A fast-operating interferometry device for measuring films thickness over the range from ten to one thousand microns

A fast-operating laser-interferometric device for measuring the thickness of films which are transparent in visible or infrared ranges is described in this work. The thickness of the films to be investigated is from 10 µm to 1 mm. Measuring frequency is 25 times per second, time of one measurement is 3·10-4 s. This allows measuring the thickness of unstable films including liquid ones. Due to combining two ways of determining the thickness in one device (by the number of peaks in the angular dependence of the laser beam reflectance coefficient, and by the value of this coefficient at a given angle of incidence) the error in determining the thickness is only 150 nm.