Account for the wedgeness and inhomogeneity of thin layers in the inverse problem of spectrophotometry on reflection

General formulas for reflectance of a weakly or moderately absorbing tapered layer and a layer with a linear dependence of the complex dielectric constant on the thickness, which are located on an absorbing substrate, are derived. Based on these formulas, a method for determining the optical constants, their dispersion, and the layer thickness from the envelopes of the extrema in the interference reflection spectrum is constructed, which generalizes the method proposed previously for homogeneous absorbing films.