Although speckle interferometry techniques were developed years ago and are widely used for the visualization of the operating deflection shapes of vibrating surfaces, methods for accurate reconstruction of the observed deflection shape are still an active topic of research. The objects displacement results in an optical phase shift. This is done by applying phaseshifting techniques to speckle interferometry, which will quantitatively determine the phase of doubleexposure. Digital speckle pattern interferometry applied to a. Electronic speckle pattern interferometry, ist ein interferometrisches messverfahren zur. These techniques can dramatically increase the resolution of ground. Carlsson, digital measurement of three dimensional shapes using lightinflight speckle interferometry, optical engineering. If the inline pdf is not rendering correctly, you can download the. The latter can measure small displacement in micrometric level. This produces an interferometric speckle pattern that will be detected by sensor to count the change of the speckle pattern due to force given 9. Moorea department of physics, rollins college, holt avenue, winter park, florida 32789 received 6 april 2004. Pdf defect detection in metals using electronic speckle. Finite element contour map of predicted strain derivative distribution. List of papers this thesis includes the following papers.
This definition appears rarely and is found in the following acronym finder categories. 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. In the present work, application of digital speckle pattern interferometry dspi was applied for the measurement of mechanicalelastic and thermal properties of fibre reinforced plastics frp. A digital speckle pattern before deformation of an object is recorded in the mass storage device of a computer facility. The problems associated with electronic speckle pattern interferometry in the presence of ambient vibrations have been the subject of discussion for some time. However, the discussions usually center on methods to mitigate the effects of vibration either by isolation of thesystem or by limiting the sampling time of the detector 3. Speckle interference patterns need in any case a kind of further decoding step in order to become a source of useful information. Speckle inter9, ferometry is often subdivided into two distinct techniques. The visualisation is in the form of fringes on the image where each fringe normally represents a displacement of half. Evaluating the elastic modulus of bone using electronic. The espi system developed relies on the analysis of soundinduced vibration of the investigated surfaces. Pdf a michelson interferometer based espi system for static and vibration out of plane displacement measurements is presented. An application of digital image processing techniques to speckleshearing interferometry is described. Phase stepping shearography and electronic speckle pattern.
In its present form it rivals any current techniques for speed and ease of use. The noncontact and fullfield measurement allows the calculation of the three. 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. A mechanically stable laser diode speckle interferometer.
Electronic speckle pattern interferometry for vibrational analysis of. Digital speckle pattern interferometric technique was used to characterize the material constants poissons ratio and youngs modulus of the. View electronic speckle pattern interferometry research papers on academia. Analysis of laser speckle severity, granularity, and. Speckle pattern is a random granular pattern produced by the reflection of coherent light beam e. Application of electronic speckle pattern interferometry.
The interferometer is useful for visualizing the normal modes of vibrating objects as well as changes in index of. Defect detection in metals using electronic speckle pattern interferometry. Development and application of a fibre optic electronic. This paper refers to two wholefield, noncontact experimental techniques. Pdf electronic speckle pattern interferometry for vibrational. Combination of digital speckle pattern interferometry and. A present system consists of an imageshearing camera using a fresnel biprism of small angles and a digital tvimage processing facility. Electronic speckle pattern interferometry espi introduction electronic speckle pattern interferometry espi is an optical technique which enables interferometric measurements of surface displacements on almost any surface and material. The measurement is performed noncontact on the whole measuring area on nearly any material and component. The visualisation is in the form of fringes on the image where each fringe. It relies on the interference between diffusely reflected light from the test object and a reference beam.
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. Digital specklepattern interferometry systems for automatic measurement of deformations of a diffuse object are presented, which are based on a fringe scanning method with phaseshifted speckle interferograms. Introduction to speckle interferometry techniques youtube. Digital speckle pattern interferometry dspi and digital image correlation dic. Timeaveraged electronic speckle pattern interferometry in.
Digital speckle interferometry and related techniques k. Pdf an electronic speckle pattern interferometer suitable for use in an undergraduate laboratory is described. Inplane electronic speckle pattern shearing inter ferometry 405 ao x. Simple electronic speckle pattern interferometer espi. Electronic speckle pattern interferometry for vibrational analysis of cutting. Mod01 lec06 hologram interferometry, speckle methods duration. Espi can be used in arrangements where fringes will represent lines of either inplane or outofplane displacement.
Elektronische specklemusterinterferometrie wikipedia. Inplane electronic speckle pattern shearing interferometry. A portable electronic speckle pattern interferometer with. We propose a noncontact optical method to detect human wrist pulse, aiming at the precise determination of the temporal and spatial distributions of pulse. Digital speckle pattern interferometry and related techniques.
Holographic and speckle interferometry jones and c. Ong sanjeev solanki xinan liang xuewu xu data storage institute astar agency for science, technology and research singapore 117608, singapore email. Dspi, originally known as electronic speckle pattern interferometry, is an interferometry based method that allows achieving wholefield, noncontacting measurements of microscopic deformation 14. The wavelength is written on the top and also marked by the red line in the bottom scale. They can be divided into the shiftandadd image stacking method and the speckle interferometry methods.
Review of electronic speckle pattern interferometry springerlink. Introduction to speckle interferometry techniques experimental stress analysis an overview. The development of a simple electronic speckle pattern interferometer espi for the noninvasive, noncontact detection and characterization of earlystage damage of painted surfaces, like fracturing and layer separation, is reported. 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. Methodology the principle of speckle interferometry uses the ability of laser light of interference. The speckle pattern is optically mixed with a second coherent light field that is either another speckle pattern or a smooth light field. Espsi stands for electronic speckle pattern shearing interferometry. Phase shifting speckle interferometry for determination of. However it suffers from the lack of objective and efficient detection method. Phase stepping shearography and electronic speckle pattern interferometry d findeis, j gryzagoridis, m matlali department of mechanical engineering university of cape town, rondebosch, 7700, south africa tel. The former can measure 3d deformations in nanometric level. It has been stated as recently as 1989 thatdynamic speckle pattern interferometry is. Pdf a simple design for an electronic speckle pattern interferometer.
Electronic speckle pattern interferometry espi is a technique for fullfield displacement measurement and has been well accepted in. 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. Electronic speckle pattern interferometry research papers. Electronic speckle pattern interferometry espi is a wellknown application of the speckle effect. The method uses the spatialcarrier digital speckle pattern. Electronic speckle pattern interferometry is a wellknown experimental technique for fullfield deformation measurements. Methodology and results of these measurements are presented in this paper.
Dspi processes speckle patterns in a computer rather than with a frame grabber and analog electronics as in espi. Our global network of friendly and knowledeable distributors. A portable electronic speckle pattern interferometer with integrated topometric surface analysis j. Electronic speckle pattern interferometry espi is a nondestructive optical method for studying surface deformations. Pulse diagnosis is one of the four diagnostic methods of traditional chinese medicine. 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. An electronic speckle pattern interferometer suitable for use in an undergraduate laboratory is described. After object deformation an object point o is displaced by d to the point o. A simple design for an electronic speckle pattern interferometer thomas r. Vibration observation is a major application of digital specklepattern interferometry dspi, which is a variation on electronic specklepattern interferometry espi. Analysis of laser speckle severity, granularity, and anisotropy using the power spectral density in polarcoordinate representation desmond c. Timeaveraged electronic speckle pattern interferometry in the presence of ambient motion. Wyant chapter 18 page 14 of 15 block diagram of electronic sequence of espi system.
A new versatile electronic speckle pattern interferometer for. Osa deformation reconstruction by means of surface. Electronic speckle pattern interferometry springerlink. With improvements in image quality it has the potential to become the definitive tool for nondestructive testing.
Espsi electronic speckle pattern shearing interferometry. Electronic speckle pattern interferometry wikipedia. This interferometer can be built for a small fraction of the cost of a commercial version. Nowadays, there are a large number of interferometric systems that allow to monitor a large variety of physical parameters. Measurement of elastic and thermal properties of composite. Fringe pattern reference beam holographic interferometry electronic speckle pattern interferometry object beam these keywords were added by machine and not by the authors. Electronic speckle pattern interferometry espi and digital shearography have been shown to be of great value for the nondestructive testing of the integrity of materials and manufactured components. This process is experimental and the keywords may be updated as the learning algorithm improves. Digital holography dh is usually free of misinterpretation, but when an expression like imageplane digital. Electronic speckle pattern interferometry espi is an optical technique which enables interferometric measurements of surface displacements on almost any surface and material. This interferometer can be built for a small fraction of the cost of a commercial version and is simple and inexpensive to build and understand. Then, the speckle is interpreted as a statistical phenomenon. Electronic speckle pattern interferometry espi is becoming a very common test and measurement tool among industrial users.
The intensity is distributed according to a negativeexponential probability density function. Such optical techniques include speckle shearing interferometry for measuring surface. However, speckle interferometry has been thus far confined to the study of static deformation, or at most, periodic deformation in a timeaverage or timefrozen sense. This is a phenomenon that occurs when coherent light strikes an optically rough surface. In relation with this thermal strain measurement method using electronic speckle pattern interferometry methodology was tested in lithuania for application to the graphite. 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 specklepattern interferometry. Electronic speckle pattern interferometry espi has been widely used for vibration. Dspi needs a phaseshifting setup and rotating the whole device for 3d deformation. Theory and applications on free shipping on qualified orders. Allfiber spectrometer based on speckle pattern reconstruction.
The dantec dynamics elektronic speckle pattern interferometry espi systems are designed for complete three dimensional, full field and highly sensitive displacement and strain and stress analysis. Electronic speckle pattern interferometry espi espi on the other hand, records the surface displacement of an object in response to the applied force. Applications speckle pattern analysis provides a wide variety of applications. Electronic speckle pattern interferometry espi non. Pdf a simple design for an electronic speckle pattern. High speed electronic speckle pattern interferometry espi. Speckle patterns have high frequency phase data, which make it difficult to find the absolute phase of a single speckle pattern. The incident light scatters in all directions from the surface and these scattered waves interfere and form an interference. The incorporation of monomode fibre optics into an argon ion powered electronic speckle pattern interferometer espi is reported. Electronic speckle pattern interferometry espi, also known as tv holography, is a technique which uses laser light, together with video detection, recording. Vibrationobservation techniques for digital speckle.