cathode ray tube
<hardware> (CRT) An electrical device for displaying images by exciting
phosphor dots with a scanned electron beam. CRTs are found in computer VDUs and
monitors, televisions and oscilloscopes. The first commercially practical CRT
was perfected on 29 January 1901 by Allen B DuMont.
A large glass envelope containing a negative electrode (the cathode) emits
electrons (formerly called "cathode rays") when heated, as in a vacuum tube. The
electrons are accelerated across a large voltage gradient toward the flat
surface of the tube (the screen) which is covered with phosphor. When an
electron strikes the phosphor, light is emitted. The electron beam is deflected
by electromagnetic coils around the outside of the tube so that it scans across
the screen, usually in horizontal stripes. This scan pattern is known as a
raster. By controlling the current in the beam, the brightness at any particular
point (roughly a "pixel") can be varied.
Different phosphors have different "persistence" - the length of time for which
they glow after being struck by electrons. If the scanning is done fast enough,
the eye sees a steady image, due to both the persistence of the phospor and of
the eye itself. CRTs also differ in their dot pitch, which determines their
spatial resolution, and in whether they use interlace or not.
Category 3 « Category 5 « CA-Telon « cathode ray
» CATIA » cationic cocktail » C/ATLAS