Full-Field 3D Mode Shape Measurement Using the Multiview Spectral Optical Flow Imaging Method

Abstract

In some modal testing applications, image-based techniques offer compelling advantages compared to conventional sensors, particularly in cases where mass loading is problematic or a high spatial resolution is required. Still, the limited field of view of the well-established stereo DIC method can be a limiting factor in some measurements. By employing the principles of multi-view imaging, this constraint can be alleviated. For linear, time-invariant structures, multi-view triangulation can be performed in the frequency domain. The measurement field of view can in this way be arbitrarily extended using only a single moving camera imaging system. By using the simplified optical flow method in the displacement spectra identification step, a still-frame camera can be used for image acquisition, considerably lowering the complexity and cost of the imaging system. In this work, the spectral optical flow imaging and frequency-domain multi-view triangulation approaches are combined in an effort to identify mode shapes of a simple three-dimensional structure. The aim is to develop a robust and cost-effective single still-frame camera-based modal testing method.