Phase-shifting interferometry with a coupled interferometer : application to optical roughness of gauge blocks

A coupled interferometer consisting of a Michelson interferometer in which one of the mirrors is replaced by a Fizeau interferometer, is presented. The fixed distance of the reflecting surfaces of the Fizeau interferometer can be determined with high precision when the phase-shifting technique is applied to the Michelson interferometer. Formulas for the interference evaluation are derived which are generally valid for coupled interferometers of this particular type