High Sensitivity Fringe Projection Profilometry Combining Optimal Fringe Frequency and Optimal Fringe Direction

Phase sensitivity plays a vital role in accurately retrieving three-dimensional (3D) shape of diffused objects in fringe projection profilometry (FPP). With regard to traditional means that simply project horizontal or vertical fringe patterns, the fringe frequency and direction may not be the best choice to acquire optimal sensitivity to depth variations. To overcome this problem, this paper proposes a novel method to obtain 3D shape with high accuracy by combining the optimal fringe frequency and the optimal fringe direction (OFF + OFD). Firstly, in order to reduce phase error caused by periodic inconsistency of the traditional fringe projection methods, period of the projected fringe is corrected by using the high-accuracy planar homography. Secondly, the optimal fringe direction is calculated by projecting sets of corrected horizontal and vertical fringe patterns onto a depth-known standard block with the optimal fringe frequency. Finally, the validation is conducted by projecting the optimized fringe patterns onto the measured objects to reconstruct 3D shape. The simulations and actual experiments demonstrate that the proposed optimization method is feasible and effective in increasing phase sensitivity and measurement accuracy.