三位置球面面形绝对检测方法在一定的条件下可以简化为两位置球面面形检测方法.本文在研究三位置绝对检测原理的基础上，提出了基于菲索干涉系统新的两位置球面面形检测方法.该方法的简化条件分为参考面面形误差偶对称或被检面面形误差偶对称两种不同的情况.实验结果表明，两位置检测方法可以有效实现PVr值λ/30的高准确度检测，且检测结果PVr值重复性在±λ/300范围内，RMS值重复性在±λ/4 000范围内.采用两位置检测方法得到的面形误差分布结果与三位置绝对检测方法非常接近，PVr值相差小于λ/300，RMS值相差小于λ/2 500.因此在一定条件下，两位置检测方法可以有效简化实验装置和检测步骤，且不失三位置绝对检测方法的准确度和重复性.

Three-position absolute surface testing technology can be simplified to method of two-position surface testing under some certain conditions.Based on the study of three-position absolute surface testing technology,a new method of two-position spherical testing via Fizeau interferometer is proposed.The method respectively assumes that the surface error of reference surface or test surface only contains aberrations with even symmetry.Results show that λ/30 PVr surface error can be measured though two-position testing as well as the method is repeatable to λ/300 PVr and λ/4000 RMS.Besides,the distribution of surface error measured through two-position testing is very close to one measured though three-position testing.The PVr difference is less than λ/300 and the RMS difference is less than λ/2500.So under certain assumptions,experimental device and process can be simplified through two-position testing method,while the accuracy and repeatability can be maintained.