Articles you may be interested inScintillator high-gain avalanche rushing photoconductor active-matrix flat panel imager: Zero-spatial frequency xray imaging properties of the solid-state SHARP sensor structure Med. Phys. 39, 7102 (2012); 10.1118/1.4760989 2 ∕ 3 in. ultrahigh-sensitivity image sensor with active-matrix high-efficiency electron emission device J. Vac. Sci. Technol. B 28, C2D11 (2010); 10.1116/1.3271163 High dynamic range active pixel sensor arrays for digital x-ray imaging using a -Si : H J. Vac. Sci. Technol. A 24, 850 (2006); 10.1116/1.2192526 X-ray detection by direct modulation of an optical probe beam-Radsensor: Progress on development for imaging applications Rev. Sci. Instrum. 75, 3995 (2004); 10.1063/1.1790055X-ray-induced recombination effects in a-Se-based x-ray photoconductors used in direct conversion x-ray sensors J.The factors determining the x-ray sensitivity of HgI 2 and PbI 2 as direct detector materials for large area matrix addressed x-ray image sensors are described, along with a model to explain their different properties. The imaging studies are made on test arrays with 512ϫ512 pixels of size 100 m. The x-ray sensitivity and spatial resolution are reported, along with measurements of the various mechanisms that influence the sensitivity, such as charge collection, x-ray absorption, fill factor, and image lag. The spatial resolution of PbI 2 decreases with increasing film thickness, but this effect is not observed in HgI 2 . The x-ray response data are used to compare the sensitivity to the theoretical values for the ionization energy and to identify the various loss mechanisms. We find that the sensitivity of HgI 2 can be explained by a few small and well characterized loss factors. This material exhibits good spatial resolution, high fill factor, and high charge collection. PbI 2 films exhibit lower sensitivity, principally attributable to a very large image lag. We propose that the x-ray response of the two materials is distinguished by their different depletion layer properties, and present a model that accounts for the sensitivity, image lag, and spatial resolution of PbI 2 .
We report on a-Si direct detection x-ray image sensors with polycrystalline Pb12, and more recently with Hg12. The arrays have 100 micron pixel size and, we study those aspects of the detectors that mainly determine the DQE, such as sensitivity, effective fill factor, dark current noise, noise power spectrum, and x-ray absorption.Line spread function data show that in the Pb12 arrays, most of the signal in the gap between pixels is collected, which is important for high DQE. The leakage current noise agrees with the expected shot noise value with only a small enhancement at high bias voltages. The noise power spectrum under x-ray exposure is reported and compared to the spatial resolution information. The MiT is close to the ideal sinc function, but is reduced by the contribution of K-fluorescence in the PhI2 film for which we provide new experimental evidence. The role of noise power aliasing in the DQE and the effect of slight image spreading are discussed.Initial studies of Hg12 as the photoconductor material show very promising results with high x-ray sensitivity and low leakage current.
Large two dimensional amorphous silicon image sensor arrays offer a new approach to electronic document input and x-ray imaging. The sensor array technology is now capable of image capture at greater than 10 frames/sec and with resolution of 200–400 spi. We describe our new high resolution imaging system, comprising a page-sized sensor array with nearly 3 million pixels, and the accompanying high speed read out and processing electronics. The key technological issues of pixel resolution, sensor fill factor, leakage currents and noise are reviewed. Measurements of a new array architecture are described, in which the sensor is formed as a single continuous film on top of the matrix addressing components.
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