We propose a novel two-dimensional contact-type image sensor using amorphous silicon photo-transistors (APTs) in order to form a compact image scanner. Each pixel of the sensor consists of an APT, a storage capacitor, and an amorphous silicon thin-film transistor (a-Si TFT). We have made a prototype 140 × 240-pixel sensor with a pixel size of 160 μm square. It is confirmed that the prototype APT sensor can detect an image under room light. Exposure for gray scale images is in the range of 10^<-1> to 7 lx・s. This TFT-switched, two-dimensional contact-type image sensor is promising for large-area applications because the process for APTs is fully compatible with that for conventional a-Si TFTs.
