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Physics Faculty Publications and Presentations

CCD cameras -- Calibration

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Articles 1 - 5 of 5

Full-Text Articles in Physics

Dark Current Behavior In Dslr Cameras, Justin Charles Dunlap, Oleg Sostin, Ralf Widenhorn, Erik Bodegom Jan 2009

Dark Current Behavior In Dslr Cameras, Justin Charles Dunlap, Oleg Sostin, Ralf Widenhorn, Erik Bodegom

Physics Faculty Publications and Presentations

Digital single-lens reflex (DSLR) cameras are examined and their dark current behavior is presented. We examine the influence of varying temperature, exposure time, and gain setting on dark current. Dark current behavior unique to sensors within such cameras is observed. In particular, heat is trapped within the camera body resulting in higher internal temperatures and an increase in dark current after successive images. We look at the possibility of correcting for the dark current, based on previous work done for scientific grade imagers, where hot pixels are used as indicators for the entire chip?s dark current behavior. Standard methods ...


Dark Current Measurements In A Cmos Imager, William C. Porter, Bradley Kopp, Justin Charles Dunlap, Ralf Widenhorn, Erik Bodegom Feb 2008

Dark Current Measurements In A Cmos Imager, William C. Porter, Bradley Kopp, Justin Charles Dunlap, Ralf Widenhorn, Erik Bodegom

Physics Faculty Publications and Presentations

We present data for the dark current of a commercially available CMOS image sensor for different gain settings and bias offsets over the temperature range of 295 to 340 K and exposure times of 0 to 500 ms. The analysis of hot pixels shows two different sources of dark current. One source results in hot pixels with high but constant count for exposure times smaller than the frame time. Other hot pixels exhibit a linear increase with exposure time. We discuss how these hot pixels can be used to calculate the dark current for all pixels. Finally, we show that ...


Measurements Of Dark Current In A Ccd Imager During Light Exposures, Ralf Widenhorn, Ines Hartwig, Justin Charles Dunlap, Erik Bodegom Feb 2008

Measurements Of Dark Current In A Ccd Imager During Light Exposures, Ralf Widenhorn, Ines Hartwig, Justin Charles Dunlap, Erik Bodegom

Physics Faculty Publications and Presentations

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 ...


Computation Of Dark Frames In Digital Imagers, Ralf Widenhorn, Armin Rest, Morley M. Blouke, Richard L. Berry, Erik Bodegom Feb 2007

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 ...


Meyer-Neldel Rule For Dark Current In Charge-Coupled Devices, Ralf Widenhorn, Lars Mündermann, Armin Rest, Erik Bodegom Jun 2001

Meyer-Neldel Rule For Dark Current In Charge-Coupled Devices, Ralf Widenhorn, Lars Mündermann, Armin Rest, Erik Bodegom

Physics Faculty Publications and Presentations

We present the results of a systematic study of the dark current in each pixel of a charged-coupled device chip. It was found that the Arrhenius plot, at temperatures between 222 and 291 K, deviated from a linear behavior in the form of continuous bending. However, as a first approximation, the dark current, D, can be expressed as: D=Dₒ exp(−ΔE/kT),where ΔE is the activation energy, k is Boltzmann’s constant, and T the absolute temperature. It was found that ΔE and the exponential prefactor Dₒ follow the Meyer–Neldel rule (MNR) for all of the more ...