Phase-shifting multiwavelength dynamic interferometer

The benefits of using two-wavelength measurements to extend the dynamic range of an interferometric measurement are well known. We present a new multi-wavelength interferometer that uses two successive single frame measurements obtained rapidly in time to significantly reduce sensitivity to vibration. At each wavelength, four phase-shifted interferograms are captured in a single image. The total acquisition time for both wavelengths is 100 microseconds, over three orders of magnitude shorter than conventional interferometers. Consequently, the measurements do not suffer from the fringe contrast reduction and measurement errors that plague temporal phase-shifting interferometers in the presence of vibration. In this paper we will discuss the basic operating principle of the interferometer, analyze its performance and show some interesting measurements.