Long-Distance Electronic Speckle Pattern Interferometry

Abstract

Electronic speckle pattern interferometry has been used to measure the vibrations and deformations of objects located far from the optical head. Vibration recordings were made for a total path-length difference of up to 200 m with the object outdoors in bright sunshine. This limit was determined by practical considerations. For deformation recordings, turbulence and mechanical instabilities create a problem, and a more realistic limit is a path-length difference of about 50 m under stable, indoor conditions.