Three-Dimensional Shape Measuring Method Based on Dual-Frequency Digital Moire Fringe

A dual-frequency digital Moire measurement method (DFDM) is proposed for the three-dimensional (3D) shape measurement of an object. The high- and low-frequency fringes are modulated separately along orthogonal direction using different carrier frequencies before being projected onto the measured object. After collecting and demodulating the composite fringe, the digital pi phase shift is used to remove the DC component of the demodulated fringes, resulting in high-precision Moire fringes for calculating the wrapped phase. The unwrapping of the high-frequency wrapped phase is guided by the low-frequency phase to further realistically reconstruct the surface of the measured object. When compared with existing single-shot digital Moire profilometry, DFDM effectively removes the DC component of the fringe and calculates the phase more accurately.