Integrating stereo and photometric stereo to monitor the development of glaucoma

shading offers hope of dense depth measurements; however, it has to contend with the spatially varying albedo of the surface of the optic disk. Fortunately, we can control the lighting and positions of the stereo pair of cameras. Section 2 describes how we can exploit this degree of freedom to apply a technique akin to homomorphic filtering to separate the contribution of albedo and reflectance map. This provides an estimate of a component of the gradient V' z of the disk surface, and after integration, an estimate of the topography of the disk. The gradient components are noisy, so Section 3 describes how we regularise them using a weak prior model of the structure of the disk. We report progress on a system to monitor the development of glaucoma by measuring the topography of the optic disk. The need for an accurate method for doing this using passive vision is explained. Sparse depth measurements from stereo matching of blood vessels provide insufficient constraint for reconstructing the surface of the optic disk. Shape-from-shading has to contend with a spatially-varying albedo. We show how a particular arrangement of fundus cameras allows us to apply a technique akin to homomorphic filtering to recover estimates of dz/dx that can be smoothed by appropriate regularisation. Stereo is integrated with this photometric stereo depth estimates. Examples of an artificial object and optic disk surface reconstructions are presented.