Correlation averaging of two-dimensional crystals: basic strategy and refinements

1986 ◽  
Vol 44 ◽  
pp. 136-139
Author(s):  
W. Baumeister ◽  
R. Rachel ◽  
R. Guckenberger ◽  
R. Hegerl
Keyword(s):  
Low Dose ◽  
Signal To Noise Ratio ◽  
Real Space ◽  
Fourier Domain ◽  
Two Dimensional ◽  
Signal To Noise ◽  
Unit Cells ◽  
Lateral Displacements ◽  
Established Technique ◽  
Crystalline Array

IntroductionCorrelation averaging (CAV) is meanwhile an established technique in image processing of two-dimensional crystals /1,2/. The basic idea is to detect the real positions of unit cells in a crystalline array by means of correlation functions and to average them by real space superposition of the aligned motifs. The signal-to-noise ratio improves in proportion to the number of motifs included in the average. Unlike filtering in the Fourier domain, CAV corrects for lateral displacements of the unit cells; thus it avoids the loss of resolution entailed by these distortions in the conventional approach. Here we report on some variants of the method, aimed at retrieving a maximum of information from images with very low signal-to-noise ratios (low dose microscopy of unstained or lightly stained specimens) while keeping the procedure economical.

scholarly journals Low-dose, phase-contrast mammography with high signal-to-noise ratio

2016 ◽  
Vol 7 (2) ◽  
pp. 381 ◽  
Author(s):  
Lukas B. Gromann ◽  
Dirk Bequé ◽  
Kai Scherer ◽  
Konstantin Willer ◽  
Lorenz Birnbacher ◽  
...  
Keyword(s):  
Phase Contrast ◽  
Low Dose ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Signal To Noise ◽  
Noise Ratio

Performance Data of a New 2048 X 2048 Pixel Slow-Scan CCD Camera For TEM

2000 ◽  
Vol 6 (S2) ◽  
pp. 732-733
Author(s):  
S.A. Hiller ◽  
B. Kabius ◽  
W. Probst ◽  
H. Tröster ◽  
M. Trendelenburg ◽  
...  
Keyword(s):  
Low Dose ◽  
Signal To Noise Ratio ◽  
Ccd Camera ◽  
High Sensitivity ◽  
Signal To Noise ◽  
Ideal Image ◽  
Main Disadvantage ◽  
Ccd Arrays ◽  
Holographic Reconstruction ◽  
The Ideal

Excellent linearity and high sensitivity have made SSCs the ideal image detector for almost every TEM application. Their ability to make high quality digital images available within fraction of seconds for further evaluation and processing in a PC, have made them a non-dispensable accessory for any modern TEM. However, despite their excellent characteristics, SSCs provide a restricted number of individual image points in respect to a negative, what is considered to be the main disadvantage of this detector. To compensate for this, CCDs with 2048x2048 pixel are available since some time. SSCs using these 2kx2k CCD arrays not only provide 4 times the pixel number but also offer a lot more options people have waiting for: e. g. highly resolved low-dose or ESI images with significantly improved signal to noise ratio, or higher resolved images for diffraction analysis and holographic reconstruction.

Signal-to-noise ratio enhancement of a Hadamard transform spectrometer using a two-dimensional slit-array

2017 ◽  
Vol 56 (25) ◽  
pp. 7188 ◽  
Author(s):  
Mingbo Chi ◽  
Yihui Wu ◽  
Fang Qian ◽  
Peng Hao ◽  
Wenchao Zhou ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Hadamard Transform ◽  
Two Dimensional ◽  
Signal To Noise ◽  
Noise Ratio

scholarly journals Three-Dimensional Microwave Holographic Imaging Employing Forward-Scattered Waves Only

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
Reza K. Amineh ◽  
Maryam Ravan ◽  
Justin McCombe ◽  
Natalia K. Nikolova
Keyword(s):  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Imaging Method ◽  
Two Dimensional ◽  
Signal To Noise ◽  
High Loss ◽  
Holographic Imaging ◽  
Multiple Receivers ◽  
Satisfactory Performance ◽  
Resolution Limits

We propose a three-dimensional microwave holographic imaging method based on the forward-scattered waves only. In the proposed method, one transmitter and multiple receivers perform together a two-dimensional scan on two planar apertures on opposite sides of the inspected domain. The ability to achieve three-dimensional imaging without back-scattered waves enables the imaging of high-loss objects, for example, tissues, where the back-scattered waves may not be available due to low signal-to-noise ratio or nonreciprocal measurement setup. The simulation and experimental results demonstrate the satisfactory performance of the proposed method in providing three-dimensional images. Resolution limits are derived and confirmed with simulation examples.

Dynamic characteristics in two-dimensional FitzHugh–Nagumo neural system driven by Lévy noise

2019 ◽  
Vol 33 (28) ◽  
pp. 1950345 ◽  
Author(s):  
Linjie Wang ◽  
Yongfeng Guo ◽  
Fang Wei ◽  
Jianguo Tan
Keyword(s):  
Steady State ◽  
Signal To Noise Ratio ◽  
Neural System ◽  
Lévy Noise ◽  
Stationary Probability ◽  
Two Dimensional ◽  
Signal To Noise ◽  
Neuron System ◽  
Runge Kutta Method ◽  
Levy Noise

In this paper, the steady state characteristics and stochastic resonance (SR) in two-dimensional FitzHugh–Nagumo (FHN) neuron system driven by Lévy noise are studied. The system is simulated by Janicki–Weron algorithm and fourth-order Runge–Kutta method, and the steady state characteristics of the system are analyzed by stationary probability density (SPD) functions. Then, the SR is determined by the classical measure of signal-to-noise ratio (SNR). Through numerical simulation, it is found that the Lévy noise can induce the transition of the system. In addition, the effects of different parameters on the SR are analyzed by SNR.

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