A method, device and computer program product for determining the material of an object based on its optical characteristics is disclosed. More specifically, the method operable on a touch screen that includes on its periphery a plurality of light sources (Li, i=1 to N) and sensors (Sj, j=1 to M), comprises the steps of transmitting a light from each of the light sources to an object within the boundary of the touch screen, determining a distance from the object to each of the light sources and each of the sensors, detecting the presences of the transmitted light at each of the sensors, determining, at each of the sensors a reflective index, n2 of the object and determining the object material based on the determined reflective indices.