Observation method and observation device

Patent metadata

Field	Value
Publication number	US-11041826-B2
Application number	US-201615775905-A
Country	US
Kind code	B2
Filing date	Nov 15, 2016
Priority date	Nov 16, 2015
Publication date	Jun 22, 2021
Grant date	Jun 22, 2021

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 a function {tilde over (m)}(k x ,k y ,z) obtained by performing two-dimensional Fourier transform on the magnetic field source m is expressed by series expansion shown in the following (Equation C),
wherein the magnetic field source m is calculated using (Equation C), and a n in (Equation C) satisfies the following (Equation D),

m
~

⁡

(

k
x

,

k
y

,
z

)

=

∑

n
=
0

N

⁢

a
n

⁢

z
n

(

Equation
⁢

⁢
C

)

h
0

⁢
ωμ
⁢

∑

n
=
0

N

⁢

(

-
α

+

i
⁢

⁢
ωσμ

)

-
n

-
1

⁢

Γ
⁡

(

n
+
1

)

⁢

a
n

=

f
⁢

⁢
α

-
g

(

Equation
⁢

⁢
D

)

where, z is a coordinate in a depth direction of the object, k x and k y are respectively wave numbers of x and y which are coordinates in two orthogonal directions in the plane perpendicular to the depth direction, σ is a conductivity of the object, μ is a magnetic permeability of the object, ω is an angular frequency of a frequency in the plurality of frequencies components, which are obtained by performing Fourier transform on the pulse current, or the currents of the plurality of frequencies, N is an integer, h 0 , α, and a n are coefficients, f and g are variables indicating a boundary condition on the surface of the object, and Γ(n+1) is a gamma function.

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. An observation device comprising:
an application unit that 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;
a detection unit that detects a second magnetic field generated by applying the first magnetic field to the object; and
a calculation unit that calculates a distribution of a magnetic field source m in the second magnetic field,
wherein a function {tilde over (m)}(k x ,k y ,z) obtained by performing two-dimensional Fourier transform on the magnetic fie

Assignees

• Univ Kobe Nat Univ Corp
• Integral Geometry Science Inc

Inventors

• Kimura Kenjiro
• Kimura Noriaki

Classifications

• G01R33/10 Primary

  Plotting field distribution {; Measuring field distribution} · 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

• G01R33/00

  Arrangements or instruments for measuring magnetic variables · CPC title

• G01R33/093

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

• G01N27/72 Primary

  by investigating magnetic variables · CPC title