Dual-frequency pattern scheme for high-speed 3-D shape measurement

TLDR

The study introduces a dual‑frequency pattern combining a high‑frequency sinusoid for robust phase and a unit‑frequency sinusoid to reduce unwrapping ambiguities, and develops real‑time lookup‑table algorithms for phase generation and 3‑D reconstruction. The authors implement fast lookup‑table based algorithms that apply to both the proposed dual‑frequency scheme and conventional phase‑measuring profilometry, enabling rapid phase data processing. The scheme eliminates phase jumping and discontinuities, produces higher‑quality phase data with fewer patterns, and delivers 1063.8 fps phase frames and 8.3 fps 3‑D point clouds—25‑fold and 10‑fold speedups over previous work.

Abstract

A novel dual-frequency pattern is developed which combines a high-frequency sinusoid component with a unit-frequency sinusoid component, where the high-frequency component is used to generate robust phase information, and the unit-frequency component is used to reduce phase unwrapping ambiguities. With our proposed pattern scheme, phase unwrapping can overcome the major shortcomings of conventional spatial phase unwrapping: phase jumping and discontinuities. Compared with conventional temporal phase unwrapped approaches, the proposed pattern scheme can achieve higher quality phase data using a less number of patterns. To process data in real time, we also propose and develop look-up table based fast and accurate algorithms for phase generation and 3-D reconstruction. Those fast algorithms can be applied to our pattern scheme as well as traditional phase measuring profilometry. For a 640 x 480 video stream, we can generate phase data at 1063.8 frames per second and full 3-D coordinate point clouds at 8.3 frames per second. These achievements are 25 and 10 times faster than previously reported studies.