ASX340AT Datasheet, PDF (44/75 Pages) ON Semiconductor – Color CMOS NTSC/PAL Digital Image

ASX340CS: 1/4-Inch Color CMOS NTSC/PAL Digital Image Sensor
Overlay Adjustment
Overlay Adjustment
To ensure a correct position of the overlay to compensate for assembly deviation, the
overlay can be adjusted with assistance from the overlay statistics engine:
• The overlay statistics engine supports a windowed 8-bin luma histogram, either row-
wise (vertical) or column-wise (horizontal).
• The calibration statistics can be used to perform an automatic successive-approxima-
tion search of a cross-hair target within the scene.
• On the first frame, the firmware performs a coarse horizontal search, followed by a
coarse vertical search in the second frame.
• In subsequent frames, the firmware reduces the region-of-interest of the search to the
histogram bins containing the greatest accumulator values, thereby refining the
search.
• The resultant row and column location of the cross-hair target can be used to assign a
calibration value to offset selected overlay graphic image positions within the output
image.
• The calibration statistics patch also supports a manual mode, which allows the host
to access the raw accumulator values directly.
ASX340AT/D Rev. H, 8/15 EN
44
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