Projectors: LCD Verses DLP (The downfall of DLP technology)
The common question heard when purchasing a new projector for the home, office, or classroom is: would I get an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two most common projector imaging technologies. With so many brands and different models available, it can be challenging for the buyer to choose between both technologies. Ultimately LCD projectors offer far superior image quality and colour accuracy. The next paragraph explains why DLP projectors struggle with reproducing the same level of image quality.
Think of a set of blinds in your room over your bedroom window. By a twist of a rod you can turn the shutters open or closed, according to if you want to let light in or not. And that is exactly how an LCD projector works. Each pixel functions like an individual shutter on a set of blinds to either send light through or to block it. DLP on the other hand is made up of millions of microscopic mirrors or ‘pixel elements’ as experts like to call them. Each pixel element operates to either reflect light or block it.
How the light source is processed from the time the projector switches on to when the picture reaches your screen is extremely important in regard to image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by dividing it into red, blue and green components, by three mirrors which direct the coloured light to 3 different LCD panels. The 3 LCD panels create the elements of the image by switching each pixel on and off. The pixels are then simultaneously processed in a glass prism to send the projector image. An important point to understad about LCD projectors is that all three colours are sent onto your wall simultaneously. The way a DLP projector operates is vastly different and even the produced image comes out is not the same. With DLP, white light from the lamp is directed through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of forming an image requires a sequence of red, blue and green light. The millions of micro mirrors as mentioned above reflect the coloured light on the pixels to construct the image elements. The elements of the image are projected in sequence on the screen, one colour at a time. The viewer’s eye will then combine each coloured element of the image into a single whole image. Using LCD projectors, all colours are available all the time to create the highest brightness and superb colour accuracy. In DLP, just one colour is available at once, causing lower colour brightness and accuracy. Some DLP developers have added a white segment for the colour wheel to improve general brightness, but this also damages colour accuracy.
I hear in forums all the time that DLP gives a higher contrast ratio and therefore must be better quality. For those 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 producing. DLP projectors do possess high contrast specifications in comparison to the majority of LCD projectors. At one glance, this appears to be a plus, however, in reality, the true black level is determined by the ambient light in the room where the projector is in use. Do not be fooled by contrast specifications on websites and in brochures.
When the content you wish to project requires moving images, DLP projection technology can also create image errors, or ‘artifacts’. The most common artifact that a DLP projector shows with moving images is colour break up. Colour break up is to be expected 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 all the colours are processed simultaneously. DLP builders have created 3DLP solutions using 3 chips to solve the colour break up error, but the expense of these projectors make them impractical for the majority of businesses and consumers.
Another difference between LCD and DLP is how they balance for the refractive qualities of light. Jump back to high school science, and remember when they taught you how different colours of light refract differing amounts when shone through the same lens. The downside with DLP projectors is that they utilise 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. Most of the time with a DLP projector, a spill of yellow colour will come through above and a superfluous blue will be projected below something as simple as a lone black line. In building LCD projectors can be adjusted to minimize these effects on the projected image, because each colour is refracted on its own LCD panels.
The one veritable plus (excluding price) with going with a DLP projector is its smaller size and weight. However, this is only relevant in regard to transporting the device and has to be traded off against the image superiority of LCD projectors. If overall picture quality is crucial to you, then the answer is easy. Choose an LCD projector! LCD projectors will consistently make bright, colourful images with fewer image mistakes. If you need to find out more about LCD technology in more detail, see this fantastic resource website: Explore 3LCD. If you have any additional questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager for Projector Central, Australia’s top online store for projectors. Brisbane based, Projector Central has served Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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