Minimization of systematic errors in phase-shifting interferometry: evaluation of residuals

While phase-shifting interferometry is now used widely to map the deviations of optical surfaces from a reference plane or reference sphere, the accuracy of such measurements is limited by systematic errors due to several causes. It has been shown that these systematic errors can be minimized by a simple averaging technique. We present calculations of the residual errors in some typical cases, which confirm that, with this technique, the residual errors can be reduced quite easily to negligible levels.