Published In
Journal of Electronic Imaging
Document Type
Article
Publication Date
9-1-2009
Subjects
Charge coupled devices, CCD cameras, Image processing -- Digital techniques, Digital cameras -- Mathematical models
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.
DOI
10.1117/1.3222943
Persistent Identifier
http://archives.pdx.edu/ds/psu/9216
Citation Details
Widenhorn R, Hartwig I, Dunlap JC, Bodegom E; Influence of illumination on dark current in charge-coupled device imagers. J. Electron. Imaging. 0001;18(3):033015-033015-8.
Description
Copyright 2009 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.