Planar Near-Field Phase Retrieval Using GPUs for Accurate THz Far-Field Prediction

2013 ◽  
Vol 61 (4) ◽  
pp. 1763-1776 ◽  
Author(s):  
Gary Junkin
Keyword(s):  
Phase Retrieval ◽  
Near Field ◽  
Far Field ◽  
Field Phase

Near-field far-field predictions from single-intensity-planar-scan phase retrieval

1989 ◽  
Vol 25 (8) ◽  
pp. 519 ◽  
Author(s):  
A.P. Anderson ◽  
G. Junkin ◽  
J.E. McCormack
Keyword(s):  
Phase Retrieval ◽  
Near Field ◽  
Far Field

Miniaturized beamsplitters realized by X-ray waveguides

2016 ◽  
Vol 72 (5) ◽  
pp. 515-522 ◽  
Author(s):  
Sarah Hoffmann-Urlaub ◽  
Tim Salditt
Keyword(s):  
Interference Pattern ◽  
Phase Retrieval ◽  
Near Field ◽  
Retrieval Algorithm ◽  
Far Field ◽  
X Ray ◽  
Reconstructed Field ◽  
Propagation Methods ◽  
Cladding Material

This paper reports on the fabrication and characterization of X-ray waveguide beamsplitters. The waveguide channels were manufactured by electron-beam lithography, reactive ion etching and wafer bonding techniques, with an empty (air) channel forming the guiding layer and silicon the cladding material. A focused synchrotron beam is efficiently coupled into the input channel. The beam is guided and split into two channels with a controlled (and tunable) distance at the exit of the waveguide chip. After free-space propagation and diffraction broadening, the two beams interfere and form a double-slit interference pattern in the far-field. From the recorded far-field, the near-field was reconstructed by a phase retrieval algorithm (error reduction), which was found to be extremely reliable for the two-channel setting. By numerical propagation methods, the reconstructed field was then propagated along the optical axis, to investigate the formation of the interference pattern from the two overlapping beams. Interestingly, phase vortices were observed and analysed.

Quantitative material decomposition using linear iterative near-field phase retrieval dual-energy x-ray imaging

2020 ◽  
Vol 65 (18) ◽  
pp. 185014
Author(s):  
Heyang Thomas Li ◽  
Florian Schaff ◽  
Linda C P Croton ◽  
Kaye S Morgan ◽  
Marcus J Kitchen
Keyword(s):  
Phase Retrieval ◽  
Near Field ◽  
Dual Energy ◽  
Material Decomposition ◽  
Field Phase ◽  
X Ray ◽  
X Ray Imaging

scholarly journals Comparison of Near- and Far-Field Supercell Inflow Environments Using Radiosonde Observations

2018 ◽  
Vol 146 (8) ◽  
pp. 2403-2415 ◽  
Author(s):  
Andrew R. Wade ◽  
Michael C. Coniglio ◽  
Conrad L. Ziegler
Keyword(s):  
Field Experiments ◽  
Near Field ◽  
Static Stability ◽  
Far Field ◽  
Field Phase ◽  
Convective Storms ◽  
Close Range ◽  
Supercell Thunderstorms

Abstract A great deal of research focuses on how the mesoscale environment influences convective storms, but relatively little is known about how supercells modify the nearby environment. Soundings from three field experiments are used to investigate differences in the near and far inflow of supercell thunderstorms. Close-range soundings in the near inflow of supercells are compared to near-simultaneous soundings released farther away (but still within inflow). Several soundings from the second field phase of the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) supplement the Mesoscale Predictability Experiment (MPEX/MiniMPEX) dataset, resulting in 28 near–far inflow pairs from a wide variety of tornadic and nontornadic supercells. The focus of this study is on a comparison of a subset of 12 near–far inflow pairs taken near tornadic supercells and 16 near–far inflow pairs taken near nontornadic supercells. Similar values of 0–1-km storm-relative helicity (SRH01) are found in the far field of the tornadic and nontornadic supercells, possibly as a result of a difference in mean diurnal timing. However, SRH01 is found to increase substantially in the near field of the tornadic supercells, but not the nontornadic supercells. Differences in the thermodynamic environment include greater moisture above the ground in the far field of the tornadic supercells (despite similar near-ground moisture in both the tornadic and nontornadic subsets) and a subtle increase in static stability near the surface in the nontornadic near inflow.

scholarly journals Near-field phase profile and far-field contrast modulation for micro-lens arrays at the refraction limit

2020 ◽  
Vol 2 (12) ◽  
Author(s):  
M. Yousefi ◽  
D. Nečesal ◽  
T. Scharf ◽  
M. Rossi
Keyword(s):  
Plane Wave ◽  
Point Source ◽  
Gaussian Beam ◽  
Near Field ◽  
Field Pattern ◽  
Far Field ◽  
High Contrast ◽  
Field Phase ◽  
Far Field Pattern ◽  
Micro Lens

Abstract We investigate the far-field pattern generation for a micro-lens array (MLA) illuminated under different conditions. Plane wave and Gaussian beam illumination are considered for an MLA with a small diameter of 27 microns and 30 microns period. At these dimensions, the optical effects are governed by diffraction and refraction and sometimes the regime is called the refraction limit. For Gaussian beam illumination, a high contrast dot pattern can be obtained in the far field according to the self-imaging theory for point source illumination and it is investigated in the simulation part. Also, we designed an interference microscopy setup to record both the phase and intensity in near field behind the MLA and also in the far field. The new instrument allows us to change illumination conditions from plane wave to point source. We then experimentally compare the near-field phase modulation and resulting far-field intensity for different conditions. For plane wave illumination, a high contrast pattern is observed in the far field. For the Gaussian beam illumination, the contrast of the far-field pattern depends on the distance of the source and MLA resulting in high contrast and a larger field of view only for particular distances depending on the interference of the Gaussian beam curved phase front and the MLA.

Linear iterative near-field phase retrieval (LIPR) for dual-energy x-ray imaging and material discrimination

2017 ◽  
Vol 35 (1) ◽  
pp. A30 ◽  
Author(s):  
Heyang (Thomas) Li ◽  
Andrew M. Kingston ◽  
Glenn R. Myers ◽  
Levi Beeching ◽  
Adrian P. Sheppard
Keyword(s):  
Phase Retrieval ◽  
Near Field ◽  
Dual Energy ◽  
Field Phase ◽  
X Ray ◽  
X Ray Imaging ◽  
Material Discrimination
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