A computer generated phase map and corresponding set of interference fringes calculated from a theoretical prescription of a measured aspheric surface comprises a Computer Generated Reference (CGR) that is used in an interferometer equipped with a spherical and/or flat reference element. moiré fringes created between real interference fringes and the CGR describe the difference between the measured object and its prescription. The moiré fringes can be nulled making the measurement of the aspheric surface analogous to the measurements of the regular spherical and/or flat surfaces.