Optimized design of composite grating in real-time three-dimensional shape measurement

A new method for improving the measuring precision in real-time three-dimensional (3D) shape measurement by optimizing structural parameters of composite grating is proposed. By analyzing the formation mechanism of composite grating, in which three phase-shifting sinusoidal gratings with equal phase-shifts 2π/3 are modulated by three carrier gratings with different carrier frequencies along the orthogonal direction respectively, it is found that the measuring precision can be improved by optimizing the period of phase-shifting sinusoidal gratings inside the composite grating when the frequencies of carrier gratings are selected properly. Three typical surfaces (cone, peaks-function, saddle) are selected according to the complexity of the measured object to design optimized composite gratings. Experimental results show that the proposed method can improve the measuring precision in real-time 3D shape measurement.