Verification of the Accuracy of a CO2Laser Interferometer for Distance Measurement

Abstract
The accuracy of a 10.6 μm CO2 laser interferometer for distance measurements is determined experimentally. The frequency of a commercial wavelength-stabilized CO2 laser is determined by comparison with a reference CO2 laser. A refractometer is used to measure the refractive index of moist air in the 10 μm wavelength region, within an uncertainty of 5 × 10-8. The performance of the CO2 system for length measurement is then verified by comparison with a wavelength-calibrated 0.63 μm He-Ne system, over distances up to 5 m. The result shows that the CO2 laser interferometer can measure distances with an accuracy of better than 5 × 10-8 in atmospheric air.