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Journal of Electronic Imaging

Influence of illumination on dark current in charge-coupled device imagers
Author(s): Ralf Widenhorn; Ines Hartwig; Justin C. Dunlap; Erik Bodegom
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Paper Abstract

Thermal excitation of electrons is a major source of noise in charge-coupled-device (CCD) imagers. Those electrons are generated even in the absence of light, hence, the name dark current. Dark current is particularly important for long exposure times and elevated temperatures. The standard procedure to correct for dark current is to take several pictures under the same condition as the real image, except with the shutter closed. The resulting dark frame is later subtracted from the exposed image. We address the question of whether the dark current produced in an image taken with a closed shutter is identical to the dark current produced in an exposure in the presence of light. In our investigation, we illuminated two different CCD chips with different intensities of light and measured the dark current generation. A surprising result of this study is that some pixels produce a different amount of dark current under illumination. Finally, we discuss the implication of this finding for dark frame image correction.

Paper Details

Date Published: 1 July 2009
PDF: 8 pages
J. Electron. Imag. 18(3) 033015 doi: 10.1117/1.3222943
Published in: Journal of Electronic Imaging Volume 18, Issue 3
Show Author Affiliations
Ralf Widenhorn, Portland State Univ. (United States)
Ines Hartwig, Portland State Univ. (United States)
Justin C. Dunlap, Portland State Univ. (United States)
Erik Bodegom, Portland State Univ. (United States)

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