Search results for "interferometry"
showing 10 items of 343 documents
Strongly decelerated expansion of SN 1979C
2002
We observed SN1979C in M100 on 4 June 1999, about twenty years after explosion, with a very sensitive four-antenna VLBI array at the wavelength of 18cm. The distance to M100 and the expansion velocities are such that the supernova cannot be fully resolved by our Earth-wide array. Model-dependent sizes for the source have been determined and compared with previous results. We conclude that the supernova shock was initially in free expansion for 6 +/- 2 yrs and then experienced a very strong deceleration. The onset of deceleration took place a few years before the abrupt trend change in the integrated radio flux density curves. We estimate the shocked swept-up mass to be about 1.6 solar masse…
Landslide Impacts on Agrigento’s Cathedral Imaged with Radar Interferometry
2013
ERS1/2 (1992–2000), ENVISAT (2002–2008) and RADARSAT1 (2003–2007) satellite data, processed with Persistent Scatterer Interferometry, are exploited to study the historic urban area of Agrigento, Italy, whose structural stability is threatened by retrogressive landslide processes. Up to 2–5mm/year of line-of-sight displacement are observed in 1992–2008 on the staircase and the left aisle of the Cathedral. Displacement acceleration to 13–15mm/year is measured in July 2006–May 2007, in the northern portion of the churchyard, in front of the left aisle. The areas moving at higher rates, located at the edge of the NW slope of Girgenti hill, correspond to those showing major structural damages. A…
A simple technique for measurement of corneal thickness.
1998
Measurement of corneal thickness has potential benefit both in the fitting of contact lenses and in monitoring any pathology that could affect corneal thickness. Corneal thickness measurement is undertaken using an accessory to the biomicroscope, the optical pachometer, or by means of expensive apparatus such as the ultrasonic pachometer. There are other complex methods, such as laser Doppler interferometry, or ultrasonic rasters of the cornea. In this study, an easier and low cost method, based on the measurement of the optical section formed of the cornea by the biomicroscope illumination system, is proposed. The advantages of this new method are the simplicity of its experimental set-up …
Agreement of predicted intraocular lens power using swept-source optical coherence tomography and partial coherence interferometry
2021
PURPOSE To analyze the agreement of the predicted intraocular lens (IOL) power obtained with ANTERION, IOLMaster 700 and Pentacam AXL biometers. METHODS We calculated the monofocal and trifocal IOL power using the SRK/T, Haigis, Barrett Universal II and Hoffer Q formulas for 106 eyes. IOL power agreement between devices was evaluated using the Bland-Altman method. RESULTS We found significant differences between biometers comparisons (p 0.05), with the same outcomes for medium- and long-eyes. No significant differences were found using the SRK/T, Haigis, or Hoffer Q formulas for short-eyes (p > 0.1). However, Barrett Universal II formula produced significant differences (p < 0.05) and thes…
Graphic representation of data resulting from measurement comparison trials in cataract and refractive surgery.
2003
* BACKGROUND AND OBJECTIVES: The evaluation of new diagnostic measurement devices allows intraindividual comparison with an established standard method. However, reports in journal articles often omit the adequate incorporation of the intraindividual design into the graphic representation. * PATIENTS AND METHODS: This article illustrates the drawbacks and the possible erroneous conclusions caused by this misleading practice in terms of recent method comparison data resulting from axial length measurement in 220 consecutive patients by both applanation ultrasound and partial coherence interferometry. * RESULTS: Graphic representation of such method comparison data should be based on boxplots…
Dynamic laser speckle analyzed considering inhomogeneities in the biological sample
2017
Dynamic laser speckle phenomenon allows a contactless and nondestructive way to monitor biological changes that are quantified by second-order statistics applied in the images in time using a secondary matrix known as time history of the speckle pattern (THSP). To avoid being time consuming, the traditional way to build the THSP restricts the data to a line or column. Our hypothesis is that the spatial restriction of the information could compromise the results, particularly when undesirable and unexpected optical inhomogeneities occur, such as in cell culture media. It tested a spatial random approach to collect the points to form a THSP. Cells in a culture medium and in drying paint, repr…
Spatially multiplexed interferometric microscopy with partially coherent illumination
2016
We have recently reported on a simple, low cost, and highly stable way to convert a standard microscope into a holographic one [Opt. Express 22, 14929 (2014)]. The method, named spatially multiplexed interferometric microscopy (SMIM), proposes an off-axis holographic architecture implemented onto a regular (nonholographic) microscope with minimum modifications: the use of coherent illumination and a properly placed and selected one-dimensional diffraction grating. In this contribution, we report on the implementation of partially (temporally reduced) coherent illumination in SMIM as a way to improve quantitative phase imaging. The use of low coherence sources forces the application of phase…
Correlation between type 2 diabetes, dry eye and Meibomian glands dysfunction
2019
espanolObjetivo Evaluar las glandulas de Meibomio, la superficie ocular y la funcion de la lagrima en pacientes con diabetes tipo 2, y estudiar la correlacion entre estas situaciones. Metodos Estudio prospectivo de 76 varones, 37 de ellos con diabetes tipo 2, con una media de duracion de entre 7±5 anos, y 36 mujeres como grupo control. Tras completar el cuestionario del indice de enfermedad de la superficie ocular (OSDI), se obtuvieron el tiempo de ruptura lagrimal no invasivo (NIBUT) y el patron de la capa lipidica de la lagrima utilizando interferometria y altura del menisco lagrimal/AML. Se estudio la superficie ocular con tincion verde de lisamina y la morfologia de las glandulas con ev…
ALD thin ZnO layer as an active medium in a fiber-optic Fabry–Perot interferometer
2015
Abstract A novel optical fiber sensor of temperature using a thin ZnO layer fabricated by atomic layer deposition (ALD) is demonstrated for the first time. The thin ZnO layer was grown on the face of a standard optical telecommunication fiber SMF-28 and operates as a Fabry–Perot interferometer sensitive to temperature. The interferometer characterization was made in the temperature range extending from 50 to 300 °C with resolution equal to 1 °C. The output signal was analyzed by measurement of the shift of the maxima in spectral pattern. The sensitivity of temperature measurement is about 0.05 nm/°C. Furthermore, very good linearity of the sensor was achieved with correlation coefficient R2…
Dual-Comb Spectroscopy With Frequency-Agile Lasers
2015
Multiheterodyne frequency comb spectroscopy without mode-locked lasers is reported in the near-infrared C and L telecommunication bands. The system without active stabilization combines high signal-to-noise ratio, rapid tuning and moderate multiplex spectral span.