Pixelated Photoinduced Discharge Readout X-Ray Detector Using 450-nm LED Line Beam

This paper describes a study on a novel X-ray detector with photoinduced discharge (PID) readout devices. Especially, we demonstrated optical scanning X-ray imaging devices based on intrinsic hydrogenated amorphous silicon (i-a-Si:H) PID readout layer, on which a pixelated metal layer, molybdenum, is formed as a charge accumulation layer of $200~\mu \text{m}$ pitch for clearly defining the pixel in the lateral and longitudinal directions. We decided to use i-a-Si:H as a readout layer instead of amorphous selenium(a-Se) layer because the material of a-Se does not withstand standard wet fabrication processes like lift-off wet process. An X-ray absorption layer of $500~\mu \text{m}$ thick a-Se is formed by a thermal evaporation process. To optically switch on the i-a-Si:H PID readout layer, we use a narrow line-beam with a beam width of $50~\mu \text{m}$ consisting of a blue LED array, optical films, and GRIN lens array. The pixelated PID readout X-ray detector is $512\times512$ image resolutions with a $200~\mu \text{m}$ pitch, and the overall active dimension is 10.24 cm $\times10.24$ cm. The sensitivity of the pixelated PID readout X-ray detector is 302 pC/cm $^{2}\cdot $ mR at Normal X-ray Tube conditions (IEC66220-1). According to MTF measurement results, the value of MTF0.1(10%) is measured at near 2.5 1/mm in the column direction scanning while the value is measured at 1.9-2.5 1/mm in the row direction scanning.