Overcoming the refractivity limit in manufacturing environment

We present a tracking interferometer with an intrinsic compensation of the refractive index of air. By using both wavelengths of a frequency doubled Nd:YAG laser the refractive index of air can be determined and compensated by the dispersion. One dimensional benchmark verification experiments in air conditioned and typical harsh, uncontrolled environment show an asymptotic length dependent uncertainty in the order of 0.1 μm/m for distances over 10 m, proofing the potential of this approach for high accuracy measurements in industrial environments.