Investigation Of Gain Non-uniformities in the Two TFT, Current Programmed Amorphous Silicon Active Pixel Sensor For Fluoroscopy, Chest Radiography And Mammography Tomosynthesis Applications

摘要

A 2-TFT current-programmed, current-output active pixel sensor in amorphous silicon (a-Si:H) technology is introduced for digital X-ray imaging, and in particular, for mammography tomosynthesis and fluoroscopy. Pixel structure, operation and characteristics are presented. The proposed APS circuit was fabricated and assembled using an in-house bottom gate inverted staggered a-Si:H thin film transistor (TFT) process. Lifetime, transient performance as well as sensitivity to temperature measurements were carried out. An off-panel current amplifier with double sampling capability required for 1/f noise reduction is proposed and implemented in CMOS 0.18 micron technology. The results are promising and demonstrate that the proposed APS compensates for electrical and thermal stress causing shift in the threshold voltage of a-Si TFTs.