单轴晶体的光程差和Lyot型滤光器的视场

 建立了以光线入射方向和晶体光轴方向为基准的入射坐标系，利用波法线反曲面方程和电磁场在晶体折射界面处切向分量连续性的边界条件，得到了晶体中波法线方向、射线方向、波法线折射率和射线折射率的表达式。从非常光的射线方向和射线折射率出发，得到了在任意的晶体光轴方向和入射角条件下，光通过单轴晶体后寻常光、非常光的光程差表达式。对Lyot型滤光单元的透射率和视场进行了计算分析后发现，滤光单元的透射率随光线入射角的变化呈现一定的周期性，视场随光轴倾角的增大而减小。得出了透射率和视场随光轴倾角(光轴与晶体表面的夹角)和光线入射角(光线在晶体表面的入射角)的变化规律。讨论了通过改变晶体倾角实现滤光器调谐和补偿晶体厚度加工误差等技术问题。

Optical path difference of uniaxial crystal and field of view of Lyot filter

An incident coordinate system was set up on the basis of the incident direction and normal direction on crystal surface.Using the inverse surface equation of wave normals and the boundary condition about the continuity of electromagnetic field tangential component at the surface of crystal,expressions about wave normal direction,ray direction,wave normal refractive index and ray refractive index were obtained.Based on the ray direction and refractive index of extraordinary light,an expression of optical path difference between ordinary and extraordinary lights was derived,when a ray of light with arbitrary incident direction passed through uniaxial crystal with arbitrary crystal axis direction.The transmissivity and field of view of a Lyot filter were analyzed.The tuning of Lyot filter and compensation of crystal thickness error were discussed by changing crystal obliquity angle.