Experimental Research On The Influence Of Air Pressure On The Figure Of Optical Elements

The resolution of the atom interferometry gravimeter is better than1μGal(1μGal=1×10^-8m/s²),but its accuracy still needs to be further improved.At present,the wavefront aberrations effect is one of the main limiting factors.The effect of wavefront aberrations is directly related to the figure of optical elements,which is usually measured in atmospheric environment and used to evaluate the influence of wavefront aberrations.However,in order to avoid the influence of the bottom window of the vacuum chamber,the optical elements need to be installed into the vacuum chamber.Does the figure of the optical elements measured in atmospheric environment change after they are installed into the vacuum chamber?In this thesis,the influence of air pressure on the figure of optical elements is studied experimentally.Firstly,the working principle of wavefront sensor is introduced,and the figure measurement method of transmission optical element and the reflection optical element based on the wavefront sensor is introduced.Secondly,the experimental scheme of measuring the figure of optical elements in vacuum is designed,including the design of wavefront sensor optical system,the design of moving and adjusting device and the design of vacuum cavity.Then,in the range of 5.8×10^-2Pa～1.0×10⁵ Pa,the figure of wave plate and mirror with the change of air pressure is measured within the diameter of 27 mm.The experimental results show that the root mean square（RMS）value of the wave plate and mirror figure of the device does not change with the air pressure,and no change of the figure distribution of the optical elements with the air pressure is observed within the error range.Then,the contribution of wave plate and mirror figure to the wavefront aberrations effect under different pressures is calculated.Finally,the figure of the optical elements changing with the air pressure under different fixed pressures is researched,and the experimental results show that under different fixed pressures,the RMS value and the figure distribution of the optical elements hardly change with the air pressure within the error range.For the mirror,the use of glue to fix it can significantly reduce the influence of the installation process on the figure of the optical element.The experimental results in this thesis show that the measurement results of optical element figure in atmospheric environment in this device are still suitable for vacuum environment in this situation,which may provide a support for the evaluation of wavefront aberrations effect in atom interferometry gravimeter.