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.
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.
