Considerable interest in speckle metrology and a consistent search to refine these techniques to suit the intricate engineering environment has led to an active investigation into the basic aspects of speckle movements in three-dimensional space induced by small displacements and deformations of the object surface. The model exploited in this paper is based on the notion of the local invariance of the speckle structure in such a case; it is thus intimately related to the concept of homology and draws closely on the theories aiming to reconcile speckle metrology and holographic interferometry techniques. The laws of speckle motions issuing from this model are applied to major known techniques in speckle photography (focused or defocused), speckle interferometry, and speckle shearing interferometry in an attempt to make as objective an assessment as possible of these methods. The study unveils the influence of parasite movements, field angles, and the geometrical parameters at the recording on the measured component, thereby paving the way for the optimization of a method to a given deformation problem and forging a better understanding of the phenomenon underlying these techniques.
Pramod K. Rastogi,
"Speckle Metrology Techniques: A Parametric Examination Of The Observed Fringes," Optical Engineering 21(3), 213411 (1 June 1982). https://doi.org/10.1117/12.7972924