In this paper, I present a novel scheme for the analysis of a general 5-layer interferometer in the surface forces apparatus (SFA), which significantly expands the variety of surfaces that can be investigated using the SFA, This scheme is used to determine the distance between the surfaces from the measured wavelengths of the fringes of equal chromatic order (FECO) in the SFA. This analysis involves the use of the multilayer matrix method in combination with the analytic expressions derived for simple 1-layer interferometer. The applicability of this scheme to analyze 5-layer interferometers involving a variety of polymers is demonstrated. Measurements of dispersion in refractive indices of several polymers are also reported.