为了解决神光系列装置所需长焦透镜焦距的检测问题,在现有斐索干涉仪的基础上,对常规组合透镜方法进行了拓展,提出了双探头光栅尺法。对两种方法的工作原理及检测方法进行了分析,同时计算分析了测量数据误差对测量结果的影响,得出测量数据测量误差的上限要求。这两种方法具有测量精度高、重复性好、测量过程简单的优点,对于各类透镜焦距的检测具有重要的实用价值。 In order to solve the problem of detecting the focal length of telephoto lenses required by SG series, the conventional combination lens method was expanded on the basis of the existing Fizeau interferometer. A double-probe grating method was proposed. The working principle and testing methods of the two methods are analyzed. At the same time, the influence of the error of measurement data on the measurement results is analyzed and calculated, and the upper limit of the measurement error of the measurement data is obtained. These two methods have the advantages of high precision, good repeatability and simple measuring process, which have important practical value for the detection of the focal length of various types of lenses.