Michelson apparatus is a dual beam interferometer: two beams generated by amplitude division can interfere. One semireflecting plate, called separator, divides one incident light beam into two beams, of identical intensity. Each beamis then reflected by a mirror. At the interferometer output, both beams, which have an optical path  difference dependingon the distance & the angle between the  mirrors, interfere ; generating therefore, an “interference pattern”. One of the two mirrors is fitted on a trolley, which enables to vary the  path difference, in rotating one micrometric screw. On the other hand, a  complete set of screws, intended to adjust the plate & mirrors  positioning.

Michelson interferometer is constituted of mirrors: Ø 40 mm, and  glass plates Ø 80 mm, in order to ensure a better visibility of the  interference gratings. Plates & mirrors are anti-reflection  processed, and have flatness of Lambda/20.  The assembly is protected by infra red filter, Ø 50 mm. Screws & adjustment devices are made of stainless steel. The fine adjustment is geared down by a torsion system. The translation plate is guided by ball bearing systems. The motion range: 25 mm, is carried out by a micrometric screw with digital display  (micrometric accuracy). The main plate is made of solid steel with anti-vibration feet. The adjustment screw of the compensating device angle is external,  giving better access. Anti-unscrewing stop ends are also fitted on the  moving mirror adjustment screws.