CN109297931B - Three-direction shearing speckle interference system and method based on spatial carrier - Google Patents

Three-direction shearing speckle interference system and method based on spatial carrier Download PDF

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CN109297931B
CN109297931B CN201811405017.XA CN201811405017A CN109297931B CN 109297931 B CN109297931 B CN 109297931B CN 201811405017 A CN201811405017 A CN 201811405017A CN 109297931 B CN109297931 B CN 109297931B
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CN109297931A (en
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闫佩正
王永红
孙方圆
钟诗民
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Hefei University of Technology
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    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
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Abstract

The embodiment of the invention discloses a three-direction shearing speckle interference system based on a space carrier, which comprises: the device comprises a laser, a first lens, three beam groups and an imaging device; the first lens is arranged between the laser and a measured object, a light beam emitted by the laser irradiates the measured object through the first lens, and reflected light of the measured object forms an image on the imaging device after passing through the three beam groups; each beam group in the three beam groups comprises a beam splitter, a beam combiner, a second lens and an aperture diaphragm, and the second lens and the aperture diaphragm are arranged on a light path between the beam splitter and the beam combiner. The embodiment of the invention divides the object to be measured into three light paths to be imaged on the image plane, and the three light paths are mutually in interference, so that three-direction synchronous shearing speckle detection is carried out on the object to be measured through a single camera.

Description

Three-direction shearing speckle interference system and method based on spatial carrier
Technical Field
The invention relates to the field of optics, in particular to a three-direction shearing speckle interference system and method based on spatial carrier waves.
Background
The shearing speckle interference technology is a full-field, non-contact and high-sensitivity optical measurement technology, can directly measure the derivative of the deformation of an object, eliminates the rigid displacement of the measured object in the measurement process, has the advantages of simple optical path device, good anti-seismic performance, low requirement on the measurement environment and the like, and is widely applied to the field of industrial nondestructive detection.
However, the shearing speckle interference technique is sensitive to deformation only in its shearing direction. The loading deformation of the detected object defect can be multidirectional, for example, a long-strip defect has obvious loading deformation in the direction perpendicular to the strip direction, but the loading deformation in the direction parallel to the strip direction is not obvious. If the defect is detected by using the traditional unidirectional shearing speckle interference system, only the defect of loading deformation in the shearing direction can be detected; if the defects in the object to be detected only generate loading deformation perpendicular to the shearing direction, the defects cannot be detected. In order to comprehensively detect various defects in a detected object, the traditional unidirectional shearing speckle interference technology can only be used for detecting for many times. However, the multi-detection mode cannot ensure the consistency of the deformation quantity of the detected object, and the difficulty is brought to the subsequent unified quantification treatment of various defects.
Disclosure of Invention
The embodiment of the invention provides a three-direction shearing speckle interference system and method based on spatial carrier waves, which can carry out three-direction synchronous shearing speckle detection on a detected object through a single camera.
The embodiment of the invention adopts the following technical scheme:
a spatial carrier based three-direction shearing speckle interferometry system comprising: the device comprises a laser, a first lens, three beam groups and an imaging device;
the first lens is arranged between the laser and a measured object, a light beam emitted by the laser irradiates the measured object through the first lens, and reflected light of the measured object forms an image on the imaging device after passing through the three beam groups;
each beam group in the three beam groups comprises a beam splitter, a beam combiner, a second lens and an aperture diaphragm, and the second lens and the aperture diaphragm are arranged on a light path between the beam splitter and the beam combiner.
A method for imaging using a spatial carrier based three-way shearing speckle interferometry system, the spatial carrier based three-way shearing speckle interferometry system comprising: the device comprises a laser, a first lens, three beam groups and an imaging device; the first lens is arranged between the laser and a measured object, a light beam emitted by the laser irradiates the measured object through the first lens, and reflected light of the measured object forms an image on the imaging device after passing through the three beam groups; each beam group in the three beam groups comprises a beam splitter, a beam combiner, a second lens and an aperture diaphragm, and the second lens and the aperture diaphragm are arranged on a light path between the beam splitter and the beam combiner;
the method comprises the following steps: rotationally adjusting the beam splitter and/or the beam combiner of each of the three sets of beam sets such that the imaging of each set of beam sets translates with the rotational adjustment to adjust a direction and an amount of shear between three images formed by the three sets of beam sets;
adjusting the mutual position of the aperture stops in each of the groups of beam sets to adjust the mutual spatial carrier size.
The three-direction shearing speckle interference system and method based on the spatial carrier, provided by the embodiment of the invention, divide a measured object into three light paths to be imaged on an image plane, and mutually interfere with each other, so that three-direction synchronous shearing speckle detection is carried out on the measured object through a single camera.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
Fig. 1 is a schematic diagram of a three-direction shearing speckle interferometry system based on spatial carrier according to an embodiment of the present invention.
Fig. 2 is a schematic diagram illustrating a position of an aperture stop according to an embodiment of the present invention.
Fig. 3 is a diagram illustrating a fourier transformed spectrum according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.
In the prior art, two lasers with different wavelengths are needed, the cost and the light path debugging complexity are increased, the size of a spatial carrier and the shearing quantity cannot be independently adjusted, generally, in order to realize frequency spectrum separation, the spatial carrier needs to be large, the shearing quantity is also large, and the measurement precision is influenced. According to the embodiment of the invention, a single camera is used, and phase diagrams in three different shearing directions can be calculated only by acquiring one image before and after deformation. And the shearing amount and the shearing direction are respectively independently adjustable. The embodiment of the invention divides a measured object into three light paths to be imaged on an image plane, and the three light paths are mutually related. Adjusting the shearing direction among the three images by adjusting the beam splitter or the beam combiner in each beam path; the size of the spatial carriers is adjusted by adjusting the position of the aperture stop in each beam path. In the interferogram, the frequency spectrum of mutual shearing interference of three beams is extracted, so that shearing speckle interference phase images in three directions are obtained.
As shown in fig. 1, an embodiment of the present invention provides a three-directional shearing speckle interferometry system based on spatial carrier, including: a laser 11, a first lens 12, three beam groups 13, and an imaging Device 14 (e.g., a CCD (Charge Coupled Device) target, a CMOS (Complementary Metal Oxide Semiconductor)); the first lens 12 is arranged between the laser 11 and the object to be measured 15, the light beam emitted by the laser 11 is irradiated on the object to be measured 15 through the first lens 12, and the reflected light of the object to be measured is imaged on the imaging device after passing through the three beam sets; each of the three beam sets 13 includes a beam splitter 131, a beam combiner 132, a second lens 133, and an aperture stop 134, and the second lens and the aperture stop are disposed on an optical path between the beam splitter 131 and the beam combiner 132.
The beam splitter 131 and the beam combiner 132 in each beam set 13 of the three beam sets can be adjusted. According to different application scenarios, any one of the beam splitters 131 and any one of the beam combiners 132 may be adjusted, or a plurality of beam splitters 131 and beam combiners 132 may be adjusted together.
According to the three-direction shearing speckle interference system based on the spatial carrier, the object to be detected is divided into three light paths to be imaged on the image plane, and the three light paths are mutually interfered, so that three-direction synchronous shearing speckle detection is performed on the object to be detected through a single camera.
In one embodiment, the beam splitter 131 and the beam combiner 132 in each of the beam sets 13 are rotationally adjustable such that the imaging of each of the beam sets 13 is translated with the rotational adjustment to adjust the direction and amount of shear between the three images formed by the three beam sets 13.
In one embodiment, the aperture stop 134 in each of the three beam sets 13 is adjustable such that a virtual image reflected by the three beam sets 13 is on the imaging device 13 to adjust the mutual spatial carrier size.
The embodiment of the invention divides a measured object into three light paths to be imaged on an image plane, and the three light paths are mutually related. Adjusting the shearing direction among the three images by adjusting the beam splitter or the beam combiner in each beam path; by adjusting the position of the aperture diaphragm in each light path and adjusting the size of the mutual spatial carrier, the frequency spectrum of the mutual shearing interference of the three light beams is extracted in the interference pattern, and the shearing speckle interference phase patterns in three directions can be obtained.
In one embodiment, the laser beam irradiates the object to be measured after being expanded, the light reflected from the object to be measured is divided into 3 optical paths by the three beam splitters 131, the 3 optical paths are imaged after passing through the lenses 133 and the aperture stops 134 on the respective optical paths, and the three optical paths after passing through the respective beam combiners 132 are imaged on the imaging device 14. By adjusting the rotation of the 3 beam splitters 131 and the 3 beam combiners 132, the three images in the 3 optical paths can be arbitrarily translated, and the translation amounts of the three images formed by the three beam groups 13 are (Δ x)j,Δyj)，j＝1,2,3；
The sizes and relative positions of the three aperture stops 134 are adjustable, and virtual images of the three aperture stops 134 reflected by the respective beam combiners 132 are on a plane. As shown in fig. 2, in the three groups of beam setsThe three aperture stops 134 are located at (ξ) positions, respectively1,η1),(ξ2,η2),(ξ3,η3)；
The light wave imaged by the object to be measured 15 is u (x, y) exp [ i phi (x, y) ], and then the images of the three light beams formed by the three beam groups 13 are represented as:
Figure GDA0002768360680000051
where j is 1,2,3, λ is the laser wavelength and d is the distance from the aperture stop to the CCD.
In one embodiment, according to interference theory, the light intensity on the imaging device 14 is:
Figure GDA0002768360680000052
the fourier transform of the light intensity image collected by the imaging device 14 is as follows:
Figure GDA0002768360680000053
a schematic diagram of the Fourier transformed spectrum is shown in FIG. 3, where FT () represents the Fourier transform, Uj＝FT[uj]；j＝1,2,3，
Figure GDA0002768360680000054
Represents a convolution; parameter(s)
Figure GDA0002768360680000055
Contains background information, which is located in the center of the spectrum; parameter(s)
Figure GDA0002768360680000056
And
Figure GDA0002768360680000057
contains the cutting graph information cut in the first direction and respectively centered in
Figure GDA0002768360680000058
And
Figure GDA0002768360680000059
parameter(s)
Figure GDA00027683606800000510
And
Figure GDA00027683606800000511
containing cropping pattern information cropped in the second direction and respectively centered at the center
Figure GDA0002768360680000061
And
Figure GDA0002768360680000062
parameter(s)
Figure GDA0002768360680000063
And
Figure GDA0002768360680000064
containing third-direction clipped clipping diagram information respectively centered at
Figure GDA0002768360680000065
And
Figure GDA0002768360680000066
in one embodiment, by selecting
Figure GDA0002768360680000067
Performing inverse Fourier transform to obtain
Figure GDA0002768360680000068
Can also obtain
Figure GDA0002768360680000069
And
Figure GDA00027683606800000610
the phase term can be calculated from the following relationship:
Figure GDA00027683606800000611
Figure GDA00027683606800000612
Figure GDA00027683606800000613
where IM and RE denote the imaginary and real parts of the complex number, respectively, psi1,2＝φ(x+Δx1,y+Δy1)-φ(x+Δx2,y+Δy2)、ψ2,3＝φ(x+Δx2,y+Δy2)-φ(x+Δx3,y+Δy3)、ψ3,1＝φ(x+Δx3,y+Δy3)-φ(x+Δx1,y+Δy1) Is the phase difference between three transverse shearing beams, the shearing direction and the shearing amount are as follows:
Figure GDA00027683606800000614
Figure GDA00027683606800000615
Figure GDA00027683606800000616
where norm () represents the modulus value of the vector;
recording a second image after the deformation, evaluating a phase diagram corresponding to the deformation by subtracting the phase distribution before and after the deformation, and calculating an optical phase difference caused by the deformation by the following equation assuming that the illumination direction is parallel to the imaging direction;
Figure GDA0002768360680000071
Figure GDA0002768360680000072
Figure GDA0002768360680000073
wherein w is the out-of-plane displacement, and the defect of the object to be measured can be detected by judging the abnormality in the distribution of the phase diagram.
The embodiment of the invention divides a measured object into three light paths to be imaged on an image plane, and the three light paths are mutually related. Adjusting the shearing direction and shearing amount among the three images by adjusting the beam splitter or the beam combiner in each beam path; the size of the spatial carriers is adjusted by adjusting the position of the aperture stop in each beam path. In the interferogram, the frequency spectrum of mutual shearing interference of three beams is extracted, so that shearing speckle interference phase images in three directions are obtained.
The embodiment of the invention provides a method for imaging by applying the three-direction shearing speckle interference system based on the space carrier, which comprises the following steps: rotationally adjusting the beam splitter 131 and/or the beam combiner 132 of each of the three sets of beam groups such that the image of each set of beam groups 13 is translated with the rotational adjustment to adjust a direction and amount of shear between the three images formed by the three sets of beam groups 13;
the mutual position of the aperture stops 134 in each of the groups of beam sets is adjusted to adjust the mutual spatial carrier size.
The beam splitter 131 and the beam combiner 132 in each beam set 13 of the three beam sets can be adjusted. According to different application scenarios, any one of the beam splitters 131 and any one of the beam combiners 132 may be adjusted, or a plurality of beam splitters 131 and beam combiners 132 may be adjusted together.
In one embodiment, the laser beam irradiates the object to be measured 15 after being expanded, the light reflected from the object to be measured is divided into 3 optical paths by the beam splitter 131, then the light passes through the lens 133 and the aperture stop 134 on each optical path and is imaged, and the three optical paths pass through each beam combiner 134 and are imaged on the CCD. By adjusting the rotation of the three beam splitters 131 and the three beam combiners 134, the three images formed by the three beam combiners can be translated arbitrarily, and the translation amounts of the three images formed by the three beam combiners are respectively (Δ x)j,Δyj)，j＝1,2,3；
The sizes and relative positions of the three aperture stops 134 are adjustable, the three aperture stops 134 respectively reflect virtual images through the respective beam combiners 134, and on one plane, as shown in fig. 2, the positions of the three aperture stops in the three groups of beam combiners are respectively (ξ)1,η1),(ξ2,η2),(ξ3,η3)；
The light wave imaged by the object to be measured 15 is u (x, y) exp [ i phi (x, y) ], and then the images of the three light beams formed by the three beam groups 13 are represented as:
Figure GDA0002768360680000081
where j is 1,2,3, λ is the laser wavelength and d is the distance of the aperture stop to the imaging device.
In one embodiment, the light intensity on the imaging device 14 is:
Figure GDA0002768360680000082
the fourier transform of the light intensity image collected by the imaging device 14 is as follows:
Figure GDA0002768360680000083
schematic diagram of Fourier transformed spectrumAs shown in fig. 3, where FT () represents the fourier transform, Uj＝FT[uj]；j＝1,2,3，
Figure GDA0002768360680000084
Represents a convolution; parameter(s)
Figure GDA0002768360680000085
Contains background information, which is located in the center of the spectrum; parameter(s)
Figure GDA0002768360680000086
And
Figure GDA0002768360680000087
contains the cutting graph information cut in the first direction and respectively centered in
Figure GDA0002768360680000091
And
Figure GDA0002768360680000092
parameter(s)
Figure GDA0002768360680000093
And
Figure GDA0002768360680000094
containing cropping pattern information cropped in the second direction and respectively centered at the center
Figure GDA0002768360680000095
And
Figure GDA0002768360680000096
parameter(s)
Figure GDA0002768360680000097
And
Figure GDA0002768360680000098
containing third-direction clipped clipping diagram information respectively centered at
Figure GDA0002768360680000099
And
Figure GDA00027683606800000910
in one embodiment, by selecting
Figure GDA00027683606800000911
Performing inverse Fourier transform to obtain
Figure GDA00027683606800000912
Can also obtain
Figure GDA00027683606800000913
And
Figure GDA00027683606800000914
the phase term can be calculated from the following relationship:
Figure GDA00027683606800000915
Figure GDA00027683606800000916
Figure GDA00027683606800000917
where IM and RE denote the imaginary and real parts of the complex number, respectively1,2＝φ(x+Δx1,y+Δy1)-φ(x+Δx2,y+Δy2)、ψ2,3＝φ(x+Δx2,y+Δy2)-φ(x+Δx3,y+Δy3)、ψ3,1＝φ(x+Δx3,y+Δy3)-φ(x+Δx1,y+Δy1) Is the phase difference between three transverse shearing beams, the shearing direction and the shearing amount are as follows:
Figure GDA00027683606800000918
Figure GDA00027683606800000919
Figure GDA00027683606800000920
where norm () represents the modulus value of the vector;
after the deformation, recording a second image, and evaluating a phase diagram corresponding to the deformation by subtracting the phase distribution before and after the deformation, wherein if the illumination direction is parallel to the imaging direction, the optical phase difference caused by the deformation can be calculated by the following equation;
Figure GDA0002768360680000101
Figure GDA0002768360680000102
Figure GDA0002768360680000103
wherein w is the out-of-plane displacement, and the defect of the object to be measured can be detected by judging the abnormality in the distribution of the phase diagram.
The embodiment of the invention divides a measured object into three light paths to be imaged on an image plane, and the three light paths are mutually related. Adjusting the shearing direction among the three images by adjusting the beam splitter or the beam combiner in each beam path; the size of the spatial carriers is adjusted by adjusting the position of the aperture stop in each beam path. In the interferogram, the frequency spectrum of mutual shearing interference of three beams is extracted, so that shearing speckle interference phase images in three directions are obtained.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains.

Claims (10)

1. A method for imaging by using a three-direction shearing speckle interference system based on a spatial carrier is characterized in that the three-direction shearing speckle interference system based on the spatial carrier comprises the following steps: the device comprises a laser, a first lens, three beam groups and an imaging device; the first lens is arranged between the laser and a measured object, a light beam emitted by the laser irradiates the measured object through the first lens, and reflected light of the measured object forms an image on the imaging device after passing through the three beam groups; each beam group in the three beam groups comprises a beam splitter, a beam combiner, a second lens and an aperture diaphragm, and the second lens and the aperture diaphragm are arranged on a light path between the beam splitter and the beam combiner;
the method comprises the following steps: rotationally adjusting the beam splitter and/or the beam combiner of each of the three sets of beam sets such that the imaging of each set of beam sets translates with the rotational adjustment to adjust a direction and an amount of shear between three images formed by the three sets of beam sets;
adjusting the mutual positions of the aperture stops in the three beam sets to adjust the mutual spatial carrier sizes.
2. The method of claim 1, wherein the three images formed by the three sets of beam sets are each translated by (Δ χ)j,Δyj)，j＝1,2,3；
The positions of the aperture diaphragms in the three beam groups are respectively (xi)1,η1),(ξ2,η2),(ξ3,η3)；
The light wave imaged by the measured object is u (x, y) exp [ i phi (x, y) ], and then the images of the three light beams formed by the three groups of beam groups are represented as:
Figure FDA0002768360670000011
where j is 1,2,3, λ is the laser wavelength and d is the distance of the aperture stop to the imaging device.
3. The method of claim 2, wherein the intensity of light on the imaging device is:
Figure FDA0002768360670000021
fourier transform is performed on the light intensity image acquired by the imaging device as follows:
Figure FDA0002768360670000022
where FT () represents the Fourier transform, Uj＝FT[uj]；j＝1,2,3，
Figure FDA0002768360670000023
Represents a convolution; parameter(s)
Figure FDA0002768360670000024
Contains background information, which is located in the center of the spectrum; parameter(s)
Figure FDA0002768360670000025
And
Figure FDA0002768360670000026
contains the cutting graph information cut in the first direction and respectively centered in
Figure FDA0002768360670000027
And
Figure FDA0002768360670000028
parameter(s)
Figure FDA0002768360670000029
And
Figure FDA00027683606700000210
containing cropping pattern information cropped in the second direction and respectively centered at the center
Figure FDA00027683606700000211
And
Figure FDA00027683606700000212
parameter(s)
Figure FDA00027683606700000213
And
Figure FDA00027683606700000214
containing third-direction clipped clipping diagram information respectively centered at
Figure FDA00027683606700000215
And
Figure FDA00027683606700000216
4. a method according to claim 3, characterised by selecting
Figure FDA00027683606700000217
Performing inverse Fourier transform to obtain
Figure FDA0002768360670000031
Can also obtain
Figure FDA0002768360670000032
And
Figure FDA0002768360670000033
the phase term can be calculated from the following relationship:
Figure FDA0002768360670000034
Figure FDA0002768360670000035
Figure FDA0002768360670000036
where IM and RE denote the imaginary and real parts of the complex number, respectively1,2＝φ(x+Δx1,y+Δy1)-φ(x+Δx2,y+Δy2)、ψ2,3＝φ(x+Δx2,y+Δy2)-φ(x+Δx3,y+Δy3)、ψ3,1＝φ(x+Δx3,y+Δy3)-φ(x+Δx1,y+Δy1) Is the phase difference between three transverse shearing beams, the shearing direction and the shearing amount are as follows:
Figure FDA0002768360670000037
Δs1,2＝norm[(Δx1-Δx2,Δy1-Δy2)]
Figure FDA0002768360670000038
Δs2,3＝norm[(Δx2-Δx3,Δy2-Δy3)]
Figure FDA0002768360670000039
Δs3,1＝norm[(Δx3-Δx1,Δy3-Δy1)]
where norm () represents the modulus value of the vector;
recording a second image after the deformation, evaluating a phase diagram corresponding to the deformation by subtracting the phase distribution before and after the deformation, and calculating an optical phase difference caused by the deformation by the following equation assuming that the illumination direction is parallel to the imaging direction;
Figure FDA00027683606700000310
Figure FDA00027683606700000311
Figure FDA00027683606700000312
wherein w is the out-of-plane displacement, and the defect of the object to be measured can be detected by judging the abnormality in the distribution of the phase diagram.
5. A three-direction shearing speckle interferometry system based on a spatial carrier, comprising: the device comprises a laser, a first lens, three beam groups and an imaging device;
the first lens is arranged between the laser and a measured object, a light beam emitted by the laser irradiates the measured object through the first lens, and reflected light of the measured object forms an image on the imaging device after passing through the three beam groups;
each beam group in the three beam groups comprises a beam splitter, a beam combiner, a second lens and an aperture diaphragm, and the second lens and the aperture diaphragm are arranged on a light path between the beam splitter and the beam combiner.
6. The system of claim 5, wherein the beam splitter and the beam combiner in each of the sets of beam groups are rotationally adjustable such that the imaging of each of the sets of beam groups is translated with the rotational adjustment to adjust a direction and amount of shear between the three images formed by the three sets of beam groups.
7. The system of claim 6, wherein the aperture stop in each of the three beam sets is adjustable such that a virtual image across the three beam sets is on the imaging device to adjust a mutual spatial carrier size.
8. The system of claim 7 wherein the three images formed by the three sets of beam sets are each translated by (Δ χ)j,Δyj)，j＝1,2,3；
The positions of the aperture diaphragms in the three beam groups are respectively (xi)1,η1),(ξ2,η2),(ξ3,η3)；
The light wave imaged by the measured object is u (x, y) exp [ i phi (x, y) ], and then the images of the three light beams formed by the three groups of beam groups are represented as:
Figure FDA0002768360670000041
where j is 1,2,3, λ is the laser wavelength and d is the distance from the aperture stop to the CCD.
9. The system of claim 8, wherein the intensity of light on the imaging device is:
Figure FDA0002768360670000051
fourier transform is performed on the light intensity image acquired by the imaging device as follows:
Figure FDA0002768360670000052
where FT () represents the Fourier transform, Uj＝FT[uj]；j＝1,2,3，
Figure FDA0002768360670000053
Represents a convolution; parameter(s)
Figure FDA0002768360670000054
Contains background information, which is located in the center of the spectrum; parameter(s)
Figure FDA0002768360670000055
And
Figure FDA0002768360670000056
contains the cutting graph information cut in the first direction and respectively centered in
Figure FDA0002768360670000057
And
Figure FDA0002768360670000058
parameter(s)
Figure FDA0002768360670000059
And
Figure FDA00027683606700000510
containing cropping pattern information cropped in the second direction and respectively centered at the center
Figure FDA00027683606700000511
And
Figure FDA00027683606700000512
parameter(s)
Figure FDA00027683606700000513
And
Figure FDA00027683606700000514
containing third-direction clipped clipping diagram information respectively centered at
Figure FDA00027683606700000515
And
Figure FDA00027683606700000516
10. the system of claim 9, wherein the selection is performed by selecting
Figure FDA0002768360670000061
Performing inverse Fourier transform to obtain
Figure FDA0002768360670000062
Can also obtain
Figure FDA0002768360670000063
And
Figure FDA0002768360670000064
the phase term can be calculated from the following relationship:
Figure FDA0002768360670000065
Figure FDA0002768360670000066
Figure FDA0002768360670000067
where IM and RE denote the imaginary and real parts of the complex number, respectively1,2＝φ(x+Δx1,y+Δy1)-φ(x+Δx2,y+Δy2)、ψ2,3＝φ(x+Δx2,y+Δy2)-φ(x+Δx3,y+Δy3)、ψ3,1＝φ(x+Δx3,y+Δy3)-φ(x+Δx1,y+Δy1) Is the phase difference between three transverse shearing beams, the shearing direction and the shearing amount are as follows:
Figure FDA0002768360670000068
Δs1,2＝norm[(Δx1-Δx2,Δy1-Δy2)]
Figure FDA0002768360670000069
Δs2,3＝norm[(Δx2-Δx3,Δy2-Δy3)]
Figure FDA00027683606700000610
Δs3,1＝norm[(Δx3-Δx1,Δy3-Δy1)]
where norm () represents the modulus value of the vector;
recording a second image after the deformation, evaluating a phase diagram corresponding to the deformation by subtracting the phase distribution before and after the deformation, and calculating an optical phase difference caused by the deformation by the following equation assuming that the illumination direction is parallel to the imaging direction;
Figure FDA0002768360670000071
Figure FDA0002768360670000072
Figure FDA0002768360670000073
wherein w is the out-of-plane displacement, and the defect of the object to be measured can be detected by judging the abnormality in the distribution of the phase diagram.
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