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• 11. [Article] Influence of Illumination on Dark Current in Charge-Coupled Device Imagers

  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 ...

  Citation × Citation Citation Abstract Copy Title: Influence of Illumination on Dark Current in Charge-Coupled Device Imagers Author: Widenhorn, Ralf, Hartwig, Ines, Dunlap, Justin Charles, Bodegom, Erik Year: 2009 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. Title: Influence of Illumination on Dark Current in Charge-Coupled Device Imagers Author: Widenhorn, Ralf, Hartwig, Ines, Dunlap, Justin Charles, Bodegom, Erik Year: 2009 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. Close

• 12. [Article] Computational Approach to Dark Current Spectroscopy in CCDs as complex systems. II. Numerical Analysis of the Uniqueness Parameters Evaluation

  The evaluation of the uniqueness parameters of the temperature dependence in CCDs is difficult to the considerable number of input parameters and to the strongly nonlinear (exponential) theoretical relations. ...

  Citation × Citation Citation Abstract Copy Title: Computational Approach to Dark Current Spectroscopy in CCDs as complex systems. II. Numerical Analysis of the Uniqueness Parameters Evaluation Author: Tunaru, Ionel, Widenhorn, Ralf, Iordache, Dan A., Bodegom, Erik Year: 2011 The evaluation of the uniqueness parameters of the temperature dependence in CCDs is difficult to the considerable number of input parameters and to the strongly nonlinear (exponential) theoretical relations. For this reason, the elaborated computer programs are very sensitive to the choice of the zero-order approximations of the effective (Si) energy gap, and of the weights associated to the experimentally determined dark current. The main goal of this work was to study the rather narrow stability domains of the zero-order approximations, which lead to attractors with physical meaning. It was found that the stability domains are surrounded by (usually in this order): other fields leading to oscillations, pseudo-convergence (false attractors, described by non-physical values of the studied parameters) or instability fields, which were studied also in detail. Title: Computational Approach to Dark Current Spectroscopy in CCDs as complex systems. II. Numerical Analysis of the Uniqueness Parameters Evaluation Author: Tunaru, Ionel, Widenhorn, Ralf, Iordache, Dan A., Bodegom, Erik Year: 2011 The evaluation of the uniqueness parameters of the temperature dependence in CCDs is difficult to the considerable number of input parameters and to the strongly nonlinear (exponential) theoretical relations. For this reason, the elaborated computer programs are very sensitive to the choice of the zero-order approximations of the effective (Si) energy gap, and of the weights associated to the experimentally determined dark current. The main goal of this work was to study the rather narrow stability domains of the zero-order approximations, which lead to attractors with physical meaning. It was found that the stability domains are surrounded by (usually in this order): other fields leading to oscillations, pseudo-convergence (false attractors, described by non-physical values of the studied parameters) or instability fields, which were studied also in detail. Close

• 13. [Article] Dark Current Measurements in a CMOS Imager

  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 ...

  Citation × Citation Citation Abstract Copy Title: Dark Current Measurements in a CMOS Imager Author: Porter, William C., Kopp, Bradley, Dunlap, Justin Charles, Widenhorn, Ralf, Bodegom, Erik Year: 2008 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 for low bias settings with universally zero counts for the dark frame one still needs to correct for dark current. The correction of thermal noise can therefore result in dark frames with negative pixel values. We show how one can calculate dark frames with negative pixel count. Title: Dark Current Measurements in a CMOS Imager Author: Porter, William C., Kopp, Bradley, Dunlap, Justin Charles, Widenhorn, Ralf, Bodegom, Erik Year: 2008 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 for low bias settings with universally zero counts for the dark frame one still needs to correct for dark current. The correction of thermal noise can therefore result in dark frames with negative pixel values. We show how one can calculate dark frames with negative pixel count. Close

• 14. [Article] Measurements of dark current in a CCD imager during light exposures

  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 ...

  Citation × Citation Citation Abstract Copy Title: Measurements of dark current in a CCD imager during light exposures Author: Widenhorn, Ralf, Hartwig, Ines, Dunlap, Justin Charles, Bodegom, Erik Year: 2008 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 to different intensities of light and measured the dark current generation. A surprising conclusion of this study is that some pixels produce a different amount of dark current under illumination. Finally, we discuss the implications that this has for dark frame image correction. Title: Measurements of dark current in a CCD imager during light exposures Author: Widenhorn, Ralf, Hartwig, Ines, Dunlap, Justin Charles, Bodegom, Erik Year: 2008 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 to different intensities of light and measured the dark current generation. A surprising conclusion of this study is that some pixels produce a different amount of dark current under illumination. Finally, we discuss the implications that this has for dark frame image correction. Close

• 15. [Article] Correction of dark current in consumer cameras

  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 ...

  Citation × Citation Citation Abstract Copy Title: Correction of dark current in consumer cameras Author: Dunlap, Justin Charles, Bodegom, Erik, Widenhorn, Ralf Year: 2010 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 to characterize the dark current in such cameras and to show that the dark current, in part due to heat generated by the camera itself, can be corrected by using hot pixels on the imager. This method generates computed dark frames based on the dark current indicator value of the hottest pixels on the chip. We compare this method to standard methods of dark current correction. Title: Correction of dark current in consumer cameras Author: Dunlap, Justin Charles, Bodegom, Erik, Widenhorn, Ralf Year: 2010 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 to characterize the dark current in such cameras and to show that the dark current, in part due to heat generated by the camera itself, can be corrected by using hot pixels on the imager. This method generates computed dark frames based on the dark current indicator value of the hottest pixels on the chip. We compare this method to standard methods of dark current correction. Close

• 16. [Article] Characterization and correction of dark current in compact consumer cameras

  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 ...

  Citation × Citation Citation Abstract Copy Title: Characterization and correction of dark current in compact consumer cameras Author: Dunlap, Justin Charles, Bodegom, Erik, Widenhorn, Ralf Year: 2010 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 to heat generated by the camera itself, can be corrected for by using hot pixels on the imager. This method generates computed dark frames based on the dark current indicator value of the hottest pixels on the chip. We compare this method to standard methods of dark current correction. Title: Characterization and correction of dark current in compact consumer cameras Author: Dunlap, Justin Charles, Bodegom, Erik, Widenhorn, Ralf Year: 2010 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 to heat generated by the camera itself, can be corrected for by using hot pixels on the imager. This method generates computed dark frames based on the dark current indicator value of the hottest pixels on the chip. We compare this method to standard methods of dark current correction. Close

• 17. [Article] Dark current in an active pixel complementary metal-oxide-semiconductor sensor

  We present an analysis of dark current from a complementary metal?oxide?semiconductor (CMOS) active pixels sensor with global shutter. The presence of two sources of dark current, one within the collection ...

  Citation × Citation Citation Abstract Copy Title: Dark current in an active pixel complementary metal-oxide-semiconductor sensor Author: Dunlap, Justin Charles, Porter, William Christian, Bodegom, Erik, Widenhorn, Ralf Year: 2011 We present an analysis of dark current from a complementary metal?oxide?semiconductor (CMOS) active pixels sensor with global shutter. The presence of two sources of dark current, one within the collection area of the pixel and another within the sense node, present complications to correction of the dark current. The two sources are shown to generate unique and characteristic dark current behavior with respect to varying exposure time, temperature, and/or frame rate. In particular, a pixel with storage time in the sense node will show a dark current dependence on frame rate and the appearance of being a ?stuck pixel? with values independent of exposure time. On the other hand, a pixel with an impurity located within the collection area will show no frame rate dependence, but rather a linear dependence on exposure time. A method of computing dark frames based on past dark current behavior of the sensor is presented and shown to intrinsically compensate for the two different and unique sources. In addition, dark frames requiring subtraction of negative values, arising from the option to modify the bias offset, are shown to be appropriate and possible using the computational method. Title: Dark current in an active pixel complementary metal-oxide-semiconductor sensor Author: Dunlap, Justin Charles, Porter, William Christian, Bodegom, Erik, Widenhorn, Ralf Year: 2011 We present an analysis of dark current from a complementary metal?oxide?semiconductor (CMOS) active pixels sensor with global shutter. The presence of two sources of dark current, one within the collection area of the pixel and another within the sense node, present complications to correction of the dark current. The two sources are shown to generate unique and characteristic dark current behavior with respect to varying exposure time, temperature, and/or frame rate. In particular, a pixel with storage time in the sense node will show a dark current dependence on frame rate and the appearance of being a ?stuck pixel? with values independent of exposure time. On the other hand, a pixel with an impurity located within the collection area will show no frame rate dependence, but rather a linear dependence on exposure time. A method of computing dark frames based on past dark current behavior of the sensor is presented and shown to intrinsically compensate for the two different and unique sources. In addition, dark frames requiring subtraction of negative values, arising from the option to modify the bias offset, are shown to be appropriate and possible using the computational method. Close