A robust phase extraction method for overcoming spectrum overlapping in shearography

Liu, Xiangwei; Yan, Ping; Wang, Yonghong

doi:10.37188/lam.2023.007

Cited by 4 publications

(2 citation statements)

References 28 publications

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“…In addition, it is used in the field of materials research to study material properties and develop new materials that are stronger and more durable. The advantages of shearography over other nondestructive techniques include its noninvasive nature, its accuracy and rapidity in measuring component surface deformation, and its versatility in application to many different areas [8]. Thermography is a nondestructive analysis technique that relies on infrared imaging.…”

Section: Introductionmentioning

confidence: 99%

Multimodal non-destructive techniques for composite inspection

Graziano¹,

Tortora²,

Vespini³

et al. 2023

Multimodal Sensing and Artificial Intelligence: Technologies and Applications III

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The analysis of innovative materials and processes stands at the frontier of a series of wide-ranging scientific problems and poses stimulating challenges from a scientific as well as technological point of view, by virtue of its connection with various industrial sectors, such as aerospace and aeronautics. In recent years, composite materials have found numerous applications due to their mechanical characteristics and properties, representing the evolution of materials science and technologies by fusing within them the best characteristics of multiple materials. The present work is focused on the characterization of composite materials, using non-destructive techniques (NDT), to check different kinds of defects eventually present for a quality control of the object under observation. Shearography and thermography are used as nondestructive methods. The former, is an optical interferometric method for the detection of surface or sub-surface defects, the latter is a diagnostic technique that, by measuring the infrared radiation emitted by a body, allows to determine its surface temperature and to understand the health status of the investigated object. The results of the shearography technique, including, are complementary to thermographic techniques and allow us to have a complete characterization of the object. Their use offers advantages related to visualization and testing of end products, as well as the noncontact nature, nondestructive and areal working principle, rapid response, high sensitivity, resolution, and accuracy.

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Section: Introductionmentioning

confidence: 99%

Multimodal non-destructive techniques for composite inspection

Graziano¹,

Tortora²,

Vespini³

et al. 2023

Multimodal Sensing and Artificial Intelligence: Technologies and Applications III

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“…Liu (2023) 11 proposed a highly relevant work in spatial phase-shift shearography. Often, there is spectrum overlap in the Fourier transform of the speckle, which severely affects the phase quality.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous orthogonal shearography using two pairs of parallel slits and a tetra-split lens

Lima

Barrera

Gonçalves

2023

Optical Measurement Systems for Industrial Inspection XIII

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There are a growing number of industrial applications for shearography, especially in non-destructive testing of composite materials. Its tolerance to hostile environments is probably the most relevant success factor for industrial applications. The introduction of carrier fringes for phase recovery, replacing temporal phase shift techniques, allows measurements with a single exposure for each loading state, making shearography even more robust. Some defects are better evident when the shearing direction is horizontal. Others are best viewed with a vertical shearing direction. Thus, it is desirable to inspect in both directions. Fortunately, the literature reports some configurations capable of using carrier fringes to perform simultaneous measurements in more than one shearing direction. These systems work well, but since they use a mask with circular holes, they require a high amount of light. An alternative is the use of a pair of oblong slits, which increases the amount of light captured. This paper extends the use of oblong slit pairs for simultaneous measurement in two orthogonal shearing directions. Two pairs of parallel oblong slits are arranged orthogonally on the system mask. Although the Fourier transform of the resulting signal at the camera sensor contains the desired signals as well as a crosstalk between the slit pairs. However, the mask can be designed in such a way that the orthogonal signals are separable. To promote shearing in orthogonal directions, a polymeric lens was sectioned, forming four quadrants of 90°. The quadrants were radially displaced and arranged so that each oblong slit covers only one quadrant of the lens. As a result, four laterally shifted images are formed, two of them with horizontal shearing and the other two with vertical shearing. A proof-of-concept prototype was developed and the first results were evaluated by the authors in the laboratory environment and are presented in this article. The paper also shows details of the resulting Fourier spectrum and the strategy used to separate the orthogonal components and recover the phase using carrier fringes. The performance of the prototype met expectations and validated the concept. Future works involve miniaturization of the prototype and tests in industrial environments.

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Photothermal vortex interferometer with azimuthal complex spectra analysis for the measurement of laser-induced nanoscale thermal lens dynamics

Dong,

Zhang,

Yang

et al. 2023

Review of Scientific Instruments

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A photothermal vortex interferometer (PTVI) is proposed to fill the gap of full-field measurement of the laser-induced nanoscale thermal lens dynamics of optical elements. The PTVI produces a multi-ring petal-like interferogram by the coaxial coherent superposition of the high-order conjugated Laguerre–Gaussian beams. The non-uniform optical path change (OPC) profile resulting from the thermal lens causes the petals of the interferogram at the different radii to shift by the different azimuths. To demodulate such an interferogram, an azimuthal complex spectra analysis is presented by using a camera with a pixelated multi-ring pattern written on its sensor to extract multiple azimuthal intensity profiles synchronously from the interferogram. Therefore, the OPC profile can be determined dynamically from the complex spectra of the azimuthal intensity profiles at the main frequency components. An analytical thermophysical model of the thermal lens is given, and the basic principle of the azimuthal complex spectra analysis is revealed. A proof-of-concept experiment is demonstrated using a N-BK7 glass sample heated by a pump laser. The results verified that the PTVI achieves the measurement accuracy of 47 pm with a standard deviation of 358 pm (3σ) and can be used for full-field measurement of the nanoscale OPC profile caused by the thermal lens dynamics. Due to the picometer-scale accuracy of the PTVI, the absorption coefficient and thermal diffusivity of the glass sample were determined to be A0 = 0.126 m−1 and D = 5.63 × 10−7 m2 s−1, respectively, which agree with the nominal ones of A0 = 0.129 m−1 and D = 5.17 × 10−7 m2 s−1. Although the PTVI is only suitable for measuring the rotationally symmetric OPC, it shows less computation burden and hardware complexity, and it is proved to be a highly sensitive and effective tool in studying optical, thermo-physical, and mechanical properties of optical elements.

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A robust phase extraction method for overcoming spectrum overlapping in shearography

Cited by 4 publications

References 28 publications

Multimodal non-destructive techniques for composite inspection

Multimodal non-destructive techniques for composite inspection

Simultaneous orthogonal shearography using two pairs of parallel slits and a tetra-split lens

Photothermal vortex interferometer with azimuthal complex spectra analysis for the measurement of laser-induced nanoscale thermal lens dynamics

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