An important task in the sampling Moir´e method is phase measurement of a grating image by using the phase of the Moir´e fringe from a single-shot image. In order to reducing the phase errors that are due to non-sinusoidal functions in any phase measurement systems that use phaseshifting techniques one should take in to account other harmonics of the grating function. The proposed formulation in this work removes this kind of errors effectively. At first it is shown that by down-sampling of a periodic function the gained Moir´e function is a stretched version of the original one. Then, an equation is obtained for the Moir´e phase function based on this result. A numerical solution method is presented to solve the equation with a sufficient accuracy. The simulation results verify the effectiveness of the proposed method.
