LEDs boost television ratings at Consumer Electronics Show

Rear-projection televisions using DLP technology and LED light engines were demonstrated at CES 2006 last week.

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Televisions featuring LED light sources were much in evidence at last week's Consumer Electronics Show in Las Vegas. In the last year or so, several companies have introduced LCD televisions featuring LED backlights, and at this year's event Samsung introduced an 82-inch monster.

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Samsung DLP TV with LEDs
However, attention was focused on a different type of TV - rear projection television (RPTV) using digital light processor (DLP) technology. Both Samsung and Akai unveiled rear-projection DLP sets in which the traditional bulb and color wheel are replaced with an LED light engine.

Generally, DLP television offers large screen sizes and excellent image quality, but the sets are deeper than "flat-screen" LCD and plasma displays, and there are issues with bulb replacement and the rainbow effect. Many of these disadvantages are addressed by replacing the bulb with LEDs.

Samsung Electronics' HL-S5679W 55-inch DLP rear-projection TV, capable of reproducing high-definition TV (HDTV) images, incorporates a 1080p (1920 x 1080) DLP chip supplied by Texas Instruments.

The set uses 18 LEDs, 6 each of red, green and blue, and eliminates the projection bulb and color wheel found in other DLP televisions (see "How it Works", below).

Akai's PT52DL27L AND PT42DL27L are 52-inch and 42-inch RPTVs, respectively.

The LED light source provides a much wider color gamut than a standard bulb, and much longer lifetime of around 20,000 hours, compared with the 3000-6000 hour lifetime of bulbs, which are replaceable at a cost of $300-$500. Another advantage of the LED light engine is more rapid switch-on time of around 7 seconds

Getting rid of the color wheel eliminates the so-called "rainbow effect", a visual artifact that can appear on screen as flashes of red, green, and blue shadows at the edges of the viewer’s peripheral vision.

Shipments are expected to begin in April, priced at around $4200. The price differential between the HL-S5679W and Samsung's standard DLP sets is less than that between standard flat-panel LCDs and the newer LED-backlit equivalents.

Electronic Business magazine reported John Reder, TI manager of worldwide DLP strategy & business development, as describing LEDs as “the shape of things to come," adding that until now, limited brightness and cost prevented LED sets from being viable in the market. “LED gives you a lifetime of illumination," said Reder. "The brightness almost matches the bulb, now.”

How it works – DLP television

Invented by Texas Instruments, DLP technology is essentially a state-of-the-art optical switch based around a digital micro-mirror device aka the DLP chip. This is a rectangular array of up to 2 million microscopic mirrors that can tilt back and forth in response to on and off signals. The mirrors reflect light from the light source onto the rear of the TV screen.

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Conventional DLP system
When the lamp and projection lens are coordinated with a digital signal, television images are projected onto the screen. This is the only all-digital television display technology: LCD and plasma displays convert digital signals to analog at the last step.

Each DMD mirror corresponds to one pixel of light in a projected image. A white pixel is produced on screen when the mirror is tilted towards the light source, and a black pixel results if the mirror is tilted away. The DMD mirrors can switch thousands of times per second.

To introduce color, most DLP systems have a color wheel between the light source and the DMD mirror panel. As the color wheel spins, it allows red, green, and blue light to fall onto the mirrors; this is coordinated with the on and off states of the mirrors to produce more than 16 million of colors.

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