Projectors: LCD Verses DLP (The downfall of DLP technology)
The common question customers ask when acquiring a new projector for the home, office, or classroom is: should I take an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two top projector imaging technologies. With so many business brands and different models available, it can be difficult for clients to choose between both technologies. The fact is that LCD projectors provide far superior image quality and colour accuracy. The article below will tell you why DLP projectors struggle with projecting a similar standard of image quality.
Visualise a set of blinds in your house on your bedroom window. By pulling on a rod you can have the shutters open or closed, depending on whether you want to let light in or not. And that is exactly how an LCD projector functions. Each pixel operates like a single 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 professionals 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 turned on to when the picture reaches your screen is vitally important for image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by cutting 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 turning each pixel on and off. The pixels are then meshed in a glass prism to deliver the projector image. An important point to realise about LCD projectors is that all three colours are projected onto your projector screen all at the same time. The way a DLP projector runs is vastly different and even the final product of how an 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 way of forming an image creates a sequence of red, blue and green light. The millions of micro mirrors described above reflect the coloured light on the pixels to produce the image elements. The elements of the image are cast in sequence on the screen, one colour at a time. The viewer’s eye will then draw each coloured element of the image into a whole image. In LCD projectors, all colours are available all the time to create the highest brightness and great colour accuracy. In DLP, just one colour is available at a time, causing lower colour brightness and accuracy. Some DLP developers have included a white segment for the colour wheel to improve all over brightness, but this further degrades colour accuracy.
I find in forums all the time that DLP has a higher contrast ratio and thus must be better quality. For those 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 able to produce. DLP projectors do offer high contrast specifications in comparison to the majority of LCD projectors. At first glance, this must be a plus, however, in real life, the true black level is determined by the ambient light in the room where the projector is used. Do not be hoodwinked by contrast specifications on websites and in brochures.
When the content you wish to bring to life requires moving images, DLP projection technology also has image errors, or ‘artifacts’. The most typical 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 between the time red, blue and green colours are shone. LCD projectors do not have this characteristic because all colours are processed at once. DLP designers have developed 3DLP solutions using 3 chips to answer the colour break up artifacts, but the expense of these projectors make them impractical for many businesses and consumers.
Another differentiation between LCD and DLP is how they match the balance for the refractive qualities of light. Think back to high school science, and remember how various colours of light refract different amounts when passing through the same lens. The disadvantage with DLP projectors is that they utilise the one same panel and the same lens to project Red, Blue and Green. All 3 colours are different and refract light in different ways. Usually with a DLP projector, some yellow colour will appear above and some blue will appear below an image of something as simple as a lone black line. During manufacturing LCD projectors can be adjusted to minimize these effects on the projected image, because each colour is processed on a separate LCD panels.
The one veritable plus (excluding price) with going with a DLP projector is its overall smaller size and weight. However, this is only relevant in regard to transport and must be traded off against the image advantages of LCD projectors. If the outcome of the picture quality is crucial to you, then the choice is easy. Go with an LCD projector! LCD projectors will consistently create bright, colourful images with fewer image errors. If you want to learn more about LCD technology in more detail, see this fabulous 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 at Projector Central, Australia’s top 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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