A Focused-Beam Type Laser Interferometric Dilatometer

Using a laser beam focused near interferometer plates, an improved interferometric dilatometer has been developed. It has a couple of features, i.e. it has a much greater latitude in parallelism adjustment of the interferometer plates than that of the conventional Fizeau-type ones and enables, on the other hand, automatic recording with a simple device just composed of a solar cell and a recorder to measure reflected beams. Moreover, collimation of the optical system is very easy. Therefore, it is applicable even to routine determination of dilatation for quality control in a factory. The dilatometer is capable of determining the thermal dilatation of materials with low and/or negative expansion as well as those with transition, extremum or inflection point in expansion curves. Experimental results on some metallic, ceramic, semiconductor and glassy materials are presented.