Q: What are the advantages of TFT LCD compared with CRT?
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 CRT 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 low of Electro Magnetic Interference?
file:///F|/manual spec/813/philips TV&lcd/cd/Q70G9002813 8A 191EW9/lcd/manual/ENGLISH/191EW9/safety/saf_faq.htm（第 5／6 页）2008-9-2 13:15:34
