A digital speckle pattern interferometer was built utilizing a 100 x 100 element reticon diode array interfaced to an hp9836c desktop computer. As any ao correction is only partial there is a need to use postfacto reconstruction algorithms to achieve the diffraction limit of the telescope over a large field of view most of the observational time. Astronomical imaging by processing stellar speckle. Electronic speckle pattern interferometry espi is a wellknown application of the speckle effect. It is illustrated by the implementation of a homemade 410mm telescope dedicated to double stars measurements and highlights the most important practical tips. A simple method speckle masking for the reconstruction of real images from astronomical speckle photographs is described.
Nov 17, 2008 there are two different algorithms in the program speckle. A total of 1641 observations were taken, yielding 1636 measurements of 1218 resolved binary and multiple stars and 577 nonresolutions of. In addition, speckle interferometry is applicable to the. This chapter describes the application of two experimental techniques, based on the speckle effect, to damage identification. A tremendous number of applications have been developed in various fields pattern recognition, interferometry, contouring, information processing, optical memories a volume hologram may store up to 10 9 bitsmm3, spectroscopy, optical reading, microscopy, detection of fatigue failure in materials or atmospheric pollutants, etc. In 1970, the french astronomer antoine labeyrie showed that fourier analysis speckle interferometry can obtain information about the highresolution structure of the object from the statistical properties of the speckle patterns. High speed electronic speckle pattern interferometry espi. With improvements in image quality it has the potential. An astronomical interferometer is an array of separate telescopes, mirror segments, or radio telescope antennas that work together as a single telescope to provide higher resolution images of astronomical objects such as stars, nebulas and galaxies by means of interferometry.
A more recent method, called speckle interferometry, has been developed to reproduce the true disks of red supergiant stars and to resolve spectroscopic binaries such as capella. Modified astronomical speckle interferometry speckle masking. Introduction the speckle interferometry is a favorite professional tool for measuring double stars. Interplanetary dust, age determinations on lunar samples, space based gamma ray detector, speckle interferometry. Calvo department of optics, complutenseuniversity of madrid 17thfebruary 2017, 11. Speckle interferometry as a method for detecting nearby extrasolar. Speckle interferometry imposes special requirements on the equipment, such as low noise, low power and fast readout. The results of speckle interferometric measurements of binary and multiple stars conducted in 2008 and 2009 at the blanco and soar 4 m telescopes in chile are presented. New method of processing speckle interferometry solar.
The speckle phenomenon is a rapidly changing interferencediffraction effect seen in a highly magnified diffraction image of a star. The speckle camera is improved with a tv acquisition and guiding camera. Image processing was therefore necessary to enhance the fringe clarity. A singlemode optical fiber mounted in the center of the systems aperture stop creates a sphericalwave reference beam.
Double stars are the object most frequently observed with speckle interferometry techniques. Some rare amateurs use this technique on missions in observatories, but none seem to use it routinely with a classical amateur instrumentation. Detecting planets in binary systems with speckle interferometry. Speckle interferometry of nearby multiple stars astronomy.
The steward observatory speckle interferometry program. Optical interferometry in astronomy 793 is resolved by an interferometer if the fringe contrast goes to zero at the longest baseline. Data acquisition is made by a photoncounting detector cp40. Diffractionlimited images, of resolution many times finer than what is ordinarily obtainable through large earthbound telescopes, can be obtained by first measuring the modulus of the fourier transform of an object by the method of labeyries stellar speckle interferometry, and then reconstructing the object by an iterative method. The integration time was initialized at 10ms, and increased in increments of 10ms if the full emccd gain for a given integration time setting was insufficient. This method is applicable to a restricted class of objects that includes double stars. Volume 21, number 1 optics communications april 1977 modified astronomical speckle interferometry speckle masking g. The results of speckle interferometric observations at the southern astrophysical research telescope soar telescope in 2014 are given.
Many astronomical applications require observations with high spatial resolu tion. Electronic speckle pattern interferometry espi is becoming a very common test and measurement tool among industrial users. This talk shows how using interferometry methods provides routinely accurate measurements with a midsized amateur telescope. Speckle1 is a program package for astronomical speckle interferometry. Speckle interferometry with midsized amateur telescope. This paper describes how to use a speckle interferometry reduction program, the speckle tool box stb, to achieve this level of result. A total of 1898 measurements of 1189 resolved pairs or subsystems and 394 observations of 285 unresolved targets are listed. Other articles where speckle interferometry is discussed. Automated speckle interferometry of double stars avoid atmospheric smearing, emccd gain adjustments up to a gain setting of 300 were preferred over increasing integration times. Ask all questions argued to set an author, he will answer. Germany received 26 january 1977 a simple method speckle masking for the reconstruction of real images from astronomical speckle photographs is described.
The applicability of the technique of speckle interferometry to the problem of detecting faint planetary and. However, it has been during the last 15 years that espi, boosted by the availability of affordable and increasingly powerful digital image processing systems, has grown into one of the leading optical measurement techniques, receiving new names such as tv. In robert argyles book on amateur astronomy, there is a chapter on speckle interferometry for the amateur. Sparse aperture speckle interferometry telescope active. Digital speckle pattern interferometry dspi is the generic name for a class of important interferometric techniques such as tv holography, electronic holography or phase shifting pattern interferometry, all of which involve similar optical and electronic principles.
Electronic speckle pattern interferometry espi use tv system to record speckle instead of film gives realtime measurements minimum speckle size limited by camera resolution can perform computer analysis of speckle data optics 505 james c. How speckle reduction software works the speckle tool box does speckle reduction by working on a fits cube. These techniques can dramatically increase the resolution of groundbased telescopes, but. Astronomical interferometers can produce higher resolution astronomical images than any other type of telescope. A typical stellar image has, at best, a diameter given by that of the diffractionlimited airy disk. As motivated in the last paragraph, this occurs when the angular separation is. Espi abbreviation stands for electronic speckle pattern interferometry.
Electronic speckle pattern interferometry espi sciencedirect. Speckle imaging definition of speckle imaging by the. Astronomical speckle imaging is a well established technique for obtaining diffraction limited images of. A prototype active optics system was created and fitted to a telescope frame using relatively low cost components.
This is a phenomenon that occurs when coherent light. Speckle interferometry astronomical institute www homepage. Pdf application of speckle interferometry to damage. The present status of the steward observatory speckle interferometer system is presented, including development of instrumentation and basic reduction software, analysis of atmospheric properties, work on image reconstruction techniques, and observations of astronomical objects and certain classes of orbiting satellites. There are two different algorithms in the program speckle. On the amplitude interferometer program at the university of maryland. Teach astronomy astronomers have invented a clever technique to improve telescope performance. A simple design for an electronic speckle pattern interferometer. Speckle interference patterns need in any case a kind of further decoding step in order to become a source of useful information. In this case the algorithm of speckle was used with the parameters of kt, tc, radius of kt 9,25, radius of tc 25 and tc distance 25. The first one, known as electronic speckle pattern interferometry or.
Speckle interferometry has proven to be a powerful method for. In its present form it rivals any current techniques for speed and ease of use. Budinichlecture hall winter college on optics 2017. Digital speckle pattern interferometry and related techniques. Electronic speckle pattern interferometry espi non. A vmebased computer under os9 controls the detector and stocks the data. With improvements in image quality it has the potential to become the definitive tool for nondestructive testing.
Modified astronomical speckle interferometry speckle. The electromagnetic radiation collected at each of a number of separate small telescopes is combined to recreate the image that would have been obtained with the. This code uses speckle interferometry for estimating the. The visualisation is in the form of fringes on the image where each fringe normally represents a displacement of half a wavelength. Schematic of an electronic speckle pattern interferometer that is sensitive to out of plane displacement. An important consideration for narrowangle speckle interferometry is the sky coverage defined by the isoplanatic patch see the lecture of c. Speckle patterns have high frequency phase data, which make it difficult to find the absolute phase of a single speckle pattern. At radio wavelengths, image resolutions of a few microarcseconds have been obtained, and image resolutions of a fractional milliarcsecond have been achieved at visible and infrared wavelengths. We present a speckle interferometry code for solar data taken with the help of an adaptive optics ao system. Speckle imaging synonyms, speckle imaging pronunciation, speckle imaging translation, english dictionary definition of speckle imaging. What is the abbreviation for electronic speckle pattern interferometry. Electronic speckle pattern interferometry espi espi on the other hand, records the surface displacement of an object in response to the applied force. We present the results of diffractionlimited optical speckle interferometry and infrared.
The visualisation is in the form of fringes on the image where each fringe. One simple layout of an astronomical interferometer is a parabolic arrangement of mirror. Sparse aperture speckle interferometry telescope active optics control system matthew clause a conventional large aperture telescope required for binary star research is typically cost prohibitive. However, it has been during the last 15 years that espi, boosted by the availability of affordable and increasingly powerful digital image processing systems, has grown into one of the leading optical measurement techniques, receiving new names such as tv holography or digital speckle pattern interferometry. Speckle interferometry article about speckle interferometry. Application of speckle interferometry to damage identification. The most fruitful application of speckle interferometry in astronomy has been in the study of binary stars, yielding individual stellar masses and the distances to the systems and providing reliable data for the empirical massluminosity relation in a region which is intermediate between visual and purely spectroscopic data. Theory and applications on free shipping on qualified orders. Speckle interferometry under linux in robert argyles book on amateur astronomy, there is a chapter on speckle interferometry for the amateur. Speckle interferometry definition is a technique for generating a clear composite image of a celestial object blurred by atmospheric turbulence in which a large number of shortexposure photographs are mathematically correlated by a computer. Speckle imaging with the soar and the very large telescopes. Stellar speckle interferometry is a technique for obtaining diffractionlimited resolution of stellar objects despite the presence of the turbulent atmosphere which limits the resolution of conventional longexposure pictures to approximately one arc second. This would also reduce many of the errors inherent in espi. The technique, called interferometry, uses widely separated telescopes in a special arrangement to increase.
Interferometry in this case astronomical interferometry is a technique that astronomers use to obtain the resolution of a large telescope by using multiple smaller telescopes. Speckle interferometry is particularly suited for work with closespaced. The image intensity of the speckle pattern formed by video signal subtraction is low. Speckle photography, electronic speckle pattern interferometry espi, speckle holography, stellar speckle interferometry, and speckle interferometry using photographic recording are among the. They can be divided into the shiftandadd image stacking method and the speckle interferometry methods. Electronic speckle pattern interferometry wikipedia. This paper describes how to use a speckle interferometry reduction pro. This trick makes it appear as if we have a bigger telescope than we really do. However, in the undergraduate laboratory and for many research applications, fig. Phaseshifting speckle interferometry katherine creath speckle patterns have high frequency phase data, which make it difficult to find the absolute phase of a single speckle pattern. Espi can be used in arrangements where fringes will represent lines of either inplane or outofplane displacement. The configuration of the correlation fringes is usually dim.
Speckle interferometry at soar in 2014 journal article. In that chapter, the reader is referred to this web page for information on how to get the software to calculate the directed vector autocorrelogram dva using a matrox meteor video frame grabber board under linux. In that chapter, the reader is referred to this web page for information on how to get the software to calculate the directed vector autocorrelogram dva using a matrox meteor video frame grabber board. This software provides an intelligent assistance to the user by choosing observational parameters as a function of atmospheric parameters, computed in real time, and the desired restored image quality. Electronic speckle pattern interferometry espi, also known as tv holography, is a technique which uses laser light, together with video detection, recording and processing to visualise static and dynamic displacements of components with optically rough surfaces.
This is done by applying phaseshifting techniques to speckle interferometry, which will quantitatively determine the phase of doubleexposure speckle measurements. Nov 16, 2008 speckle1 is a program package for astronomical speckle interferometry. A prototype active optics system was created and fitted to a. A on the applications of interference methods to astronomical. A digital specklepattern interferometer was built utilizing a 100 x 100 element reticon diode array interfaced to an hp9836c desktop computer.