Sensors and Actuators - Fachbereich Physik der Universität ...

shifted by one location. After a delay equal to the number of capacitors multiplied by the
shift interval, the charge corresponding to the input signal arrives at the last capacitor in the
array, where it is amplified to become the output signal. This process continues indefinitely,
creating a signal at the output that is a delayed version of the input, with some distortion
due to sampling. A CCD used in this way is also known as a bucket-brigade delay line. This
application of CCDs has now been mostly superseded by digital delay lines.
CCDs with several rows of pixels shift the charge down in the fashion of a vertical shift
register and only the last row is read out in a horizontal shift register. The speed of the
measuring circuit must be enough to count out the entire bottom row, then shift the rows
down and repeat for every other row, until it has read the entire frame. In video cameras this
entire process takes place about 40 times a second.
Several factors can affect whether a photon releases an electron: circuits on the CCD
surface can block light from entering; longer wavelengths can penetrate certain depths of
the CCD without interaction with the atoms; some shorter wavelengths may reflect off the
surface, and so on.
Knowing how many of the photons which fall on the photoreactive surface will release an
electron is an accurate measurement of the CCD's sensitivity. This figure is called "quantum
efficiency" and is given as a percentage.
Quelle: http://en.wikipedia.org/wiki/CCD, http://videoequipment.globalspec.com/LearnMore/Sensors_Transducers_Detectors/Vision_Sensing/CCD_Image_Sensors
CCDs bestehen aus einer Matrix von Fotodioden. Die Fotodioden wandeln Lichtenergie in
Form von Photonen in elektrische Ladungen um. Die Elektronen, die durch Interaktion von
Licht mit Siliziumatomen entstehen, werden in einem Ladungspool in Form eines
Kondensators gesammelt. Später wird jedes so erzeugte Ladungspaket mit Hilfe von
Schieberegistern über den Chip zum Ausgang und zu einem Verstärker transportiert.
Folgende Skizze zeigt verschiedene Komponenten, die zu einer CCD gehören.
At the heart of all charge-coupled devices (CCDs) is a light-sensitive metal oxide
semiconductor (MOS) capacitor, which has three components consisting of a metal
electrode (or gate), an insulating film of silicon dioxide, and a silicon substrate.
Quelle: http://www.microscopy.fsu.edu/primer/digitalimaging/concepts/moscapacitor.html
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