强激光系统中，光学元件表面中频段误差会导致光学元件的丝状破坏，引起光束的高频调制和非线性自聚焦，从而影响系统工作。现阶段还没有仪器专门针对中频段误差进行测试，做出完整的分析。为解决这一问题，设计出一套高分辨率干涉仪系统，对光学元件表面中频部分实行全频段检测。采用结构简单的Fizeau干涉光路，利用光纤导出式稳频激光作为光源，采用半波片、偏振分光棱镜和1/4波片组合成偏振干涉光路，成像系统采用双远心光路设计并使用超光滑面作为标准参考平面镜，并搭建了一套实验系统。实验结果表明该系统在空间频率8.3 mm-1处的系统传递函数(STF)大于70%，达到中频段检测要求。

In the high power solid-state laser facility, the mid-spatial frequency error of the optical elements can lead to a serious filamentous destruction of the optical components, then cause high frequency modulation and nonlinear self focusing of the light beam, thus affect the system. However, there is no instrument which is suitable to test the whole mid-spatial frequency error and give a complete analysis. To solve this problem, a set of high resolution interferometer system which can measure the whole mid-spatial frequency band of the surface is designed. System design using fiber stable laser as the light source is based on the simple structure of Fizeau interference light path. Half-wave plate, polarizing beam splitter and quarter wave plate are used for the polarized interference. The imaging system is designed for double telecentric light path, using a super smooth surface as the standard reference mirror. A set of experimental system is built and the experimental results show that the system transfer function at spatial frequency of 8.3 mm-1 is superior to 70%, which achieves the requirement of the measurement of mid-spatial frequency error.