A vibration remote sensors based on speckle tracking is an optical receiver-transmitter system, which transmits a 532 nm laser beam, a coherent light which is scattered by a vibrating surface, the irregularities of which produce small spots (or speckles). A receiver optical system, which ends in a photosensor (CCD), receives the granular image of the moving speckles. A mathematical algorithm then reconstructs the vibrations of the surface hit by the laser beam starting from the overall movement of the speckles (speckle pattern tracking).

The remote sensors based on speckle tracking mainly measures the angular velocity d9/dt, the fundamental frequencies, and the harmonics of the investigated surface. Displacements and angular accelerations can be inferred from these data with simple on-line operations. Furthermore, other kinematic parameters can also be determined from the knowledge of the geometric surface. Remote sensors may be used in long-distance (even beyond 200 m) measurements of surfaces vibrations of physical targets of various nature.