Low noise, large area CMOS X-ray image sensor for C.T. application

A novel CMOS X-ray active pixel sensor for indirect C.T. X-ray detection has been developed. Noise reduction by reducing the detector junction capacitance is applied to increase the SNR, instead of increasing the sensitivity. For this purpose a new low capacitance, a low dark current dot type photo diode based on minority diffusion has been developed. The dynamic range is expanded to 17 bit by the use of individual in pixel automatic gain control. A photon noise limited detector exhibiting a 20 x 10 pixel array with a frame rate of 3000 frames/sec has been realized in a 1.2µm CMOS process.