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Influence of illumination on dark current in charge-coupled device imagers

[+] Author Affiliations
Ralf Widenhorn

Portland State University, Department of Physics, Portland, Oregon 97207-0751

Ines Hartwig

Portland State University, Department of Physics, Portland, Oregon 97207-0751

Justin C. Dunlap

Portland State University, Department of Physics, Portland, Oregon 97207-0751

Erik Bodegom

Portland State University, Department of Physics, Portland, Oregon 97207-0751

J. Electron. Imaging. 18(3), 033015 (September 08, 2009). doi:10.1117/1.3222943
History: Received April 13, 2009; Revised July 21, 2009; Accepted July 22, 2009; Published September 08, 2009
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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.

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© 2009 SPIE and IS&T

Citation

Ralf Widenhorn ; Ines Hartwig ; Justin C. Dunlap and Erik Bodegom
"Influence of illumination on dark current in charge-coupled device imagers", J. Electron. Imaging. 18(3), 033015 (September 08, 2009). ; http://dx.doi.org/10.1117/1.3222943


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