EA045848B1 - DEVICE FOR VISUALIZING DISTRIBUTION OF RESPONSE TO EXTERNAL FIELD AND METHOD FOR VISUALIZING DISTRIBUTION OF RESPONSE TO EXTERNAL FIELD - Google Patents

Description

Field of technology to which the invention relates

The present invention relates to an external field response distribution imaging apparatus and the like that generates an image representing the external field response distribution.

BACKGROUND OF THE INVENTION

Patent Document (PTL) 1 discloses a device that obtains a field distribution by measurement. The apparatus obtains a magnetic force image of the magnetic field strength distribution in a first measurement plane above the sample, obtains an auxiliary magnetic force image by performing a measurement in a second measurement plane that is at a small distance d from the first measurement plane, and then obtains an image of magnetic force gradients by dividing the difference between them by a small distance d. The magnetic force image and the auxiliary magnetic force image are Fourier transformed and substituted into the three-dimensional field equation derived from the general solution of Laplace's equation to obtain the three-dimensional field indicating the magnetic force.

The device disclosed in PTL 1 can obtain the state of magnetic domains on the surface of a sample with high accuracy by obtaining a three-dimensional field.

Bibliography

Patent document

PTL 1.: WO 2008/123432.

The essence of the invention

Technical problem

However, the device disclosed in PTL 1 is capable of producing magnetic domains only on the surface of the sample. Obtaining the state of magnetic domains in regions deeper than on the sample surface is a difficult task. In other words, it is difficult to obtain the distribution of magnetic susceptibility (i.e., the distribution of response to an external field) of the internal region of the sample.

In this regard, the present invention provides an external field response distribution imaging apparatus and the like, which can accurately generate an image representing the external field response distribution in a region including an interior region of an object.

Solution

An apparatus for visualizing an external field response distribution in accordance with one aspect of the present invention produces an image representing an external field response distribution, which is a distribution of responses to an external field, and includes: an excitation (induction) circuit that produces a first field component of each of the excitation positions specified outside the object in the form of positions relative to the object; a sensor that measures, at each of the measurement positions defined outside the object as positions relative to the object, a field strength containing a second field component created by the object under the influence of the first field component, to measure the field strength at the measurement positions for each of the excitation positions; and an information processing circuit that receives the field strength measurement result and generates an image representing the distribution of the response to the external field in a zone including the interior region of the object based on the measurement result. Information processing circuit: calculates a field function depending on the excitation position, which takes the virtual excitation position and the virtual measurement position as input, and outputs the field strength at the virtual measurement position, using the measurement result as the boundary condition; calculates an imaging function that takes the imaging target position as input and outputs an image intensity at the imaging target position, and is determined based on the strength output from the field function dependent on the excitation position in response to input of the imaging target position, in the form of a virtual excitation position and a virtual sampling position, into a field function depending on the excitation position; and generates an image based on the imaging function.

The foregoing general or specific aspects may be implemented in the form of a system, device or apparatus, method, integrated circuit, computer program, or non-volatile computer-readable storage medium, such as a CD-ROM, or any combination thereof.

Beneficial effects of the invention

In accordance with one aspect of the present invention, an image can be formed representing with high accuracy the distribution of response to an external field in a zone including the interior region of an object.

Brief description of drawings

Fig. 1 is a configuration diagram of a first example of a magnetic susceptibility distribution imaging apparatus according to an embodiment of the present invention.

Fig. 2 is a schematic diagram explaining the reconstruction of the magnetic field according to the reference example.

Fig. 3 is a schematic diagram for explaining a driving position and a sensing position according to an embodiment of the present invention.

Fig. 4 is a schematic diagram for explaining another example of a driving position and a sensing position according to an embodiment of the present invention.

Fig. 5 is a schematic diagram for explaining another example of a driving position and a sensing position according to an embodiment of the present invention.

Fig. 6 is a configuration diagram of a second example of a magnetic susceptibility distribution imaging apparatus according to an embodiment of the present invention.

Fig. 7 is a schematic diagram for explaining a first example of a body scanner according to an embodiment of the present invention.

Fig. 8 is a schematic diagram for explaining a drive circuit according to an embodiment of the present invention.

Fig. 9 is a schematic diagram for explaining a magnetic sensor according to an embodiment of the present invention.

Fig. 10 is a schematic diagram for explaining a specific structure of a magnetic sensor according to an embodiment of the present invention.

Fig. 11 is a schematic diagram for explaining a second example of a body scanner according to an embodiment of the present invention.

Fig. 12 is a schematic diagram for explaining a third example of a body scanner according to an embodiment of the present invention.

Fig. 13 is a schematic diagram for explaining a combination circuit of a magnetic sensor and an excitation circuit according to an embodiment of the present invention.

Fig. 14 is a schematic diagram for explaining a fourth example of a body scanner according to an embodiment of the present invention.

Fig. 15 is a schematic diagram for explaining a fifth example of a body scanner according to an embodiment of the present invention.

Fig. 16 is a schematic diagram for explaining a sixth example of a body scanner according to an embodiment of the present invention.

Fig. 17 is a schematic diagram for explaining an example of presenting information on an external terminal according to an embodiment of the present invention.

Fig. 18 is a schematic diagram for explaining an example of a security verification system according to an embodiment of the present invention.

Fig. 19 is a flowchart showing the operation of a magnetic susceptibility distribution imaging apparatus according to an embodiment of the present invention.

Description of Embodiments

For example, an apparatus for imaging an external field response distribution in accordance with one aspect of the present invention generates an image representing an external field response distribution, which is a distribution of responses to an external field, and includes: a drive circuit that produces a first field component from each from excitation positions specified outside the object in the form of positions relative to the object; a sensor that measures, at each of the measurement positions defined outside the object as positions relative to the object, the strength of a field containing a second field component created by the object under the influence of the first field component, so as to measure the field strength at the measurement positions for each of the excitation positions; and an information processing circuit that receives the field strength measurement result and generates an image representing the distribution of the response to the external field in a zone including the interior region of the object based on the measurement result. Information processing circuit: calculates the field function depending on the excitation position, which takes the virtual excitation position and the virtual measurement position as input, and outputs the field strength at the virtual measurement position, using the measurement result as the boundary condition; calculates an imaging function that takes the imaging target position as input and outputs the image intensity at the imaging target position, and is determined based on the strength output from the field function dependent on the excitation position in response to input of the imaging target position, in the form of a virtual excitation position and a virtual sampling position, into a field function depending on the excitation position; and generates an image based on the imaging function.

This allows the external field response distribution imaging device to generate an image representing with high accuracy the external field response distribution in an area including the interior of the object, based on the field strength measurement result, based on various combinations of excitation positions and measurement positions.

- 2 045848

For example, the information processing circuit calculates, as a field function depending on the excitation position, a solution to the Laplace equation satisfied by the field function depending on the excitation position, using the measurement result as a boundary condition.

This allows the device for visualizing the distribution of the response to the external field to correctly derive the field function depending on the excitation position, based on the measurement result and the Laplace equation related to the multipath problem in a static or quasi-static field.

For example, the information processing circuit calculates, as an imaging function, the limit value of the field function depending on the excitation position, through the operation of taking the limit of the field function depending on the excitation position, which orients the virtual excitation position and the virtual measurement position input to the field function depending on from the excitation position, to the imaging target position.

This allows the external field response distribution imaging device to correctly derive the imaging function based on the field function depending on the excitation position.

For example, drive positions are specified in a first plane, and sensing positions are specified in a second plane that is the same as or different from the first plane.

This allows the device to visualize the distribution of the response to the external field to avoid increasing the size of the space required to accommodate the excitation circuit and the sensor. A device for visualizing the distribution of the response to an external field can also limit the complexity of the calculation process.

For example, the sensing positions are located on the first side of the object, and the excitation positions are located on the second, opposite side of the object.

This allows the device to visualize the distribution of response to an external field to measure the field strength at each of the sampling positions that are on the opposite side of the object with respect to the excitation positions. Accordingly, the device for visualizing the distribution of the response to the external field can suppress the influence of the first field component generated by the drive circuit when measuring the field strength at each of the measurement positions.

For example, the sensing positions and the excitation positions are located on the same side of the object.

This allows the external field response distribution imaging device to measure the field strength at each of the sampling positions that are on the same side of the object as the excitation positions. This allows the device to visualize the distribution of the response to the external field to avoid increasing the size of the space required to accommodate the excitation circuit and the sensor.

For example, the drive circuit produces a first field component from each of the drive positions by moving to each of the drive positions, and the sensor measures the field strength at each of the sensing positions by moving to each of the sensing positions.

This allows the device for visualizing the distribution of response to an external field to implement one excitation circuit for multiple excitation positions and one sensor for multiple measurement positions. Accordingly, a device for visualizing the distribution of response to an external field can limit the increase in the cost of hardware.

For example, the drive circuit includes a plurality of drive circuits located at drive positions, and the sensor includes a plurality of sensors located at sensing positions.

This allows the device to visualize the distribution of the response to an external field to create a field component from each of the excitation positions without moving the excitation circuit or sensor and measure the field strength at each of the sampling positions. Accordingly, the apparatus for visualizing the distribution of the response to the external field can quickly obtain a measurement result corresponding to a plurality of driving positions and a plurality of sampling positions.

For example, a plurality of drive circuits are located in a first plane, and a plurality of sensors are located in a second plane that is the same as or different from the first plane.

This allows the device for visualizing the distribution of the response to the external field to quickly obtain a measurement result corresponding to excitation positions in the first plane and measurement positions in the second plane.

For example, a plurality of drive circuits are located on a first line, and a plurality of sensors are located on a second line that is the same as or different from the first line.

This allows the device for visualizing the distribution of response to an external field to reduce the space in which the excitation circuits are located and the space in which the sensors are located.

For example, an object is moving, the excitation circuit generates a first field component from each of the excitation positions specified relative to the object that is moving by generating the first field component from a predetermined position at different times, and the sensor measures the field strength at each of the sensing positions specified relative to an object that is moving by measuring the field strength at a predetermined position in

- 3 045848 different points in time.

This allows the apparatus for visualizing the distribution of the response to an external field to generate a field component from each of the excitation positions, without providing multiple excitation loops or multiple sensors and without moving the excitation loop or sensor, and measure the field strength at each of the sampling positions.

For example, the drive circuit is enclosed in a first wall and the sensor is enclosed in a second wall that is the same as or different from the first wall.

This allows the external field response distribution imaging device to produce an image representing the external field response distribution without being noticed by humans.

For example, the excitation circuit and the sensor are enclosed in the floor.

This allows the external field response distribution imaging device to produce an image representing the external field response distribution without being noticed by humans.

For example, the drive circuit is enclosed in a first post and the sensor is enclosed in a second post that is the same as or different from the first post.

This allows the external field response distribution imaging device to produce an image representing the external field response distribution unbeknownst to humans.

For example, in the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position is expressed as (y1, z1), the virtual sampling position is expressed as (x, y ₂ , z ₂ ), z-coordinate of the contour position excitation is set to 0, and the z-coordinate of the sensor position is set to z ₀ , the field function depending on the excitation position is defined as:

[expression 1]

F%U1.U2.21,2 ₂ )

OO CO CO = [ ί ia(k _x ,k _v

IIV ^x> Y1' y-iJ x Yx Y2 ' a(k _x ,k _Y1 ,k _Y2 ) = f(k _x ,k _Y1 ,k _y2 ,z ₁ = 0,z ₂ = z ₀ )

The Fourier image of the measurement result is expressed as:

[expression 2] f(k _x ,k _Y1 ,k _y2 ,z ₁ = 0,z ₂ = z ₀ ) where k _x , k _y1 and k _y2 are the wave numbers corresponding to x, y ₁ and y ₂ , and the function image formation is defined as:

[expression 3]

Ф<У у, z) = ^Ljm^ Ф {х, y _lt у ₂ , z^zj

Z ₂ ->Zj=Z

OO CO OO .______________ = Lira ί ί [ a(k _x ,k _v ,k _U U ^k * ^x+ ' ^k »U1 ⁺ ' ^k ?^

Y2^Y1 ⁼ Y III < * Y1 Y^y x Y1 Yr ^Z 2~* ^z l ^{- Z -co -co} -co

This allows the external field response distribution imaging apparatus to generate an image representing the external field response distribution with high accuracy using the excitation position dependent field function expressed by the above equation and the imaging function expressed by the above equation.

For example, in the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position is expressed as (y1, z1), the virtual sensing position is expressed as (x, y2, _z2 ), z-coordinate of the excitation loop position is set to 0, and the z-coordinate of the sensor position is set to z ₀ , the field function depending on the excitation position is defined as:

[expression 4]

Ф(х.У1,У2^1,г ₂ ) = fl J а(к _x , к _У1 ,к _У2 У ^к * ^x+1к у^ ⁺ ^ dk _x dk _Vi dk _y2 , ζ ί /с I - a {k _x ,k _ye k _y ^ = e f(k _x ,k _U1 ,k _U2 ,g ₁ = 0,z ₂ = z ₀ )

The Fourier image of the measurement result is expressed as:

[Expression 5] = 0,ζ ₂ = ζ ₀ ) where k _x , k _y1 and k _y2 are the wave numbers corresponding to x, y1 and y ₂ and the imaging function is defined as:

- 4 045848

[expression 6] f(x,Y,A - Lim Φ(χ,γ ₁ ,γ ₂ ,ζ ₁ ,ζ ₂ ) Уг^У1-У z ₂ ->z _r =z су co co

- Lim ff ( a(k,L _y A _v .)e ^ik * ^x+ik viyi ^+ik y^^

У2~ ^, У\ ⁼ У III ^xx У1 Уг ζ ₂ ^ζ _Ύ =ζ

This allows the external field response distribution imaging apparatus to generate an image representing the external field response distribution with high accuracy using the excitation position dependent field function expressed by the above equation and the imaging function expressed by the above equation.

For example, in the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position is expressed as (x1, y, z ₁ ), the virtual sampling position is expressed as (x ₂ , y, z ₂ ), z- The excitation loop position coordinate is set to 0, and the z-coordinate of the sensor position is set to z ₀ , the field function depending on the excitation position is defined as: [Expression 7]

ФСхрХг.у, ζ^,ζ^

OO OO co ⁼ / / / - CO -co -co a(k _X1 ,k _X2 ,k _y ) = f(k _X1 ,k _X2 ,k _y ,g ₁ = 0,z ₂ = ζ ₀ )

The Fourier image of the measurement result is expressed as:

[Expression 8] = 0,ζ ₂ = ζ ₀ ) where k _x1 , k _x2 and k _y are the wave numbers corresponding to x1, x ₂ and y, and the imaging function is defined as:

[expression 9]

1f(x,U,Yu = ₁ it^F(x ₁ ,x ₂ ,y,g ₁ ,g ₂ ) Z ₂ -*?1 -ζ SO OO co .____________ .____________ = _X2 Yt _=x ί ί C (/< _X1 , z ₂ 'Ζ _Ί ~ζ

This allows the external field response distribution imaging apparatus to generate an image representing the external field response distribution with high accuracy using the excitation position dependent field function expressed by the above equation and the imaging function expressed by the above equation.

For example, in the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position is expressed as (x ₁ , y, z ₁ ), the virtual sampling position is expressed as (x ₂ , y, z ₂ ), z -coordinate of the excitation circuit position is set equal to 0, and z-coordinate of the sensor position is set equal to z ₀ , the field function depending on the excitation position is defined as: [expression 10] Φ^,χ^γ,ζ^ζ^) SY OO CO ____________ _____________ = 11 I a(k _X1 ,k _X2 ,ku)e' ^k *1 ^x ^ ^k *g ^x ^ ^k yYe~^ - CO -co -co

I-----2------2 a(k _X1 ,k _Xz ,k _y ) = ^+liy Ф(k _Xg ,k _X1 ,k _y , ₂₁ = 0,z ₂ = z ₀ )

The Fourier transform of the measurement result is expressed as: I[Expression 11] = 0,z ₂ = z ₀ ) where k _x1 , k _x2 and k _y are the wave numbers corresponding to x1, x ₂ and y, and the imaging function is defined in form:

[expression 12]

Ιφ(χ,γ,ζ) = _X2 Lim _=x 0(x ₁ ,x ₂ .yz ₁ ,z ₂ ) ^Ζ 2^ ^Ζ 1 -Ζ CO CO CO ._____________ ______________ = _X2 Tt _=x JJJ a(k _Xt ,k _X2 ,k _y )e ^ik *i^ ^+ik *2 ^x ? ^+ik yye~F^ _ _co

- 5 045848

This allows the external field response distribution imaging apparatus to generate an image representing the external field response distribution with high accuracy using the excitation position dependent field function expressed by the above equation and the imaging function expressed by the above equation.

For example, the information processing circuit determines whether an object contains a detection target based on an image, and, when it is determined that the object includes a detection target, outputs information indicating the location of the detection target or object to an external terminal.

This allows the apparatus for visualizing the distribution of the response to the external field to notify the location of a particular detection target or the location of an object including a particular detection target.

For example, a method for visualizing an external field response distribution for generating an image representing an external field response distribution, which is a distribution of external field responses, includes: the step of generating, by a driving circuit, a first field component from each of externally defined driving positions object in the form of positions relative to the object; a step of measuring, by the sensor, at each of the measurement positions specified outside the object in the form of positions relative to the object, a field strength containing a second field component created by the object under the influence of the first field component, to measure the field strength at the measurement positions for each of the excitation positions; and the step of obtaining a field strength measurement result and generating an image representing the distribution of the response to the external field in a zone including an interior region of the object based on the measurement result. The acquisition and generation step includes: computing a field function dependent on the excitation position, which takes the virtual excitation position and the virtual measurement position as inputs, and outputs the field strength at the virtual measurement position, using the measurement result as a boundary condition; calculating an imaging function that takes the imaging target position as input and outputs the image intensity at the imaging target position, and is determined based on the strength output from the field function dependent on the excitation position in response to the input of the imaging target position, in the form of a virtual excitation position and a virtual sampling position, into a field function depending on the excitation position; and generating an image based on the imaging function.

This allows the formation of an image representing, with high accuracy, the distribution of the response to the external field in a zone including the internal region of the object, based on the result of the field strength measurement, based on various combinations of excitation positions and measurement positions.

Hereinafter, embodiments will be described with reference to the drawings. Each of the following embodiments represents a general or specific example. The numerical values, shapes, materials, elements, arrangement and connection of elements, steps, order of steps, etc. presented in the following embodiments are merely examples and do not limit the scope of the claims.

Hereinafter, as one example of an apparatus for imaging a response distribution to an external field, a magnetic susceptibility distribution imaging apparatus that uses a magnetic field will be described hereinafter. The components of the magnetic field described below are the components that add up to the magnetic field. The components of the magnetic field can be each of several magnetic fields that add up to the total magnetic field.

Embodiments

Fig. 1 is a configuration diagram of a first example of a magnetic susceptibility distribution imaging apparatus according to the present embodiment. The device 100 for visualizing the distribution of magnetic susceptibility shown in FIG. 1 includes a drive circuit 110, a drive circuit drive 120, a magnetic sensor 130, a magnetic sensor drive 140, an information processing circuit 150, a display 160, and a sample table 170. The magnetic susceptibility distribution imaging apparatus 100 generates an image representing the magnetic susceptibility distribution in a zone including the interior region of a sample placed on the sample table 170 . This image may show magnetic material, particularly ferromagnetic material, contained in the sample.

The excitation (induction) circuit 110 is an electrical circuit that produces (induces) a magnetic field component. The drive circuit 110 may be a coil or an electrical wire. Here, the magnetic field component generated by the drive circuit 110 is called the first magnetic field component. In the example shown in FIG. 1, the drive circuit 110 moves. Therefore, the drive circuit 110 produces a first magnetic field component from each of the drive positions. The first magnetic field component produces the magnetic field component from the sample. Here, the magnetic field component created from the sample is called the second

- 6 045848 components of the magnetic field.

The drive circuit actuator 120 is a drive that moves the field circuit 110. The field circuit actuator 120 moves the field circuit 110 to each of the field positions. In this case, the excitation circuit 110 produces a first magnetic field component from each of the excitation positions.

Magnetic sensor 130 is a sensor that measures magnetic characteristics. The magnetic sensor 130 may be a tunnel magnetic resistive (TMR) element, a supermagnetoresistive (GMR) element, a superconducting quantum interferometric (SQUID) element, or a magnetic impedance (MI) element.

In the example shown in FIG. 1, the magnetic sensor 130 moves. Magnetic sensor 130 measures, at each sampling position, magnetic characteristics in a magnetic field containing a second magnetic field component created by the sample. Here, the magnetic sensor 130 measures the magnetic characteristics at the measurement positions for each of the excitation positions.

The magnetic sensor actuator 140 is an actuator that moves the magnetic sensor 130. The magnetic sensor actuator 140 moves the magnetic sensor 130 to each of the sensing positions. In this case, the magnetic sensor 130 measures the magnetic characteristics at each of the measurement positions.

The information processing circuit 150 is an electrical circuit that performs information processing. The information processing circuit 150 may be, for example, a computer or a computer processor. The information processing circuit 150 receives the measurement result of the magnetic characteristics and, based on the measurement result, generates an image representing the distribution of magnetic susceptibility in the area including the internal region of the sample.

Specifically, the information processing circuit 150 calculates a magnetic field function depending on the excitation position using the measurement result as a boundary condition. The excitation position-dependent magnetic field function is a function that takes the excitation position of the first magnetic field component and the magnetic measurement position as input, and outputs the magnetic field strength at the measurement position.

Then, the information processing circuit 150 calculates an image generation function. The imaging function is a function that takes the imaging target position as input and outputs the image intensity at the imaging target position, and is determined based on the strength output from the excitation position-dependent magnetic field function in response to input of the imaging target position images, in the form of excitation position and measurement position, into a function of the magnetic field depending on the excitation position. Then, the information processing circuit 150 generates, based on the imaging function, an image representing the distribution of magnetic susceptibility in the area including the interior region of the sample.

The information processing circuit 150 may output the generated image, for example, to a display 160. For example, the information processing circuit 150 may represent the image on the display 160 by outputting the image to the display 160. Alternatively, the information processing circuit 150 may print the image on a printer (not shown). in the drawings) by outputting the image to a printer. Alternatively, the information processing circuit 150 may transmit the image in electronic data format to another device (not shown in the drawings) via wired or wireless communications.

The display 160 is a display device such as a liquid crystal display. It should be noted that the display 160 is an optional component and not a required component. The display 160 may be an external device, not included in the device 100, for visualizing the distribution of magnetic susceptibility.

The sample table 170 is a table on which the sample is placed. It should be noted that the sample table 170 is an optional component and not a required component. The magnetic susceptibility distribution imaging device 100 may form an image of a sample that is not placed on the sample table 170 or the like. The sample table 170 may be an external component not included in the device 100 for imaging the magnetic susceptibility distribution. The sample can be an electrical circuit or any other object.

The magnetic susceptibility distribution imaging device 100 measures sample-dependent magnetic characteristics while changing the relative position between the sample, the excitation position, and the measurement position. This allows the magnetic susceptibility distribution imaging device 100 to obtain sufficient information about the magnetic susceptibility distribution in a zone including the interior region of the sample. In such a case, the magnetic susceptibility distribution imaging device 100 can calculate a magnetic field function depending on the excitation position based on the obtained sufficient information, and can generate an image representing the magnetic susceptibility distribution with high accuracy based on the calculated magnetic field function depending on excitation positions.

- 7 045848

For example, the magnetic susceptibility distribution imaging device 100 can generate a high-precision image by combining the results of multiple measurements corresponding to multiple combinations of excitation positions and sensing positions.

Fig. 2 is a schematic diagram explaining the reconstruction of a magnetic field according to the reference example. A static magnetic field in a space in which there is no source of magnetic field satisfies the equation (1-1) below, based on Maxwell's equations.

I[expression 13]

ΔΗ _Ζ = О • · · (1 - 1)

H _z in the above (1-1) means the magnetic field in the z-direction in the Cartesian xyz coordinate system and corresponds to the z-component of the magnetic field vector. Δ is the Laplacian, also known as the Laplace operator. The general solution for the above (1-1) can be expressed as the sum of a term that increases exponentially in the z-direction and a term that decreases exponentially in the z-direction, as shown in (1-2) below.

[expression 14]

N _g (x, y, z) = if ία(k _x , k _y )e ^Z ^l^~^~ + b(k _x , ky)e ^g 1 \41T) JJ { J • -(1-2 )

In the above equation (1-2), k _x and k _y represent the wave numbers in the x- and y-directions, respectively. In addition, a(k _x , k _y ) and b(k _x , k _y ) are functions expressed in terms of k _x and k _y . For example, the measurement gives the z-component H _z (x, y, 0) of the magnetic field vector in the z=0 plane, and the gradient δ/δzH _z (x, y, z)|z= ₀ in the z-direction for the z-component magnetic field vector. Using this, a(k _x , k _y ) and b(k _x , k _y ) in (1-2) can be obtained as shown below in (1-3) and (1-4), respectively.

[expression 15]

[expression 16] b(k _x ,k

In the above equations (1-3) and (1-4), f(k _x , k _y ) is the two-dimensional Fourier transform of H _z (x, y, 0), and g(kx, k _y ) is the two-dimensional Fourier transform -image for δ/δzH _z (x, y, z)| _z = ₀ . By substituting (1-3) and (1-4) into (1-2), one can obtain H _z as shown below in (1-5).

[expression 17]

H _z {x,y, z) (27)

Using the above method, you can obtain H _z (x, y, z) with any z-coordinate in a space in which there is no source of magnetic field, using Hz(x, y, 0), which is the Dirichlet boundary condition, and δ/ δzH _z (x, y, z)| _z = ₀ , which is the Neumann boundary condition. This means that the magnetic field on the sample surface can be reconstructed from the magnetic field in the measurement plane, which is the xy plane at z=0.

However, the equations applied in the above method are valid in space in which there is no source of magnetic field. Therefore, using the above method alone, it is difficult to reconstruct the magnetic field deeper than on the surface of the sample. In other words, using the above method alone, it is difficult to visualize the magnet distribution

- 8 045848 susceptibility inside a sample that includes a magnetic field source.

In contrast, the magnetic susceptibility distribution imaging device 100 according to the present embodiment calculates a magnetic field function depending on the excitation position from a measurement result obtained by measuring magnetic characteristics while changing the sample location, the excitation position and the measurement position relative to each other. Then, the magnetic susceptibility distribution imaging device 100 generates an image representing the magnetic susceptibility distribution based on the magnetic field function depending on the excitation position. In other words, the magnetic susceptibility distribution imaging device 100 can reconstruct the magnetic field in a region deeper than the surface of the sample.

Fig. 3 gives a schematic diagram for explaining the driving position and the sensing position according to the present embodiment. In the example shown in FIG. 3, the excitation position and the measurement position are presented in the Cartesian xyz coordinate system.

In particular, the drive circuit 110 is an electrical wire through which current flows parallel to the x-axis. Therefore, the position of the drive circuit 110 is expressed as T _LINE (y ₁ , z1). In other words, the excitation position is expressed as T _LINE (y ₁ , z1). Since the magnetic sensor 130 may have an x-coordinate, a y-coordinate and a z-coordinate, the position of the magnetic sensor 130 is expressed as R _TMR (x, y ₂ , z ₂ ). In other words, the measurement position is expressed as R _TMR (x, y ₂ , z ₂ ).

In the example in FIG. 3, the position of the sample is indicated by P. The sample can also be described as an inductive magnetic field source. The magnetic field component is transferred in the following order: ^T LINE ⁽ y1, ^z 1) ^- > ^{P -} > RTMR ^(x , Y2, ^z 2).

At the excitation position T _LINE (y ₁ , z1 ) and the measurement position R _TMR (x, y ₂ , z ₂ ), the magnetic field strength at the measurement position R _TMR (x, y ₂ , z ₂ ) can be expressed as Φ(x , y1, y ₂ , z1, z ₂ ). Φ(x, y1, y ₂ , z1, z2) is a magnetic field function depending on the excitation position, which takes the excitation position T _LINE (y ₁ , z1) and the measurement position R _TMR (x, y ₂ , z ₂ ) at as input data and outputs the magnetic field strength at the R _TMR (x, y ₂ , z ₂ ) measurement position.

The drive position T _LINE (y ₁ , z1) may be a virtual position of the drive loop 110 . The sensing position R _TMR (x, y ₂ , z ₂ ) may be a virtual position of the magnetic sensor 130. If the drive position T _LINE (y ₁ , z1) corresponds to the actual position of the drive circuit 110, and the sensing position RTMR(x, y2, z2) corresponds to the actual position of the magnetic sensor 130, then Φ(x, y1, y ₂ , z1, z ₂ ) corresponds to the measured value, which is the actual measurement result.

In the example shown in FIG. 3, the drive circuit 110 has a z=0 coordinate and scans in the y-axis direction. The magnetic sensor 130 has a coordinate z=z ₀ and scans in the x- and y-axis directions in the xy plane. This gives Φ(x, y1, y ₂ , z1=0, z ₂ =z ₀ ) as the measured value for each combination of x, y1 and y ₂ . This measured value is used as a boundary condition for the magnetic field function depending on the excitation position, which is Φ(x, y1, y ₂ , z1, z ₂ ).

Φ(x, y1, y ₂ , z1, z ₂ ) is a harmonic function depending on y1 and z1 corresponding to the excitation position T _LINE (y ₁ , z1), and a harmonic function depending on x, y ₂ and z ₂ , corresponding to the position R _TMR (x, y ₂ , z ₂ ) of the measurement. Therefore, Φ(x, y1, y ₂ , z1, z ₂ ) satisfies (2-1) and (2-2) given below as fundamental equations, which are Laplace's equations related to a multipath problem in a static or quasi-static field .

[expression 18] / d ² d ² \ xru^ oz^J • · «(2-1)

[expression 19] ( d ² d ² d ² \ (^+^+^)^^^=° • · · (2-2)

When the z-coordinate of the sample position P is greater than the z-coordinate of the excitation circuit 110 and less than the z-coordinate of the magnetic sensor 130, the general solution of equation (2-1) and the general solution of equation (2-2) can each be expressed as either a term that increases exponentially in the z-direction or a term that decreases exponentially in the z-direction. In particular, the general solution of equation (2-1) and the general solution of equation (2-2) can each be expressed as (2-3) and (2-4) below.

- 9 045848

[expression 20]

OO

Ф(х,УнУ2^1,2 ₂ ) = J a _z (k _y ^e ^1k y^e ^k y^ak _yr - OO • · · (2-3)

[expression 21] with with ._______________

Φ(χ-7ι-72-Ζι,ζ ₂ ) = J j\ ₂ (k _x ,k _yz )e ^ikxX+i ^^ -СО -СО • · · (2-4)

The combination of (2-3) and (2-4) can be expressed by the following equation (2-5). [expression 22] ¢(^-71-72-¾.¾) с с СО _____________ = III а(к _x ,к _У1 ,к _У2 У ^кхХ+ ^^ dk _x dk _yi dk _y2

-OO -OO -OO • · · (2 - 5)

Applying the measured values at z ₁ =0 and z ₂ =z ₀ as boundary conditions to (2-5) gives equation (2-6) below.

[expression 23] с с с ___________ ¢(^-71-72-0-¾) = JJ fa(k _x ,k _yi ,k _y Je ^lkxX+lk yi ^yi+lk y^^^ -СО -СО -СО • · · (2 - 6)

The inverse Fourier transform of (2-6) gives equation (2-7) below.

[expression 24] a^k _x ,k _Y1 ,k _y ^ = e Ф(k _x ,k _yi ,k _y2 ,Zi = 0, ζ ₂ = ζθ) • · · (2-7)

Below is the Fourier transform of the measured value:

[expression 25] f(k _x ,k _U1 ,k _y2 ,g ₁ = 0,ζ ₂ = ζ ₀ )

Therefore, the magnetic field function depending on the excitation position is expressed by the following equation (2-8).

[expression 26] ¢0-71.72-21-¾)

OO OO OO .______________ = III a(k _x ,k _U1 ,k _y2 U ^kxHik U1Uy ⁺ ^ a(k _x ,k _U1 ,k _U2 ) - e ^Z °< ^{x +ku2} Ф(k _x ,k _U1 ,k _У2 ,г ₁ = 0,z ₂ = z ₀ ) • · -(2-8)

By applying x --> x, y ₂ --> y ₁ (=y) and z ₂ --> z ₁ (=z) to the magnetic field function depending on the excitation position, the output is assumed to indicate the magnetic field strength , measured at (x, y, z) after creating a magnetic field component at (x, y, z). It is assumed that the stronger the magnetic characteristics, the higher the magnetic susceptibility, and it is assumed that the image representing a given magnetic field strength shows the distribution of magnetic susceptibility in a zone including the interior region of the sample. The imaging function for generating such an image is expressed by the following equation (2-9).

[expression 27] φ(χ, y, ζ) = _y2 ζ _{= y} Ф(x, У1, y ₂ - Ζι, z ₂ )

Z ₂ ^Zy=Z oo oo oo _____________ = _y Tshts / / / a(%, k _yi ,k _y2 )e ^lkxX+lk yy ^y ^ y ^{x + ku2 22} dk _x dk _y dk _y , ₂ z ₂ -> z _x =z _ _yu _ _yu _ _yu • · · (2-9)

The imaging function in (2-9) is a function that takes the imaging target position as input and outputs the image intensity at the imaging target position. The image intensity corresponds to the value obtained as the magnetic field strength at the output of the excitation position dependent magnetic field function in response to inputting the imaging target position into the function

- 10 045848 magnetic field, depending on the excitation position.

For example, the information processing circuit 150 of the magnetic susceptibility distribution imaging device 100 calculates a magnetic field function depending on the excitation position from the measurement result, which is the measured value, and equation (2-8). Then, the information processing circuit 150 calculates the imaging function based on the magnetic field function depending on the excitation position and (2-9). Then, the information processing circuit 150 generates, based on the imaging function, an image representing the magnetic susceptibility distribution. Specifically, the information processing circuit 150 generates an image consisting of the values output by the imaging function for each imaging target position in the form of an image representing the magnetic susceptibility distribution.

This allows the magnetic susceptibility distribution imaging device 100 to generate an image representing the magnetic susceptibility distribution with high accuracy using the above-described excitation position dependent magnetic field function and the imaging function.

It should be noted that equations such as the magnetic field function depending on the excitation position and the imaging function described above with reference to FIG. 3 are just examples; and equations such as the magnetic field function depending on the excitation position and the imaging function are not limited to the above examples. Other equations based on different conditions can be derived in a manner that is similar to the above method.

For example, in the example in FIG. 3, the magnetic sensor 130 and the drive circuit 110 are located on opposite sides of the sample, but the magnetic sensor 130 and the drive circuit 110 may be located on the same side of the sample. For example, when the z-coordinate P is less than the z-coordinate of the drive circuit 110 and less than the z-coordinate of the magnetic sensor 130, the above equation (2-3) can be replaced by the following equation (3-1).

[expression 28]

OO Ф(^УъУ2^1,г ₂ ) = J - OO • · · (з- 1)

Therefore, in this case, the magnetic field function depending on the excitation position is expressed by equation (3-2).

[expression 29]

Ф(л:-У1<У2^1^ ₂ )

CO CO OO _f = f ί ί a(k _x ,k _v

III \ x* У1' Уг J ^x Уд Л2 ' а(к _x ,к _У1 ,к _у2 ) = _e ² °^ ^kх +^У2 f^ _x ,к _У1 ,к _у2 ,г ₁ = 0,z ₂ = z ₀ ) • · -(3-2)

Moreover, in this case, the imaging function can be expressed by the following equation (3-3).

[expression 30] φ(χ, y, z) = Lira Ф(x, y ₂ , z _lt z ₂ )

У 2 ^У±~У z ₂ ^z ₁ =z = Lim iff a(k _x ,k _v ,k _v ^ ^kхХ+1к У1У ^1+1к УгУ ² e ^{kyiZ1 kx +ky2 Z2} dk _x dk _v dk _v У -^У-^У j J j У ^x ' У^ У24 X У1 У2 _ _{w —oo} _ _yu • · · (3-3)

Fig. 4 is a schematic diagram for explaining another example of a driving position and a sensing position according to the present embodiment. Exactly as in the example shown in FIG. 3, in the example shown in FIG. 4, the excitation position and the measurement position are presented in the Cartesian xyz coordinate system. In the example in FIG. 4, the drive circuit 110 is a coil. The drive circuit 110 and the magnetic sensor 130 are at positions with the same y-coordinate, and the y-coordinate of the drive circuit 110 and the y-coordinate of the magnetic sensor 130 change as one coordinate.

Therefore, the position of the drive circuit 110 is expressed as T _COIL (x ₁ , y, z1). In other words, the excitation position is expressed as T _COIL (x ₁ , y, z1). The position of the magnetic sensor 130 is expressed as R _TM R(x ₂ , y, z ₂ ). In other words, the measurement position is expressed as R _TMR (x ₂ , y, z ₂ ). Just as x1 and _x2 are independent of each other, so z1 and _z2 are independent of each other.

Exactly as in the example in FIG. 3, the position of the sample in the example of FIG. 4 is designated P. The magnetic field component is transferred in the following order: T _COIL (x1, y, z ₁ ) --> P --> R _TMR (x2, y, z ₂ ).

At the excitation position T _COIL (x ₁ , y, z1 ) and the measuring position R _TMR (x2, y, z ₂ ), the magnetic field strength at the measuring position R _TMR (x2, y, z ₂ ) can be expressed as Φ(χ1 , x ₂ , y, z1, z ₂ ). Φ(χ1, x ₂ , y, z1, z ₂ ) is a magnetic field function depending on the excitation position, which takes the excitation position T _COIL (x ₁ , y, z1) and the position R _TMR (x2, y, z ₂ ) measurement as input and outputs the magnetic field strength at the measurement position RTMR(x2, y, z2).

The drive position T _COIL (x ₁ , y, z1) may be a virtual position of the drive circuit 110 . The measurement position R _TMR (x ₂ , y, z ₂ ) may be a virtual position of the magnetic sensor 130. If the drive position T _COIL (x ₁ , y, z1) corresponds to the actual position of the drive circuit 110, and the position RTMR(x2, y, z2 ) measurement corresponds to the actual position of the magnetic sensor 130, Φ(x ₁ , x ₂ , y, z1, z ₂ ) corresponds to the measured value, which is the actual measurement result.

In the example shown in FIG. 4, the drive circuit 110 has a z=0 coordinate and scans in the y- and x-axis directions in the xy plane. The magnetic sensor 130 has a coordinate z=z ₀ and scans in the x- and y-axis directions in the xy plane. This gives Φ(x ₁ , x ₂ , y, z1=0, z ₂ =z ₀ ) as the measured value for each combination of x1, x ₂ and y. This measured value is used as a boundary condition for the magnetic field function depending on the excitation position, which is Φ(x ₁ , x ₂ , y, z1, z2).

Φ(x ₁ , x ₂ , y, z1, z ₂ ) is a harmonic function depending on x1, y and z1 corresponding to the excitation position T _COIL (x ₁ , y, z1) and a harmonic function depending on x ₂ , y and z ₂ corresponding to the position R _TMR (x ₂ , y, z ₂ ) of the measurement. Therefore, Φ(x ₁ , x ₂ , y, z1, z ₂ ) satisfies (4-1) and (4-2) given below as fundamental equations, which are the Laplace equations related to the multipath problem in static or quasi-static field.

[expression 31] / a ² a ² a ² \ (^ ⁺ w ⁺ ^r ^(XllX2 ' ^y ' ^Z1 ' ^{22) = 0} ...(4-1)

[expression 32] / a ² a ² a ² \ (q^ ⁺ ^ ⁺ ^) ^f(x ^ ^y ' ² - ^22)=o • · · (4-2)

When the z-coordinate of the sample position P is greater than the z-coordinate of the excitation circuit 110 and less than the z-coordinate of the magnetic sensor 130, the general solution of equation (4-1) and the general solution of equation (4-2) can each be expressed as either a term that increases exponentially in the z-direction, or a term that decreases exponentially in the z-direction. In particular, the general solution of Equation (4-1) and the general solution of Equation (4-2) can each be expressed as (4-3) and (4-4) below.

[expression 33]

SO OO ____________

Φ(χ ₁ ,χ ₂ ,γ,ζ ₁ ,ζ ₂ ) = j J aJj< _Xi ,k _y )e ^ik ^ ^Xy+ ^ ^{+ky Z} 4k _x± dk _y - OO -co • · *(4-3 )

[expression 34]

SO OO ____________

Φ(χ ₁ ,χ ₂ ,γ,ζ ₁ ,ζ ₂ ) = J ja ₂ (k _X2 ,k _y )e ^ik *^^^ - OO -OO • · · (4-4)

The combination of (4-3) and (4-4) can be expressed by the following equation (4-5). [expression 35] ζ _υ ζ ₂ ) с с с ._____________ ______________ = III a(b^ _Xi J _(y )e^^ ⁺ ^^ - OO - OO -OO • · · (4-5)

Applying the measured values at z ₁ =0 and z ₂ =z ₀ as boundary conditions to (4-5) gives (4-6) below.

- 12 045848

[expression 36] oo oo so ._____

F(x ₁₍ x ₂ ,y, O,z _o ) = /// ', ^{2 y 0} dk _Xi dk _X2 dk _y - OO - OO -co • · · (4-6)

The inverse Fourier transform of (4-6) gives equation (4-7) below. [expression 37] a(k _X1 .k _X2 ,k _y ) = Ф(k _X1 ,k _X2 ,k _y ,g _z = 0,z ₂ = z ₀ ) • · -(4-7)

Below is the Fourier transform of the measured value:

I[expression 38]

F[k _X1 ,k _X2 ,k _y ,g ₁ = 0,z ₂ - z ₀ )

Therefore, the magnetic field function depending on the excitation position is expressed by the following equation (4-8).

[expression 39]

Φ^,Χ^γ, Z^Zz)

CO CO OO .______________ _______________ = JJ ja(k _Xi ,k _X2 ,ky)e ^ikx i ^X1+ikx 2 ^X2+ik y ^y eJ ^{kxi +ku Z1} y ^{X2 +ku} - CO -00 -00

Z j k ² -]-/< ² __ = e ^{2 y} Ф(k _Xg ,k _X2 ,k _y ,g ₁ = 0,z ₂ = z ₀ ) • · -(4-8)

By applying x ₂ --> x1 (=x), y --> y and z ₂ --> z ₁ (=z) to the magnetic field function depending on the excitation position, the output is assumed to indicate the magnetic field strength, measured at (x, y, z) after creating a magnetic field component at (x, y, z). It is assumed that the stronger the magnetic characteristics, the higher the magnetic susceptibility, and it is assumed that the image representing a given magnetic field strength shows the distribution of magnetic susceptibility in a zone including the interior region of the sample. The imaging function for generating such an image is expressed by the following equation (4-9).

[expression 40] <p(x,y,z) = Um

42“*^^ —Λ ^Ζ 2^ ^Ζ 1 ~ ^Ζ co co co ______________ ._____________ = Lim ff ί a(k _x ,k _x ь}е ^1кх ^* _Х2 x2+1к _у у^ _{dk dk} χ ₂ ^χ _Ύ =χ III \ ^x i' ^x 2' yJ ^x i ^x 2 У —co —co — co • · -(4-9)

The imaging function in (4-9) is a function that takes the imaging target position as input and outputs the image intensity at the imaging target position. The image intensity corresponds to a value obtained as a magnetic field strength at the output of the excitation position dependent magnetic field function in response to input of the imaging target position to the excitation position dependent magnetic field function.

For example, the information processing circuit 150 of the magnetic susceptibility distribution imaging device 100 calculates a magnetic field function depending on the excitation position from the measurement result, which is the measured value, and equation (4-8). Then, the information processing circuit 150 calculates the imaging function based on the magnetic field function depending on the excitation position and (4-9). Then, the information processing circuit 150 generates, based on the imaging function, an image representing the magnetic susceptibility distribution. Specifically, the information processing circuit 150 generates an image consisting of the values output by the imaging function for each imaging target position in the form of an image representing the magnetic susceptibility distribution.

This allows the magnetic susceptibility distribution imaging device 100 to generate an image representing the magnetic susceptibility distribution with high accuracy using the above-described excitation position dependent magnetic field function and the imaging function.

Fig. 5 is a schematic diagram for explaining another example of a driving position and a sensing position according to the present embodiment. In the above example shown in FIG. 4, the magnetic sensor 130 and the excitation circuit 110 are located on opposite sides of the sample. In contrast, in the example in FIG. 5, the magnetic sensor 130 and the excitation circuit 110 are located on the same side of the sample. Other conditions in the example in FIG. 5 are the same as in the example in FIG. 4.

As in the example in FIG. 5, when the z-coordinate P is less than the z-coordinate of the drive circuit 110 and less than the z-coordinate of the magnetic sensor 130, the above equation (4-3) can be replaced by the following equation (5-1).

[expression 41] with with _____________

Φ(χ ₁ ,χ ₂ ,γ,ζ ₁ ,ζ ₂ ) = JJ h ^{1 +ku Zy} dk _Xi dk _y • · -(5-1)

Therefore, in this case, the magnetic field function depending on the excitation position is expressed by the following equation (5-2).

[expression 42]

F(ad,UA,g ₂ )

OO OO CO ------------ -----------= III a(k _Xi ,k _X2 ,k _y )e ^l ^' ^+lh ^^^ a( k _X1 ,k _X2 ,k _y ) = eH ^{kx2 +ku} Ф(k _X1 ,k _X2 ,k _y ,g ₁ = 0,z ₂ = z ₀ ) • · -(5-2)

Moreover, in this case, the imaging function can be expressed by the following equation (5-3).

[expression 43] φ(χ,γ,ζ) = ^Lim^ Ф(x ₁ ,x ₂ ,y,z ₁ ,g ₂ ) ζ ₂ ^ζ ₁₌ ζ = _χ Yt _=x JJJ fi^^ ^Z2 dk _Xt dk _x? dk _y z ₂ ->z,=z _ _m _ ₀₀ • · · ( 5 - 3)

Fig. 6 is a configuration diagram of a second example of a magnetic susceptibility distribution imaging apparatus according to the present embodiment. The device 200 for visualizing the distribution of magnetic susceptibility shown in FIG. 6 includes a plurality of drive circuits 210, a drive circuit support structure 220, a plurality of magnetic sensors 230, a magnetic sensor support structure 240, an information processing circuit 150, a display 160, and a sample table 170. The magnetic susceptibility distribution imaging device 200 generates an image representing the magnetic susceptibility distribution in a zone including the interior region of a sample placed on the sample table 170 .

The plurality of drive circuits 210 are represented by electrical circuits of the same type as the drive circuit 110 shown in FIG. 1. In the example in FIG. 6, instead of a single drive circuit 110, multiple drive circuits 210 are used. Multiple excitation circuits 210 produce the first component of the magnetic field sequentially, without movement. In other words, the plurality of drive circuits 210 produces the first magnetic field component one at a time or in each predetermined block. Here, just like the drive circuit 110, a plurality of drive circuits 210 may produce a first magnetic field component from each of the drive positions.

The drive circuit support structure 220 is a structure that serves as a fixed support for a plurality of drive circuits 210. In the example in FIG. 6, field loop drive 120 shown in FIG. 1 is optional since the plurality of drive circuits 210 do not move.

The plurality of magnetic sensors 230 are of the same type as the magnetic sensor 130 shown in FIG. 1. In the example in FIG. 6, instead of a single magnetic sensor 130, a plurality of magnetic sensors 230 are used. The plurality of magnetic sensors 230 can measure magnetic characteristics at measurement positions without moving. In other words, just like the magnetic sensor 130, the plurality of magnetic sensors 230 can measure magnetic characteristics at each of the sensing positions.

The magnetic sensor support structure 240 is a structure that serves as a fixed support for a plurality of magnetic sensors 230. In the example of FIG. 6, the magnetic sensor drive 140 shown in FIG. 1 is optional since the plurality of magnetic sensors 230 do not move.

A plurality of drive circuits 210 and a plurality of magnetic sensors 230, and the like. device 200 for visualizing the distribution of magnetic susceptibility shown in FIG. 6 may perform the same function as the excitation circuit 110 and the magnetic sensor 130, etc. device 100 for visualizing the distribution of magnetic susceptibility shown in FIG. 1. Accordingly, exactly like the device 100 for visualizing the distribution of magnetic susceptibility, the device

- 14 045848

200 for visualizing the distribution of magnetic susceptibility can also measure sample-dependent magnetic characteristics while changing the relative position between the sample, the excitation position, and the sampling position.

This allows the magnetic susceptibility distribution imaging device 200 to obtain sufficient information about the magnetic susceptibility distribution in a zone including the interior region of the sample. In such a case, the magnetic susceptibility distribution imaging device 200 can calculate a magnetic field function depending on the excitation position based on the obtained sufficient information, and can generate an image representing the magnetic susceptibility distribution with high accuracy based on the calculated magnetic field function depending on excitation positions.

Example in Fig. 1 can be combined with the example in FIG. 2. For example, a moving drive circuit 110 and a plurality of magnetic sensors 230 may be employed, or a plurality of drive circuits 210 and a moving magnetic sensor 130 may be employed.

Fig. 7 is a schematic diagram for explaining a first example of a body scanner using the magnetic susceptibility distribution imaging device 200 shown in FIG. 6.

The body scanner 300 shown in FIG. 7 includes a plurality of drive circuits 210 and a plurality of magnetic sensors 230. For example, the body scanner 300 also includes an information processing circuit 150 and a display 160 shown in FIG. 6. In other words, the body scanner 300 may be a magnetic susceptibility distribution imaging device 200 or include a magnetic susceptibility distribution imaging device 200 . In such a case, the body scanner 300 generates an image representing the distribution of magnetic susceptibility.

Since the knives contain iron, the knives are characterized by high magnetic susceptibility. In contrast, the magnetic susceptibility of an aluminum case is low. Therefore, it is expected that the knives will appear in an image representing the distribution of magnetic susceptibility. In other words, the body scanner 300 can form an image of a knife that a person is holding inside an aluminum case by forming an image representing the distribution of magnetic susceptibility.

Fig. 7 is a schematic diagram. The number and dimensions of the plurality of drive circuits 210 and the number and dimensions of the plurality of magnetic sensors 230 may differ from those shown in the example of FIG. 7. More smaller drive circuits 210 can be arranged at higher densities, and more smaller magnetic sensors 230 can be arranged at higher densities. The same applies to other schematic representations.

As shown, for example, in FIG. 7, a plurality of drive circuits 210 produce a first magnetic field component, one row at a time, in the vertical or horizontal direction. The first component of the magnetic field causes the knife to create a second component of the magnetic field. The plurality of magnetic sensors 230 then measures the magnetic characteristics of the magnetic field containing the second magnetic field component. Here, a plurality of magnetic sensors 230 may measure magnetic characteristics at the sensing positions for each of the drive positions. The body scanner 300 can then generate an image of the knife from the measurement result with high accuracy.

Specifically, one vertical or horizontal row of a plurality of drive circuits 210 performs the same function as the electrical wire represented as the drive circuit 110 in FIG. 3. It is assumed that the fundamental equations given in (2-1) and (2-2), etc. are valid. Therefore, the magnetic field function depending on the excitation position and the imaging function given in (2-8) and (2-9) can be derived using the method described with reference to FIG. 3.

Therefore, the body scanner 300 can accurately image a knife based on the magnetic field function depending on the excitation position and the imaging function given in (2-8) and (2-9). In particular, the aluminum case does not transmit terahertz waves and microwaves. The body scanner 300 can accurately image the knife inside such an aluminum case.

The plurality of drive circuits 210 need not produce the first magnetic field component one row at a time in the vertical or horizontal direction, and may produce the first magnetic field component one at a time or in each predetermined block. In such cases, using the method described with reference to FIG. 3, it is possible to derive a magnetic field function depending on the excitation position and an imaging function different from those given in (2-8) and (2-9). The body scanner 300 can generate an image of a knife based on such a magnetic field function depending on the excitation position and such an imaging function.

Fig. 8 is a schematic representation of drive circuit 210. Drive circuit 210 shown in FIG. 8 corresponds to any of the plurality of drive circuits 210 depicted in FIG. 7. Specifically, the drive circuit 210 is a coil. This circuit creates the first component of the magnetic field. It should be noted that the drive circuit 210 is not limited to a coil and may be some other electrical circuit.

Fig. 9 is a schematic representation of a magnetic sensor 230. The magnetic sensor 230 shown in FIG. 9 corresponds to any of the plurality of magnetic sensors 230 shown in FIG. 7. In particular, the magnetic sensor 230 includes a TMR element or an MI element. This makes it possible to measure magnetic characteristics in a magnetic field containing a second magnetic field component.

Fig. 10 is a schematic diagram for explaining a specific structure of the magnetic sensor 230 shown in FIG. 9. As mentioned above, the magnetic sensor 230 includes, for example, a TMR element.

In a TMR element, an insulating film is sandwiched between magnetic films having a thickness of 10 nm to 100 nm. Specifically, the TMR element includes a plurality of thin films including a soft magnetic layer 231, a tunnel layer 232, and a PIN junction layer 233. The soft magnetic layer 231 is a magnetic film in which the magnetization direction changes in accordance with the magnetization direction of the external field. The PIN junction layer 233 is a magnetic film in which the magnetization direction does not change. The tunnel layer 232 is an insulating film.

The electrical resistance when the magnetization direction in the soft magnetic layer 231 and the PIN junction layer 233 are the same is different from the electrical resistance when the directions are different. This change in electrical resistance is used to measure the magnetic field component.

For example, magnetic sensor 230 uses the characteristics described above to sense and measure components of magnetic fields. It should be noted that the magnetic sensor 230 is not limited to the above-described example of a TMR element and may also include other elements such as a GMR element, a SQUID element, or an MI element.

Fig. 11 is a schematic diagram for explaining a second example of a body scanner using the magnetic susceptibility distribution imaging device 200 shown in FIG. 6. Body scanner 400 shown in FIG. 11 is substantially identical to the body scanner 300 shown in FIG. 7, but a plurality of drive circuits 210 and a plurality of magnetic sensors 230 of the body scanner 400 are enclosed in the structure. In particular, a plurality of drive circuits 210 and a plurality of magnetic sensors 230 are enclosed in two walls.

More specifically, a plurality of drive circuits 210 are included in the first of the two walls, and a plurality of magnetic sensors 230 are included in the second of the two walls. When a person is between two walls, a first magnetic field component is generated from each of the excitation positions by a plurality of excitation circuits 210, and magnetic characteristics are measured at the sensing positions by a plurality of magnetic sensors 230. This allows the body scanner 400 to form an image of a knife that the person is holding in an aluminum case. invisible to humans.

Fig. 12 is a schematic diagram for explaining a third example of a body scanner using the magnetic susceptibility distribution imaging device 200 shown in FIG. 6. Body scanner 500 shown in FIG. 12 is substantially identical to the body scanner 400 shown in FIG. 11, but the body scanner 500 includes a plurality of combination circuits 310 combining a plurality of drive circuits 210 and a plurality of magnetic sensors 230. Specifically, one combination circuit 310 includes one drive circuit 210 and one magnetic sensor 230. The plurality of combination circuits 310 are included in one wall.

In other words, a plurality of magnetic sensors 230 and a plurality of drive circuits 210 are located on the same side of the person corresponding to the sample. Therefore, it is possible to apply, for example, the magnetic field function depending on the excitation position and the imaging function given in (3-2) and (3-3). The body scanner 500 can then generate an image of the knife with high accuracy.

If one vertical or horizontal row of the plurality of combination circuits 310 produces the first magnetic field component, then rows other than that row can measure the magnetic characteristics. This protects the combination circuit 310 from sensing too much magnetic field from the first magnetic field component generated by the same circuit.

Fig. 13 is a schematic representation of a combination circuit 310. As shown in FIG. 13, the combination circuit 310 includes a drive circuit 210 and a magnetic sensor 230. Specifically, the drive circuit 210 is a coil. The magnetic sensor 230 includes a TMR element and is provided within the coil. This allows combination circuit 310 to create a first magnetic field component and measure magnetic characteristics in a magnetic field containing a second magnetic field component.

Fig. 14 is a schematic diagram explaining a fourth example of a body scanner using the magnetic susceptibility distribution imaging device 200 shown in FIG. 6. Body scanner 600 shown in FIG. 14 is substantially identical to the body scanner 500 shown in FIG. 12, but a plurality of combination circuits 310 of the body scanner 600 are enclosed in the floor.

Exactly as in the example in FIG. 12, a plurality of magnetic sensors 230 and a plurality of drive circuits 210 are located on the same side of the sample person. Therefore, it is possible to apply, for example, the magnetic field function depending on the excitation position and the imaging function given in (3-2) and (3-3). The body scanner 600 can then generate an image of the knife with high accuracy.

Fig. 15 is a schematic diagram for explaining a fifth example of a body scanner using the magnetic susceptibility distribution imaging device 200 shown in FIG. 6. Body scanner 700 shown in FIG. 15 is substantially identical to the body scanner 500 shown in FIG. 12, but a plurality of combination circuits 310 of the body scanner 700 are enclosed in a rack. This post can be, for example, a barrier post or boom of a barrier type.

In fig. 15, for example, a person passes by the counter. Here, a plurality of combination circuits 310 housed in the rack alternately generate a first magnetic field component. In such a case, a plurality of combination circuits 310 measure the magnetic characteristics. When measuring magnetic characteristics, a plurality of combination circuits 310 other than the combination circuit 310 that produces the first magnetic field component may measure the magnetic characteristics. The body scanner 700 repeats these processes as a person walks near the counter.

In particular, the unidirectional movement of a person passing near the post along a direction perpendicular to the post will cause the magnetic sensor 230 to perform a one-dimensional scan of the combination circuit 310 contained in the post relative to the person. In such a case, a two-dimensional scan (two-dimensional measurement result) is obtained by combining data obtained from a number of magnetic sensors 230 located in the same direction in the rack.

For example, as a person walks near the post, a plurality of combination circuits 310 may scan in a plane relative to the person. In other words, the body scanner 700 may generate a first magnetic field component from each of the in-plane excitation positions and may measure the magnetic characteristics of the magnetic field comprising the second magnetic field component at each of the in-plane sampling positions. The body scanner 700 can then form an image of, for example, a knife that a person is holding in an aluminum case from the measurement result.

For example, if the direction in which a person walks in FIG. 15, take the y-axis direction in FIG. 4, the y-coordinate of the drive circuit 210 relative to the passing person is the same as the y-coordinate of the magnetic sensor 230. In addition, the plurality of magnetic sensors 230 and the plurality of drive circuits 210 are located on the same side of the person corresponding to the sample. Therefore, it is possible to apply, for example, the magnetic field function depending on the excitation position and the imaging function given in (5-2) and (5-3).

Fig. 16 is a schematic diagram for explaining a sixth example of a body scanner using the magnetic susceptibility distribution imaging device 200 shown in FIG. 6. Body scanner 800 shown in FIG. 16 is substantially identical to the body scanner 700 shown in FIG. 15, but a plurality of combination circuits 310 of the body scanner 800 are housed in a plurality of racks. When a person walks between two of the posts, the body scanner 800 generates a first magnetic field component and measures the magnetic characteristics of the magnetic field containing the second magnetic field component.

The body scanner 800 may generate a first magnetic field component from the first of the two poles and measure the magnetic characteristics of the magnetic field containing the second magnetic field component at the second of the two poles. Here, a plurality of combination circuits 310 housed in the first frame may alternately produce a first magnetic field component. Here, just like the body scanner 300, the body scanner 800 can generate a first magnetic field component from each of the in-plane excitation positions and can measure the magnetic characteristics of the magnetic field containing the second magnetic field component at each of the in-plane sampling positions.

The body scanner 800 can then form an image of, for example, a knife that a person is holding in an aluminum case from the measurement result.

In the example in FIG. 16, each rack includes a plurality of combination circuits 310. However, the first rack of a pair of racks may include a plurality of drive circuits 210, and the second rack of a pair of racks may include a plurality of magnetic sensors 230.

For example, in FIG. 16 shows that a person walks between two posts along a direction parallel to the center line between the two posts. In this case, if the direction in which the person passes in FIG. 16, take the y-axis direction in FIG. 4, the y-coordinate of the drive circuit 210 relative to the passing person is the same as the y-coordinate of the magnetic sensor 230. In addition, the plurality of magnetic sensors 230 and the plurality of drive circuits 210 are located on opposite sides of the person corresponding to the sample. Therefore, it is possible to apply, for example, a magnetic field function depending on the excitation position and a shaping function

- 17 045848 images shown in (4-8) and (4-9).

The body scanner 800 may detect a knife or the like based on the generated image. When a knife or the like is detected, information indicating the location where the knife or the like was detected or the location of the person storing the knife or the like may be presented on an external terminal or the like.

Fig. 17 is a schematic diagram for explaining an example of presenting information on an external terminal by the body scanner 800 shown in FIG. 16. For example, the body scanner 800 generates a plurality of images from a measurement result obtained from a plurality of posts. In such a case, the body scanner 800 detects a knife or the like based on each image and a location corresponding to the knife or the like. The body scanner 800 then transmits information indicating a location corresponding to a knife or the like to the external terminal 1000.

The above-described operations can be performed, for example, by the information processing circuit 150 of the device 200 for visualizing the distribution of magnetic susceptibility. For example, the information processing circuit 150 determines whether the object corresponding to the pattern contains a detection target, and when it is determined that the detection target is contained in the object, outputs information indicating the location of the detection target or object to the external terminal 1000. The external terminal 1000 receives information indicating a location corresponding to a detection target such as a knife, and displays the information as shown in FIG. 17.

The above-described operations may be performed not only by the body scanner 800, but also by the body scanners 300, 400, 500, 600, 700, or any combination of such scanners and the like.

The above-described body scanners 300, 400, 500, 600, 700 and 800 correspond to the magnetic susceptibility distribution imaging device 200, but can be modified to correspond to the magnetic susceptibility distribution imaging device 100. In other words, the moving drive circuit 110 can be used in place of the plurality of drive circuits 210, and the moving magnetic sensor 130 can be used in place of the plurality of magnetic sensors 230.

Fig. 18 is a schematic diagram explaining an example of a security inspection system that uses the magnetic susceptibility distribution imaging device 100 shown in FIG. 1, or the device 200 for visualizing the distribution of magnetic susceptibility shown in FIG. 6.

For example, the security verification system 900 shown in FIG. 18 includes a device 100 or 200 for visualizing the distribution of magnetic susceptibility. In particular, the security screening system 900 may include a body scanner 400, shown in FIG. 11. The safety verification system 900 measures the quasi-static magnetic field, analytically solves the inverse problem, and reconstructs an image of the field. This allows the real-time security inspection system 900 to non-invasively visualize weapons, such as knives or firearms, hidden in briefcases, clothing, under body clothing or inside human bodies, and the like.

The safety testing system 900 further includes a gas phase chemical agent analyzer 910 and a pipe 920 to perform real-time analysis for gasoline or poison gas. For example, microscopic holes are formed in the surface of the wall in one or two dimensions, and surrounding air is drawn into numerous channels. The intake air is directed to the gas-phase chemical agent analyzer 910 through a pipe 920.

For example, the gas phase chemical agent analyzer 910 may include a gas chromatograph, a mass spectrometer, an ion mobility analyzer, or a combination of two or more of these, and may also be referred to as a gas classification detector. The gas phase chemical agent analyzer 910 detects the air supplied to the gas phase chemical agent analyzer 910 and analyzes the risk.

The gas phase chemical agent analyzer 910 disseminates information over the communications network about a person carrying poison gas in the same manner as information about a person carrying a weapon, such as a knife or firearm, as described above. The gas phase chemical agent analyzer 910 may send a report of such a dangerous person to the police or other crisis management team and may include such dangerous person information in commands on evacuation routes for nearby citizens.

It should be noted that FIG. 18 is merely a schematic representation, and the number and sizes of openings leading to gas phase chemical agent analyzer 910 via pipe 920 may differ from the example in FIG. 18. It is possible to form a larger number of denser, smaller holes.

The security verification system 900 may also be walk-through. The above-described security verification system 900 corresponds to a body scanner 400, but may be modified to correspond to a body scanner 300, 500, 600, 700, or 800. For example, gas phase chemical agent analyzer 910 and pipe 920 may be enclosed in only one wall, floor, or rack.

Fig. 19 is a flowchart representing the operation of the device

- 18 045848 (100, 200) for visualizing the distribution of magnetic susceptibility in accordance with an embodiment.

For example, the drive circuit (110, 210) produces a first magnetic field component from each of the drive positions specified outside the object as positions relative to the object (S101).

The magnetic sensor (130, 230) measures, at each of the measurement positions defined outside the object as positions relative to the object, magnetic characteristics in a magnetic field containing a second magnetic field component created by the first magnetic field component under the influence of the object (S102). In this case, the magnetic sensor (130, 230) measures the magnetic characteristics at the measurement positions for each of the excitation positions.

The information processing circuit (150) obtains the measurement result of the magnetic characteristics and generates an image representing the distribution of magnetic susceptibility in the area including the interior region of the object based on the measurement result (S103). For example, the information processing circuit (150) displays an image on the display (160) (S104). Alternatively, the information processing circuit 150 may print the image or transmit the image to another device.

When forming an image, the information processing circuit 150 calculates a magnetic field function depending on the excitation position using the measurement result as a boundary condition. The excitation position-dependent magnetic field function is a function that takes the virtual excitation position of the first magnetic field component and the virtual measurement position of the magnetic characteristics as input, and outputs the magnetic field strength at the virtual measurement position.

Then, the information processing circuit 150 calculates an image generation function. The imaging function takes the imaging target position as input and outputs the image intensity at the imaging target position, and is determined by the strength output from the magnetic field function dependent on the excitation position as a result of inputting the imaging target position, in the form of a virtual position excitation and virtual measurement position, into a function of the magnetic field depending on the excitation position. Then, the information processing circuit 150 generates an image based on the imaging function.

This allows the magnetic susceptibility distribution imaging device (100, 200) to generate an image representing, with high accuracy, the magnetic susceptibility distribution in a zone including the interior of an object, as measured by magnetic characteristics, based on various combinations of excitation positions and measurement positions.

For example, the information processing circuit 150 may calculate, as a magnetic field function depending on the excitation position, a solution to the Laplace equation satisfied by the magnetic field function depending on the excitation position, using the measurement result as a boundary condition. This allows the device (100, 200) for visualizing the distribution of magnetic susceptibility to correctly derive the magnetic field function depending on the excitation position based on the measurement result and the Laplace equation associated with a multipath problem in a static or quasi-static field.

For example, the information processing circuit 150 may calculate, as an imaging function, a limit value of the excitation position dependent magnetic field function by performing a limit taking operation of the excitation position dependent magnetic field function, which orients the virtual excitation position and the virtual sensing position, input into a magnetic field function dependent on the excitation position to the target imaging position. This allows the magnetic susceptibility distribution imaging device (100, 200) to correctly derive an imaging function based on the magnetic field function depending on the excitation position.

For example, the excitation positions may be defined in the first plane. Measuring positions can be specified in a second plane that is the same as or different from the first plane. In other words, the measurement positions may be specified in a first plane in which the excitation positions are specified, or in a second plane other than the first plane. The second plane may be parallel to the first plane.

This allows the device (100, 200) for visualizing the distribution of magnetic susceptibility to avoid increasing the size of the space required to accommodate the excitation circuit (110, 210) and the magnetic sensor (130, 230). A device (100, 200) for visualizing the distribution of magnetic susceptibility can also limit the complexity of the calculation process.

For example, the sensing positions may be located on a first side of the object, and the excitation positions may be located on a second, opposite side of the object. This allows the magnetic susceptibility distribution imaging device (100, 200) to measure magnetic characteristics at each of the measurement positions that are on the opposite side of the object from the excitation positions. Accordingly, the device (100, 200) for visualizing the distribution of magnetic susceptibility can suppress the influence of the first field component created by the excitation circuit (110, 210) when measuring magnetic characteristics at each of the measurement positions.

For example, the sensing positions and the excitation positions may be located on the same side of the object. This allows the magnetic susceptibility distribution imaging device (100, 200) to measure magnetic characteristics at each of the measurement positions that are on the same side of the object with respect to the excitation positions. Accordingly, the apparatus (100, 200) for visualizing the distribution of magnetic susceptibility may avoid increasing the size of the space required to accommodate the drive circuit (110, 210) and the magnetic sensor (130, 230).

For example, the drive circuit (110, 210) may generate a first magnetic field component from each of the drive positions by moving to each of the drive positions. The magnetic sensor (130, 230) can measure magnetic characteristics at each of the sensing positions by moving to each of the sensing positions.

This allows the magnetic susceptibility distribution imaging device (100, 200) to use one drive circuit (110, 210) for multiple drive positions and one magnetic sensor (130, 230) for multiple sensing positions. Accordingly, a device (100, 200) for visualizing the distribution of magnetic susceptibility can limit the increase in the cost of hardware.

For example, the drive circuit (110, 210) may include a plurality of drive circuits (110, 210) located at drive positions. The magnetic sensor (130, 230) may include a plurality of magnetic sensors (130, 230) located at sensing positions.

This allows the magnetic susceptibility distribution imaging device (100, 200) to generate a magnetic field component from each of the excitation positions and measure the magnetic characteristics at each of the sampling positions without moving the excitation circuit (110, 210) or the magnetic sensor (130, 230). Accordingly, the magnetic susceptibility distribution imaging apparatus 100, 200 can quickly obtain a measurement result corresponding to a plurality of drive positions and a plurality of sensing positions.

It should be noted that the plurality of drive circuits (110, 210) are not limited to a one-to-one correspondence with a plurality of drive positions; two or more plurality of drive circuits (110, 210) may correspond to a single drive position (zone). Likewise, the plurality of magnetic sensors (130, 230) are not limited to one-to-one correspondence with a plurality of sensing positions; two or more plurality of magnetic sensors (130, 230) may correspond to a single sensing position (zone).

For example, a plurality of drive circuits (110, 210) may be located in the first plane. A plurality of magnetic sensors (130, 230) may be located in a second plane that is the same as or different from the first plane. In other words, a plurality of magnetic sensors (130, 230) may be located in a first plane in which a plurality of drive circuits (110, 210) are located, or in a second plane different from the first plane. The second plane may be parallel to the first plane.

This allows the magnetic susceptibility distribution imaging device (100, 200) to quickly obtain a measurement result corresponding to excitation positions in the first plane and measurement positions in the second plane.

For example, a plurality of drive circuits (110, 210) may be located on the first line. A plurality of magnetic sensors (130, 230) may be located on a second line that is different from the first line. In other words, a plurality of magnetic sensors (130, 230) may be located on a first line on which a plurality of drive circuits (110, 210) are located, or on a second line different from the first line. The second line can be parallel to the first line.

This allows the device (100, 200) for visualizing the distribution of magnetic susceptibility to reduce the space in which the excitation circuits (110, 210) are located and the space in which the magnetic sensors (130, 230) are located.

For example, the object may be moving. The drive circuit (110, 210) can generate a first magnetic field component from each of the drive positions specified relative to an object that is moving by generating the first magnetic field component from a predetermined position at different times. The magnetic sensor (130, 230) can measure magnetic characteristics at each of the measurement positions specified relative to an object that is moving by measuring magnetic characteristics at a predetermined position at different times.

This allows the magnetic susceptibility distribution imaging device (100, 200) to generate a magnetic field component from each of the excitation positions and measure the magnetic characteristics at each of the sampling positions without providing multiple excitation circuits (110, 210) or multiple magnetic sensors (130, 230). and without moving the contour (110, 210)

- 20 045848 excitation or magnetic sensor (130, 230).

For example, the drive circuit (110, 210) may be contained within the first wall. The magnetic sensor (130, 230) may be housed in a second wall that is the same as or different from the first wall. In other words, the magnetic sensor (130, 230) may be enclosed in a first wall in which the drive circuit (110, 210) is enclosed, or in a second wall other than the first wall. The first wall and the second wall may be opposite walls. In addition, for example, the drive circuit (110, 210) and the magnetic sensor (130, 230) may be embedded in the floor.

For example, the drive circuit (110, 210) may be contained within the first post. The magnetic sensor (130, 230) may be housed in a second post that is the same as or different from the first post. In other words, the magnetic sensor (130, 230) may be housed in a first post that encloses the drive circuit (110, 210), or in a second post different from the first post.

The above configurations make it possible to make the excitation circuit (110, 210) and the magnetic sensor (130, 230) invisible on the ground. This allows the magnetic susceptibility distribution imaging device (100, 200) to generate an image representing the magnetic susceptibility distribution without being noticed by humans.

In the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position can be expressed as (y1, z1). The virtual measurement position can be expressed as (x, y ₂ , z ₂ ). The z-coordinate of the position of the excitation circuit (110, 210) may be set to 0. The z-coordinate of the position of the magnetic sensor (130, 230) may be set to z ₀ . When the measurement positions and excitation positions are on opposite sides of the object, the magnetic field function depending on the excitation position can be defined as follows.

[expression 44]

Ф^УгУг-^г)

SO OO OO = 111 a(k _x ^ _yi ^y ₂ )e ^ikxX+i ^ dk _x dk _yi dky ₂ , a(k _x ,k _U1 ,k _U1 ) = ^{+ ky2} <i>(k _x ,ky ₁ ,ky ₂ ,z ₁ = 0,z ₂ = z ₀ )

Here, the Fourier image of the measurement result is expressed as follows.

[expression 45]

F^ku^ku^ = 0,z ₂ = Y)

Here, k _x , k _y1 and k _y2 are the wave numbers corresponding to x, y1 and y ₂ . The imaging function can be defined as follows.

[expression 46]

z) = Φ(χ,γ ₁ ,γ ₂ ,ζ ₁ ,ζ ₂ ) =ζ

OO OO OO = Lim [ ί [ a(k _x L _y ,k _y )e ^ik * ^x+ik yi ^y i ⁺ⁱ ^

Y2^Y1 ⁼ Y III Y ^x> Yr ^g Yr; ^x У1 У2 z ₂ ^z ₁₌ z

This allows the magnetic susceptibility distribution imaging device (100, 200) to generate an image representing the magnetic susceptibility distribution with high accuracy using the excitation position dependent magnetic field function expressed by the above equation and the imaging function expressed by the above equation.

In the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position can be expressed as (y ₁ , z ₁ ). The virtual measurement position can be expressed as (x, y ₂ , z ₂ ). The z-coordinate of the position of the excitation circuit (110, 210) may be set to 0. The z-coordinate of the position of the magnetic sensor (130, 230) may be set to z0. When the sensing positions and excitation positions are on the same side of the object, the magnetic field function depending on the excitation position can be defined as follows.

[expression 47] a(k _x ,k _Y1 , k _Y2 )e^+^ _Y1 y^^ _Y2 Y2 _e ~ ^k y^~^x ² +kY2 ² z ₂ , - OO -OO -OO a(k _x ,k _U1 ,k _U2 ) = _e ^z °J ^kx2+ky2 f{k _x ,k _Ug ,k _U2 ,2 _z = 0,z ₂ = z ₀ )

Here, the Fourier image of the measurement result is expressed as follows.

[expression 48]

F^ku^ku^ = 0,z ₂ = z ₀ )

- 21 045848

Here, k _x , k _y1 and k _y2 are the wave numbers corresponding to x, y1 and y ₂ . The imaging function can be defined as follows.

[expression 49]

Ιφ(χ,γ,ζ) - ^Lnn ^(x^y^.Z;,)

Ζ ₂ ^ _Ζ1 =Ζ

CO CO OO ___________ = _y2 Yrn _y J f I a(k _x ,k _yi ,k _y2 )e ^ikxX ^^^

22^Zi=Z — „qq _—οο

This allows the magnetic susceptibility distribution imaging device (100, 200) to generate an image representing the magnetic susceptibility distribution with high accuracy using the excitation position dependent magnetic field function expressed by the above equation and the imaging function expressed by the above equation.

In the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position can be expressed as (x1, y, z1). The virtual measurement position can be expressed as (x ₂ , y, z ₂ ). The z-coordinate of the position of the excitation circuit (110, 210) may be set to 0. The z-coordinate of the position of the magnetic sensor (130, 230) may be set to z ₀ . When the measurement positions and excitation positions are on opposite sides of the object, the magnetic field function depending on the excitation position can be defined as follows.

[expression 50]

Ф(x ₁ ,x ₂ ,y, z ₁ ,z ₂ )

CO OO OO ____________ ____________ = III a(t _ry k _X2 ^ _y )e ^lk -M' ^+l ^ - CO - CO -co a(k _X1 ,k _X2 ,ku) = _e ^Zo X^ ^{2 +ku} Ф^ k _x± ,k _X2 ,k _y ,g ₁ = 0,z ₂ = z ₀ )

Here, the Fourier image of the measurement result is expressed as follows.

[expression 51] = 0,Z ₂ = Z ₀ )

Here, k _x , k _y1 and k _y2 are the wave numbers corresponding to x, y ₁ and y ₂ . The imaging function can be defined as follows.

[expression 52] |ip(x,y,z) = Um Φ^,χ^ y, z _lt z ₂ ~)

L2“Λ

Z ₂ ^Zy=Z

OO OO OO ____________ ____________ = _x Lim _=x ί ί ί a(k _Xi ,k _X2 ,k _y )e ^lkx i ^X1+lk ^ ^+к У ^Ζγ ^ ^{кх2 +к} У ^Z2 dk _Xi dk _X2 dk _y w* X

This allows the magnetic susceptibility distribution imaging device (100, 200) to generate an image representing the magnetic susceptibility distribution with high accuracy using the magnetic field function depending on the excitation position expressed by the above equation and the imaging function expressed by the above equation.

In the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position can be expressed as (x _b y, z1). The virtual measurement position can be expressed as (x ₂ , y, z ₂ ). The z-coordinate of the position of the excitation circuit (110, 210) may be set to 0. The z-coordinate of the position of the magnetic sensor (130, 230) may be set to z ₀ . When the measurement positions and excitation positions are on the same side of the object, the magnetic field function depending on the excitation position can be defined as follows.

[expression 53]

Ф(^1.^2-У-21,2 ₂ )

CO OO OO _____________ _____________ = 111 a(k _Xi ,k _X2 ,k _y )e ^ikx i ^x i ^+ik *2 ^X2+i ^ - CO -CO -OO a(k _X1 ,k _X2 ,k _y ) - _e ^z <'^ ^2+k y ^{k _xv k _X2 ,k _y ,z ₁ = 0,z ₂ - z ₀ )

Here, the Fourier image of the measurement result is expressed as follows.

[expression 54] = 0.¾ = z ₀ )

Here, k _x , k _y1 and k _y2 are the wave numbers corresponding to x, y1 and y ₂ . The imaging function can be defined as follows.

- 22 045848

[expression 55] |φ(χ, y, ζ) = _X2 Tt _=x Φ(χ _υ x ₂ , y, ζ _χ , zj

Z ₂ ~*Zy -ζ οο οο οο ___________ ___________ = Lim fffa(k _x ,k _x k _v }e ^ikx i ^X1+ikx 2 ^X2+ik y ^y e /J+V ²² dk _x dk _v

III\ ^{%2 X1 X2} _{—00 — 00 — 00}

This allows the magnetic susceptibility distribution imaging device (100, 200) to generate an image representing the magnetic susceptibility distribution with high accuracy using the excitation position dependent magnetic field function expressed by the above equation and the imaging function expressed by the above equation.

For example, based on the image, the information processing circuit 150 can determine whether the detection target object is contained in the object, and, when it is determined that the detection target object is contained in the object, outputs information indicating the location of the detection target object or object to the external terminal ( 1000). This allows the magnetic susceptibility distribution imaging device (100, 200) to notify the location of a particular detection target or the location of an object including a particular detection target.

Above, herein, an aspect of the magnetic susceptibility distribution imaging apparatus has been described by way of example of the embodiments, but aspects of the magnetic susceptibility distribution imaging apparatus are not limited to the embodiments. Various changes may be made to the embodiments as will be apparent to those skilled in the art, and elements in the embodiments may be freely combined. For example, a process performed by a particular element in an embodiment may be performed, alternatively, by another element. In addition, the execution order of processes can be changed, and processes can be executed in parallel.

The method for visualizing the distribution of magnetic susceptibility, including the steps performed by the elements included in the device for visualizing the distribution of magnetic susceptibility, can be performed by any device or system. For example, part or all of the method for visualizing a magnetic susceptibility distribution may be performed by a computer including, for example, a processor, memory, and input/output circuitry. In such cases, the magnetic susceptibility distribution visualization method may be executed by a program to assign a computer task to execute the magnetic susceptibility distribution visualization method executed by the computer.

The program can be recorded on a non-volatile computer-readable storage medium.

Each of the elements of the device for visualizing the distribution of magnetic susceptibility can be made in the form of specialized equipment, in the form of universal equipment that runs the above program or the like, or any combination of the above. For example, the general-purpose hardware may be in the form of a memory on which the program is stored, and a general-purpose processor that reads the program from the memory and executes the program. Here, the memory may be a semiconductor memory or a hard disk, and the general purpose processor may be a central processing unit (CPU) or the like.

Specialized hardware may be in the form of a memory and a dedicated processor or the like. For example, a dedicated processor may access memory to record measurement data and perform the method described above for visualizing the distribution of magnetic susceptibility.

Each of the elements of the device for visualizing the distribution of magnetic susceptibility can be an electrical circuit. The electrical circuits may together form a single electrical circuit and, alternatively, may form separate electrical circuits. These electrical circuits may correspond to specialized equipment or general-purpose equipment that runs, for example, the above-mentioned program.

An apparatus for visualizing the distribution of magnetic susceptibility can also be described as an imaging apparatus. The device for visualizing the magnetic susceptibility distribution may be a safety monitoring device, such as a body scanner, and may be included in the safety monitoring device. Although the above is an example of a body scanner, application examples are not limited to this example. A device for visualizing the distribution of magnetic susceptibility can be used for testing electrical circuits or testing reinforced structures. The device for visualizing the distribution of magnetic susceptibility can also be used in medical diagnostics, where the human body is examined using a contrast agent containing a magnetic material.

Although the example in the above description is a magnetic field, the ideas of the present invention

Claims (20)

The principles are applicable in any domain that satisfies Laplace’s equation, which relates to a multipath problem in a static or quasi-static field. A quasi-static field may be an essentially static field, such as an electromagnetic field with a frequency of 100 kHz or lower, which may be considered to have no wave properties. In particular, instead of a magnetic field, an electric field, a temperature field, or a pressure field can be used. Therefore, the above-described device for visualizing the distribution of magnetic susceptibility can be described as a device for visualizing the distribution of response to an external field. For example, an apparatus for visualizing an external field response distribution produces an image representing an external field response distribution, which is a distribution of external field responses. The above-described magnetic sensor may be a sensor that measures field strength. Instead of magnetic field strength, field strength can be used. The magnetic field function depending on the excitation position can also be expressed as a field function depending on the excitation position. In other words, the magnetic field in the above description can be replaced by simply a field, and the distribution of magnetic susceptibility can be replaced by the distribution of response to an external field. For example, the drive circuit produces a first field component from a plurality of drive positions. The first field component directs the second field component away from the object. The sensor measures the field strength, which includes the second field component, at each measurement position. The information processing circuit receives the result of the intensity measurement and generates an image representing the distribution of the response to the external field in the zone including the internal region of the object, based on the measurement result. In such cases, the information processing circuit calculates a field function depending on the excitation position using the measurement result as a boundary condition, and calculates an imaging function based on the field function depending on the excitation position. The information processing circuit then generates an image based on the imaging function. This allows the device for visualizing the distribution of response to an external field to form an image representing with high accuracy the distribution of response to an external field in a zone including the internal region of the object. Industrial applicability One aspect of the present invention is useful for magnetic susceptibility imaging devices that produce images showing the distribution of magnetic susceptibility, and is applicable to magnetic field diagnostic devices, electronic component inspection, seismic inspection of reinforced structures, medical diagnostics, and safety inspection systems. List of symbols: 100, 200 - device for visualizing the distribution of magnetic susceptibility (device for visualizing the distribution of response to an external field); 110, 210 - excitation circuit; 120 - drive of the excitation circuit; 130, 230 - magnetic sensor (sensor); 140 - magnetic sensor drive (sensor drive); 150 - information processing circuit; 160 - display; 170 - sample table; 220 - supporting structure of excitation circuits; 231 - soft layer; 232 - tunnel layer; 233 - layer with PIN junction (layer for fixing the magnetization direction); 240 - magnetic sensor support structure (sensor support structure); 300, 400, 500, 600, 700, 800 - body scanner; 310 - combined circuit; 900 - security verification system; 910 - gas-phase chemical agent analyzer; 920 - pipe; 1000 - external terminal. CLAIM 1. A device for visualizing the distribution of a response to an external field, configured to generate an image representing the distribution of a response to an external field, wherein the device for visualizing the distribution of a response to an external field contains an excitation circuit configured to induce a first field component from - 24 045848 each of the excitation positions specified outside the object in the form of positions relative to the object; a sensor configured to measure, at each of the measurement positions defined outside the object as positions relative to the object, the strength of a field comprising a second field component induced by the object under the influence of the first field component, to measure the field strength at the measurement positions for each of the excitation positions ; and an information processing circuit configured to obtain a field strength measurement result and generate an image representing the distribution of the response to an external field in a zone including an internal region of the object based on the measurement result, wherein the information processing circuit is configured to calculate a field function depending from the excitation position, configured to receive the virtual excitation position and the virtual measurement position as input data and output the field strength at the virtual measurement position, using the measurement result as a boundary condition; calculate an imaging function, configured to take as input an imaging target position, which is a position to be rendered in the image, and output an image intensity at the imaging target position, and configured to determine based on the intensity output from the function a drive position dependent field in response to inputting the imaging target position, in the form of a virtual drive position and a virtual measurement position, into a drive position dependent field function; and generate an image based on the imaging function. 2. A device for visualizing the distribution of the response to an external field according to claim 1, in which the information processing circuit is configured to calculate, as a field function depending on the excitation position, the solution to the Laplace equation, which is satisfied by the field function depending on the excitation position, using measurement result as a boundary condition. 3. A device for visualizing the distribution of a response to an external field according to claim 1 or 2, in which the information processing circuit is configured to calculate, as an imaging function, the limit value of the field function depending on the excitation position, by taking the limit value of the field function depending on the excitation position from the excitation position, which orients the virtual excitation position and the virtual sensing position input to the excitation position-dependent field function to the imaging target position. 4. A device for visualizing the distribution of a response to an external field according to claim 1 or 2, wherein the excitation positions are configured to be specified in a first plane, and the measurement positions are configured to be specified in a second plane that is the same as or different from the first plane. 5. A device for visualizing the distribution of response to an external field according to claim 1 or 2, in which the measurement positions are located on the first side of the object and the excitation positions are on the second, opposite side from the object. 6. A device for visualizing the distribution of response to an external field according to claim 1 or 2, in which the measurement positions and excitation positions are located on one side of the object. 7. A device for visualizing the distribution of a response to an external field according to claim 1 or 2, wherein the excitation circuit is configured to induce a first field component from each of the excitation positions by moving to each of the excitation positions, and the sensor is configured to measure the field strength at each of the metering positions by moving to each of the metering positions. 8. A device for visualizing the distribution of response to an external field according to claim 1 or 2, wherein the excitation circuit comprises a plurality of excitation circuits located at excitation positions, and the sensor contains a plurality of sensors located at measurement positions. 9. The device for visualizing the distribution of response to an external field according to claim 8, in which the plurality of excitation circuits are located in the first plane, and the plurality of sensors are located in the second plane, which is the same as or different from the first plane. 10. A device for visualizing the distribution of response to an external field according to claim 8, in which a plurality of excitation circuits are located on the first straight line, and a plurality of sensors are located on the second straight line, which coincides with or differs from the first straight line. 11. A device for visualizing the distribution of response to an external field according to claim 1 or 2, in which the object is configured to move, the excitation circuit is configured to induce the first field component from each of the excitation positions, configured to be specified relative to the object, configured to move, by inducing a first field component from a predetermined position at different times, and the sensor is configured to measure the field strength at each of the measurement positions, configured to be specified relative to the object, configured to move, by measuring the field strength at a predetermined position at different times. 12. A device for visualizing the distribution of response to an external field according to claim 1 or 2, in which the excitation circuit is enclosed in a first wall, and the sensor is enclosed in a second wall, which is the same as and different from the first wall. 13. A device for visualizing the distribution of response to an external field according to claim 1 or 2, in which the excitation circuit and the sensor are enclosed in the floor. 14. An external field response distribution imaging device as claimed in claim 1 or 2, wherein the excitation circuit is enclosed in a first post and the sensor is enclosed in a second post that is the same as or different from the first post. 15. A device for visualizing the distribution of response to an external field according to claim 5, in which, in the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position is expressed as (y1, z ₁ ), the virtual measurement position is expressed as (x, y ₂ , z ₂ ), z-coordinate of the excitation circuit position is set equal to 0 and z-coordinate of the sensor position is set equal to z ₀ , the field function depending on the excitation position is defined as: [expression 1] Ф(Х-У1,У2^1,2 ₂ ) OO OO OO ___________ ⁼ J / / ^a ( ^k *'kyi'kyz^ ^lkiX+l ^^^ ^{kx + kug Z2} dk _x dk _yi dk _y2 , - OO - OO -OO a^ku^ku^ = _e ² °'1^^Ф(k _x ,k _U1G k _{y2,2 1} = 0,z ₂ = z ₀ ) The Fourier image of the measurement result is expressed as: [expression 2] Ф(k _x ,k _y1 ,ky ₂ ,z ₁ = 0,z ₂ = z ₀ ) where kx, k _y i and k _y2 are the wave numbers corresponding to x, y1 and y ₂ , and the imaging function is defined as : [expression 3] |φ(χ, y, ζ) - _У2 Цпн _у Ф(х, УкУг, ζ ₁ , ζ ₂ ) z ₂ -»zl=z с с с _____________ ⁼ уж? / / / <<k _x .k _y ^ _U! )e «^^^ 22^=2 16. A device for visualizing the distribution of response to an external field according to claim 6, in which in the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position is expressed as (y1, z1), the virtual measurement position is expressed as ( x, y ₂ , z ₂ ), the z-coordinate of the excitation circuit position is set equal to 0 and the z-coordinate of the sensor position is set to z0, the field function depending on the excitation position is defined as: [expression 4] FSH-UiUg^^gg) dk _y2 , a(k _x ,k _U1 ,k _y2 ) = e ^g °G ^{x + ku2} F[k _x ,k _U1> k _y2>21 = 0,z ₂ = z ₀ ) The Fourier image of the measurement result is expressed as: [Expression 5] ^(k _x ,ky ₁ ,ky ₂ ,z ₁ = 0,z ₂ = z ₀ ) where kx, k _y1 and k _y2 are the wave numbers corresponding to x, y1 and y ₂ , and the imaging function is defined as: [expression 6] φ(χ,γ,ζ) = ^brm^FSx.uru^r^gg) Ζ ₂ ->Ζ1=Ζ OO CO OO _____________ = / / ί <k _y ,k _U1 ,k _U2 )e'^^^ 22^=2 17. A device for visualizing the distribution of response to an external field according to claim 5, in which - 26 045848 in the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position is expressed as (x1, y, z1), the virtual measurement position is expressed as (x ₂ , y, z ₂ ), z coordinate of the contour position excitation is set equal to 0 and the z-coordinate of the sensor position is set equal to z ₀ , the field function depending on the excitation position is defined as: [expression 7] ¢(4-4-7-4-¾) CO CO Cj ____________ ____________ = JJJ a(k _X1 ,k _X2 ,k _y )e ^1kx 1 ^X1+1k ^^ +* _y +i _y z ₂ , - CO -co -co a(k _X1 ,k _X2 ,ky ) = e ^z °^^ f(k _X1 ,k _X2 ,k _y ,g ₁ = 0,z ₂ = z ₀ ) The Fourier image of the measurement result is expressed as: [S expression] Kk^k^.ky^ = 0,z ₂ = z ₀ ) where k _x1 , k _x2 and k _y are the wave numbers corresponding to x1, x ₂ and y, and the imaging function is defined as: [expression 9] φ^χ,γ,ζ) _x it^ _x Ф(x ₁ , x ₂ , y ₁ g ₁ , g ₂ ) Ζζ^Ζ^Ζ OO CO OO ___________ ___________ = ^Ш1 ₌₁ iff a(k _x y _Xz ,k _y )e ^!kx i^^ z _z ^=z 18. A device for visualizing the distribution of response to an external field according to claim 6, in which, in the three-dimensional space of x-coordinates, y-coordinates and z-coordinates, the virtual excitation position is expressed as (x1, y, z1), the virtual measurement position is expressed as form (x ₂ , y, z ₂ ), the z-coordinate of the excitation circuit position is set equal to 0 and the z-coordinate of the sensor position is set equal to z0, the field function depending on the excitation position is defined as: [expression 10] ¢(4-4-44,¾) с с с ____________ ____________ = III a(k _x y _X2 ,k _y )e ^1kx '- ^x - ⁺¹ ^ ^{1 +ku 21} Y ^{2 +ku 22} dk _Xi dk _X2 dk _y , - OO -OO -OO «(^, % ₂ - ku) = e°^^Ф(k _X1 , k _X2 , k _y , _Z1 = 0, z ₂ = z ₀ ), The Fourier image of the measurement result is expressed as: [expression I] f(k _X1 ,k _X2 ,k _y ,z _z - 0, z ₂ - z ₀ ) where k _x1 , k _x2 and k _y are the wave numbers corresponding to x1, x ₂ and y, and the formation function images are defined as: [expression 12] f(4 y, ζ) = Φ(χ _υ x ₂ ,y, ζ _υ ζ ₂ ) CO CO 00 ___________ ___________ = _x ^ _x f II a(k _x y _x2 ,k _y y ^kx ^ ^+ikx 2 ^x ^^ 22--^1=2 -and -t" - 00 19. An external field response distribution imaging device as claimed in claim 1 or 2, wherein the information processing circuit is configured to determine whether the object contains a detection target based on the image, and when it is determined that the object includes the target detection object, configured to output information indicating the location of the detection target or object to an external terminal. 20. A method for visualizing the distribution of a response to an external field for generating an image representing the distribution of a response to an external field, wherein the method for visualizing the distribution of a response to an external field comprises the following steps: inducing, by means of the excitation circuit, a first field component from each of the excitation positions specified outside the object in the form of positions relative to the object; measuring with the sensor, at each of the measurement positions specified outside the object in the form of positions relative to the object, the field strength containing the second field component created by the object under the influence of the first field component, in order to measure the field strength at the measurement positions for each of the excitation positions; And -