Showing papers on "Speckle imaging published in 1982"
TL;DR: The many methods suggested and (some of them) tried out experimentally and/or observationally for imaging celestial objects through the Earth's atmosphere are reviewed in this paper, where their theoretical and physical bases are examined.
118 citations
TL;DR: In this paper, an expression for the life-time of stellar speckle as a function of the distribution of wind and turbulence in the Earth's atmosphere is given, in agreement with previously published observations and with the results of a laboratory simulation.
Abstract: An expression is given for the life-time of stellar speckle as a function of the distribution of wind and turbulence in the Earth's atmosphere. Estimates of this parameter are in agreement with previously published observations and with the results of a laboratory simulation.
114 citations
TL;DR: In this paper, an experiment in narrow spectral band speckle interferometry is described, which uses variations in the spectrum across the astronomical object under study, to obtain information of the object on the millisecond of arc scale.
Abstract: This paper describes an experiment in narrow spectral band speckle interferometry, which uses variations in the spectrum across the astronomical object under study, to obtain information of the object on the millisecond of arc scale. We plan to apply this experiment to the study of spectroscopic double stars, stellar rotation, spectroscopic and magnetic variable stars and other astronomical objects.
66 citations
TL;DR: In this paper, the statistical theory of coherent speckle patterns is compared to classical coherence theory, and it is shown that the Hanbury Brown and Twiss effect is directly analogous to the Coherence effect.
Abstract: The statistical theory of fully developed, coherent speckle patterns is compared to classical coherence theory. It is shown that speckle correlations are directly analogous to the Hanbury Brown and Twiss effect. On that background a unified description is given for a number of measurement techniques based on intensity correlation measurements in scattered laser light: holographic interferometry, speckle pattern interferometry, speckle photography, stellar speckle interferometry, laser Doppler velocimetry and intensity correlation spectroscopy.
58 citations
TL;DR: In this paper, it was shown that previously published expressions for the isoplanatic angle do not apply to stellar speckle interferometry and a new expression was derived and found in better agreement with published observations.
Abstract: It is shown that previously published expressions for the isoplanatic angle do not apply to stellar speckle interferometry. A new expression is derived and found in better agreement with published observations.
46 citations
TL;DR: The main methods of speckle shear interferometry include Michelson's interferometric arrangement, two or multiple apertures in conjunction with a lens and defocusing, and use of parallel plates and wedges in front of the lens with or without aperture.
Abstract: The main methods of speckle shear interferometry include Michelson's interferometric arrangement, two or multiple apertures in conjunction with a lens and defocusing, and use of parallel plates and wedges in front of the lens with or without apertures. It has been our experience that the partial slope fringes are not localized at the plane of the specklegram in the case when defocusing is used for shear.
31 citations
TL;DR: A method for reconstructing a diffraction-limited image from data consisting of many short-exposure turbulence degraded images is described and a computer simulation indicates that the method may be applicable to astronomical objects as faint as approximately 11th magnitude.
Abstract: A method for reconstructing a diffraction-limited image from data consisting of many short-exposure turbulence degraded images is described. The results of a computer simulation of the method are presented. The method should prove useful for obtaining high-angular resolution images from large earth bound telescopes. The simulation indicates that the method may be applicable to astronomical objects as faint as ~11th magnitude.
27 citations
26 citations
24 citations
TL;DR: The study unveils the influence of parasite movements, field angles, and the geometrical parameters at the recording on the measured component, thereby paving the way for the optimization of a method to a given deformation problem and forging a better understanding of the phenomenon underlying these techniques.
Abstract: Considerable interest in speckle metrology and a consistent search to refine these techniques to suit the intricate engineering environment has led to an active investigation into the basic aspects of speckle movements in three-dimensional space induced by small displacements and deformations of the object surface. The model exploited in this paper is based on the notion of the local invariance of the speckle structure in such a case; it is thus intimately related to the concept of homology and draws closely on the theories aiming to reconcile speckle metrology and holographic interferometry techniques. The laws of speckle motions issuing from this model are applied to major known techniques in speckle photography (focused or defocused), speckle interferometry, and speckle shearing interferometry in an attempt to make as objective an assessment as possible of these methods. The study unveils the influence of parasite movements, field angles, and the geometrical parameters at the recording on the measured component, thereby paving the way for the optimization of a method to a given deformation problem and forging a better understanding of the phenomenon underlying these techniques.
20 citations
16 Nov 1982
TL;DR: In this article, a photon-sensitive camera for speckle imaging of astronomical sources, high-resolution spectroscopy of faint galaxies in a crossed-dispersion spectrograph, or narrow-band direct imaging of galaxies, is presented.
Abstract: A photon-sensitive camera, applicable to speckle imaging of astronomical sources, high-resolution spectroscopy of faint galaxies in a crossed-dispersion spectrograph, or narrow-band direct imaging of galaxies, is presented. The camera is shown to supply 8-bit by 8-bit photon positions (256 x 256 pixels) for as many as 10 to the 6th photons/sec with a maximum linear resolution of approximately 10 microns. The sequence of photon positions is recorded digitally with a VHS-format video tape recorder or formed into an immediate image via a microcomputer. The four basic elements of the camera are described in detail: a high-gain image intensifier with fast-decay output phosphor, a glass-prism optical-beam splitter, a set of Gray-coded masks, and a photomultiplier tube for each mask. The characteristics of the camera are compared to those of other photon cameras.
TL;DR: The characteristics and performance of a Ranicon photon-counting system combined with digital tape recording are described and Astronomical applications will include low light level quantitative imaging and speckle imaging.
Abstract: The characteristics and performance of a Ranicon photon-counting system combined with digital tape recording are described. The most important features are a bialkali photocathode response over 256 X 256 digital pixels, with approximately 100 X 100 resolvable pixels at 50% MTF, a dead time of 16 microsec/count, a maximum recordable count rate of 14,400/sec, and a background of less than 1 count/digital pixel/h. A video cassette recorder serves for the digital recording which retains the temporal sequence of the registered photons. Astronomical applications will include low light level quantitative imaging and speckle imaging.
TL;DR: In this paper, the spatial structure at 4.8 microns has been observed in W3-IRS 5, Mon R2- IRS 3, and S 140-SIRS 1, the first two of which are clearly double.
Abstract: The spatial structure at 4.8 microns has been observed in W3-IRS 5, Mon R2-IRS 3, and S 140-IRS 1, the first two of which are clearly double. In addition, for four compact sources, low upper limits can be set to the angular diameters which are near those for blackbodies having the same fluxes and color temperatures observed for those sources. With a factor-of-2 higher-resolution, one may be able to distinguish between thermal emission or reddening as the source of the observed spectral shape.
TL;DR: In this technique, the object is illuminated with two symmetrically oriented beams, and an image plane hologram is recorded in photoconductor-thermoplastic devices which can be developed in situ and in virtually real time.
Abstract: A technique for separating the in-plane and out-of-plane motions of a tested object in hologram interferometry is described. In this technique, the object is illuminated with two symmetrically oriented beams, and an image plane hologram is recorded in photoconductor–thermoplastic devices which can be developed in situ and in virtually real time. Then the hologram is read out with the object waves only, thereby reconstructing the reference beam. If the object is moved or deformed during readout, fringes denoting equal in-plane motion appear as long as the motion is less than the speckle size. The exact arrangement is presented along with experimental results, which are compared with conventional holographic interferometry results.
Journal Article•
TL;DR: In this paper, a video speckle camera has been designed, constructed, and successfully used to record data for a wide variety of astronomical objects, including solar features, and the problems associated with recovering images from specckle data have been explored extensively.
Abstract: : The hardware and software required to demonstrate and evaluate the speckle imaging process for use on solar features have been developed and tested. A video speckle camera has been designed, constructed, and successfully used to record data for a wide variety of astronomical objects, including solar features. The problems associated with recovering images from speckle data have been explored extensively. Particular attention has been given to identifying and correcting effects due to noise bias and edges in images reconstructed from real as well as simulated data. The principles involved in imaging solar features at improved resolution by means of speckle techniques have been delineated, and sample images recovered from a variety of test data. (Author)
01 Jan 1982
TL;DR: Differential speckle interferometry has been used to study stellar rotation, evolution of stellar systems, spectroscopic binaries, the mass-luminosity relation, and peculiar A stars.
Abstract: We propose to develop a technique to achieve submillisecond of arc resolution on stellar objects It uses the fact that the spectrum of the light emitted by such an object often changes across its surface either because of Doppler shifts, Zeeman splitting, abundance anomalies or changes in the stellar atmosphere By an appropriately designed ex-periment using narrow band (05 – 1 A) filters, it is then possible to obtain differences between the position of speckles in the stellar image when viewed in slightly different wavelengths It is possible to determine these differences in the position of the speckles with an accuracy much higher than the speckle size itself using techniques which are already developed for binary star-speckle research We propose to use the technique of “Differential Speckle Interferometry” to study stellar rotation, evolution of stellar systems, spectroscopic binaries, the mass-luminosity relation, and peculiar A stars
04 Nov 1982
TL;DR: In this paper, the use of a telescope with a "one dimensional" aperture (10 x 800 cm for example) is suggested for high angular speckle interferometry in the image plane, the speckles are elongated in a direction perpendicular to the entrance pupil.
Abstract: The use of a telescope with a "one dimensional" aperture (10 x 800 cm for example) is suggested for high angular speckle interferometry. In the image plane, the speckles are elongated in a direction perpendicular to the entrance pupil. For a given amount of atmospherical turbulence, a one-dimensional pupil gives a contrast gain in the high frequencies region compared to the circular objective having the same resolution limit. Associated with a spectroscope, a one-dimensional telescope allows the representation of the spatial-spectral plane with no loss of photons. This is obtained because the image of the telescope aperture is the entrance slit of the spectroscope. It permits precise, high resolution astronomical measurements as a function of wavelength as well as velocity speckle-interferometry at high level of photons with CORAVEL type experiments. The study of a domeless, altazimuthal mount, low-cost prototype of 4 cm x80 cm, intended for solar observations, is developed at the Nice Observatory.
01 Feb 1982
TL;DR: In this article, an iterative reconstruction algorithm was proposed to reconstruct diffraction-limited images from the Fourier modulus (or autocorrelation) data provided by stellar speckle interferometry.
Abstract: : This report describes the results of a two-year research effort to investigate the reconstruction of fine-resolution images of space objects using earth-bound optical telescopes despite the turbulence of the atmosphere. The results of this research are an indication that, using an iterative reconstruction algorithm, it is feasible to reconstruct diffraction-limited images from the Fourier modulus (or autocorrelation) data provided by stellar speckle interferometry. Methods of compensating for systematic errors and noise present in astronomical data were developed and were applied to binary star data, from which a diffraction-limited image was successfully reconstructed. It was analytically shown that the following types of objects are uniquely specified by their Fourier modulus: objects consisting of separated parts satisfying certain disconnection conditions, objects consisting of collections of distinct points, and objects with radial symmetry. Experimental indications are that complicated two-dimensional objects are usually unique. An equivalence of the error-reduction iterative reconstruction algorithm and the steepest-descent gradient search method was shown, and the convergence of this algorithm was proven. However, the input-output iterative algorithm and other gradient search algorithms were found to converge much faster in practice. A survey of other applications of the iterative algorithm was performed, and it was found to be remarkably useful in solving problems for a wide range of applications.
TL;DR: A multiple-aperture imaging system generates the modulated speckles and produces an image plane hologram in which the various complex waveforms, passing through the individual apertures, operate simultaneously as object and reference beams.
Abstract: A technique is described for recording and reconstructing two- and three-dimensional color images utilizing a fringe-modulated speckle pattern. A multiple-aperture imaging system generates the modulated speckles and produces an image plane hologram in which the various complex waveforms, passing through the individual apertures, operate simultaneously as object and reference beams. This holographic recording system is considerably less sensitive to external vibration than conventional off-axis holography and requires much less stringent temporal- and spatial-coherence specifications for its light source.
01 Jan 1982
TL;DR: A complete data analysis system utilizing laser speckle interferometry and Experimental Integral Equation Method (EBIE) and the basic theory of pointwise filtering and digital correlation is described as experimental data input to the BIE method.
Abstract: A complete data analysis system utilizing laser speckle interferometry and Experimental Integral Equation Method (EBIE) is described. A host computer provides the optical data analysis and serves as an input device to a PDP11/VAX computer for numerical analysis. The basic theory of pointwise filtering and digital correlation is described as experimental data input to the BIE method.
16 Nov 1982
TL;DR: The Canada-France-Hawaii Telescope Co. two-dimensional array of infrared detectors has been applied for the first time to the stellar speckle interferometry technique.
Abstract: The Canada-France-Hawaii Telescope Co. two-dimensional array of infrared detectors has been applied for the first time to the stellar speckle interferometry technique. Preliminary results are presented.
TL;DR: In this paper, the spectroscopic binary star 94 Aqr A is analyzed in order to determine the Aa,b system visual orbit, and the angular separation and position angle observations yield orbital elements which are in agreement with those obtained by Sarma (1961) spectroscopically, and which in combination with the trigonometric parallax of 0.033 arcsec yield Aa and Ab component masses of 3.0 and 1.2 solar masses, and absolute magnitudes of +3.1 and +4.6, respectively.
Abstract: Speckle observations of the spectroscopic binary star 94 Aqr A are analyzed in order to determine the Aa,b system visual orbit. Eleven angular separation and position angle observations yield orbital elements which are in agreement with those obtained by Sarma (1961) spectroscopically, and which in combination with the trigonometric parallax of 0.033 arcsec yield Aa and Ab component masses of 3.0 and 1.2 solar masses, and absolute magnitudes of +3.1 and +4.6, respectively.
01 Jan 1982
TL;DR: A speckle pattern is a pattern made up of irregularly spaced dot (specs) as discussed by the authors, which is created by interference between a great number of wavelets with random phase values.
Abstract: By formal definition, a speckle pattern is a pattern made up of irregularly spaced dots (specs). In optics, the speckle pattern is (usually) created by interference between a great number of wavelets with random phase values. These wavelets are formed when coherent light is reflected from a rough surface or transmitted through a diffusing media.
04 Nov 1982
Abstract: Speckle interferometry techniques are especially attractive with large future telescopes. For example, a 10m telescope can yield an angular resolution of 0.01 arc sec in spite of image degradation by the atmosphere. The limiting magnitude of speckle interferometry is about 20m. We intend to discuss the following aspects of speckle methods: (a) The influence of telescope aberrations on speckle interferometry measurements. We show laboratory simulations of speckle interferometry with severe stationary telescope aberrations. (b) Roll deconvolution: a method for reconstructing high-resolution images from Space Teles-cope data. In the case of the 2.4m Space Telescope a resolution of about 0.01 arc sec can be achieved. (c) The reconstruction of direct images (instead of autocorrelations) from speckle interfero-grams. Applications on data recorded with large telescopes are discussed. Reconstruction of high-resolution objective prism spectra with the speckle spectroscopy method.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Journal Article•
TL;DR: A method for recording, on black and white photographic emulsion, the image of coloured objects is described in this article, where the reconstruction of this image with the colours of the object is explained.
Abstract: A method for recording, on black and white photographic emulsion, the image of coloured objects is described. For this purpose, we have used an interferential device by division of wavefront. The reconstruction of this image with the colours of the object is explained.
01 Jan 1982
TL;DR: The description of a speckle camera used with the BTA 6-meter telescope is given in this article, where the Fourier optical spectrum analyzer is used to estimate atmospheric parameters.
Abstract: The description of a speckle camera used with the BTA 6-meter telescope is given. Observational data recorded on photographic film are processed with a Fourier optical spectrum analyzer. Results of binary star measurements are presented. Analysis of short exposure images of a point source obtained with telescopes of various sizes allows the estimation of atmospheric parameters which are necessary for correct application of speckle interferometry.