光学畸变是大视场星敏感器标定的重要误差源之一，由于各误差之间存在耦合，光学畸变将会影响焦距标定精度。针对此问题，基于针孔模型，建立了光学畸变对焦距标定影响的数学模型，推导得到了采用最小二乘法时标定用导航星的入射角参考阈值βmax，为星敏感器的焦距标定提供了理论参考。仿真实验表明，与标定用导航星的部分或全部入射角大于βmax时的焦距标定精度相比，标定用导航星的入射角均小于βmax时的焦距标定精度分别平均提高了5倍和10倍左右，有效降低了光学畸变对焦距标定精度的影响。

Optical distortion is one of important error sources of Wide Field-of-View (WFOV) star sensor,which has a great effect on focal length calibration due to coupling between the errors.To solve the problem,we established a mathematical model to determine the coupling relationship between optical distortion and focal length based on pinhole model.The referring threshold βmax of guide star incident angle is deduced using least square method to calibrate focal length,which provides the theoretical reference for focal length calibration.Simulation results demonstrate that:compared with calibration accuracy in cases that partial or all the guide star incident angles are greater than βmax,the focal length calibration accuracy in case that all guide star incident angles are less than βmax is increased by five times and ten times respectively.The influence of optical distortion on focal length calibration is effectively reduced.