Observation method and observation device

Patent metadata

Field	Value
Publication number	US-11422110-B2
Application number	US-202117158169-A
Country	US
Kind code	B2
Filing date	Jan 26, 2021
Priority date	Nov 16, 2015
Publication date	Aug 23, 2022
Grant date	Aug 23, 2022

Abstract

Provided is a measurement device including an application unit, a detection unit, and a calculation unit. The application unit applies a first magnetic field, which is generated by applying a pulse current to a coil or applying currents with a plurality of frequencies to the coil in order, to an object. The detection unit detects a second magnetic field which is generated by applying the first magnetic field to the object. The calculation unit calculates a distribution of a magnetic field source m in the second magnetic field. The calculation unit may further generate an imaging signal for displaying the calculated distribution of the magnetic field source m, as an image. The display unit displays the image indicating the distribution of the magnetic field source m by using the imaging signal.

First claim

The invention claimed is:

1. An observation method comprising:
an application step of applying a first magnetic field, which is generated by applying a pulse current to a coil or applying currents with a plurality of frequencies to the coil in order, to an object;
a detection step of detecting a second magnetic field generated by applying the first magnetic field to the object; and
a calculation step of calculating a distribution of a magnetic field source m in the second magnetic field,
wherein the magnetic field source m satisfies the following (Equation A),

1
σ

⁢

∇
σ

×

j
e

=

-

m
⁡

(

x
,
y
,
z

)

⁢

{

ωμ
⁢

⁢

H
0

⁡

(

t
,
z

)

}

(

Equation
⁢

⁢
A

)

where, σ is a conductivity of the object, ω is an angular frequency of a frequency in a plurality of frequency components, which are obtained by performing Fourier transform on the pulse current, or the currents of the plurality of frequencies, μ is a magnetic permeability of the object, H 0 is the first magnetic field, j e is a current density of an eddy current generated in a direction in which the first magnetic field is canceled, t is a time, z is a coordinate in a depth direction of the object, and x and y are respectively coordinates in two orthogonal directions in a plane perpendicular to the depth direction.

2. The observation method according to claim 1 , further comprising:
a step of generating an imaging signal for displaying the calculated distribution of the magnetic field source m, as an image; and
a step of displaying an image indicating the distribution of the magnetic field source m by using the imaging signal.

3. The observation method according to claim 1 ,
wherein the first magnetic field and the second magnetic field are quasi-steady magnetic fields.

4. The observation method according to claim 3 ,
wherein a frequency band of the pulse current or the currents with the plurality of frequencies is equal to or less than 1 GHz.

5. The observation method according to claim 1 ,
wherein the object is a non-magnetic body.

6. The observation method according to claim 1 ,
wherein the magnetic field source m satisfies the following (Equation J),
wherein H 0 (t,z)∝e iωt holds,
wherein a magnetic field H(t,x,y,z=0) on a surface of the object is measured in the detection step, and
wherein the distribution of the magnetic field source m is calculated using the magnetic field H(t,x,y,z=0) measured and (Equation J) in the calculation step,

σ
⁢
μ
⁢

∂

∂
t

⁢
H

-

Δ
⁢
H

=

-

m
⁡

(

x
,
y
,
z

)

⁢

{

ω
⁢
μ
⁢

H
0

⁡

(

t
,
z

)

}

.

(

Equation
⁢

⁢
J

)

7. An observation method comprising:
an application step of applying a first magnetic field, which is generated by applying a pulse current to a coil or applying currents with a plurality of frequencies to the coil in order, to an object;

Assignees

• Univ Kobe Nat Univ Corp
• Integral Geometry Science Inc

Inventors

• Kimura Kenjiro
• Kimura Noriaki

Classifications

• G01R33/022

  Measuring gradient · CPC title

• G01R27/02

  Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant (by measuring phase angle only G01R25/00) · CPC title

• G01N27/72 Primary

  by investigating magnetic variables · CPC title

• G01R33/093

  using multilayer structures, e.g. giant magnetoresistance sensors (thin magnetic films H01F10/00) · CPC title

• G01R33/00

  Arrangements or instruments for measuring magnetic variables · CPC title