根据纳米计量分辨力的要求，设计一套共焦法布里珀罗(F-P)干涉显微测头。系统光源采用保偏光纤直接导入，从F-P腔外入射。光路设计成便于减小光学共模噪音的差动形式。通过建立模型分析系统光学特性，得出反射平板的最佳反射率以及共焦结构对干涉条纹的影响。实验验证表明反射平板反射率为40%时可以使系统得到对比度高，信噪比好的干涉条纹；针孔光阑可以方便寻找测量透镜的焦点和减小杂散光的噪音；系统轴向分辨力达到0.2 nm。

According to the requirements of resolution of nanometrology, a confocal Fabry-Pérot (F-P) interference microscopy probe is designed. The laser source is directly conveyed into the system by the single polarization-maintaining fiber, and passes through F-P cavity. In order to reduce the optical common mood noise, the differential optical path is designed. Through the establishment of model, the physics characters of the system are analyzed. The best reflectivity of the reflection plate can be obtained and how the confocal impacting the interference process can be found. The experiment results show that the system can get interference fringes with high-contrast and high signal to noise ratio when the reflectivity of the reflection plate is 40%. Pinhole aperture is favorable for finding the focus of the measure lens and reduces the noise of stray light. The axial resolution of the system can reach up to 0.2 nm.