Use of spatial phase shifting technique in digital speckle pattern interferometry (DSPI) and digital shearography (DS)

Bhaduri, Basanta; Mohan, N. Krishna; Kothiyal, M. P.; Sirohi, R. S.

doi:10.1364/oe.14.011598

Cited by 96 publications

(50 citation statements)

References 12 publications

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“…In order to avoid such problems, a new method that can analyze phenomena by the minimum number of sheets of speckle patterns and that does not use any higher-speed camera has been required. [11][12][13][14][15] Generally, there are two kinds of analysis methods. 11 One is the method that would directly analyze speckle patterns.…”

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confidence: 99%

“…[11][12][13][14][15] Generally, there are two kinds of analysis methods. 11 One is the method that would directly analyze speckle patterns. 16,17 The other one is the method that analyzes the specklegram produced from speckle patterns.…”

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confidence: 99%

“…[11][12][13][14][15][16][17] The total deformation information is given from the difference between the phase maps of each speckle pattern. The idea of this analysis method is generally the same as the off-axis digital holography technology.…”

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confidence: 99%

“…Furthermore, intensity distributions shown in Eqs. (10) and (11) are filtered in order to obtain specklegrams concerning the cosine and the sine components as Filtered[SG 1 ] and Filtered[SG 2 ], respectively. In this filtering processing, 2-D band pass width is decided by an operator.…”

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Improvement of measuring accuracy of spatial fringe analysis method using only two speckle patterns in electronic speckle pattern interferometry

Arai

2014

Opt. Eng

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Abstract. 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. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Improvement of measuring accuracy of spatial fringe analysis method using only two speckle patterns in electronic speckle pattern interferometry

Arai

2014

Opt. Eng

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“…Thirdly, the speckle fringe patterns which will reflect the underlying defect can be displayed in realtime. Compared with the spatial phase shifting techniques using a phase mask [3,4] which are at the sacrifice of a weakened light intensity, the current technique is a light intensity loss-free method.* …”

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A novel phase shift technique in shearography for NDT

Liu

Gao

2010

EPJ Web of Conferences

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Abstract:Digital shearography (DS) is a whole-field non-contacting optical method for nondestructive testing (NDT) of subsurface flaws and strain measurement. In this paper, we describe a novel phaseshifting technique in DS for nondestructive evaluation (NDE) and NDT of quasi dynamic behaviour of objects subject to varying loads. A Wollaston lens, a precise wave plate device and a polariser are employed to introduce constant phase differences between two shearing wavefronts. The wave plate device is in front of the polariser, which has a transmissive wavefront distortion of less than 1/8 wavelength. Phase difference can be adjusted by rotating the polariser. The rotation for angle adjusting can be easily carried out according to the requirement of the phase shifting. In this technique, the phase shifting is performed only on the static images of the object before deformation or loading. By setting the angle of the polariser to 0º, -60ºand 60º, three speckle patterns with the defined phase differences are captured, and are referred to as initial speckle patterns I1,0, I1,-60 and I1,60. Afterwards, the polariser is reset to 0º before loading. The speckle pattern I0 is treated as a base pattern, and will be subtracted from the subsequent speckle patterns which are captured in the quasi dynamic deformation process.During the quasi dynamic deformation process, the optical path and the entire optical set-up will be kept unchanged, and a series of speckle patterns (I m,0 , m=2,3,…..) which carry the deformation information will be quickly captured. In the meantime, fast image subtractions will be performed. The speckle fringes (I m,0 -I 1,0 ) will be displayed in real-time. In detailed post-processing, phase of differences method (PDM) [1] is used to extract phase information from the speckle images Im,0 -I 1,0 , I 1,0 , I 1,-60 and I 1,60 . Specifically, when a three phase step technique is employed, the phase of the fringe pattern (Im,0-I1,0) can be calculated from (I m,0 -I 1,0 )+ I 1,0 -I 1,-60 , (I m,0 -I 1,0 ), and (I m,0 -I 1,0 )+ I 1,0 -I 1,60 . Because this temporal phase shifting is not performed in the deformation process, the technique is suitable for NDT and NDE of quasi dynamic deformation behaviour of an object.The technique only requires three speckle patterns with phase differences prior to the object deformation. When a varying or quasi dynamic load is applied on the object, no physical phase shifting is needed to be conducted when sequential speckle patterns are recorded by a digital camera during the deformation process. Compared with the (5, n) temporal phase shifting techniques [2] using a PZT driver, the proposed technique has three main advantages. Firstly, it does not need a tedious calibration process for phase shifting. Secondly, the optical set-up is relatively simple. Thirdly, the speckle fringe patterns which will reflect the underlying defect can be displayed in realtime. Compared with the spatial phase shifting techniques using a phase mask [3,4] which are at the sacrifice of a weakened ...

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Advances in Speckle Metrology

Joenathan

Sirohi

Bernal

2015

The Optics Encyclopedia

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The field of speckle metrology has seen a surge in development in the past 10 years owing to advancements in digital cameras and computing power. For instance, a variety of digital speckle correlation (DSC) processes can now be performed in almost real time and therefore speckle techniques has found applications in nondestructive testing (NDT), biology, and medicine. New techniques in terms of optical arrangements and in extracting phase data have been introduced for measuring out‐of‐plane and in‐plane motions in digital speckle interferometry (DSPI) and digital speckle shear interferometry (DSSPI). DSC, DSPI, and DSSPI have also been combined to extend the range of measurements. In addition, quantitative analysis in speckle interferometry has seen a plethora of new software developments for conducting real‐time, accurate, complicated, fast, and repeatable measurements with ease. In addition, different methods to process speckle fringes have made analysis equivalent to that of classical interferometry, yet can be applied to all types of real‐world specimen.

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Use of spatial phase shifting technique in digital speckle pattern interferometry (DSPI) and digital shearography (DS)

Cited by 96 publications

References 12 publications

Improvement of measuring accuracy of spatial fringe analysis method using only two speckle patterns in electronic speckle pattern interferometry

Improvement of measuring accuracy of spatial fringe analysis method using only two speckle patterns in electronic speckle pattern interferometry

A novel phase shift technique in shearography for NDT

Advances in Speckle Metrology

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