LCD, DLP and LED Projectors — The Differences
Differences betweent the types of projectors -- LCD, LED, and DLP
More than just alphabet soup, these projectors each have something specific to offer.
By Sharon Fisher

Sometimes trying to figure out data projector technology is like dealing with the government, with all the TLAs (three-letter acronyms). LED, LCD, DLP…what do they all mean?

First of all, there’s two basic components in a projector: lighting, and the imaging/display device technology, says Joe Gillio, director of product marketing for Casio America Inc., in Dover, N.J.

Traditionally, there’s been one type of lighting source — the lamp — though the technology behind the lamp has improved over time. The move to metal halide bulbs, and then to the ultra-high pressure mercury lamps used today, has both reduced the cost of the bulbs, and improved their lifetimes. The result is that projectors using bulb technology are more reliable today than they ever have been before, says Felix Pimentel, product manager for Optoma Technology Inc., in Fremont, Calif.

But in the past few years, the industry has developed projectors using a different lighting source, the light-emitting diode (LED). LED-based projectors offer a number of advantages over traditional lamp-based systems.

First, they tend to have a longer lifespan — up to 20,000 hours, compared with the mercury vapor lamp, says Gillio. This makes the projectors more reliable, because they fail less often, and don’t “burn out” like lamps do. In addition, the mercury in LCD projectors is environmentally hazardous, he says, which is not a factor with LEDs.

While the LED light sources are more expensive, they save money in the long run because they fail less often, Gillio says. Because lamps aren’t typically the kind you can go down to the corner and buy, a salesman on the road or a teacher in the classroom with a blown bulb faces the cost of the downtime until the bulb can be replaced, he says.

Another advantage of the LED lighting systems is that they provide a larger number of colors, and more saturated colors, on the screen, meaning the LED system “looks” brighter, Pimentel says. LED projectors also tend to have fewer parts because the LED performs some of the functions that require additional parts in lamp-based projectors. This means LED-based projectors can be smaller and lighter than lamp-based ones, he says. They also use as little



Comments
Posted by James Fife  on  12/03  at  11:34 AM
One of the things that has been toted a lot about LED based projectors is the 'larger' number of colours. The issue is difference between primary colours and secondaries that fill in the colour space. The primary colours are very vibrant, however the spaces between has a lot less energy. It is like having a very loud sound system that only have 32 narrow bands of power. Yes it is loud, and can extend from 20-20k possibly, but that doesn't make a nice flat response. Take a look at the graph of a three emitter LED engines output colour spectrum and it becomes apparent. The level difference between the RGB spikes and the spaces is around 90-95%. Yes that may make the image look punched, but it has to be. The colour spaces that are not covered end up over saturated because there is nothing else the projector profile can be programmed to do. Proper multi colour emitter projectors need to have filters on the peaks and start to include secondary emitters to ensure a flat base light before the imaging section of the projector. So that means the inclusion of not only RGB, but CMY as well.
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