Dr. Saifollah Rasouli Profile

Dr. Saifollah Rasouli

Associate Professor of Physics at Institute for Advanced Studies in Basic Sciences

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Publications (7)

Proceedings Article | 1 October 2009 Paper

Two-channel wavefront sensor arrangement employing moire deflectometry

Saifollah Rasouli, Anamparambu Ramaprakash, H. K. Das, C. V. Rajarshi, Yasser Rajabi, M. Dashti

Proceedings Volume 7476, 74760K (2009) https://doi.org/10.1117/12.829962

KEYWORDS: Wavefronts, Wavefront sensors, Deflectometry, Turbulence, Atmospheric propagation, Beam splitters, CCD cameras, Moire patterns, Atmospheric sensing, Sensors

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A wavefront sensor which takes advantage of the moire deflectometry has been constructed for measuring atmosphere induced wavefront distortions. In this sensor a collimated laser beam propagates through turbulent atmosphere, then a beam splitter splits it into two beams and the beams pass through a pair of moire deflectometers. Directions of the grating's rulings are parallel in each moire deflectometer but are perpendicular in the two beams. Using a suitable array of lenses and mirrors two sets of moire patterns are projected on a CCD camera. A suitable spatial filter removes the unwanted frequencies. Recording the successive moire patterns by the CCD camera and feeding them to a computer, allow temporal fluctuations of the laser beam wavefront phase to be measured highly accurately. Displacements of the moire fringes in the recorded patterns correspond to the fluctuations of two orthogonal components of the angle of arrival (AA) across the wavefront. The fluctuations have been deduced in successive frames, and then evolution of the wavefront shape is determined. The implementation of the technique is straightforward and it overcomes some of the technical difficulties of the Schlieren and Shack-Hartmann techniques. The sensitivity of detection is adjustable by merely changing the distance between two gratings in both moire deflectometers and relative grating ruling orientation. This overcomes the deficiency of the Shack-Hartman sensors in that these require expensive retrofitting to change sensitivity. Besides, in the moire deflectometry, the measurement is relatively insensitive to the alignment of the beam into the device. Hence this setup has a very good potential for adaptive optics applications in astronomy. Since tilts are measured in the Shack-Hartmann method at discrete locations, it cannot detect discontinuous steps in the wavefront. By this method discontinuous steps in the wavefront are detectable, because AA fluctuations are measured across the wavefront.

SPIE Journal Paper | 1 May 2008

Determination of vibration parameters of a large-scale structure by measuring the visibility changes on the time-averaged images of a sinusoidal pattern fixed on it

Saifollah Rasouli, Mohammad Tavassoly

OE, Vol. 47, Issue 05, 053603, (May 2008) https://doi.org/10.1117/12.10.1117/1.2927460

KEYWORDS: Visibility, Video, Optical engineering, Holographic interferometry, Bessel functions, Iron, Holography, Modal analysis, Digital holography, Imaging systems

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Proceedings Article | 28 September 2006 Paper

Measurement of modulation transfer function of the atmosphere in the surface layer by moiré technique

Saifollah Rasouli, Khosro Madanipour, Mohammad Tavassoly

Proceedings Volume 6364, 63640K (2006) https://doi.org/10.1117/12.687614

KEYWORDS: Modulation transfer functions, Transmittance, Imaging systems, Atmospheric optics, Ronchi rulings, Turbulence, Atmospheric propagation, Image quality, Image transmission, Atmospheric physics

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Proceedings Article | 28 September 2006 Paper

Measurement of the refractive-index structure constant,C2n, and its profile in the ground level atmosphere by moiré technique

Saifollah Rasouli, Mohammad Tavassoly

Proceedings Volume 6364, 63640G (2006) https://doi.org/10.1117/12.683873

KEYWORDS: Atmospheric propagation, Turbulence, Refractive index, Atmospheric turbulence, Atmospheric optics, Telescopes, Wavefronts, Wave propagation, Radio propagation, Astronomical imaging

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Proceedings Article | 28 January 2006 Paper

Nondestructive measurement of refractive index profile of optical fiber preforms using moiré technique and phase shift method

Samaneh Ranjbar, Hamid Khalesifard, Saifollah Rasouli

Proceedings Volume 6025, 602520 (2006) https://doi.org/10.1117/12.667094

KEYWORDS: Refractive index, Optical fibers, Liquids, Nondestructive evaluation, Interferometry, Phase shifts, Collimation, Ronchi rulings, Control systems, Helium neon lasers

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Proceedings Article | 9 December 2005 Paper

Moiré deflectometer for measuring distortion in sheet glasses

Saifollah Rasouli, Mohammad Tavassoly

Proceedings Volume 6024, 60240E (2005) https://doi.org/10.1117/12.666818

KEYWORDS: Glasses, Distortion, Imaging systems, Fringe analysis, Phase shifting, Phase shifts, Signal processing, Moire patterns, Glass casting, Image transmission

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Proceedings Article | 13 June 2005 Paper

Specification of vibrational modes and amplitudes in large-scale structure by time averaging moiré technique

Saifollah Rasouli, Mohammad Tavassoly

Proceedings Volume 5856, (2005) https://doi.org/10.1117/12.612414

KEYWORDS: Visibility, Holographic interferometry, Reflectivity, Imaging systems, Bessel functions, Speckle interferometry, Modal analysis, Image processing, Mechanical engineering, Digital cameras

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Showing 5 of 7 publications

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