面向背光照相技术是诊断惯性约束聚变（ICF）中瑞利-泰勒（RT）不稳定性的重要方法，讨论了利用该技术对球形靶丸扰动幅度测量时由于收缩几何效应带来的影响。通过计算，分析了一个简化模型下扰动振幅的实际值和测量值，讨论了偏移距离、靶丸外半径、扰动波长和扰动振幅等因素对实验结果相对误差的影响。计算表明，合理选择这些参数能使诊断的系统误差小于3%，而且可通过计算模型对测量结果进行修正。研究结果可为即将开展的神光III激光装置上的收缩几何烧蚀RT不稳定性实验参数设计和结果分析提供依据。

Face-on radiography is a significant method to diagnose Rayleigh-Taylor (RT) instability in inertial confinement fusion (ICF). The effects of convergent geometry on the measurement of the perturbation amplitude of spherical capsule by face-on radiography are discussed in this paper. By calculation, the actual value and measured value of perturbation amplitude are analyzed under a simplified model. The effects of such factors as offset distance, the outer radius of capsule, the wavelength and amplitude of perturbations on the relative errors of the experiment results are discussed as well. The calculation results show that reasonable choice of these parameters can make the diagnosis of systematic error less than 3%, and the measurement results can be corrected by the calculation model. The study results can provide reference for the parameter design and result analysis of future experiments of convergent geometry erosion RT instability on Shenguang-III laser facility.