Method of deconvoluting and restoring image observed in charged particle beam apparatus, image processing apparatus, and charged particle beam apparatus equipped with image processing apparatus
View Patent ↗Provided is a method of deconvoluting and restoring an image observed in a charged particle beam apparatus. The method includes receiving, by an image processing apparatus, an observed image acquired by a detector of the charged particle beam apparatus, calculating, by the image processing apparatus, a point spread function (PSF), deconvoluting and restoring, by the image processing apparatus, the observed image using the observed image and the PSF, calculating, by the image processing apparatus, an evaluation function of the parameter applied to a process of the deconvoluting, and adjusting, by the image processing apparatus, the parameter on the basis of a result of the evaluation function, and restoring the image after deconvoluting the observed image and the PSF again using an optimal parameter. Furthermore, a charged particle beam apparatus using the above-described method of deconvoluting and restoring the image is provided.
1. A method of restoring an image observed in a charged particle beam apparatus, the method comprising:
receiving, by an image processing apparatus, an observed image acquired by a detector of the charged particle beam apparatus;
calculating, by the image processing apparatus, a point spread function (PSF);
restoring, by the image processing apparatus, the observed image using the observed image and the PSF;
calculating, by the image processing apparatus, an evaluation function of a parameter applied to a process of the restoring; and
adjusting, by the image processing apparatus, the parameter on the basis of a result of the evaluation function to generate an optimal parameter, and restoring the observed image by deconvoluting the observed image and the PSF again using the optimal parameter,
wherein the evaluation function of the parameter is expressed as the following equation and the image processing apparatus determines the parameter when the result of the evaluation function of the parameter has a lowest value, as the optimal parameter:
ϕ
(
γ
)
=
❘
"\[LeftBracketingBar]"
1
N
-
1
1
M
-
1
∑
n
=
0
N
∑
m
=
0
M
ψ
m
,
n
(
r
;
γ
)
❘
"\[RightBracketingBar]"
wherein ϕ(γ) denotes the evaluation function of the parameter, γ denotes an optimization parameter, and ψ(r;γ) corresponds to a difference between an original image and an image restored by applying the parameter γ.
2. The method of claim 1 , wherein the parameter includes at least one of a Wiener filter parameter and a regularization parameter.
3. The method of claim 1 , wherein the image processing apparatus adjusts the parameter using an optimization algorithm.
4. The method of claim 1 , further comprising providing, by the image processing apparatus, sharpness and contrast-to-noise-ratio (CNR) information on the restored image.
5. The method of claim 1 , wherein the image processing apparatus restores the observed image by applying a constrained least square filter (CLSF) to the process of the deconvoluting.
6. The method of claim 5 , wherein the image processing apparatus restores the observed image by applying the CLSF to the process of the deconvoluting as shown in the following equation:
f
^
(
r
;
γ
)
=
ℱ
-
1
[
G
*
(
k
)
❘
"\[LeftBracketingBar]"
G
(
k
)
❘
"\[RightBracketingBar]"
2
+
γ
❘
"\[LeftBracketingBar]"
P
(
k
)
❘
"\[RightBracketingBar]"
2
]
H
(
k
)
,
P
(
k
)
=
ℱ
-
1
(
P
(
r
)
)
,
P
(
r
)
=
[
0
-
1
0
-
1
4
-
1
0
-
1
0
]
(G(k) denotes the Fourier transform of a PSF g(r), H(k) denotes the Fourier transform of an observed image h(r), and γ denotes an optimization parameter).
7. A charged particle beam apparatus for restoring an observed image of a sample by using the method of restoring an image observed in the charged particle beam apparatus of claim 1 .
8. The charged particle beam apparatus of claim 7 , wherein the charged particle beam apparatus uses an electron source or an ion source as a source, scans the sample with an electron beam or an ion beam, and allows a detector to detect a signal emitted from the sample.