Characterization of large deflection with a monocular deflectometer

Abstract The optical deflectometer facilitates the characterization of deformation for the safety assessment of large structures. Actual displacement is determined by multiplying pixel displacement by a constant scaling factor, which potentially introduces errors if a large displacement occurs within a small working distance. In this study, a novel deflection measurement method has been proposed considering variations of the scaling factor to attenuate errors in large deformation measurements. As the structure deflects, the scaling factor is updated according to the changes in the working distance and local pitch angle. We first investigated how the scaling factor affects off-axis deflection measurements using a set of simulated deflection data. An experiment using a monocular camera for measuring close-range large off-axis structural deflection has been conducted to determine the vertical displacement produced by a controllable translation frame. Results, compared to traditional methods, show improved accuracy and efficiency.