High-speed digital processing of electro-optic holography images for a quantitative analysis

Spagnolo, Giuseppe Schirripa; Ambrosini, Dario; Paoletti, Domenica; Borghi, Riccardo

doi:10.1088/0150-536x/28/3/005

Cited by 20 publications

(9 citation statements)

References 17 publications

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“…From each phase map, a value of the diffusion coefficient D can be deduced from parameter t 1 , t 2 , w by Eq. (27). The distance w was automatically computed in the following way.…”

Section: Resultsmentioning

confidence: 99%

“…(27) has several important features. Only three directly measurable parameters are involved ( 1 t , 2 t and w ).…”

Section: Determination Of Diffusion Coefficient In Mass Transfermentioning

confidence: 99%

“…The phase calculated by equation (34) is wrapped in the range π − to π + 26,27 . Figure 4 shows a conceptual illustration of the process used to obtain the phase map of the local phase shift.…”

Section: Phase Analysismentioning

confidence: 99%

See 2 more Smart Citations

Diffractive optical element based sensor to measure small diffusion coefficients

Spagnolo

Ambrosini²,

Paoletti

2003

SPIE Proceedings

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In studying hydrodynamic instabilities between two miscible fluid mixtures one often faces the problem of assigning a reliable value to very small diffusion coefficients. As for diffusion between two binary mixtures such as water and glycerin, water and salt, etc., no complete data are available in the literature. In order to measure small diffusion coefficients of miscible fluids, in this paper we propose an improved version of digital projection moiré. The system uses a fringe generator realized with a diffractive optical element (DOE). The fringe patterns are projected on the bottom of a ground glass plate. The phase object (diffusion cell) is placed in front of the ground glass (in other words, in front of the fringe pattern), which is imaged by a digital video camera. Grating patterns, during the evolution of diffusion phenomena, are captured by a CCD camera and stored in a computer at different times. With the aid of Fast Fourier Transform (FFT) and signal demodulating techniques, the images are processed to obtain the diffusion coefficients. The theoretical basis of the device is presented. Furthermore, we report some experiments conducted for demonstrating the usefulness of the system. ) · 0277-786X/03/$15.00 244 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/20/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Proc. of SPIE Vol. 5191 245 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/20/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx*

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“…From each phase map, a value of the diffusion coefficient D can be deduced from parameter t 1 , t 2 , w by Eq. (27). The distance w was automatically computed in the following way.…”

Section: Resultsmentioning

confidence: 99%

“…(27) has several important features. Only three directly measurable parameters are involved ( 1 t , 2 t and w ).…”

Section: Determination Of Diffusion Coefficient In Mass Transfermentioning

confidence: 99%

See 1 more Smart Citation

Diffractive optical element based sensor to measure small diffusion coefficients

Spagnolo

Ambrosini²,

Paoletti

2003

SPIE Proceedings

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show abstract

“…[8][9][10][11][12] Phase unwrapping is carried out to convert the discontinuous phase to a continuous one by adding or subtracting 2 to the wrapped phase. This removes the discontinuities to yield a continuous phase map related to the measurement parameter.…”

Section: Principle Of the Methods "Based On Ref 7…mentioning

confidence: 99%

Fourier transform method for measurement of thin film thickness by speckle interferometry

Karaaliog̃lu

Skarlatos

2003

Opt. Eng

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The surface profile of an Al thin film and its thickness are observed by electronic speckle pattern interferometry (ESPI). The Michelson interferometer is used as our basic interferometric system to obtain interference fringes on a CCD camera. These interference fringes depend on the path differences due to the surface contours of the thin film. The interference fringes are analyzed with the fast Fourier transform method and a wrapped phase is obtained. An unwrapping procedure is used to obtain a continuous phase. Results on thickness measurement are presented.

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“…In recent years, the phase unwrapping problem has been widely studied [1][2][3][4][5][6][7][8][9][10][11] . However, one of the most robust techniques for phase unwrapping is the least-squares method.…”

Section: Weighted Phase Unwrappingmentioning

confidence: 99%

Unwrapping weighted algorithm in fringe projection 3D profilometry

Spagnolo

Majo

Ambrosini

et al. 2003

Optical Information Systems

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In this paper we present an unwrapping weighted algorithm to analyze phase maps obtained by means of fringe projection 3-D profilometry. The proposed method is a variant of the iterative weighted phase unwrapping developed by Ghiglia and Romero 1 . In fringe projection method, the phase distribution of the measured fringe pattern includes information on the surface height variation of the object. Phase unwrapping is a critical step in any phase measurement technique in which the height of an object is obtained from phase data. Indeed, when a complex object is measured, abrupt and irregular changes in the measured surface may result in local shadows. In shadow areas the observed phase data are uncertain or misleading. These zones yield "lacunae", in the reconstruction of the 3D model. In this work we propose a new phase unwrapping method able to mitigate the "lacunae" problem by interpolation of phase data. The case of an image containing regions without phase information (for fringe projection 3-D profilometry the zones in shadows), is treated, in our algorithm, in the following manner: (a) phase inconsistencies are handled by excluding invalid pixels from the unwrapping process though the assignment of zero-valued weights; (b) an unwrapped phase map is obtained by an algorithm based on robust, path-independent method of phase unwrapping; (c) the lacks (zones of phase inconsistencies) are eliminated by means of an suitable procedure of interpolation; (d) a rewrapping procedure is used to obtain wrapped phase map without initial inconsistencies; (e) a new unwrapped phase map is obtained by the same algorithm used in step-b but with weights different from zero. The robustness of the proposed phase-unwrapping method is then tested computationally and experimentally and its enhancement is proven through the simulation and experimental results. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/20/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Proc. of SPIE Vol. 5202 241 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/20/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

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High-speed digital processing of electro-optic holography images for a quantitative analysis

Cited by 20 publications

References 17 publications

Diffractive optical element based sensor to measure small diffusion coefficients

Diffractive optical element based sensor to measure small diffusion coefficients

Fourier transform method for measurement of thin film thickness by speckle interferometry

Unwrapping weighted algorithm in fringe projection 3D profilometry

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