●
G3 cameras with Kodak KAI Interline Transfer (IT) architecture
(G4 cameras are not produced with IT detectors). 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 G3 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.
8
Illustration 2: “Interline Transfer” CCD schematic diagram
