Sensitivity study in moiré interferometry under spherical illumination

In the present work, a simple moire interferometer, which commonly is sensitive to in-plane displacement, is studied. In contrast to traditional in-plane moire interferometric technique, we use two spherical wavefronts. This kind of illumination produces a sensitivity vector varying with the position. Therefore, it is capable of detecting in-plane and (a whitish) out-of-plane deformations due to the use of divergent beams. Uncertainty to each component of the displacement vector is calculated and discussed. It is shown each component of the sensitivity vector, which should be examined in the stage of planning an interferometric measurement experiment, have to minimize the required component uncertainty. This analysis is made for a flat and spherical object surface. Experimental results for the displacements of a rigid object are presented, which show the measured displacement components with the highest sensitivity.