A method and system for 3D surface mapping system using a plurality of image sensors, each image sensor associated with an optical flow processor, each image sensor sharing a substantially coaxial optical path from the scene to a beam splitter and having substantially non-coaxial optical paths between the beam splitter and the image sensor such that the optical magnification of each optical path varies differently with the distance between the system and the surface of interest. The ratio of detected optical flows combined with the parameters of the two optical paths and the baseline between the image sensors is used to compute the Z-distance from the optical center of the image sensors to the surface.