Laser wave front matching interferometer for thickness measurements

The so-called Laser Wave Front Matching Interferometer (LWFMI) is developed for thickness measurements of transparent films and layers with high spatial resolution. This interferometer is constructed under scheme of Michelson interferometer with focusing microobjectives in the interferometer arms (Linnik scheme) and wide integrating detector aperture in common exit branch. The peaks are observed in the envelope of interference LWFMI signal as function of object displacement relatively to the focal point of an interferometer focusing objective when the probing beam is focused on the front and rear surfaces of a layer. The distance between the interference peaks is proportional to the geometrical thickness of a layer and can be measured by the technique of interference fringe counting, if the refractive index of layer medium is known. The results of geometrical thickness measurements of some objects by this interferometer for high numerical aperture of probing focused beam are discussed.