scholarly journals Kernel-phases for high-contrast detection beyond the resolution limit

2011 ◽  
Author(s):  
Frantz Martinache
Keyword(s):  
High Contrast ◽  
Resolution Limit ◽  
Contrast Detection

Compositional Analysis of III-V Interface Lattice Images

1980 ◽  
Vol 38 ◽  
pp. 318-319
Author(s):  
A. Olsen ◽  
J.C.H. Spence ◽  
P. Petroff
Keyword(s):  
Crystal Structure ◽  
Image Matching ◽  
Compositional Analysis ◽  
Depth Of Field ◽  
Limit Set ◽  
High Contrast ◽  
Resolution Limit ◽  
Fourier Image ◽  
Lattice Images ◽  
True Structure

Since the point resolution of the JEOL 200CX electron microscope is up = 2.6Å it is not possible to obtain a true structure image of any of the III-V or elemental semiconductors with this machine. Since the information resolution limit set by electronic instability (1) u0 = (2/πλΔ)½ = 1.4Å for Δ = 50Å, it is however possible to obtain, by choice of focus and thickness, clear lattice images both resembling (see figure 2(b)), and not resembling, the true crystal structure (see (2) for an example of a Fourier image which is structurally incorrect). The crucial difficulty in using the information between Up and u0 is the fractional accuracy with which Af and Cs must be determined, and these accuracies Δff/4Δf = (2λu2Δf)-1 and ΔCS/CS = (λ3u4Cs)-1 (for a π/4 phase change, Δff the Fourier image period) are strongly dependent on spatial frequency u. Note that ΔCs(up)/Cs ≈ 10%, independent of CS and λ. Note also that the number n of identical high contrast spurious Fourier images within the depth of field Δz = (αu)-1 (α beam divergence) decreases with increasing high voltage, since n = 2Δz/Δff = θ/α = λu/α (θ the scattering angle). Thus image matching becomes easier in semiconductors at higher voltage because there are fewer high contrast identical images in any focal series.

scholarly journals Author Correction: Selective, high-contrast detection of syngeneic glioblastoma in vivo

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Richard B. Banati ◽  
Paul Wilcox ◽  
Ran Xu ◽  
Grace Yin ◽  
Emily Si ◽  
...  
Keyword(s):  
High Contrast ◽  
Contrast Detection

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

scholarly journals Kernel-phase analysis: Aperture modeling prescriptions that minimize calibration errors

2020 ◽  
Vol 636 ◽  
pp. A72
Author(s):  
Frantz Martinache ◽  
Alban Ceau ◽  
Romain Laugier ◽  
Jens Kammerer ◽  
Mamadou N’Diaye ◽  
...  
Keyword(s):  
Data Analysis ◽  
Projection Operator ◽  
Detection Limits ◽  
Systematic Errors ◽  
Transmission Model ◽  
Data Sets ◽  
High Contrast ◽  
Analysis Method ◽  
Contrast Detection ◽  
The Impact

Context. Kernel phase is a data analysis method based on a generalization of the notion of closure phase, which was invented in the context of interferometry, but it applies to well corrected diffraction dominated images produced by an arbitrary aperture. The linear model upon which it relies theoretically leads to the formation of observable quantities robust against residual aberrations. Aims. In practice, the detection limits that have been reported thus far seem to be dominated by systematic errors induced by calibration biases that were not sufficiently filtered out by the kernel projection operator. This paper focuses on the impact the initial modeling of the aperture has on these errors and introduces a strategy to mitigate them, using a more accurate aperture transmission model. Methods. The paper first uses idealized monochromatic simulations of a nontrivial aperture to illustrate the impact modeling choices have on calibration errors. It then applies the outlined prescription to two distinct data sets of images whose analysis has previously been published. Results. The use of a transmission model to describe the aperture results is a significant improvement over the previous type of analysis. The thus reprocessed data sets generally lead to more accurate results, which are less affected by systematic errors. Conclusions. As kernel-phase observing programs are becoming more ambitious, accuracy in the aperture description is becoming paramount to avoid situations where contrast detection limits are dominated by systematic errors. The prescriptions outlined in this paper will benefit from any attempt at exploiting kernel phase for high-contrast detection.

High Contrast Detection of Water-Filled Terahertz Nanotrenches

2018 ◽  
Vol 6 (21) ◽  
pp. 1800582 ◽  
Author(s):  
Jeeyoon Jeong ◽  
Hyeong Seok Yun ◽  
Dasom Kim ◽  
Kang Sup Lee ◽  
Han-Kyu Choi ◽  
...  
Keyword(s):  
High Contrast ◽  
Contrast Detection

Long-Lasting Detection Facilitation Induced by Gabor Flankers

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 155-155
Author(s):  
Y Tanaka ◽  
D Sagi
Keyword(s):  
Time Course ◽  
Detection Threshold ◽  
Stimulus Onset ◽  
Long Term Memory ◽  
High Contrast ◽  
Spatial Filters ◽  
Contrast Detection ◽  
Separation Threshold ◽  
Sensitivity Changes

Contrast detection threshold of a Gabor signal (GS) is enhanced in the presence of high contrast GS flankers. Repetitive performance of the task induces contrast sensitivity changes on different time scales: minutes when using mental imagery, and weeks in the context of perceptual learning. We tested the time course of lateral enhancement within a single trial, using a forward masking technique. Contrast detection thresholds were measured (2AFC) for a foveal GS target presented briefly (32 ms) preceded by a presentation (80 ms) of two high-contrast GS flankers, with stimulus onset asynchrony (SOA) varying from 0 to 3600 ms. Using target-to-mask separation of 3\lambda and 12\lambda (\lambda =18°, GS wavelength), we found that the 3\lambda separation GS flankers decreased target threshold by 0.25 log units at SOA=0 and by 0.17 log units at 3600 ms. At 12\lambda separation, threshold decreased by 0.11 log units at SOA=0 and by 0.14 log units at 3600 ms. Long-term and short-term enhancements showed similar dependence on stimulus configuration (maximal for collinear target and masks) and local parameters (orientation and spatial frequency differences between target and flankers). The results imply that spatial filters in early vision retain an input trace for as long as a few seconds (up to 14.4 seconds tested). This trace may subserve the consolidation of filter activity into long-term memory.

Far‐Red/Near‐Infrared Emissive (1,3‐Dimethyl)barbituric Acid‐Based AIEgens for High‐Contrast Detection of Metastatic Tumors in the Lung

2018 ◽  
Vol 14 (6) ◽  
pp. 871-876 ◽  
Author(s):  
Heqi Gao ◽  
Pingping Bao ◽  
Shuxin Dai ◽  
Ruihua Liu ◽  
Shenglu Ji ◽  
...  
Keyword(s):  
Barbituric Acid ◽  
Near Infrared ◽  
High Contrast ◽  
Metastatic Tumors ◽  
Contrast Detection

scholarly journals Excitatory and inhibitory lateral interactions effects on contrast detection are modulated by tRNS

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
L. Battaglini ◽  
G. Contemori ◽  
A. Fertonani ◽  
C. Miniussi ◽  
A. Coccaro ◽  
...  
Keyword(s):  
Frontal Cortex ◽  
Random Noise ◽  
Specific Effect ◽  
Inhibitory Effect ◽  
Facilitatory Effect ◽  
High Contrast ◽  
Contrast Detection ◽  
Complex Interactions ◽  
Transcranial Random Noise Stimulation ◽  
Increased Sensitivity

AbstractContrast sensitivity for a Gabor signal is affected by collinear high-contrast Gabor flankers. The flankers reduce (inhibitory effect) or increase (facilitatory effect) sensitivity, at short (2λ) and intermediate (6λ) target-to-flanker separation respectively. We investigated whether these inhibitory/facilitatory sensitivity effects are modulated by transcranial random noise stimulation (tRNS) applied to the occipital and frontal cortex of human observers during task performance. Signal detection theory was used to measure sensitivity (d’) and the Criterion (C) in a contrast detection task, performed with sham or tRNS applied over the occipital or the frontal cortex. After occipital stimulation results show a tRNS-dependent increased sensitivity for the single Gabor signal of low but not high contrast. Moreover, results suggest a dissociation of the tRNS effect when the Gabor signal is presented with the flankers, consisting in a general increased sensitivity at 2λ where the flankers had an inhibitory effect (reduction of inhibition) and a decreased sensitivity at 6λ where the flankers had a facilitatory effect on the Gabor signal (reduction of facilitation). After a frontal stimulation, no specific effect of the tRNS was found. We account for these complex interactions between tRNS and flankers by assuming that tRNS not only enhances feedforward input from the Gabor signal to the cortex, but also enhances the excitatory or inhibitory lateral intracortical input from the flankers. The boosted lateral input depends on the excitation-inhibition (E/I) ratio, namely when the lateral input is weak, it is boosted by tRNS with consequent modification of the contrast-dependent E/I ratio.

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