In-plane electronic speckle pattern of interference (ESPI) with optical fibre system applied to the study of the human jaw

The standard illumination set-up for measurement of in-plane displacement in electronic speckle pattern of interference (ESPI) requires the use of two oblique coherent beams for the illumination of the object. These two beams define a direction in the plane perpendicular to the optical axis in which the displacement can be measured, while in the perpendicular direction the interferometer has no sensitivity. In this paper, a new ESPI system for the measurement of in-plane displacements is used. The novelty presented by this assembly is the use of optical fibres to split and guide the light beams. In this way, it is possible to vary with great precision and ease the direction of the projected beams and, consequently, the direction of the plane in which the displacements undergone by the object can be studied. This set-up makes possible the study of objects with complex geometries, which have deformations with unknown symmetry. We present results obtained with this interferometer applied to the study of the mechanical behaviour of the human jaw.