A novel method to set the proper phase steps, as used in phase-stepped inte
rferometry, is presented. It is indicated how and when this method can be u
sed. With only two images one can deduce the relative phase step between th
em by calculating the correlation between the two images. The error of the
proposed method is shown to be smaller than 0.1%. (C) 1999 Optical Society
of America. OCIS codes: 120.2650, 120.3180, 120.5070.