Heterodyne interferometry using two wavelengths for dimensional measurements

Abstract

Heterodyn interferometry is a powerful tool for high precision distance and vibration analysis. Two wavelength heterodyne techniques become very interesting for absolute distance measurement. It was shown, that a synthetic wavelength can be generated by two shorter ones. This leads also to the techniques to measure optically rougher surfaces because the optical path difference is to be compared with the synthetic wavelength. Further work will be reported.