Embodiments of a system for displaying images include a light emitting device with a plurality of photo sensors. Each photo sensor includes a PIN diode composed of an N+ doped semiconductor region, a P+ doped semiconductor region, and an intrinsic semiconductor region formed therebetween. An insulated control gate overlaps the intrinsic semiconductor region and is operative to provide the PIN diode with a controllable electric characteristic with respect to a saturation photo current at a saturation voltage.