Digital indirect-detection x-ray imagers with microlens focusing: effects of Fresnel reflections from the microlens layer

Nicholas Petrick; Aldo Badano; Heang-Ping Chan; Berkman Sahiner; Lubomir M. Hadjiiski

doi:10.1117/12.479995

5 June 2003 Digital indirect-detection x-ray imagers with microlens focusing: effects of Fresnel reflections from the microlens layer

Nicholas Petrick, Aldo Badano, Heang-Ping Chan, Berkman Sahiner, Lubomir M. Hadjiiski

Author Affiliations +

Proceedings Volume 5030, Medical Imaging 2003: Physics of Medical Imaging; (2003) https://doi.org/10.1117/12.479995
Event: Medical Imaging 2003, 2003, San Diego, California, United States

Abstract

We have been investigating whether a microlens layer placed between the phosphor and the photodetector can improve indirect detection x-ray imagers. Using a simulation study, we analyzed the light collection properties of the proposed imager taking into account Fresnel reflection and transmission properties of the lenses and the screen. A digital x-ray imager combining an 82-μm-thick Gd₂O₂S:Tb phosphor screen, a fused silica microlens layer, and a 127-μm pixel pitch photodetector (optical fill factor of 57%) were modeled. The light collection for the prototypes varied from 53% to 69% for lens thicknesses ranging from 10 to 50 μm. The full-width half-maximum (FWHM) of the light spread function ranged from 177-192 μm. 4-8% of the light was reflected back into the phosphor screen when correctly taking into account Fresnel reflections for these prototype imagers. In comparison, 56% of the light was collected and the FWHM of the light spread function was 174 μm for a conventional imager with the screen in direct contact with the photodetector. We observed that the light collection was overestimated by 6-9% but the spread functions were basically unaffected when the Fresnel assumption was not utilized in the simulations. This study shows that a properly designed microlens layer can more than offset Fresnel losses, thereby producing an improved digital x-ray imager.

Citation Download Citation

Nicholas Petrick, Aldo Badano, Heang-Ping Chan, Berkman Sahiner, and Lubomir M. Hadjiiski "Digital indirect-detection x-ray imagers with microlens focusing: effects of Fresnel reflections from the microlens layer", Proc. SPIE 5030, Medical Imaging 2003: Physics of Medical Imaging, (5 June 2003); https://doi.org/10.1117/12.479995

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