Video Hardware, Part 1 - Curved Versus Flat Picture Tubes
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Phosphor-based screens come in two styles: curved and flat. Until recently, the typical display screen has been curved; it bulges outward from the middle of the screen. This design is consistent with the vast majority of CRT designs (the same as the tube in most television sets). Although this type of CRT is inexpensive to produce, the curved surface can cause distortion and glare, especially when used in a brightly lit room. Some vendors use antiglare treatments to reduce the reflectivity of the typical curved CRT surface.
The traditional screen is curved both vertically and horizontally. Some monitor models use the Sony Trinitron CRT, some versions of which are curved only horizontally and flat vertically; these are referred to as flat square tube (FST) designs.
Most manufacturers are now selling monitors featuring CRTs that are flat both horizontally and vertically. Sony's FD Trinitron, NEC-Mitsubishi's DiamondTron NF, and ViewSonic's PerfectFlat are some of the more popular flat CRT designs, the first such screens for PCs since the short-lived Zenith FTM monitors of the late 1980s. Many people prefer this type of flatter screen because these picture tubes show less glare and provide a higher-quality, more accurate image. Although flat-screen CRTs are slightly more expensive than conventional curved CRTs, they are only one-third to one-half the price of comparably sized flat-panel LCDs.
Figure 15.2 compares the cross-section of typical curved and flat CRT picture tubes.
Figure 15.2 A typical curved-tube CRT (left) compared to a Sony Trinitron FD flat tube (right).
DVI—Digital Signals for CRT Monitors The latest trend in CRT monitor design is the use of digital input signals using the same Digital Video Interface (DVI) standard used for LCD flat-panel displays. Although several major monitor vendors announced support for DVI-I interfaces for their CRT monitors in 1999, most CRT monitors (except for a few 19'' or larger high-end monitors) continue to use the conventional 15-pin analog VGA connector. CRT monitors that use the DVI-I connector—unlike the TTL digital displays of the 1980s that supported only a few colors—support the same unlimited color spectrum as analog CRTs. Users benefit from digital displays because these displays can feature better picture quality, better signal reception, and precise auto setup.
Because most low-end and mid-range video cards still feature only analog (DB-15) VGA connectors, many of these monitors feature both analog and 20-pin DVI interfaces. However, as all-digital LCD panels that also use the DVI interface increase in popularity and DVI interfaces on video cards continue to increase in popularity, analog VGA eventually might be replaced by DVI-based CRT and LCD panels.
 | This chapter is from Upgrading and Repairing PCs, 16th edition,by Scott Mueller. (Que Books, 2004, ISBN: 0789731738). Check it out at your favorite bookstore today. Buy this book now! |
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