Low-frame-rate single camera system for 3D full-field high-frequency vibration measurements

A single-camera stereo-digital image correlation (stereo-DIC) system to obtain 3D full-field vibration measurements is proposed. The optical setup is composed of two planar mirrors and a single low frame rate camera, thus resulting in a compact and low-cost equipment. The two mirrors are used to create pseudo-stereo images of a target surface on the camera sensor, which are then correlated by using stereo-DIC. The image acquisition process is carried out at low frame rates and the Nyquist-Shannon frequency limitation is overcome by adopting a down-sampling approach under the hypothesis that the vibration signal is characterized by a single known frequency component. The developed pseudo-stereo DIC system allows to obtain 3D full-field vibration measurements in a frequency range up to 4 kHz even with an available frame rate (at full resolution) of 178 fps. The effectiveness of the described approach has been verified by performing vibration measurements on a cantilever plate and a turbine blade.