Signal-to-noise enhancement in bright field images by incoherent superposition

1978 ◽  
Vol 36 (1) ◽  
pp. 232-233
Author(s):  
W. Kunath
Keyword(s):  
Signal To Noise Ratio ◽  
Random Network ◽  
Carbon Film ◽  
Cone Angle ◽  
Carbon Support ◽  
Signal To Noise ◽  
Bright Field ◽  
Contrast Transfer Function ◽  
Subsidiary Maxima ◽  
Field Imaging

Bright field imaging of heavy single atoms with hollow cone illumination results in images with only slightly reduced central contrast, compared to axial illumination, but strongly suppressed subsidiary maxima. This holds for certain values for the cone angle and defocus and is due to the triangle-shaped contrast transfer function. Computer-simulated micrographs of Hg atoms on a carbon support film show that the inherent structural noise is suppressed as well, resulting in twice as good a signal-to-noise ratio compared to axial illumination. The phase grating approximation is used.The computer-generated carbon film with an area of 48 Å by 48 Å is a random network of atoms, the sampling distance corresponding to 0.75 Å. It is fitted to give a noise-to-background ratio N = 5% in the Scherzer focus with the data λ = 3.7 • 10-2 A; Cs = 0.5 mm; Cc = 0.8 mm of our microscope.

Experiments in Bright-Field Imaging with Hollow-Cone Illumination

1981 ◽  
Vol 39 ◽  
pp. 226-227
Author(s):  
W. Kunath ◽  
K. Weiss ◽  
E. Zeitler
Keyword(s):  
Signal To Noise Ratio ◽  
Carbon Support ◽  
Electronic System ◽  
Optic Axis ◽  
Hollow Cone ◽  
Signal To Noise ◽  
Bright Field ◽  
Noise Ratio ◽  
Single Field ◽  
Field Imaging

Bright-field images taken with axial illumination show spurious high contrast patterns which obscure details smaller than 15 ° Hollow-cone illumination (HCI), however, reduces this disturbing granulation by statistical superposition and thus improves the signal-to-noise ratio. In this presentation we report on experiments aimed at selecting the proper amount of tilt and defocus for improvement of the signal-to-noise ratio by means of direct observation of the electron images on a TV monitor.Hollow-cone illumination is implemented in our microscope (single field condenser objective, Cs = .5 mm) by an electronic system which rotates the tilted beam about the optic axis. At low rates of revolution (one turn per second or so) a circular motion of the usual granulation in the image of a carbon support film can be observed on the TV monitor. The size of the granular structures and the radius of their orbits depend on both the conical tilt and defocus.

scholarly journals Erratum: “Signal-to-noise ratio in x-ray dark-field imaging using a grating interferometer” [J. Appl. Phys. 110, 053105 (2011)]

2011 ◽  
Vol 110 (10) ◽  
pp. 109902 ◽  
Author(s):  
Michael Chabior ◽  
Tilman Donath ◽  
Christian David ◽  
Manfred Schuster ◽  
Christian Schroer ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Dark Field ◽  
Signal To Noise ◽  
X Ray ◽  
Dark Field Imaging ◽  
Grating Interferometer ◽  
Noise Ratio ◽  
Field Imaging

scholarly journals Contrast Transfer Function-Based Exit-Wave Reconstruction and Denoising of Atomic-Resolution Transmission Electron Microscopy Images of Graphene and Cu Single Atom Substitutions by Deep Learning Framework

Nanomaterials ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1977
Author(s):  
Jongyeong Lee ◽  
Yeongdong Lee ◽  
Jaemin Kim ◽  
Zonghoon Lee
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Transfer Function ◽  
Signal To Noise Ratio ◽  
Atomic Resolution ◽  
Single Atom ◽  
Monolayer Graphene ◽  
Signal To Noise ◽  
Contrast Transfer Function ◽  
Transmission Electron

The exit wave is the state of a uniform plane incident electron wave exiting immediately after passing through a specimen and before the atomic-resolution transmission electron microscopy (ARTEM) image is modified by the aberration of the optical system and the incoherence effect of the electron. Although exit-wave reconstruction has been developed to prevent the misinterpretation of ARTEM images, there have been limitations in the use of conventional exit-wave reconstruction in ARTEM studies of the structure and dynamics of two-dimensional materials. In this study, we propose a framework that consists of the convolutional dual-decoder autoencoder to reconstruct the exit wave and denoise ARTEM images. We calculated the contrast transfer function (CTF) for real ARTEM and assigned the output of each decoder to the CTF as the amplitude and phase of the exit wave. We present exit-wave reconstruction experiments with ARTEM images of monolayer graphene and compare the findings with those of a simulated exit wave. Cu single atom substitution in monolayer graphene was, for the first time, directly identified through exit-wave reconstruction experiments. Our exit-wave reconstruction experiments show that the performance of the denoising task is improved when compared to the Wiener filter in terms of the signal-to-noise ratio, peak signal-to-noise ratio, and structural similarity index map metrics.

scholarly journals Signal-to-noise ratio in x ray dark-field imaging using a grating interferometer

2011 ◽  
Vol 110 (5) ◽  
pp. 053105 ◽  
Author(s):  
Michael Chabior ◽  
Tilman Donath ◽  
Christian David ◽  
Manfred Schuster ◽  
Christian Schroer ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Dark Field ◽  
Signal To Noise ◽  
X Ray ◽  
Dark Field Imaging ◽  
Grating Interferometer ◽  
Noise Ratio ◽  
Field Imaging

Improvement of TEM Bright-Field Images by Hollow-Cone Illumination

1977 ◽  
Vol 35 ◽  
pp. 200-201
Author(s):  
H. Rose ◽  
J. Fertig
Keyword(s):  
Phase Contrast ◽  
Scattering Amplitude ◽  
Cone Angle ◽  
Hollow Cone ◽  
Bright Field ◽  
Single Atoms ◽  
Severe Reduction ◽  
Imaging Mode ◽  
Field Imaging ◽  
Absorption Contrast

Axial coherent (parallel) illumination, commonly used for bright-field imaging, creates artifacts and strong structural noise. These parasitic structures are caused by an overlap of Fresnel fringes, which can be largely suppressed if hollow-cone (partially coherent) illumination is employed (1,2). However, it is commonly assumed that this imaging mode leads to a severe reduction in contrast. To obtain reliable information on the maximum contrast achievable, we have made extensive calculations of images of single atoms taking into account both phase contrast and scattering absorption contrast. The image contrast C = C(r, C3, Δf, U, θo, θ, Z) of an atom is a function of the image coordinate r, sperical aberration C3, defocus Δf, voltage U, aperture ΔO, cone angle Δ of the illumination, and the atomic number Z. At resolutions currently obtainable, the bright-field contrast of the objects can be described very accurately if the first- and second-order terms of the Born approximation of the scattering amplitude are considered.

Determination of the Best Emulsion for the Microscopy of Crystals

1981 ◽  
Vol 39 ◽  
pp. 32-33
Author(s):  
David A. Grano ◽  
Kenneth H. Downing
Keyword(s):  
Spatial Frequency ◽  
Information Transfer ◽  
Signal To Noise Ratio ◽  
Experimental Situation ◽  
Photographic Emulsion ◽  
Modulation Transfer ◽  
Signal To Noise ◽  
Frequency Space ◽  
Noise Ratio

The retrieval of high-resolution information from images of biological crystals depends, in part, on the use of the correct photographic emulsion. We have been investigating the information transfer properties of twelve emulsions with a view toward 1) characterizing the emulsions by a few, measurable quantities, and 2) identifying the “best” emulsion of those we have studied for use in any given experimental situation. Because our interests lie in the examination of crystalline specimens, we've chosen to evaluate an emulsion's signal-to-noise ratio (SNR) as a function of spatial frequency and use this as our critereon for determining the best emulsion.The signal-to-noise ratio in frequency space depends on several factors. First, the signal depends on the speed of the emulsion and its modulation transfer function (MTF). By procedures outlined in, MTF's have been found for all the emulsions tested and can be fit by an analytic expression 1/(1+(S/S0)2). Figure 1 shows the experimental data and fitted curve for an emulsion with a better than average MTF. A single parameter, the spatial frequency at which the transfer falls to 50% (S0), characterizes this curve.

Radiation Damage of Support Films

1981 ◽  
Vol 39 ◽  
pp. 28-29
Author(s):  
H.A. Cohen ◽  
W. Chiu
Keyword(s):  
Transfer Function ◽  
Low Temperatures ◽  
Carbon Support ◽  
Contrast Transfer Function ◽  
Electron Dose ◽  
Imaging Parameters ◽  
Negative Stain ◽  
Phase Corrections ◽  
Two Parameters ◽  
Medium Dose

The goal of imaging the finest detail possible in biological specimens leads to contradictory requirements for the choice of an electron dose. The dose should be as low as possible to minimize object damage, yet as high as possible to optimize image statistics. For specimens that are protected by low temperatures or for which the low resolution associated with negative stain is acceptable, the first condition may be partially relaxed, allowing the use of (for example) 6 to 10 e/Å2. However, this medium dose is marginal for obtaining the contrast transfer function (CTF) of the microscope, which is necessary to allow phase corrections to the image. We have explored two parameters that affect the CTF under medium dose conditions.Figure 1 displays the CTF for carbon (C, row 1) and triafol plus carbon (T+C, row 2). For any column, the images to which the CTF correspond were from a carbon covered hole (C) and the adjacent triafol plus carbon support film (T+C), both recorded on the same micrograph; therefore the imaging parameters of defocus, illumination angle, and electron statistics were identical.

Density-based discrimination of protein and RNA in the ribosome

1992 ◽  
Vol 50 (1) ◽  
pp. 464-465
Author(s):  
Joachim Frank
Keyword(s):  
Transfer Function ◽  
Spatial Frequency ◽  
Three Dimensional ◽  
Wiener Filter ◽  
Dark Field Image ◽  
Dark Field ◽  
Frequency Range ◽  
Bright Field ◽  
Contrast Transfer Function ◽  
Pass Filter

Cryo-electron microscopy combined with single-particle reconstruction techniques has allowed us to form a three-dimensional image of the Escherichia coli ribosome.In the interior, we observe strong density variations which may be attributed to the difference in scattering density between ribosomal RNA (rRNA) and protein. This identification can only be tentative, and lacks quantitation at this stage, because of the nature of image formation by bright field phase contrast. Apart from limiting the resolution, the contrast transfer function acts as a high-pass filter which produces edge enhancement effects that can explain at least part of the observed variations. As a step toward a more quantitative analysis, it is necessary to correct the transfer function in the low-spatial-frequency range. Unfortunately, it is in that range where Fourier components unrelated to elastic bright-field imaging are found, and a Wiener-filter type restoration would lead to incorrect results. Depending upon the thickness of the ice layer, a varying contribution to the Fourier components in the low-spatial-frequency range originates from an “inelastic dark field” image. The only prospect to obtain quantitatively interpretable images (i.e., which would allow discrimination between rRNA and protein by application of a density threshold set to the average RNA scattering density may therefore lie in the use of energy-filtering microscopes.

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