A digital holographic method for simultaneous measurement of the displacement and its spatial derivatives is described. In this method, two holograms are first recorded in the undeformed and deformed states of the specimen; then two object waves related to the two states of the specimen are numerically reconstructed. The phase maps of the displacement and its derivatives can be generated simultaneously from these two reconstructed object waves with a numerical method. This proposed method offers a simple experimental setup, flexibility in handing the data, and high quality of phase maps.
"Simultaneous measurement of displacement and its spatial derivatives with a digital holographic method," Optical Engineering 42(12), (1 December 2003). https://doi.org/10.1117/1.1624077