Projectors: LCD Verses DLP (The downfall of DLP technology)
July 19th, 2010
The typical question heard when buying a new projector for the home, office, or classroom is: should I get an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two top projector imaging technologies. With so many company brands and models available, it can be difficult for customers to choose between the two technologies. Ultimately LCD projectors give better image quality and colour accuracy. The article below will tell you why DLP projectors struggle with creating a similar rate of image quality.
It’s like a set of blinds in your house over your bedroom window. By pulling on a rod you can have the shutters open or closed, according to whether you want to let light in or not. And this is exactly how an LCD projector functions. Each pixel operates like a unique shutter on a set of blinds to either allow light through or to block it. DLP on the other hand is created of millions of microscopic mirrors or ‘pixel elements’ as the experts like to call them. Each pixel element functions to either reflect light or block it.
How the light source is processed from when the projector is switched on to when the picture reaches your screen is absolutely important to image quality, brightness and colour accuracy. LCD projectors shine white light from the lamp by splitting it into red, blue and green components, by three mirrors which send the coloured light to 3 separate LCD panels. The 3 LCD panels cast the elements of the image by processing each pixel on and off. The pixels are then simultaneously processed in a glass prism to form the projector image. A significant point to understad about LCD projectors is that all three colours are projected onto your wall all at once. The way a DLP projector works is totally different and even the final product of how an image comes out is not the same. With DLP, white light from the lamp is projected through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of making an image creates a sequence of red, blue and green light. The millions of micro mirrors as described above reflect the coloured light on the pixels to form the image elements. The elements of the image are cast 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 a total image. From LCD projectors, all colours are available all the time to deliver top brightness and great colour accuracy. In DLP, only one colour is available at a time, resulting in lower colour brightness and accuracy. Some manufacturers have added a white segment in the colour wheel to improve general brightness, but this also lessens colour accuracy.
I read in forums all the time that DLP offers a higher contrast ratio and thus must be better quality. For those who are unaware, 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 capable of producing. DLP projectors do provide high contrast specifications in comparison to most LCD projectors. At a glance, this seems to be a plus, however, in truth, the true black level is determined by the ambient light in the room where the projector is in use. Do not be hoodwinked by contrast specifications on websites and in brochures.
When the content you are trying to bring to life has moving images, DLP projection technology can also create image imperfections, or ‘artifacts’. The most commonplace artifact that a DLP projector creates with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images change position between the time red, blue and green colours are projected. LCD projectors do not have this problem because all colours are delivered simultaneously. DLP builders have created 3DLP solutions using 3 chips to answer the colour break up artifacts, but the expense of these projectors make them not practical for the large part of businesses and consumers.
Another point of difference between LCD and DLP is how they make up for the refractive qualities of light. Take yourself back to high school science, and they taught you how the various colours of light refract various amounts when directed through the same lens. The downfall 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 different and refract light at different levels. Often with a DLP projector, some extra yellow colour will show above and a spill of blue will appear below an image containing something as simple as a single black line. In manufacturing LCD projectors can be fixed to take away these effects on the projected image, because each colour is refracted on its own LCD panels.
The one real advantage (excluding price) with going with a DLP projector is its smaller size and weight. However, this is only relevant to transport and has to be traded off against the image plusses of LCD projectors. If the result of the picture quality is crucial to you, then the answer is a no-brainer. Go for an LCD projector! LCD projectors will definitely produce bright, colourful images with fewer image errors. If you desire to learn more about LCD technology in more detail, have a gander at this tremendous resource website: Explore 3LCD. If you have any more questions, get onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager of Projector Central, Australia’s premier online retailer for projectors. Brisbane based, Projector Central has been serving Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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