2. Full-Field Three-Dimensional Characterization of Non-repetitive Motions by Single-Shot Multiplexed Digital Holography

Typically, in 3D displacement measurements, the sample is repeatedly loaded at least three times and the displacement fields are obtained from multiple sensitivity vectors. However, for studying transient and non-repetitive phenomena, including, but not limited to, displacement fields of temporally-varying biological tissues, repeating the experiment is not an option. Therefore, to measure 3D displacements in such applications, all the measurements have to be done concomitantly. In this paper, single-frame, multiplexed holography is used for simultaneous quantification of 3D displacement fields. In our approach, the hologram of an object of interest is recorded in an off-axis configuration, with three simultaneous incoherently-superimposed pairs of reference and object beams. Three different spatial carrier frequencies are realized by small differences in the angle of illumination of each reference wave with respect to the CCD sensor. Therefore, the reconstructed image corresponding to each illumination direction is reconstructed at a particular position on the image plane. Because of the differences in the position of each reference beam and wavelength of each pair of beams, the reconstruction distance and magnification of each sensitivity vector are different. Therefore, we developed and implemented registration algorithms to accurately translate individual views into a single global coordinate system. Representative results highlighting the 3D measuring capabilities of our holographic system are presented.