IMAGE SENSOR SOLUTIONS
8
Electronic Shutter
The KAI-1010 provides a structure for the prevention of
blooming which may be used to realize a variable
exposure time as well as performing the anti-blooming
function. The anti-blooming function limits the charge
capacity of the photodiode by draining excess electrons
vertically into the substrate (hence the name Vertical
Overflow Drain or VOD) . This function is controlled by
applying a large potential to the device substrate (device
terminal SUB). If a sufficiently large voltage pulse (VES
≈
40V) is applied to the substrate, all photodiodes will be
emptied of charge through the substrate, beginning the
integration period. After returning the substrate voltage to
the nominal value, charge can accumulate in the diodes
and the charge packet is subsequently readout onto the
VCCD at the next occurrence of the high level on
φV1.
The integration time is then the time between the falling
edges of the substrate shutter pulse and
φV1. This scheme
allows electronic variation of the exposure time by a
variation in the clock timing while maintaining a standard
video frame rate.
Application of the large shutter pulse must be avoided
during the horizontal register readout or an image artifact
will appear due to feedthrough. The shutter pulse VES
must be “hidden” in the horizontal retrace interval. The
integration time is changed by skipping the shutter pulse
from one horizontal retrace interval to another.
The smear specification is not met under electronic shutter
operation. Under constant light intensity and spot size, if
the electronic exposure time is decreased, the smear signal
will remain the same while the image signal will decrease
linearly with exposure. Smear is quoted as a percentage of
the image signal and so the percent smear will increase by
the same factor that the integration time has decreased.
This effect is basic to interline devices.
Color Filter Array (optional, for KAI-
1011CM only)
OUTPUT
G
B
R
G
G
G
G
G
G
G
R
R
B
B
B
2 BLACK LINES
R
Figure 5 CFA Pattern
KAI-1010/1011 Rev 8 •
www.k odak.com/go/imagers 585-722- 4385 imagers@kodak.com
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