Laser interferometry based read-out system for seismic accelerometer

Laser interferometry is one of the most sensitive methods for small displacement displacement. This technique was successfully used in several fields of physics, giving very good performances also due to the large availability of optical components and high quality and relatively low cost laser sources. At the same time this technique is enough flexible to be effectively used in very different applications. In particular, in this paper, we present a laser interferometric system used to read the position of the sensitive element of a standard seismic accelerometer. The working mechanism of seismic accelerometers is based on a control system that acts on the sensible element to stabilize its position. By looking at the force needed to perform this feedback it is possible to obtain the acceleration. Usually the feedback system of these instruments is based on magnets and coils, or on piezoelectric actuators, while the signal transducer is usually a capacitive device. The performances of the interferometric system were analyzed in comparison with standard one. The result are encouraging also if some problem, mainly connected with the dynamic of the read-out system have to be better studied.