It is about the system.

  In the case where the position of a part inside the living body or the surface of the living body is accurately measured by a magnetic method, it is desirable that the marker attached to the measurement part does not have an electrical lead wire or a battery. So far, as a method suitable for detecting the position of an optically shielded space, a method for detecting the position of a permanent magnet or a magnetized magnetic material has been developed (the following Non-Patent Documents 1-5). However, since these measure a DC magnetic field, they are susceptible to the effects of geomagnetism and low-frequency noise.

  On the other hand, Massachusetts Institute of Technology reports a marker position detection system using an LC resonance circuit (Non-Patent Document 6 below). However, this is to roughly measure the position of the magnetic marker using one coil, and the position accuracy has not been discussed, and it is not a precise position detection system on the order of mm. Moreover, it is difficult to measure the five degrees of freedom of the marker position and direction. Also, a position detection method using an active IC tag with a built-in battery has been proposed (Non-Patent Document 7 below), but there are problems such as restrictions on dimensions and operating time and time stability of measurement due to the built-in battery. is there.

  The inventors of the present application aimed to achieve both the necessity of an electrical lead wire to the magnetic marker and the difficulty of being affected by external noise, and a position detection system using a marker by an LC resonance circuit. Proposed. By measuring the amplitude of the induced voltage of the marker, it was shown that the position of the marker can be detected with a positional accuracy of about 2 mm using a magnetic marker having a diameter of 5 mm and a length of 10 mm (Non-patent Document 8 below). .

In the position detection system, if the marker diameter is reduced to about 1 mm and can be measured with a position accuracy of about 1 mm, the marker can be inserted into the living body with an injection needle or a catheter and the position can be measured with high accuracy. Possibility is considered to be a current issue.
JP 2005-121573 A F. Grant, G.G. West, Interpretation Theory in Applied Geophysics. New York: McGraw-Hill, 1965, pp. 306-381. S. V. Marshall, Vehicle Detection Using a Magnetic Field Sensor, IEEE Trans. Vehicular Technology, vol. VT-27, pp. 65-68, (1978). W. M.M. Wynu, C.I. P. Frahm, P.A. J. et al. Carroll, R.A. H. Clark, J. et al. Wellhoner, M .; J. et al. Wynn, Advanced Supercomputing Gradiometer / Magnetometer Arrays and A Novel Signal Processing Technique, IEEE Trans. Magn. vol. MAG-11, pp. 701-707, (1974). J. et al. E. McFee, Y.M. Das, Determination of the Parameters of a Dipole by Measurement of it's Magnetic Field, IEEE Trans. Antennas and Propagation, vol. AP-29, pp. 282-287, (1981). S. Yabukami, K .; Arai, H .; Kanetaka, S .; Tsuji, and K.K. I. Arai, Journal of the Magnetics Society of Japan, vol. 28, pp. 711-717, (2004). J. et al. A. Paradiso, K .; Hsiao, J. et al. Stricken, J .; Lifton, A.M. Adler, IBM Systems Journal, vol. 39, no. 3 & 4, pp. 892-914, (2000). S. Watanabe, S.M. Nishiyama, N .; Koshizuka, and K.K. Sakamura, MWE 2003 Microwave Workshop, pp. 245-250, (2003). S. Yabukami, S .; Hashi, Y .; Tokunaga, T .; Kohno, K .; I. Arai, and Y.A. Okazaki, Journal of the Magnetics Society of Japan, vol. 28, pp. 877-885, (2004). T.A. Nakagawa, Y .; Koyanagi, Experimental Data Analysis by the least square method, p. 95-99, The University of Tokyo Press (1982).

  Therefore, the present invention aims to improve the detection accuracy of the marker position by measuring not only the amplitude of the induced voltage of the magnetic marker but also the phase. In other words, in Patent Document 1 and Non-Patent Document 8, it may not be sufficient to obtain the marker contribution voltage only from the amplitude depending on the electrical characteristics of the marker and the arrangement of the marker and each coil. Furthermore, when only the amplitude is to be measured, it is necessary to measure signals of two frequencies per marker, and there is a problem that the measuring apparatus becomes complicated when detecting the positions of a large number of markers. It was.

  Furthermore, the present invention intends to connect each detection coil to the same number of high-speed AD converters in parallel to increase the speed and the S / N ratio. Thus, the objective was to measure the position and direction of the marker having a diameter of about 1 mm and the equivalent magnetic moment, which are realistic dimensions for inserting or sticking the marker into the living body or on the surface of the living body.

  A position detection system based on the above target was developed, and a fine marker having a diameter of 1.2 mm and a length of 10 mm was used as a marker coil with a three-dimensional movement of about 100 mm with an absolute position accuracy of about 1 mm. It was shown that measurement is possible. The marker position can be displayed in real time.

  That is, in view of the above situation, the present invention provides the position, direction, and direction of a high-accuracy LC resonance type magnetic marker that can improve the detection accuracy of the marker position as a measurement target in addition to the amplitude of the induced voltage of the magnetic marker. An object is to provide an equivalent magnetic moment detection system.

In order to achieve the above object, the present invention provides
[1] In a system for detecting the position, direction, and equivalent magnetic moment of a high-accuracy LC resonance type magnetic marker, an excitation coil, a plurality of detection coils opposed to the excitation coil, and between the excitation coil and the detection coil And the exciting coil generates an alternating magnetic field tuned to a resonance frequency of the LC resonant magnetic marker, and an induced magnetic field from the LC resonant magnetic marker is detected by the plurality of detection coils. Means for measuring with each detection coil, means for measuring a first induced voltage by the detection coil in a state in which the LC resonance type magnetic marker is set, and the state in which the LC resonance type magnetic marker is not set. Means for measuring a second induced voltage by the detection coil; means for determining a phase difference between the first induced voltage and the second induced voltage; and the phase difference. Based characterized by comprising a means for obtaining a voltage of the LC resonant magnetic marker.

  [2] In the detection system for the position, direction, and equivalent magnetic moment of the high-accuracy LC resonant magnetic marker described in [1] above, the measurement means may convert the detection coils to the same number of high-speed AD converters as the detection coils. It is characterized by being connected in parallel to increase the speed and the SN ratio.

  According to the present invention, the following effects can be achieved.

The position of a plurality of markers can be detected by phase measurement. That is, this system is composed of an excitation coil, a detection coil, and an LC resonance type marker, excites an AC magnetic field tuned to the resonance frequency of the LC resonance type marker, measures the induction magnetic field from the marker with each detection coil, Optimize the marker position, orientation, and equivalent magnetic moment (proportional to the amount of magnetic flux linking the marker coil). In this case, as described in the vector diagram of FIG. 4, the phase change Δθ due to the induced voltage of the marker is used when obtaining the voltage V _mk (vector amount) due to the induced magnetic field from the marker.

  The detection system of the position, direction and equivalent magnetic moment (proportional to the amount of magnetic flux interlinking the marker coil) of the high-accuracy LC resonance type magnetic marker of the present invention includes an excitation coil and a plurality of detection coils opposed to the excitation coil. And an LC resonance type magnetic marker disposed between the excitation coil and the detection coil, and the excitation coil generates an alternating magnetic field tuned to a resonance frequency of the LC resonance type magnetic marker, and the LC resonance type Means for measuring the induced magnetic field from the magnetic marker with each of the detection coils, means for measuring a first induced voltage by the detection coil in a state where the LC resonance type magnetic marker is set, and Means for measuring a second induced voltage by the detection coil in a state where the LC resonance type magnetic marker is not set, the first induced voltage and the second induced voltage Comprising means for determining the phase difference, and means for determining the voltage of the LC resonant magnetic marker based on the phase difference.

  Hereinafter, embodiments of the present invention will be described in detail.

(1) Position, direction and equivalent magnetic moment detection method using phase information (1-1) Overall measurement procedure FIG. 1 shows a position and direction detection system using a high-accuracy LC resonance type magnetic marker according to the present invention. FIG. 2 is a flowchart for obtaining the position and direction of the high-accuracy LC resonance type magnetic marker according to the present invention.

  The position and direction detection system using the high-accuracy LC resonance type magnetic marker of the present invention comprises an excitation coil 1, a plurality of detection coils 2, and an LC resonance type magnetic marker 3, as shown in FIG. In this system, an alternating magnetic field tuned to the resonance frequency of the LC resonance type magnetic marker 3 is generated by the excitation coil 1 to excite the LC resonance type magnetic marker 3, and the induced magnetic field from the LC resonance type magnetic marker 3 is applied to each of the induction magnetic fields. Assuming that the induction magnetic field from the LC resonance type magnetic marker 3 is a dipole magnetic field measured by the detection coil 2, the position, direction and equivalent magnetic moment of the LC resonance type magnetic marker 3 (the amount of magnetic flux interlinking the marker coil) (Proportional) is optimized.

  A method for obtaining the position and direction of the high-accuracy LC resonance type magnetic marker according to the present invention will be described with reference to FIG.

  First, the excitation coil 1 and the detection coil 2 are set (step S1).

Next, with the LC resonance type magnetic marker 3 removed, the induced voltage of the arranged detection coil 2 is measured to _{obtain a} background voltage (B _background ) (step S2).

Next, the LC resonance type magnetic marker 3 is arranged, and the induced voltage (B _total ) of the detection coil 2 is measured (step S3).

Next, by determining the vector difference of the induced voltage due to the presence or absence of the LC resonance type magnetic marker 3, the contribution of the LC resonance type magnetic marker 3 (the induced voltage B ⁽ⁱ from the LC resonance type magnetic marker in the detection coil i ^{) )} m) is measured (step S4).

  Next, assuming that the induced magnetic field generated from the LC resonance type magnetic marker 3 can approximate the dipole magnetic field, the position and direction of the LC resonance type magnetic marker 3 are determined by the following equations (1) to (3). Optimization processing is performed by the Gauss-Newton method (see Non-Patent Document 9).

(1-2) Measurement Method Using Phase Information FIG. 3 is an explanatory diagram of the measurement of the induced voltage using the amplitude, which has already been proposed by the present inventors, and FIG. 4 is the measurement of the induced voltage using the phase of the present invention. It is explanatory drawing of.

FIG. 3A is a vector diagram showing the relationship between the contribution voltage of the magnetic marker and the induced voltage of the coil when measuring the amplitude of the induced voltage shown in Patent Document 1 or Non-Patent Document 8. .

  Here, the contribution voltage of the marker was obtained as in the following formula (4).

FIG. 3B shows the frequency dependence of the voltage amplitude in the state where the marker is inserted, and it is necessary to measure two frequency components of the maximum value and the minimum value of this voltage.

FIG. 4B schematically shows an equivalent circuit of the marker. In FIG. 4B, L is an inductance, C is a capacitance of a capacitor, R is an internal resistance, V is an induced voltage generated by an AC magnetic field given from the outside as an equivalent voltage source, and I is a voltage source. The induced current flowing in the circuit is shown.

  By measuring at the resonance frequency, measurement with the highest S / N ratio is possible, and the contribution voltage of the marker can be measured at one frequency per marker. In the present invention, the amplitude in the state where there is no marker in each detection coil and the phase difference between the two voltages are measured, and a vector-equivalent marker contribution voltage is obtained using the following equation (5).

3. Position Detection System Next, the position detection system will be described.

  FIG. 5 is a diagram showing the configuration of a prototype position detection system according to the present invention.

  The measurement system includes an excitation coil 11, a detection coil array 12 (20 channels), an LC resonance type magnetic marker 13, an AD converter and a DA converter 14 (NI PXI-6251: 1 unit), and an AD converter 15 (NI PXI-6250: 9 units). ), A control unit (NI PXI-8187), and a preamplifier 16 (SR560). The control program is Lab VIEW ver. 7.1, A position and orientation optimization processing program was created using Visual C ++. The AD converters PXI-6251 and PXI-6250 are used in a mode to measure 16-bit signals of 2 channels per unit at a sampling rate of 500 ksample / sec, and the induced voltages of 20 channels of detection coils are acquired in parallel. Configured to be possible. For the voltage to the excitation coil, the output signal from the AD converter and DA converter PXI-6251 was connected to the excitation coil via an amplifier. All AD converters and DA converters are synchronized with each other because of the PXI system, and the phase difference with respect to the reference signal can be measured. The LC resonance type magnetic marker was arranged inside a unit composed of an excitation coil and a detection coil. The marker position and direction optimization processing was performed by another personal computer [Pentium (registered trademark) (R) D, 3.20 GHz] connected via Ethernet, and the marker position was displayed on the screen.

  FIG. 6 is a photograph of the PXI controller (with built-in AD converter and DA converter), preamplifier, and display used in the measurement system according to the present invention. FIG. 7 is a photograph of an excitation coil, a detection coil, and a marker according to the present invention. FIG. 7A shows the excitation coil and marker arrangement. The excitation coil and the detection coil were arranged in a cube made of acrylic and having a side of 150 mm, and the surfaces of the excitation coil and the detection coil were opposed to each other at a distance of 150 mm. The exciting coil was a square having a side of about 150 mm, and 20 turns of a copper wire having a diameter of 1.0 mm was applied. FIG. 7 (b) shows a photograph of the detection coil array, and FIG. 7 (c) shows the arrangement of the detection coils. As the detection coil, a copper wire having a wire diameter of 0.2 mm was applied to a coil having a diameter of 23 mm and 125 turns, and 20 coils were arranged on the same plane. The diameter of the detection coil is 23 mm, and the numerical value in the round frame indicates the number of the detection coil. The arrangement position of the detection coil was designed with the intention of sufficiently reducing the influence of the local solution inside a cube having a side of 150 mm.

  FIG. 8 shows a photograph of a prototype LC resonance type marker according to the present invention. The marker was produced by connecting a coil and a capacitor in series with solder. Two types of markers are prepared, and the dimensions are shown in Table 1.

The marker 1 was formed by winding a copper wire having a diameter of 0.1 mm for 500 turns around a MnZn ferrite having a diameter of 5 mm and a length of 20 mm (EE series manufactured by TDK Corporation) to have an outer dimension of 20 mm in length and a diameter of about 6 mm. The inductance at 90 kHz was about 5.6 mH. The figure of merit at 90 kHz was about 60. As the capacitor, a 1 nF chip capacitor (ROCH MCH series) was used.

  The marker 2 is obtained by applying one layer (77 turns) of a 0.1 mm diameter copper wire around a MnZn ferrite having a diameter of 1 mm and a length of 10 mm. The resonance frequency of each marker was set to about 90 kHz. The figure of merit at the resonant frequency was about 10. The marker was moved by a non-conductor triaxial scanner.

(4) Measurement Result (4-1) Amplitude and Phase Measurement Accuracy FIG. 9 shows the amplitude and phase measurement accuracy in the measurement system according to the present invention with respect to the measurement time. Each was obtained from the standard deviation in 1000 measurements. The longer the measurement time, the higher the measurement accuracy of amplitude and phase, and it was almost inversely proportional to the average power of 1/2. For example, when the measurement time is 0.1 second (10 Hz), the amplitude accuracy is about 1.7 μV and the phase accuracy is 5.1 m. FIG. 9B shows an average signal level of each detection coil when the fine marker 2 (see Table 1) is arranged at a point where the distance from the detection coil is 80 mm using this measuring apparatus, and FIG. The S / N ratio with the amplitude angle is obtained. A maximum S / N ratio of about 100 was obtained.

  FIG. 10A shows a comparison of the S / N ratio in the same configuration as described above using a commercially available network analyzer (MS4630B) instead of the AD converter used in the present invention and using the marker 2. FIG. 10B shows the absolute position accuracy of the marker at that time. The RBW of the network analyzer was 100 Hz, and the averaging count was 10 times. In the range of about 40 mm, which is near the center of FIG. 10B, an absolute position accuracy within 1 mm was obtained, and the SN ratio was about 50 or more. This SN ratio was lower than the SN ratio when the detector of the present invention was used.

From the above, it can be said that the measurement accuracy necessary for obtaining the absolute position accuracy of about 1 mm was obtained using the measurement unit prototyped in the present invention.
(4-2) Position and Direction of Magnetic Marker FIG. 11 shows the position and direction of the marker 1 according to the present invention. The marker is a marker having a diameter of 6 mm and a length of 20 mm shown in FIG. The position was moved about 100 mm in 10 mm increments in the x-axis, y-axis, and z-axis directions, with the distance from the detection coil being 80 mm as a reference. However, since the coordinate system of the detection coil and the coordinate system of the marker moving micrometer do not match, the coordinates of the obtained marker are slightly inclined. The normal direction of the marker coil was arranged so as to be substantially parallel to the y-axis direction in the figure. The measurement cycle was 1 Hz. The coordinate axes are shown in FIG. FIG. 11A shows the position in the xz plane, and FIG. 11B shows the position in the yz plane. (2) is an actual measurement value, and a broken line is a theoretical value. The broken line is represented by a straight line parallel to and substantially corresponding to the trace of the actual measurement value. Furthermore: ◆ in the broken line represents the marker position in 10 mm increments, indicating the theoretical position of the marker. From FIG. 11 (b) and FIG. 11 (c), it is determined that the position of the marker is generally measured correctly. FIG. 11 (d) shows the absolute position accuracy. The absolute position accuracy was defined by the distance between the three-dimensional positions of ■ and ◆ in FIGS. 11 (a) and 11 (b). The abscissa shows the movement distance with respect to the reference position normalized. According to FIG. 11D, the absolute position accuracy within 1.5 mm is obtained within a maximum distance of 130 mm from the surface of the detection coil. Absolute position accuracy within 1 mm was obtained at about 88% of the measurement points.

  FIG. 11E shows the direction angle of the marker. φ is an angle formed by the direction vector and the z-axis. In the experimental arrangement, the normal component of the coil is almost parallel to the y-axis, and θ cannot be defined. The horizontal axis is expressed as the movement distance from the reference point. A value of about 0 degrees was obtained for φ. The absolute angle accuracy was within ± 4 degrees.

  FIG. 12 shows the position and direction obtained using the fine marker 2 according to the present invention. The marker moving method was the same as in FIG. The measurement cycle was 1 Hz.

  FIG. 12A shows the position of the marker in the xy plane, and FIG. 12B shows the position of the marker in the xz plane. The marker position was measured approximately accurately. FIG. 12 (c) shows the absolute position accuracy. The positional accuracy was within 1.6 mm within the experimental range. The absolute position accuracy was within 1 mm at about 91% of all the measurement points, and it is considered that the target was generally achieved. FIG. 12D shows an angle profile. The angular accuracy was generally within ± 4 degrees.

(4-3) Consideration on Positional Accuracy FIG. 13 shows error voltages for each detection coil when two types of markers are arranged at a reference point (the distance from the detection coil array is about 80 mm). . The error voltage was calculated by the following equation (6).

V ⁽ⁱ⁾ _error = V ⁽ⁱ⁾ _mk -v ⁽ⁱ⁾ _c (6)
Where V _mk is a measured value of the marker contribution voltage, V _c is a calculated value obtained by converting the magnetic flux density obtained by substituting the optimized position and direction into the above equation (2), and i is a detection coil. Is the number.

  According to FIG. 13, the error voltage at the marker 1 (coil diameter: 6 mm, coil length: 20 mm) is sufficiently larger than the noise level of the measuring instrument, and the positional accuracy using this marker is the dimensions of the marker and the detection coil. Due to the effect, the error from the dipole magnetic field is considered as the main factor.

  On the other hand, although the error voltage in the fine marker 2 (coil diameter: 1.2 mm, coil length: 10 mm) was slightly larger than the noise level of the measuring instrument, it was almost on the same order. For this reason, it is considered that the error factor in this marker is caused by both the size effect of the marker and the detection coil and the noise of the measuring instrument.

As mentioned above,
(1) With the LC resonance type magnetic marker position detection system of the present invention, a position detection system based on real-time operation using phase information could be developed.

  (2) The absolute position accuracy was within 1.5 mm with a marker having a diameter of 6 mm and a length of 20 mm inside a cube having a maximum distance of 130 mm from the detection coil and a side of 100 mm. The absolute position accuracy was within 1 mm at about 88% of all measurement points.

  (3) Using a marker having a marker coil diameter of about 1.2 mm and a length of 10 mm, the absolute position accuracy was within 1.6 mm within the above range. The absolute position accuracy was within 1 mm at about 91% of all measurement points.

  Further, the present invention can detect not only the position and direction using phase information but also the equivalent magnetic moment of the marker.

  FIG. 14 is a diagram showing the arrangement of the magnetic field sensor and the marker when detecting the equivalent magnetic moment of the marker according to the present invention, and FIG. 15 is proportional to the magnetic field intensity felt by the marker with respect to the normalized position (mm) of the marker. It is a figure which shows the equivalent magnetic moment (Wbm) to do.

  As shown in FIG. 14, a magnetic field sensor (pickup coil array) 21 is arranged on one surface behind a rectangular parallelepiped, and an LC resonance type magnetic marker 22 facing in the Z-axis direction is arranged for each of X, Y, and Z. Move parallel to the axis. The exciting coil 23 is disposed on the front surface of the rectangular parallelepiped. Here, for the movement with respect to the Z axis, the direction away from the magnetic field sensor 21 is defined as the negative direction. The exciting coil 23 is in the vicinity of −30 mm on the horizontal axis of FIG.

  As the marker 22 moves away from the exciting coil 23, the magnetic flux interlinking the marker decreases, so the equivalent magnetic moment (proportional to the magnetic field strength) is reduced. The magnetic field was maximized in the vicinity of the exciting coil 23. The equivalent magnetic moment value is maximized. In addition, in the movement in the direction parallel to the X direction and the Y direction, the equivalent magnetic moment value does not change, but slightly decreases at the end. Considering that the marker 22 detects the Z-axis component of the magnetic field generated from the exciting coil 23, it is a reasonable result that the Z-axis component of the magnetic field intensity decreases toward the end.

  From the above, it was shown that the magnetic field in the normal direction of the marker coil can be measured by obtaining the equivalent magnetic moment.

  In addition, this invention is not limited to the said Example, Based on the meaning of this invention, a various deformation | transformation is possible and these are not excluded from the scope of the present invention.

  The position and direction detection system of the high-accuracy LC resonance type magnetic marker of the present invention can be used as a position detection system based on real-time operation using phase information.

It is a schematic diagram of the position detection system by the high precision LC resonance type magnetic marker concerning this invention. It is a flowchart for calculating | requiring the position and direction of the high precision LC resonance type | mold magnetic marker concerning this invention. It is explanatory drawing of the measurement of the induced voltage using the amplitude which the present inventors already proposed. It is explanatory drawing of the measurement of the induced voltage using the phase of this invention. It is a figure which shows the structure of the position detection system made as a prototype concerning this invention. It is a photograph (substitute figure) of a PXI controller (built-in AD converter and DA converter), a preamplifier, and a display used for the measurement system concerning the present invention. It is a photograph (substitute figure) of the exciting coil, detection coil, and marker concerning this invention. It is a photograph (substitute figure) of the LC resonance type marker made as a prototype according to the present invention. It is the figure which showed the measurement accuracy of the amplitude in the measurement system concerning this invention with respect to measurement time. It is a figure which shows the relationship between SN ratio and position accuracy using the network analyzer concerning this invention. It is the figure which showed the position and direction of the marker 1 concerning this invention. It is the figure which showed the position and direction obtained using the fine marker 2 concerning this invention. It is a figure which shows an error voltage with respect to each detection coil in case the two types of markers concerning this invention are arrange | positioned in the reference | standard point (the distance from a detection coil array is about 80 mm). It is a figure which shows arrangement | positioning of the magnetic field sensor and marker in the case of detecting also the equivalent magnetic moment of the marker concerning this invention. It is a figure which shows the equivalent magnetic moment (Wbm) proportional to the magnetic field intensity which the marker with respect to the normalized position (mm) senses.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11,23 Excitation coil 2,12 Detection coil 3,13,22 LC resonance type magnetic marker 14 AD converter and DA converter 15 AD converter 16 Preamplifier 16
21 Magnetic field sensor (Pickup coil array)

Claims (2)

(A) an exciting coil;
(B) a plurality of detection coils opposed to the excitation coil;
(C) an LC resonance type magnetic marker disposed between the excitation coil and the detection coil;
(D) Measurement in which the excitation coil generates an alternating magnetic field tuned to the resonance frequency of the LC resonance type magnetic marker, and an induction magnetic field from the LC resonance type magnetic marker is measured by each detection coil of the plurality of detection coils. Means,
(E) means for measuring a first induced voltage by the detection coil in a state where the LC resonance type magnetic marker is set;
(F) means for measuring a second induced voltage by the detection coil in a state where the LC resonance type magnetic marker is not set;
(G) means for determining a phase difference between the first induced voltage and the second induced voltage;
And (h) means for determining a contribution voltage of the LC resonance type magnetic marker based on the phase difference, and the position, direction and equivalent magnetic moment of the high precision LC resonance type magnetic marker by phase measurement. Detection system.   2. The system for detecting the position and equivalent magnetic moment of a high-accuracy LC resonant magnetic marker according to claim 1, wherein the measuring means is connected in parallel to the same number of high-speed AD converters as the detection coils of the plurality of detection coils. System for detecting the position, direction, and equivalent magnetic moment of a high-precision LC resonance type magnetic marker, characterized in that the SNR and the SN ratio are increased.