High-speed three-dimensional shape measurement for dynamic scenes using bi-frequency tripolar pulse-width-modulation fringe projection

This paper introduces a high-speed three-dimensional (3-D) shape measurement technique for dynamic scenes by using bi-frequency tripolar pulse-width-modulation (TPWM) fringe projection. Two wrapped phase maps with different wavelengths can be obtained simultaneously by our bi-frequency phase-shifting algorithm. Then the two phase maps are unwrapped using a simple look-up-table based number-theoretical approach. To guarantee the robustness of phase unwrapping as well as the high sinusoidality of projected patterns, TPWM technique is employed to generate ideal fringe patterns with slight defocus. We detailed our technique, including its principle, pattern design, and system setup. Several experiments on dynamic scenes were performed, verifying that our method can achieve a speed of 1250 frames per second for fast, dense, and accurate 3-D measurements. ► We introduce a high-speed three-dimensional shape measurement technique for dynamic scenes. ► Two wrapped phase maps can be obtained simultaneously by bi-frequency phase-shifting algorithm. ► Two phase maps are unwrapped using a simple look-up-table based number-theoretical approach. ► Tripolar pulse-width-modulation technique is employed to generate ideal fringe patterns. ► Our method can achieve a speed of 1250 frames per second for fast, and accurate 3-D measurements.