Flat panel fingerprint optical sensor using TFT technology

A 3.2×3.0 inch2 optical type fingerprint scanning flat panel is designed and implemented. The driving system is based on the passive pixel sensor (PPS) array with amorphous silicon (a-Si) TFT technology. The sensing layer of the optical sensor is composed of the Si-nanocrystals (Si-NCs) embedded in the dielectric material. The pixel density is over 500 PPI and the gray levels are up to 256 with excellent linearity.