Reconstruction of measurable sets from two generalized projections

The problem of reconstructing a measurable plane set from its two generalized projections is considered. It means that the projections contain also the effect of a known modification given in the whole plane. This is a more general case than that of a constant absorption within a given material. Via a suitable mapping, this generalized problem can be transformed into the solved case of the classical (non-absorbed and non-generalized) projections, giving a theorem about the characterization of unique, non-unique, and inconsistent projections analogous to Lorentz' theorem. The connection between uniqueness and the existence of so-called generalized switching components is discussed.