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Before reading this howto, I highly recommend
looking at any of the CRT articles published by www.howstuffworks.com.
While this site contains all sorts of technical yummies,
their articles on TVs and PC monitors are particularly tasty.
arcade monitors, and PC monitors are all Cathode Ray Tubes
(CRT). The crude drawing above illustrates the basic operation
of a Cathode Ray Tube display. A "gun" located
at the back of a CRT shoots a set of electron beams towards
a phosphor coated screen. When the phosphors are struck
by electrons, they give off visible light. The gun that
shoots the electron beams is called an "electron gun,"
and it typically shoots three tightly grouped electron beams.
Each beam is dedicated to a type of phosphor that gives
off a different color of light when struck, red, green,
and blue (or RGB for short). These three primary colors
can be added together to create the full visible spectrum.
From the lit RGB triad below we can see that blue and green
come together to create cyan, and that red and green come
together to form yellow, and that red, green, and blue come
together to create white, the list goes on, and on. By varying
the number of electrons dedicated to each color phosphor,
the electron gun can create any visible color. Black is
the only exception which, of course, is created by the absence
of any light (i.e. electrons).
In the days of yore, monitor
phosphors were arranged much like they are above, in a triad
formation. Many monitors today, however, use a grill type
layout instead (pictured below).
use magnetic fields to steer / deflect the electron beams.
In the theoretical CRT model pictured above, what we are
basically looking at is a snap shot in time. The electron
gun located at the back of the tube is shooting a set of
electron beams past two deflecting magnetic fields. One
magnetic field controls the horizontal deflection, the other
controls the vertical deflection. By timing the potential
of these two fields, the electron beams can be directed
in a controllable path across the CRT's phosphor coated
Today's CRTs can manipulate the electron
beams at an amazing speed, at a speed usually measured in
micro seconds. However, when CRTs first emerged in the late
30's, in the form of a TV, the speed with which the electron
beams could be directed was comparatively slow. PC monitors
are now up to six times faster than the first TVs ever made.
Many of the first arcade games ever made
used vector CRTs, games like Asteroids. Vector CRTs direct
the electron beams as a series of programmable lines called
vectors. Unlike most CRTs, these lines don't have to follow
a raster pattern.
Vector CRTs not only produced very vivid,
bright graphic displays, but they also inspired the world's
first 3D games. Atari released several enormously popular
3D games in the early 80s, including Battlezone, Tempest,
and Star Wars, all of which used vector CRTs.
While vector CRTs produced bright colorful
games, they severely limited the complexity of drawable
images (images had to be drawn as a series of lines). Eventually,
they fell out of favor with game developers and by the mid
80's had all but disappeared from production lines. While
tremendously successful at one time, vector CRTs were ultimately
displaced by the more flexible raster CRT. Now-a-days, only
the grooviest arcade rooms feature vector game cabinets,
as they are quite rare.
So what are raster CRTs? Well, chances
are you are viewing this website on one. But even if you
aren't, I'm sure you've seen one before. Most TVs and all
Multisync PC monitors are raster CRTs.
While there are many variations
to a grill type layout, they all strive towards the same
goal, a display that contains more phosphor. Essentially,
a grill type layout includes much of the horizontal space
consumed by a traditional triad shadow mask. Pictured above
is a Sony Trinitron aperture grill layout. Notice how much
more phosphor it contains per square area over a traditional
triad shadow mask layout. While Sony pioneered the first
grill layouts, most CRT manufacturers now use them, albeit
a hybrid of some sort.
Pictured above is a Triad
Shadow Mask - Trinitron hybrid type layout. Wellsgardner's
D9200 uses a layout like the one above, as do most modern
arcade monitors and TVs.