It is a device for measuring changes in the dimensions of a specimen, optically, the achieved resolution can result in greater values than those of a conventional pushrod dilatometer.
As the specimen contracts or expands, there is a proportional movement of the interference fringes, which can be measured using a camera system.
In particular, the use of optical methods has been playing a role in the field of ceramics and have been used to measure the coefficient of thermal expansion of bodies and glazes in order to ensure an optimal match of their thermomechanical behaviour.
This method has proved to be very accurate, with a resolution of a fraction of the wavelength of the incident light, but it is limited by the reflectivity of the surface of the specimen.
Optical dilatometers are used for thermal analysis of various types of materials, such as incoherent materials (expansion and contraction of an incoherent granular frit, as applied, for example, on raw tiles) and polymers (behaviour above the glass transition temperature, where the surface tension starts pulling the edges and making the sample shrink), as well as for analysis of various processes in materials manufacturing, for example, sintering kinetics, thermal expansion and sintering behaviour of thin glaze layer or polymer thin films.