Determination of film thickness and refractive index by interferometry

The interference fringes formed in an air wedge and those based on the theory of two-beam interference such as the Pluta microscope and Michelson interferometer are utilized for estimating the thickness and/or refractive index of transparent polypropylene thin films. The theories of the methods are presented, and their applications to measurement of film thickness and refractive index are given. The accuracy of the measured film thickness and refractive index is calculated. The three interference methods proved that they could be transformed into valuable technological tools. The study established that, estimation of the thickness of thin films by the air wedge interference method is more simple and more accurate than the others. Films not more than 50 mum thickness are recommended in the Pluta interference microscope. (C) 2004 Elsevier Ltd. All rights reserved.