Azimuthal variations in the brightness of Fabry-Perot axicon fringes

According to Fresnel relations, the transmission through an inclined dielectric plate depends on the orientation of the light vector relative to the plane of incidence. Since an axicon has a conical surface, linearly polarized incident light has different transmissivity through different portions of the axicon. It is shown that the difference in transmissivity, as a function of azimuthal angle, increases with increasing values of the vertex angle of the axicon. This effect causes inhomogeneity in the brightness of Fabry-Perot fringes, and for a slightly misaligned system can distort the shape of the scanning spectral line.