双三步相移算法证明可以较大地减少数字光栅投影测量轮廓术的测量误差，基于理论分析与实验验证，针对常用的四步、五步相移算法，提出了相应的双四步、双五步相移算法。通过两次传统相移算法得到两幅主值相位图，直接融合两幅主值相位图即可获得测量所需的相位信息，与已有的针对两幅展开相位进行相位融合方法相比，此方法实现简单且更加有效。相较于双三步相移算法，双四步和双五步相移算法实现简单且能够极大地减少测量误差，仅需通过投影2倍数目传统相移算法所需的投影光栅，且可保持常用三步、四步及五步相移算法固有的优点。

Double three-step phase shifting algorithm (PSA) works well in reducing the measurement error for a digital fringe projection profilometric system. Based on theoretical analysis and experiments, double four-step PSA and double five-step PSA are proposed. In addition, a new method to average two obtained phase maps and to generate the correct phase map is presented, which is simple and effective for double-step PSA. Experiment verifies the correctness of double four-step PSA and double five-step PSA which can reduce much more measurement error than double three-step PSA in the practical applications. The advantages of three-step, four-step and five-step PSA are kept through projecting double the number of fringe patterns which are needed for traditional phase shifting algorithm.