近日，本实验室博士研究生陶天阳在条纹投影领域的文章"High-precision real-time 3D shape measurement using a bi-frequency scheme and multi-view system"被Applied Optics接收！
Tianyang Tao, Qian Chen, Shijie Feng, Yan Hu, Jian Da, and Chao Zuo, "High-precision real- time 3D shape measurement using a bi-frequency scheme and multi-view system," Appl. Opt. 56, 3646-3653 (2017)[PDF]
High-speed and high-precision 3D shape measurement plays a central role in diverse applications such as automatic online inspection, robotics control, and human-computer interaction. Conventional multi-frame phase-shifting-based fringe projection profilometry techniques face inherent trade-offs between the speed and measurement precision, which are fundamentally limited by the fringe density and extra pattern projections used for de-ambiguity of fringe orders. Increasing the frequency of the projection fringes can obviously improve the measurement precision; however, it creates difficulties in the subsequent phase unwrapping. For this reason, to date, the frequency of the fringes in typical real-time 3D shape measurement techniques is generally less than 30 to guarantee a reasonable reliability of phase unwrapping. To overcome this limitation, a bi-frequency phaseshifting technique based on a multi-view fringe projection system is proposed, which significantly enhances the measurement precision without compromising the measurement speed. Based on the geometric constraints in a multi-view system, the unwrapped phase of the low-frequency (10-period) fringes can be obtained directly, which serves as a reference to unwrap the high-frequency phase map with a total number of periods of up to 160. Besides, the proposed scheme with 10-period and 160-period fringes is suitable for slightly defocusing projection, allowing a higher projection rate and measurement speed. Experiments on both static and dynamic scenes are performed, verifying that our method can achieve high-speed and high-precision 3D measurement at 300 frames per second with a precision of about 50 μm.