Large DOF microscopic fringe projection profilometry with a coaxial light-field structure.

Fringe projection profilometry (FPP) has been widely researched for three-dimensional (3D) microscopic measurement during recent decades. Nevertheless, some disadvantages arising from the limited depth of field and occlusion still exist and need to be further addressed. In this paper, light field imaging is introduced for microscopic fringe projection profilometry (MFPP) to obtain a larger depth of field. Meanwhile, this system is built with a coaxial structure to reduce occlusion, where the principle of triangulation is no longer applicable. In this situation, the depth information is estimated based on the epipolar plane image (EPI) of light field. In order to make a quantitative measurement, a metric calibration method which establishes the mapping between the slope of the line feature in EPI and the depth information is proposed for this system. Finally, a group of experiments demonstrate that the proposed LF-MFPP system can work well for depth estimation with a large DOF and reduced occlusion.