Influence of beam divergence on Michelson interferometer

Abstract

Aiming at the influence of beam divergence angle on the distance measuring system such as Michelson interferometer, the Michelson interference system model of point light source is established. The influence of beam divergence on the interference signal is calculated by numerical simulation. The theoretical calculation results show that when the incident light source has a divergence angle, the optical path difference between the reference path and the measurement path will cause the size of the measurement spot and the reference spot to be inconsistent, and the interference spot will show circular interference fringes, resulting in energy loss and interference efficiency reduction. Meanwhile, the interference signal intensity will decrease with the increase of the measurement path distance and beam divergence angle. By reducing the divergence angle, the interference signal can maintain high intensity. Finally, an equivalent Michelson interference optical system is built based on a He-Ne laser with a divergence angle of 1.7 mrad. The experiment results show that the interference signal intensity is significantly improved after the addition of the collimator. The results of this paper show that for the measurement system such as Michelson interferometer, reducing the beam divergence angle to 0.5 mrad can obtain relatively high interference signal intensity during the measurement.