scholarly journals High-resolution nanopatterning by achromatic spatial frequency multiplication with electroplated grating structures

2012 ◽  
Vol 30 (3) ◽  
pp. 031603 ◽  
Author(s):  
Li Wang ◽  
Bernd Terhalle ◽  
Mohamad Hojeij ◽  
Vitaliy A. Guzenko ◽  
Yasin Ekinci
Keyword(s):  
High Resolution ◽  
Spatial Frequency ◽  
Frequency Multiplication

High-resolution Fresnel zone plate fabrication by achromatic spatial frequency multiplication with extreme ultraviolet radiation

2011 ◽  
Vol 36 (10) ◽  
pp. 1860 ◽  
Author(s):  
Sankha Subhra Sarkar ◽  
Harun H. Solak ◽  
Menouer Saidani ◽  
Christian David ◽  
J. Friso van der Veen
Keyword(s):  
High Resolution ◽  
Spatial Frequency ◽  
Ultraviolet Radiation ◽  
Extreme Ultraviolet ◽  
Fresnel Zone ◽  
Zone Plate ◽  
Fresnel Zone Plate ◽  
Frequency Multiplication ◽  
Extreme Ultraviolet Radiation

Three-fold astigmatism: An important TEM aberration

1993 ◽  
Vol 51 ◽  
pp. 972-973 ◽  
Author(s):  
O.L. Krivanek ◽  
M.L. Leber
Keyword(s):  
High Resolution ◽  
Spatial Frequency ◽  
Field Emission ◽  
Azimuthal Angle ◽  
Hollow Cone ◽  
Small Probe ◽  
Wide Range ◽  
High Resolution Images ◽  
Image Position

Three-fold astigmatism resembles regular astigmatism, but it has 3-fold rather than 2-fold symmetry. Its contribution to the aberration function χ(q) can be written as:where A3 is the coefficient of 3-fold astigmatism, λ is the electron wavelength, q is the spatial frequency, ϕ the azimuthal angle (ϕ = tan-1 (qy/qx)), and ϕ3 the direction of the astigmatism.Three-fold astigmatism is responsible for the “star of Mercedes” aberration figure that one obtains from intermediate lenses once their two-fold astigmatism has been corrected. Its effects have been observed when the beam is tilted in a hollow cone over a wide range of angles, and there is evidence for it in high resolution images of a small probe obtained in a field emission gun TEM/STEM instrument. It was also expected to be a major aberration in sextupole-based Cs correctors, and ways were being developed for dealing with it on Cs-corrected STEMs.

Spatial-frequency multiplication via absorbance modulation

2007 ◽  
Vol 91 (9) ◽  
pp. 094103 ◽  
Author(s):  
Hsin-Yu Tsai ◽  
Gregory M. Wallraff ◽  
Rajesh Menon
Keyword(s):  
Spatial Frequency ◽  
Frequency Multiplication

scholarly journals Alpha-Null Defocus: an Optimum Defocus Condition with Relevance for Focal-Series Reconstruction

2001 ◽  
Vol 7 (S2) ◽  
pp. 916-917 ◽  
Author(s):  
Michael A. O’Keefe
Keyword(s):  
High Resolution ◽  
Spatial Frequency ◽  
Super Resolution ◽  
High Resolution Electron Microscopy ◽  
Phase Changes ◽  
Objective Lens ◽  
Microscope Objective ◽  
Reconstruction Methods ◽  
Electron Microscopes ◽  
Microscope Objective Lens

Two optimum defocus conditions are well known to users of high-resolution transmission electron microscopes. Scherzer defocus is useful in high-resolution electron microscopy (HREM) because it produces an image of the specimen “projected potential” to the resolution of the microscope. Lichte defocus is useful in electron holography because it optimizes sampling in frequency-space by minimizing the slope of the microscope objective lens phase change out to the highest spatial frequency in the hologram, consequently minimizing dispersion. For focal-series reconstruction, the requirement to maximize transfer into the image of high-frequency diffracted beam amplitudes leads to a third optimum defocus condition.Image reconstruction methods allow the achievement of super-resolution - resolution beyond the native (Scherzer) resolution of the microscope - by correction of the phase changes introduced by the microscope objective lens. One such method is focal-series reconstruction, in which diffracted-beam information obtained at several different focus values is combined. to produce a valid super-resolution result, it is necessary to ensure that every spatial frequency is represented appropriately. Suitable choice of an optimum defocus produces optimum transfer of diffracted-beam amplitudes at any chosen spatial frequency.

scholarly journals Effect of Filtered Back-Projection Filters to Low-Contrast Object Imaging in Ultra-High-Resolution (UHR) Cone-Beam Computed Tomography (CBCT)

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6416
Author(s):  
Sunghoon Choi ◽  
Chang-Woo Seo ◽  
Bo Kyung Cha
Keyword(s):  
Computed Tomography ◽  
High Resolution ◽  
Spatial Frequency ◽  
Spatial Resolution ◽  
Cone Beam Computed Tomography ◽  
Cone Beam ◽  
Acquisition Time ◽  
Imaging Protocol ◽  
Low Contrast ◽  
Smoothing Window

In this study, the effect of filter schemes on several low-contrast materials was compared using standard and ultra-high-resolution (UHR) cone-beam computed tomography (CBCT) imaging. The performance of the UHR-CBCT was quantified by measuring the modulation transfer function (MTF) and the noise power spectrum (NPS). The MTF was measured at the radial location around the cylindrical phantom, whereas the NPS was measured in the eight different homogeneous regions of interest. Six different filter schemes were designed and implemented in the CT sinogram from each imaging configuration. The experimental results indicated that the filter with smaller smoothing window preserved the MTF up to the highest spatial frequency, but larger NPS. In addition, the UHR imaging protocol provided 1.77 times better spatial resolution than the standard acquisition by comparing the specific spatial frequency (f50) under the same conditions. The f50s with the flat-top window in UHR mode was 1.86, 0.94, 2.52, 2.05, and 1.86 lp/mm for Polyethylene (Material 1, M1), Polystyrene (M2), Nylon (M3), Acrylic (M4), and Polycarbonate (M5), respectively. The smoothing window in the UHR protocol showed a clearer performance in the MTF according to the low-contrast objects, showing agreement with the relative contrast of materials in order of M3, M4, M1, M5, and M2. In conclusion, although the UHR-CBCT showed the disadvantages of acquisition time and radiation dose, it could provide greater spatial resolution with smaller noise property compared to standard imaging; moreover, the optimal window function should be considered in advance for the best UHR performance.

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