Leave it to Apple to encase the latest technology in a wrapper so irresistible that it appeals both to cutting-edge technophiles and to people who care more about how something looks than how it works. The most noticeable change in the new generation of the iMac isn’t under the hood but stuck on the top of the diminutive computer, looking like the Space Shuttle’s robotic arm holding a big solar panel. In place of the old iMac’s bulky tube monitor hangs an ultra-thin liquid-crystal display (LCD) — a crystal-clear indication of the changing face of display technology.

Apple marketing executives were quick to call the introduction “the beginning of the end” for the cathode-ray tube (CRT), and that’s more than mere hype. A report by the market-research firm Display Search at the end of 2001 showed a record increase in sales of LCD computer monitors, accompanied by a significant decline in sales of CRT monitors. While LCD monitors are still more expensive than their tube counterparts, especially in larger screen sizes, that gap is narrowing all the time. Increasingly, shoppers are willing to pay the extra money for thin, high-tech screens that don’t waste precious desk space.

Whether the same logic applies to living-room space remains to be seen, but TV manufacturers aren’t taking any chances. The new crop of LCD-based TVs and monitors — including rear-projection TVs (RPTVs), front-projection systems, and wafer-thin direct-view sets — is more varied and affordable than ever. And all of them are built around the same general technology that powers the display on your pocket calculator.


LCD TV Shopping Guide
Inside a Liquid Crystal Display

How LCD Works
RCA created the first experimental LCD in 1968, and in 1973 Sharp was the first company to sell a calculator with a liquid-crystal screen. An LCD contains rod-shaped molecules, initially all pointed the same way, that can change their orientation in response to small amounts of electricity.

There are basically two types of LCDs: reflective and transmissive. A simple reflective display consists of a layer of liquid crystals sandwiched between two transparent electrode layers, with the whole array contained between two pieces of polarized glass plus a mirrored back that reflects ambient light. When current runs through the electrodes, the liquid-crystal molecules change orientation (“untwist”) and become dark, blocking light from passing through and producing, say, one of the hexagonal bars that make up digits on a calculator. Instead of having a mirrored back, transmissive flat-panel LCDs — including both TVs and computer monitors — contain a fluorescent backlight that shines through the panel so you can see the image onscreen even in the dark.

Early laptop-computer screens and portable TVs used a passive-matrix LCD design, but today most LCDs are active-matrix. Both types contain thousands or millions of tiny pixels, or picture elements, that together form an image. In a color LCD, each pixel actually consists of three subpixels — one each for red, green, and blue — that combine to create the spectrum of visible color.

In a passive LCD, the electrical charges travel down rows and columns of the display until they intersect at the designated subpixel and untwist it to the desired degree. But the current can also excite neighboring subpixels as it travels along the row or column, decreasing contrast and fuzzing the images.

To preserve contrast and sharpness as much as possible, active-matrix LCDs use tiny switches called thin-film transistors (TFTs) that allow the control circuit to address each subpixel individually without affecting the others, untwisting it in tiny degrees to produce the slight gradations in intensity necessary to create a realistic image. Typical active LCDs are capable of showing 16.8 million colors, created by 256 gradations in each of the three primary colors.

A typical 1,024 x 768-pixel LCD panel (found in direct-view TV sets and computer monitors) or chip (found inside front projectors and RPTVs) has around 2.3 million individual TFTs, representing quite a manufacturing feat. A problem with any one of these TFTs causes a “bad pixel,” which can show up as a spot whose intensity doesn’t change or changes differently from the rest of the display. Even modern LCDs have bad pixels, but advances in manufacturing and quality control have made them rare.

LCD in the Living Room
For home entertainment, LCDs have been most popular in front-projection installations, since they are less expensive than CRT projectors and far easier to set up. An LCD front projector contains a lamp that shines through the small LCD chip and then the lens, which throws an enlarged image onto the screen. Better versions contain three separate chips devoted to red, green, and blue (like the three tubes in a CRT projector), doing away with the subpixel arrangement.

The LCD projectors found in corporate boardrooms and video art galleries aren’t really the best choice for people building big-screen home theater systems. They’re designed to be attached to computers and provide a bright PowerPoint-friendly picture even under fluorescent lighting. In a home environment, their picture quality suffers considerably compared with CRT projectors.

The big problem with LCD monitors is low contrast — the range (expressed as a ratio) between the brightest white and darkest black the display can produce. Since some light always makes it through the LCD panel to the screen, black areas of the picture appear dark gray instead of black. While a contrast ratio of 800:1 is common among the best CRT projectors, even the best LCD projectors can’t achieve half as much. Another problem sometimes found is the “screen door effect,” where the spaces between pixels in the panel appear as a faint grid overlaying the image. Many LCD projectors also lack the processing power to cleanly convert (“scale”) the resolution of the incoming video to match the pixel count of the LCD chip or to realize fine gradations in color.

Projectors designed specifically for home theater overcome many of these limitations. In addition to standard A/V connections (often at the expense of computer connections like a VGA input) and better internal processors, they generally have reduced brightness and higher contrast to achieve better blacks. Many also employ 16:9-shaped panels to correspond to wide projection screens and widescreen DVDs and HDTV programs. While these advances are significant, video experts agree that both CRT and DLP (Digital Light Processing) projectors still beat LCD in the picture-quality race. In most cases, though, LCD projectors are cheaper.

LCD technology can also be built into rear-projection TVs. While still uncommon compared with CRT-based RPTVs, large-screen LCD models from Sony and Panasonic are beginning to appear in A/V showrooms. Their biggest advantage is their shallow cabinets. Sony’s 60-inch KF-60DX100 HDTV monitor ($8,000), for instance, is a hair over 15 inches deep, or about 10 inches less than the slimmest comparable-size CRT rear projector. Like LCD front projectors, LCD RPTVs suffer from relatively low contrast, and they’re still expensive. On the plus side, they don’t require periodic tube convergence to maintain a sharp picture.

Perhaps the most exciting application of LCD is for ultra-thin direct-view TVs. These super-slim sets can be picked up and carried from room to room or hung in places where a normal set won’t fit. Some direct-view LCD screens, like those on battery-powered Watchmen, portable DVD players, or the backs of airplane headrests, have narrow viewing angles — the image gets quite a bit darker and the colors less accurate as you move to either side of dead center. This isn’t a problem for computer monitors and personal TVs, but a living-room TV requires a wide viewing angle so everyone in the room can enjoy a good picture. Advances in the way the liquid crystals are oriented allow better LCD sets and monitors to boast viewing angles up to 170°, which is comparable to a direct-view CRT set. New LCD TVs also have improved contrast (though still not as good as CRTs) and use significantly less power.

More manufacturers than ever before offer thin LCD TVs. Panasonic makes combi-models that fit a thin, widescreen LCD TV and a DVD player into one chassis, while Sharp and Samsung both offer standalone models. Sharp’s Aquos line, with built-in analog TV tuners and speakers, ranges in size from a 13-inch standard-screen model ($1,200) to a 30-inch widescreen HDTV monitor ($8,000). Compare that with the street price of 15-inch LCD computer monitors, now down around $400.

The significant disparity in prices is because there’s tougher competition in the computer market, LCD TVs have to meet more stringent picture-quality standards than computer monitors, and far fewer LCD TVs are made in the first place, which means economies of scale haven’t kicked in yet. But that could soon change. The total dollar value of LCD TVs sold in Japan exceeded that of CRT TVs for the first time in 2001. Despite opening a new production facility in Japan that tripled its production capacity, Sharp says it still can’t keep up with the demand. While the eager acceptance of LCD TVs by Japanese consumers can be attributed mainly to the small size of living quarters there, industry observers are optimistic that Americans, too, will come to favor the slim sets over the next few years.

Currently there isn’t much competition between LCD and plasma, the other major flat-panel display technology. In fact, many manufacturers offer both. Plasma TVs are generally 42 inches (diagonal) or larger, while LCD screens are closer in size to standard direct-view sets and top out at 30 inches (diagonal). Although Samsung has shown an experimental 40-inch LCD direct-view TV, the high cost of manufacturing such large panels leaves plasma unlikely to be challenged any time soon at the large-screen end of the thin-panel spectrum. (For more on plasma displays, see “Everybody Loves Plasma,” April.)

Most TV manufacturers don’t want to see the prices of LCD sets fall as quickly as their counterparts did in the computer world, but they might not have a choice. The appeal of a thin TV you can hang on the wall of your home — or mobile home — is pretty universal. It’s just a matter of time before slim TVs will be the norm at every size.