Active matrix of amorphous silicon multijunction color sensors for document imaging

An integrated color image sensor, made entirely with amorphous silicon (a-Si:H) large-area technology, is presented. The a-Si:H based sensor is a double-junction p-i-n-i-p photodiode that discriminates two spectral bands according to the bias voltage. The active-matrix addressed array has 512×512 pixels with 75 μm pixel pitch and uses thin-film transistors as pixel switches. The array structure and the spectral response are discussed, and color images taken by the system using two bias voltages demonstrate the compatibility of color sensors with large-area active-matrix addressing techniques.