Portland State University. Department of Physics
Term of Graduation
Date of Publication
Master of Science (M.S.) in Physics
Charge coupled devices, Photoelectron spectroscopy
1 online resource (xii, 81 pages)
A systematic study of persistent, or residual, images occurring in CCD imagers and a systematic study of dark current generation in CCD imagers are presented. These effects are a source of unwanted signal in frames, and should be considered where very exact, low light-level signal processing is necessary. For both studies explanatory models and statistical analysis techniques have been developed which enable the derivation of the densities and the characteristic energies. Furthermore the importance of understanding these phenomena in the context of today's low light-level imaging is discussed.
Impurity sites are found to be responsible for residual images. Photoelectrons are trapped at impurity sites and thermally released over time. From the analysis the initial number of loaded traps and a trapping energy of 0.48 eV are found. In addition, the optical excitation rate and the maximum number of available trapping sites per pixel are derived.
For the systematic study of the dark current, a quantization of the dark current and the existence of different pixel groups in a CCD imager are shown. The pixels are split into different groups (negative pixels, non-linear pixels, normal pixels, hot pixels) and models are developed to explain the different sources of dark current. For each group an explanatory model and a statistical analysis technique have been developed which enables the derivation of the densities and the characteristic energies responsible for these effects. For normal pixels the diffusion current is found to cause the dark current. Furthermore, for hot pixels and non-linear pixels an interface state generated component of the dark current is found in addition to diffusion current.
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Mündermann, Lars, "Spectroscopy of Charge-Coupled Devices" (1998). Dissertations and Theses. Paper 6390.