Image Acquisition for High Accuracy Interferometry

In phase shifting interferometry, the image acquisition electronics have largely been ignored, because the overall measurement accuracy has generally been limited by the quality of the reference wave. A recently developed interferometer, the phase shifting diffraction interferometer,[1] provides a high quality reference wave, which has been measured to be better than λ/8000 rms. With such a reference wave, the interferometer accuracy then becomes limited by systematic errors in the image acquisition electronics. This paper presents a variety of issues that arise when using image acquisition electronics of the sort commonly used in commercial interferometers. A basic fiber interferometer that isolates electronics issues is described, as are simple solutions to some of the errors.