Effect of interpolation on noise propagation from images to DIC displacement maps

This paper introduces and validates a new prediction of sensor noise propagation from images of randomly marked surfaces to displacement maps obtained by digital image correlation ( DIC). Images are indeed often affected by sensor noise, which propagates to DIC output. We consider here the 2D global DIC, for which this output is the in-plane displacement calculated at a set of nodes. Predictive formula for the resolution of the displacement at these nodes is already available in the literature. The contribution of the present paper is to revisit this formula to take into account the interpolation required by sub-pixel displacement. A generalization is also proposed to predict the displacement resolution throughout the field of view. It is then extended to several kinds of DIC. The correlation procedure is thoroughly described in order to emphasize the role of the interpolation. A numerical assessment on synthetic data validates the new prediction and shows the improvement brought about by the proposed formula. Copyright (C) 2016 John Wiley & Sons, Ltd.