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Proceedings Paper

Empirical and theoretical examination of the noise performance of a prototype polycrystalline silicon active pixel array
Author(s): Martin Koniczek; Larry E. Antonuk; Youcef El-Mohri; Albert K. Liang; Qihua Zhao
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Paper Abstract

Active matrix flat-panel imagers (AMFPIs), which typically incorporate a single a-Si:H thin-film transistor (TFT) in each pixel, have become ubiquitous in diagnostic x-ray imaging by virtue of many advantages, including good radiation damage resistance and the economic availability of monolithic, large area backplanes. However, under conditions of low exposure per image frame, such as encountered in fluoroscopy, digital breast tomosynthesis and breast cone-beam CT, AMFPI performance degrades due to the effect of additive noise primarily originating from the acquisition electronics. To overcome this limitation, while retaining the advantages of AMFPIs, large area imagers can be fabricated using polycrystalline silicon (poly-Si) TFTs configured to form in-pixel amplifiers. Such active pixel (AP) circuits provide signal enhancement prior to readout, thereby largely overcoming the effect of additive noise, as well as facilitating correlated multiple sampling (CMS). In this paper, early results of an examination of the noise performance of a poly-Si AP prototype array are reported. The array consists of pixel circuit designs incorporating a single-stage amplifier with three TFTs and was operated at 25 fps using CMS techniques. Noise performance is compared to results obtained from sophisticated circuit simulations which account for TFT thermal and flicker noise. Noise is found to depend on many variables, including the size of the source-follower TFT, the reset voltage, the addressing time and the sampling technique – with noise levels from individual pixels as low as 715 e. The circuit simulations were found to reproduce the trends for noise as a function of the aforementioned variables.

Paper Details

Date Published: 9 March 2018
PDF: 8 pages
Proc. SPIE 10573, Medical Imaging 2018: Physics of Medical Imaging, 105730L (9 March 2018); doi: 10.1117/12.2294571
Show Author Affiliations
Martin Koniczek, Univ. of Michigan (United States)
Larry E. Antonuk, Univ. of Michigan (United States)
Youcef El-Mohri, Univ. of Michigan (United States)
Albert K. Liang, Univ. of Michigan (United States)
Qihua Zhao, Univ. of Michigan (United States)

Published in SPIE Proceedings Vol. 10573:
Medical Imaging 2018: Physics of Medical Imaging
Joseph Y. Lo; Taly Gilat Schmidt; Guang-Hong Chen, Editor(s)

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