Interferometry
Mechanical measurements using optical methods

Light interference is characterized by the observation of alternately dark and bright bangs in the area common to two beams. This phenomenon is only visible under certain conditions when the light waves are coherent in time and space. In practice, this means using a laser source that is considered coherent. To take advantage of this phenomenon, a beam of wavelength λ is split in two. By recombining these beams at an angle α, the bangs observed are a function of the optical path difference between the two (figure 29 ).