1. A system mountable on a vehicle, the system comprising: a primary camera configured to acquire a plurality of primary images of the environment through the window; a secondary camera adapted to focus on at least a portion of a surface of the window to acquire a secondary image of an obstruction when present on the surface, wherein a region of the window is subtended by respective fields of view of the primary camera and the secondary camera; a light source adapted to illuminate the window with a puke of light, wherein the secondary camera is operated synchronously with the light source; and a processor adapted to process the secondary image to detect the obstruction in the secondary image.