An optical interferometric system has been developed that measures changes in the position or density of an object utilizing the phase of the light that is reflected at or transmitted by the investigated object. With this system qualities like shape, refractive index, strain, mass density, deformation and surface roughness can be determined with a high accuracy. Furthermore, the developed system can be applied to detect defects in, for example, composite materials. The system is capable of performing 25 measurements per second, which is at least 3 times as fast as conventional systems. Because of this speed, our system is less sensitive to external disturbances like air flow, temperature changes and vibrations and can therefore be applied in industrial environments. Furthermore, the developed system can be utilized to monitor time dependent processes and fast vibrating objects.