Silicon Graphics Presenter, Руководство пользователя

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Appendix A: Liquid Crystal Display (LCD) Technology
an overhead projector. When the door is removed, a switch opens that
disables the CCF tubes and reverses the data stream to the display, causing
the image to be flipped right to left. The display can therefore be placed face
down, 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 subpixel 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 subpixel 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’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’s pixels are formed by a combination of light
valve and color filter that produces an extremely crisp edge for each
subpixel. You can actually see these red, green and blue subpixels when
using the Presenter 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. 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’s flat panel. CRTs
flicker because the electron beam can only be in 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’s flat panel, all pixels are being