Dark count or Dark Current is one of the most important CCD specifications, :: Computer Science

grungy count or sin watercourse is angiotensin converting enzyme of the most important CCD specifications, along with resolution, quantum power and preventative figure.Dark count or Dark Current is one of the most important CCDspecifications, along with resolution, quantum efficiency and noisefigure. Dark circulating(prenominal) causes an output to occur without the previousintroduction of an input. This is caused by the thermal genesis andthen diffusion of charge. This Dark Current is generated at differentlocations in the CCD, but the cause of this charge generation isbasic on the wholey the equal in all locations. This is because all cases argon todo with irregularities in the fundamental watch glass structure of the silicon present in CCDs. Examples of these irregularities includemetal impurities much(prenominal) as gold, copper or iron, and crystal defectssuch as dislocations and stacking faults, all of which are realisen to bethermal generation sites of charge carrier s in silicon. THE BESTEXAMPLE OF WHERE THIS DARK Current can be situated is at the SiliconOxide to silicon interface of the MOS capacitor (which is the main grammatical construction block of a CCD) . This is referable to the fact that this is wherethe largest irregularity in the silicon crystal structure occurs.However, it can also be located in the in the bulk of the silicon bothinside and outside the depletion layer, which is define by the CCDpotential wells.To give an example of the amount of Dark Current, which is bring forth AKodak KAF-0400 and KAF-1600 sensor is specified to have a Dark Currentof 50 electrons being induced per second at 25 degrees c. pickings aone-minute exposure at this temperature would generate 3000 electronsof thermally induced charge, which is calculated by 60secs times 50electrons.In theory the average Dark Current value can be subtracted from theoutput value to countenance the signal due to photoelectrons. However inreality there are fluctuations in the Dark Current called Dark noise,and this cannot be accounted for in the same way. Noise occurs indifferent forms such as shot noise and trapping noise which bothappear in the CCD channel. It also occurs at the input and outputstages as KTC noise, but my main focus shall be on shot noise as it isclosely associated with Dark Current.We know that the generation of Dark Current is a totally randomprocess, due to the fact that the generation sites are randomlydistributed and perhaps more importantly, the Dark Current generationprocess is random as a lean of time. The number of electronsgenerated and then collected in a charge portion travelling through the