Separating corneal reflections for illumination estimation

Eyes exhibit a significant amount of specular reflection and could be used to derive a detailed estimate of frontal illumination. To determine a more accurate estimate of illumination from the environment, iris color and texture should be separated from the specularly reflected light, since they may substantially obscure reflections of the scene. In this paper, a method is presented for separating corneal reflections in an image of human irises. We consider the iris texture to be diffuse, and the observed image color is produced as the sum of the diffuse component and the specular component. A number of methods have been proposed to separate or decompose these two components. To our knowledge, all methods that use a single input image demonstrated success in only limited cases, such as for uniform colored lighting and simple object textures. They are not applicable to irises, which exhibit intricate textures and complicated reflections of the environment. To make this problem feasible, our method capitalizes on physical characteristics of human irises to obtain an illumination estimate that encompasses the prominent light contributors in the scene. Results of the algorithm are presented for eyes of different colors, including light colored eyes for which reflection separation is necessary to determine a valid illumination estimate.