A servo controlled Fabry-Perot interferometer using capacitance micrometers for error detection

Abstract

A servo controlled Fabry-Perot interferometer using capacitance micrometers to sense departures from parallelism and variations in the mean spacing of the Fabry-Perot plates is described. The parallelism and mean spacing of the plates is maintained over the full 75 mm aperture of the instrument to an accuracy better than the surface quality of the plates ( approximately lambda /150 at 500 nm).