HDTV pushes displays to perform

DN Staff

April 3, 2000

5 Min Read
HDTV pushes displays to perform

Plano, TX -Does Monday Night Football have you eyeing your 27-incher and wishing for a high-resolution big screen to make those images look like a seat on the fifty-yard line? If you're like many people, you may be holding out on that big screen purchase. Poor picture quality in today's systems may be the reason why. Another downside is size-you may think you have to give up the whole living room to get good picture quality. And what about HDTV (high definition television)-isn't it right around the corner?

Crisp image quality, low weight, and portability have made digital light processing, or DLP, projection popular in the business market, from ultraportable projectors for on-the-road presentations to high brightness systems used at trade shows. Since the technology was first unveiled in 1996, the world has become increasingly digital-with digital image capture, editing, and transmission seen in high-definition television, 64-bit gaming systems, digital cameras, and DVD-digital projection seems the next logical step. This year consumers will see the launch of large screen, HD-capable home entertainment systems based on Texas Instruments' DLP technology, which the company says provides higher contrast, color accuracy, and sharper video images than liquid crystal display or cathode ray tube-based systems. The DLP also offers size advantages, says the company, since it can be housed in a compact cabinet that is smaller than the enclosure required for a conventional large screen television.

Digital light processing (DLP) projection system consists of optics, color filters, digital processing and formatting, a digital micromirror device (DMD), and a projection lens.

"To display all the information which the family of the future will demand," says Dale Zimmerman, home entertainment project manager with Texas Instruments, "the screen will have to be large-which means that the CRT is unlikely to be able to compete without filling the entire living room." DLP enables the design of large screen systems, which can be housed in compact cabinets. LCD has not yet demonstrated that it can deliver acceptable video image quality of HD applications. "Plasma is everyone's idea of the TV on the wall, but it continues to be very expensive and still has a long way to go in terms of image quality," says Zimmerman.

Both Mitsubishi and Hitachi will use DLP technology in all-digital, large-screen, high-definition rear-projection television, which will go on the market this year.

Texas Instruments' digital light processing system consists of a light source, optics, color filters, digital processing and formatting, a digital micromirror device (DMD), and projection lens. It operates under an extremely simple principle. The DMD, an optical semiconductor chip that has 500,000 microscopic mirrors mounted on a standard logic device, is the heart of the system. Each mirror represents one pixel. These tiny hinged mirrors (480,000 SVGA, 786,000 XGA, or 1,310,000 SXGA) operate as optical switches-either reflecting light away from the lens (off) or through a lens (on) to create a high-resolution, full-color image. Electrodes under opposite corners of the mirror are activated by the incoming video or graphics signal and cause each mirror to tilt thousands of times per second. This structure yields pixels that can switch on or off more than 5,000 times per second in response to incoming digital signals. Each square micromirror is about 1/5th the thickness of a human hair. The gap between the mirrors is less than one micron, giving DLP images a seamless appearance. Light is either reflected through the lens onto the screen-in which case a white pixel appears-or away from the lens, in which case a black pixel appears. Shades of gray are projected by varying the proportion of time each mirror is "on" or "off."

Projectors contain a one-chip DLP, with big-screen systems containing two-chip systems, and three-chip subsystems available for large audience applications.

A digital micromirror: each digital light-processing device contains 1/2 million of these tiny devices.

DLP has three key advantages over existing projection technologies, says Texas Instruments. The inherent digital nature of DLP enables noise-free, precise image quality with digital gray scale and color reproduction. Its digital nature also positions DLP to be the final link in the digital video infrastructure. DLP is more efficient than competing transmissive liquid crystal display (LCD) technology because it is based on the reflective DMD and does not require polarized light. Finally, close spacing of the micromirrors causes video images to be projected as seamless pictures with higher perceived resolution.

Applying the technology to cinema applications, The Walt Disney Co. used DLP for all-digital showings of Disney/ Pixar's Toy Story 2-the first ever major studio feature to be released in both digital and a traditional film format.

For more information about digital light processing devices from Texas Instruments: Circle 536



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