In one embodiment, an optical navigation sensor for a computer mouse is designed to be operable on an optically transparent material. The optically transparent material may include a contact surface on which the mouse sits during normal operation. An optically rough tracking surface is provided below the contact surface. The mouse includes a light source that illuminates an area on the contact surface and an area on the tracking surface. The mouse may include a tracking sensor onto which the illuminated area on the tracking surface is imaged to detect mouse displacement. The mouse may also include a lift sensor that picks up specular light reflected from the illuminated area on the contact surface to generate lift information indicative of whether the mouse has been lifted off the contact surface. Tracking of the mouse displacement may be qualified with the lift information.