Differences Between Lcd And Crt Technology - Silicon Graphics Presenter 1280 Owner's Manual

Appendix A: About Liquid Crystal Display (LCD) Technology
42
instead of back down, on the projector stage. This is important because it
places the color filter layer between the powerful projector beam and the
somewhat light-sensitive TFT plate.
In operation, the TFT devices activate sub-pixel elements in the display by
causing a voltage potential across selected portions of the liquid crystal
material. These elements are used as variable shutters to control the intensity
of white light coming from the CCF panel and reaching the red, green, or
blue filters. Combinations of these sub-pixel elements produce a full pixel
(RGB triad) of the proper hue, saturation, and brightness much like a
cathode ray tube (CRT).

Differences Between LCD and CRT Technology

If you are accustomed to using a CRT monitor, you will notice that the
Presenter 1280's flat panel display is remarkably different.
One of the most noticeable differences is the crispness of text. A CRT pixel is
formed by a beam of electrons that scans across the screen. Thus pixels
"bloom" at the fuzzy edge of the electron beam and smear into each other as
the beam moves. The Presenter 1280's pixels are formed by a combination of
light valve and color filter that produces an extremely crisp edge for each
sub-pixel. You can actually see these red, green and blue sub-pixels when
using Presenter 1280 in Overhead Projector mode if you stand very close to
the projector screen.
Another difference is the lack of distortion in the image displayed by the
Presenter 1280. There are two reasons a CRT cannot achieve this: the physics
of creating glass tubes makes it almost impossible to make them flat, and the
magnetics of controlling an electron beam makes it almost impossible to get
straight lines everywhere on the CRT.
A third difference is the lack of flicker on the Presenter 1280's flat panel. CRTs
flicker because the electron beam can be in only one place at a time. Thus
each pixel on a CRT is being driven only about a millionth of the time. The
phosphor has a "persistence" that causes it to emit light over a little longer
period, but it still flickers. In the Presenter 1280's flat panel, all pixels are
being driven all the time. Thus pixels that are not changing in value look
perfectly stable.