Invariants of the reflection coefficient

A detailed analysis of the reflection coefficient of linearly polarized in plane of incidence of a plane monochromatic wave from a three-layer structure is carried out. Solved the reverse problem ellipsometry for a three-layer structure. The existence of two reflection factor invariants for the flat-parallel plate is shown. A set of three observable parameters not previously used is proposed, which allows to restore the material parameters of the layer. Analytical expressions are obtained both for the reflection coefficient and incidence angles for a number of important particular cases, and for the direct calculation of the dielectric constant and layer thickness from the measured values of the observed parameters.