13 June 2005 Experimental comparison of shearography and laser optical feedback imaging for crack detection in concrete structures
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Abstract
The metallic and concrete structures used in civil Engineering show their defects by the appearance of cracks. We report crack detection laboratory tests on a piece of armed concrete stimulated by acoustic waves. The feasibility of detecting non-emerging (hence invisible to a human observer) cracks is demonstrated. Our results show a good visual correlation between differential speckle interferometry, (a.k.a. shearography) and laser optical feedback imaging (LOFI). The advantages of shearography are its compacity, resolution and rapidity (it is a direct full view technique), but in this application, the information it provides is essentially qualitative. On the contrary the LOFI technique measures the difference of vibration amplitude on each side of the defect. Moreover its good sensitivity enables long-range measurement, but the image resolution and acquisition time depend on the tuning of scanning mirrors. The metallic and concrete structures used in civil Engineering show their defects by the appearance of cracks. We report crack detection laboratory tests on a piece of armed concrete stimulated by acoustic waves. The feasibility of detecting non-emerging (hence invisible to a human observer) cracks is demonstrated. Our results show a good visual correlation between differential speckle interferometry, (a.k.a. shearography) and laser optical feedback imaging (LOFI). The advantages of shearography are its compacity, resolution and rapidity (it is a direct full view technique), but in this application, the information it provides is essentially qualitative. On the contrary the LOFI technique measures the difference of vibration amplitude on each side of the defect. Moreover its good sensitivity enables long-range measurement, but the image resolution and acquisition time depend on the tuning of scanning mirrors.
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V. Muzet, V. Muzet, E. Lacot, E. Lacot, O. Hugon, O. Hugon, Y. Guillard, Y. Guillard, } "Experimental comparison of shearography and laser optical feedback imaging for crack detection in concrete structures", Proc. SPIE 5856, Optical Measurement Systems for Industrial Inspection IV, (13 June 2005); doi: 10.1117/12.611268; https://doi.org/10.1117/12.611268
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