CN112326665A - Defect detection system based on space step-by-step frequency shift illumination - Google Patents
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Abstract
The invention discloses a defect detection system based on space step-by-step frequency shift illumination, which comprises a light source, a microscope objective, a tube lens, an image detector, a control module and a data processing module, wherein the light source comprises a vertical illumination light source and an inclined illumination unit. Emergent light of the vertical illumination light source and each inclined illumination unit can irradiate on an observed sample to excite a scattered field, the scattered field is collected by the microscope objective and then is incident to the image detector through the shaping of the microscope objective, and the scattered field is converted into a far-field intensity graph by the data processing module. And the control module controls the lighting of each light source and the acquisition of the scattering field signals of the observed sample by the image detector under the illumination of each light source according to the time sequence. The data processing module reconstructs the spatial frequency spectrum information of the observed sample to finally realize the detection imaging of the complex defect characteristic outline information and the detail characteristic information of the surface of the observed sample under the conditions of transmission type illumination or reflection type illumination.
Description
Technical Field
The invention relates to a product surface defect detection device, and belongs to the field of surface defect detection.
Background
The defect detection of the product surface is one of important means for realizing product quality control, improving the production process and optimizing the product performance. The manual detection is a traditional mode for detecting the surface defects of the products, but with the development and progress of the society, the traditional detection mode cannot meet the requirements of detection speed, detection accuracy and the like. With the development of industrial automation, the defect detection technology based on machine vision is rapidly developed by virtue of the advantages of non-contact, no damage, safety, reliability, wide spectral response range, high production efficiency and the like. For example, patent document CN105973912A discloses a dermal surface defect detection device based on linear array light source illumination and linear array industrial camera detection; patent document CN104897693A proposes a glass surface defect enhanced detection apparatus, which realizes magnified imaging of surface defects of an observed sample by oblique illumination in a single direction, but is limited by the numerical aperture NA of an imaging receiving objective (usually, a low-power large-field low-NA microscope objective), and the spatial spectrum information of the sample received by single illumination imaging is limited, which may cause defect feature loss in steps in other directions. Patent document CN102023164A discloses a detection device for dark field illumination with low angle ring light source, which solves the defect feature missing problem of single direction illumination, but due to aliasing of frequency spectrum information, it is unable to provide all detail information of observed sample with large size span through frequency spectrum reconstruction, and has the problems of missing detection and error detection.
Patent documents with publication numbers CN105225202A, CN104181686A, and CN106199941A propose an FPM imaging method, which improves the space Bandwidth product sbp (space Bandwidth product) of the whole imaging system by a sample space spectrum reconstruction method, and further implements the amplification and reconstruction of sample space spectrum information. However, the methods proposed in the related patent documents are all transmission-type illumination, and are not applicable to the microscopic observation of the surface of a non-transparent sample. Meanwhile, when the LED lighting unit is far from the center, the divergence angle of incident light is large, and the accuracy of the sub-aperture spectrum information obtained by fourier transform may be reduced.
A defect detection apparatus that can achieve fast step-wise reflective illumination and can improve the spatial bandwidth product of an imaging system through accurate spectral reconstruction is not available at present.
Disclosure of Invention
The invention aims to provide a defect detection system based on space step-by-step frequency shift illumination, which is used for acquiring detailed characteristic information of complex defects on the surface of an observed sample through reconstruction of sub-aperture frequency spectrum information.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: the defect detection system based on the space step-by-step frequency shift illumination comprises a light source, a microscope objective, a tube lens, an image detector, a control module and a data processing module, wherein the light source comprises a vertical illumination light source and an inclined illumination unit; emergent light of the vertical illumination light source and each inclined illumination unit can be irradiated on an observed sample to excite a scattered field; the scattered field can be collected by the microscope objective, then is shaped by the tube lens and enters the image detector, and scattered field signals are collected by the image detector; the control module can control the image detector to collect the scattered field signal of the observed sample under the illumination condition of each light source according to the time sequence, convert the scattered field signal into an electrical signal and send the electrical signal to the data processing module, and can light the next light source after the scattered field signal under the illumination condition of one light source is collected; the control module can control the data processing module to convert the electrical signals from the image detector into far-field intensity graphs and acquire sub-aperture spectrum information of each far-field intensity graph to perform spectrum splicing reconstruction; the vertical illumination light source and the adjacent sub-aperture spectrum information corresponding to the far-field intensity diagram formed under the irradiation of each inclined illumination unit are mutually overlapped, so that the data processing module can obtain a wide-band space spectrum information convergence solution of the observed sample when carrying out space spectrum reconstruction according to a spectrum splicing reconstruction method, and a reconstructed image of the observed sample is obtained.
Furthermore, the vertical illumination light source, the inclined illumination unit, the microscope objective and the image detector are all positioned on the same side of the observed sample; or the vertical illumination light source and the inclined illumination unit are positioned on one side of the observed sample, and the microscope objective and the image detector are positioned on the other side of the observed sample.
Furthermore, the inclined lighting units are distributed in a concentric ring; alternatively, the inclined lighting units are fixed on a spherical curved surface and distributed in a circular ring shape at different heights.
Further, the emergent wavelengths of the inclined lighting units distributed on the same ring are the same.
Furthermore, the light from the vertical illumination light source is vertically irradiated on the observed sample after passing through the optical lens, the beam splitter and the microscope objective.
The invention further comprises a two-dimensional scanning micro-displacement platform, the sample platform is fixed on the two-dimensional scanning micro-displacement platform, and after the data processing module completes the image reconstruction of one imaging position of the observed sample, the control module can control the two-dimensional scanning micro-displacement platform to move the observed sample on the sample platform to the next imaging position.
Furthermore, the invention also comprises a display, and the display is connected with the data processing module.
Furthermore, the device also comprises a self-focusing module, and the control module can control the self-focusing module to perform real-time focusing imaging on the surface of the observed sample.
Further, the data processing module can splice the reconstructed images of the adjacent imaging positions of the surface of the observed sample.
Furthermore, the data processing module can intelligently identify and calibrate the defect characteristics of the obtained spliced image.
Compared with the prior art, the invention has the beneficial effects that: (1) by utilizing the detection system, the contour information of the microstructure on the surface of the observed sample can be given, and the detail information in the image can be further given. (2) The invention can give out all detail information of the observed sample with larger size span through spectrum reconstruction, thereby effectively avoiding the problems of missed detection and error detection. (3) When the method is used for detecting the defects, the space bandwidth product of an imaging system can be improved by using accurate frequency spectrum reconstruction through not only performing reflective illumination on a transparent or non-transparent sample, but also performing transmission illumination on the transparent sample.
Drawings
FIG. 1 is a schematic structural diagram of an embodiment of a defect detection system based on spatially stepped frequency-shift illumination according to the present invention.
FIG. 2a is a schematic view of the tilted lighting units of the present invention arranged in concentric rings; fig. 2b is a schematic diagram of a spectral stitching reconstruction when the tilted illumination units are distributed in concentric circles as shown in fig. 2 a.
Fig. 3 is a timing diagram illustrating the application of vertical illumination sources and three sets of circular oblique illumination units when the oblique illumination units are distributed in concentric circles as shown in fig. 2a, wherein T represents time.
FIG. 4a is an ideal microarchitecture of a simulation design (concentric ring pairs, line width 192nm, line-to-center spacing 960 nm); FIG. 4b is a reconstructed image of the observed sample obtained by spectral reconstruction according to the present invention with vertical illumination and 24 directional step-wise frequency-shift oblique illumination (from inside to outside, the oblique illumination units on the three sets of rings respectively have illumination oblique incident angles of 25 °, 40 ° and 65 °); FIG. 4c is a graph of the far field intensity of a sample observed with a prior art 360 annular low angle incidence illumination (oblique incidence angle set to 65); fig. 4d is a graph of the far field intensity of a sample observed with prior art single direction low angle incidence illumination (oblique incidence angle set at 65 °).
Fig. 5 shows three imaging scanning modes of the two-dimensional scanning micro-displacement table of the invention.
In FIG. 1, 101. control module; 102. a vertical illumination light source; 103. an optical lens; 104. a beam splitter; 105. a microscope objective; 106. an observed sample; 107. a tube mirror; 108. an image detector; 109. a fixing device; 110. a tilting lighting unit; 111. a sample stage; 112. two-dimensional scanning micro-displacement table; 113. a data processing module; 114. a display.
Detailed Description
The technical scheme of the invention is further explained by combining the drawings and the specific embodiments.
As shown in fig. 1, the defect detection system based on spatially stepped frequency-shift illumination of the present invention mainly includes a light source, a microscope objective 105, a tube mirror 107, an image detector 108, a control module 101, and a data processing module 113. Wherein the light sources include a vertical illumination light source 102 and an oblique illumination unit 110. The oblique illumination unit 110 may selectively use light sources such as an LED light source, an LD light source, and a fiber bundle output light source. Preferably, an optical collimating device may be equipped at the vertical illumination light source and the exit port of each oblique illumination unit, so as to project the exit light into the imaging field range of the optical microscope objective 105, thereby improving the directional collimation of the illumination light field. Preferably, the output light of each oblique illumination unit 110 can directly irradiate on the surface of the observed sample, or a light uniformizing element can be added at the output end of the light source, so that the surface of the observed sample is uniformly illuminated. To improve the imaging field of view of the whole system, the microscope objective 105 is preferably a low power objective, such as a 5X, 10X, 20X magnification microscope objective. The image detector 108 may be a CCD (charge coupled device), SCMOS (Scientific COMS, COMS: complementary metal oxide semiconductor), or the like.
The emergent light of the vertical illumination light source 102 and each oblique illumination unit 110 can be irradiated on the observed sample to excite a scattered field, wherein the emergent light of the vertical illumination light source 102 is perpendicularly irradiated on the observed sample, and each oblique illumination unit 110 is irradiated on the observed sample at a certain inclination angle. The scattered field excited from the observed sample can be collected by the microscope objective 105, then shaped by the tube lens 107 and incident to the image detector 108, and the image detector 108 collects the scattered field signal and converts the scattered field signal into an electrical signal to be sent to the data processing module 113. As one embodiment of the present invention, as shown in fig. 1, light from a vertical illumination light source 102 is vertically irradiated on a sample to be observed via an optical lens 103, a beam splitter 104, and a microscope objective 105.
The control module 101 can control the image detector 108 to collect the scattered field signal of the observed sample under the illumination of each light source according to time sequence; after the image detector 108 finishes the acquisition of the scattered field signal of the observed sample under the illumination condition of one light source, the control module 101 lights the next light source, thereby realizing the space step type frequency shift illumination mode of the invention. Specifically, after the image detector 108 finishes collecting the scattered field signal of the observed sample under the irradiation of the vertical illumination light source 102, the control module 101 controls the oblique illumination units 110 to be sequentially turned on at a set timing, and the control module 101 controls the image detector 108 to collect the scattered field signal of the observed sample under the irradiation of the oblique illumination units 110 in a time-sharing manner. Wherein the next tilted illumination unit is illuminated after the image detector 108 has completed the acquisition of the scattered field signal under the illumination condition of the previous tilted illumination unit. The image detector 108 converts the scattered field signals of the observed sample under the irradiation of the vertical illumination light source 102 and each inclined illumination unit 110 into electrical signals, and sends the electrical signals to the data processing module 113. The control module 101 controls the data processing module 113 to convert the electrical signals from the image detector 108 into a far-field intensity map. The far-field intensity map of the observed sample under the previous light source illumination condition may be stored before the next light source is illuminated, or may be stored simultaneously with or after the next light source is illuminated. The invention can not only perform reflective illumination imaging on a transparent or non-transparent sample, but also perform transmission illumination imaging on the transparent sample, and can improve the space bandwidth product of an imaging system by using accurate frequency spectrum reconstruction under two illumination imaging modes, thereby not only providing the outline information of the surface microstructure of the observed sample, but also further providing the detail information in the image.
In addition, the control module 101 can also control the data processing module 113 to acquire sub-aperture spectrum information of each far-field intensity map and perform spectrum splicing reconstruction. In the present invention, the spectrum information of adjacent sub-apertures corresponding to the far-field intensity pattern formed under the irradiation of the vertical illumination light source 102 and each of the oblique illumination units 110 are overlapped with each other, so that the data processing module 113 can obtain a wide-band space spectrum information convergence solution of the observed sample when performing space spectrum reconstruction according to the spectrum stitching reconstruction method, thereby obtaining a reconstructed image of the observed sample. After the far-field intensity images under the illumination conditions of the vertical illumination light source 102 and all the inclined illumination units are stored, the data processing module 113 respectively acquires sub-aperture spectrum information corresponding to each far-field intensity image formed under the illumination of each inclined illumination unit 110 by applying inverse Fourier transform, and reconstructs and restores the morphological characteristics of the surface of the observed sample according to a spectrum splicing reconstruction algorithm.
As shown in FIG. 1, as an embodiment of the present invention, the vertical illumination source 102, the tilted illumination unit 110, the microscope objective 105 and the image detector 108 are all located on the same side of the sample under observation, so that the imaging of the reflected illumination of the transparent or non-transparent sample can be realized. As another embodiment of the invention, the vertical illumination light source 102 and the inclined illumination unit 110 are positioned on one side of the observed sample, and the microscope objective 105 and the image detector 108 are positioned on the other side of the observed sample, so that transmission illumination imaging of the transparent sample can be realized.
In a preferred embodiment of the present invention, the inclined lighting units 110 are distributed in concentric rings, for example, they may be distributed in concentric circular rings as shown in fig. 2a, or they may be arranged in concentric polygonal rings (not shown) such as concentric regular hexagons, concentric octagons, etc. The oblique illumination units 110 are distributed in concentric rings, so that the control module 101 can light the oblique illumination units 110 layer by layer in the sequence from the inner ring to the outer ring or from the outer ring to the inner ring, and therefore, the time sequence control of the control module 101 on the illumination of each light source, the acquisition of scattered fields under the illumination of each light source and the time sequence control of the storage of a far field intensity map are better realized.
As another preferred embodiment of the present invention, the oblique illumination units 110 may not be distributed on the same plane, for example, they may be fixed on a spherical curved surface and distributed in circular ring shape at different heights (not shown in the figure), the normal of the emergent light field of each oblique illumination unit 110 is directed to the spherical center, and the spherical center coincides with the center of the imaging field of view of the microscope objective 105. As a preferred embodiment of the present invention, the emission wavelengths of the oblique illumination units distributed on the same ring are the same.
As shown in fig. 1, each of the oblique illumination units 110 may be mounted on a fixing device 109 as an embodiment of the present invention. The fixing device 109 may be provided with a plurality of concentric circular ring supports, each inclined lighting unit 110 is fixed in a different circular ring support, and the interval between adjacent circular rings may be equal or unequal. Preferably, the inclination angle of the circular ring-shaped support can be adjusted, so that the inclination angle of each inclined illumination unit 110 mounted on the support can be adjusted, the illumination intensity and uniformity of each inclined illumination unit 110 in the imaging field of the microscope objective 105 are improved, and the accuracy of the sub-aperture spectrum information acquired by the post-image processing is improved.
As a preferred embodiment, as shown in fig. 1, the present invention may further include a two-dimensional scanning micro-displacement stage 112, and the sample stage 111 is fixed on the two-dimensional scanning micro-displacement stage 112. The range of the two-dimensional scanning micro-displacement stage 112 can be selected according to the sample size. After the reconstruction of the image at one imaging position of the observed sample is completed, the control module 101 can control the two-dimensional scanning micro-displacement stage 112 to move the observed sample on the sample stage to the next imaging position, and at the same time, the two-dimensional coordinate information corresponding to the next imaging position can be calibrated. By using the two-dimensional scanning micro-displacement table 112, the invention can provide all detail information of the observed sample with larger size span through frequency spectrum reconstruction, thereby effectively avoiding the problems of missing detection and error detection.
As a preferred embodiment, as shown in fig. 1, the present invention further includes a display 114, and the display 114 is connected to the data processing module 113.
As a preferred embodiment, the present invention may further include a self-focusing module, and the control module 101 may control the self-focusing module to perform real-time focusing imaging on the surface of the observed sample, so as to quickly adjust the Z-direction position of the microscope objective and ensure that the focal plane of the microscope objective is located on the target layer.
In the present invention, the data processing module 113 can also stitch the reconstructed images of the adjacent imaging positions of the large-sized observed sample surface. As a preferred embodiment, when the large-size sample is observed, the data processing module 113 can also perform intelligent identification and calibration of defect characteristics on the obtained stitched image.
In the embodiment shown in fig. 2a, the tilted lighting units 110 of the present invention are distributed in three sets of concentric circular rings from inside to outside, corresponding to ring 1, ring 2 and ring 3 in sequence. The center of the imaging field of view of the microscope objective 105 is located at the center of the three sets of concentric circles. The arrangement of the three sets of concentric rings includes, but is not limited to, the following two: the first illumination unit and the second illumination unit are positioned on the same plane, and the emergent light direction of each inclined illumination unit 110 is vertically downward; and the exit directions of the oblique illumination units 110 in the three groups of concentric rings are all directed to the center of the imaging field of view of the microscope objective 105.
As shown in fig. 2b, after completing the storage of the far-field intensity image of the observed sample at one imaging position under the vertical illumination light source 102 and all the oblique illumination units in the three groups of rings, the data processing module 113 respectively obtains the sub-aperture spectrum information corresponding to each far-field intensity image formed under the illumination of each oblique illumination unit 110 by applying inverse fourier transform, and reconstructs and restores the morphological feature of the observed sample surface according to the spectrum stitching reconstruction algorithm. Then, the control module 101 controls the two-dimensional scanning micro-displacement stage 112 to move to the next imaging position of the observed sample.
Fig. 3 shows a timing diagram of the application of the vertical illumination sources and the tilted illumination units within each ring, when the tilted illumination units are distributed in three sets of concentric rings as shown in fig. 2 a. Sequentially corresponding to the time period t that the vertical lighting light source is lightened from left to right0Time period t during which each of the inclined illumination units in the ring 1 is sequentially illuminated1And a time period t during which each of the oblique illumination units in the ring 2 is sequentially turned on2And a time period t during which each of the oblique illumination units within the ring 3 is sequentially illuminated3. Thus, in order from first to last, the control module controls the vertical illumination source, the tilt within rings 1 to 3The illumination units are sequentially lit.
FIG. 4a shows an ideal double line-to-loop structure (line width 192nm, line-to-center spacing 960 nm). If the step-by-step frequency-shift illumination imaging mode is adopted, the oblique incidence angles of the oblique illumination units in the three groups of rings from outside to inside are respectively 65 degrees, 40 degrees and 25 degrees, the numerical aperture angle of the microscope objective is 0.25, the third group of rings from inside to outside comprises 24 oblique illumination units which are distributed at equal intervals, and the corresponding reconstruction effect is shown in fig. 4 b. As can be seen from comparison with fig. 4a, the reconstruction result shown in fig. 4b shows that, with the detection system of the present invention, in addition to the profile information (circle) of the microstructure on the surface of the observed sample, the detailed information (two-line-to-circle structure) in the image can be further provided. In contrast, the prior art does not achieve the technical effect of the present invention, for example, the imaging scheme of the patent document with publication number CN102023164A is adopted to apply 360 ° low-angle annular illumination to the sample, assuming that the oblique illumination angle is 65 degrees, the corresponding far-field imaging intensity diagram is shown in fig. 4c, and the detail features of the visible microstructure are missing; if the single-direction diagonal low-angle oblique illumination scheme disclosed in the patent document with publication number CN104897693A is adopted, only the intensity information in the corresponding direction can be given, and as shown in fig. 4d, not only the detail information inside the microstructure is missing, but also the morphological feature of the whole structure is missing.
Fig. 5 shows three scanning imaging modes of the two-dimensional scanning micro-displacement stage 112, the first scanning imaging mode is the zigzag scanning mode shown in fig. 5 a: after the system is locked, the control module 101 controls the displacement platform in the X direction to continuously move along the X direction according to the control timing sequence, and after the line scanning in the X direction is completed, controls the scanning displacement platform in the Y direction to move by a certain step length, and then controls the scanning displacement platform in the X direction to perform reverse continuous scanning imaging. This process is repeated until the observation of the entire observed sample is completed. The second scanning imaging method is the comb scanning method shown in fig. 5b, and compared with the Z scanning method shown in fig. 5a, after the line scanning is completed, the scanning displacement table in the X direction needs to be controlled to return to the starting end, and then the scanning displacement table is moved a distance along the Y direction to start the scanning of the next line. The third scanning imaging mode is a spiral scanning scheme shown in fig. 5c, after the edge searching of the observed sample is completed, the control module 101 controls the sample stage to move the center of the observed sample to the field of view of the imaging system, and then spiral scanning imaging is performed.
The preferred embodiments of the present invention have been described above in a non-limiting manner with reference to the accompanying drawings, but various modifications made within the scope of the claims of the present invention will also fall within the scope of the present invention. The electric scanning imaging mode utilizing the two-dimensional scanning micro-displacement platform can also be carried out by manual mechanical control; although the above-mentioned embodiment shows the illumination scheme of the inclined illumination units distributed in three groups of rings, other numbers of groups of rings may be used to provide illumination, such as two groups, four groups, etc.; although only the concentric circular ring-shaped inclined lighting unit distribution structure is shown in the embodiments, in practical applications, polygonal ring-shaped controllable inclined lighting unit arrays such as hexagon, octagon, etc. can also be used. In the simulation of the above embodiment, although the oblique incident angles of the three sets of concentric annular oblique illumination units are given, the actual application may be adjusted according to the requirement, for example, according to the overlapping ratio between the sub-aperture spectrums. Meanwhile, in the simulation of the above embodiment, although the number of the three sets of concentric annular oblique illumination units is given, in practical application, adjustment may be performed according to parameters such as the numerical aperture NA of the microscope objective, the size of the oblique incident angle, and the like.
Claims (10)
1. A defect detection system based on space step-by-step frequency shift illumination is characterized in that: the device comprises a light source, a microscope objective (105), a tube lens (107), an image detector (108), a control module (101) and a data processing module (113), wherein the light source comprises a vertical illumination light source (102) and an inclined illumination unit (110);
emergent light of the vertical illumination light source (102) and each inclined illumination unit (110) can be irradiated on an observed sample to excite a scattered field; the scattered field can be collected by a microscope objective (105), then is shaped by a tube lens (107) and enters an image detector (108), and scattered field signals are collected by the image detector (108);
the control module (101) can control the image detector (108) to collect the scattered field signal of the observed sample under the illumination condition of each light source according to time sequence, convert the scattered field signal into an electrical signal and send the electrical signal to the data processing module (113), and can light the next light source after the scattered field signal under the illumination condition of one light source is collected; the control module (101) can control the data processing module (113) to convert the electrical signals from the image detector (108) into far-field intensity maps and acquire sub-aperture spectrum information of each far-field intensity map for spectrum splicing reconstruction;
the vertical illumination light source (102) and adjacent sub-aperture spectrum information corresponding to a far-field intensity diagram formed under the irradiation of each inclined illumination unit (110) are mutually overlapped, so that when the data processing module (113) carries out spatial spectrum reconstruction according to a spectrum splicing reconstruction method, a wide-band spatial spectrum information convergence solution of an observed sample can be obtained, and a reconstructed image of the observed sample is obtained.
2. The defect detection system of claim 1, wherein: the vertical illumination light source (102), the inclined illumination unit (110), the microscope objective (105) and the image detector (108) are all positioned on the same side of the observed sample; or the vertical illumination light source (102) and the inclined illumination unit (110) are positioned on one side of the observed sample, and the microscope objective (105) and the image detector (108) are positioned on the other side of the observed sample.
3. The defect detection system of claim 1 or 2, wherein: each inclined lighting unit (110) is distributed in a concentric ring; alternatively, the inclined lighting units (110) are fixed on a spherical curved surface and distributed in a circular ring shape at different heights.
4. The defect detection system of claim 3, wherein: the exit wavelengths of the oblique illumination units distributed on the same ring are the same.
5. The defect detection system of claim 1, 2 or 4, wherein: light from a vertical illumination light source (102) is vertically irradiated on a sample to be observed through an optical lens (103), a beam splitter (104) and a microscope objective (105).
6. The defect detection system of claim 1, 2 or 4, wherein: the device is characterized by further comprising a two-dimensional scanning micro-displacement table (112), wherein the sample table (111) is fixed on the two-dimensional scanning micro-displacement table (112), and after the data processing module completes image reconstruction at one imaging position of an observed sample, the control module (101) can control the two-dimensional scanning micro-displacement table (112) to move the observed sample on the sample table to the next imaging position.
7. The defect detection system of claim 1, 2 or 4, wherein: the display (114) is further included, and the display (114) is connected with the data processing module (113).
8. The defect detection system of claim 1, 2 or 4, wherein: the device further comprises a self-focusing module, and the control module can control the self-focusing module to perform real-time focusing imaging on the surface of the observed sample.
9. The defect detection system of claim 1, 2 or 4, wherein: the data processing module (113) is capable of stitching reconstructed images of adjacent imaging locations of the surface of the observed sample.
10. The defect detection system of claim 9, wherein: the data processing module (113) can intelligently identify and calibrate defect characteristics of the obtained spliced image.
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