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Proceedings Paper

Measurements of dark current in a CCD imager during light exposures
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 to different intensities of light and measured the dark current generation. A surprising conclusion of this study is that some pixels produce a different amount of dark current under illumination. Finally, we discuss the implications that this has for dark frame image correction.

Paper Details

Date Published: 4 March 2008
PDF: 9 pages
Proc. SPIE 6816, Sensors, Cameras, and Systems for Industrial/Scientific Applications IX, 68160B (4 March 2008); doi: 10.1117/12.769082
Show Author Affiliations
Ralf Widenhorn, Portland State Univ. (United States)
Digital Clarity Consultants (United States)
Ines Hartwig, Portland State Univ. (United States)
Justin C Dunlap, Portland State Univ. (United States)
Erik Bodegom, Portland State Univ. (United States)
Digital Clarity Consultants (United States)


Published in SPIE Proceedings Vol. 6816:
Sensors, Cameras, and Systems for Industrial/Scientific Applications IX
Morley M. Blouke; Erik Bodegom, Editor(s)

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