The present work studies the refraction index and physical thickness variation of deposited thin films over large glass substrates (r ≈ 20 cms.) and source emission patterns variation, exclusively due to the type of material in the evaporation process at high vacuum. The employed method consists in varying the evaporated material and so obtaining the thin films physical thickness and refraction index in several points over the substrate through adjustment of the measured transmittance, comparing with the one obtained by simulation. The results show a radial distribution of the refraction index and physical thickness in dielectric thin films due to the material employed. © 2001 SPIE · 0277-786X/01/$15.00.