Three frames phase-shifting shadow moiré using arbitrary unknown phase steps

A method combining the spatial and temporal fringe analysis techniques is proposed to extract the phase from shadow moiré interferogram with random phase shift. The proposed method first determines the grating translation difference based on the spiral phase transform technique. Then the initial phase shift is estimated. After that a generalized iterative least-squares method is developed to retrieve the accurate phase map using three interferogram frames. The proposed method relaxes the restriction on phase shift calibration between frames and provides stable and correct convergence in a fast way. Simulation and experiment demonstrate the effectiveness of this method. It shows our method possesses a superior performance than the existing typical phase-shifting algorithm. The proposed method is suitable for phase-shifting shadow moiré.