scholarly journals Signal Retrieval from Non-Sinusoidal Intensity Modulations in X-ray and Neutron Interferometry Using Piecewise-Defined Polynomial Function

2021 ◽  
Vol 7 (10) ◽  
pp. 209
Author(s):  
Simon Pinzek ◽  
Alex Gustschin ◽  
Tobias Neuwirth ◽  
Alexander Backs ◽  
Michael Schulz ◽  
...  
Keyword(s):  
Polynomial Function ◽  
Expectation Maximization Algorithm ◽  
Dark Field ◽  
Imaging Systems ◽  
Differential Phase Shift ◽  
Dark Field Imaging ◽  
Phase Stepping ◽  
Sinusoidal Functions ◽  
Field Imaging ◽  
Physical Signal

Grating-based phase-contrast and dark-field imaging systems create intensity modulations that are usually modeled with sinusoidal functions to extract transmission, differential-phase shift, and scatter information. Under certain system-related conditions, the modulations become non-sinusoidal and cause artifacts in conventional processing. To account for that, we introduce a piecewise-defined periodic polynomial function that resembles the physical signal formation process, modeling convolutions of binary periodic functions. Additionally, we extend the model with an iterative expectation-maximization algorithm that can account for imprecise grating positions during phase-stepping. We show that this approach can process a higher variety of simulated and experimentally acquired data, avoiding most artifacts.

scholarly journals Aberrated dark-field imaging systems

2018 ◽  
Vol 98 (5) ◽  
Author(s):  
Mario A. Beltran ◽  
David M. Paganin
Keyword(s):  
Dark Field ◽  
Imaging Systems ◽  
Dark Field Imaging ◽  
Field Imaging

Dreidimensional abbildende Elektronenmikroskope I. Prinzip der Geräte / Threedimensionally Imaging Electron Microscopes

1972 ◽  
Vol 27 (6) ◽  
pp. 919-929 ◽  
Author(s):  
W. Hoppe
Keyword(s):  
Dark Field ◽  
Imaging Systems ◽  
Atomic Resolution ◽  
Small Object ◽  
Fourier Space ◽  
Bright Field ◽  
Image Construction ◽  
Dark Field Imaging ◽  
Electron Microscopes ◽  
Field Imaging

Abstract Threedimensionally Imaging Electron Microscopes The principles of new electron optical imaging systems will be described which make possible the threedimensional image construction of a small object. Data of threedimensional Fourier space are collected by the registration of several images using primary beams with different tilting angles. The simplest device of such a type - a magnetic fly's eye system - will lead to spherical aberrrations larger than about 20 mm. It will be shown, that there is a good chance to correct “ring zone segment”-systems to reach atomic resolution with or without image-reconstruction-calculations. Not only microscopes with conventional bright field and dark field imaging but also transmission scanning microscopes can be constructed usind these principles.

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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