Amorphous Si:H contact linear image sensor with Si3N4blocking layer

An a-Si:H contact linear image sensor for facsimile equipment with high S/N performance has been developed. The keys to the improvement are: (a) The photosensing element has a new structure with Si3N4and p-a-Si:H blocking layers on both sides of photosensitive a-Si:H layer. These blocking layers markedly suppress the dark current while the signal current can passes through the these layers. (b) A novel noise suppression method is proposed and demonstrated. S/N ratios as high as 32 dB is obtained at 0.7 lux-sec exposure. A 960-element, 8 elements/mm contact linear image sensor was fabricated. The optical system had a rod lens array and two yellow-green LED arrays as stable light sources. Performance tests on this sensor show excellent results with 8 lines/mm resolution. Images are satisfactorily recorded using a thermal printer.