Real-time illumination adjustment for video deflectometers

Video deflectometers, as a real-time, contactless optical means, show great potentials in monitoring structural deflections. However, variations of illumination conditions pose a severe challenge on accurate measurement. In this study, a strategy with global illumination adjustment has been proposed to dynamically change the exposure time of the camera to achieve an optimal intensity distribution. An illumination-robust digital image correlation (DIC) algorithm is also proposed for accurate, real-time video deflection measurement. The combined method improves robustness and accuracy of measurement in two ways, which includes globally dynamic intensity adjustment and modification of the grayscale arrays in subsets during the correlation process. Experiments in the laboratory environment and applications in the outdoor environment have been conducted to validate the performance of the proposed method. The results show that the proposed method is feasible and accurate in real-time deflection measurement in the outdoor environment with variations of environmental illumination.

Automated summary

Video deflectometers show great potential in monitoring structural deflections. This study proposes a strategy with global illumination adjustment and an illumination-robust digital image correlation algorithm for real-time video deflection measurement. Experiments validate the feasibility and accuracy of the proposed method in outdoor environments.