Philips 190X6 - Manual (Page 49)

FAQs (Frequently Asked Questions)
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 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.
file:///D|/My%20Documents/dfu/X6_model/english/190x6/safety/saf_faq.htm (8 of 9)2005-06-27 1:29:18 PM