Fringe Projection Profilometry for Metal Additive Manufacturing Parts Using Trinocular Vision Model

Additive manufacturing (AM) presents significant advantages for fabricating complex geometries and structured surfaces, which is difficult using conventional manufacturing. The complex surfaces by additive manufacturing pose challenges to 3D shape measurements and quality controls. This paper proposes a binocular fringe projection profilometry system applying a trinocular vision model based on a plane sweeping method to measure the shape of complex surfaces fabricated by Selective laser melting (SLM). Firstly, the left and right wrapped phase maps are extracted using an N-step phase-shifting algorithm. The extracted phase maps are unwrapped by dual-frequency heterodyne. Then, a novel trinocular vision model for binocular fringe projection profilometry based on a plane sweeping method is presented to recover the 3D locations of measured points from matched binocular image points as well as the absolute phase values of the structured light projector. The proposed methods can effectively exploit the depth cues from the phase map without the complex projector calibration. The experiment results demonstrate that the proposed methods achieve high precision and are able to be utilized to inspect metal additive manufacturing parts.