Classification of compensation films

Uniaxial film is an anisotropic birefringent film with only one optical axis. For simplicity, let us limit our discussions to non-absorption uniaxial films. From the viewpoint of optical axis orientation, uniaxial films can be classified into a film and c film. An a film s optical axis is parallel to the film surface, while a c film s optical axis is perpendicular to the film surface. 

Both a film and c film can be further divided into positive or negative films depending on the relative values of the extraordinary refractive index tie and the ordinary refractive index Table 8.1 lists aU the types of compensation films and their refractive index relationship. In our analyses, we focus on the uniaxial films. As a general rale, a positive uniaxial film means Tie no, otherwise, rig tig for a negative uniaxial film. 

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