Speckle Interferometry

Ennos, A. E.

doi:10.1007/978-3-662-43205-1_6

Cited by 45 publications

(32 citation statements)

References 28 publications

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“…In order to derive the deformation resolution in the object plane, the maximal image magnification M is calculated with the speckle diameter σ, the laser wavelength λ and the f -number F by [13] …”

Section: Deformation Resolutionmentioning

confidence: 99%

Precise In-Process Strain Measurements for the Investigation of Surface Modification Mechanisms

Tausendfreund

Stöbener

Fischer

2018

JMMP

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Abstract:The question, how certain surface layer properties (for example, hardness or roughness) can be specifically influenced in different manufacturing processes, is of great economic interest. A prerequisite for the investigation of the formation of surface layer properties is the metrological assessment of the material stresses during processing. Up to now, no commercial in-process measuring system exists, which is able to determine material stresses in the form of mechanical strains in high-dynamic manufacturing processes with sufficient accuracy. A detailed analysis of the resolution limits shows that speckle photography enables deformation measurements with a resolution in the single-digit nanometer range. Thus, speckle photography basically offers the potential to measure material stresses during processing. Using the example of single-tooth milling, the applicability of speckle photography for in-process stress measurements is demonstrated. Even in such highly dynamic manufacturing processes with cutting speeds up to 10 m/s, the absolute measurement uncertainty of the strain is less than 0.05%. This is more than one order of magnitude lower than the occurring maximal strain. Therefore, speckle photography is suitable for characterizing the dynamic stresses and the material deformations in manufacturing processes.

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Section: Deformation Resolutionmentioning

confidence: 99%

Precise In-Process Strain Measurements for the Investigation of Surface Modification Mechanisms

Tausendfreund

Stöbener

Fischer

2018

JMMP

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“…The exact relationship between M and the investigated physical quantity is beyond the scope of the present investigation. SI aims to render this relationship as simple and univocal as possible, by making M proportional to a particular projection of the displacement vector or to its partial derivatives, depending on the chosen geometry of the optical arrangement, [1][2][3]. In regard of sensitivity, density of interrogated points, flexibility in the choice of the measurand and capacity of real time visualization, interferometry is overwhelmingly preferred to image correlation.…”

Section: Extracting the Phase Of Interferometric Signalsmentioning

confidence: 99%

“…The volumes inside which it is reasonable to make inter-and extrapolation calculations are as small as the average size of isolated speckle grains, i.e. of the order of 3x3x100 Pm 3 for visible wavelengths and usual apertures [1][2][3]. The speckle fluctuations, the existence of phase uncertainties or singularities, the non-linearity and nonstationary behaviour of Eq.…”

Section: The Status Of Simentioning

confidence: 99%

Phase extraction in dynamic speckle interferometry: proposal of a road map

Equisa

Jacquot

2010

EPJ Web of Conferences

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Abstract. Of all the two-beam interference patterns, the ones obtained in speckle interferometry (SI) are the most difficult to be phase-demodulated. Many solutions exist in classical smooth-wave interferometry and alike techniques, both in static and dynamic regimes. In SI, the three constituents of the signals -the background, the modulation and the phase -are all basically random variables. There is no way to make a prediction of the evolution of these variables outside the small size of the correlation volumes -the volumes defined by the average speckle grain. To some extent, the classical methods can be adapted to SI. Here, we prefer to develop a series of new processing tools tailored to the specificities of the dynamic SI signals: the cooperative use of the empirical mode decomposition (EMD), the Hilbert transform (HT), and the three dimensional piecewise processing (3DPP) for recovering efficiently the phase of these signals.

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“…The only feasible way to increase the optical efficiency of the interferometer is to increase P s, the power conveyed by a single speckle. Because the total reflected power Poi Ro is distributed over a 27t solid angle containing 50 % bright speckles and 50 % dark spots, (2) where e denotes the average solid angle of a single speckle [4]: (3) Here, do is the diameter of the illuminated spot, which should be reduced to the diffraction limit to obtain the largest possible speckles. For a Gaussian beam [5], …”

Section: Optical Efficiencymentioning

confidence: 99%