A novel system and novel methods for the active tilt stabilisation of an optical table

摘要

In many high-resolution systems, seismic noise is the ultimate measurement limitation. One of the well-known methods for reducing the seismic noise is pneumatic vibration isolation. Optical tables with pneumatic vibration isolation (pneumatic damping "on") exhibit great long-period (> 1 s) angular oscillations and angular drift. These oscillations, as well as the drift, are often the main limiting factors for measurements. A novel system for the reduction of the low-frequency angular oscillations and drift is presented. A novel discretised algorithm for the optimum stabilisation of different oscillating systems is proposed. The measured tilt noise power spectrum (TNPS) of an optical table (pneumatic damping "on") with and without active tilt stabilisation is presented. The measured angular standard deviation of the optical table (pneumatic damping "on") with active tilt stabilisation over a time period of 2 h was 2·10{sup}(-8) radian. This value is by a factor of 1000 better than without stabilisation. For the estimation of the tilt noise level of the measuring laboratory ground in the frequency range from 3·10{sup}(-6) Hz up to 0.1 Hz, an approximating function is presented. This function allows the user to estimate the tilt amplitude of his laboratory table without stabilisation (pneumatic damping "off").