Optical element surface defects detection and quantitative evaluation standard based on dark-field imaging

2021 ◽  
Author(s):  
Yongying Yang ◽  
Weimin Lou ◽  
Pengfei Zhang ◽  
Fanyi Wang ◽  
Zichen Lu ◽  
...  
Keyword(s):  
Quantitative Evaluation ◽  
Surface Defects ◽  
Optical Element ◽  
Dark Field ◽  
Evaluation Standard ◽  
Dark Field Imaging ◽  
Field Imaging

scholarly journals A New Stitching Method for Dark-Field Surface Defects Inspection Based on Simplified Target-Tracking and Path Correction

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 448
Author(s):  
Chen ◽  
Li ◽  
Sui
Keyword(s):  
Target Tracking ◽  
Surface Defects ◽  
Imaging System ◽  
Dark Field ◽  
Dark Field Imaging ◽  
Fine Surface ◽  
Camera Perspective ◽  
Scanning Path ◽  
Field Imaging ◽  
Small Field Of View

A camera-based dark-field imaging system can effectively detect defects of microns on large optics by scanning and stitching sub-apertures with a small field of view. However, conventional stitching methods encounter problems of mismatches and location deviations, since few defects exist on the tested fine surface. In this paper, a highly efficient stitching method is proposed, based on a simplified target-tracking and adaptive scanning path correction. By increasing the number of sub-apertures and switching to camera perspective, the defects can be regarded as moving targets. A target-tracking procedure is firstly performed to obtain the marked targets. Then, the scanning path is corrected by minimizing the sum of deviations. The final stitching results are updated by re-using the target-tracking method. An experiment was carried out on an inspection of our specially designed testing sample. Subsequently, 118 defects were identified out of 120 truly existing defects, without stitching mismatches. The experiment results show that this method can help to reduce mismatches and location deviations of defects, and it was also effective in increasing the detectability for weak defects.

Influence of light polarization state on the imaging quality of dark-field imaging system

2021 ◽  
Author(s):  
Dan Chen ◽  
Yuqin Wang ◽  
Rongzhu Zhang
Keyword(s):  
Intensity Distribution ◽  
Surface Defects ◽  
Imaging System ◽  
Detection System ◽  
Polarization State ◽  
Polarized Light ◽  
Dark Field ◽  
Light Polarization ◽  
Dark Field Imaging ◽  
Field Imaging

Abstract Annular linear polarized light is used as the illumination source of the reflective dark-field detecting system in this paper. According to the theories of the Bidirectional Reflectance Distribution Function (BRDF) and multi-beam interference, the influence of the light polarization state on the intensity distribution of the scattering light is analyzed in detail. For surface defects, a simulation model of dark-field imaging is established based on the Finite-Difference Time-Domain method (FDTD). Both the near-field and the far-field scattering intensity distribution caused by surface defects are calculated under different illumination conditions. The incidence angle and polarization state of illumination light are optimized. Simulation and experimental results show that the image quality will be minimally affected by the interference effect while P-polarized light illuminates with the incident angle of 45°. The higher measurement accuracy of the dark-field imaging detection system can be obtained when the optimized illumination scheme is used.

Detection of a point defect in a silicon single crystal by high-resolution TEM

1995 ◽  
Vol 53 ◽  
pp. 466-467
Author(s):  
M. Awaji
Keyword(s):  
High Resolution ◽  
Single Crystal ◽  
Point Defect ◽  
Point Defects ◽  
Noise Level ◽  
Dark Field ◽  
Silicon Single Crystal ◽  
High Resolution Image ◽  
Dark Field Imaging ◽  
Field Imaging

It is necessary to improve the resolution, brightness and signal-to-noise ratio(s/n) for the detection and identification of point defects in crystals. In order to observe point defects, multi-beam dark-field imaging is one of the useful methods. Though this method can improve resolution and brightness compared with dark-field imaging by diffuse scattering, the problem of s/n still exists. In order to improve the exposure time due to the low intensity of the dark-field image and the low resolution, we discuss in this paper the bright-field high-resolution image and the corresponding subtracted image with reference to a changing noise level, and examine the possibility for in-situ observation, identification and detection of the movement of a point defect produced in the early stage of damage process by high energy electron bombardment.The high-resolution image contrast of a silicon single crystal in the [10] orientation containing a triple divacancy cluster is calculated using the Cowley-Moodie dynamical theory and for a changing gaussian noise level. This divacancy model was deduced from experimental results obtained by electron spin resonance. The calculation condition was for the lMeV Berkeley ARM operated at 800KeV.

scholarly journals Noninvasive, in vivo assessment of the cervical microcirculation using incident dark field imaging

2021 ◽  
Vol 135 ◽  
pp. 104145
Author(s):  
Yani P. Latul ◽  
Arnoud W. Kastelein ◽  
Patricia W.T. Beemster ◽  
Nienke E. van Trommel ◽  
Can Ince ◽  
...  
Keyword(s):  
Dark Field ◽  
Dark Field Imaging ◽  
Incident Dark Field Imaging ◽  
Field Imaging ◽  
In Vivo Assessment

scholarly journals Correlation of image quality parameters with tube voltage in X-ray dark-field chest radiography: a phantom study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Andreas P. Sauter ◽  
Jana Andrejewski ◽  
Manuela Frank ◽  
Konstantin Willer ◽  
Julia Herzen ◽  
...  
Keyword(s):  
Image Quality ◽  
Imaging Modality ◽  
Signal Strength ◽  
Dark Field ◽  
Tube Voltage ◽  
X Ray ◽  
Dose Area Product ◽  
Dark Field Imaging ◽  
Field Imaging

AbstractGrating-based X-ray dark-field imaging is a novel imaging modality with enormous technical progress during the last years. It enables the detection of microstructure impairment as in the healthy lung a strong dark-field signal is present due to the high number of air-tissue interfaces. Using the experience from setups for animal imaging, first studies with a human cadaver could be performed recently. Subsequently, the first dark-field scanner for in-vivo chest imaging of humans was developed. In the current study, the optimal tube voltage for dark-field radiography of the thorax in this setup was examined using an anthropomorphic chest phantom. Tube voltages of 50–125 kVp were used while maintaining a constant dose-area-product. The resulting dark-field and attenuation radiographs were evaluated in a reader study as well as objectively in terms of contrast-to-noise ratio and signal strength. We found that the optimum tube voltage for dark-field imaging is 70 kVp as here the most favorable combination of image quality, signal strength, and sharpness is present. At this voltage, a high image quality was perceived in the reader study also for attenuation radiographs, which should be sufficient for routine imaging. The results of this study are fundamental for upcoming patient studies with living humans.

3d Reconstruction of Sub-Nm Beam Profiles in STEM

2001 ◽  
Vol 7 (S2) ◽  
pp. 344-345
Author(s):  
G. Möbus ◽  
R.E. Dunin-Borkowski ◽  
C.J.D. Hethėrington ◽  
J.L. Hutchison
Keyword(s):  
Electron Beam ◽  
Chemical Analysis ◽  
Energy Loss ◽  
Intensity Distribution ◽  
Dark Field ◽  
Beam Forming ◽  
Dark Field Imaging ◽  
Annular Dark Field ◽  
Electron Energy Loss ◽  
Field Imaging

Introduction:Atomically resolved chemical analysis using techniques such as electron energy loss spectroscopy and annular dark field imaging relies on the ability to form a well-characterised sub-nm electron beam in a FEGTEM/STEM [1-2]. to understand EELS+EDX-signal formation upon propagation of a sub-nm beam through materials we first have to assess precisely the beam intensity distribution in vacuum and find conditions for the best obtainable resolution.Experimental Details:Modern TEM/STEM instruments combine features of both imaging and scanning technology. The beam forming capability approaches closely that for dedicated STEMs, while CCD recording devices allow us to measure the beam profile by direct imaging at magnifications up to 1.5 M. The recording of a “z-section” series through the 3D intensity distribution of the cross-over can therefore be realised by recording of a “condenser focal series”.

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