A touch screen system configured to detect a displacement of a cover sheet when pressure or force is applied to the cover sheet upper surface. A light source and photodetector are configured to be in optical communication by reflection of light from the light source from the lower surface of the cover sheet. A displacement of the coversheet changes the amount of reflected light that falls upon the detector. The detector signal can be used to measure the amount of displacement, as well as the time-evolution of the displacement. The touch-screen system can be interfaced with a touch-sensitive display unit to form a display system having both pressure-sensing capability and touch-sensing capability.