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G3 cameras with OnSemi KAI Interline Transfer (IT)
architecture.
There is a shielded column of pixels just beside each
column of active pixels on these detectors. The shielded columns are
called Vertical registers. One pulse moves charge from exposed pixels
to shielded pixels on the end of each exposure. The the charge is
moved from vertical registers to horizontal register and digitized in
the same way like in the case of Full Frame detectors. This mechanism
is also known as “electronic shuttering”, because it allows very short
exposures and also digitization of the image without mechanically
shielding of the detector from incoming light.
Also cameras with IT CCDs are equipped with mechanical shutter,
because electronic shutter does not allow dark-frame exposures,
necessary for proper image calibration etc.
The price for electronic shutter if lower quantum efficiency
(sensitivity) of IT detectors compared to FF ones. Also all IT detectors
are equipped with ABG, so they can acquire images of very bright
objects without charge blooming to neighboring pixels.
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Illustration 3: “Interline Transfer” CCD schematic diagram
