Vibration frequency measurement with speckle interferometry

Traditional speckle fringe patterns of electronic speckle pattern interferometry (ESPI) are obtained by adding, subtracting, or multiplying the speckle patterns recorded before and after the deformation. However, these speckle fringe patterns are of limited visibility, especially for addition and multiplication fringe patterns. We propose a novel method to obtain speckle fringe patterns of ESPI from undeformed and deformed speckle patterns. The fringe pattern generated by our method is of high contrast and has better quality than subtraction fringe. The new method is simple and does not require more computational effort. The proposed method is tested on the experimentally obtained undeformed and deformed speckle patterns. The experimental results illustrate the performance of this approach.

The knowledge of residual stresses allows a reliable prediction of structure performances evolution, such as service life [1-3]. In this paper, we develop a new method for residual stresses determination combining Electronic Speckle Pattern Interferometry (ESPI) with the machining of a groove. The internal stress field is perturbed as the depth of the groove is increased incrementally. The structure finds a new equilibrium state generating displacements which are measured using ESPI. This method was tested on an aluminium alloy AU4G plate treated locally by an ultrasonic shot-peening. The investigation of the images obtained with the phase shifting technique and fringe patterns, makes it possible to analyze, simultaneously, the stress profile along two directions: along the depth of the structure, and along the groove direction.

Video-based speckle interferometric methods such as electronic speckle pattern interferometry (ESPI) allow us to measure full-field surface deformation of a diffuse object. In this paper we show, in a first step, that the susceptibility of ESPI to noise can be substantially reduced [1] by synchronizing the optical interferometer and the object stressing system with the CCD image acquisition and processing system, and by performing what amounts to a repetitive sequence of rapid ESPI tests. In this manner, a stable fringe pattern can be obtained as long as the ambient noise is of sufficiently lower frequency than the video acquisition rate (typically 30 Hz). This scheme will be referred in this paper as reference-updating subtractive correlated ESPI to distinguish it from classical ESPI. We then take this issue further with a hybrid additive-subtractive decollated ESPI technique that will freeze out unwanted environmental noise of frequencies much higher than video rates [2], The basic principle of this proposed technique can be summed up as follows: (i) acquire speckle images containing information about the same two deformed object states in every frame of the image acquisition sequence, (ii) decorrelate the speckles between every frame, and (iii) compare every consecutive pair of speckle images to extract visible fringes corresponding to the two deformed states of the test object.

Anisotropic partial differential equation noise-reduction algorithm based on fringe feature for ESPI

The amplitude range for vibration measurement by time-average recording in electronic speckle pattern interferometry (ESPI) has been extended by sinusoidal phase modulation of the reference wave. The technique is, in part, similar to the reference wave modulation technique known from holography. The low resolution of the ESPI system results in a greater need for an extension of the measuring range. In addition, the technique is more convenient to use combined with ESPI, because of the instantaneous presentation of interferograms by this system. The modulation technique also provides information about the vibration phase. Fringe patterns illustrating applications of this technique are presented.

In conventional optical nondestructive evaluation (NDE) of structures using shearography or electronic speckle pattern interferometry (ESPI), results are typically provided in the form of fringe patterns or deformation contour plots. However, in order to fully automate the process of defect detection, it is desirable to obtain simpler results which are easier to interpret. We present here one such optical system based on additive–subtractive shearography/ESPI. This system processes additive–subtractive fringe patterns and provides the sizes and locations of defects such as disbonds in adhesively-bonded composite structures. This is achieved by exciting the structure under inspection using an acoustic stressing mechanism which sweeps a range of vibration frequencies of the structure. Since the defective areas of the structure have different mechanical properties from their neighboring regions, varying and complex fringe patterns are obtained at different stressing frequencies. We propose an algorithm which enables the automatic identification and selection of relevant additive–subtractive fringe patterns that pertain only to localized deformations associated with defects, and which excludes images that pertain to any overall modes of the entire structure. The algorithm also includes a pixel-by-pixel adjustable thresholding scheme which compensates for intensity variations due to nonuniform reflectivity from unpainted and dirty test objects. Morphological processing is then performed to extract the shapes of the defect from the processed fringe clusters. Various structures, from simple aluminum specimens with simulated defects to a complex honeycomb-based aviation repair patch specimen, have been successfully evaluated using this system.

In the current study, we used the method of electronic speckle pattern interferometry (ESPI) to measure polymerization shrinkage of composite resins. Standardized cavities were prepared and placed into the ESPI apparatus before the cavities were filled with composites (n=2) .The ESPI apparatus was constructed to measure the out-of-plane displacement of the resins surface during the polymerization. Experiments demonstrated that the ESPI technique was a viable method to measure the deformation of composite resins. It was responsive and sensitive to dimensional changes. We found that cavity shape, size and C- factor influenced the date of resins shrinkage. And the tooth deformation in response to polymerization of resins was measured by the ESPI too. We concluded that ESPI was a feasible method for assessing resins deformation induced by its polymerization shrinkage when it was bonded in tooth cavities. And the results were greatly influenced by the dimensions of cavities , or interface adhesive and so on. It could also measure the tooth deformation induced by shrinkage of bonded composite resins. We found that resins polymerization shrinkage date may overestimate shrinkage-induced tooth deformation.

International Journal of Computational Engineering ScienceVol. 04, No. 03, pp. 467-470 (2003) Testing and CharacterisationNo AccessSTATIC AND DYNAMIC CHARACTERIZATION OF MEMS VIA ESPIAndreas H. Foitzik, Wolfgang Kaese, Thomas Vogt, Michael Sommerer, and Serguei ArkhipovAndreas H. FoitzikUniversity of Applied Sciences Esslingen, Department for Mechatronics, Robert-Bosch-Str. 1, D-73037 Goeppingen, Germany Search for more papers by this author , Wolfgang KaeseUniversity of Applied Sciences Esslingen, Department for Mechatronics, Robert-Bosch-Str. 1, D-73037 Goeppingen, Germany Search for more papers by this author , Thomas VogtUniversity of Applied Sciences Esslingen, Department for Automotive Technology, Esslingen, Germany Search for more papers by this author , Michael SommererUniversity of Applied Sciences Esslingen, Department for Automotive Technology, Esslingen, Germany Search for more papers by this author , and Serguei ArkhipovMOSCOW AVIATION INSTITUTE (MAI), MOSCOW, Russia Search for more papers by this author https://doi.org/10.1142/S1465876303001538Cited by:2 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractGenerally unaltered surfaces stemming from IC- or MEMS-production (Micro Electro Mechanical Systems) cannot be investigated with ESPI (Electronic Speckle Pattern Interferometry) due to the lack of any interference from the extremely flat surfaces of devices made of silicon. In order to enable ESPI for such devices additional "rough" layers can be added to the MEMS surfaces, while these relatively "thick" layers alter the mechanical properties of such small devices considerably. Utilizing a new surface preparation technique (Goeppingen Procedure®) allows to create a nm-sized roughness onto the surfaces of MEMS, thus enabling interference originating from such altered surfaces and subsequently allowing ESPI.Static ESPI on commercially available micro-sized tilt-sensors as well as read-write head of a hard disk drive showed that elastic deformations can be determined with a lateral accuracy in the μm-range and an axial accuracy in the nm-range, respectively. The static investigations allowed the identification of defect sensors in terms of quality assurance. Dynamic ESPI on MEMS showed different normal modes as well as the dynamic behaviour at the occurence of the first and the second harmonic.Keywords:MEMSESPI - Electronic Speckle Pattern InterferometryGoeppingen Procedure References J. A. Leendertz, J. Phys. E (Sci. Instrum.) 3, 214 (1970). Crossref, Google Scholar H. Marwitz , Praxis Holographie ( Expert-Verlag , 1990 ) . Google ScholarP. Aswendt and R. Höfling, Measurement 23, S. 205 (1998). Crossref, Google ScholarD. Holsteinet al., Composite Structures 40, S. 257 (1998). Crossref, Google Scholar K. Hariri , Bruchmechanisches Verhalten jungen Betons: Laser-Speckle-Interferometrie und Modellierung der Rißprozeßzone ( Techn. Univ. Braunschweig , 2000 ) . Google ScholarZ. Yanget al., Optics and Lasers in Engineering 28(6), 443 (1997). Google Scholar Höfling, R.; Aswendt, P.; Liebig, V.; Brückner, H.: Synthesis of experiment and simulation in speckle interferometry: a medical application; Akademie Verlag Series in Optical Metrology, Vol. 2, S. 261-268, Berlin 1996 . Google Scholar Foitzik, A.H.; Kümmel, M.; Schmid, M.; Kaese, W.; Vogt, T.; Groth, P.; "ESPI on MEMS", 13.Intern. Wissenschaftlich-technische Konferenz SENSOR 2001, Sudak/Krim 2001 . Google Scholar FiguresReferencesRelatedDetailsCited By 2An Experimental Study of the Vibrational Characteristics of a Diamond Circular Blade Using Electronic Speckle-Pattern Interferometry and FEMMykhaylo Tkach, Yurii Halynkin, Arkadii Proskurin, Irina Zhuk and Volodymyr Kluchnyk et al.15 May 2021 | Acta Mechanica et Automatica, Vol. 15, No. 1Electronic Speckle Pattern Interferometry for Vibrational Analysis of Cutting ToolsPiotr Mrozek, Ewa Mrozek and Andrzej Werner17 July 2018 | Acta Mechanica et Automatica, Vol. 12, No. 2 Recommended Vol. 04, No. 03 Metrics History KeywordsMEMSESPI - Electronic Speckle Pattern InterferometryGoeppingen ProcedurePDF download

A comprehensive ESPI based system for combined measurement of shape and deformation of electronic components

The high resolution technique of electronic speckle pattern interferometry (ESPI) can be very useful in determining deformation of laboratory specimens and identifying initiation of failure. The in-plane ESPI theory is described and the fringe pattern of the processed ESPI image is analyzed to determine deformation and crack opening displacement. Fringes on the ESPI image represent lines of equal intensity, which relate to surface displacement. An ESPI system was constructed and calibrated for measuring uni-directional displacements. Several types of the experiments, such as uniaxial compression and fracture testing, were conducted to demonstrate the utility of ESPI.

The use of holographic interferometry (HI) has been available for whole field testing of components for nearly twenty years. As an experimental technique it was limited to a laboratory environment but with the incorporation of a pulsed laser the possibility existed to attempt this type of analysis on the component operating in its usual environment. This should have provided the scientific and engineering community with the necessary tool to investigate many different difficult problems. The reality is holographic interferometry consumed billions of dollars globally, produced few real results and interest dwindled. Why? A number of reasons have been proposed which include experimental difficulties, data reduction and cost. Combined with the vast research effort in holography, interest in the allied field of speckle interferometry developed a video based technique which could rival holographic interferometry. This technique known as electronic speckle pattern interferometry (ESPI)1 provided equipment with similar capabilities to holographic interferometry but used the television camera directly as the imaging transducer rather than the photographic system. However this technique, which overcame a number of the experimental problems of holographic interferometry, still did not find immediate favour as an analysis tool. The end user was still not hammering on the door of the research laboratories. Laser costs have reduced and supporting digital electronics have substantially reduced to the extent where fully ruggedised commercial ESPI equipment costs approximately $30-50K. This makes it comparable with other experimental analysis packages, the cost argument therefore no longer strictly holds. The availability of image processing computer's has enabled a great deal of research into automated fringe data reduction and analyis, this was reviewed at a recent symposium by the Fringe Analysis Special Interest Group 4. The final major problem now outstanding is the availability of a handA¢â‚¬â€?held portable instrument capable of providing the computer with suitable data. The work this paper reports is an effort in this direction, to produce such a system. The application areas envisaged are: (i) displacement measurement of strain fields (ii) vibration measurement of resonant objects (iii) vibration measurement of non-resonant conditions (iv) refractive index changes in fluids, eg convective heat and fluid flow.

Out-of-plane displacement measurement by electronic speckle pattern interferometry in presence of large in-plane displacement

High-resolution deformation measurement method, which requires only two speckle patterns in electronic speckle pattern interferometry, is proposed by using fringe analysis based on specklegram. In fringe analysis using the proposed optical system, a pair of real- and imaginary-part components concerning the deformation information is extracted from one speckle pattern by Fourier transform in the same manner as the off-axis digital holography processing. A specklegram is calculated as a fringe image by multiplying the components of the real and imaginary part of speckle patterns in order to perform a high-resolution deformation analysis. Then, the phase map concerning deformation is detected from the specklegram, and the influence of speckle noise is also reduced by shifting the component on frequency domain. Furthermore, the amplitude of the intensity distribution of speckle pattern is normalized in order to reduce the influence by speckle noise much more. It is confirmed that the accuracy of the deformation measurement is efficiently improved by the proposed noise reduction methods.

This PDF contains the errata for the paper, Evaluation of a scale-space filter for speckle noise reduction in electronic speckle pattern interferometry.

Measurement of dynamic crack tip displacement field by speckle photography and interferometry