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Topic: Interferometry

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	Nikon MicroscopyU: Principles and Applications of Multiple-Beam Interferometry
		The technique of multiple-beam interferometry is based upon situating two surfaces of high reflectivity in close proximity and using a lens to converge beams which have undergone multiple-reflection between the surfaces.
		When the optimal conditions are satisfied, the breadth of the fringes in multiple-beam interferometry is on the order of 1/50 of the corresponding breadth in the two-beam method, and hence the precision is improved by a factor of approximately 50.
		As in the case of two-beam interferometry, the pattern must be adjusted so that the fringes appear perpendicular to the step to be measured, and the dispersion of the fringes is also adjusted.
	www.microscopyu.com /articles/interferometry/multibeam.html (2638 words)

	Interferometry - Wikipedia, the free encyclopedia
		Interferometry is the science of combining (interfering) two or more waves, which creates an output wave different from the input waves; this in turn can be used to explore the nature of the input waves.
		A famous use of white light interferometry is the precise measurement of geodetic standard baselines as invented by Yrjö Väisälä.
		More modern geodetic applications of laser interferometry are in calibrating the divisions on levelling staffs, and in monitoring the free fall of a reflective prism within a ballistic or absolute gravimeter, allowing determination of gravity, i.e., the acceleration of free fall, directly from the physical definition at a few parts in a billion accuracy.
	en.wikipedia.org /wiki/Interferometry (2422 words)

	Very Long Baseline Interferometry - Wikipedia, the free encyclopedia
		Very Long Baseline Interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy, in which the data received at each antenna in the array is paired with timing information, usually from a local atomic clock, and then stored for later analysis on magnetic tape or hard disk.
		The resolution achievable using interferometry is proportional to the distance between the antennas furthest apart in the array.
		In VLBI interferometry, the data are usually recorded at each of the telescopes (in the past this was done on large magnetic tapes, but nowadays it is usually done on large RAID arrays of computer disk drives).
	en.wikipedia.org /wiki/Very_Long_Baseline_Interferometry (1392 words)

	SPACE.com -- Interferometry 101: How light is combined from multiple telescopes
		The terms "interferometry'' and "interferometer'' are both derived from the word interference.
		Interferometry is the use of interference phenomena for measurement purposes, either for very small angles or for tiny distance increments (the displacement of two objects relative to one another).
		In astronomical interferometry, the most important parameter is the "baseline," the distance between the flat mirrors.
	www.space.com /scienceastronomy/astronomy/interferometry_101.html (1166 words)

	Accordion Fringe Interferometry (Site not responding. Last check: 2007-10-18)
		1) " Accordion" -- As to Accordion Fringe Interferometry
		3) " Interferometry" -- As to Accordion Fringe Interferometry
		Interferometry is the applied science of combining two or more input points of a particular data type, such as optical measurements, to form a greater picture based on the combination of the two sources.In astronomy (such as with the Keck telescopes), this is used to "combine" two telescopes.
	www.eurostudent.net /info/34923-accordion-fringe-interferometry.html (923 words)

	Radar Interferometry (Site not responding. Last check: 2007-10-18)
		Radar interferometry is a technique where radar data, usually recorded from satellite, are used to map the elevation (topography) or the deformation of the ground - such as in earthquakes.
		Interferometry is applied to accurately map the speed of this glacier and the method is described briefly below.
		First we use differential interferometry, and then the horizontal and vertical surface-velocities are calculated from the remaining fringes, the geometry of the satellite orbits and the glacier topography.
	www.antarctica.ac.uk /BAS_Science/Techniques/Interferometry/index.html (608 words)

	NIST: Quantum Metrology Group - X-ray Interferometry (Site not responding. Last check: 2007-10-18)
		X-ray interferometry uses the interference of two x-ray beams to precisely measure optical constants, or (by moving components of the interferometer) to measure displacement with picometer precision.
		An introduction to the terminology and physics of x-ray interferometry is given in the first part of this overview, followed by a brief discussion of the historical background of the technique.
		X-ray interferometry (XRI) was invented by Bonse and Hart at Cornell University in 1965 [1].
	physics.nist.gov /Divisions/Div842/Gp5/admd.html (1280 words)

	* Interferometry - (Astronomy): Definition
		In radio interferometry, a complex-valued un-normalized measure of the coherence function of the arriving radiation, modified by the characteristics of the interferometer's antennas.
		They plan to use the method of nulling interferometry -- combining the signal from a number of different telescopes in such a way that the light from the central star is cancelled out -- will be used to reveal dim planets.
		Interferometry = combine light from several dishes to produce an image with resolution defined by separation of dishes, not dish size.
	en.mimi.hu /astronomy/interferometry.html (660 words)

	Taking the measure of the stars - optical interferometry Science News - Find Articles (Site not responding. Last check: 2007-10-18)
		Interferometry began as a technique inoptical laboratories, using visible light, but its most widespread use in astronomy so far has been in the radio range.
		This produces what we see as stellar twinkling, and it destroys the correlations on which interferometry depends unless the two receivers are under the same isoplanatic patch, the area in which the atmospheric refraction changes uniformly.
		In the century and a half since interferometry was developed in the laboratory, astronomers working with visible light have not been able to utilize it to any great extent.
	www.findarticles.com /p/articles/mi_m1200/is_v131/ai_4610623 (939 words)

	Optical Interferometry (Site not responding. Last check: 2007-10-18)
		Optical Interferometry is the technique of coherently combining light from widely spaced telescopes to acheive the resolution of one with size equal to the telescope spacing.
		Interferometry is common at radio wavelengths; perhaps the best-known example is the Very Large Array, or VLA.
		Interferometry is a challeging observational technique at optical wavelengths for a number of reasons.
	www.mit.edu /~matthew1/oi/oi.html (310 words)

	Interferometry (Site not responding. Last check: 2007-10-18)
		Although interferometry has been standard practice at radio wavelengths for decades, it has only recently seen widespread and successful application at optical and infra-red wavelengths.
		Interferometry is quite useful for providing direct measurements of stellar diameters.
		Another use of interferometry is in resolving the orbits of spectroscopic binary stars.
	space.mit.edu /home/blane/Interferometry.html (433 words)

	Multiple Images SAR Interferometry (Site not responding. Last check: 2007-10-18)
		The Death Sea area was selected because of the absence of vegetation cover, its climate stability, its geologically favourable relief and an interesting tectonic context, related to the presence of a strike slip fault area and to the forming of pull-apart bassins.
		Four-images SAR interferometry makes use of two independent interferometric pairs: one containing a topographic phase as well as the displacement component that we want to measure, and a second interferometric pair which is supposed to contain only a topographic phase component in order to be used as reference.
		Four images SAR interferometry is similar in its principle to the method developped by JPL since it uses a SAR interferogram to generate the phase component due to the topography.
	earth.esa.int /workshops/fringe_1996/derauw (3294 words)

	Opticon - Interferometry
		The objective of the Interferometry Forum is to bring optical interferometry to main stream astronomy and enable the Candidate Countries of central Europe to participate fully in technical and scientific developments in optical interferometry.
		Interferometry – the combination of multiple telescopes in a single coherent array – is a powerful technique that allows astronomers to obtain unprecedented angular resolution and to measure motions of celestial bodies with extreme precision.
		European Exchange Visitors Programme in Optical Interferometry: Funding (travel and accommodation) will be made available for visits of researchers from one of the participants to an institute of his/her choice (but within the European Community) to perform collaborative work on one of the active topics of the European Interferometry Initiative.
	www.astro-opticon.org /networking/interferometry.html (382 words)

	Optical Interferometry -- from Eric Weisstein's World of Physics
		It is technologically more challenging than radio interferometry because it detects individual photons and requires extreme mechanical precision because of the short wavelengths involved.
		Additional technological challenges include the lack of coherent broadband amplifiers the visible and the fact that, except using a CO laser in the infrared, signals cannot be mixed to an intermediate frequency.
		Three type of optical interferometry which do not make use of masks are speckle interferometry, Knox-Thompson interferometry, and bispectrum analysis.
	scienceworld.wolfram.com /physics/OpticalInterferometry.html (325 words)

	Interferometry - Free net encyclopedia (Site not responding. Last check: 2007-10-18)
		Interferometry is the applied science of combining two or more waves, which are said to interfere with each other.
		Although the wave phenomenon of interference is very general, in applications the word interferometry is used for a small number of specialist niches, including optical metrology, studies of quantum mechanics such as neutron interferometry and amongst astronomers as described below.
		The chief benefit of low-coherence interferometry is that it does not suffer from the $2 \pi$ ambiguity of coherent interferometry, and is therefore suited to profiling steps and rough surfaces.
	www.netipedia.com /index.php/Interferometry (1941 words)

	Aperture synthesis (interferometry)
		Interferometry is an extremely clever way of overcoming the limited angular resolution of telescopes, which is caused by the so-called "diffraction" of light.
		The basics of interferometry can be presented based on experiments with optical light, because the rules of behaviour are the same for light all across the electromagnetic spectrum.
		Recently the development of optical/near-infrared interferometry has started and first successes have been achieved, opening a second extremely high resolution observing window to the sky.
	www.atnf.csiro.au /people/mdahlem/pop/tech/synth.html (2199 words)

	Optical Interferometry
		Radio interferometry has been an important and widely used tool in astronomy, as evidenced by the VLA, the VLBA and other long baseline arrays of radio interferometers through out the world.
		Interferometry uses the constructive and destructive interference of radiation to determine the spatial properties of the source of the radiation.
		Rather, it increases the sensitivity of the interferometry by restoring the coherence of the incoming light over the individual elements of the interferometer.
	www.pha.jhu.edu /~jlotz/aoptics/node5.html (537 words)

	Interferometry (Site not responding. Last check: 2007-10-18)
		Interferometry is the study of interference patterns created by combining two sets of radar signals.
		If you've ever seen a puddle of water with a film of oil on it, you've probably noticed bands of color on the surface.
		Using the information about the distance between the two antennas and the differences in the reflected radar wave signals, accurate elevation of the Earth's surface can be calculated.
	srtm.usgs.gov /data/interferometry.html (352 words)

	Nikon MicroscopyU: Principles and Applications of Two-Beam Interferometry
		Among the various forms of interferometry, two-beam interferometry is especially simple and straightforward in principle, as well as practice, and is therefore utilized for a broad range of applications.
		In optical interferometry, this reference plane is known as the reference plate (or reference mirror).
		Using white light to examine the surface of a convex object, the interference fringes are arrayed in increasing order from the vicinity of the reference plate (reference mirror) toward the periphery of the object.
	www.microscopyu.com /articles/interferometry/twobeam.html (4216 words)

	Re: can sonic interferometry provide an acoustic 'image'?
		Interferometry, as you have probably learned in class, is the use of interfering waves from two different coherent signal sources to determine something about an object.
		The important thing to remember about interferometry is that it requires two sources that are coherent, meaning that they are operating at the same frequency and that they are synchronized.
		Be sure not to confuse interferometry with acoustic imaging, which is used in SONAR and in medical ultrasound, as well as other applications and does, indeed, use such arrays of microphones.
	www.madsci.org /posts/archives/2000-03/953650598.Ph.r.html (418 words)

	Interferometry Showcase (Site not responding. Last check: 2007-10-18)
		INSI : SAR Interferometry (INSAR) is a hot topic which is rapidly evolving thanks to spectacular results achieved in fields such as monitoring of earthquakes and volcanoes, land subsidence, glacier dynamics, classification of different land types and construction of Digital Elevation Models (DEM's) of the Earth's surface.
		Interferometry: scientific background, applications and reference documentation : After one year of ERS-1 and ERS-2 performing repeat acquisitions with a one day separation (the so-called tandem acquisition phase) there are around 100 000 repeated frames of data covering areas all over the world.
		ERS-1 and 2 Interferometry Baseline Listing : It has been demonstrated that Synthetic Aperture Radar (SAR) Interferometry or INSAR is a significant potential application of ERS-1 SAR data, using the baseline listings, users can identify those repeat orbit combinations which satisfy the INSAR baseline criterion and are thus appropriate for various applications.
	earth.esa.int /applications/interferometry.html (229 words)

	Astronomical interferometry,from the visible to sub-mm waves
		Interferometry has been used to infer the distance of a nova explosion, and of Galactic Cepheid stars.
		These facilities will broaden the scope of optical and infrared interferometry by providing sufficient sensitivity to observe rather faint stars and even some extragalactic objects, by offering a suite of beam combiners and detectors covering a wide wavelength range, and by making a fairly complicated technique more accessible to a broad users’ community.
		There are now a number of mm-wave interferometers that perform imaging of continuum and line emission of objects as varied as nearby star-forming regions and distant galaxies in the young universe, with a spatial resolution of about 1 arc second.
	www.europhysicsnews.com /full/12/article13/article13.html (2194 words)

	English Interferometry
		Interferometry is the science of combining two or more waves, which are said to interfere with each other.
		Although the wave phenomenon of interference is very general, in applications the word interferometry is used for a small number of specialist niches, including optical metrology, studies of quantum mechanics such as neutron interferometry and neutrino interferometry and string theory interferometry amongst astronomers as described below.
		In astronomy (such as with the Keck telescopes), this is used to combine light from two or more telescopes to obtain measurements with higher resolution than could be obtained with either telescopes individually.
	www.dejavu.org /cgi-bin/get.cgi?ver=93&url=http%3A%2F%2Farticles.gourt.com%2F%3Farticle%3Dinterferometry%26type%3Den (1939 words)

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