Method for Eliminating Interference Fringes for Thin Film Infrared Measurements
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
In making absorption band measurements of films on substrates using optical methods, the interference fringes can cause difficulty. In the method described here, an incident ray is applied at a fixed angle to the film and the rays reflected from the surface of the film and the interface between the film and substrate are detected and added to the detected rays transmitted through the film and substrate, thereby cancelling interference fringes. Fig. 1 shows a cross-section of a typical substrate where ray 1 is the incident ray, ray 2 is reflected from the film 6 surface, ray 3 is reflected from the film 6 and substrate 7 interface, and rays 4 and 5 are transmitted through both the film 6 and the substrate 7. Reflected rays 2 and 3 cause an interference pattern.