Interferometric-auto-collimation technique for the determination of small angular tilt of a plane mirror

TLDR: In this paper, a common path interferometric auto-collimation technique is proposed for generating Fizeau fringes formed due to interference between two split up plane wave components with angular separation equal to four times of the angular deflection of the plane test mirror.

Abstract: A new common path interferometric auto-collimation technique is proposed. A laser autocollimator is combined with a modified triangular path interferometer for generating Fizeau fringes formed due to interference between two split up plane wave components with angular separation equal to four times of the angular deflection of the plane test mirror. The angular deflection of the plane test mirror is measured either from the fringe spacing or more accurately, from the slope of the optical path difference variation of the interference field obtained by applying polarization phase shifting interferometry. Results for a validation experiment are presented.