The Instrument Transfer Function

By Zygo

An interferometer is a common instrument for measuring optical surfaces to very high precision that can be applied with care to enable extremely low uncertainty measurements to address tight metrology requirements. The ability of an interferometer to quantify mid-spatial frequency content is defined not only by its sampling density (camera resolution), but also by the many critical design aspects of the optical illumination and imaging system. The instrument transfer function (ITF) quantitatively characterizes the response of the instrument as a function of spatial frequency.