1 August 1985 Holographic Fringe Linearization Interferometry For Defect Detection
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In normal double-exposure holography with impulse loading, it is very difficult to locate defects because fringe clutter, which is due to random motion between exposures, often dominates the fringe shifts caused by the presence of subsurface defects (cracks, disbonds, etc.). We attempted to simplify the defect location problem by developing a concept more amenable to automatic readout techniques. Our approach to incorporate this change is quite simple. We swing the object beam between the two exposures, which adds a linear fringe to the reconstructed image. Proper selection of the fringe frequency (angle of object beam swing) and the loading force creates a reconstructed image laced with linear fringes that have fringe shifts at the defect locations that are highly visible. We describe the theory of the process. Experiments performed with static load illustrate that the defect is seen as fringe shifts on a linear carrier. Both through cuts and rear-surface cuts in a metal test plate were used to simulate defects. We further show that the defects have characteristic Fourier signatures different from those of the carrier.
G. O. Reynolds, G. O. Reynolds, D. A. Servaes, D. A. Servaes, L. Ramos-Izquierdo, L. Ramos-Izquierdo, J. B. DeVelis, J. B. DeVelis, D. C. Peirce, D. C. Peirce, P. D. Hilton, P. D. Hilton, R. A. Mayville, R. A. Mayville, } "Holographic Fringe Linearization Interferometry For Defect Detection," Optical Engineering 24(5), 245757 (1 August 1985). https://doi.org/10.1117/12.7973572 . Submission:

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