Based on the double refraction principle of outgoing beam in the biprism,the displacement method for measuring the small angle of biprism is presented.The error of this method is also discussed.

利用镜引起射向向偏折的原理,提了一种位移法测量玻镜微小底角的新法,介绍了测量的基本原理,讨论了测量误差.