A Practical System for Measuring Film Thickness by Means of Laser Interference with Laminar-Like Laser

A practical system for measuring a film thickness based on laser interferometry has been constructed using laminar-like laser and a CCD camera. The system can measure a film thickness at a measuring frequency of 50 Hz, which enables real-time measurement in practical use. The measurable minimum thickness by means of a blue laser having a wavelength of 405 nm was 2.4 μm, and the maximum thickness was 1.2 mm for a film with a refractive index of 1.4. The measurement error of the film thickness due to the spherical aberration of the cylindrical lens was Δh/h=2% at maximum, where h expresses film thickness and Δh its error amount