Frequency domain triangulation for full-field 3D operating-deflection-shape identification

The use of high-speed camera systems in vibration measurements is typically limited to identifying motion, transversal to the optical axis, due to an inherent limitation of 2D imaging systems. Depth information, lost in the imaging process, can be recovered by using the well-established 3D DIC technique, but is still limited to a single face of the object, observed by the stereo pair. In this research a full-field 3D operating-deflection-shape measurement technique, based on frequency-domain triangulation of image-data, is presented. A mathematical model of frequency-domain perspective transformation of small harmonic motion is introduced. This model is used to relate multiview image data to spatial amplitude spectra of the observed displacement. Using the developed method, spatial small harmonic motion of arbitrary-shaped specimen can be identified in the frequency domain using only a single, moving high-speed camera, extending the field-of-view of the established image-based vibration measurement methods. (C) 2019 Elsevier Ltd. All rights reserved.