Monitor Technologies
The monitors in most desktop computers today are the same cathode ray tubes (CRTs) that had their first use in televisions. CRTs, which use a set of three electron guns that scan back and forth to illuminate color phosphors on the front of the screen, provide a good image, but they are heavy, bulky, and use lots of power. The big advantage of CRTs is price; several generations of manufacturing improvements have created monitors of consistently high quality at very advanced levels of production efficiency. The fact that televisions use essentially the same technology is an important contributor to this success. But CRTs have lots of weaknesses, and competition is coming, beginning with portable machines.
Laptop and other small displays already use one or another kind of what is called flat panel technology. Even for desktops, the movement of the market is now away from CRTs and toward flat panels. Flat panels can match or exceed CRTs in most aspects of quality, and always beat them in power consumption. The problem is that production is two or three times as expensive. There are quite a few contending flat panel technologies, three or four of which look very promising. If any reach their potential, the CRT will quickly disappear. The leaders in the flat panel race are described in Table 3.2 below.
If you were handicapping the flat panel race at the beginning of 2000, it's likely you would bet on active matrix moving up fast to dominate CRTs in the desktop race, plasma screens taking the lead in the emerging category of wall-hanging displays, and micromirrors as the choice for any large image that will allow projection. The organic LED, which in its early stages of development seems to offer the best of all possible worlds, is a dark horse in all these races.
Table 3.2. Flat Panel Display Technologies| Type | Characteristics | Strengths vs. other flat panel types | Weaknesses vs. other flat panel types |
|---|
| Active matrix liquid crystal display (AMLCD) | Each dot triad uses separately switched liquid crystals that can be open or closed; a backlight shines through an open crystal and then through an open red, green, or blue filter. Fabrication of the switching matrix is essentially the same as chip making. Standard for laptop computers. | High resolution | Limited angle of view. Cost increases dramatically with size since larger panels are more likely to have flaws. Backlight consumes a lot of power. Note that significant improvements in angle of view and power consumption are in the pipeline. |
| Passive matrix LCD | Pixels are switched indirectly rather than through transistors at each dot. Reflective displays don't use a blacklight but suffer from low contrast in dim lighting. | Inexpensive | Moderate resolution, narrow angle of view, blurry with fast motion. |
| Field effect display (FED) | Each element in a dot triad is like a tiny CRT. | Low weight and power consumption, rugged. | Medium resolution. Can't yet be manufactured at competitive cost to AMLCD. More likely to be used for TV size than monitors. |
| Plasma displays | Tiny pockets of gas illuminate colored phospors on a screen. | Bright with high contrast. | Moderate resolution, high power consumption. Manufacturing cost still high. |
| Micromirrors | Around 500,000 little mirrors on one silicon chip reflect or don't reflect according to a digital signal. | High resolution, scalable to very large sizes. | Projection only. High power consumption. System manufacturing costs need to come down to compete in TV market. |
| Organic light emitting diodes (OLED; also called polymer LEDs) | Organic polymers emit light directly (no backlight or filter is required). Variety of approaches in testing. | High resolution, low weight and power consumption. | Still in research stage, need reliable blue LED to get full color. Very promising. |
