as blurring or smearing of a sharp brightness transition.
It may or may not be
accompanied by an overshoot or ringing to the right or left of the transition.
Measurement of the SD may be accomplished by observing the leading and trailing
edge of the window signal displayed at the horizontal rate; the display may be
expanded on the scope time base.
b. Line-time Waveform Distortion (LD) concerns a longer time constant than does
SD, and it results in impairment of brightness reproduction between the sides of a
picture detail. When detail is smaller than full picture height, the streaking is
most noticeable to the right of the detail. Details extending all the way up and
down the picture may result in streaking across the full raster horizontally.
Measurement of LD is done across the top of the window signal viewed at a
horizontal rate, and by the relationship of the leading and trailing edges to
reference black.
(1) In one type of LD, (fig 3-20) positive streaking is indicated preceding
the window (black-after-black) and following the window (white-afterwhite) on the
raster.
Note the blacker-than-black tilt prior to the window, and the time
duration required to fall to black at the trailing edge of the window. In actual
measurement, the 1 microsecond intervals at the leading and trailing edges are not
used, and the same durations for a and b relative to A are used.
The window is
approximately 1/2H in duration, and the time from the trailing edge of the window
to the leading edge of sync is about 1/4H.
So one-half of the window tilt is
included in the (a) measurement, as indicated on the drawing.
Figure 3-20.
LD with leading and trailing positive streaking
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