Development of an Area Image Sensor Pixel for an X-Ray Detector

Abstract

Area photodetector devices (image sensors) are the main imaging element of digital X-ray systems used in medicine today. Since the cost of a medical diagnostics error is very high, the requirements imposed on the image sensor are very strict. We consider a sequence of procedures for the development of an area image sensor for biomedical X-ray investigations, which must reliably distinguish low-contrast details down to 80–100 µm. The development is aimed, in particular, at combining different parameters for different tasks, which require either a high frame rate at a low digit capacity or a wide dynamic range in the slow image sensing mode. The most important parameters of an image sensor are the fill factor of an optical pixel (photosensitive cell) and the quantum efficiency. The pixel layout and topology are proposed and a solution of merging the four neighboring photocells in a separate functional group (superpixel) with a large sensitive area and a potential well is found. The calculation and simulation allow us to develop specific recommendations and requirements on the photodetector for the developed X-ray sensitive panel, and determine the frame and bit rate ranges in the transmission lines.