Vibrationobservation techniques for digital speckle. The image obtained for an unresolved point source depends on the exposure time. The outofplane setup can be briefly described as follows. A simple design for an electronic speckle pattern interferometer. Spatial versus temporal phase shifting in electronic speckle. In its present form it rivals any current techniques for speed and ease of use. This is one of the most sensitive interferometric technique, so that we can measure submicron level displacements either in plane or out of plane. Pulsed lasers in electronic speckle pattern interferometry. Squeezing interferometry for optical phase extraction in. A technique is described for observing vibrational and transient events with a double pulsed laser and some typical results are given.
Since its inception during the early 1970s espi has gradually evolved into different optical designs and has been applied to a range of. Pollard this paper describes the incorporation of a pulsed ruby laser into an electronic speckle pattern interferometer. In our paper we have analyzed the application possibility of a modified version of speckle pattern interferometry. With improvements in image quality it has the potential to become the definitive tool for nondestructive testing. What is the abbreviation for electronic speckle pattern interferometry. Espi abbreviation stands for electronic speckle pattern interferometry. We discuss a simple experiment for detecting small deformations by speckle interferometry. Phaseshifting speckle interferometry katherine creath speckle patterns have high frequency phase data, which make it difficult to find the absolute phase of a sin.
It can be used to measure surface displacement 2 and related parameters including dis1, placement derivative 3, strain 45, shape and slope 6, 7. Speckle interferometry is based on the coherent addition of scattered light from an object surface with a reference beam that may be a smooth wavefront or a scattered field from a reference object or from the sample. The speckle phenomenon is a rapidly changing interferencediffraction effect seen in a highly magnified diffraction image. An online simplified version of the data treatment software was also available to. The combination of electronic speckle pattern interferometry espi. Because of the ease with which the vibrations and small displacements of objects can be studied in real time, the electronic speckle pattern interferometer is the ideal tool for the undergraduate laboratory as. Simultaneous acquisition of 3d shape and deformation by combination of interferometric and correlationbased laser speckle metrology.
Florent also extended his userfriendly, welldocumented double star reduction software, reduc, to include speckle interferometry, paving the way for other amateur astronomers to also make speckle interferometry observations of close binaries on their telescopes. Vibrationobservation techniques for digital speckle pattern interferometry katherine creath optical sciences center, university of arizona, tucson, arizona 85721 gudmunn a. Digital speckle pattern interferometry and related techniques. Osa spatial versus temporal phase shifting in electronic. Amateur speckle interferometry ebsco information services. Speckle imaging describes a range of highresolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. The software can be used to count the correlation fringes and to transform them automatically into a quantitative set of deformation. A mechanically stable laser diode speckle interferometer.
The core of this technique is the using of the holographically reconstructed virtual images of reference waves. While speckle seams to be the standard, im happy to use other systems as well, but dont have easy access to lasers etc. First automated speckle interferometry was achieved on the 0. 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. Electronic speckle pattern interferometry espi is a wellknown application of the speckle effect. Phase shifting speckle interferometry for determination of. The project is supported by national natural science foundation of china grant nos. A nonimaging speckle interferometer measures position of a diffuse sample to nanometer precision. Conclusions with the data available in the literature, in com. The infrared speckle interferometer was based on the eso 3. 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. High speed electronic speckle pattern interferometry espi. Vibrationobservation techniques for digital specklepattern.
Electronic speckle pattern interferometry espi is a wholefield noncontact optical metrology technique for displacement measurement, based on the optical physics of surfacegenerated laser speckle. It relies on the interference between diffusely reflected light from the test object and a reference beam. Electronic speckle pattern interferometry espi is a nondestructive optical method for studying surface deformations. Schematic illustrations of typical optical arrangements for the two techniques are shown in figure 2. We give a brief description of the main principles of the method and the history of its development at large telescopes. We call this technique adaptive speckle imaging interferometry. Speckle interferometry article about speckle interferometry. In this paper we present two recent developments of speckle technique with applications to micromechanics problems using siem speckle interferometry with electron microscopy, to nondestructive evaluation of crevice corrosion and composite disbond and vibration of large structures using tads timeaverage digital specklegraphy.
Espi can be used in arrangements where fringes will represent lines of either inplane or outofplane displacement. Some rare amateurs use this technique on missions in observatories, but none seem to use it routinely with a classical amateur instrumentation. The event took place from september 25 to september 28, 2000. Temporal and spatial phase shifting in electronic speckle pattern interferometry are compared quantitatively with respect to the quality of the resultant deformation phase maps. In speckle interferometry, the optimal integration time goes as \approx\lambda1. We offer a complete package including equipment and software. Interferometers could soon be making life easier for people with diabetes. Jacquot nanophotonics and metrology laboratory, swiss federal institute of technology, ch1015 lausanne, switzerland. Mod01 lec06 hologram interferometry, speckle methods duration. The main advantage of the electronic speckle pattern interferometry as compared to the classical interferometry and holographic methods is ability to measure strain of the real diffusive. Pdf speckle tracking and interferometric processing of. Automated speckle interferometry of double stars meter telescope at kitt peak national observatory figure 2.
We present a speckle interferometry code for solar data taken with the help of an adaptive optics ao system. Electronic speckle pattern interferometry espi is becoming a very common test and measurement tool among industrial users. Material testing by computer aided speckle interferometry. Spatial phase shifting sps technique is useful for extracting quantitative displacement data from the system with only two.
This would also reduce many of the errors inherent in espi. Introduction the speckle interferometry is a favorite professional tool for measuring double stars. Electronic speckle pattern interferometry espi espi on the other hand, records the surface displacement of an object in response to the applied force. Speckle interferometry with midsized amateur telescope.
Speckle interferometry experiments with a digital photocamera. We introduce an efficient tool, the interimage distance, to evaluate the speckle dynamics, and the concept of speckle rate sr, in hz to quantify this dynamics. With improvements in image quality it has the potential. Theory and applications results from a bottomup approach and is original in several ways. Speckle interferometry and correlation applied to large. To fulfill these requirements our department developed the optics, electronics and software for our speckle interferometry observations. Custom software modules written by teiche consisted of a run manager, scheduler, database, andor emccd camera control, and monitorlogger. Pdf a doubleexposure speckle photographic technique has been widely used in various fields of optical. Measurement principles of espi dantec dynamics precision.
Wang department of civil engineering university of new mexico albuquerque, nm 871 introduction the fracture of rock and concrete is characterized by the formation and propagation of the fracture process zone. Trends in surface roughness 409 for obvious commercial reasons, source code is rarely available to users, and by the time queries have been filtered through sales engineers and office staff it is often very difficult to establish exactly how a particular parameter is calculated or even defined figure 4. A comparison between combined speckle interferometry speckle correlation and updating the reference image, submitted for. Allfiber spectrometer based on speckle pattern reconstruction brandon redding, sebastien m. Using an electronic speckle interferometry for measurement of a stressdeformation state of elastic bodies and structures. Squeezing interferometry for optical phase extraction in digital speckle pattern interferometry. This experiment aims at understanding this concept of speckle interferometry and to illustrate the realization of an experimental setup that can visualize small deformations of a scattering object. The software for the image processing, phase calculation, fringe analysis, phase. How nasa engineers are using interferometry to test the feasibility of a warp drive. Simultaneous acquisition of 3d shape and deformation by. Mar 28, 2016 introduction to speckle interferometry techniques. Electronic speckle pattern interferometry espi is an optical technique which enables interferometric measurements of surface displacements on almost any. Wyant chapter 18 page 14 of 15 block diagram of electronic sequence of espi system. Laser speckle contrast imager moorflpi2 moor instruments.
Jul 15, 2008 we present a speckle interferometry code for solar data taken with the help of an adaptive optics ao system. Electronic speckle pattern interferometry espi non. A software package for speckle interferometry of adaptive. Speckle interferometry of open cluster binaries and multiples 27 of spectral classes using classical photometry, which would a. Budinichlecture hall winter college on optics 2017. Electronic speckle pattern interferometry espi fea validation. 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 experiments with a digital photocamera maurizio vannonia and giuseppe molesinib istituto nazionale di ottica applicata, largo e. 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. Pramod k rastogi ed measurement science and technology. They can be divided into the shiftandadd image stacking method and the speckle interferometry methods. The electronic speckle pattern interferometry espi method has been adapted for analyzing mechanical and thermal properties of thin metallic. A pignal to noise optimization algorithm for speckle interferometry applications g.
Four telescope linkup creates worlds largest mirror by katia. Slettemoen the foundation of scientific and industrial research, n7034 nth, trondheim, norway received january 21, 1985. Calvo department of optics, complutenseuniversity of madrid 17thfebruary 2017, 11. Software house international how is software house. Fermi 6, 50125 firenze, italy received 12 september 2003. Electronic speckle pattern interferometry espi is a fast developing whole field optical technique widely used for measuring displacement components, their derivatives, surface roughness, shape. Because of the ease with which the vibrations and small displacements of objects can be studied in real time, the electronic speckle pattern interferometer is the ideal tool for the undergraduate laboratory as well as for classroom demonstrations. Recent developments and applications in electronic speckle. Wyant chapter 18 page 1 of 15 chapter 18 speckle interferometry basic phenomena applications outofplane surface vibration inplane displacement inplane vibration stellar speckle interferometry electronic speckle pattern interferometry. These proceedings reflect the work presented at the conference interferometry in speckle light. Effect of plasticity at outofplane electronic speckle. Speckle interferometry from eric weissteins world of physics. Electronic speckle pattern interferometry in characterizing. 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.
These techniques can dramatically increase the resolution of groundbased telescopes, but. A software package for speckle interferometry of adaptive optics corrected solar data we present a speckle interferometry code for. 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. There are two major classes among the instruments used daily by amateurs. 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. Nowadays, it deserves a chapter in almost every book that is published on speckle techniques, holographic interferometry or optical. Review of electronic speckle pattern interferometry espi. The visualisation is in the form of fringes on the image where each fringe normally represents a displacement of half a wavelength of the light used.
By using software program imagej program, the values of the mean intensity. Popoff, and hui cao department of applied physics, yale university, new haven, connecticut 06520, usa hui. Speckle interferometry is a method for attainment high angular resolution using full aperture of the large telescope. Pdf speckle interferometry as a tool for fine measurements. The moorflpi2 blood flow imager uses the laser speckle contrast technique to deliver realtime, highresolution blood flow images, providing outstanding performance in a wide range of preclinical and clinical research applications. 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. Speckle interferometry is a highly sensitive tool used for making fullfield, noncontact measurements of surface properties at the microscale. A signal to noise optimization algorithm for speckle. Dec 10, 20 the electronic speckle pattern interferometry espi method has been adapted for analyzing mechanical and thermal properties of thin metallic, polymer and composite films, metallized structures in. Speckle interferometry allows to measure static or dynamic displacement maps that occur on. Jacquot nanophotonics and metrology laboratory, swiss federal institute of technology, ch1015 lausanne, switzerland abstract. Speckle interferometry definition of speckle interferometry. Compared to the speckle photography method, speckle interferometry is more sensitive.
Pulsed lasers in electronic speckle pattern interferometry t. Espi can be used for stress and strain measurement, vibration mode analysis and nondestructi. Allfiber spectrometer based on speckle pattern reconstruction. Introduction to speckle interferometry techniques youtube. Electronic speckle pattern interferometry espi sciencedirect. Electronic speckle pattern interferometry wikipedia. On the basis of an analysis of the noise in sawtooth fringes a figure of merit is defined and measured for various inplane and outofplane sensitive electronic speckle pattern interferometry configurations. This leads to a series of interferometric dynamic measurement techniques based on highspeed imaging. Gathering and processing a terabyte of data during a speckle interferometry run in an orderly, reasonably errorfree manner by human operators was difficult as explained by teiche 2014. In order to measure various physical quantities at any instant, highspeed camera is adopted in various interferometric techniques to satisfy the nyquist sampling theorem along time axis.909 9 156 661 36 1367 1351 545 687 1131 1326 269 1327 974 1061 651 628 558 996 979 320 845 1496 301 440 1141 11 460 1122 1069 154 707 1248 778 920 1365 770 918 283 753 987 223 536 890 91 119 1186 819