In-line measurement of phase-shift non linearity
Institut d'Optique/CNRS/Université de Paris-Sud,
B.P. 147, 91403 Orsay Cedex, France
One of the principal limitations of phase-shift interferometry is the shift non linearity. We propose two methods for measuring this non linearity, one applicable to the registration of a limited number of interferograms (3 or 4) and the other applicable to many interferograms (typically 16). We see two main advantages in these methods: first, they require no extra instrumentation, and, secondly, shift non linearity is measured in situ, that is particularly important in the case of mechanical phase shift. Experiments confirm the validity of the corrections , allowing in our case reduction of systematic errors by 30 to 45%.
© EDP Sciences, 1999