提出了一种基于特殊点的两步广义相移干涉相移值提取算法。搜索干涉图中满足特殊要求的点位置并利用相移值和特殊点数据关系计算得到相移值。根据是否需要记录物光和参考光图像分为盲提取和非盲提取两种方式。进行了理论分析、模拟仿真及实验验证。实验结果表明，该算法在速度和精度上达到同类算法的水平，在干涉条纹数少于1时相移提取值精度优于同类算法。

A phase shift extraction algorithm based on the special points in two-step generalized phase-shifting interferometry is proposed. This algorithm searches the special points that meet specific requirements and calculates the phase shift via the latter′s relationship with these special points. It is divided into two modes according to whether the intensity distributions of the two interference beams are recorded or not. Theoretical analysis, computer simulation and experimental verification are carried out. Experimental results show that this algorithm reaches the same level of other algorithms in speed and accuracy. Moreover, when the interferogram′s fringe number is less than one, a better phase shift extraction accuracy can be obtained.