外差激光干涉仪由于测量精度高,环境适应能力强和实时动态高速测量等特点而广泛应用于机床误差的实时监测中。外差激光干涉仪中,使用平面镜作为转向装置时,接收器上的两束光有可能只是相交而不是重合,这给光路的调节增加了很大的难度。针对这一问题,提出一种辅助光路调节方法,先将光路切换到单频干涉仪,调好光路,再切换到外差干涉仪,利用单频干涉条纹的直观性能可看出外差干涉仪光路调节的好坏。理论分析和实验结果表明，提出的调节方案具有可行性,效果良好,同时通过从单频切换到双频能更深入地理解拍频。

The heterodyne interferometer is widely used in real-time measurement of errors for machine tools due to its high accuracy,high adaptability to environment and real-time dynamic measurement.While the plane mirror is used as the steering device,the spots on the receiver may be just intersected instead of overlapped,which increases a lot of difficulties to adjust the optical path.In order to solve this problem,a new method is proposed.Firstly,the optical path is switched to a homodyne interferometer.Then the optical path is switched back to the heterodyne interferometer.The optical path of the heterodyne interferometer is observed by the visible homodyne interference fringes.This scheme is simple.Theoretical analysis and experimental results show that the proposed scheme is feasible and effective,and it is useful to understand the beat frequency by the switching between the two interferometers.