A: In a CRT monitor, a gun shoots electrons and general light by colliding polarized
electrons on fluorescent glass. Therefore, CRT monitors basically operate with an
analog RGB signal. A TFT LCD monitor is a device that displays an input image by
operating a liquid crystal panel. The TFT has a fundamentally different structure than
a CRT: Each cell has an active matrix structure and independent active elements. A
TFT LCD has two glass panels and the space between them is filled with liquid
crystal. When each cell is connected with electrodes and impressed with voltage, the
molecular structure of the liquid crystal is altered and controls the amount of inlet
lighting to display images. A TFT LCD has several advantages over a CRT, since it
can be very thin and no flickering occurs because it does not use the scanning
method.
Q: Why is vertical frequency of 60Hz optimal for an LCD monitor?
A: Unlike a CDT monitor, the TFT LCD panel has a fixed resolution. For example, an
XGA monitor has 1024x3 (R, G, B) x 768 pixels and a higher resolution may not be
available without additional software processing. The panel is designed to optimize
the display for a 65MHz dot clock, one of the standards for XGA displays. Since the
vertical/horizontal frequency for this dot clock is 60Hz/48kHz, the optimum frequency
for this monitor is 60Hz.
Q: What kind of wide-angle technology is available? How does it work?
A: The TFT LCD panel is an element that controls/displays the inlet of a backlight
using the dual-refraction of a liquid crystal. Using the property that the projection of
inlet light refracts toward the major axis of the liquid element, it controls the direction
of inlet light and displays it. Since the refraction ratio of inlet light on liquid crystal
varies with the inlet angle of the light, the viewing angle of a TFT is much narrower
than that of a CDT. Usually, the viewing angle refers to the point where the contrast
ration is 10. Many ways to widen the viewing angle are currently being developed and
the most common approach is to use a wide viewing angle film, which widens the
viewing angle by varying the refraction ratio. IPS (In Plane Switching) or MVA (Multi
Vertical Aligned) is also used to give a wider viewing angle.
Q: Why is there no flicker on an LCD Monitor?
A: Technically speaking, LCDs do flicker, but the cause of the phenomenon is
different from that of a CRT monitor -- and it has no impact of the ease of viewing.
Flickering in an LCD monitor relates to usually undetectable luminance caused by the
difference between positive and negative voltage. On the other hand, CRT flickering
that can irritate the human eye occurs when the on/off action of the fluorescent object
becomes visible. Since the reaction speed of liquid crystal in an LCD panel is much
slower, this troublesome form of flickering is not present in an LCD display.
Q: Why is an LCD monitor virtually free of Electro Magnetic Interference?
A: Unlike a CRT, an LCD monitor does not have key parts that generate Electro
Magnetic Interference, especially magnetic fields. Also, since an LCD display utilizes
relatively low power, its power supply is extremely quiet.
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