in the generation of symbology, for sweep retrace, and
so forth.
We take you through a detailed look at how the
vector scan CRT uses these signals to paint the
display on the CRT later in this chapter.
COLOR CRT’S
Thus far our discussion has been about
monochrome CRTs. Color CRTs offer a variety of
colors and are used extensively with personal
computers, simulators, and other training devices.
Most color CRTs use a raster-scan type deflection.
The major differences between color and
monochrome CRTs are in the phosphor coating of the
CRT, the electron gun(s), and the high voltage
requirements.
The phosphor coating of a color CRT is made up
of small dots that contain a dye so they radiate one of
the three primary colors of light (red, green, or blue).
These dots are arranged in groups called triads.
Figure 1-6 illustrates a typical grouping of triads.
The size of the phosphor dots is often used as a
measure of the CRT’s resolution. Newer monitors
have CRTs with dots of .20 mm and smaller. The
dots are the smallest addressable element of a picture.
These picture elements are called pixels or pels,
depending on the manufacturer. Both terms have the
same meaning.
Three electron beams are required to properly
strike the different colored phosphor dots. Some
color CRTs use three electron guns, known as a delta
gun CRT. The beams pass through a shadow mask
that is designed so that only the red gun strikes the red
dots, the blue gun strikes the blue dots, and the green
gun strikes the green dots.
Newer color CRTs have combined all three
electron beams into a single gun, as shown in figure
1-6. The single-gun CRT does not need convergence
alignments and greatly reduces the amount of circuitry
required in a color monitor. This design is common
in almost all of the newer color monitors.
Figure 1-6.—A typical color CRT.
1-6
