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1
Chesneau, O., K. Rousselet-Perraut et F. Vakili. « Interferometry and Stellar Magnetism ». International Astronomical Union Colloquium 175 (2000) : 174–77. http://dx.doi.org/10.1017/s0252921100055792.
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AbstractThe classical detection of magnetic fields in Be stars remains a challenge due to the sensitivity threshold and geometrical cancelation of the field effects. We propose to study the Zeeman effect using Spectro-Polarimetric INterferometry (SPIN) which consists of the simultaneous use of polarimetry and very high angular resolution provided by long baseline interferometers. As monitoring of the instrumental polarisation is mandatory in order to calibrate interferometric observations in any case, the polarised signal is a natural by-product of interferometers. This method will be tested on the GI2T interferometer thanks to its high spectral resolution and its polarimetric capabilities.
2
McAlister, Harold A. « Overview of Multiple–Aperture Interferometry Binary Star Results from the Northern Hemisphere ». Proceedings of the International Astronomical Union 2, S240 (août 2006) : 35–44. http://dx.doi.org/10.1017/s1743921307003778.
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AbstractLong-baseline optical interferometry (LBI) can nearly close the gap in selection space between astrometric and spectroscopic detection of binary star systems, bringing the complementary powers of astrometry and spectroscopy to bear on a complete dynamical understanding of such systems, particularly including the determination of the masses of the individual stellar components. In the case of double-lined spectroscopic systems, their resolution by long-baseline interferometry also yields the orbital parallax and hence the luminosities of the individual stars. In some of these cases, the angular diameters of one or more components are accessible, and so a complete specification of a star in terms of its mass, radius and luminosity is made.The northern hemisphere is now equipped with several interferometers of unprecedented capability in terms of their baseline sizes, numbers of telescopes and telescope apertures. These instruments, most notably the Palomar Testbed Interferometer at Mt. Palomar Observatory, have produced very significant results of a number of interesting systems fulfilling interferometry's promise to produce fundamental astrophysical data at levels of accuracy that challenge or confirm astrophysical theory.This paper presents basic principles of long-baseline interferometric study of binary stars and summarizes results from northern interferometers with specific examples of their broad impact on binary star astronomy.
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Jankov, S. « Astronomical optical interferometry, I : Methods and instrumentation ». Serbian Astronomical Journal, no 181 (2010) : 1–17. http://dx.doi.org/10.2298/saj1081001j.
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Previous decade has seen an achievement of large interferometric projects including 8-10m telescopes and 100m class baselines. Modern computer and control technology has enabled the interferometric combination of light from separate telescopes also in the visible and infrared regimes. Imaging with milli-arcsecond (mas) resolution and astrometry with micro-arcsecond (?as) precision have thus become reality. Here, I review the methods and instrumentation corresponding to the current state in the field of astronomical optical interferometry. First, this review summarizes the development from the pioneering works of Fizeau and Michelson. Next, the fundamental observables are described, followed by the discussion of the basic design principles of modern interferometers. The basic interferometric techniques such as speckle and aperture masking interferometry, aperture synthesis and nulling interferometry are discussed as well. Using the experience of past and existing facilities to illustrate important points, I consider particularly the new generation of large interferometers that has been recently commissioned (most notably, the CHARA, Keck, VLT and LBT Interferometers). Finally, I discuss the longer-term future of optical interferometry, including the possibilities of new large-scale ground-based projects and prospects for space interferometry.
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Trolinger, James D., Amit Lal, Joshua Jo et Stephen Kupiec. « Programmable Holographic Optical Elements as Adaptive Optics in Optical Diagnostics Devices ». Key Engineering Materials 437 (mai 2010) : 108–12. http://dx.doi.org/10.4028/www.scientific.net/kem.437.108.
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This paper reports a combined, Hartmann/Digital Holographic interferometry inspection system for inspecting optical components that do not easily lend themselves to conventional interferometric or Hartmann inspection. A programmable holographic optical element (HOE) preconditions wavefronts to extend the dynamic range of interferometry measurements and also transforms the same system into a scanning Hartmann operation, which has lower resolution but higher dynamic range. Inspecting aspherical surfaces with existing interferometers requires special, computer generated holographic optical elements to transform the wavefront to within the dynamic range of the interferometer. The Hartmann measurement provides the information required to precondition a reference wave that avails the measurement process to the more precise phase shifting interferometry. The SLM offers yet other benefits including a method for minimizing the effects of speckle on the measurement. The paper provides example measurements, discusses the limitations, and suggests other potential applications.
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Cavedo, Federico, Parisa Esmaili, Alessandro Pesatori et Michele Norgia. « Self-mixing Interferometer : Frequency Modulation Noise Dependence on Laser Source ». Journal of Physics : Conference Series 2698, no 1 (1 février 2024) : 012019. http://dx.doi.org/10.1088/1742-6596/2698/1/012019.
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Abstract The acquisition of frequency modulation in self-mixing interferometry opens the way to a new generation of instruments, with significantly superior performance compared to traditional self-mixing interferometers. In this work, we experimentally confirm the noise limit dependence of this kind of interferometer on the laser source linewidth. The obtained results confirm the theoretical prediction, opening the way for a deeper improvement in sensitivity, by employing narrow-line lasers in this interferometric configuration.
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Yankelev, Dimitry, Chen Avinadav, Nir Davidson et Ofer Firstenberg. « Atom interferometry with thousand-fold increase in dynamic range ». Science Advances 6, no 45 (novembre 2020) : eabd0650. http://dx.doi.org/10.1126/sciadv.abd0650.
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The periodicity inherent to any interferometric signal entails a fundamental trade-off between sensitivity and dynamic range of interferometry-based sensors. Here, we develop a methodology for substantially extending the dynamic range of such sensors without compromising their sensitivity, stability, and bandwidth. The scheme is based on simultaneous operation of two nearly identical interferometers, providing a moiré-like period much larger than 2π and benefiting from close-to-maximal sensitivity and from suppression of common-mode noise. The methodology is highly suited to atom interferometers, which offer record sensitivities in measuring gravito-inertial forces but suffer from limited dynamic range. We experimentally demonstrate an atom interferometer with a dynamic-range enhancement of more than an order of magnitude in a single shot and more than three orders of magnitude within a few shots for both static and dynamic signals. This approach can considerably improve the operation of interferometric sensors in challenging, uncertain, or rapidly varying conditions.
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Stee, Ph, D. Bonneau, F. Morand, D. Mourard et F. Vakili. « Current studies and future prospects in stellar-structure imaging with the GI2T ». Symposium - International Astronomical Union 176 (1996) : 191–98. http://dx.doi.org/10.1017/s0074180900083224.
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The capability of optical long baseline interferometry for measuring the angular diameter of stars or binary separation is now well established. However, for the imaging of photospheric disk structures one needs very long baseline interferometers operated in the multi-telescope phase-closure technique. In this paper we will stress the capability of spectro-interferometric measurements to constrain the physics of hot stars. We will report our study of the interacting binary, β Lyrae, and the mass-losing Be star γ Cassiopeiae. We will look at the interpretation of both the modulus and phase data recorded by the long baseline interferometer GI2T in the southern France. The performances and limitations of spectro-interferometric techniques will also be discussed through some of the most exciting prospects within the reach of current interferometers.
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Noordam, J. E. « European Space Interferometry ». Symposium - International Astronomical Union 166 (1995) : 345. http://dx.doi.org/10.1017/s0074180900228349.
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Optical interferometry is ensconced as an ‘area of future interest’ (a socalled Green Dream) in Horizon 2000, the long-term scientific plan of ESA. Over the years, there have been three large ESA workshops on Space interferometry, where many different concepts and designs were proposed, and several ESA committees have studied the possibilities. These committees were also involved, in an advisory role, in a modest technological research program (TRP) by ESTEC. In 1990, the Space Interferometry Study Team (SIST) recommended building an optical interferometer, consisting of 10-15 small telescopes attached to an 100m inflatable structure, as a scientifically interesting first step. The SIST even produced a workable design. It quickly became clear, however, that such an undertaking would cost much more than an ESA cornerstone mission, and was thus far too ambitious. Simultaneously, another ESA study team (LIST) came to the conclusion that the Moon, contrary to earlier beliefs, does not offer a particularly suitable environment for interferometry. At the Beaulieu workshop in 1992, it was decided to try to achieve cornerstone status for one or two smaller interferometry missions in Space: a 10m UV imaging interferometer, or an interferometric successor to the astrometry satellite Hipparchos. The latter seems to have a good chance at the moment, in the form of the GAIA proposal which has been selected for further study for the new ‘post-Horizon 2000’ program. GAIA may have some limited imaging capability, but a true imaging interferometer in Space will have to wait for a few decades yet.
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Pushin, D. A., M. G. Huber, M. Arif, C. B. Shahi, J. Nsofini, C. J. Wood, D. Sarenac et D. G. Cory. « Neutron Interferometry at the National Institute of Standards and Technology ». Advances in High Energy Physics 2015 (2015) : 1–7. http://dx.doi.org/10.1155/2015/687480.
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Neutron interferometry has proved to be a very precise technique for measuring the quantum mechanical phase of a neutron caused by a potential energy difference between two spatially separated neutron paths inside interferometer. The path length inside the interferometer can be many centimeters (and many centimeters apart) making it very practical to study a variety of samples, fields, potentials, and other macroscopic medium and quantum effects. The precision of neutron interferometry comes at a cost; neutron interferometers are very susceptible to environmental noise that is typically mitigated with large, active isolated enclosures. With recent advances in quantum information processing especially quantum error correction (QEC) codes we were able to demonstrate a neutron interferometer that is insensitive to vibrational noise. A facility at NIST’s Center for Neutron Research (NCNR) has just been commissioned with higher neutron flux than the NCNR’s older interferometer setup. This new facility is based on QEC neutron interferometer, thus improving the accessibility of neutron interferometry to the greater scientific community and expanding its applications to quantum computing, gravity, and material research.
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Monnier, John D. « Infrared interferometry of circumstellar envelopes ». Symposium - International Astronomical Union 191 (1999) : 321–30. http://dx.doi.org/10.1017/s0074180900203239.
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This paper will review the technical progress of interferometric infrared observing techniques from the first 2-element interferometer 25 years ago to the 3+ element arrays now coming into service. To date, only the Infrared Spatial Interferometer (ISI) has published separate-element interferometric data on circumstellar dust shells in the infrared and many of these scientific results will be discussed. Speckle interferometry has also evolved significantly over the last few decades as slit-scanning techniques over single-pixel detectors have largely been replaced by fast-readout of large format detector arrays. Important near-infrared and mid-infrared results derived from speckle data will also be reviewed.Until recently, two-dimensional information about circumstellar dust distributions has been sorely lacking, hence detections of dust shell asymmetries have been difficult and uncertain. New speckle observations using modern, 10-m class telescopes have yielded surprising results, demonstrating the importance of accurate closure phase information in interpreting interferometric data. These discoveries hopefully precursor those to be made from closure-phase imaging with the new generation of separate-element, interferometric arrays.
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Müller, André F., Claas Falldorf, Gerd Ehret et Ralf B. Bergmann. « Messen von asphärischen Linsenformen mittels räumlicher Kohärenz ». tm - Technisches Messen 86, no 6 (26 mai 2019) : 325–34. http://dx.doi.org/10.1515/teme-2019-0025.
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ZusammenfassungWir zeigen den Vergleich zweier interferometrischer Verfahren zur Formprüfung anhand einer Messung an einer Zylinderlinse. Das erste Verfahren, die Multiple Aperture Shear Interferometry (MArS), basiert auf der Messung der Kohärenzfunktion mittels eines Scher-Interferometers. Es erlaubt interferometrische Messungen unter gleichzeitiger Verwendung mehrerer unabhängiger und teilkohärenter Lichtquellen, und ermöglicht so eine flexible, an den Prüfling anpassbare Ausleuchtung. Als Vergleichsverfahren kommt die Computational Shear Interferometry (CoSI) zur Messung von Wellenfronten zum Einsatz. Da beide Messverfahren auf einem Scher-Interferometer basieren, ist ein direkter Vergleich unter identischen Umgebungsbedingungen möglich.
12
Petrov, R. G., S. Lagarde et M. N'GUYEN Van KY. « Differential interferometry imaging ». Symposium - International Astronomical Union 176 (1996) : 181–90. http://dx.doi.org/10.1017/s0074180900083212.
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Differential Interferometry (DI) combines high spectral and high spatial resolution. On non resolved objects, it yields the angular variation of the source photocenter as a function of wavelength which has been shown theoretically and experimentally to complement very usefully both interferometric and spectroscopic data in a large number of astrophysical problems. This paper presents the general characteristics of DI which are likely to allow improvements of the Doppler images of stellar surface structures as soon as interferometers with large apertures and baselines approaching 100 m are available.
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TEN BRUMMELAAR, T., P. TUTHILL et G. VAN BELLE. « INTRODUCTION ». Journal of Astronomical Instrumentation 02, no 02 (décembre 2013) : 1303001. http://dx.doi.org/10.1142/s2251171713030013.
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After nearly one and a half centuries of effort, one of the most pernicious problems in observational astronomy — obtaining resolved images of the stars — is finally yielding to advances in modern instrumentation. The exquisite precision delivered by today's interferometric observatories is rapidly being applied to more and more branches of optical astronomy. The most capable interferometers in the Northern Hemisphere, both located in the United States are the Navy Precision Optical Interferometer (NPOI) in Arizona and the Center for High Angular Resolution Astronomy Array (CHARA) run by Georgia State University and located in California. In early 2013 these two groups held a joint meeting hosted by the Lowell Observatory in Flagstaff. All major groups working in the field were represented at this meeting and it was suggested to us by this Journal that this was an excellent opportunity to put together a special issue on interferometry. In order to be as broad as possible, those who did not attend the CHARA/NPOI meeting were also solicited to make a contribution. The result is this collection of papers representing a snap shot of the state of the art of ground based optical and near infrared interferometry.
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Samoylenko, O., O. Adamenko et V. Kalynichenko. « The Method and the Results of the Direct Comparison of the Laser Interferometers Renishaw Xl-80 ». Metrology and instruments, no 4 (30 août 2018) : 15–21. http://dx.doi.org/10.33955/2307-2180(4)2018.15-21.
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The method of the direct comparison of the laser interferometers and method processing of the interferometry measurement results by the least square method (LSM) is present. The additive part of the measurement error for each pair of the interferometers is evaluated and the multiplicative part of the measurement error for each interferometer is evaluated too by LSM. Uncertainty by A tape by LSM is evaluated for all parameters. Results of the comparison of the three interferometers are presented.
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ten Brummelaar, Theo A. « Reducing Binary Star Data from Long-Baseline Interferometers ». Proceedings of the International Astronomical Union 2, S240 (août 2006) : 178–87. http://dx.doi.org/10.1017/s1743921307003997.
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AbstractProcessing long-baseline interferometry data presents a unique set of complications: How does one derive relative astrometry from interferometric data? How can 1-D interferometric results be used to solve a 2-D orbit? How can baseline-only solutions be combined with historical data and how should interferometric data be published so that they can be combined with archived data? What new techniques for interferometers are coming on line? This paper contains a brief review of interferometric data analysis in the context of binary star astrometry.
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Rodríguez, Luis F. « SpS1-Instrumentation for sub-millimeter spectroscopy ». Proceedings of the International Astronomical Union 5, H15 (novembre 2009) : 527–28. http://dx.doi.org/10.1017/s1743921310010525.
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The fields of millimeter and sub-millimeter interferometry have been developing for more than 30 years. At millimeter wavelengths the most important interferometers are the Combined Array for Research in Millimeter-Wave Astronomy (CARMA), the Plateau de Bure Interferometer (PdBI), and the Nobeyama Millimeter Array (NMA). At sub-millimeter wavelenghts, the most powerful interferometer is the SubMillimeter Array (SMA, for a detailed description, see Ho et al. 2004).
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Jalil, Muhammad Arif Bin. « An Overview on Several Types of the Optical Interferometers ». International Journal for Research in Applied Science and Engineering Technology 12, no 6 (30 juin 2024) : 454–58. http://dx.doi.org/10.22214/ijraset.2024.63070.
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Abstract: A common research instrument in many branches of science and engineering is the interferometer. Because they can identify and analyse interference patterns caused by the combination of light sources, these mid- to late-19th-century technologies are known as interferometers. The tool used for this process is called a "interferometer" or "interfere-meter." Interferometers are remarkably versatile devices that enable the development of highly accurate optical sensors for a wide range of applications. This article discussed the principles of interferometry as well as three different interferometer configurations. The chosen configuration will be influenced by the machinery, mechanical stability, laser coherence, and particular goals. Interferometers are widely used in lab-on-a-chip systems for non-invasive biomolecule research, astronomy, and gravitational wave detection.
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Yang, Yichao, Kohei Yamamoto, Miguel Dovale Álvarez, Daikang Wei, Juan José Esteban Delgado, Vitali Müller, Jianjun Jia et Gerhard Heinzel. « On-Axis Optical Bench for Laser Ranging Instruments in Future Gravity Missions ». Sensors 22, no 5 (7 mars 2022) : 2070. http://dx.doi.org/10.3390/s22052070.
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The laser ranging interferometer onboard the Gravity Recovery and Climate Experiment Follow-On mission proved the feasibility of an interferometric sensor for inter-satellite length tracking with sub-nanometer precision, establishing an important milestone for space laser interferometry and the general expectation that future gravity missions will employ heterodyne laser interferometry for satellite-to-satellite ranging. In this paper, we present the design of an on-axis optical bench for next-generation laser ranging which enhances the received optical power and the transmit beam divergence, enabling longer interferometer arms and relaxing the optical power requirement of the laser assembly. All design functionalities and requirements are verified by means of computer simulations. A thermal analysis is carried out to investigate the robustness of the proposed optical bench to the temperature fluctuations found in orbit.
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Stee, Ph, A. Meilland et O. L. Creevey. « Interferometry of massive stars : the next step ». Proceedings of the International Astronomical Union 9, S307 (juin 2014) : 480–89. http://dx.doi.org/10.1017/s174392131400742x.
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AbstractWe present some new and interesting results on the complementarity between asteroseismology and interferometry, the detection of non-radial pulsations in massive stars and the possibility for evidencing differential rotation on the surface of Bn stars. We also discuss the curretn interferometric facilities, namely the Very Large Telescope Interferometer (VLTI)/AMBER, VLTI/MIDI, VLTI/PIONIER within the European Southern Observatory (ESO) context and the Center for High Angular Resolution Astronomy (CHARA) array with their current limitations. The forthcoming second-generation VLTI instruments GRAVITY and MATISSE are presented as well as the FRIEND prototype in the visible spectral domain and an update of the Navy Precision Optical Interferometer (NPOI). A conclusion is presented with a special emphasis on the foreseen difficulties for a third generation of interferometric instruments within the (budget limited) Extremely Large Telescope framework and the need for strong science cases to push a future visible beam combiner.
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Aydin, Deniz, Jack A. Barnes et Hans-Peter Loock. « In-fiber interferometry sensors for refractive index ». Applied Physics Reviews 10, no 1 (mars 2023) : 011307. http://dx.doi.org/10.1063/5.0105147.
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Compact interferometers based on waveguiding structures have found countless applications in refractive index measurements, chemical sensing, as well as temperature and pressure measurements. The most common fiber devices are based on Mach–Zehnder interferometry and Michelson interferometry—two design concepts that can readily be implemented using simple fiber optic components, such as mode splitters and combiners, fiber optic gratings, and fiber tapers, among others. Fiber interferometry can also be conducted based on the Sagnac effect and the Young (double-slit) interferometer. In this review, we examine and compare over 400 fiber optic interferometers as well as more than 60 fiber optic refractive sensors based on fiber optic cavities. Even though many of the devices show temperature-, strain-, and pressure-sensitivity, we focus our review on refractive index measurements, as these are the most common applications. Many devices were characterized by their inventors using their sensitivity to refractive index changes. While the sensitivity is an important characteristic of the device, it does not easily relate to the smallest resolvable refractive index change or the limit of detection when applied to chemical measurements. Instead, we propose here that one should use the figure of merit, which is defined through the refractive index sensitivity and the width of an interferometer fringe. Using simple assumptions, we were able to mathematically relate the sensitivity and the figure of merit to common design parameters, such as the length of the interferometer arms, the operating wavelength, refractive indices of the fiber and the sample, as well as an overlap parameter, which describes the fraction of the guided wave in the sensing arm that interacts with the sample. We determined this overlap parameter for each reviewed device from the reported interferograms. Our meta-analysis provides for the first time simple and easily applicable guidance to increase the figure of merit of fiber optic interferometers and fiber optic cavities with regard to their ability to detect small refractive index changes. A high figure of merit allows measuring very small refractive index changes such as those of gases at different pressures or of very dilute solutions.
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Pérez-Callejo, G., V. Bouffetier, L. Ceurvorst, T. Goudal, M. P. Valdivia, D. Stutman et A. Casner. « TIA : A forward model and analyzer for Talbot interferometry experiments of dense plasmas ». Physics of Plasmas 29, no 4 (avril 2022) : 043901. http://dx.doi.org/10.1063/5.0085822.
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Interferometry is one of the most sensitive and successful diagnostic methods for plasmas. However, owing to the design of most common interferometric systems, the wavelengths of operation and, therefore, the range of densities and temperatures that can be probed are severely limited. Talbot–Lau interferometry offers the possibility of extending interferometry measurements to x-ray wavelengths by means of the Talbot effect. While there have been several proof-of-concept experiments showing the efficacy of this method, it is only recently that experiments to probe High Energy Density (HED) plasmas using Talbot–Lau interferometry are starting to take place. To improve these experimental designs, we present here the Talbot-Interferometry Analyzer (TIA) tool, a forward model for generating and postprocessing synthetic x-ray interferometry images from a Talbot–Lau interferometer. Although TIA can work with any two-dimensional hydrodynamic code to study plasma conditions as close to reality as possible, this software has been designed to work by default with output files from the hydrodynamic code FLASH, making the tool user-friendly and accessible to the general plasma physics community. The model has been built into a standalone app, which can be installed by anyone with access to the MATLAB runtime installer and is available upon request to the authors.
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Scholz, Gregor, Ling Yang, Markus Schake et Ines Fortmeier. « Concept for improving the form measurement results of aspheres and freeform surfaces in a tilted-wave interferometer ». Journal of Sensors and Sensor Systems 13, no 1 (15 mai 2024) : 89–97. http://dx.doi.org/10.5194/jsss-13-89-2024.
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Abstract. Accurate and flexible form measurements for aspherical and freeform surfaces are in high demand, and non-null-test interferometric methods such as tilted-wave interferometry have gained attention as a promising response to this need. Interferometric methods, however, display ambiguities between the measurement of certain form errors and the misalignment of the measured specimen. Therefore, improved knowledge of the absolute measurement position of the specimen in relation to the interferometer setup may improve the form measurement result. In this work, we propose a concept that uses a white light interferometer to measure the absolute distance between a transparent specimen's surface and the interferometer's objective and present preparatory data to qualify the white light interferometer for the improvement of tilted-wave interferometer measurements.
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Volkov, Petr, Andrey Lukyanov, Alexander Goryunov, Daniil Semikov et Oleg Vyazankin. « Low-Coherence Homodyne Interferometer for Sub-Megahertz Fiber Optic Sensor Readout ». Sensors 24, no 2 (16 janvier 2024) : 552. http://dx.doi.org/10.3390/s24020552.
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This study proposes a method for interferometric fiber optic sensor readouts. The method utilizes the advantages of the active homodyne demodulation technique and low-coherence interferometry. The usage of the tandem low-coherence interferometer enables modulating the reference interferometer without any changes to the sensor. This achieves high sensitivity, high stability, and a wide frequency band. A sensitivity of up to 0.1 nm (RMS) in the frequency range of 5 kHz is demonstrated by detecting acoustic signals with a fiber Michelson interferometer as a sensor.
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Thuering, T., et M. Stampanoni. « Performance and optimization of X-ray grating interferometry ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 372, no 2010 (6 mars 2014) : 20130027. http://dx.doi.org/10.1098/rsta.2013.0027.
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The monochromatic and polychromatic performance of a grating interferometer is theoretically analysed. The smallest detectable refraction angle is used as a metric for the efficiency in acquiring a differential phase-contrast image. Analytical formulae for the visibility and the smallest detectable refraction angle are derived for Talbot-type and Talbot–Lau-type interferometers, respectively, providing a framework for the optimization of the geometry. The polychromatic performance of a grating interferometer is investigated analytically by calculating the energy-dependent interference fringe visibility, the spectral acceptance and the polychromatic interference fringe visibility. The optimization of grating interferometry is a crucial step for the design of application-specific systems with maximum performance.
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Davis, John. « Stellar angular diameter measurements by interferometry ». Symposium - International Astronomical Union 189 (1997) : 31–38. http://dx.doi.org/10.1017/s0074180900116468.
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Stellar angular diameter measurements have been made with a range of interferometric techniques including speckle, aperture masking and long baseline optical/infrared interferometry. The current status of these measurements are summarised in terms of the range of spectral types and luminosity classes measured, the accuracies achieved, the wavelengths used for observations, and the reliability of the results. A number of major long-baseline interferometers are coming on-line, or are under development, and their potential is assessed in terms of wavelength cover, accuracy, angular resolution, and the range of spectral type and luminosity class cover.
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Kol'tso, N. E., S. A. Grenkov et L. V. Fedotov. « Comparison of Radio Interferometers with Analog and Digital Extraction of Recorded Signal ». Journal of the Russian Universities. Radioelectronics 23, no 2 (28 avril 2020) : 6–18. http://dx.doi.org/10.32603/1993-8985-2020-23-2-6-18.
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Introduction. Radio telescopes of Very Long Baseline Interferometry (VLBI) networks usually record several signals with relatively narrow (up to 32 MHz) bands, which are extracted by means of base band converters (BBC) from an analog noise signal of an intermediate frequency (IF) with bands up to 1 GHz. When processing data, frequency band synthesis is used. At new small radio telescopes (for example, RT-13), directly wideband IF signals are digitized. An ability to connect the RT-13 radio telescope to the “Quasar” VLBI complex and to international VLBI networks provides by a digital narrow-band signal extraction module developed in 2019.Aim. Determining the measuring accuracy of an interferometric group delay of a signal by a radio interferometer with a digital narrow-band signal extraction module and comparing the sensitivity of interferometers with analog and digital signal extraction systems.Materials and methods. Sensitivity losses of interferometers with different systems for detecting recorded signals were calculated. The accuracy of a multi-channel interferometer with the synthesis of a frequency band and of an interferometer with recording of digital broadband IF signals without band synthesis was compared. The results were confirmed by VLBI observations in the observatories of the “Quasar” complex.Results. When replacing the analog system of signal extraction with digital system the sensitivity losses of the interferometer were slightly reduced. The measurement accuracy of the interferometric group delay had not changed. Accuracy increased when digitally recording broadband IF signals and when synthesizing a frequency band significantly larger than the IF bandwidth. Conditions and minimum synthesized bands were determined under which the accuracy of the interferometer with the registration of narrowband signals can be higher than the accuracy of the interferometer with the registration of wideband IF signals.Conclusion. The problem of combining RT-13 radio telescopes with VLBI networks with recording of video frequency signals was solved. The efficiency of the installation of digital signal conversion systems at radio telescopes was shown.
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Zou, Yi-Quan, Ling-Na Wu, Qi Liu, Xin-Yu Luo, Shuai-Feng Guo, Jia-Hao Cao, Meng Khoon Tey et Li You. « Beating the classical precision limit with spin-1 Dicke states of more than 10,000 atoms ». Proceedings of the National Academy of Sciences 115, no 25 (1 juin 2018) : 6381–85. http://dx.doi.org/10.1073/pnas.1715105115.
Texte intégralRésumé :
Interferometry is a paradigm for most precision measurements. Using N uncorrelated particles, the achievable precision for a two-mode (two-path) interferometer is bounded by the standard quantum limit (SQL), 1/N, due to the discrete (quanta) nature of individual measurements. Despite being a challenging benchmark, the two-mode SQL has been approached in a number of systems, including the Laser Interferometer Gravitational-Wave Observatory and today’s best atomic clocks. For multimode interferometry, the SQL becomes 1/[(M−1)N] using M modes. Higher precision can also be achieved using entangled particles such that quantum noises from individual particles cancel out. In this work, we demonstrate an interferometric precision of 2.42−1.29+1.76 dB beyond the three-mode SQL, using balanced spin-1 (three-mode) Dicke states containing thousands of entangled atoms. The input quantum states are deterministically generated by controlled quantum phase transition and exhibit close to ideal quality. Our work shines light on the pursuit of quantum metrology beyond SQL.
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VETRANO, FLAVIO, GIANLUCA M. GUIDI, ANDREA VICERÉ, QUENTIN BODART, YU-HUNG LIEN, MARCO PREVEDELLI, GABRIELE ROSI, FIODOR SORRENTINO et GUGLIELMO M. TINO. « PRINCIPLES OF GRAVITATIONAL WAVES DETECTION THROUGH ATOM INTERFEROMETRY ». International Journal of Modern Physics : Conference Series 23 (janvier 2013) : 135–43. http://dx.doi.org/10.1142/s2010194513011185.
Texte intégralRésumé :
The output of a simple Mach-Zehnder atom interferometer (with light field beam splitters) is studied in order to obtain sensitivity curves for GW signals in the paraxial approximation by using the ABCD matrices techniques and first order perturbation theory for mirroratom interaction; order of magnitude of relevant physical parameters for a realistic GW detector through atom interferometry is deduced, both for single- and coupled-interferometers configurations. Finally a synthetic overview of ongoing activities of the Florence-Urbino group in this field is presented.
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Bedding, T. R., et J. G. Robertson. « Optical Aperture Synthesis with the Anglo-Australian Telescope ». Publications of the Astronomical Society of Australia 8, no 1 (1989) : 78–80. http://dx.doi.org/10.1017/s1323358000022967.
Texte intégralRésumé :
AbstractWe propose to construct an optical interferometer to produce high resolution images by aperture synthesis. The interferometer, known as the Masked Aperture Pupil-Plane Interference Telescope (MAPPIT), will be mounted at the coudé focus of the Anglo-Australian Telescope. It will use a non-redundant aperture mask, together with closure phase methods developed for radio VLBI, to overcome the wavefront distortions which are introduced by atmospheric turbulence. By using the techniques of pupil-plane interferometry and wavelength dispersion, it is hoped that MAPPIT will have more sensitivity than many other interferometric imaging projects.
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Haniff, Chris A. « High Angular Resolution Studies of Stellar Atmospheres ». Symposium - International Astronomical Union 205 (2001) : 288–95. http://dx.doi.org/10.1017/s0074180900221256.
Texte intégralRésumé :
The advent of long-baseline optical and infrared interferometers has meant that spatially resolved studies of stellar atmospheres have now become routinely possible. While prototype arrays, which have typically operated with short baselines and limited sensitivity, have produced exciting preliminary results, it is the development of larger dedicated facility arrays, such as the CHARA, Keck, and VLT interferometers, that offer the best prospects for advancing astrophysics. In this paper I review the possibilities and limitations of interferometric studies of stellar atmospheres, and highlight some recent results from optical/IR spatial interferometry.
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Hartkopf, William I. « Twenty Years of Speckle Interferometry ». International Astronomical Union Colloquium 135 (1992) : 459–68. http://dx.doi.org/10.1017/s0252921100006977.
Texte intégralRésumé :
The purpose of my talk is to briefly review the results of two decades of astrometric research using the technique of speckle interferometry. Although speckle, invented by Labeyrie in 1970 (Gezari et al. 1972), is the most well–known and widely–used interferometric technique in the visible and near infra-red, it neither the only technique in use, nor was it the first. Karl Schwarzschild made the first interferometric measurements of binary stars in 1895, using the then–new technique of Michelson interferometry and following a suggestion by Michelson himself that his technique was amenable to binary star astrometry. From 1919 to 1921, Anderson (1920) and Merrill (1922) made a series of measurements of Capella and other bright stars, using a Michelson interferometer of 20-foot baseline, mounted on the Mount Wilson 100-inch. These early measurements have definitely stood the test of time. Figure 1 shows a recently calculated orbit of Capella (Bagnuolo & Hartkopf 1989), using data spanning some 250 full revolutions. Anderson and Merrill’s measurements agree beautifully with observations made 7 decades later. As a result, Capella has probably the most accurately known orbit of any visual binary. Orbital elements calculated in 1981 (McAlister 1981) and again 10 years later differ in period by about 14 seconds, or less than 2 parts per million!
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Hou, X. X., G. M. Huang et Z. Zhao. « Extracting DEM from airborne X-band data based on PolInSAR ». ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-7/W4 (26 juin 2015) : 35–39. http://dx.doi.org/10.5194/isprsarchives-xl-7-w4-35-2015.
Texte intégralRésumé :
Polarimetric Interferometric Synthetic Aperture Radar (PolInSAR) is a new trend of SAR remote sensing technology which combined polarized multichannel information and Interferometric information. It is of great significance for extracting DEM in some regions with low precision of DEM such as vegetation coverage area and building concentrated area. In this paper we describe our experiments with high-resolution X-band full Polarimetric SAR data acquired by a dual-baseline interferometric airborne SAR system over an area of Danling in southern China. Pauli algorithm is used to generate the double polarimetric interferometry data, Singular Value Decomposition (SVD), Numerical Radius (NR) and Phase diversity (PD) methods are used to generate the full polarimetric interferometry data. Then we can make use of the polarimetric interferometric information to extract DEM with processing of pre filtering , image registration, image resampling, coherence optimization, multilook processing, flat-earth removal, interferogram filtering, phase unwrapping, parameter calibration, height derivation and geo-coding. The processing system named SARPlore has been exploited based on VC++ led by Chinese Academy of Surveying and Mapping. Finally compared optimization results with the single polarimetric interferometry, it has been observed that optimization ways can reduce the interferometric noise and the phase unwrapping residuals, and improve the precision of DEM. The result of full polarimetric interferometry is better than double polarimetric interferometry. Meanwhile, in different terrain, the result of full polarimetric interferometry will have a different degree of increase.
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Jankov, S. « Astronomical optical interferometry, II : Astrophysical results ». Serbian Astronomical Journal, no 183 (2011) : 1–35. http://dx.doi.org/10.2298/saj1183001j.
Texte intégralRésumé :
Optical interferometry is entering a new age with several ground- based long-baseline observatories now making observations of unprecedented spatial resolution. Based on a great leap forward in the quality and quantity of interferometric data, the astrophysical applications are not limited anymore to classical subjects, such as determination of fundamental properties of stars; namely, their effective temperatures, radii, luminosities and masses, but the present rapid development in this field allowed to move to a situation where optical interferometry is a general tool in studies of many astrophysical phenomena. Particularly, the advent of long-baseline interferometers making use of very large pupils has opened the way to faint objects science and first results on extragalactic objects have made it a reality. The first decade of XXI century is also remarkable for aperture synthesis in the visual and near-infrared wavelength regimes, which provided image reconstructions from stellar surfaces to Active Galactic Nuclei. Here I review the numerous astrophysical results obtained up to date, except for binary and multiple stars milliarcsecond astrometry, which should be a subject of an independent detailed review, taking into account its importance and expected results at microarcsecond precision level. To the results obtained with currently available interferometers, I associate the adopted instrumental settings in order to provide a guide for potential users concerning the appropriate instruments which can be used to obtain the desired astrophysical information.
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Chen, Zhenkai, Wenjing Zhou, Yingjie Yu, Vivi Tornari et Gilberto Artioli. « Defect Isolation from Whole to Local Field Separation in Complex Interferometry Fringe Patterns through Development of Weighted Least-Squares Algorithm ». Digital 4, no 1 (29 décembre 2023) : 104–13. http://dx.doi.org/10.3390/digital4010004.
Texte intégralRésumé :
In this paper, based on Gaussian 1σ-criterion and histogram segmentation, a weighted least-squares algorithm is applied and validated on digital holographic speckle pattern interferometric data to perform phase separation on the complex interference fields. The direct structural diagnosis tool is used to investigate defects and their impact on a complex antique wall painting of Giotto. The interferometry data is acquired with a portable off-axis interferometer set-up with a phase-shifted reference beam coupled with the object beam in front of the digital photosensitive medium. A digital holographic speckle pattern interferometry (DHSPI) system is used to register digital recordings of interferogram sequences over time. The surface is monitored for as long as it deforms prior to returning to its initial reference equilibrium state prior to excitation. The attempt to separate the whole vs. local defect complex amplitudes from the interferometric data is presented. The main aim is to achieve isolation and visualization of each defect’s impact amplitude in order to obtain detailed documentation of each defect and its structural impact on the surface for structural diagnosis purposes.
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Marklund, O., et L. Gustafsson. « Interferometry-based measurements of oil-film thickness ». Proceedings of the Institution of Mechanical Engineers, Part J : Journal of Engineering Tribology 215, no 3 (1 mars 2001) : 243–59. http://dx.doi.org/10.1243/1350650011543510.
Texte intégralRésumé :
Measurement of the thickness of thin lubricant films separating rotating surfaces in elastohydrodynamic experiments presents some challenging problems. The nature of the experimental apparatus inhibits the use of most commonly applied interferometric phase measurement methods. Also the absolute thickness of the separating film must be determined, as opposed to relative distances that would be sufficient in most other measurement scenarios where interferometry methods are used. In this paper, computer-based analysis of interferograms recorded using an elastohydrodynamic lubrication Fitzeu interferometer (a so-called ball-and-disc apparatus) is discussed, the main objective being to extract the absolute oil-film thickness. Intensity based methods (most importantly, calibration look-up procedures where colour parameters from recorded dynamic interferograms are compared with table values corresponding to known film thicknesses, but also a phase measurement approach based on multi-channel interferometry using trichromatic light) are described. A discussion regarding compensation for measurement errors due to the pressure dependence of the refractive index of the lubricant is also included.
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Sweedler, Jonathan V., Rafi D. Jalkian, Gary R. Sims et M. Bonner Denton. « Crossed Interferometric Dispersive Spectroscopy ». Applied Spectroscopy 44, no 1 (janvier 1990) : 14–20. http://dx.doi.org/10.1366/0003702904085967.
Texte intégralRésumé :
A novel design is described which combines dispersive and interferometric spectrometric instrumentation for ultraviolet visible spectroscopy, offering significant advantages in comparison to conventional spectroscopic configurations. The optical system incorporates the triangular common-path interferometer with an additional cross-dispersive element, allowing spectra to be obtained in a format compatible with rectangular CTD array detectors. The use of a cross-dispersive optical element reduces the distributive multiplex effects of interferometry in a rugged, compact, optically simple system.
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Simon, R. S., K. J. Johnston, D. Mozurkewich, K. W. Weiler, D. J. Hutter, J. T. Armstrong et T. S. Brackett. « Imaging Optical interferometry ». International Astronomical Union Colloquium 131 (1991) : 358–67. http://dx.doi.org/10.1017/s0252921100013646.
Texte intégralRésumé :
AbstractInterferometry at optical wavelengths is very similar to radio interferometry, once the fundamental differences in detectors are accounted for. The Mount Wilson Mark III optical interferometer has been used for optical interferometry of stars and stellar systems. Success with the Mark III has lead to the current program at the Naval Research Laboratory to build the Big Optical Array (BOA), which will be an imaging interferometer. Imaging simulations show that BOA will be able to produce images of complex stellar systems, with a resolution as fine as 0.2 milliarcseconds.
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Yang, Yichao, Kohei Yamamoto, Victor Huarcaya, Christoph Vorndamme, Daniel Penkert, Germán Fernández Barranco, Thomas S. Schwarze et al. « Single-Element Dual-Interferometer for Precision Inertial Sensing ». Sensors 20, no 17 (3 septembre 2020) : 4986. http://dx.doi.org/10.3390/s20174986.
Texte intégralRésumé :
Tracking moving masses in several degrees of freedom with high precision and large dynamic range is a central aspect in many current and future gravitational physics experiments. Laser interferometers have been established as one of the tools of choice for such measurement schemes. Using sinusoidal phase modulation homodyne interferometry allows a drastic reduction of the complexity of the optical setup, a key limitation of multi-channel interferometry. By shifting the complexity of the setup to the signal processing stage, these methods enable devices with a size and weight not feasible using conventional techniques. In this paper we present the design of a novel sensor topology based on deep frequency modulation interferometry: the self-referenced single-element dual-interferometer (SEDI) inertial sensor, which takes simplification one step further by accommodating two interferometers in one optic. Using a combination of computer models and analytical methods we show that an inertial sensor with sub-picometer precision for frequencies above 10 mHz, in a package of a few cubic inches, seems feasible with our approach. Moreover we show that by combining two of these devices it is possible to reach sub-picometer precision down to 2 mHz. In combination with the given compactness, this makes the SEDI sensor a promising approach for applications in high precision inertial sensing for both next-generation space-based gravity missions employing drag-free control, and ground-based experiments employing inertial isolation systems with optical readout.
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Fiorucci, D., A. Fassina et M. La Matina. « Feasibility study of an enhanced heterodyne dispersion interferometer ». Journal of Instrumentation 18, no 02 (1 février 2023) : C02057. http://dx.doi.org/10.1088/1748-0221/18/02/c02057.
Texte intégralRésumé :
Abstract Interferometry is the commonly exploited technique for electron density measurements in magnetically confined fusion plasma experiments. Reliable electron density measurements are fundamental both for machine protection and for plasma physics understanding. In the last years, attention was drawn on the dispersion interferometer concept, because of its robustness and simplicity. Nevertheless, the heterodyne version of this configuration, which has several advantages over the homodyne scheme, loses one of the main benefits of the dispersion interferometer technique, that is its inherent insensitivity to vibration errors. In this paper, two methods are proposed and theoretically investigated to reduce the vibration noise in the electron density measurements performed with heterodyne dispersion interferometers.
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Armstrong, J. T. « Sub-Milliarcsecond Optical Astrometry and Binary Stars ». Symposium - International Astronomical Union 166 (1995) : 193–202. http://dx.doi.org/10.1017/s0074180900228064.
Texte intégralRésumé :
Long-baseline optical interferometry has made it possible to measure the visual orbits of binary stars with major axes as small as 5 mas and errors of ≲ 100 μas. Interferometers now nearing completion will extend these values to ≳ 500 μas and σa ∼ 10 μas. Observations of double-lined spectroscopic binaries with current interferometers have already yielded some mass estimates with precisions rivaling those from fitting the light curves of eclipsing double-lined systems. Luminosity estimates based on combined visual interferometric observations and velocity curves are often more precise than those from more indirect methods based on estimates of Teff. New interferometers now coming into operation will make it possible to measure fundamental parameters in dozens to hundreds of binary systems.
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Kolkiran, Aziz. « High-NOON States with High Flux of Photons Using Coherent Beam Stimulated Noncollinear Parametric Down Conversion ». International Journal of Optics 2019 (30 décembre 2019) : 1–7. http://dx.doi.org/10.1155/2019/6871979.
Texte intégralRésumé :
We show how to reach high fidelity NOON states with a high count rate inside optical interferometers. Previously, it has been shown that by mixing squeezed and coherent light at a beam splitter, it is possible to generate NOON states of arbitrary N with a fidelity as high as 94%. The scheme is based on higher-order interference between “quantum” down-converted light and “classical” coherent light. However, this requires optimizing the amplitude ratio of classical to quantum light, thereby limiting the overall count rate for the interferometric super-resolution signal. We propose using coherent beam stimulated noncollinear two-mode down-converted light as input to the interferometer. Our scheme is based on the stimulation of noncollinear parametric down conversion by coherent light sources. We get a better flexibility of choosing the amplitude ratio in generating NOON states. This enables super-resolution intensity exceeding the previous scheme by many orders of magnitude. Therefore, we hope to improve the magnitude of N-fold super-resolution in quantum interferometry for arbitrary N using bright light sources. We give improved results for N = 4 and 5.
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Kovačević, Andjelka B., Yu-Yang Songsheng, Jian-Min Wang et Luka Č. Popović. « Probing the elliptical orbital configuration of the close binary of supermassive black holes with differential interferometry ». Astronomy & ; Astrophysics 644 (décembre 2020) : A88. http://dx.doi.org/10.1051/0004-6361/202038733.
Texte intégralRésumé :
Context. Obtaining detections of electromagnetic signatures from the close binaries of supermassive black holes (CB-SMBH) is still a great observational challenge. The Very Large Telescope Interferometer (VLTI) and the Extremely Large Telescope (ELT) will serve as a robust astrophysics suite offering the opportunity to probe the structure and dynamics of CB-SMBH at a high spectral and angular resolution. Aims. Here, we explore and illustrate the application of differential interferometry on unresolved CB-SMBH systems in elliptical orbital configurations. We also investigate certain peculiarities of interferometry signals for a single SMBH with clouds in elliptical orbital motion. Methods. Photocentre displacements between each SMBH and the regions in their disc-like broad line regions (BLR) appear as small interferometric differential phase variability. To investigate the application of interferometric phases for the detection of CB-SMBH systems, we simulated a series of differential interferometry signatures, based on our model comprising ensembles of clouds surrounding each supermassive black hole in a CB-SMBH. By setting the model to the parameters of a single SMBH with elliptical cloud motion, we also calculated a series of differential interferometry observables for this case. Results. We found various deviations from the canonical S-shape of the CB-SMBH phase profile for elliptically configured CB-SMBH systems. The amplitude and specific shape of the interferometry observables depend on the orbital configurations of the CB-SMBH system. We get distinctive results when considering anti-aligned angular momenta of cloud orbits with regard to the total CB-SMBH angular momentum. We also show that their velocity distributions differ from the aligned cloud orbital motion. Some simulated spectral lines from our model closely resemble observations from the Paα line obtained from near-infrared AGN surveys. We found differences between the “zoo” of differential phases of single SMBH and CB-SMBH systems. The “zoo” of differential phases for a single SMBH take a deformed S shape. We also show how their differential phase shape, amplitude, and slope evolve with various sets of cloud orbital parameters and the observer’s position. Conclusions. We calculate an extensive atlas of the interferometric observables, revealing distinctive signatures for the elliptical configuration CB-SMBH. We also provide an interferometry atlas for the case of a single SMBH with clouds with an elliptical motion, which differs from those of a CB-SMBH. These maps can be useful for extracting exceptional features of the BLR structure from future high-resolution observations of CB-SMBH systems, but also of a single SMBH with clouds in an elliptical orbital setup.
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Hoque, Nabil Md Rakinul, et Lingze Duan. « Impact of Soil-Based Insulation on Ultrahigh-Resolution Fiber-Optic Interferometry ». Sensors 23, no 1 (27 décembre 2022) : 259. http://dx.doi.org/10.3390/s23010259.
Texte intégralRésumé :
High resolution optical interferometry often requires thermal and acoustic insultation to reduce and remove environment-induced fluctuations. Broader applications of interferometric optical sensors in the future call for low-cost materials with both low thermal diffusivity and good soundproofing capability. In this paper, we explore the feasibility and effectiveness of natural soil as an insulation material for ultrahigh-resolution fiber-optic interferometry. An insulation chamber surrounded by soil is constructed, and its impact on the noise reduction of a Mach-Zehnder Fabry-Perot hybrid fiber interferometer is evaluated. Our results indicate that soil can effectively reduce ambient noise across a broad frequency range. Moreover, compared to conventional insulation materials such as polyurethane foam, soil shows superior insulation performance at low frequencies and thereby affords better long-term stability. This work demonstrates the practicability of soil as a legitimate option of insulation material for precision optical experiments.
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Crosetto, M., O. Monserrat, N. Devanthéry, M. Cuevas-González, A. Barra et B. Crippa. « PERSISTENT SCATTERER INTERFEROMETRY USING SENTINEL-1 DATA ». ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (22 juin 2016) : 835–39. http://dx.doi.org/10.5194/isprs-archives-xli-b7-835-2016.
Texte intégralRésumé :
This paper is focused on deformation monitoring using a Persistent Scatterer Interferometry technique and the interferometric SAR data acquired by the Sentinel-1 satellite of the European Space Agency. The first part of the paper describes the procedure used to process and analyze Sentinel-1 interferometric SAR data. Two main approaches are described. The first one is a simplified Persistent Scatterer Interferometry approach that exploits two key properties of the Sentinel-1 data: the high coherence of the 12-day interferograms and the reduced orbital tube. The second approach is a full Persistent Scatterer Interferometry approach, where a more sophisticate data treatment is employed. The second part of the paper illustrates the results obtained with the two processing approaches. Two case studies are described. The first one concerns landslide detection and monitoring. In this case, the simplified Persistent Scatterer Interferometry approach was used. The second one regards the deformation monitoring of an urban area. In this case, a full Persistent Scatterer Interferometry approach was used.
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Crosetto, M., O. Monserrat, N. Devanthéry, M. Cuevas-González, A. Barra et B. Crippa. « PERSISTENT SCATTERER INTERFEROMETRY USING SENTINEL-1 DATA ». ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (22 juin 2016) : 835–39. http://dx.doi.org/10.5194/isprsarchives-xli-b7-835-2016.
Texte intégralRésumé :
This paper is focused on deformation monitoring using a Persistent Scatterer Interferometry technique and the interferometric SAR data acquired by the Sentinel-1 satellite of the European Space Agency. The first part of the paper describes the procedure used to process and analyze Sentinel-1 interferometric SAR data. Two main approaches are described. The first one is a simplified Persistent Scatterer Interferometry approach that exploits two key properties of the Sentinel-1 data: the high coherence of the 12-day interferograms and the reduced orbital tube. The second approach is a full Persistent Scatterer Interferometry approach, where a more sophisticate data treatment is employed. The second part of the paper illustrates the results obtained with the two processing approaches. Two case studies are described. The first one concerns landslide detection and monitoring. In this case, the simplified Persistent Scatterer Interferometry approach was used. The second one regards the deformation monitoring of an urban area. In this case, a full Persistent Scatterer Interferometry approach was used.
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Pringkasemchai, A., J. Wongsaroj et K. Mongkolsuttirat. « Determination of phase change correction on gauge block measurement in two different interferometric measurement systems ». Journal of Physics : Conference Series 2431, no 1 (1 janvier 2023) : 012012. http://dx.doi.org/10.1088/1742-6596/2431/1/012012.
Texte intégralRésumé :
Abstract Phase change correction (PCC) is an important correction value of the end effect in an optical interferometry system. Normally, this value is used to compensate for gauge block measurement by an optical interferometry system based on ISO 3650:1998. Two different interferometric measurement systems in terms of fringe fraction measurement were performed to determine the phase change correction by a five-stacking method. These results are used to determine the length measurement of gauge blocks in an optical interferometer technique and consequently, to evaluate the uncertainty of gauge blocks measurement. The preliminary results for steel gauge block are shown that the value of phase change correction in a phase shift gauge block interferometer (PSGBI) system and a standard uncertainty are 35.2 nm and 5.8 nm, respectively. In contrast, the values from an average slits gauge block interferometer (ASGBI) system and a standard uncertainty are 66.0 nm and 6.0 nm, respectively. We found that the phase correction from the PSGBI system is lower than ASGBI about 0.53 - 0.56 times because the different of wave front correction in two interferometric systems. However, the lengths of gauge blocks of all materials measured by the two systems were consistent as assessed by En number. According to the study, we can conclude that phase change correction is based on the characteristics of each GBI system, surface texture characteristic in term of wringing condition and material types of gauge block and optical plates such as the fringe fraction measurement technique, and wave front error compensation. Consequently, measurements that require a high accuracy should determine the phase change correction before each measurement due to this value is not interchangeable.
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McAlister, H. A. « The Potential of Long–Baseline Optical Interferometry of Binary Stars ». International Astronomical Union Colloquium 135 (1992) : 527–35. http://dx.doi.org/10.1017/s0252921100007053.
Texte intégralRésumé :
AbstractInterferometric arrays possessing sub-milliarcsecond resolution are either about to be fully scientifically productive, as in the case of the Sydney University Stellar Interferometer, or are under various stages of planning and development. The 1990’s will thus witness a hundred–fold gain in resolution over speckle interferometry at the largest telescopes and 5,000 times the resolution of classical direct imaging. Where speckle interferometry can now resolve binary stars with periods of 1 to 2 years, interferometric arrays with baselines of hundreds of meters will resolve binaries with periods of a few hours. Arrays will resolve the majority of the known spectroscopic binaries, providing a substantial increase in the quantity and quality of stellar mass determinations. Surveys for new binaries among the field stars and other restricted samples will be accomplished with unprecedented completeness. The remarkable enhancement in resolution we are about to witness from facilities like SUSI and our own proposed CHARA Array will quite literally revolutionize the field of double and multiple star research.
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Vasconcelos, Ivan, Roel Snieder et Brian Hornby. « Imaging internal multiples from subsalt VSP data — Examples of target-oriented interferometry ». GEOPHYSICS 73, no 4 (juillet 2008) : S157—S168. http://dx.doi.org/10.1190/1.2944168.
Texte intégralRésumé :
Seismic interferometry has become a technology of growing interest for imaging borehole seismic data. We demonstrate that interferometry of internal multiples can be used to image targets above a borehole receiver array. By internal multiples, we refer to all types of waves that scatter multiple times inside the model. These include, for instance, interbed, intrasalt, and water-bottom multiples as well as conversions among them. We use an interferometry technique that is based on representation theorems for perturbed media and targets the reconstruction of specific primary reflections from multiply reflected waves. In this interferometry approach, we rely on shot-domain wavenumber separation to select the directions of waves arriving at a given receiver. Using a numerical walkaway (WAW) VSP experiment recorded by a subsalt borehole receiver array in the Sigsbee salt model, we use the interference of internal multiples to image the salt structure from below. In this numerical example, the interferometric image that uses internal multiples reconstructs the bottom- and top-of-salt reflectors above the receiver array as well as the subsalt sediment structure between the array and the salt. Because of the limited source summation in this interferometry example, the interferometric images show artifact reflectors within the salt body. We apply this method to a field walkaway VSP from the Gulf of Mexico. With the field data, we demonstrate that the choice of shot-domain wavenumbers in the target-oriented interferometry procedure controls the wavenumbers in the output pseudoshot gathers. Target-oriented interferometric imaging from the 20-receiver array recovers the top-of-salt reflector that is consistent with surface seismic images. We present our results with both correlation-based and deconvolution-based interferometry.
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Zhao, Ya, Zhi Wang, Yupeng Li, Chao Fang, Heshan Liu et Huilong Gao. « Method to Remove Tilt-to-Length Coupling Caused by Interference of Flat-Top Beam and Gaussian Beam ». Applied Sciences 9, no 19 (1 octobre 2019) : 4112. http://dx.doi.org/10.3390/app9194112.
Texte intégralRésumé :
We discuss the tilt-to-length (TTL) coupling noise caused by interference between a flat-top beam and a Gaussian beam. Several physical models are presented to research the effects of non-diffracted and diffracted beams on TTL noise. A special case that can remove TTL coupling noise is discovered and is verified via both theoretical analysis and numerical simulations. The proposed case could provide desirable suggestions for the construction of high-precision interferometers such as the Laser Interferometer Space Antenna (LISA), Taiji program, or other interferometry systems.
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Xiao, Longfei, Hengfei Wang, Canhua Xu et Yantang Huang. « Research the Nonlinear Frequency Modulation of Tunable Light Source to Improve the Spatial Resolution of OFDR ». Journal of Physics : Conference Series 2464, no 1 (1 mars 2023) : 012015. http://dx.doi.org/10.1088/1742-6596/2464/1/012015.
Texte intégralRésumé :
Abstract The main factor affecting the optical fiber spatial resolution of OFDR system is the non-linearity of laser frequency tuning.We demonstrated a M-Z interferometry and performed nonlinear measurements at different frequencies. The main and auxiliary interferometers with tunable laser source(TLS) were built, and the auxiliary interferometer was used to correct the nonlinearity modulation of the frequecny of the main laser.The interpolation compensation scheme was proposed.The research results of the nonlinear frequency modulation of TLS to improve the spatial resolution of optical fiber vibration sensing was demonstrated,the spatial resolution is 0.17m.