Patent ID: 8466902

Claim:
A touch panel system comprising: a touchable surface; at least one infrared source integrated in the touch panel system and configured to direct infrared radiation through the touchable surface for illuminating one or more objects that are in contact with or adjacent to the touchable surface with infrared radiation; and a touch panel display configured to illuminate pixels for radiating visible light through the touchable surface, the touch panel display including an active matrix backplane comprising: a plurality of pixel circuits, each pixel circuit comprising a drive transistor directly connected to a common bias line that provides a non-ground voltage reference; a plurality of infrared sensors distributed parallel to the touchable surface and configured to detect reflected infrared radiation incident on the infrared sensors, wherein infrared radiation directed by the at least one infrared source and visible light radiated by the pixels are not incident on the infrared sensors, and wherein reflected infrared radiation directed through the touchable surface by the one or more objects is detected by the infrared sensors; and a capacitor directly connected to the common bias line, to an infrared sensor of the plurality of infrared sensors, and to a readout transistor, wherein if reflected infrared radiation is incident on the infrared sensor: a voltage imposed on the capacitor discharges through the infrared sensor, a charge to reset the voltage on the capacitor flows through the readout transistor, a measure of the reflected infrared radiation incident on the infrared sensor is output based on the charge needed to reset the voltage on the capacitor, and reflected infrared radiation detected by the plurality of infrared sensors is processed to identify a detected infrared image.