DLP TV Explained

A Handbook to DLP TV Technology by Jack Burden

Step 1: DLP TV (Digital Light Processing) Technology

Plasma TV's have long enjoyed singular billing as the "Big Thing" in consumer electronics, but a new display technology has begun to make some headlines of its own. Digital Light Processing (DLP TV) technology was developed by Larry Hornbeck at Texas Instruments (TI) in the 1970s, perfected in the '80s, and finally introduced to the public in 1996. Since then, DLP TV has started making waves in the fixed-pixel display market by meeting the surging demand for less expensive--though no less capable--large-screen TVs. Some analysts think DLP might wind-up being as ubiquitous as Dolby sound is in stereos.

After years of experimenting with fingernail-sized computer chips that hold a million or more microscopic mirrors, TI is finally seeing a payoff--and it may be in your living room before long. Some major players in the consumer electronics industry have gotten behind this new display technology. With its DLP chip now at the heart of new high-definition television sets from RCA, Samsung, LG, Toshiba, Zenith, and Panasonic (to name a few), TI shipped its 3 millionth DLP chip in April 2004. Which is quite a feat, given that, as recently as 2002, DLPs accounted for just 0.8% of new TV sales.

With so many manufacturers adopting this technology, DLP TVs are expected to account for a full 8.5% of total domestic TV sales by the end of 2004. Analysts think 2005 will be a breakout year for DLP, when it will finally surpass the 10% mark in its share of U.S. television market. If TI has its way, you'll be seeing the benefits of DLP technology first-hand the next time you buy a new TV. Consider how DLP has penetrated the product lines of companies like:

RCA/Thomson DLP TV, which utilizes DLP technology to power its Scenium line of HDTVs and is making headlines with its new Profiles series of under-seven-inch-deep HD DLP TVs;
Sharp DLP TV, which plans to have its line of DLP TVs on store shelves by early 2005;
Panasonic DLP TV, which introduced four new 50" and 60" DLPs with 10-bit image processing, built-in tuners, and photo-viewing capability at this year's Consumer Electronics Show in Las Vegas;
Samsung DLP TV, which will be the first manufacturer to offer the next-generation TI HD3 DLP chip in its 63 series of 46", 50", 56", and 61" DLP TVs.;
Toshiba DLP TV, which will start shipping its new line of DLPs in Fall 2004
LG DLP TV, which recently got into the DLP TV business with a 52" monitor of its own; and
Mitsubishi DLP TV, which plans to expand its microdisplay-based rear-projection television assortment to include 52" and 62" high-def DLP televisions.

DLP TV technology has found its way in product showrooms, and it's quickly finding itself "at home" in many peoples' living rooms.

Step 2:DLP TV: Rear Projection Television for a new generation

What Was Old (& Clunky) Is New Again: A Review of DLP TV's Innovativeness

DLP TVs are basically a new spin on an old technology, or, if you like, rear-projection television (RPTV) with a digital twist. RPTVs have been around for quite some time now. You no doubt remember those "big screen" behemoths whose dim, fuzzy-edged pictures "entertained" us in the 90s. Those CRT-based RPTVs are still around, holdovers from the last millennium.

DLP technology has brought rear-projection television into the 21st Century. Instead of three space-consuming electron guns, DLPs utilize a system of microscopic mirrors and lenses to reproduce video signals as light signals, which the eye sees--or brain reads--as full-blown images on the television screen.

This technology has eliminated any number of "issues" long associated with rear-projection TVs. For starters, DLPs weigh 1/3 to 1/4 what comparably sized CRT-based big-screen TVs do, making DLPs not only cheaper to ship but also easier to move around your house. (Compared to the 300-400 pound monitors they compete with, DLPs are virtual lightweights, weighing, on average, 85-100 pounds. They're substantially slimmer than old-fashioned RPTVs, too. 50" DLPs generally have depths < 16 inches.) The light output of one of these displays is also impressive, and, since there's no convergence, the picture remains sharp and clean from edge to edge, with none of the "touching up" cathode ray tubes require. As your set ages, simply replacing a light bulb will return it to "like new" performance levels. Not so with conventional RPTVs, which incur enormous maintenance costs over time, so much so that it's usually cheaper to buy new ones than to repair old ones.

The Bottom Line: Microdisplay projection TVs afford consumers that much-sought-after digital picture at a fraction of the price of flat-panel display sets. DLPs may not be as thin as plasma TVs, but they are dramatically improved over their much larger, much deeper predecessors. Some newer DLPs are even slim enough to hang on a wall!

Step 3: How DLP TV Technology Works

The Basics: DLP TVs are rear-projection units, meaning they create pictures by manipulating light, which originates from a centralized source, as it's projected onto a screen. If you've read our article on LCD displays, you already know that they work by blocking light. DLP TV monitors, by contrast, work by reflecting light: That is, they utilize a complex system of mirrors to reflect or deflect red, green, and/or blue light through a optical projection lens and onto the screen in front of you. These mirrors can switch between ON (where light is fully reflected) and OFF (where light is fully deflected) states. And, by switching between light and dark states at great speeds, these mirrors are able to reproduce the gray scale with staggering accuracy.

The Digital Micromirror Device (DMD): The functional core of DLP technology is the DMD semiconductor, which TI defines as a binary spatial light modulator. That's tech speak for an "on-" and "off-" (binary) moving (spatial) light regulator (light modulator)--a light switch, if you will.

Let's have a look at one of these semiconductors that Texas Instruments claims has "changed everything."

* Pictures complements of DLP.com

The principle behind these semiconductor chips is fairly straightforward. DMDs contain millions of microscopic mirrors--one for each pixel in their display--that can be directed to tilt 10° back and forth on their axes. These micromirrors are made of aluminum for maximum reflectivity and durability. They measure just 16 µm by 16µm (1 µm = 1 millionth of a meter).

16 µm² =
.000016 m x .000016 m =
.016 mm² =
.000256 mm of reflective surface area

Let's just say a strand of your hair is about five times the width of one of these mirrors.

These micromirrors are arranged into rectangular or square grids (depending on the DMD's aspect ratio), with each mirror separated by 1 mm. To the unaided eye, though, this 1 mm of space is invisible. So, what looks like one, solid thumbnail-sized mirror is really millions of micromirrors arranged in a grid pattern, like so:

DMD™ with Mirror Removal

The top left view shows nine mirrors. The top right view shows the central mirror removed to expose the underlying, hidden-hinge structure. The bottom right shows a close-up view of the mirror substructure. The mirror post, which connects to the mirror, sits directly on the center of this underlying surface. Lastly the bottom left view shows several pixels with the mirror removed.

DMD™ and Straight Pin

Micrographic photo of the tip of a pin on the surface of a DMD. Each mirror is 16µm per side, with a 1µm separation between mirrors.

* Pictures complements of DLP.com

The actual number of micromirrors present on a given DMD is equal to the number of pixels on your TV's screen (a k a its resolution). A display with a resolution of 1280 x 1024 contains a DMD consisting of 1,310,720 micromirrors. This "one pixel, one mirror" setup lends itself to exceptionally precise digital imaging.

The Mirror As Switch: Since each micromirror on a DMD chip operates independent of its neighbors on the DMD grid, each aluminum mirror can reflect light in one of two directions--either 10° toward or 10° away from a lens. The light the gets reflected is directed towards an optical lens, which projects that light onto a screen in the form of a lit pixel. A light absorber absorbs the light that is deflected away from this lens, so no light reaches the screen at that particular pixel, producing a dark, square pixel image. In short, each micromirror either illuminates a pixel (i.e., switches it ON by moving +10°) or darkens a pixel (i.e., switches it OFF by moving -10°). When these mirrors aren't in use, they remain "parked" at 0° on their axes.

Addressing the Switch: A DMD operates according to the data input into the static random access memory (SRAM) cells located beneath each micromirror. The data directing each mirror's tilt angle comes in the form of binary bit planes (i.e., ones and zeroes), where 1 = +10° tilt = ON and 0 = -10° tilt = OFF. The incoming video or graphics signal is decoded; the address electrodes are activated; and they produce the electrostatic torque necessary to rotate the mirror. If the mirror reflects light, that light is directed toward a projection lens, amplified, and then cast onto the back of a screen. If the mirror deflects light, it gets absorbed, which leaves a pixel-sized portion of the screen dark.

Note: With DLP technology, each pixel of information gets mapped directly to its corresponding micromirror. If the signal has a 640 x 480 sampling structure, the central 640 x 480 mirrors on the DMD will be active in broadcasting the picture. All the extraneous mirrors outside the 640 x 480 area will be tilted -10°, or "off," which preserves the integrity of the source image as it's processed and displayed.

Recreating the Gray Scale: With DLPs, grays are produced through the rapid oscillation of micromirrors switching between light and dark states. Grays are encoded in bit planes that represent the ratio of light states to dark ones, "on's" to "off's", ones to zeroes. A pixel's relative brightness is written in 8- or 10-bit segments, with each bit representing successively longer on/off durations. In an 8-bit word, for example, the time durations have relative values of 2⁰, 2¹, 2², 2³, …, 2⁷, which allows for 256 unique combinations of ones and zeroes or lights and darks. Each pixel is thus capable of displaying 256 or 28 equally spaced shades of gray or relative brightnesses. 10-bit image processing boosts conventional gray scale gradations by a factor of four to 1024 or 210. Lighter shades of gray consist of more "on's" than "off's," and darker grays consist of more "off's" than "on's." The gray scale you see is effectively the analog version of a purely digital light signal. This technique for producing the sensation of the gray scale before a viewer's eyes is called binary pulsewidth modulation.

Coloring the Gray Scale: DLPs utilize a color wheel composed of red, green, and blue filters, which direct individual pulses of colored light toward the DMD for gray-scale processing. This means that, at any given instant, only one of the primary light colors is hitting the DMD, but when the filter system spins fast enough (~120 time per second), the colors appear blended into a full-color digital image. DLPs display color images as rapid sequences of red, green, and blue light signals, which the brain integrates or reads this sequential color data as an analog or "whole picture" signal. The result is an image teeming with colors. [After all, 256 shades of red x 256 shades of green x 256 shades of blue " 16.8 million different colors!]

All this color blending and/or image formation, known as "averaging," is performed on the viewer's end, so DLP TV technology respects the digital integrity of video/graphic signals from start to finish. This ensures that the image you see on your TV screen is an exacting rendition of the source material, as it were, bit for bit.

Note: Because DLPs "stack" red, green, and blue components of light over a period of time--albeit an exceedingly brief period of time (milliseconds)--it is theoretically possible to see a "rainbow effect" on your TV screen. This is an instance where the colors apparently fail to layer properly, so that viewers perceive discrete transitions from red to green to blue on the screen (hence the "rainbow" euphemism). Few people are genuinely bothered by this phenomenon, and it seems mainly to occur on the earliest DLP models. Second- and third-generation DLPs have been reengineered to mitigate such color separation.

Still, the only way to figure out if you're sensitive to the speed of the color wheel and can see artifacts generated as it spins is to do some viewing tests of your own. You should try out a variety of video material because this effect tends to be content-specific, i.e., more prevalent in the dark areas around a moving bright spot.

Step 4: Advantages of DLP TVs

DLP TVs look cool and save space, but what are the real advantages of owning one?

First of all, it's easier to watch. DLPs are inherently brighter than other display technologies because it is a reflective device. Its higher-than-average light efficiency means that a DLP TV will perform exceedingly well under most ambient light conditions. Brightly lit rooms won't wash out the pictures on DLP televisions. DLPs can achieve deeper, more realistic shadows and blacks than other fixed-pixel display technologies because DLPs create blacks by reflecting light away from the screen. And you don't have to worry about eyestrain, since DLP TVs don't flicker the way old-fashioned TVs do.

A Note on Off-Axis Viewing & DLP Technology: One of the quirks of DLP TVs is that their viewing angles are one dimensional--i.e., horizontal. You can watch your DLP television about 70° to 75° in either direction from the center of the screen along what would be the horizontal or y-axis. This is not true of the vertical viewing axis. DLPs need to be positioned at eye level--any higher or lower makes for an awfully dim viewing experience. This is one area where flat-panel technology takes the prize for viewing flexibility. The picture is also smooth, colorful, and impeccably realistic. DLPs have none of those annoying scan lines that conventional CRT-type sets do. This owes to the fact that each pixel has its own optical equivalent in the DMD chip itself. The result is a smooth, evenly lit image across the whole display surface. Unlike the rear-projection units of yesteryear, the picture on a DLP is clear and bright all over--even at the edges.

The square micromirrors on a DMD chip are 16mm2 with 1mm gaps separating them, which translates into a fill factor approaching 90%. (By contrast, the best LCDs have fill factors of just 70%.) About 90% of the total pixel/mirror area actively reflects light when images are being displayed. This tight interpixel spacing renders individual pixels nearly invisible: There's so little "dead" or non-image-generating space between pixels that you can scarcely tell where one pixel ends and another begins. High fill factors make for higher perceived resolutions, which make for virtually seamless pictures. DLP TVs don't suffer from the "screen door" effect (a k a "pixelation"), where a faint impression of the pixel grid seems to be overlaid on the screen.

Because of the high speed with which the micromirrors on a DMD switch on and off--approximately 50,000 times per second--DLPs display moving images with ease and virtually no motion artifacts or image streaking. Which means that DLP TVs are well suited for gaming.

DLP TVs deliver strikingly clear, non-pixelated images with perfect geometry. Unlike CRTs, DLPs can display perfectly straight lines. This makes DLP monitors especially good for use with graphic-intensive software applications like PageMaker or Excel.

And, you can watch your new DLP TV right out of the box because the tuner is built-in. DLPs generally come with NTSC tuners and speakers already built-in to them, which equip them for standard-television watching. Some of the newer DLP models also include ATSC tuners for high-definition reception. Since DLP TVs don't require external tuning devices, they are ideal for situations where less is more--at least with respect to wires coming out the back of your TV (e.g., houses with small children, etc.).

Finally, these displays are multi-functional and extremely long-lived. A DLP is a television monitor, capable of displaying HDTV, standard TV, and home video. It's also a computer monitor. In fact, it can accept almost any video format. DLP TVs typically include inputs for (a) composite video, (b) S-video and component video, and (c) one or more RGB inputs from a computer. Because of the high resolution and perfect geometry of DLPs, text and graphics look especially sharp when viewed on them, which makes them one of the best solutions for displaying data and web-based content. And, of course, you can view static images like Excel spreadsheets with impunity since it is literally impossible to "burn-in" projected images onto a TV screen.

You can expect to use your DLP monitor in many capacities for many years to come. The only element of the display that suffers from wear is the light source, which can be easily replaced--without much technical assistance--to obtain "like new" performance levels. They utilize very bright light sources, such as Metal Halide or Ultra High Performance bulbs that last between 8,000 and 10,000 viewing hours. The bulbs cost about $250. All of which makes DLPs inherently reliable: Even the most committed couch potatoes won't be able to "burn out" his or her TV. This could literally be the last television you'll ever buy!

If you'd like to learn more about the reliability of Texas Instruments's DMD chip, take a look at one of its White Papers covering this topic: http://www.dlp.com/dlp_technology/images/dynamic/white_papers/135_Myth.pdf

Step 5: DLP TV Purchasing Considerations

What do you need to consider before you buy your flat screen DLP TV?

Determine the right screen size based on your budget and your floor plan. The big story in the rear-projection TV category has to do with the newer lines of widescreen DLPs with cabinet depths of less than 7 inches. Manufacturers claim these models can be hung on the wall. And DLPs are getting bigger all the time. You can expect to see 70-inch versions of flat-panel DLPs in stores by 2005.

To get the most out of your investment, remember what your mother always said about sitting too close to the TV-that it's no good for you. Well, she might have been thinking about your health, but we're thinking about your viewing pleasure. For the optimal viewing experience, you need to keep a comfortable distance between your viewing area and your television screen. You can certainly watch your DLP up close, but one of the great joys of owning a widescreen TV is that you can sit back and watch it!

Note: Some audio-visual critics have observed that fixed-pixel displays tend to show their pixel structures at closer viewing distances, so one might notice a sandy texture to the screen when the set is viewed too close. The high fill factor of DLP TVs does a lot to minimize this effect.

Choose a comfortable viewing distance based on the screen size of your DLP TV:

For 42 to 46-inch DLP TVs, might consider putting 10 to 14 feet between you and the screen.
50-inch DLP displays will look good from as far as 12 to 16 feet away, though you can certainly sit closer to the screen.
You can sit up to 15 feet away from a DLP screen that's larger than 60 inches. Again, the high fill factor inherent to DLP technology enables you to sit much closer to the screen without being annoyed by pixelated images.

Get the lowdown on HD compatibility. If you're one of the 55+ million households sitting astride cable systems that can carry HDTV signals, your LCD TV will enable you to take advantage of the slightly better (10-15%) picture you can get from a higher resolution unit displaying HDTV broadcasts. Most LCD units come with built-in ATSC tuners, which enable them to pick up over-air HD broadcasts using antennas. In addition, manufacturers have begun packaging ATSC and cable tuners in LCD TV sets, making them optimal for watching HDTV-on local as well as national broadcasts.

Tip: To learn more about the availability of HDTV broadcasts in your area, or for a lineup of programs shown in hi-def, consult the Consumer Electronic Association's website: http://www.ce.org/publications/books_references/dtv_guide/default.asp

Step 6: Placement Options

Imagine all the possible places you can set up your DLP TV. DLP technology has recently introduced super-slim versions of their already slender TVs, which affords consumers new options when it comes to the physical placement of their TV displays. Gone are the days when you had to configure a room around the television set. Now, you can incorporate the TV into almost any décor, if you give a little thought to the matter beforehand.

Note: When you're investigating possible locations for your television, remember that DLPs look best when viewed at eye level. Their pictures are spoiled by vertical shifts in the viewing axis. That is, when you view your DLP from above or below its central axis, the picture dims considerably. You need a full, front-on view of the screen to witness the true luminosity of rear-projection technology.

Step 7: Where should you go to buy your DLP TV?

If you go with a traditional, "brick and mortar" retailer, remember to shop around-not just for the best prices but also for the best equipment. While established retailers are almost always authorized dealers of what they sell (which ensures the manufacturer's warranty will be upheld) and have more lenient return policies (restocking charges notwithstanding), they usually have a vested interest in which brand of TV they sell you. Many of the chain stores like Best Buy and Circuit City tend to push one manufacturer's products over another's based on issues totally unrelated to the merits of the products themselves. Some manufacturers offer incentives, or threaten to withhold merchandise, to achieve higher sales volumes. All of which means the big retailers do pretty much what the manufacturers tell them to do with-and say about-their products.

There are essentially two types of retailers selling high-end television sets. They differ in terms of price structure and technical know-how.

On the one hand, you have the "big box" retailer, which are the ones with the best prices and the worst service. Their employees are poorly qualified and poorly compensated. These retailers generally appeal to price-driven consumers.
The smaller home theater stores and middle-sized specialty chains, on the other hand, tend to be long on know-how and short on price-breaks. Their salespeople know the products they sell fairly well-sometimes really well. You'll typically find a bit better equipment at these stores as well as more diversity in makes and models of TVs. But, all this comes with a price: You'll probably pay more for your DLP TV at these stores. Just know that you're paying more for merchandise that will last and comes recommended by someone who knows something about it.

Regardless of which type of retailer you go with, the principal advantage of going with a traditional retailer is this: You get a chance to see-and watch-what you're buying before you actuallycommit to buying it.

If you go with an online dealer, expect to pay MUCH less for your TV-and to do some pretty extensive homework beforehand. We have all heard tales of online transactions gone wrong, where unsuspecting customers get stuck with defective, damaged, or otherwise sub par merchandise. If they are left with anything at all, that is.

There is a wide range of quality and professionalism among the electronics dealers you'll find online, so you need to check them out before you even think about doing business with them. Looks can be deceiving. A professional-looking website is a good sign, but it's no real insurance against an eventual case of buyer's remorse. Nor is paying with a credit card. Credit card companies can only protect you to a point. Ultimately, you are bound to the dealer's sales and returns policies.

Generally, you're looking for an established, specialized electronics vendor that can give you a good price and good service/support.

When buying your DLP TV from an online dealer, be sure to get someone on the phone so that you can do some investigating.

(1) Find out if the company you're dealing with is an Authorized Dealer of the TV you're thinking about purchasing. Most Internet e-tailers are not authorized, which makes ones that are stand way out from the rest of the pack. Getting authorization to sell a given manufacturer's products is no easy process. Dealers have to meet some fairly stringent standards. Manufacturers usually require their dealers to offer technical support through a service center of some sort. In almost all instances, they will also require dealers to have a showroom for the product and a warehouse for the stock.

Internet companies that are not authorized retailers of the electronics they sell normally do nothing more than drop ship those products from distributors or other dealers. All of which means they have no way of replacing defective merchandise, getting spare parts, or handling returns. Nor can such dealers guarantee that the TV you get will be new, unopened, or unused.

(2) Ask, "What if…?" Imagine everything that could go wrong, and then ask a sales representative how his or her company would handle the situation. What if the DLP unit you receive is defective? What if your display goes bad after six months? What constitutes a "defective" monitor? Will they take the display back? Or, how can he or she guarantee you that your television will be repaired?

(3) Find out where they're located. Check the physical address of the company, and exclude those listing P.O. boxes or foreign countries as their addresses. You should also verify any address information with the Better Business Bureau (if the BBB insignia is posted on the website). Why? Because, if a dispute should arise, you need to be able to contact the company in writing.

(4) Determine whether they stock the products they sell. Many companies will claim to have a physical location, when they are really home- or apartment-based operations with little or no control over what happens once the transaction has been made. Always try to purchase from a dealer that buys direct from the manufacturer and stocks inventory.

(5) Ask whether they have corporate clients. If a vendor services other businesses, chances are, they're legitimate.

(6) Ask some technical questions about the products they sell. Make sure these people are competent enough to give you some after-purchase technical assistance should you need it.

(7) Get the low-down on the warranty. Inquire into the specifics of the dealer's return policy. It should give you one month's time to have any defective unit replaced at the seller's expense (shipping charges included).

You should also expect to pay some reasonable shipping fees. "Super saver" shipping is fine for books. But shipping a high-end digital television via the cheapest method possible will almost certainly turn into a major hassle down the road. In most cases, the costs of shipping are offset by the money you save by not having to pay sales tax on the purchase price of your DLP unit.

Which online vendor should you use? Purchasing a cutting-edge digital TV is a big decision, so you probably want to go with one of the principal online retailers. The following list is list of recommended online dealers:

DTVCity - Official Sponsor
PlasmaDepot
DTV Express

View all online stores offering DLP Televisions

Step 8: DLP TV Retailers

Purchasing a DLP TV is a big decision, currently the following companies are the main online DLP TV retailers. Before you purchase your DLP TV we suggest you read our How and Where to Buy a DLP Television article.

The following is a list of recommended online retailers:

DTVCity - Official Sponsor
PlasmaDepot
DTVExpress
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All Online Retailers

DTVCity - Official Sponsor
PlasmaDepot
DTVExpress
BestBuy
Office Depot/School.com
Circuit City
Net TV - Digital Displays
Good Guys
Fry's Electronics
HDT Vision
Info Tech America
One Better Buy
iGadget
Giant Savings
Manufacturer Sites

Samsung DLP TV
Optoma DLP Televisions
RCA DLP TVs

Other Resource Sites

Plasma TV Science
Plasma TV Buying Guide
LCD TV Buying Guide
Projector Buying Guide

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