In-Plane Strain Measurement By Digital Phase Shifting Speckle Interferometry

Maas, Ad A. M.; Vrooman, Henri A.

doi:10.1117/12.962751

Cited by 4 publications

(3 citation statements)

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“…The irradiance g(x, y) of the interference fringes can be expressed as g(x, y) = a(x, y) + b(x, y) cos[ 2t (f,x +fy ) + 4(x, y) I (4) =a(x,y)+c(x,y)exp[i(2(fx+f))]+c*(x,y)exp[j(2(fx+f,,))] (5) where a(x, y) is the background irradiance, b(x, y) is the fringe contrast,J andJ are the spatial frequencies of the carrier fringe in the x and y directions respectively, (x, y) is the phase of the fringe, c(x, y) = [ b(x, y) I 2 1 exp[ i (x, y)] and denotes a complex conjugate.…”

Section: Fourier Transform Methodsmentioning

confidence: 99%

<title>Simultaneous measurements of vector components of displacement by ESPI and FFT techniques</title>

Takatsuji

Oreb

Farrant

et al. 1995

Interferometry VII: Techniques and Analysis

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To measure a number of components of displacement with electronic speckle pattern interferometry (ESPI), multiple interferograms are usually captured in succession for different sensitivity vectors. Simultaneous measurement of a number of orthogonal components of displacement using ESPI can be carried out by application of the Fourier transform method (FTM). An object is illuminated by several object beams, and the scattered light is combined with one reference beam to form a first speckle image. After providing different tilts to the object beams, a second speckle image is recorded. A third speckle image is then recorded with the object loaded. The difference of the first and second images contains a set of straight carrier fringes. The difference of the first and third images contains a corresponding separate set of modulated carrier fringes due to the loading. The Fourier transforms of these two difference images show multiple peaks which correspond to the carrier fringes of the different object beams. By appropriately masking the corresponding peaks in the two Fourier transforms ,the different sets of carrier fringes for the loaded and unloaded object configurations, can be separated. The phase corresponding to the different orthogonal components of displacement can then be retrieved from the ratios of the real to imaginary parts of the two inverse Fourier transforms of each filtered peak. An example of the measurement is presented.

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Section: Fourier Transform Methodsmentioning

confidence: 99%

<title>Simultaneous measurements of vector components of displacement by ESPI and FFT techniques</title>

Takatsuji

Oreb

Farrant

et al. 1995

Interferometry VII: Techniques and Analysis

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“…u O ðx; y; z H Þe −j2πððr x þk x R Þxþðr y þk y R ÞyÞ dxdy ¼û R const U O ðr x þk x R ; r y þk y R Þ; (5) indicating proportionality to U O ðr x ; r y Þ linearly shifted by ð−k x R ; −k y R Þ in the spatial frequency domain. When recording the hologram in the hologram plane z H by a CCD sensor, 1 thus retrieving a reconstruction of the wavefront u O ðx; y; z H Þ.…”

Section: Wavefront Reconstruction In Off-axis Digital Holographymentioning

confidence: 99%

Compensated, nonlinear weighted exponential average filtering for digital holography on rough surfaces

Brunn

2015

Opt. Eng

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The concept of exponential averaging of a reconstructed wavefront is extended by considering the full process of image formation in digital holographic microscopy (DHM), including object illumination, optical imaging, reference wave, and hologram sampling. Phase filtering by exponential averaging uses the whole capability of DHM to retrieve both the amplitude and phase of a wavefront. The aim is to apply the exponential filtering to the spatial distribution of the complex reflection coefficient of the object surface rather than to the whole orthoscopically reconstructed wavefront. To identify possible contributions to errors in the weighting of the exponential averaging, the phase measurement process of DHM is described as a signal transmission path. Accordingly, the orthoscopic wavefront needs to be compensated for both amplitude and phase of the illuminating wave and of the reference wave as closely as possible. As hologram sampling can introduce spectral amplitude attenuation, its numerical compensation is also proposed. Finally, nonlinear amplitude weighting is proposed in exponential averaging. For a better understanding of the physical meaning of weighting and its particular importance for measuring rough object surfaces, the effect of object roughness on an imaged object wavefront is presented by the concept of optical convolution. Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/12/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Optical Engineering 084102-2 August 2015 • Vol. 54(8) Brunn: Compensated, nonlinear weighted exponential average filtering for digital holography. . . Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/12/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Optical Engineering 084102-6 August 2015 • Vol. 54(8) Brunn: Compensated, nonlinear weighted exponential average filtering for digital holography. . . Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/12/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Optical Engineering 084102-8 August 2015 • Vol. 54(8) Brunn: Compensated, nonlinear weighted exponential average filtering for digital holography. . . Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/12/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Optical Engineering 084102-12 August 2015 • Vol. 54(8) Brunn: Compensated, nonlinear weighted exponential average filtering for digital holography. . . Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/12/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

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“…Speckle pattern interferometry using a photographic method was first reported by Archbold et al 1 and further developed by Butters and Leendertz. 2 Electronic speckle pattern interferometry has found many applications in nondestructive evaluation, 3,4 mechanical stress analysis, 5,6 and vibration analysis. 7,8 In electronic speckle pattern interferometry the surface of an object is illuminated by laser light producing a speckled object beam which interferes with a coherent reference beam.…”

Section: Introductionmentioning

confidence: 99%

In-plane sensitive electronic speckle pattern interferometer using a diffractive holographic optical element

Jallapuram¹,

Healy²,

Mihaylova³

et al. 2011

American Journal of Physics

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In-Plane Strain Measurement By Digital Phase Shifting Speckle Interferometry

Cited by 4 publications

References 0 publications

<title>Simultaneous measurements of vector components of displacement by ESPI and FFT techniques</title>

<title>Simultaneous measurements of vector components of displacement by ESPI and FFT techniques</title>

Compensated, nonlinear weighted exponential average filtering for digital holography on rough surfaces

In-plane sensitive electronic speckle pattern interferometer using a diffractive holographic optical element

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