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Figure 5. Image with proper scan direction
Image scanned in direction where the TDI rows track opposite to the object motion
Figure 6. Image with incorrect scan direction
Some AOI systems require the scan direction to change at regular intervals, such as those scanning
a panel forwards, coming to a stop, and then scanning backward as the cameras field of view is
progressively indexed over the entire panel. Direction can be dynamically controlled by sending the
appropriate direction command to the camera or via the CLHS GPIO (General Purpose
Input/Output) control bits.
It is important to note that when the camera line rate comes to a stop and the direction is changed
the correct imaging will not be achieved for several scan lines. Therefore, it is necessary for the
system to over-scan the area being imaged, including the lines that are not valid as a result of the
direction change. This will ensure that valid data will be generated on the return path, as the
24 •
The Piranha XL XDR Camera
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