负双轴晶体光轴角和光线轴角推导的新方法

为了有助于人们更好的理解和区分双轴晶体的光轴角和光线轴角，以及对光在晶体中传播的理解，本文以负双轴晶体为例，根据光轴和光线轴的定义，从菲涅耳波面法线方程和光线方程出发，推导出了光轴角和光线轴角的表达式。作为对此新方法的验证，通过几何作图法得到了一致的结果，由此证明这一新方法是正确的。

New inference method of the optic axial angle and the ray axial angle of the negative biaxial crystal

In order to help people to understand and discriminate two concepts of the optic axial angle and ray axial angle, as well as to understand the propagation of ray in the crystal, this paper gives a new method. This paper has given the equations of the optic axial angle and the ray axial angle of the negative biaxial crystal, based on the Fresnel＇s wave normal equation and the ray equation, according to the definitions of the optical axis and the ray axis. The new method is proved to be correct because the same results are shown by geometric construction derivation.