scispace - formally typeset
Search or ask a question
Topic

Speckle imaging

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


Papers
More filters
Journal ArticleDOI
TL;DR: The state of the art and the path to future progress in high-spatial-resolution imaging interferometry is reviewed in this article, with a focus on the problems specific to delay lines, beam recombination, polarization, dispersion, fringe tracking, bootstrapping and cophasing.
Abstract: The present ``state of the art'' and the path to future progress in high-spatial-resolution imaging interferometry is reviewed. The review begins with a treatment of the fundamentals of stellar optical interferometry, the origin, properties, and optical effects of turbulence in the Earth's atmosphere, the passive methods such as speckle interferometry that are applied on a single telescope to overcome atmospheric image degradation, and various other techniques. These topics include differential speckle interferometry, speckle spectroscopy and polarimetry, phase diversity, wave-front shearing interferometry, phase-closure methods, dark speckle imaging, as well as the limitations imposed by the detectors on the performance of speckle imaging. A brief account is given of the technological innovation of adaptive optics to compensate for atmospheric effects on the image in real time. A major advancement involves the transition from single-aperture to dilute-aperture interferometry using multiple telescopes. Therefore the review deals with recent developments involving ground-based and space-based optical arrays. Emphasis is placed on the problems specific to delay lines, beam recombination, polarization, dispersion, fringe tracking, bootstrapping, coherencing and cophasing, and recovery of the visibility functions. The role of adaptive optics in enhancing visibilities is also discussed. The applications of interferometry, such as imaging, astrometry, and nulling, are described. The mathematical intricacies of the various ``postdetection'' image-processing techniques are examined critically. The review concludes with a discussion of the astrophysical importance and the prospects of interferometry.

45 citations

Proceedings ArticleDOI
TL;DR: The presented speckle interferometry code is capable to run in future real-time reconstruction applications at solar telescopes if care is taken that the multi-processor environments have low latencies between the processing nodes.
Abstract: We present a speckle interferometry code for solar data taken with the help of an adaptive optics (AO) system. As any AO correction is only partial there is a need to use post-facto reconstruction algorithms to achieve the diffraction limit of the telescope over a large field of view most of the observational time. However, data rates of current and future solar telescopes are ever increasing with camera chip sizes. In order to overcome the tedious and expensive data handling, we investigate the possibility to use the presented speckle reconstruction program in a real-time application at telescope sites themselves. The program features Fourier phase reconstruction algorithms using either an extended Knox-Thompson or a triple correlation scheme. The Fourier amplitude reconstruction has been adjusted for use with models that take the correction of an AO system into account. The code has been written in the C programming language and optimized for parallel processing in a multi-processor environment. We analyze the scalability of the code to find possible bottlenecks. Finally, the phase reconstruction accuracy is validated by comparison of reconstructed data with satellite data. We conclude that the presented code is capable to run in future real-time reconstruction applications at solar telescopes if care is taken that the multi-processor environments have low latencies between the processing nodes.

45 citations

Journal ArticleDOI
TL;DR: This Letter proposes a motionless diffractive optical element (DOE) for speckle reduction that was designed based on finite-element method simulations, fabricated using micromachining technology, and characterized for despeckle efficiency.
Abstract: Speckle reduction by moving diffuser has been previously studied in display systems with coherent light sources, such as lasers. In this Letter, we propose a motionless diffractive optical element (DOE) for speckle reduction. The DOE was designed based on finite-element method simulations, fabricated using micromachining technology, and characterized for despeckle efficiency. Experiments using a DOE with two gratings have indicated that the speckle was suppressed to 50%, which shows fair agreement with theoretical analysis. With some modification of this DOE, the speckle noise can be reduced to 10% according to the theory.

45 citations

Journal ArticleDOI
TL;DR: In this paper, surveys on automatic and quantitative deformation measurements using CCDs and computers in holographic interferometry and speckle metrology for diffusely reflecting surfaces are presented.

45 citations

Patent
09 Mar 1979
TL;DR: In this paper, the photodetector output component at the frequency of the surface movement representing that movement is used to produce a speckle pattern therefrom by coherent light illumination.
Abstract: Measurement of small oscillatory movements of an irregular surface involves the production of a speckle pattern therefrom by coherent light illumination, and the arrangement of a photodetector for direct response to such pattern, variations in photodetector output component at the frequency of the surface movement representing that movement. Another, stationary, illuminated irregular surface can be involved to produce a speckle interference pattern for response of the photodectector thereto and, in the case where the two surfaces are closely adjacent, a single beam can be used to illuminate the first and other surfaces predominantly and by stray light, respectively. This common beam illumination can be used in prior speckle interferometry. The first surface can be an eardrum oscillated by a sound wave, suitably of swept frequency or impulse form, with detection of the photodetector variations respectively being in synchronous manner or by Fourier analysis, respectively.

45 citations


Network Information
Related Topics (5)
Interferometry
58K papers, 824.8K citations
88% related
Optical fiber
167K papers, 1.8M citations
82% related
Polarization (waves)
65.3K papers, 984.7K citations
81% related
Light scattering
37.7K papers, 861.5K citations
80% related
Emission spectrum
36.9K papers, 878.7K citations
79% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202332
202249
202162
202079
201972
201895