ELECTRONIC CONTROL OF THE HORIZONTAL ALIGNMENT OF AN OPTICAL BENCH

A pneumatically damped optical bench has been put under the control of a digital computer in order to keep its table top constantly horizontal, as required when using imaging techniques in measurements involving a liquid-liquid or a liquid-gas interface. The deviation of the table top from true horizontal alignment is continuously monitored by the computer through two synchro transformers. Corrective actions are taken through electro-pneumatic valves. The system has been proven to be able to keep the table top inclination within +/-0.03 mrad over a time period of many hours and has been applied to measurements of interfacial tension using the drop-shape technique.