3D shape, deformation and strain measurement on complex structure using DIC-assisted fringe projection profilometry

Stereo digital image correlation (3D-DIC or Stereo-DIC) has advantages of high accuracy and flexibility and is widely used for 3D shape and deformation reconstruction. However, it is difficult to retrieve information of complex structure due to the severe perspective distortion in both views and area-based matching algorithm. And on the other hand, fringe projection profilometry (FPP) has pixelwise 3D shape reconstruction ability for complex structure but lacks accurate deformation and strain analyzing ability. In this work, we combine DIC with FPP to simultaneously obtain accurate 3D shape and deformation information and further perform strain analysis. First, the complete 3D shape of complex surface is reconstructed pixel by pixel using FPP. Next, the modulation of the phase-shifting fringes is extracted as texture maps to eliminate the interference of ambient light and for further DIC processing. DIC is only used to perform temporal matching for pixel-by-pixel tracking on reconstructed 3D shape. The in-plane and out-of-plane deformations are obtained simultaneously by directly comparing the complete 3D data for each corresponding pixel. Moreover, the strain in each direction is calculated by differencing the deformation data with chain rule. Experiments on the complex dynamic scene demonstrate the feasibility of the proposed method and show potential in analysis of specimen with complex structure.