Data Translation DT3152-LS, User Manual

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Principles of Operation
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The clamping circuit selectively holds the blanking level portion of
the video signal. Refer to
page 35 for more information on clamping
as it relates to the active video area.
Chrominance Notch Filter
While it is possible to acquire monochrome images from color
signals, the color content of these signals can cause interference
patterns that degrade the image. The DT3152-LS frame grabber board
provides a chrominance notch filter that removes color information
for cleaner acquisition and more accurate analysis.
For area-scan operations only, if you are using an AC-coupled video
signal that has chrominance information on it, as is the case with the
NTSC and PAL video formats, you can use software to apply the
chrominance notch filter. The chrominance notch filter for 60 Hz is set
to 3.58 MHz, while the chrominance filter for 50 Hz is set to
4.43 MHz. By default, no filter is selected.
For line-scan operations, you can select either AC no filter or DC no
filter.
Black and White Levels
Black level is defined by DT-Open Layers as the voltage below which
all other voltages are digitized to black. White level is defined as the
voltage above which all other voltages are digitized to white. For ease
of use, both of these voltages are measured at the camera's output.
On the DT3152-LS frame grabber board, if you are using a gain of 1,
use software to set a black level and a white level. If, however, you
need to use a gain other than 1, use software to set an offset, gain, and
reference value.