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with CCD die temperature, a noticeable increase in CCD dark current can occur at very high
binning factors.
5.4.
Region of Interest
Arbitrary, on-chip vertical Region of Interest (ROI) is fully supported on the DVC-4000D
cameras. When ROI is enabled, the regions above and below the region of interest are “dumped”
as fast as the CCD allows. The region of interest itself is read out normally. Dumping unwanted
lines outside the ROI can significantly increase the readout rate of the camera. DVCView
software provides interactive, graphical ROI selection, and the DVC camera API provides
developers with full ROI control. On-chip horizontal ROI is not available. Simultaneous binning
and ROI is fully supported.
As in binning, the CCD vertical registers are driven faster when the region of interest is reduced.
Dark current can increase during operation with small regions of interest.
6.
CCD phenomena
The Kodak KAI-04022 CCD is a high-performance image sensor with very good characteristics over a
wide operating range. To be as versatile as possible, the DVC-4000D camera exploits as much of the
CCD capability as possible and provides the user a great degree of control over the CCD functions. As a
result, it is possible to observe some interesting, low-level CCD phenomena under certain extreme
conditions.
6.1.
Blooming
Blooming is the result of charge spillover in the vertical transfer regions when the signal greatly
exceeds saturation. The DVC-4000D provides anti-blooming control, which suppresses
blooming under most imaging conditions. If signal levels are extreme and such high signal levels
cover a large percentage of the field of view, blooming may occur. The result is jagged, vertical
bright streaks running below such regions. In general, anti-blooming performance decreases with
increasing binning ratios.
6.2.
Smear
Smear is inherent to interline CCD sensors such as the KAI-04022. It is the result of transferring
image charge out of the pixels and into the adjacent vertical charge-transfer registers while
photons strike the CCD. Though the vertical charge-transfer registers are covered with a light
shield, unwanted signal can be introduced into them either by small amounts of light leaking
under the light shield or by signal electrons diffusing into the transfer region from the adjacent
pixels.
Smear is typically noticed during very short exposure times, when an extremely high light
intensity is incident on the CCD. The result is regions of elevated signal level extending above
and below very bright regions. Kodak interline CCDs exhibit very low smear levels, and smear
should not be noticeable under normal operating conditions.