Self-compensated heterodyne laser interferometer

The heterodyne laser interferometer has gained popularity in applications a s an encoder system in ultra-precision machines. it can provide ultra high resolution, which satisfies the requirements of ultra-precision machines. T he difficulty of using a laser interferometer is the elimination of the eff ects of change of the refractive index of air whether by variation in envir onmental conditions or by external effects like air movement, air vibration and mechanical vibration. This paper presents a new technique for the elim ination of the effect of refractive index when using a heterodyne laser int erferometer. The preliminary results showed that this set-up has a better s tatic error when compared to an industrial laser system.