Method, device and program for processing diffraction images of a crystalline material

Patent metadata

Field	Value
Publication number	US-11526980-B2
Application number	US-201816771415-A
Country	US
Kind code	B2
Filing date	Dec 7, 2018
Priority date	Dec 11, 2017
Publication date	Dec 13, 2022
Grant date	Dec 13, 2022

Abstract

The invention relates to a method for processing images obtained by a diffraction detector, of a crystalline or polycrystalline material, in which a first image of the material is acquired in a state of reference as well as a second image of the material in a deformed state. The invention is characterised in that, in a calculator, during a first step (E6, E12), a current elastic deformation gradient tensor Fe is given a value determined by calculation, during a second step (E7), the current displacement field induced by the tensor Fe is calculated, during a third step (E8), third digital values of a deformed image {hacek over (g)}(x)=g(x+u(x)) corrected by the current displacement field are calculated, and during an iterative algorithm, iterations of the second and third steps (E12, E7, E8) are carried out on modified values of the tensor r Fe until a convergence criterion is met in relation to the correction to the current value of Fe.

First claim

The invention claimed is:

1. A method for processing images, obtained by a diffraction detector, of a material being crystalline or polycrystalline, in which the detector is used to measure:
a first diffraction image of the material when the material is in a reference state, giving first digital pixel values as a function of two pixel coordinates,
at least a second diffraction image of the material when the material is in a deformed state with respect to the reference state, the second diffraction image giving second digital pixel values as a function of the two pixel coordinates,
comprising in a calculator,
previously storing in a memory a displacement field, for displacing pixels of the first diffraction image to pixels of a deformed image, as a function of:
the two pixel coordinates,
predetermined coordinates of a center, corresponding to a normal projection, in an image plane of the detector, of a source point of a beam diffracted in the material, and
components of an elastic deformation gradient tensor,
during a first computing step, making the elastic deformation gradient tensor to take a determined value of the elastic deformation gradient tensor,
during a second computing step, computing the displacement field from the elastic deformation gradient tensor and from the two pixel coordinates of the first diffraction image,
during a third computing step, computing third digital pixel values of a deformed image by correcting the second diffraction image at the two pixel coordinates to which the displacement field has been added,
over an iterative algorithm, making iterations of the first computing step, of the second computing step and of the third computing step on modified determined tensor values, until a criterion of convergence on the determined value of the elastic deformation gradient tensor is fulfilled, to compute the displacement field.

2. The method as claimed in claim 1 , wherein the elastic deformation gradient tensor {circumflex over (F)} e is equal to

[

F
^

e

]

=

[

F
ˆ

1
e

F
ˆ

2
e

F
ˆ

3
e

F
ˆ

4
e

F
ˆ

5
e

F
ˆ

6
e

F
ˆ

7
e

F
ˆ

8
e

1

]

where {circumflex over (F)} 1 e , {circumflex over (F)} 2 e , {circumflex over (F)} 3 e , {circumflex over (F)} 4 e , {circumflex over (F)} 5 e , {circumflex over (F)} 6 e , {circumflex over (F)} 7 e , {circumflex over (F)} 8 e are the components of the elastic deformation gradient tensor {circumflex over (F)} e .

3. The method as claimed in claim 1 , wherein the displacement field u x ,u y , for displacing pixels of the first diffraction image to pixels of a deformed image, as a function of:
the two pixel coordinates x,y,
predetermined coordinates x*,y*, z* of the center, corresponding to the normal projection, in the image plane of the detector, of the source point of the beam diffracted in the material, and
components {circumflex over (F)} 1 e , {circumflex over (F)} 2 e , {circumflex over (F)} 3 e , {circumflex over (F)} 4 e , {circumflex over (F)} 5 e , {circumflex over (F)} 6 e , {circumflex over (F)} 7 e , {circumflex over (F)} 8 e of the elastic deformation gradient tensor {circumflex over (F)} e ,
is equal to

u
x

(

x
,

y

)

=

z
*

(

F
ˆ

1
e

(

x
-

x
*

)

+

F
ˆ

2
e

(

y
-

y
*

)

+

Assignees

• Electricite De France
• Centre Nat Rech Scient
• Ecole Normale Superieure Cachan

Inventors

• Latourte Félix
• Shi Qiwei
• Hild François
• Roux Stéphane

Classifications

• G01N2223/606

  texture · CPC title

• G06T7/001 Primary

  using an image reference approach · CPC title

• G01N23/203 Primary

  Measuring back scattering · CPC title

• G01N23/2251

  using incident electron beams, e.g. scanning electron microscopy [SEM] · CPC title

• G01N2223/0566

  analysing diffraction pattern · CPC title