Vibration Measurement of 3-D Objects With Single-Shot Double Field-of-View High-Speed Digital Holography

Vibration measurement is critical in engineering as it plays a vital role in ensuring the safety, reliability, and performance of machinery, structures, and systems. Non-destructive techniques, such as digital holography for vibration measurements, are most important for assessing the dynamic behavior of structures and materials without inflicting damage or alteration with high resolution and precision. In this work, to the best of our knowledge, for the first time, we experimentally demonstrated a high-speed digital holography approach for out-of-plane displacement and vibration measurements of 3-D objects in a single-shot acquisition with double field-of-view (FoV) imaging capability. This extended FoV is realized by spatial multiplexing the object wavefront with distinct object information onto the faceplate of a digital image sensor. This multiplexing is achieved by inserting a cube beam splitter (CBS) in the object wavefront. The CBS is slanted to create two object wavefronts with two distinct FoVs that propagate in almost the same direction and accumulate near the image sensor, each carrying a different set of object information. During the reconstruction process, two different imaging areas corresponding to the two recorded FoVs can be obtained concurrently, and hence the desired information, including the phase, displacement/deformation, vibration, refractive index, etc. The single-shot acquisition is realized by principal component analysis (PCA) based computational method. The digital holographic system is used for imaging distinct areas of 3-D reflective objects recorded in a single multiplexed hologram and for studying dynamic phenomena such as displacement and vibration measurements. The proposed system could have a broad range of usages in exploring real-time dynamic phenomena with the advantages of single-shot acquisition and wider FoV.