A scintillator-coated phototransistor pixel sensor with dark current cancellation

An investigation of a prototype integrating phototransistor-based CMOS Active Pixel Sensor (APS) circuit coated with scintillating material for intra-oral dental X-ray imaging is presented. Cancellation of the leakage current using a dummy phototransistor technique was tested and proved efficient. Measured results showed a minimal dark current whose value is in the photodiodes ranges. The low values of the leakage current that was achieved together with the low X-ray direct absorption results in a high input dynamic range which, in addition to its high optical sensitivity, makes the phototransistor an excellent candidate to replace the presently dominating CCD systems