Video Picture
Each
line represents one
sweep
of
an
electron beam
which
is
"painting"
the
picture
as
it
goes
along.
The video beam produces
each
line
by
sweeping
from
left
to
right.
It
produces the
full
screen
by
sweeping the beam
from
the
top
to
the
bottom,
one line
at
a time.
Figure
3-1:
How
the Video Display Picture Is Produced
The video beam produces about
262
video lines from top to bottom, of which
200
nor-
mally are visible on the screen. Each complete set of
262
lines
is
called a display
field.
A complete display
field
is produced
in
approximately 1/60th of a second; this is known
as the
field
time. Between display
fields,
the video beam traverses the lines
that
are not
visible on the screen and returns to the top of the screen
to
produce another display
field.
The display area is defined as a grid of pixels. A pixel is a single picture element, the
smallest addressable
part
of a screen display. The drawings below show what a pixel is
and
how
pixels form displays.
Playfield Hardware
29
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