Displacement Measurement Using Concentric Moiré Method

Non-contact displacement measurement is necessary for evaluating the health of infrastructure structures. One of the non-contact displacement measurement technologies is the sampling moiré method. This method is capable of measuring displacements greater than the grating pitch by using time-series displacement information. However, if the displacement between one frame exceeds half the grating pitch or if there is an obstacle such as a person between the camera and the grating, the displacement cannot be measured correctly. In this paper, we propose a concentric moiré method in which the grating is replaced by concentric circles. This method makes it possible to measure displacements greater than the grating pitch using only spatial information rather than time series. We confirm that the proposed method makes it possible to measure displacements greater than half the grating pitch between one frame.