Patent ID: 8237685

Claim:
A method for determining a material of an object, based on its optical characteristics, within boundaries of a touch screen, the touch screen including on its periphery a plurality of light sources (L i , i=1 to N) and sensors (S j , j =1 to M), the method comprising the steps of: transmitting a light sequentially from each of the light sources to the object within the boundary of the touch screen, wherein a portion of the sequentially transmitted light is one or more of (i) absorbed, (ii) reflected, and (iii) transmitted by the object; detecting a respective presence of the sequentially transmitted light at each of the sensors, wherein one or more of the sensors receive varying degrees of the sequentially transmitted light; determining a respective distance from the object (i) to each of the light sources and (ii) to each of the sensors; determining a respective reflective index (n 2 ) of the object at each of the sensors, wherein each reflective index is based on (i) a light intensity (I r ) after being reflected from the object, (ii) a light intensity (I i ) just before light reaches a surface of the object, and (iii) a reflective index close to one; and determining the material of the object based on the respective determined reflective indices.