Computer display, Monitor
A computer display monitor, usually called simply a monitor,
is a piece of electrical equipment which displays viewable images
generated by a computer without producing a permanent record. The word
"monitor" is used in other contexts; in particular in television
broadcasting, where a television picture is displayed to a high
standard. A computer display device is usually either a cathode ray
tube or some form of flat panel such as a TFT LCD. The monitor
comprises the display device, circuitry to generate a picture from
electronic signals sent by the computer, and an enclosure or case.
Within the computer, either as an integral part or a plugged-in
interface, there is circuitry to convert internal data to a format
compatible with a monitor.
Screen Size
Diagonal size
The
inch size quoted is the diagonal size of the picture tube or LCD panel.
With CRTs the picture is normally smaller by 1.5" - 2", hence a 17" LCD
gives about the same size picture as a 19" CRT.
This
method of size measurement dates from the early days of CRT television
when round picture tubes were in common use, which only had one
dimension that described display size. When rectangular tubes were
used, the diagonal measurement of these was equivalent to the round
tube's diameter, hence this was used (and of course it was the largest
of the available numbers)
Widescreen area
A
widescreen display always has less screen area for a given quoted inch
size than a standard 4:3 display, due to basic geometry. Some regard
the resulting greater potential profit margin as a prime reason for
their promotion.Imaging technologies
As with television, several different hardware technologies exist for displaying computer-generated output:
* Liquid crystal display (LCD). TFT LCDs are the most popular display device for new computers in the Western world.
o Passive LCD gives poor contrast and slow response, and other image defects. These were used in some laptops until the mid 1990s.
*
o TFT Thin Film Transistor LCDs give much better picture quality in several respects. All modern LCD monitors are TFT.
* Cathode ray tube (CRT)
o Standard raster scan computer monitors
o Vector
displays, as used on the Vectrex, many scientific and radar
applications, and several early arcade machines (notably Asteroids -
always implemented using CRT displays due to requirement for a
deflection system, though can be emulated on any raster-based display.
o Television
receivers were used by most early personal and home computers,
connecting composite video to the television set using a modulator.
Image quality was reduced by the additional steps of composite video ?
modulator ? TV tuner ? composite video.
* Plasma display
* Surface-conduction electron-emitter display (SED)
* Video
projector - implemented using LCD, CRT, or other technologies. Recent
consumer-level video projectors are almost exclusively LCD based.
* Organic light-emitting diode (OLED) display
* Penetron military aircraft displays
