Optical Sensing Circuit Using Low-Temperature Polycrystalline Silicon p-Type Thin-Film Transistors and p–Intrinsic–Metal Diode for Active Matrix Displays with Optical Input Functions

概要

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An optical sensing circuit composed of low-temperature polycrystalline silicon (LTPS) p-type thin-film transistors (TFTs) and a p–intrinsic–metal (p–i–m) diode is proposed for image scanning and touch sensing functions. Because it is a very difficult challenge to integrate both display pixels and optical sensing circuits into the restricted pixel area, the number of additional devices and control signal lines must be minimized. Therefore, two p-type TFTs, one p–i–m diode, one capacitor, and one signal line are added to display pixel for the proposed optical sensing circuit. Active matrix liquid crystal display (AMLCD) and active matrix organic light-emitting diode (AMOLED) pixels with the proposed optical sensing circuit have image scanning and touch sensing functions, respectively. Through the measurement of the proposed circuit under the condition of incident light varying from 0 to 10,000 lx, we verified that the dynamic and output ranges of the proposed circuit are 30 dB and 1.5 V, respectively.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2009-03-25