A new method for compensating and measuring any motion of 3D-objects in holographic interferometry: Recent developments

A method allowing the compensation and the measurement of the complex motion of an object, the amplitude of which can be greater than the coherence length of the laser used for the holographic recording, is proposed. The method, called Complete Motion Compensation, can be used for real-time, time-average, and double-exposure holographic interferometry even in the case of high-speed phenomena. The rigid block composed by the holographic image and by illuminating object beam is moved to exactly superimpose the object and its holographic image (infinite fringe, i.e., exact compensation of the optical path variations). A perfect optical path compensation only occurs for rigid body motion. In the case of the deformation of an object, the compensation can be done only for a small area. The whole object surface deformation can be studied spot by spot. Rigid displacements and deformations can be quantified by measuring the displacements of the whole rigid block without taking account of the fringe spacing or localization distances.