Imaging performance of a CaWO4/CMOS sensor

Niki Martini; Vaia Koukou; George Fountos; Ioannis Valais; Ioannis Kandarakis; Christos Michail; Athanasios Bakas; Eleftherios Lavdas; Konstantinos Ninos; Georgia Oikonomou; Lida Gogou; George Panayiotakis

doi:10.3221/IGF-ESIS.50.39

Imaging performance of a CaWO4/CMOS sensor

Authors

Niki Martini University of West Attica https://orcid.org/0000-0002-9525-2010
Vaia Koukou University of West Attica https://orcid.org/0000-0003-1722-744X
George Fountos University of West Attica
Ioannis Valais University of West Attica https://orcid.org/0000-0001-6808-0252
Ioannis Kandarakis University of West Attica
Christos Michail University of West Attica https://orcid.org/0000-0001-5863-8013
Athanasios Bakas University of West Attica
Eleftherios Lavdas University of West Attica
Konstantinos Ninos University of West Attica https://orcid.org/0000-0001-5933-0133
Georgia Oikonomou University of West Attica
Lida Gogou University of West Attica
George Panayiotakis Department of Medical Physics, Faculty of Medicine, University of Patras

DOI:

https://doi.org/10.3221/IGF-ESIS.50.39

Keywords:

CaWO4, Phosphors, Medical imaging, APS, CMOS sensors, MTF

Abstract

The aim of this study was to investigate the modulation transfer function (MTF) and the effective gain transfer function (eGTF) of a non-destructive testing (NDT)/industrial inspection complementary metal oxide semiconductor (CMOS) sensor in conjunction with a thin calcium tungstate (CaWO₄) screen. Thin screen samples, with dimensions of 2.7x3.6 cm² and thickness of 118.9 μm, estimated from scanning electron microscopy-SEM images, were extracted from an Agfa Curix universal screen and coupled to the active area of an active pixel (APS) CMOS sensor. MTF was assessed using the slanted-edge method, following the IEC 62220-1-1:2015 method. MTF values were found high across the examined spatial frequency range. eGTF was found maximum when CaWO₄was combined with charge-coupled devices (CCD) of broadband anti-reflection (AR) coating (17.52 at 0 cycles/mm). The combination of the thin CaWO₄ screen with the CMOS sensor provided very promising image resolution and adequate efficiency properties, thus could be also considered for use in CMOS based X-ray imaging devices, for various applications.

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Published

02-09-2019

Issue

Vol. 13 No. 50 (2019): October 2019

Section

SI: Research activities of the Greek Society of Experimental Mechanics of Materi

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