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Full-Text Articles in Physics
Nonlinear Time Dependence Of Dark Current In Charge-Coupled Devices, Justin Charles Dunlap, Erik Bodegom, Ralf Widenhorn
Nonlinear Time Dependence Of Dark Current In Charge-Coupled Devices, Justin Charles Dunlap, Erik Bodegom, Ralf Widenhorn
Physics Faculty Publications and Presentations
It is generally assumed that charge-coupled device (CCD) imagers produce a linear response of dark current versus exposure time except near saturation. We found a large number of pixels with nonlinear dark current response to exposure time to be present in two scientific CCD imagers. These pixels are found to exhibit distinguishable behavior with other analogous pixels and therefore can be characterized in groupings. Data from two Kodak CCD sensors are presented for exposure times from a few seconds up to two hours. Linear behavior is traditionally taken for granted when carrying out dark current correction and as a result, …
Correction Of Dark Current In Consumer Cameras, Justin Charles Dunlap, Erik Bodegom, Ralf Widenhorn
Correction Of Dark Current In Consumer Cameras, Justin Charles Dunlap, Erik Bodegom, Ralf Widenhorn
Physics Faculty Publications and Presentations
A study of dark current in digital imagers in digital singlelens reflex (DSLR) and compact consumer-grade digital cameras is presented. Dark current is shown to vary with temperature, exposure time, and ISO setting. Further, dark current is shown to increase in successive images during a series of images. DSLR and compact consumer cameras are often designed such that they are contained within a densely packed camera body, and therefore the digital imagers within the camera frame are prone to heat generated by the sensor as well as nearby elements within the camera body. It is the scope of this work …
Characterization And Correction Of Dark Current In Compact Consumer Cameras, Justin Charles Dunlap, Erik Bodegom, Ralf Widenhorn
Characterization And Correction Of Dark Current In Compact Consumer Cameras, Justin Charles Dunlap, Erik Bodegom, Ralf Widenhorn
Physics Faculty Publications and Presentations
A study of dark current in digital imagers within consumer grade digital cameras is presented. Dark current is shown to vary with temperature, exposure time, and ISO setting. Further, dark current is shown to increase in successive images during a series of images. Consumer cameras are often designed to be as compact as possible and therefore the digital imagers within the camera frame are prone to heat generated by nearby elements within the camera body. It is the scope of this work to characterize the dark current in such cameras and to show that the dark current, in part due …
Computation Of Dark Frames In Digital Imagers, Ralf Widenhorn, Armin Rest, Morley M. Blouke, Richard L. Berry, Erik Bodegom
Computation Of Dark Frames In Digital Imagers, Ralf Widenhorn, Armin Rest, Morley M. Blouke, Richard L. Berry, Erik Bodegom
Physics Faculty Publications and Presentations
Dark current is caused by electrons that are thermally exited into the conduction band. These electrons are collected by the well of the CCD and add a false signal to the chip. We will present an algorithm that automatically corrects for dark current. It uses a calibration protocol to characterize the image sensor for different temperatures. For a given exposure time, the dark current of every pixel is characteristic of a specific temperature. The dark current of every pixel can therefore be used as an indicator of the temperature. Hot pixels have the highest signal-to-noise ratio and are the best …
Psf Measurements On Back-Illuminated Ccds, Ralf Widenhorn, Alexander Weber, Morley M. Blouke, Albert J. Bae, Erik Bodegom
Psf Measurements On Back-Illuminated Ccds, Ralf Widenhorn, Alexander Weber, Morley M. Blouke, Albert J. Bae, Erik Bodegom
Physics Faculty Publications and Presentations
The spatial resolution of an optical device is generally characterized by either the Point Spread Function (PSF) or the Modulation Transfer Function (MTF). To directly obtain the PSF one needs to measure the response of an optical system to a point light source. We present data that show the response of a back-illuminated CCD to light emitted from a sub-micron diameter glass fiber tip. The potential well in back-illuminated CCD"s does not reach all the way to the back surface. Hence, light that is absorbed in the field-free region generates electrons that can diffuse into other pixels. We analyzed the …
Residual Images In Charged-Coupled Device Detectors, Armin Rest, Lars Mündermann, Ralf Widenhorn, Erik Bodegom, T. C. Mcglinn
Residual Images In Charged-Coupled Device Detectors, Armin Rest, Lars Mündermann, Ralf Widenhorn, Erik Bodegom, T. C. Mcglinn
Physics Faculty Publications and Presentations
We present results of a systematic study of persistent, or residual, images that occur in charged-coupled device (CCD) detectors. A phenomenological model for these residual images, also known as "ghosting," is introduced. This model relates the excess dark current in a CCD after exposure to the number of filled impurity sites which is tested for various temperatures and exposure times. We experimentally derive values for the cross section, density, and characteristic energy of the impurity sites responsible for the residual images.