Television - Which Technology?

Television technology can boggle the mind if you’re not sure what the mechanics of different types of displays offer. We can get lost in the terminology. Would a Rear-projection or direct-view CRT be best for my needs? Maybe a rear-projection DLP or LCoS would be more what I’m looking for. And what about those LCD and Plasma flat-panel TVs…would one of those be the best choice for me? There are several styles of HDTV display technology, each with its own pros and cons. Read on, if you dare, to discover all you ever wanted to know, and then some, about TV technology.

DIRECT-VIEW CRT
Accounting for the greatest number of TVs in American homes are the traditional tube-type TVs. Direct-view CRT TVs use a glass picture tube called a cathode ray tube (CRT) to produce sharp, bright images that can be viewed in almost every room in the house regardless of the brightness of the room. They utilize the same fundamental design as analog TVs with improved technology. The most recent technology involves flat tube designs to increase viewing angles and eliminate the traditional curved screen that can cause glare. HDTV direct-view TVs have 16:9 widescreen flat tubes. Screen sizes for a direct-view CRT range from 12 to 40 inches and the average lifespan is about 20,000 hours of viewing time.

The strengths of direct-view CRTs are that they can reproduce deeper, darker blacks than any other type of TV and that they are bright enough to be viewed even in an extremely bright room. Also, the color characteristics are superb regardless of viewing angle and no convergence adjustments are required due to the use of a single light source.

The drawbacks of direct-view CRTs are their bulk, weight, and deep cabinets (CRT TVs can be over 25” deep, weighing over 200 pounds) making it difficult to use in crowded rooms and very hard to transport. Older technology does involve a curved screen that reflects glare, but as mentioned before, new flat picture tubes are correcting this problem.

REAR-PROJECTION CRT
Although it is the least advanced in projection technologies, rear-projection CRT provides high-definition performance on a big screen for much less cost than the newer technologies. CRT-based projection uses three separate cathode ray tubes (red, green, blue) to project three beams that have been combined and magnified onto a specially formulated screen that will then diffuse and transmit the light as a single composite image. Screen sizes range from 42 to 65 inches and up.

Even though these TVs perform well and are less expensive than thin TV technology, the drawbacks are numerous. Their bulk, weight, and depth (these screens are contained in a large cabinet with the light sources, electronics and projection system) make these TVs hard to place and almost impossible to transport. Adjustments may need to be made intermittently to converge the three beams into a single sharp image; however, new technology offers automatic digital convergence. Because of their limited viewing area, to see a clear picture you must view these screens straight-on; if viewed from the side or while standing, the picture may appear dimmer, faded, or discolored. Rear-projection CRTs are hard to view in a sunlit room and could be victim to screen burn-in, permanent imprints on the screen caused by extended viewing of static image elements.

REAR-PROJECTION DLP
Digital Light Processing (DLP) technology is a revolutionary new way to display and build rear projection TVs developed by Texas Instruments. This technology utilizes a DLP chip (about the size of a postage stamp) loaded with a million tiny, individual mirrors based around a semiconductor called a digital micromirror device (DMD). These tiny mirrors can move thousands of times every second. When a single light source is shone on the DMD and the mirrors are moved, the reflected light will pass through a spinning color wheel to filter the light into red, green, and blue, and sometimes white and yellow. Because of this technology, the DLP light engine is able to create images with subtle color variations that will be magnified and projected onto the screen. Screen sizes are 42 inches and up.

An advantage of DLP technology is that DLP TVs have no CRTs making them much lighter and much less bulky (many of them measure less than 17” deep, weighing less than 100 pounds). The single bulb is easy to replace at a lower cost, so DLP TVs keep their like-new brightness and there is no need to make adjustments for convergence because the DLP chip stays in place. DLP TVs are not susceptible to screen burn-in, so you never have to worry about stationary images. These sets are easily viewed even in a bright room because the DLP light engine can produce high brightness. Great reproduction of blacks gives the DLP TV superior performance when compared to other non-CRT projection technology.

Although DLP TVs do have several strengths, a major drawback is that the spinning color wheel creates a “rainbow effect” that could be noticed by sensitive viewers. Also, they aren’t as bright as LCD technology nor as compact as LCD or Plasma flat-panel models.

REAR-PROJECTION LCoS and HD-ILA
LCoS (Liquid Crystal on Silicon), the newest in microdisplay technology, mixes liquid crystal and reflective technology and works with ultra-bright light to produce sharp, focused, high-contrast images. LCoS technology uses three reflective light imagers, a prism, and a lens system to transmit light as a laser-like beam that is imprinted with a high-definition image that is then magnified and displayed on a widescreen.

Advantages to rear-projection LCoS sets are that the brightness is uniform and that there is no need to make adjustments for convergence.

HD-ILA is the most technologically advanced microdisplay. Created by JVC, HD-ILA is based on D-ILA (Direct-drive Image Light Amplifier) technology and uses a 3-chip, LCOS technology vertically aligned to stabilize the performance and maximize chip production. Made up of 13 separate glass components and aspheric resin coated lens, 32 layers of anti-reflective coatings on each element make it possible to create pure, sharp images. The gray-scaling, brightness, color reproduction, and resolution excel when compared to other LCOS technologies.

LCD FLAT-PANEL
The screen on an LCD (Liquid Crystal Display) flat-panel TV is like those you see on lap-top computers. The flat-panel measures about 3” to 4” deep and is very lightweight. LCD flat-panel TVs are much brighter and offer more contrast than CRT TVs, so they are easier on your eyes and can be viewed in very brightly lit rooms. LCD flat-panel TVs contain three high-resolution HTPS (High Temperature Poly-Silicone) LCD image panels (one for red, blue, and green) to give excellent color without a color wheel. Each panel holds up to one million pixels and each pixel has its own thin-film transistor (TFT) etched onto the cell’s glass surface with the electrical conductors. Special mirrors split light into red, green, and blue beams that are combined into a full-color image by a prism and then projected through the lens. LCD TVs can be SDTV, EDTV, or HD and come in either 4:3 or 16:9 aspect ratios. They are compatible with multiple systems including your computer and screen sizes range from 10 to 40 inches or more.

Advantages of LCD flat-panel TVs include excellent color and brightness with resistance to screen burn-in from stationary images. They are slim and lightweight, so they can be placed or mounted almost anywhere and are easily transported (excluding the largest screen sizes); plus, they look very stylish on the stands that are made for them. LCD flat-panels have uninhibited viewing angles up to 170 degrees off axis and use relatively little electricity and run cooler and more quietly than most other plasma displays. Also, there will never be a need for alignment adjustments because the panels are in a fixed position.

LCD TVs also have their disadvantages. Their brightness comes at the expense of very deep blacks so the contrast ratio is not as good as what a DLP or direct-view TV would produce. A slow refresh rate in older models produces blurring or smearing of fast-moving images, but new improvements have been made to minimize this effect. New improvements have also been made to minimize another disadvantage, the “screen-door” effect that occurs because of the distance between the pixels on the screen.

PLASMA FLAT-PANEL
Plasma flat-panel TVs work differently than any other TV technology because the light is produced independently at each pixel on the screen instead of being projected from another light source. The screen displays hundreds of thousands of individual cells (3 for each pixel on the screen coated with red, green, and blue phosphors). Each cell is filled with a rare-gas mixture and connected to an electrode. This gas is converted to a plasma state that emits an ultraviolet light when the electrode is charged with an electrical voltage. The light makes the phosphors react producing bright visible light. The pixels receive instruction from software on the electrostatic silicon board which varies the voltage and intensity of the electrical charge to combine the red, green, and blue light to form a composite image. Plasma flat-panel TVs have multiple functions and a long lifespan (an average of 30,000 hours in viewing time). They can display HDTV, analog TV, and home videos and can act as your computer monitor. Screen sizes range from 40 to 70 inches and up. Something to note is that not all plasma TVs come with a tuner or speakers, so you may need to purchase these.

Plasma TVs perform well under most lighting conditions and can be seen from a 160 degree viewing angle. Unlike traditional TVs, plasma flat-panel screens have no scan lines and offer excellent color realism and gradations among colors. These TVs are ultra-thin (less than 6”) and lightweight allowing you to save space and mount them almost anywhere. There may be installation issues by running cables and wires behind walls, so you may want to consult a professional before installing.

A disadvantage to plasma flat-panel TVs is that they are especially vulnerable to screen burn-in because of the direct way they produce light, but new technology to limit this problem are beginning to include “pixel-orbiting” to shift the images, almost imperceptibly by the viewer.

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