A touch screen (TS) comprises a display; a frame with edges positioned opposite each other around the display; at least a first sensor array and at least a second sensor array, wherein each of the sensor arrays has a plurality of light transmitters and a plurality of light sensors, and wherein the at least first sensor array and the at least second sensor array are disposed on the first edge and the second edge of the frame, respectively, wherein the transmitters of the first sensor array are facing the light sensors on the second sensor array positioned on two opposing edges of the frame; and at least one physical obstacle located on the third edge or the fourth edge, for reducing stray light scattered or reflected by third edge or the fourth edge and arriving to the light sensors.