This paper presents a novel technique for direct determination of derivatives of the displacement recorded by holographic interferometry. In the recording of a double exposure hologram, a set of relatively high frequency carrier fringes is coherently superimposed upon the displacement fringes by slightly changing the object beam direction, in addition to deforming the object. The resultant fringe pattern is a perturbed carrier fringe pattern, and the local fringe spacing directly determines displacement derivatives. Fringe spacing is accurately determined by measuring the separation of a pair of diffracted orders produced by a laser beam diffracted by the local carrier fringes.
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References
1.
TheocarisP.Moire fringes in strain analysis, 1969 (Pergamon Press, Oxford).
2.
ParksV. J.DurelliA. J.‘Moire patterns of partial derivatives of displacement components’, J. Appl. Mech., 1966, 33, 901–906.
3.
ChiangF. P.KhetanR. P.‘Differentiation of moire patterns by optical spatial filtering’, J. Appl. Mech., 1975, 42, 25–28.
4.
PirrodaL.‘Optica differentiation of geometric patterns’, Expl Mech., 1977, 17, 427–432.
5.
WangL.HovanesianJ. D.HungY. Y.‘A new fringe carrier method for the determination of displacement derivatives in hologram interferometry’, Optics Lasers Engng1984, 5, 109–120.
6.
HovanesianJ. D.HungY. Y.‘Moire contour-sum, contour-difference, and vibrational analysis of arbitrary objects’, Appl. Optics, 1971, 2734–3888.
7.
WojtaszakI. A.‘The calculation of maximum deflection, moment and shear for uniformly loaded rectangular plate with clamped edges’, J. Appl. Mech., 1937, 4, A173–A176.
