Time-average subraction method in electronic speckle pattern interferometry

Lu, Bing-Rui; Yang, Xiangyang; Abendroth, Harald; Eggers, H.

doi:10.1016/0030-4018(89)90060-6

Cited by 24 publications

(6 citation statements)

References 1 publication

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“…We have recorded two time-averaged specklegrams of the vibrating plate. The intensity, if two time-averaged specklegrams are subtracted, is given by 17,18 )] cos[2(…”

Section: Time-average Dspimentioning

confidence: 99%

Application of plate vibration and DSPI in evaluation of elastic modulus

Kumar

Shakher

2008

SPIE Proceedings

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Due to change in the plate constants/plate stiffness which is a function of elastic modulus, change in natural frequencies takes place. At each natural frequency, the plate has a unique mode shape of vibration which can be easily differentiated from mode shapes at other natural frequencies. In this paper, a technique for the evaluation of the elastic modulus is proposed which is based on the vibration analysis of the plate using digital speckle pattern interferometry (DSPI) and Rayleight's method. Large numbers of experiments were conducted on square aluminium plate for the boundary condition; one edge is fixed and other edges free. The experimental result reveals that a single observation of frequency at first torsional mode is sufficient to evaluate the elastic modulus for all practical purposes. The evaluated experimental error was found to be less than 1%. Ease in sample preparation, simplicity in evaluation, non destructive nature of the DSPI and speed of DSPI has good prospect to evaluate elastic modulus of a material.

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“…We have recorded two time-averaged specklegrams of the vibrating plate. The intensity, if two time-averaged specklegrams are subtracted, is given by 17,18 )] cos[2(…”

Section: Time-average Dspimentioning

confidence: 99%

Application of plate vibration and DSPI in evaluation of elastic modulus

Kumar

Shakher

2008

SPIE Proceedings

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“…Two timeaveraged specklegrams of the vibrating plate are recorded. The intensity, if two time-averaged specklegrams are subtracted, is given by 4,19 I͑x,y ͒ϭ2A o A r ͉J 0 ͓͑2/ ͒␥w 0 ͑ x,y ͔͉͒…”

Section: Dspi Fringe Pattern Recordingmentioning

confidence: 99%

“…Time-average DSPI is a powerful tool for nondestructive evaluation of dynamic deformations. [1][2][3][4] But DSPI interferograms have inherent speckle noise. 1 The source of this noise is attributed to random interference between the coherent returns.…”

Section: Introductionmentioning

confidence: 99%

“…6 In one method, called the time-average subtraction method, a phase difference of /2 is introduced in the reference before subtraction. 4 In the other method, phase stepping and digital image processing were employed, where a maximum-minimum fringe scanning technique is used to increase fringe contrast and a normalized maximum-minimum scanning technique is used to reduce speckle noise. 7 The different methods investigated to reduce speckle noise in DSPI fringes are only partially successful.…”

Section: Introductionmentioning

confidence: 99%

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Study of various preprocessing schemes and wavelet filters for speckle noise reduction in digital speckle pattern interferometric fringes

2005

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A new filtering scheme is investigated for the removal of speckle noise in the recorded fringe pattern by a digital speckle pattern interferometric technique (DSPI). The scheme consists of a preprocessing scheme i.e., averaging, sampling, thresholding, and again averaging, followed either by a symlet or biorthogonal wavelet filter. The preprocessing scheme improves the contrast between the dark and bright fringes, and the implementation of the biorthogonal wavelet filter, which is symmetrical and purely linear in phase, solves the problem of border effect and discontinuity. The developed scheme is implemented on recorded fringe patterns of a vibrating cantilever beam and vibrating square plate with all ends fixed. The performance and effectiveness of the proposed scheme in reducing speckle noise is evaluated and compared in terms of reduction in speckle index and the improvement of the signal-to-noise ratio (SNR) of speckle interferograms. The new scheme has the ability to improve the speckle index and SNR significantly.Subject terms: digital speckle pattern interferometry; symlet wavelet filter; biorthogonal wavelet filter; speckle index; signal-to-noise ratio.

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“…In the electronic detection using digital speckle pattern interferometry (DSPI), the two exposures are independently handled and their subtraction removes the DC component [34]. Phase shifting techniques can be easily incorporated with DSPI systems and hence deformation maps can be presented digitally.…”

Section: (Iii) Speckle Interferometrymentioning

confidence: 99%

Lensless in-line digital holography for dynamic applications

Singh¹

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for spending their precious time with me and for the valuable tips. I am thankful to technicians of Photonics and Microsciences lab Mr. Koh Hai Tong and Grace Ho and all technicians of Micromachine lab for their helping attitude and support throughout the work. I would like to thank to NTU and SPIE of USA for providing the financial supports for presenting my research works in international conferences. I am also thankful to Ngee Ann AEM Centre of Innovation (NACOI) for providing the opportunity as industrial attachment student. I would like to express my gratitude to all my family members, specially my parents and my wife for their constant encouragement. Its my pleasure to express thanks to all my friends in NTU for the useful discussion and excellent company. Finally, I would like to acknowledge the financial support that I received from NTU during my studies in Singapore. i

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Time-average subraction method in electronic speckle pattern interferometry

Cited by 24 publications

References 1 publication

Application of plate vibration and DSPI in evaluation of elastic modulus

Application of plate vibration and DSPI in evaluation of elastic modulus

Study of various preprocessing schemes and wavelet filters for speckle noise reduction in digital speckle pattern interferometric fringes

Lensless in-line digital holography for dynamic applications

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