Search results for "interferometry"
showing 10 items of 343 documents
Simulations of Array Configurations for the Square Kilometre Array (SKA)
2010
The Square Kilometre Array (SKA) is a new generation radio telescope for the next decades, working at metre to centimetre wavelengths. The SKA will be operational at the same time than other new optical, X-ray and Gamma-ray telescopes. It is of extreme importance that the SKA becomes competitive and complementary to those instruments. An extensive study of technologies and possible configurations involved is needed to ensure the SKA will reach the design specifications. To compare imaging capabilities between different SKA configurations or between the SKA and other instruments, we have implemented figures of merit based on several characteristics of these instruments. In this work we are p…
Normal metal - insulator - superconductor interferometer
2003
Hybrid normal metal - insulator - superconductor microstructures suitable for studying an interference of electrons were fabricated. The structures consist of a superconducting loop connected to a normal metal electrode through a tunnel barrier . An optical interferometer with a beam splitter can be considered as a classical analogue for this system. All measurements were performed at temperatures well below 1 K. The interference can be observed as periodic oscillations of the tunnel current (voltage) through the junction at fixed bias voltage (current) as a function of a perpendicular magnetic field. The magnitude of the oscillations depends on the bias point. It reaches a maximum at energ…
Remote monitoring of building oscillation modes by means of real-time Mid Infrared Digital Holography
2016
AbstractNon-destructive measurements of deformations are a quite common application of holography but due to the intrinsic limits in the interferometric technique, those are generally confined only to small targets and in controlled environment. Here we present an advanced technique, based on Mid Infrared Digital Holography (MIR DH), which works in outdoor conditions and provides remote and real-time information on the oscillation modes of large engineering structures. Thanks to the long wavelength of the laser radiation, large areas of buildings can be simultaneously mapped with sub-micrometric resolution in terms of their amplitude and frequency oscillation modes providing all the modal p…
Observer for a thick layer of solid deuterium-tritium using backlit optical shadowgraphy and interferometry.
2007
Our work is in the context of the French "laser megajoule" project, about fusion by inertial confinement. The project leads to the problem of characterizing the inner surface, of the approximately spherical target, by optical shadowgraphy techniques. Our work is entirely based on the basic idea that optical shadowgraphy produces "caustics" of systems of optical rays, which contain a great deal of 3D information about the surface to be characterized. We develop a method of 3D reconstruction based upon this idea plus a "small perturbations" technique. Although computations are made in the special "spherical" case, the method is in fact general and may be extended to several other situations.
Anterior chamber depth measurement in teenagers. Comparison of two techniques
2013
Purpose: The aim of this study is to determine the anterior chamber depth (ACD) in teenagers using two different devices: partial coherence interferometry IOLMaster (Carl Zeiss Meditec) and anterior segment optical coherence tomography (Visante TM OCT, Carl Zeiss Meditec) and to evaluate the degree of agreement between ACD measurements carried out by both instruments. Methods: In this prospective study 68 eyes of 34 emmetropic Caucasic patients (18 girls and 16 boys) were analysed. ACD was measured from the anterior corneal surface to anterior surface of the crystalline lens. For each age the ACD size was calculated and the difference between IOLMaster and Visante-OCT measurements was analy…
Photoelastic stress pattern analysis using Fourier transform with carrier fringes: influence of quarter-wave plate error
2002
The Fourier transform method, widely applied in photomechanics for the automated analysis of interferometric fringe patterns, has been recently extended to the photoelastic isochromatic fringe patterns analysis. Unfortunately, its use in photoelasticity involves some limitations that have not been completely highlighted in literature. This work deals with the influence of the quarter-wave plate tolerance on the evaluation of the retardation. Both theoretical and experimental analyses have shown that the quarter-wave plate error does not affect the retardation only if the principal stress directions in the model and in the carrier are aligned. In general, instead, the tolerance of the quarte…
Coherent Microscopy for 3-D Movement Monitoring and Super-Resolved Imaging
2010
In this chapter we present three types of microscopy-related configurations while the first one is used for 3-D movement monitoring of the inspected samples, the second one is used for super-resolved 3-D imaging, and the last one presents an overview digital holographic microscopy applications. The first configuration is based on temporal tracking of secondary reflected speckles when imaged by properly defocused optics. We validate the proposed scheme by using it to monitor 3-D spontaneous contraction of rat’s cardiac muscle cells while allowing nanometric tracking accuracy without interferometric recording. The second configuration includes projection of temporally varying speckle patterns…
A possible jet precession in the periodic quasar B0605-085
2010
The quasar B0605-085 (OH 010) shows a hint for probable periodical variability in the radio total flux-density light curves. We study the possible periodicity of B0605-085 in the total flux-density, spectra and opacity changes in order to compare it with jet kinematics on parsec scales. We have analyzed archival total flux-density variability at ten frequencies (408 MHz, 4.8 GHz, 6.7 GHz, 8 GHz, 10.7 GHz, 14.5 GHz, 22 GHz, 37 GHz, 90 GHz, and 230 GHz) together with the archival high-resolution very long baseline interferometry data at 15 GHz from the MOJAVE monitoring campaign. Using the Fourier transform and discrete autocorrelation methods we have searched for periods in the total flux-de…
THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope
2020
This is an open access article.-- Full list of authors: Broderick, Avery E.; Gold, Roman; Karami, Mansour; Preciado-López, Jorge A.; Tiede, Paul; Pu, Hung-Yi; Akiyama, Kazunori; Alberdi, Antxon; Alef, Walter; Asada, Keiichi; Azulay, Rebecca; Baczko, Anne-Kathrin; Baloković, Mislav; Barrett, John; Bintley, Dan; Blackburn, Lindy; Boland, Wilfred; Bouman, Katherine L.; Bower, Geoffrey C.; Bremer, Michael; Brinkerink, Christiaan D.; Brissenden, Roger; Britzen, Silke; Broguiere, Dominique; Bronzwaer, Thomas; Byun, Do-Young; Carlstrom, John E.; Chael, Andrew; Chatterjee, Shami; Chatterjee, Koushik; Chen, Ming-Tang; Chen, Yongjun; Cho, Ilje; Conway, John E.; Cordes, James M.; Crew, Geoffrey B.; Cu…
Calibration of a neutron time-of-flight multidetector system for an intensity interferometry experiment
2004
We present the details of an experiment on light particle interferometry. In particular, we focus on a time-of-flight technique which uses a cyclotron RF signal as a start and a liquid scintillator time signal as a stop, to measure neutron energy in the range of En approximate to 1.8-150 MeV. This dynamic range (up to 300 ns) is much larger than the beam bunch separation (54 ns) of the AGOR cyclotron (KVI). However, the problem of a short burst period is overcome by using the time information obtained from a fast projectile fragment phoswich detector. The complete analysis procedure to extract the final neutron kinetic energy spectra, is discussed. (C) 2003 Elsevier B.V. All rights reserved.