A display panel incorporates the functionality to determine the three dimensional position of a light reflecting or emitting object (400, 401, 410) in front of a display surface (100). An array of sensors (310) is disposed in the panel and provided with optical arrangements such as apertures in masks (321, 331) within the panel. These arrangements prevent light incident normally on the display surface (100) from reaching the sensors (310) but allow obliquely incident light (602, 604) to reach the sensors (310). The object position is determined by analyzing the sensor responses.