Projectors: LCD Verses DLP (The downfall of DLP technology)
The typical question heard when buying a new projector for the home, office, or classroom is: would I get an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two most common projector imaging technologies. With so many different brands and different models available, it can be overwhelming for the buyer to decide between both technologies. It comes down to the fact that LCD projectors provide better image quality and colour accuracy. The following article will tell you why DLP projectors struggle with projecting the same level of image quality.
Think of a set of blinds in your home on your bedroom window. By twisting a rod you can make 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 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 constructed 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 when the projector is switched on to when the content reaches your screen is vitally significant in regard to image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by splitting it into red, blue and green components, by three mirrors which direct the coloured light to 3 stand alone LCD panels. The 3 LCD panels make the elements of the image by turning each pixel on and off. The pixels are then meshed in a glass prism to send the projector image. A significant point to realise about LCD projectors is that all three colours are directed onto your projected surface at the same time. The way a DLP projector functions is vastly different and even how an image comes out is not the same. With DLP, white light from the lamp is directed through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of forming an image requires a sequence of red, blue and green light. The millions of micro mirrors mentioned above reflect the coloured light on the pixels to produce the image elements. The elements of the image are projected in sequence on the screen, one colour at a time. The viewer’s eyes will then pull together each coloured element of the image into the complete image. Using LCD projectors, all colours are available all the time to form the top level of brightness and spectacular colour accuracy. In DLP, just one colour is available at any given time, and so resulting in lower colour brightness and accuracy. Some DLP manufacturers have included a white segment for the colour wheel to improve all over brightness, but this also detracts from colour accuracy.
I find in forums all the time that DLP provides a higher contrast ratio and thus must be better. For those who are unsure, 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 system is capable of producing. DLP projectors do have high contrast specifications when compared to a majority of LCD projectors. At a glance, this must be a plus, however, in the real world, the true black level is determined by the ambient light in the room in which the projector is utilised. Do not be duped by contrast specifications on websites and in brochures.
When the content you plan to project has moving images, DLP projection technology also creates image marks, or ‘artifacts’. The most often seen artifact that a DLP projector displays with moving images is colour break up. Colour break up is inherent in DLP systems because moving images change up between the time red, blue and green colours are pulled up. LCD projectors do not have this problem because all colours are processed at once. DLP designers have developed 3DLP solutions using 3 chips to fix the colour break up artifacts, but the price tag of these projectors make them impractical for the majority of businesses and consumers.
Another point of difference between LCD and DLP is how they match the balance for the refractive qualities of light. Jump back to high school science, and they taught you how the different colours of light refract varied amounts when projected through the same lens. The downside with DLP projectors is that they take the one same panel and the same lens to project Red, Blue and Green. All 3 colours are not the same and refract light at different levels. Most of the time with a DLP projector, some yellow colour will appear above and some extra blue will show below an image as simple as a lone black line. In manufacturing LCD projectors can be fixed to minimize these effects on the projected image, because each colour is projected on its own LCD panels.
The one real plus (excluding price) with choosing a DLP projector is its smaller overall size and weight. However, this is only relevant in regard to transport and needs to be traded off against the image plusses of LCD projectors. If the outcome of the picture quality is important to you, then the answer is a no-brainer. Take an LCD projector! LCD projectors will definitely show bright, colourful images with fewer image errors. If you desire to learn more about LCD technology in more detail, have a gander at this fabulous resource website: Explore 3LCD. If you have any other questions, visit Projector Central and send me an email.
Jonathan King is the sales and marketing manager for Projector Central, Australia’s leading online store for projectors. Based in Brisbane, 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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