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

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

It’s like a set of blinds in your house on your bedroom window. By pulling on a rod you can turn the shutters open or closed, according to if you want to let light in or not. And this is exactly how an LCD projector behaves. Each pixel functions like its own shutter on a set of blinds to either shine light through or to block it. DLP on the other hand is made up of millions of microscopic mirrors or ‘pixel elements’ as the experts like to call them. Each pixel element works to either reflect light or block it.

How the light source is processed from the time the projector turns on to when the picture reaches your screen is vitally significant with regard to image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by separating it into red, blue and green components, by three mirrors which direct the coloured light to 3 separate LCD panels. The 3 LCD panels form the elements of the image by switching each pixel on and off. The pixels are then meshed in a glass prism to send the projector image. Something important to remember about LCD projectors is that all three colours are directed onto your screen at the same time. The way a DLP projector operates is vastly different and even the way an image comes out 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 approach to making an image forms a sequence of red, blue and green light. The millions of micro mirrors mentioned above reflect the coloured light on the pixels to construct the image elements. The elements of the image are cast in sequence on the screen, one colour at a time. The viewer’s eyes will then draw each coloured element of the image into a single full image. Using LCD projectors, all colours are available all the time to offer the top level of brightness and great colour accuracy. In DLP, only one colour is available at any given time, resulting in lower colour brightness and accuracy. Some designers have included a white segment into the colour wheel to improve brightness generally, but this also detracts from colour accuracy.

I find in forums all the time that DLP has a higher contrast ratio and therefore must be superior. 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 machine is able to produce. DLP projectors do provide high contrast specifications as compared to a majority of LCD projectors. Initially, this seems to be a plus, however, in reality, the true black level is determined by the ambient light in the room while the projector is being used. Do not be hoodwinked by contrast specifications on websites and in brochures.

When the content you are trying to view requires moving images, DLP projection technology also has image marks, or ‘artifacts’. The most common artifact that a DLP projector shows with moving images is colour break up. Colour break up is inherent in DLP systems because moving images keep changing between the time red, blue and green colours are pulled up. LCD projectors do not have this disadvantage because the colours are sent at the same time. DLP designers have developed 3DLP solutions using 3 chips to answer the colour break up problem, but the price of these projectors make them almost impossible for most businesses and consumers.

Another variance between LCD and DLP is how they balance for the refractive qualities of light. Jump back to high school science, and recall how the different colours of light refract various amounts when passing through the same lens. The downside with DLP projectors is that they use the one same panel and the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light in different ways. Most of the time with a DLP projector, a spill of yellow colour will come up above and some extra blue will be projected below an image of something as simple as a straight black line. In manufacturing LCD projectors can be set to take away these effects on the projected image, because each colour is projected on its own LCD panels.

The sole true benefit (excluding price) with going with a DLP projector is its smaller overall size and weight. However, this is only relevant in regard to portability and cannot be traded off against the image plusses of LCD projectors. If overall picture quality is important to you, then the solution is no-brainer. Go with an LCD projector! LCD projectors will always create bright, colourful images with fewer image errors. If you need to find out more about LCD technology in more detail, check out this fabulous resource website: Explore 3LCD. If you have any additional questions, go to Projector Central and send me an email.

Jonathan King is the sales and marketing manager at Projector Central, Australia’s leading online retailer for projectors. Brisbane based, Projector Central has been serving Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.