Film thickness measurement by improved Michelson′s interferometer

For the measuring of the thickness of an opaque or refractivity-unknown film a force sensor is added to the traditional Michelson′s interferometer.Employing the principle of equal inclination interference coupled with the offset method,the result is an improved measuring instrument.The film is replaced by a layer of air as substitution.Through indirect measurement,the lost motion effect is avoided.More over,the effect of pressing is greatly weakened by using the pressure sensor.The measuring range of this apparatus is between 0.3 μm and 1.5 mm,and the effective resolution reaches 0.3 μm.The result indicates that the improved device is of good repeatability and accuracy.