Fast Fringe Projection Profilometry of Deep Micro-Scale Objects using Holographic Detection

Phase-shifting Fringe Projection Profilometry (FPP) is the state-of-the-art 3D measurement technique for many macroscopic applications, but as necessary object details become microscopic, depth-of-field slows measurements and requires mechanism usage. To overcome this limitation, we introduce Digital Holography (DH) to capture fringe images and allow numerical refocusing on object areas which are defocused. We experimentally prove the concept and compare depth measurement noise to other DH and FPP techniques. We show that for low levels of defocus, incoherent FPP clearly outperforms coherent techniques. However, at strong defocus, the new approach reduces measurement uncertainty whilst performing similarly to other DH approaches, enabling FPP measurement of deep objects with fewer captures.