MEMS-mirror-based dynamic structured light projection system for three-dimensional measurement with high precision

Three-dimensional (3D) measurement based on structured light, as a non-contact, active, and high-precision measurement technology, is widely applied in the diverse fields of industrial detection, face recognition, reverse engineering, and so on. We adopted an adjustable grating-stripe coding as the dynamic structured-light mode, which can continuously cover the entire measured surface to guarantee high accuracy. A one-axis resonant-mode MEMS mirror combined with a linear laser was used to project the desired adjustable grating stripes, leading to a miniaturized module size. To make the scanning angle of the MEMS mirror matching the intensity distribution of the linear laser, we further introduced a single-chip microcomputer (STM32) to receive the feed-back signals from MEMS mirror, and synchronously controlled the laser power with corresponding function relationship output. Here, the MEMS mirror could provide a resonant frequency of 1.15 kHz, a scanning optical angle of ±30°, a feed-back scanning-angle resolution of 0.05°, and a reflected mirror size of 3 mm-diameter circle, respectively. Also, the laser source could generate a line width of 70 μm at a 300 mm focused distance. To decrease the error in the energy amplitude of each cycle of the structured light stripes, the empirical mode decomposition (EMD) was used to perform principal component analysis and recombination of the structured light stripes. In addition, total harmonic distortion (THD) is used to evaluate the quality of structured light stripes. Finally, the structured light based on the scanning of the MEMS mirrors exhibits a good sinusoidal stripes and high refresh rate, implying high adaptivity for the 3D reconstruction.