Dynamic range measurements of a dual camera complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS)

DynAMITe (Dynamic range Adjustable for Medical Imaging Technology) is a recently developed wafer scale (12.8 cm × 13.1 cm) X-ray detector consisting of a Complementary Metal-Oxide-Semiconductor (CMOS) Active Pixel Sensor (APS) coupled to a 150 μm Thallium-activated Cesium Iodide (CsI:Tl) screen. It consists of two cameras: a Sub-Pixel (SP) camera with 50 μm pitch and a Pixel (P) camera with 100 μm pixel pitch. Each camera can support multiple Regions of Interest (ROIs). The combination of different settings (reset voltages, frame rates and destructive or non-destructive readout) for the two cameras allows DynAMITe to achieve a high dynamic range in comparison to other CMOS devices. Mean-Variance analysis was used in this paper to characterise the detector using different reset voltages. A commercial X-ray source was used instead of optical light to perform the Mean-Variance analysis. Overall gain instead of conversion gain can be measured using this method. However, by using a cascaded linear system model, the conversion gain of the detector using different reset voltage can also be estimated. The experimental results have shown that by combining the two cameras at different reset voltages, the dynamic range can be increased to 93.7 ± 0.2 dB from 66.7 ± 0.4 dB (SP) and 66.8±0.1 (P).