Open AccessLarge depth-of-field 3D shape measurement using an electrically tunable lens
Author(s) -
Xiaowei Hu,
Guijin Wang,
Yujin Zhang,
Huazhong Yang,
Song Zhang
Publication year - 2019
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.27.029697
Subject(s) - lens (geology) , focal length , optics , synchronizing , depth of field , focus (optics) , computer science , structured light 3d scanner , phase (matter) , autofocus , field of view , projection (relational algebra) , depth of focus (tectonics) , computer vision , artificial intelligence , physics , geology , algorithm , telecommunications , scanner , quantum mechanics , transmission (telecommunications) , paleontology , subduction , tectonics
The state-of-the-art 3D shape measurement system has rather shallow working volume due to the limited depth-of-field (DOF) of conventional lens. In this paper, we propose to use the electrically tunable lens to substantially enlarge the DOF. Specifically, we capture always in-focus phase-shifted fringe patterns by precisely synchronizing the tunable lens attached to the camera with the image acquisition and the pattern projection; we develop a phase unwrapping framework that fully utilizes the geometric constraint from the camera focal length setting; and we pre-calibrate the system under different focal distance to reconstruct 3D shape from unwrapped phase map. To validate the proposed idea, we developed a prototype system that can perform high-quality measurement for the depth range of approximately 1,000 mm (400 mm - 1400 mm) with the measurement error of 0.05%. Furthermore, we demonstrated that such a technique can be used for real-time 3D shape measurement by experimentally measuring moving objects.