Interferometer applications
Light interference - Theory and applications

As mentioned in the introduction, light interference can be used to highlight very small variations in an optical path in relation to another taken as a reference. Visual or photometric observation of fringe deformation enables sensitivities ranging from a tenth of an inter-fringe for visual observation, to a hundredth or a few thousandths of an inter-fringe for more complete analysis. The latter sensitivity is only justified if the reference beam can guarantee stability of the same order.