Specular reflection is an important issue for an iris acquisition imaging system. This thesis is aimed to investigate the influence of near IR source on the image quality as well as optimizing arrangement of light source to enhance segmentation process. The arrangement of the light source manipulates the specular positions on iris region. More specifically, by controlling the geometric relations of subject, light source and image acquisition is able to avoid the specular reflections overlapping with iris information region. In this thesis, we proposed a complete geometric model to predict the specular reflections. The effectiveness and practicability of the proposed modeling have been validated by a series of experimental testing.