The temperature disturbance and optical system performance analysis

Optical system performance is easily affected by various surrounding conditions, especially the precision optical system, such as interferometer, goniometer, are sensitive to temperature fluctuations. Temperature is an important parameter of the air refractive index. Its fluctuation causes unsteady changes in air density and hence index of refraction changes. So the temperature of the detection room must be controlled in reasonable scope. But the heat released from devices, staff members and luminaires is unavoidable. This study calculates fluid field variations induced by temperature, obtains the air density and temperature distribution by Computational Fluid Dynamics (CFD) software, and then the fluctuations of refractive index are calculated from the density field. The optical path difference (OPD) is then given with density changes, also the OPD RMS values are computed. These data can quantify the influence degree of temperature changes and improve optical design.