Application of SSR for Bridge Deflection Measurement by Using of Digital Image Correlation

Being different from the displacement and strain measurements in a laboratory environment, the bridge deflection measurement by using of digital image correlation is very impressionable due to the changes of ambient light. The illumination disturbances can result in an increase of deflection measurement errors or unreliable results. In order to decrease the influence of illumination disturbances on the results, the images were preprocessed by Single Scale Retinex. The experiments showed Single Scale Retinex could effectively decrease the influence of illumination disturbances on bridge deflection measurement. In a laboratory environment, SSR could decrease the systematic errors by more than 50% and the random errors by 30%-60%. In a field environment, the inhibitory effect of SSR on the changes of ambient light was not as obvious as the indoor test. But, the accuracy of bridge deflection measurement in field could be improved by using SSR for preprocessing.