Effects of the environment on refractive index of air in long gauge block interferometer.

The environment parameters, i.e. temperature, pressure, humidity and CO2 concentration affecting the refractive index of air play an important role on the long gauge block measurement using interferometer. In this paper, the environment parameters in a measurement chamber had been continuously investigated more than 24h. The refractive index was then calculated by using an updated Edlén equation. The stability of the refractive index of air in the experiment is 0.1×10−6 with the measurement uncertainty of 4.32×10−8 at the confidential level k =2. While the sensitivity of the pressure of air was small, it was an evidence that the pressure of air mainly contributed to the stability of the refractive index of air due to its large variation. Furthermore, the calculated refractive index of air was employed to correct the length of long gauge blocks. The correction for 1m long gauge block in interferometer system is 0.270mm, 0.269mm and 0.267mm which are respectively based on the three laser wavelengths at 532nm, 633nm and 780nm. [ABSTRACT FROM AUTHOR]