Projectors: LCD Verses DLP (The downfall of DLP technology)
The common question heard when acquiring a new projector for the home, office, or classroom is: would I buy an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many business brands and types available, it can be confusing for the buyer to pick between the two technologies. The simple fact of the matter is that LCD projectors offer better image quality and colour accuracy. The following article explains why DLP projectors struggle with bringing up a comparable level of image quality.
Imagine a set of blinds in your house on your bedroom window. By a twist of a rod you can make the shutters open or closed, according to if you want to let light in or not. And that is exactly how an LCD projector operates. Each pixel works like a unique shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is constructed of millions of microscopic mirrors or ‘pixel elements’ as professionals like to call them. Each pixel element works to either reflect light or block it.
How the light source is processed from when the projector is turned on to when the image reaches your screen is extremely important with regard to 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 individual LCD panels. The 3 LCD panels create the elements of the image by turning each pixel on and off. The pixels are then projected in a glass prism to form the projector image. Something important to realise about LCD projectors is that all three colours are sent onto your screen all at the same time. The way a DLP projector runs is vastly different and even the way an image shows up is not the same. With DLP, white light from the lamp is processed through a spinning 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 described above reflect the coloured light on the pixels to create 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 put together each coloured element of the image into the single complete image. With LCD projectors, all colours are available all the time to create the top level of brightness and spectacular colour accuracy. In DLP, only one colour is available at once, and so causing lower colour brightness and accuracy. Some designers have put a white segment into the colour wheel to improve brightness overall, but this also detracts from colour accuracy.
I find in forums all the time that DLP provides a higher contrast ratio and therefore must be better. 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 technology is able to produce. DLP projectors do offer high contrast specifications in comparison to a majority of LCD projectors. At one glance, this must be an advantage, however, in reality, the true black level is determined by the ambient light in the room when the projector is used. Do not be duped by contrast specifications on websites and in brochures.
When the content you wish to view includes moving images, DLP projection technology also has image errors, or ‘artifacts’. The most commonplace artifact that a DLP projector forms with moving images is colour break up. Colour break up is unavoidable 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 the colours are processed at once. DLP developers have created 3DLP solutions using 3 chips to fix the colour break up error, but the price tag of these projectors make them almost impossible for most businesses and consumers.
Another variance between LCD and DLP is how they match the balance for the refractive qualities of light. Take yourself back to high school science, and recall how the different colours of light refract different amounts when shone through the same lens. The downside with DLP projectors is that they take 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 in different ways. Usually with a DLP projector, a superfluous yellow colour will appear above and a superfluous blue will show below an image containing something as simple as a single black line. In building LCD projectors can be adapted to take away these effects on the projected image, because each colour is directed on separate LCD panels.
The only true buy point (excluding price) with buying a DLP projector is its overall smaller size and weight. However, this is only relevant in regard to portability and needs to be traded off against the image advantages of LCD projectors. If resulting picture quality is vital to you, then the answer is simple. Go for an LCD projector! LCD projectors will definitely produce bright, colourful images with fewer image blips. If you need to ask more about LCD technology in more detail, have a gander at this tremendous resource website: Explore 3LCD. If you have any persisting questions, get onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s premier online shop for projectors. Based in Brisbane, Projector Central has been serving Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.
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