Spatial Coherence Radius: Plane Wave

2009 ◽  
pp. 28-28
Keyword(s):  
Plane Wave ◽  
Spatial Coherence

scholarly journals Spatial coherence computed from a plane‐wave model

1981 ◽  
Vol 69 (S1) ◽  
pp. S70-S71
Author(s):  
Robert L. Field ◽  
Gerald B. Morris ◽  
Homer P. Bucker
Keyword(s):  
Plane Wave ◽  
Spatial Coherence ◽  
Wave Model

scholarly journals Two-Dimensional Spatial Coherence for Ultrasonic DMAS Beamforming in Multi-Angle Plane-Wave Imaging

2019 ◽  
Vol 9 (19) ◽  
pp. 3973 ◽  
Author(s):  
Che-Chou Shen ◽  
Pei-Ying Hsieh
Keyword(s):  
Image Quality ◽  
Plane Wave ◽  
Spatial Coherence ◽  
P Value ◽  
Two Dimensional ◽  
One Dimensional ◽  
Wave Imaging ◽  
Artifact Suppression ◽  
Simulation Results ◽  
Acquisition Delay

Ultrasonic multi-angle plane-wave (PW) coherent compounding relies on delay-and-sum (DAS) beamforming of two-dimensional (2D) echo matrix in both the dimensions PW transmit angle and receiving channel to construct each image pixel. Due to the characteristics of DAS beamforming, PW coherent compounding may suffer from high image clutter when the number of transmit angles is kept low for ultrafast image acquisition. Delay-multiply-and-sum (DMAS) beamforming exploits the spatial coherence of the receiving aperture to suppress clutter interference. Previous attempts to introduce DMAS beamforming into multi-angle PW imaging has been reported but only in either dimension of the 2D echo matrix. In this study, a novel DMAS operation is proposed to extract the 2D spatial coherence of echo matrix for further improvement of image quality. The proposed 2D-DMAS method relies on a flexibly tunable p value to manipulate the signal coherence in the beamforming output. For p = 2.0 as an example, simulation results indicate that 2D-DMAS outperforms other one-dimensional DMAS methods by at least 9.3 dB in terms of ghost-artifact suppression. Experimental results also show that 2D-DMAS provides the highest improvement in lateral resolution by 32% and in image contrast by 15.6 dB relative to conventional 2D-DAS beamforming. Nonetheless, since 2D-DMAS emphasizes signal coherence more than its one-dimensional DMAS counterparts, it suffers from the most elevated speckle variation and the granular pattern in the tissue background.

scholarly journals A United Sign Coherence Factor Beamformer for Coherent Plane-Wave Compounding with Improved Contrast

2020 ◽  
Vol 10 (7) ◽  
pp. 2250 ◽  
Author(s):  
Chen Yang ◽  
Yang Jiao ◽  
Tingyi Jiang ◽  
Yiwen Xu ◽  
Yaoyao Cui
Keyword(s):  
Image Quality ◽  
Plane Wave ◽  
Contrast Ratio ◽  
Spatial Coherence ◽  
Frame Rate ◽  
In Vivo Studies ◽  
Angular Dimension ◽  
One Dimensional ◽  
Coherence Factor

In this study, we present a united sign coherence factor beamformer for coherent plane-wave compounding (CPWC). CPWC is capable of reaching an image quality comparable to the conventional B-mode with a much higher frame rate. Conventional coherence factor (CF) based beamformers for CPWC are based on one-dimensional (1D) frameworks, either in the spatial coherence dimension or angular coherence dimension. Both 1D frameworks do not take into account the coherence information of the dimensions of each other. In order to take full advantage of the radio-frequency (RF) data, this paper proposes a united framework containing both spatial and angular information for CPWC. A united sign coherence factor beamformer (uSCF), which combines the conventional sign coherence factor (SCF) and the united framework, is introduced in the paper as well. The proposed beamformer is compared with the conventional 1D SCF beamformers (spatial and angular dimension beamformers) using simulation, phantom and in vivo studies. In the in vivo images, the proposed method improves the contrast ratio (CR) and generalized contrast-to-noise ratio (gCNR) by 197% and 20% over CPWC. Compared with other 1D methods, uSCF also shows an improved contrast and lateral resolution on all datasets.

Theory and Errors in Stereo Electron Microscopy

1968 ◽  
Vol 26 ◽  
pp. 336-337
Author(s):  
J. M. Pankratz
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Plane Wave ◽  
Focal Length ◽  
Foil Thickness ◽  
Points Of Interest ◽  
Transmission Electron ◽  
Vertical Spacing ◽  
Illuminating System

It is often desirable in transmission electron microscopy to know the vertical spacing of points of interest within a specimen. However, in order to measure a stereo effect, one must have two pictures of the same area taken from different angles, and one must have also a formula for converting measured differences between corresponding points (parallax) into a height differential.Assume (a) that the impinging beam of electrons can be considered as a plane wave and (b) that the magnification is the same at the top and bottom of the specimen. The first assumption is good when the illuminating system is overfocused. The second assumption (the so-called “perspective error”) is good when the focal length is large (3 x 107Å) in relation to foil thickness (∼103 Å).

Quanitative aspects of electron diffraction using electron holography

1995 ◽  
Vol 53 ◽  
pp. 616-617
Author(s):  
E. Völkl ◽  
L.F. Allard ◽  
B. Frost ◽  
T.A. Nolan
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Software Package ◽  
Spatial Coherence ◽  
Electron Holography ◽  
Image Intensity ◽  
Interference Fringes ◽  
Complex Image ◽  
The Difference ◽  
Recorded Image

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.

A hybrid Gaussian and plane wave density functional scheme

1997 ◽  
Vol 92 (3) ◽  
pp. 477-487 ◽  
Author(s):  
GERALD LIPPERT ◽  
JuRG HUTTER ◽  
MICHELE PARRINELLO
Keyword(s):  
Plane Wave ◽  
Density Functional ◽  
Functional Scheme
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