Evaluation of noise in measurements with speckle shearography
TL;DR: In this paper, a method is proposed to evaluate the experimental noise in measurements with speckle shearography whenever it is in the range [−π, π] and the limits of the proposed method are assessed by applying it to phase maps with added noise.
About: This article is published in Mechanical Systems and Signal Processing.The article was published on 2019-03-01. It has received 15 citations till now. The article focuses on the topics: Shearography & Speckle pattern.
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TL;DR: By training the system using typical butterfly fringe patterns which are captured from bonding samples, the system can accurately identify the bonding defects on the cylindrical surface at a high success rate.
19 citations
TL;DR: It is found that the accuracy of the multi-damage localization is significantly enhanced by optimizing the process of damage feature extraction and data fusion, which guarantees providing robust multi- damage localization results.
6 citations
TL;DR: The evaluation method of quality of the speckle pattern in DSPI system is proposed, and the influence of the size of Speckle grain on the stability and contrast of speckel pattern is discussed.
Abstract: In order to detect the deformation and strain of materials accurately, the key is to obtain the phase information caused by dynamic loading in digital speckle pattern interferometry (DSPI). In this paper, the evaluation method of quality of the speckle pattern in DSPI system is proposed, and the influence of the size of speckle grain on the stability and contrast of speckle pattern is discussed. And then, the strain detection experiments of inactive and bioactive materials are provided with different aperture slit size under the same detection conditions. The size of speckle grain has an important influence on the quality of speckle pattern. For strain detection of inactive materials, using the small size of speckles can obtain higher quality speckle pattern under the condition of satisfying the Nyquist theorem and spectral separation. For active biomaterials, non-structural factors easily induce the instability of speckle pattern, which leads to the de-correlation of between pre-deformation and post-deformation speckle pattern. So the compromise between the stability and the information capacity of speckle images should be considered in the selection of speckle size. Experiments show that the optimum size of speckles used for strain detection active biomaterials is larger than that of inactive biomaterials under the same conditions in the same DSPI system.
4 citations
TL;DR: A new technique for structural damage identification using cubic spline interpolation based on the interpolation of modal rotations measured with speckle shearography is explored, yielding a good performance.
Abstract: This paper aims to explore a new technique for structural damage identification using cubic spline interpolation. The method is based on the interpolation of modal rotations measured with speckle shearography. In order to locate the damaged areas, we make use of the analytical derivative of the cubic spline function to compute the modal curvature, which is known to be very sensitive to damage. A comprehensive parametric study of the spatial sampling interval is carried out to find its influence on noise filtering. Furthermore, the identification quality dependency on the mode shape and respective noise is also examined. The results obtained with the proposed method show the consistency of the localizations. Additionally, the challenging tasks of identifying small and multiple damage are tackled, yielding a good performance.
3 citations
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2,782 citations
Book•
01 Jan 1982
TL;DR: Teaching Special Relativity Phys.
Abstract: The need for error analysis is captured in the book's arresting cover shot - of the 1895 Paris train disaster (also available as a wall poster). The early chapters teach elementary techniques of error propagation and statistical analysis to enable students to produce successful lab reports. Later chapters treat a number of more advanced mathematical topics, with many examples from mechanics and optics. End-of-chapter problems include many that call for use of calculators or computers, and numerous figures help readers visualize uncertainties using error bars. "Score a hit! ...the book reveals the exceptional skill of the author as lecturer and teacher...a valuable reference work for any student (or instructor) in the sciences and engineering." The Physics Teacher "This is a well written book with good illustrations, index and general bibliography...The book is well suited for engineering and science courses at universities and as a basic reference text for those engineers and scientists in practice." Strain, Journal of the British Society for Strain Measurement
2,264 citations
Book•
28 Apr 1998
TL;DR: Methods for Phase Unwrapping, Phase Data, Quality Maps, Masks, and Filters, and Minimum-Norm Methods.
Abstract: Introduction to Phase Unwrapping. Line Integrals, Residues, and 2-D Phase Unwrapping. Phase Data, Quality Maps, Masks, and Filters. Path-Following Methods. Minimum-Norm Methods. Comparisons and Conclusion. Appendices. Index.
1,575 citations
Book•
27 Dec 2004
TL;DR: In this paper, the Fourier Transform is used for the reconstruction of digital Holograms, and the convolutional approach is used to reconstruct the Holographic Histogram.
Abstract: Preface.1 Introduction.1.1 Scope of the Book.1.2 Historical Developments.1.3 Holographic Interferometry as a Measurement Tool.2 Optical Foundations of Holography.2.1 Light Waves.2.2 Interference of Light.2.3 Coherence.2.4 Scalar Diffraction Theory.2.5 Speckles.2.6 Holographic Recording and Optical Reconstruction.2.7 Elements of the Holographic Setup.2.8 CCD- and CMOS-Arrays.3 Digital Recording and Numerical Reconstruction of Wave Fields.3.1 Digital Recording of Holograms.3.2 Numerical Reconstruction by the Fresnel Transform.3.3 Numerical Reconstruction by the Convolution Approach.3.4 Further Numerical Reconstruction Methods.3.5 Wave-Optics Analysis of Digital Holography.3.6 Non-Interferometric Applications of Digital Holography.4 Holographic Interferometry.4.1 Generation of Holographic Interference Patterns.4.2 Variations of the Sensitivity Vectors.4.3 Fringe Localization.4.4 Holographic Interferometric Measurements.5 Quantitative Determination of the Interference Phase.5.1 Roleof Interference Phase.5.2 Disturbances of Holographic Interferograms.5.3 Fringe Skeletonizing.5.4 Temporal Heterodyning.5.5 Phase Sampling Evaluation.5.6 Fourier Transform Evaluation.5.7 Dynamic Evaluation.5.8 Digital Holographic Interferometry.5.9 Interference Phase Demodulation.6 Processing of the Interference Phase.6.1 Displacement Determination.6.2 TheSensitivity Matrix.6.3 Holographic Strain and Stress Analysis.6.4 Hybrid Methods.6.5 Vibration Analysis.6.6 Holographic Contouring.6.7 Contour Measurement by Digital Holography.6.8 Comparative Holographic Interferometry.6.9 Measurement Range Extension.6.10 Refractive Index Fields in Transparent Media.6.11 Defect Detection by Holographic Non-Destructive Testing.7 Speckle Metrology.7.1 Speckle Photography.7.2 Electronic and Digital Speckle Interferometry.7.3 Electro-optic Holography.7.4 Speckle Shearography.Appendix.A Signal Processing Fundamentals.A.1 Overview.A.2 Definition of the Fourier Transform.A.3 Interpretation of the Fourier Transform.A.4 Properties of the Fourier Transform.A.5 Linear Systems.A.6 Fourier Analysis of Sampled Functions.A.7 The Sampling Theorem and Data Truncation Effects.A.8 Interpolation and Resampling.A.9 Two-Dimensional Image Processing.A.10 The Fast Fourier Transform.A.11 Fast Fourier Transform for N!= 2n.A.12 Cosine and Hartley Transform.A.13 The Chirp Function and the Fresnel Transform.B Computer Aided Tomography.B.1 Mathematical Preliminaries.B.2 The Generalized Projection Theorem.B.3 Reconstruction by Filtered Backprojection.B.4 Practical Implementation of Filtered Backprojection .B.5 Algebraic Reconstruction Techniques.C Bessel FunctionsBibliographyAuthor IndexSubject Index.
539 citations
TL;DR: Two approaches are developed on the extraction of phase and phase derivatives from either phase-shifted fringe patterns or a single carrier fringe pattern based on the best match between the fringe pattern and computer-generated windowed exponential elements.
Abstract: Fringe patterns in optical metrology systems need to be demodulated to yield the desired parameters. Time-frequency analysis is a useful concept for fringe demodulation, and a windowed Fourier transform is chosen for the determination of phase and phase derivative. Two approaches are developed: the first is based on the concept of filtering the fringe patterns, and the second is based on the best match between the fringe pattern and computer-generated windowed exponential elements. I focus on the extraction of phase and phase derivatives from either phase-shifted fringe patterns or a single carrier fringe pattern. Principles as well as examples are given to show the effectiveness of the proposed methods.
495 citations