Two-Wavelength Phase-Shifting Interferometry With Active Stabilization System.

Abstract

A system for phase stabilization of different interferometric set-ups is presented. A point sensitive high resolution het-erodyne interferometer is integrated into a full field Twyman-Gmen interferometer for optical testing. A phase stability of 0.8 nm (nns) is obtained through a piezo feedback controlled by a computer closed loop control. The system is opted for two-wavelength phase-shifting interferometry (TWPSI) where succesive recordings under well defined phase steps is applied. For optical testing with TWPSI one have to record two sets of phase data with two different wavelengths. These are then used to calculate the phase map corresponding to a longer equivalent wavelength.