In this simulator the amplitude and phase of a light wave are represented by the amplitude and phase of an ac voltage. Each layer in the film is simulated by a four-terminal network containing adjustable attenuators and an adjustable phase shifter. The network obeys the same difference equation [See: Lord Rayleigh, Proc. Roy. Soc. (London) 93, 565 (1917); P. Rouard, Ann. Phys., Ser. 11, 7, 291 (1937); W. Pfister and O. H. Roth, Hochfrequenztechnik und Elektroakustik 51, 156 (1938); S. M. MacNeille, U. S. Patent No. 2 403 731; A. Vasicek, J. Opt. Soc. Am. 37, 623 (1947); D. Caballero, J. Opt. Soc. Am. 37, 176 (1947) as that which relates the reflectance of <i>n</i>+1 interference layers to the separate reflectances of the first <i>n</i> layers taken together and of the <i>n</i>+1th layer. With these networks connected in sequence and the circuit parameters adjusted to correspond to the optical constants of the various layers of the film, either the reflectance or transmittance of the multilayer can be read directly on a meter. Since the circuit parameters correspond to (1) reflectance at the interface between layers, (2) phase retardation, and (3) attenuation with passage through the layer, the instrument can treat problems involving oblique as well as normal incidence, polarization, and absorption.
S. M. MACNEILLE and E. O. DIXON, "Simulator for Calculating the Reflectance and Transmittance of Multilayer Interference Films," J. Opt. Soc. Am. 44, 805-806 (1954)