Projectors: LCD Verses DLP (The downfall of DLP technology)

July 19th, 2010

The most common question asked when buying a new projector for the home, office, or classroom is: will I get an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two most common projector imaging technologies. With so many brands and models available, it can be difficult for the buyer to make a choice between both technologies. The simple fact of the matter is that LCD projectors provide far superior image quality and colour accuracy. The following article tells you why DLP projectors struggle with projecting an equal level of image quality.

Visualise a set of blinds in your home over your bedroom window. By pulling a rod you can turn the shutters open or closed, depending on if you want to let light in or not. And this is exactly how an LCD projector works. Each pixel works like a single shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is constructed of millions of microscopic mirrors or ‘pixel elements’ as the pros like to call them. Each pixel element works to either reflect light or block it.

How the light source is processed from the point when the projector is switched on to when the picture reaches your screen is extremely important for image quality, brightness and colour accuracy. LCD projectors shine white light from the lamp by separating it into red, blue and green components, by three mirrors which project the coloured light to 3 different LCD panels. The 3 LCD panels make the elements of the image by switching each pixel on and off. The pixels are then meshed in a glass prism to form the projector image. A point to know about LCD projectors is that all three colours are directed onto your wall all at once. The way a DLP projector works is very different and even the way an image appears is not the same. With DLP, white light from the lamp is sent through a spinning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of projecting an image forms a sequence of red, blue and green light. The millions of micro mirrors as mentioned above reflect the coloured light on the pixels to create the image elements. The elements of the image are sent in sequence on the screen, one colour at a time. The viewer’s vision will then put together each coloured element of the image into the single complete image. From LCD projectors, all colours are available all the time to form top brightness and spectacular colour accuracy. In DLP, just one colour is available at once, and so causing lower colour brightness and accuracy. Some developers have included a white segment in the colour wheel to improve all over brightness, but this then degrades colour accuracy.

I see in forums all the time that DLP has a higher contrast ratio and thus must be superior quality. For those who are uncertain, the contrast ratio is a measure of a display system defined as the ratio of the luminance of the brightest white to that of the darkest black that the projector is capable of. DLP projectors do provide high contrast specifications compared to a majority of LCD projectors. At first glance, this can seem to be a benefit, however, in the real world, the true black level is determined by the ambient light in the room in which the projector is in use. Do not be fooled by contrast specifications on websites and in brochures.

When the content you plan to view needs moving images, DLP projection technology also has image marks, or ‘artifacts’. The most commonplace artifact that a DLP projector displays with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images change up between the time red, blue and green colours are displayed. LCD projectors do not have this downside because all colours are projected at the same time. DLP designers have come up with 3DLP solutions using 3 chips to resolve the colour break up artifacts, but the price of these projectors make them impractical for most businesses and consumers.

Another differentiation between LCD and DLP is how they balance for the refractive qualities of light. Take yourself back to high school science, and remember when they taught you how the different colours of light refract various amounts when projected through the same lens. The disadvantage with DLP projectors is that they have the one same panel for the same lens to project Red, Blue and Green. All 3 colours are obviously not the same and refract light at different levels. Generally with a DLP projector, a superfluous yellow colour will come up above and a spill of blue will come up below an image containing something as simple as a straight black line. In building LCD projectors can be adjusted to minimize these effects on the projected image, because each colour is refracted on separate LCD panels.

The one veritable buy point (excluding price) with choosing a DLP projector is its smaller overall size and weight. However, this is only relevant in regard to transporting the device and must be traded off against the image advantages of LCD projectors. If overall picture quality is vital to you, then the choice is easy. Choose an LCD projector! LCD projectors will always create bright, colourful images with fewer image imperfections. If you want to learn more about LCD technology in more detail, have a gander at this fantastic resource website: Explore 3LCD. If you have any further questions, get onto Projector Central and send me an email.

Jonathan King is the sales and marketing manager of Projector Central, Australia’s number one online retailer for projectors. Based in Brisbane, Projector Central has been serving Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.

Sphere: Related Content

Categories: General Travel Information | Tags: , | No Comments