Electronic Design

LEDs Hold The Key To DLP Advantages

The driving forces behind Samsung’s 50-in. HL-T5089S display are Texas Instruments’ MEMS-based Digital Light Processor (DLP) Discovery Digital Micromirror Device (DMD) and Luminus Devices’ Phlatlight LEDs (see the figure).

The HL-T5089S delivers a great HDTV picture for less money and uses less power than large-screen LCDs and plasma displays. It’s surprising that the core of this large-screen rear-projection system fits in the palm of your hand.

The move to LEDs has had a significant impact on DLP displays. LEDs greatly extend the life of a critical and previously expensive component, the light source. DLP display bulbs used to require replacement every couple of years, and the bulbs were costly. However, the LEDs are rated at 20,000 hours. LEDs also eliminate the motor and color wheel in single-DMD systems. And, they simplify the system’s optics.

Another significant difference with LEDs is the removal of the “rainbow effect” caused by the bulb and color wheel. LCDs and plasma displays used to have a burn-in problem that has been effectively eliminated, putting all three technologies at a similar level.

Luminus Devices’ Phlatlight LEDs also have the advantage of requiring less power for the same amount of light than a bulb. This translates to less heat. Likewise, the performance and light characteristics of these photonic lattice LEDs is significantly better than a conventional bulb.

DLPs have a high dynamic contrast ratio, and the use of LEDs and new DMDs has increased this performance. The LEDs are a factor in high-dynamic-range (HDR) displays, but not just for DLPs. The move to LED backlighting for LCDs is beginning. Luminus Devices is a major player in the backlight race as well.

Plasma displays and LCDs have pushed DLP technology to the high end of the consumer space. DLP technology also dominates projection systems, including home theater environments and movie theaters that are moving from film to digital projection systems.

The HL-T5089S continues the trend toward thinner DLP HDTVs, but DLPs are unlikely to reach the thin profile of LCDs and plasma displays. This can be a challenge when it comes to wall-mounting, and more than a third of all large-screen HDTVs are wall-mounted.

Significantly more hi-def displays are wall-mounted in the digital signage arena. The wall-mount issue is only a thickness issue because DLPs are often lighter than their counterparts, since DLPs are mostly airspace inside. They also run cooler.

The HL-T5089S is 13.4 in. deep. Likewise, wall-mounting very large screens where DLPs exist is less important than it is with smaller screens. The depth of the screen is insignificant in a room large enough for displays that are this big, negating the depth advantage of LCDs or plasma screens.

Room size also has a large impact on the other limitation of rear-screen DLP systems—viewing angle, which is less than plasma displays and LCDs, but not by much. This can make a difference in digital signage applications where a viewer may come in from the side, but it makes little difference in a home where seating is normally arranged in front of the display.

It’s not surprising how many salesmen try to steer customers to higher-priced LCD and plasma options by noting how bad a DLP display looks when you’re standing above and off to the side in an aisle only 4 ft wide when you should be viewing it from the front sitting on a couch.

Samsung’s latest DLPs, the Series 6 and 7, should be showing up in stores about now. They supercede the HL-T5089S and use improved versions of TI’s DMDs and Luminus’ LEDs. The newer models also offer 120-Hz Cinema Pure color engine performance. LED life is rated at 60,000 hours. They only draw a cool 230 W. The line tops out with a 72-in. model.

So if you can still find an HL-T5098S, it’s worth the investment. If not, keep an eye out for the Series 7 and 8 or competing DLP rear-projection systems. For my money, they are the best bargain for a home theater.

Luminus Devices www.luminus.com
Samsung www.samsung.com
Texas Instruments

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