Self-Compensated Heterodyne Laser Interferometer

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