High Precision Digital Interferometry: Its Application To The Production Of An Ultrathin Solid Fabry-Perot Etalon

Teflon polishing is capable of producing surfaces flat to 3 nm or better, but its wider application requires suitable testing methods to measure such small residual errors. Digital interferometry solves this problem and, because data can be stored and processed, makes it possible to carry out a variety of tests with high precision. The application of these techniques to the production and testing of a solid Fabry-Perot eta Ion with a diameter of 50 mm, a thickness of 0.352 mm, and a maximum deviation from parallelism of its faces of ±2 nm over the central 30 mm is described.