Infrared interferometry based measurement of asphero diffractive optical surface

Diffractive features on lenses are widely used in thermal imaging instruments for chromatic aberration correction and provide a good tool to optical designer for minimizing aberrations and designing a compact imaging system. The measurement of diffractive surface is a challenging task and a standard method used to qualify a diffractive lens is the sag deviation from the designed lens profile. Imperfections in the manufacturing of the diffractive feature may cause scattering and performance loss. In this paper, a method is presented to measure the three dimensional surface profile of a diffractive optical surface using infrared interferometry.