Speckle imaging

About: Speckle imaging is a research topic. Over the lifetime, 3730 publications have been published within this topic receiving 62354 citations.

Analysis of the shift-and-add method for imaging through turbulent media

Abstract: We examine the statistical basis of the shift-and-add technique, by which true images of objects (viewed through fluctuating, distorting media) are formed by a particular kind of averaging of speckle images Our theory agrees with experimental results for objects consisting of isolated unresolvable points We develop a preliminary analysis for extended objects (i e, objects having continuous, resolvable brightness distributions)

Bispectrum speckle interferometry of the B[e] star MWC 349A

Abstract: We present the results of bispectrum speckle interferometry of the B[e] star MWC 349A obtained with the SAO 6 m telescope. Our diffraction-limited J-, H-, and K-band images (resolutions 43–74 mas) suggest the star is surrounded by a circumstellar disk seen almost edge-on. The observed visibility shape is consistent with a two-component elliptical disk model, probably corresponding to the gaseous and dusty components of the disk. We show that the classification of the object as a pre-main-sequence star or a young planetary nebula is problematic. An analysis of the uncertainties in the basic parameter determination lead us to the conclusion that MWC 349A is probably either a B[e] supergiant or a binary system, in which the B[e]-companion dominates the observed properties.

Diffraction-Limited Imaging with Large and Moderate Telescopes

Abstract: Introduction to Electromagnetic Theory Wave Optics and Polarization Interference and Diffraction Image Formation Theory of Atmospheric Turbulence Speckle Imaging Adaptive Optics High Resolution Detectors Image Processing Astronomy Fundamentals Astronomical Applications.

The empirical mode decomposition: a must-have tool in speckle interferometry?

Abstract: In a wider and wider range of research and engineering activities, there is a growing interest for full-field techniques, featuring nanometric sensitivities, and able to be addressed to dynamic behaviors characterization. Speckle interferometry (SI) techniques are acknowledged as good candidates to tackle this challenge. To get rid of the intrinsic correlation length limitation and simplify the unwrapping step, a straightforward approach lies in the pixel history analysis. The need of increasing performances in terms of accuracy and computation speed is permanently demanding new efficient processing techniques. We propose in this paper a fast implementation of the Empirical Mode Decomposition (EMD) to put the SI pixel signal in an appropriate shape for accurate phase computation. As one of the best way to perform it, the analytic method based on the Hilbert transform (HT) of the so-transformed signal will then be reviewed. For short evaluation, a zero-crossing technique which exploits directly the extrema finding step of the EMD will be presented. We propose moreover a technique to discard the under-modulated pixels which yield wrong phase evaluation. This work is actually an attempt to elaborate a phase extraction procedure which exploits all the reliable information in 3D, – two space and one time coordinates –, to endeavor to make the most of SI raw data.

Measurement of complex surface deformation by high-speed dynamic phase-stepped digital speckle pattern interferometry.

Abstract: We describe a high-speed digital speckle pattern interferometer incorporating a line-scan camera and a waveguide phase modulator for the measurement of complex deformation (vibration phase and amplitude) at audio acoustic frequencies. Experimental data show continuous phase-stepped recovery of out-of-plane surface deformation in one dimension, obtained at 100 kHz with 2π/20‐rad0.02‐µm displacement resolution, for surface velocities of 3.2 mm s-1.